GIFT  OF 


V-    NC\ 


(U*. , 


MANUAL 


OF 


CHEMICAL    TECHNOLOGY 


BY 


RUDOLF  VON  WAGNER 


MANUAL 


OP 


CHEMICAL  TECHNOLOGY 


BY 


RUDOLF  VON   WAGNER 

II 


TRANSLATED    AND    EDITED    BY 

SIR  WILLIAM  CROOKES,  F.R.S. 

PAST  PRES.  C.S.,  PRES.  INST.  E.E. 

FROM  THE  THIRTEENTH  ENLARGED  GERMAN  EDITION  AS  REMODELLED  BY 

DE    FERDINAND    FISCHER 

WITH   596   ILLUSTRATIONS 
REPRINTED  1897 


NEW    YORK 
D.    APPLETON    &    CO. 

1,  3  &  5  BOND   STREET 
1897 


T  P/  fs- 


PREFACE  TO  THE  THIRTEENTH  GERMAN  EDITION. 


IN  the  twelfth  edition  of  this  Manual,  which  appeared  in  1886,  I  confined 
myself  to  abridging  or  totally  removing  jhe  obsolete  matter  in  the  eleventh 
edition,  which  had  been  completed  by  Wagner  shortly  before  his  death, 
October  4,  1880,  and  to  inserting,  or  at  least  referring  to,  the  improvements 
effected  in  the  last  few  years. 

In  the  present  edition  the  former  arrangement  of  the  subject-matter  was 
rejected,  as  it  seems  inadmissible  to  speak  of  nitric  acid,  explosives,  and  soda 
before  sulphuric  acid  ;  to  separate  cotton  from  wool,  whilst  placing  in  juxta- 
position leather,  lucifer  matches,  and  milk. 

Technology  (T^VJ?,  Aoyoc) — the  doctrine  of  the  industries  which  improve 
materials — is  divided,  for  more  ready  comprehension,  into  Mechanical  Technology, 
which  teaches  us  to  modify  the  form  of  the  crude  material,  and  Chemical 
Technology,  the  task  of  which  is  to  alter  the  nature  or  the  composition  of  the 
materials.  A  strict  separation  of  both  parts  of  Technology  is  impracticable, 
since  Chemical  Technology  very  often  requires  the  help  of  mechanical  arrange- 
ments, especially  in  metallurgy,  in  the  production  and  elaboration  of  glass, 
earthenware,  cements,  and  paper,  in  tissue-printing,  &c.  But  in  the  arrangement 
of  the  subject-matter  in  Mechanical  Technology  the  manner  in  which  the  form 
of  bodies  is  modified  is  exclusively  prominent,  whilst  in  Chemical  Technology  the 
chemical  change  of  the  material  is  the  dominant  point  of  view.  The  Mechanical 
Technologist  treats,  e.g.,  the  cutting  of  iron,  wood,  leather,  and  bread  as  if 
in  connection ;  he  presupposes  the  necessary  knowledge  of  the  material.  The 
Chemical  Technologist  must  pursue  the  material  in  its  various  changes,  pre- 
supposing the  mechanical  auxiliaries  which  may  be  needed  (e.g.,  the  various 
machines  for  comminution),  or  they  must  be  treated  in  such  a  manner  as  not  to 
interfere  with  the  survey  of  the  chemical  process. 

452047 


<ri  PREFACE   TO  THE   THIRTEENTH   GERMAN   EDITION. 

In  every  department  of  Technology  fuel  is  indispensable,  and  it  is  therefore 
discussed  in  the  first  place. 

If  we  consider  that  Germany  alone  consumes  every  minute  almost  a 
milliard  of  calories  of  the  heat  (or  of  energy)  stored  up  in  the  state  of  fossil 
fuel,  we  are  justified,  whilst  no  substitute  can  be  thought  of,  in  demanding 
that  more  attention  shall  be  paid  to  fuel  than  has  been  hitherto  the  case. 

In  Section  II.  the  subdivisions  on  Potassium  and  Sodium,  in  III.  those 
on  Water,  Manures,  and  Thermo -chemistry,  are  entirely  novel ;  Section  I.  is 
chiefly,  and  Section  IV.  entirely,  new.  As  compared  with  the  eleventh  edition, 
in  that  now  submitted  to  the  reader  more  than  half  the  text  and  also  the  illus- 
trations will  be  found  new.  It  is  hoped  that  this  new  edition  will  meet  with 
as  favourable  a  reception  as  its  predecessors. 

F.  FISCHER. 

HAKOVEE,  December  1888 


PREFACE  TO   THE   ENGLISH   EDITION. 


THE  present  English  version  differs  so  widely  from  that  which  appeared  in 
May  1872,  that  it  may  be  regarded  as  substantially  a  new  work.  It  is 
founded  on  the  thirteenth  German  edition  of  1888,  brought  out  by  Dr. 
Ferdinand  Fischer,  and  re-modelled  in  accordance  with  the  many  important 
changes  which  have  been  recently  effected  in  chemical  industry.  To  these 
reference  has  already  been  made  in  Dr.  Fischer's  Preface. 

But  further  modifications  have  been  found  necessary.  A  treatise  on  pure 
chemistry  is  of  equal  value  the  world  over.  But  a  Manual  like  the  present 
must  be  in  many  respects  adapted  to  the  conditions  of  the  country  where  it  is 
written,  and,  if  translated  for  use  elsewhere,  it  requires  modification.  The  prices 
of  raw  materials,  of  fuel,  and  of  labour  have  to  be  kept  in  view.  The  laws 
of  different  countries  interfere  with  industrial  processes  in  different  manners 
and  to  a  very  different  extent.  Hence  certain  passages  have  been  omitted  as 
inapplicable  to  conditions  prevailing  in  Britain,  and  many  notes  have  been 
added,  for  which  the  Editor  considers  himself  solely  responsible. 

Bibliographical  references  to  works  easily  accessible  to  the  English  reader 
are  added  either  in  the  form  of  notes  or  in  the  text,  the  latter  chiefly  under 
Silver  (pp.  187  and  188)  and  Gold  (pp.  189,  190,  and  191). 

Concerning  the  illustrations,  it  may  be  necessary  to  add  that  many  of  the 
blocks,  instead  of  being  lettered  for  reference  with  plain  printing  characters, 
are  marked  in  script,  and  in  some  cases  German  words  form  part  of  the 
figures.  It  has  therefore  been  necessary  to  add  to  each  such  cut  an  "  Explana- 
tion of  Terms/'  which  the  Editor  hopes  will  render  it  perfectly  intelligible  to 
the  reader. 

Temperatures   are   almost   entirely  expressed  on   the  Centigrade    scale,  the 


viii  PREFACE  TO  THE   ENGLISH   EDITION. 

freezing-point  or  zero  =  o,  and  the  boiling-point  of  water  =  100.  Where 
other  scales  are  used,  such  as  Fahrenheit,  they  are  specially  mentioned. 

Weights  and  measures  are  given  according  to  the  metric  system. 

Specific  gravities  of  liquids  heavier  than  water  are  generally  given  on 
TwaddelPs  hydroinetric  scale.  This  scale  has  the  double  advantage  over  that 
of  Baume",  in  that  it  does  not  exist  in  two  or  more  modifications,  and  that  it  can 
be  converted  into  direct  specific  gravity  by  a  very  simple  calculation,  for  which 
the  reader  is  referred  to  the  tables  at  the  end  of  the  book. 

WILLIAM   CKOOKES. 

LONDON,  December  1891. 


TABLE  OF  CONTENTS. 

SECTION  I. 
TECHNOLOGY  OF  FUEL. 

PAG* 

FUEL  AND  ITS  TREATMENT .      I 

THERMOMETRY 2 

History,  2 ;  conspectus  of  ordinary  thermometers,  2  ;  mercurial  thermometers,  2 ;  naph- 
thaline and  benzophenone  thermometers,  3  ;  determination  of  boiling-point,  3  ;  determina- 
tion of  high  temperatures,  4  ;  electric  thermometers,  5  ;  diffusion  of  heat,  5. 

DETERMINATION  OP  THE  VALUE  OF  FUELS 6 

Sampling,  6  ;  determination  of  ash,  7  ;  the  yield  of  coke,  7 ;  determining  the  nitrogen  by 
Kjeldahl's  process,  7  ;  determining  the  carbon  and  hydrogen,  7  ;  determining  the  volatile 
sulphur,  8  ;  wood,  n  ;  air-dried  wood,  n  ;  degasified  wood,  12. 

MANUFACTURE  OF  WOOD  CHARCOAL 12 

Kiln,  12  ;  Italian  kiln,  13  ;  Slavonian  kiln,  13  ;  Schwarten  kiln,  13  ;  sweating,  full  com- 
bustion, slow  smouldering,  13 ;  carbonisation  in  South  Germany,  Russia,  and  Sweden, 
13;  charcoal  ovens,  14;  simplest  kilns,  14;  charring  wood  in  retorts,  15;  wood-tar  in 
Russia,  15;  in  Lower  Austria,  15;  in  Bohemia,  15;  Swedish  "  thermo-kettles,"  16 ;  yield 
of  crude  acid  tar  and  charcoal  with  different  kinds  of  wood,  17. 

PEAT  .        .        . 18 

Varying  nature,  18;  extraction,  18 ;  percentages  of  water,  18;  composition,  18 ;  uses  of 
peat,  19. 

LIGNITE  (BROWN  COAL,  BOVEY  COAL) .19 

Experiments  of  Schinnerer  and  Morawski,  A.  Bartoli  and  G.  Papasogli,  19  ;  degree  of  com- 
position to  distinguish  appearance  of  wood,  19 ;  pitch-coal,  19 ;  jet,  19 ;  Cologne  umber, 
20  ;  production  of  solar  oil  and  paraffine,  20  ;  average  composition  of  lignites,  20 ;  moisture, 
20  ;  applicability,  20 ;  drying,  20 ;  modes  of  treatment — fire-plate  ovens,  20 ;  steam- 
oven,  21  ;  tube  drying  oven  of  Schulz,  21  ;  hot-air  oven,  22;  desiccation  by  means  of  steam 
and  hot  air,  22;  fault  of  all  systems,  22;  "press-coal,"  22;  collecting  space,  23;  limit  of 
compression,  23. 

COAL 23 

Composition,  23  ;  important  localities  in — the  United  Kingdom,  23  ;  Europe,  24  ;  America, 
24  ;  British  North  America,  24 ;  South  Africa,  24 ;  India,  24  ;  China,  24  ;  Japan,  24  ;  Aus- 
tralia, 24  ;  researches  of  M.  A.  Carnot,  24  ;  of  Scheurer-Kestner,  24  ;  quality  of  coal,  24 ; 
combustion  value,  24  ;  Schwackhofer's  experiments,  24  ;  anthracite,  25  ;  where  found,  25  ; 
analysis,  25  ;  use,  25  ;  Boghead  coal,  25  ;  where  found,  25  ;  composition,  25  ;  Dr.  Stenhouse's 
analysis,  25  ;  analysis  of  ash,  25  ;  used  as  fuel  in  gas  manufacture,  &c. ,  25  ;  Hilt's  classifi- 
cation of  coals,  26  ;  L.  Gruner  on  technical  value  of  a  coal,  26  ;  E.  Jensch's  analysis,  26. 

COKE 26 

Object  of  making,  26  ;  oven-coking,  27  ;  closed  coke-ovens,  27  ;  coking  of  small  coal,  27  ; 
coke-oven  used  on  the  Saar,  &c.,  28 ;  coke-oven  of  Appolt  Bros.,  28  ;  combination  of  coke- 
ovens  with  the  Siemens  heat  reservoirs  by  G.  Hoffmann,  30  ;  coke-ovens  at  the  Pluto  Mine, 
32  ;  briquettes,  block-coal,  35  ;  moulded  charcoal,  35  ;  coal  blocks,  &c.,  35. 

b 


x  TABLE   OF   CONTENTS. 

PAGI 

DEGASIFYING,  GASIFYING,  COMBUSTION 35 

Application  of  the  fuels,  35  ;  degasifying,  36  ;  products  of  degasification  of  coal,  36 ;  of 
•wood,  36 ;  time  required,  38 ;  H.  Bunte's  experiment,  39 ;  Berthelot's  researches,  39 ; 
analyses  of  purified  gas,  39  ;  combustion  value  of  the  components  of  coal-gas,  39 ;  bye- 
products,  40 ;  generator-gas,  41  ;  coke-generators,  41  ;  gas-fires,  41  ;  gas-firing,  42  ;  F. 
Siemens'  generator,  42  ;  gasification  of  carbon,  43  ;  introduction  of  watery  vapour,  44  ; 
water-gas,  45  ;  method  of  making,  45  ;  arrangements  at  Essen  and  Witkowitz,  46  ;  gener- 
ator-gas made  at  Essen,  47  ;  determinations  of  carbonic  acid,  48  ;  cost  of  lighting  by 
water-gas,  48  ;  applications  in  metallurgical  operations,  49. 

HEATING  ARRANGEMENTS 50 

Materials  used,  50  ;  method  of  combustion,  50  ;  gas  analysis,  50  ;  W.  Apel's  apparatus,  50  ; 
mode  of  use,  52  ;  method  of  determining  hydrogen  and  methan,  53  ;  the  analysis,  53  ; 
lubricator  for  the  cocks,  55  ;  calculating  various  readings,  55  ;  to  preserve  samples  of  gas, 
56  ;  loss  of  heat,  57  ;  weight  of  sulphurous  or  sulphuric  acid,  &c.,  57  ;  best  apparatus  for 
steam-boiler  furnaces,  &c.,  58  ;  steam-boiler  firing,  58  ;  size  of  grate,  58  ;  control,  59 ; 
heating  experiments,  59  ;  regulations  for  deciding  on  the  duty  of  a  steam  boiler,  59 ; 
evaporation  and  distribution  of  heat,  60;  shape  of  grate,  60;  smoke  consumption,  61  ; 
house  heating,  61  ;  object,  61  ;  forms,  61  ;  open  fires,  61  ;  stove  heating,  61  ;  results,  62  ; 
stoves  in  Germany,  62  ;  Russian  stoves,  62  ;  experiments  with  a  tile  stove,  63  ;  hot-air 
heating,  63  ;  air  entrance,  64 ;  air-filter,  64  ;  consumption  of  fuel,  65  ;  water  heating,  65  ; 
steam  heating,  65  ;  best  means  of  heating,  65  ;  heating  with  coal  gas,  65  ;  expense,  65  ; 
gas-firing,  66  ;  air  entrance,  66  ;  system  for  lignite,  66  ;  burners,  66  ;  generator,  66  ;  C.  W. 
Siemens'  method,  66  ;  Munich  generator  furnace  of  N.  H.  Schilling,  68  ;  composition  of 
generator  gases,  70  ;  uses  of  gas-firing,  71. 

LIGHTING-GAS 71 

History,  71  ;  production,  72  ;  Stedman's  retort  furnace,  73  ;  furnaces  of  Liegel  and  Klonne, 
Hasse  and  Didier,  73  ;  tar-firing,  73  ;  reduced  value  of  tar,  73  ;  Korting's  pulveriser,  73  ; 
experiments  with  various  kinds  of  coal,  74  ;  purification  of  the  gas,  75  ;  the  condenser,  75 ; 
scrubber,  75;  purifiers,  76;  purifying  with  oxide  of  iron,  76;  "Laming's  mass,"  76; 
ammoniacal  purifying,  76  ;  Glaus'  method,  76  ;  F.  C.  Hill's  modification,  77  ;  examination, 
78 ;  amount  of  sulphur,  78  ;  ammonia,  78  ;  complete  analysis  of  gas,  78  ;  wood-gas,  79  ; 
Lebon's  "  thermo-lamp,"  79  ;  resin-gas,  79  ;  peat-gas,  79  ;  oil-gas,  80;  apparatus  used,  80; 
air-gas,  80. 

MINERAL  OIL 80 

Ancient  use  of,  80  ;  natural  oil  wells,  81  ;  origin,  81  ;  how  obtained,  81  ;  relative  quantities 
from  different  places,  82  ;  Bradford  oil,  82  ;  natural  gas,  82  ;  where  found,  82  ;  composition, 
82  ;  manufacture,  84  ;  upright  wrought-iron  boilers,  84  ;  waggon  boiler,  84  ;  roller  boiler, 
85  ;  fuel  substitutes,  85  ;  products  of  distillation,  86 ;  cost  of  production,  86  ;  uses  of 
residues,  86. 

PABAFFINE  AND  SOLAR  OIL  INDUSTRY •     .    87 

Paraffine — when  and  how  first  obtained,  87  ;  how  now  obtained,  87  ;  manufacture,  87  ; 
preparation  of  the  tar,  87  ;  arrangement  of  retorts,  87  ;  condensation  of  the  vapours  of  the 
tar,  88  ;  properties  of  tar,  89  ;  quantity  obtained,  89  ;  mode  of  operating  with  the  tar,  89 ; 
distillation  of  the  tar,  90  ;  treatment  of  the  products  of  distillation,  90  ;  rectification  of  the 
crude  oils,  91  ;  refining  the  crude  paraffine,  91  ;  Hubner's  method  of  preparing  paraffine, 
92  ;  yield  of  paraffine,  92  ;  brown  coal,  92  ;  steam-tar,  93  ;  purified  paraffine,  93  ;  applica- 
tion, 93  ;  solar  oil,  94  ;  "  vulcanol,''  94. 

PRODUCTION  OF  LIGHT 94 

Treatment  of  solids,  94. 

PHOTOMETEY 95 

Measuring  the  luminosity  of  a  flame,  95  ;  Bunsen's  photometer,  95  ;  various  photometric 
candles,  95  ;  German,  95  ;  Munich,  96  ;  English,  96  ;  carcel  lamp,  96  ;  Von  Hefner- Alteneck's 
proposed  unit  of  light,  96  ;  international  conference  unit,  97  ;  Violle's  method  of  producing 
this  unit,  97  ;  apparatus  for  comparing  platinum  unit  with  carcel  lamp,  97. 

LIGHTING  WITH  CANDLES       .  98 

Various  kinds,  98. 


TABLE   OF   CONTENTS.  xi 

MM 

LIGHTING  WITH  LAMPS 98 

Various  oils  used,  98 ;  refining  fatty  oils,  98  ;  ancient  use  and  development  of  lamps,  99 ; 
evaporating  temperature  of  oils,  99  ;  suction  lamps,  100 ;  the  lamp  of  Schuster  and  Baer, 
100;  imperial  lamps,  101  ;  study  lamps,  101  ;  ligroine  and  sponge  lamp,  101. 

GAS  LIGHTING 101 

Materials  for  burners,  101  ;  various  classes  of  burners,  101  ;  Fr.  Siemens'  regenerative 
gas-burner,  101  ;  Auer  von  Welsbach's  burner,  103;  Fahnehjelm's  "globe-light,"  103; 
Gillard's  "platinum  gas,"  103  ;  the  Drummond  light,  104  ;  H.  Cohn,  quantity  of  light  for 
reading,  104  ;  cost  of  various  kinds  of  illumination,  104  ;  pollution  and  contamination  of 
the  air,  104  ;  economy  of  various  lights,  104. 

ELECTRIC  LIGHT 105 

Arc  light,  105  ;  Siemens  and  Halske's  apparatus  for  measuring  the  light,  105  ;  Von  Hefner- 
Alteneck's  experiments,  106  ;  intensity  of  light,  105. 


SECTION   II. 

METALLURGY. 

Chemical  processes,  108 ;  how  metals  are  found,  108  ;  dressing,  108  ;  preparation,  108  ;  smelting, 
108  ;  mixing,  109 ;  furnace  products,  109  ;  slags,  109;  various  kinds  of  slags,  no  ;  com- 
position of  slags,  no;  properties  of  metals,  no  ;  melting  and  boiling  point  of  metals,  no  ; 
specific  heat,  1 10 ;  thermo-conductivity,  in;  hardness,  1 1 1  ;  modification  of  the  hard- 
ness and  tenacity  of  metals,  112  ;  pliancy,  112  ;  treatment  of  metals  for  manufacture,  113  ; 
friction,  113  ;  welding,  113. 

IKON 113 

Magnetic  ironstone,  113 ;  red  ironstone  and  specular  iron,  113  ;  iron  spar,  113 ;  brown  iron 
ores,  114 ;  bean  ore,  114 ;  bog  iron  ore,  114  ;  Franklinite,  114  ;  classification,  114. 

CKUDE  IRON 114 

Roasted  ores,  114;  smelting  in  blast  furnaces,  114;  furnace  building,  115;  air  heating, 
115  ;  air-heater  of  Whit  well,  117;  Macco's  heater,  117;  smelting  process,  117;  heat  con- 
ditions of  the  blast  furnace,  117  ;  processes  of  reduction,  118  ;  experiments  in  the  refining 
process,  118;  importance  of  silica,  119;  melting-heat  of  crude  iron,  119  ;  melting-heat  of 
slags,  119;  decomposition  of  the  atmospheric  moisture,  119  ;  water  and  air  used  for  re- 
frigeration, 119  ;  losses,  119  ;  consumption  of  fuel,  120  ;  average  heat  required  for  smelt- 
ing, 121  ;  proportion  of  cyanogen  compounds  in  the  gases  and  dust,  122  ;  composition  of 
slags,  122  ;  analyses  of  slags,  123  ;  use,  123;  crude  iron,  123. 

EXAMINATION  OP  IRON  AND  STEEL 124 

Wohler's  process,  124;  for  determining  carbon,  124;  for  determining  sulphur,  124  ;  for 
determining  silicon,  124  ;  for  determining  phosphorus,  124  ;  analyses  of  crude  iron,  124. 

IKON  FOUNDING 125 

Various  methods,  125  ;  examination  of  Krigar  furnaces,  125;  analyses,  126  ;  melting  pig- 
iron  with  lime  and  fluor  spar,  126;  good  casting-iron,  126  ;  reverberatory  furnace,  126. 

WROUGHT  OR  BAR  IRON 127 

Improved  method  of  obtaining  wrought  iron,  127  ;  value  of  the  "direct"  process,  128  ; 
refining  process,  129;  hearth  refining,  129;  Swedish  fining,  129 ;  puddling,  129;  puddling 
furnace,  130  ;  bar-iron,  wrought  or  malleable  iron,  131  ;  chemical  examination  of  bar-iron, 
131 ;  welding,  132 ;  Siemens-Martin  and  Bessemer  processes,  132. 

STEEL 132 

Composition,  132;  how  obtained,  132;  rough  steel  or  natural  steel,  133;  puddled  steel, 
133 ;  Bessemer  steel,  133  ;  apparatus,  134 ;  analysis,  136 ;  basic  process  (of  Thomas  and 
Gilchrist),  136;  Finkener's  experiments,  136;  Hilgenstock's  experiment,  137;  the  slag, 
138;  the  Siemens- Martin  process,  138;  furnaces  at  Witkowitz,  139;  basic  hearth-smelt- 
ing, 140 ;  carbonisation  steel,  142  ;  sheer  steel,  142  ;  cast  steel,  142 ;  run  steel,  143 ;  infil- 
tration of  cast  blocks,  143  ;  steeling,  143  ;  properties  of  steel,  143  ;  Damascus  steel, '144; 
steel  engraving,  144. 


xu  TABLE  OF  CONTENTS. 

PAGE 

MANGANESE .       .       .       ...       .        •       •       .       •       •  145 

Occurrence,  145  ;  preparation,  145. 

COBALT *45 

Occurrence,  145  ;  cobalt  colours,  145  ;  smalts,  146 ;  cobalt  speiss,  146  ;  cobalt  ultra- 
marine,  146;  coeruleum,  146;  Rinmann's  or  cobalt  green,  146;  pure  protoxide  of  cobalt, 
147  ;  nitrite  of  protoxide  of  cobalt  and  potassa,  147 ;  cobalt  bronze,  147. 

NICKEL X47 

Occurrence,  147  ;  treatment  before  smelting,  147  ;  dry  process  for  nickel,  148  ;  wet  pro- 
cess, 148  ;  L.  Mond's  process  for  nickel,  149  ;  composition  of  cast  nickel,  149 ;  colour,  149. 

COPPER 15° 

Copper  ores,  150;  red  copper  ore,  150;  tile  ore,  150;  azurite,  150;  malachite,  150; 
chalkosine,  150  ;  copper  slate,  150  ;  enargite,  150  ;  Fahl  ores,  150  ;  atakamite,  150;  method 
of  obtaining  copper  from  its  ores,  150 ;  production  of  copper  in  the  dry  way,  151  ;  roast- 
ing of  the  copper  matte,  152  ;  eliquation,  153  ;  refining  copper,  153  ;  English  system  of 
copper  smelting,  154;  smelting  furnace,  154;  white  metal,  155  ;  refining  in  the  United 
States,  155  ;  copper  ores  worked  in  the  Bessemer  converter,  156  ;  working  crude  regulus, 
156  ;  production  of  copper  in  the  wet  way,  157  ;  Dotsch's  process,  158  ;  analysis  of  cement 
copper,  158  ;  fusion  with  a  reducing  flame,  159  ;  poling,  159  ;  general  treatment  of  coppers 
during  refining,  160  ;  composition  of  Mansfeld  coppers,  160  ;  tough  poling,  160  ;  obtaining 
and  refining  copper  by  electricity,  161 ;  Siemens  and  Halske's  method,  162  ;  machines  at 
Oker,  164  ;  Hilarion  Roux's  machines,  165  ;  properties  of  copper,  165  ;  uses  of  copper,  165; 
analysis  of  some  samples  of  refined  copper,  165  ;  copper  alloys,  166  ;  bell-metal,  166  ;  gun- 
metal,  167  ;  art-bronze,  167  ;  phosphor-bronze,  167  ;  brass,  167  ;  alloys  of  brass,  167  ;  bronze 
colours,  168  ;  German  silver,  168  ;  copper  amalgam,  168. 

LEAD 169 

Production,  169  ;  lead  smelting  furnace,  169  ;  English  process  for  the  production  of  lead, 
169 ;  composition  of  the  lead  ore  washings  of  the  Upper  Harz,  170 ;  treatment  of  ores  at 
Mechernich,  171  ;  flue-dust,  172  ;  work-lead,  172  ;  electric  production  of  lead,  172 ;  Keith's 
process,  173;  properties,  173;  uses,  173;  manufacture  of  small  shot,  173;  alloys,  174; 
production  of  lead,  174. 

SILVER 174 

Where  and  how  found,  174  ;  extraction,  174;  amalgamation,  175  ;  various  processes,  175  ; 
American  or  wet  process,  175  ;  Kroncke's  process,  176  ;  extraction  of  silver  by  solution  and 
precipitation,  176;  Augustin's  process,  177;  Ziervogel's  process,  178;  other  procedures, 
178;  extraction  of  silver  in  the  dry  way,  178;  the  Pattinson  process,  179;  desilvering 
lead,  1 80;  Plattner's  process,  180  ;  desilvering  work-lead  by  electricity,  185;  fine- burning 
silver,  185  ;  total  production  of  silver,  186  ;  chemically  pure  silver,  186;  silver  alloys,  187 ; 
silver  assay,  187  ;  silvering,  187  ;  electro-plating,  188  ;  oxidation  of  silver,  188. 

GOLD 188 

Occurrence,  188 ;  different  processes  for  extracting,  189 ;  W.  Crookes'  process,  190 ; 
Molloy's  process,  191  ;  Morgan  and  Longden's  process,  191  ;  Plattner's  process,  192  ; 
various  modifications,  192 ;  separation  of  gold,  194;  Gutzkow's  proposal,  194;  properties, 
J95  5  g°ld  alloys,  195  ;  gold  proof,  195  ;  gilding,  196  ;  galvanic  gilding,  197. 

PLATINUM I97 

Occurrence,  197 ;  analysis  of  various  ores,  197  ;  extraction,  197  ;  St.  Claire  Deville  and 
Debray's  process,  198  ;  properties,  198  ;  platinum  black,  198  ;  manufacture,  198. 


TIN 


199 


Tin-stone,  199  ;  treatment  of  ore,  199  ;  occurrence,  199  ;  properties,  200  ;  assay  of  tin  ores, 
200  ;  uses,  200  ;  tinning,  201. 

^ 

BISMUTH 2OI 

Occurrence,  201;  treatment  of  ore?,  202  ;  properties,  202 ;  uses,  202. 

ANTIMONY ....  202 

Occurrence,  202  ;  extraction,  203  ;  smelting  in  Hungary,  204  ;  electrolytic  extraction,  204  ; 
properties,  204  ;  alloys,  205. 


TABLE   OF  CONTENTS.  xiu 

PAGE 

ARSENIC     . 205 

Production,  205  ;  arsenious  acid,  205 ;  arsenic  acid,  206 ;  realgar,  206 ;  orpiment,  206. 

MERCURY    .  207 

Occurrence,  207  ;  production,  207  ;  furnaces  used,  208  ;  the  Knox-furnace,  209  ;  quantity 
and  price,  211 ;  furnace  at  Horzowitz,  211 ;  properties,  211  ;  detection,  212. 

ZINC 212 

Occurrence,  212  ;  treatment,  212  ;  Belgian  system,  212  ;  furnaces  at  Letmathe,  213  ;  English 
method,  214  ;  production  of  zinc  by  electricity,  214  ;  properties,  216  ;  uses,  217. 

CADMIUM 217 

Properties,  217  ;  occurrence,  218;  treatment,  218;  detection,  218. 

POTASSIUM  AND  SODIUM 218 

Production,  218 ;  manufacture  of  sodium,  218  ;  potassium,  220  ;  cost  of  manufacture,  22 1 ; 
uses,  221 ;  electrolytic  production  of  sodium,  221 ;  price  of  potassium,  221. 

ALUMINIUM 22. 

Woehler's  process  for  isolating,  221;  Cowles  Bros.'  process,  222;  result  according  t<> 
Mehner,  222  ;  according  to  Maberry,  222 ;  Prof.  Netto's  process,  223  ;  properties,  223  ;  appli- 
cations, 223 ;  alloys,  223  ;  aluminium  bronze,  223. 

MAGNESIUM 224 

Occurrence,  224  ;  production,  224  ;  Bunsen's  method,  224  ;  modification  by  Graetzel,  225  ; 
uses,  225. 


SECTION  III. 

CHEMICAL  MANUFACTURING  INDUSTRY. 

WATER  AND  ICE 226 

Occurrence,  226  ;  quantity,  226  ;  distribution  of  rainfall,  226  ;  composition,  226  ;  impurities, 
227  ;  spring  and  well  water,  227  ;  examination  of  waters,  228  ;  process  used  by  W.  Crookes, 
W.  Odling,  and  C.  M.  Tidy,  228  ;  purification  of  water,  229  ;  water  for  steam  boilers,  229  ; 
breweries,  230;  distilleries,  230  ;  starch  works,  230;  sugar  works,  231  ;  paper  mills,  231  ; 
tanneries,  231  ;  manufacture  of  glue,  231  ;  bleach  and  dye  works,  231  ;  water  for  municipal 
and  domestic  supplies,  233  ;  various  kinds  of  soap  to  be  used,  233  ;  water  used  for  baking, 
234 ;  washing  the  floors,  &c.,  234  ;  in  the  construction  of  houses,  234  ;  filtering  water,  234 ; 
speed  of  filtration,  235  ;  effects  of  sand  filtration,  236  ;  analysis  by  Koch,  236 ;  various 
analyses,  237  ;  softening  water — the  Clarke  process,  237 ;  Bohlig's  process,  238  ;  E.  de  Haen's 
process,  239  ;  distillation,  239  ;  of  sea-water,  239  ;  water  mains,  240. 

ARTIFICIAL  MINERAL  WATERS 241 

Production,  241 ;  ice,  242 ;  uses  in  works,  242  ;  artificial  production,  242 ;  evaporation  ice 
machines,  242  ;  Pictet's  machine,  243. 

SULPHUR 244 

Occurrence,  244  ;  extraction,  244  ;  distillation  process,  245  ;  fusion  process,  245  ;  refining, 
245  ;  apparatus,  246 ;  Michel's  apparatus,  246  ;  Dujardin's  apparatus,  247  ;  sulphur  from 
iron  pyrites,  247 ;  sulphur  from  roasting  copper  ores,  248  ;  gas  sulphur,  248 ;  from  sul- 
phurous acid  and  sulphuretted  hydrogen,  248  ;  from  sulphurous  acid  and  carbon,  249 ; 
from  sulphuretted  hydrogen,  249 ;  properties,  249-50 ;  carbon  disulphide,  249  ;  sulphur 
chloride,  251  ;  sulphurous  and  sulphuric  acids,  251  ;  furnaces,  251 ;  kilns  used  at  the  Oker 
works,  252 ;  pyrites  kilns  used  at  Marseilles,  253  ;  Gerstenhofer  roasting  kilns,  254  ;  Hasen- 
clever  and  Helbig  kiln,  255  ;  plate  furnace  of  Maletra,  255  ;  roasting  blende,  256  ;  blende 
furnace,  257  ;  composition  of  the  roasting  gases,  259  ;  liquid  sulphurous  acid,  259  ;  proper- 
ties, 260  ;  applications,  260 ;  calcium  sulphite,  261 ;  sodium  thiosulphate,  261. 

SULPHURIC  ACID 262 

Fuming  sulphuric  acid,  262 ;  properties,  263  ;  solid  oil  of  vitriol,  263  ;  ordinary  sulphuric 
acid,  263 ;  lead  chambers,  263 ;  arrangements  for  collecting  the  nitrous  vapours,  265  ; 
denitration  of  the  nitrose,  266 ;  Gay-Lussac's  denitrificator,  266 ;  J.  Glover's  tower,  267 ; 
Laurent's  apparatus  for  raising  sulphuric  acid,  268  ;  lead  chamber  process,  270  ;  formation 


adv  TABLE   OF   CONTENTS. 

PAG* 

of  sulphuric  acid  in  the  lead  chambers,  271 ;  purification  of  chamber  acid,  274 ;  concentra- 
tion of  sulphuric  acid,  275  ;  concentration  in  leaden  pans,  275  ;  completion  of  concentra- 
tion, 276 ;  apparatus  used  in  Britain,  277  ;  at  Muehlheim,  277 ;  platinum  still,  278  ;  apparatus 
of  Johnson,  Matthey  &  Co.,  279;  concentrator  of  Faure  and  Kessler,  280;  composition, 
281 ;  modern  proposals  for  manufacturing  sulphuric  acid,  281. 

PROPERTIES  OF  SULPHURIC  ACID 282 

Specific  gravity,  282 ;  applications,  282. 

POTASSIUM  SALTS 283 

Occurrence,  283  ;  potassa  salts  from  the  Stassfurt  salt  mine,  283  ;  preparation  of  potas- 
sium chloride,  283 ;  Mr.  A.  Frank's  process,  283  ;  Dupre's  method,  284  ;  manufacture  of 
Glauber's  salts,  285 ;  kainite,  286 ;  production  of  potassium  carbonate,  286  ;  analysis  of, 
286  ;  various  processes,  287  ;  salts  of  potassium  from  the  ashes  of  plants,  287  ;  value  of 
ash,  288  ;  lixiviation  of  the  ash,  289  ;  boiling  down  the  liquor,  289  ;  calcination  of  crude 
potash,  289  ;  American  potash,  290  ;  salts  of  potassium  from  the  treacle  of  beet-root  sugar, 
291  ;  various  analyses,  291 ;  treatment  of  molasses,  292  ;  salts  of  potassium  from  seaweeds, 
295  ;  French  method,  295  ;  Scotch  mode,  295  ;  Stanford's  method,  296  ;  salts  of  potas- 
sium from  the  suint  of  wool,  297  ;  Maumene'  and  Rogelet's  patent,  297  ;  caustic  potash, 
299  ;  alkalimetry,  300 ;  commercial  potash,  300  ;  Mohr's  normal  solution,  300 ;  commer- 
cial value,  300. 

COMMON  SALT  AND  SALT  WORKS 302 

Occurrence,  302  ;  method  of  preparing  common  salt  from  sea  water,  302  ;  in  salines,  303  ; 
by  freezing,  303  ;  by  artificial  evaporation,  304  ;  rock-salt,  304  ;  composition,  304 ;  mode 
of  working  rock-salt,  305  ;  salt-springs,  306  ;  preparation  of  common  salt  from  brine,  306 ; 
concentrating  the  brine,  306  ;  enriching  by  gradation,  306  ;  faggot  gradation,  306  ;  boil- 
ing down  the  brine,  307  ;  properties  of  common  salt,  307  ;  uses  of  common  salt,  309. 

SODA 309 

NATURAL  SODA 309 

Occurrence,  309 ;  La  Lagunilla,  309. 

SODA  FROM  PLANTS 310 

SODA   OBTAINED   BY   CHEMICAL   MEANS JJQ 

The  Leblanc  process,  310;  Gossage's  patent,  311  ;  salt-cake  furnaces,  312  ;  sulphate  fur- 
naces of  Mactear,  312;  Hargreaves  and  Eobinson's  process  for  salt-cake,  313  ;  hydro- 
chloric acid,  313  ;  properties,  313  ;  applications,  314  ;  sodium  sulphate,  314;  applications, 
315  ;  conversion  of  sulphate  into  crude  soda,  315  ;  rotating  soda  furnace,  317  ;  conversion 
of  crude  soda  into  purified  soda,  318 ;  lixiviation,  319 ;  C.  Desormes'  apparatus,  319  ; 
Durre's  apparatus,  321  ;  Shanks'  apparatus,  321  ;  treatment  of  lyes,  321  ;  composition, 
323  ;  purification  and  concentration  of  the  lye,  323  ;  analysis  of  soda-lyes,  324 ;  use  of  re- 
verberatory,  325  ;  producing  soda  crystals,  326  ;  theory  of  the  formation  of  soda,  328 ; 
utilisation  of  the  Leblanc  soda-residues,  329  ;  obtaining  sulphur-lye,  330  ;  Mond's  recovery 
process,  332  ;  P.  W.  Hofmann's  process,  334  ;  Divers'  process,  336  ;  C.  Opl's  process,  337  ; 
Chance's  new  process,  337  ;  ammonia-soda  process,  339 ;  cryolite  soda,  343 ;  soda  from 
sodium  sulphate,  343  ;  caustic  soda,  343 ;  Lunge's  advice  for  the  oxidation  of  sulphides, 
344 ;  Deacon  and  Hurter's  process,  345  ;  sodium  bicarbonate,  346. 

CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES .  347 

Production,  347 ;  apparatus  at  the  Josephsthal  paper  works,  347  ;  Dunlop's  process,  347  ; 
Gatty's  process,  348  ;  F.  Kuhlmann's  process,  348  ;  Weldon's  process,  348 ;  obtaining 
chlorine  without  manganese,  350  ;  Deacon  and  Hurter's  process,  350  ;  MacDougal,  Kawson, 
and  Shanks'  process,  352 ;  Vogel's  method,  352 ;  Peligot's  method,  352 ;  properties  and 
uses  of  chlorine,  358  ;  chloride  of  lime,  358 ;  liquid  chloride  of  lime,  359 ;  properties  of 
chloride  of  lime,  360;  loss  of  value,  360  ;  chlorometry,  361  ;  Penot's  test,  361  ;  Wagner's 
method,  361  ;  Lunge's  method,  362 ;  chlorometric  degrees,  363  ;  chloride  of  alkali,  363  ; 
potassium  chlorate,  363  ;  properties,  364 ;  potassium  perchlorate,  364. 

BBOMINE _  -g- 

Occurrence,  365  ;  distillation,  365  ;  A.  Frank's  process,  365 ;  apparatus  used  at  united 
chemical  works  of  Leopoldshall,  366  ;  crude  bromine,  369 ;  properties  and  applications  of 
bromine,  368. 


TABLE   OF  CONTENTS.  xv 

PA&B 

IODINE 368 

Production,  368 ;  from  seaweed,  369  ;  Allary  and  Pellieux'  method,  370 ;  Vitali's  method, 
370  ;  properties  and  uses,  371. 

NITRIC  ACID  AND  NITRATES  .  371 

Soda  saltpetre,  371  ;  sodium  nitrate,  372  ;  potassium  saltpetre,  373  ;  occurrence  of  native 
saltpetre,  373  ;  mode  of  obtaining  saltpetre,  373  ;  treatment  of  the  ripe  saltpetre  earth, 
373  5  preparation  of  raw  lye,  374;  breaking  up,  374;  boiling  down,  375  ;  refining  crude 
saltpetre,  375  ;  preparation  of  potassium  nitrate  from  Chili  saltpetre,  376 ;  testing  the  salt- 
petre, 378 ;  Wagner's  method,  378  ;  uses  of  saltpetre,  379. 

NITRIC  ACID 379 

Methods  of  manufacture,  379  ;  bleaching,  380 ;  condensation,  380 ;  preparing  chemically 
pure,  381  ;  densities,  382  ;  technical  applications,  383. 

EXPLOSIVES 384 

Gunpowder,  384  ;  manufacture,  384  ;  mechanical  operations  of  powder  manufacture,  384  ; 
pulverising  the  ingredients,  384  ;  mixing  the  ingredients,  385  ;  caking  and  pressing  the 
powder,  385  ;  granulation  of  the  cake,  and  sorting  the  powder,  385  ;  Congreve's  granu- 
lating machine,  386  ;  polishing  the  granulated  powder,  386;  drying  the  powder,  386 ;  sifting 
the  dust  from  the  powder,  387  ;  properties  of  gunpowder,  387  ;  composition,  388  ;  products 
of  combustion,  388  ;  testing,  390  ;  pyrotechnics,  390  ;  chemical  principles  of  pyrotechny, 
390  ;  the  more  commonly  used  firework  mixtures,  390  ;  saltpetre  and  sulphur  mixture,  391  ; 
grey-coloured  mixture,  391  ;  potassium  chlorate  mixtures,  friction  mixtures,  percussion 
powders,  391  ;  mixture  for  igniting  the  cartridges  of  needle-guns,  391 ;  heat-producing 
mixtures,  392  ;  coloured  fires,  392  ;  more  recent  explosives,  392  ;  nitroglycerine,  393  ; 
Nobel's  dynamite,  395  ;  gun-cotton,  395  ;  properties  of  gun-cotton,  396  ;  apparatus  of  Hess 
for  determining  the  chemical  stability  of  explosives,  398  ;  Alberts'  examination  of  gun- 
cotton,  397  ;  collodion  cotton,  398  ;  fulminating  mercury,  398  ;  percussion-caps,  398. 

AMMONIA 399 

Preparation  of  liquid  ammonia,  399  ;  inorganic  sources  of  ammonia,  400  ;  organic  sources 
of,  401  ;  Mallet's  apparatus,  401  ;  Lunge's  apparatus,  401  ;  H.  Griineberg's  apparatus,  402  ; 
stairs  column,  404  ;  apparatus  of  J.  Gareis,  405  ;  ammonia  from  lant,  405  ;  apparatus 
contrived  by  Figuera,  406  ;  ammonia  from  bones,  406  ;  from  beet-root,  407  ;  technically 
important  ammoniacal  salts,  407  ;  ammonium  sulphate.  409  ;  ammonium  carbonate,  409  ; 
ammonium  nitrate,  409  ;  C.  O.  Harz,  manurial  value  of  ammoniacal  salts,  410. 

PHOSPHORUS 410 

Preparation  of  phosphorus,  410 ;  composition  of  bone  ash,  410 ;  burning  the  bones  to  ash, 
411  ;  decomposition  of  bone  ash  by  sulphuric  acid,  411  ;  distillation  of  phosphorus,  412  ; 
refining  and  purifying  the  phosphorus,  413  ;  another  process,  413  ;  moulding  the  refined 
phosphorus,  414  ;  Fleck's  process  for  obtaining  phosphorus,  415  ;  properties  of  phosphorus, 
416;  amorphous  or  red  phosphorus,  416;  Dr.  Schrotter's  experiment,  416;  properties  of 
amorphous  phosphorus,  417  ;  production,  417. 

MATCHES  :  PRODUCTION  OP  FIRE 417 

Db'bereiner's  hydrogen  lamp,  417  ;  phosphorus  match,  417  ;  manufacture  of  lucifer  matches, 
419  ;  preparation  of  wooden  splints,  419  ;  preparation  of  the  combustible  composition,  420 ; 
dipping  and  drying  the  splints,  421  ;  dipping  apparatus  of  Eoller,  422 ;  matches  with 
amorphous  phosphorus,  422  ;  wax  or  vesta  matches,  423 ;  B.  Forster  and  F.  Wara's  "  non- 
poisonous  "  match,  423  ;  Zulzer's  machine  for  cutting  tapers,  424. 

PHOSPHATES:  MANURES 424 

Poudrette,  424  ;  guano,  424  ;  bone  meal,  425  ;  precipitated  tricalcium  phosphate,  425  ;  super- 
phosphate, 425;  coprolites,  426;  double  superphosphate,  426;  preparation  of  solutions, 

427. 

BORIC  ACID  AND  BORAX 427 

Occurrence,  427 ;  theory  of  the  formation  of  native  boric  acid,  428  ;  production,  428 ; 
properties  and  uses,  429  ;  borax,  429  ;  from  boric  acid,  430  ;  prismatic  borax,  430 ;  purify- 
ing borax,  431 ;  octahedral  borax,  432  ;  uses,  432 ;  manufacture  of  borax  in  Germany,  433 ; 
diamond  boron  or  adamantine,  434  ;  Wohler  and  H.  Deville's  observations,  434. 

SALTS  OP  ALUMINIUM 435 

Alum,  435  ;  material  of  alum  manufacture,  435  ;  preparation  of  alum  from  alum  stone  (ist 
group),  435  ;  from  alum  shale  and  alum  earths  (2nd  group),  436  ;  preparation  of  alum,  436  ; 


rri  TABLE  OF  CONTENTS. 

*      *  1 

roasting  the  alum-earth,  436  ;  lixiviation,  436  ;  evaporation  of  the  lye,  436  ;  alum-flour, 
437  ;  washing  and  re-crystallisation,  437  ;  preparation  of  alum  from  clay  (3rd  group),  437  ; 
from  cryolite,  438  ;  decomposition  of  cryolite  according  to  Thomsen's  method,  438  ;  decom- 
position of  cryolite  with  caustic  lime  by  the  wet  way  (Sauerwein's  method),  438  ;  decom- 
position by  sulphuric  acid,  439  ;  preparation  of  alum  from  bauxite,  439  ;  from  blast  furnace 
slag,  439;  from  felspar  (4th  group),  439;  properties  of  alum,  440;  ammonia  alum,  440; 
soda  alum,  440  ;  neutral  or  cubical  alum,  441 ;  aluminium  sulphate,  441 ;  composition,  441 ; 
H.  Fleck's  analyses  of  cake-alum,  441 ;  preparation  of  cake-alum,  442  ;  sodium  aluminate, 
442  ;  aluminium  hydrate,  443  ;  applications  of  alum  and  aluminium  salts,  443. 

ULTRAMARINE .  444 

Haw  materials,  444  ;  manufacture,  444 ;  preparation  of  sulphate  ultramarine,  444 ;  green 
ultramarine,  445  ;  Stolzel's  analysis,  445  ;  conversion  of  green  into  blue  ultramarine,  446  ; 
preparation  of  soda  ultramarine,  446  ;  of  silica  ultramarine,  446 ;  siliceous  blues  from 
Hirschberg  works  and  from  Marienberg  works,  447  ;  violet  and  red  ultramarines,  447  ; 
constitution  of  ultramarine,  447  ;  properties,  448 ;  adulterations,  448. 

COMPOUNDS  OP  TIN  AND  ANTIMONY  .    • 448 

Mosaic  gold,  448  ;  tin  crystals,  448  ;  tin  chloride,  stannic  chloride,  449  ;  nitrate  of  tin,  449 ; 
pink  salt,  449  ;  stannate  of  soda  (sodium  stannate),  449. 

COMPOUNDS  OP  ANTIMONY 449 

Antimony  oxide,  449 ;  black  antimony  sulphide,  449  ;  Neapolitan  yellow,  450 ;  antimony 
cinnabar,  450  ;  pentasulphide,  450. 

COMPOUNDS  OP  ARSENIC 450 

Arsenic  acid,  450  ;  plant,  450 ;  uses,  452  ;  how  tested,  452. 

COMPOUNDS  OF  GOLD,  SILVER,  AND  MERCURY 452 

Cassius's  purple,  gold  purple,  452  ;  salts  of  gold,  452  ;  salts  of  silver,  silver  nitrate,  lunar 
caustic,  452  ;  marking  ink,  452  ;  mercurial  compounds,  453  ;  mercuric  oxide,  453  ;  mercuric 
chloride,  453  ;  cinnabar  or  vermilion,  453  ;  red  lead,  454. 

COMPOUNDS  OP  COPPER .  .  454 

Copper  sulphate,  blue  vitriol,  blue  stone,  454  ;  preparation  of  blue  vitriol,  454 ;  double 
vitriol,  455  ;  applications  of  blue  vitriol,  455  ;  copper  pigments,  455  ;  Brunswick  green, 
455  ;  Bremen  blue  or  Bremen  green,  456  ;  Casselmann's  green,  457  ;  mineral  green  and  blue, 
457  ;  oil  blue,  457  ;  Schweinfurt  green  or  emerald  green,  457  ;  copper  stannate,  458  ;  ver- 
digris, 458  ;  applications  of  verdigris,  459  ;  Egyptian  blue,  459. 

COMPOUNDS  OP  ZINC  AND  CADMIUM        .        . 459 

Zinc  white,  459  ;  white  vitriol,  zinc  sulphate,  460  ;  zinc  chromate,  460  ;  zinc  chloride,  460  ; 
cadmium  yellow,  461. 

COMPOUNDS  OP  LEAD ,: 461 

Lead  oxide,  461  ;  massicot,  461  ;  litharge,  461  ;  minium,  red  lead,  461  ;  lead  peroxide,  462; 
white  lead,  462  ;  methods  of  manufacture,  463  ;  English,  French,  methods,  463  ;  apparatus 
used  at  Clichy,  463  ;  improvements  suggested,  464  ;  theory  of  preparing  white  lead,  464 
properties,  465  ;  adulteration,  465  ;  applications,  466 ;  white  lead  from  chloride  of  lead, 
467  ;  basic  lead  chloride  as  a  substitute  for  white  lead,  467  ;  lead  sulphate,  467  ;  Cassel 
yellow  and  Turner's  yellow,  467. 

COMPOUNDS  OP  MANGANESE  AND  CHROMIUM 467 

Manganese,  467  ;  testing  the  quality,  468  ;  potassium  permanganate,  468  ;  uses,  468  ; 
preparation,  468  ;  chromates,  469  ;  Jacquelain's  method  of  preparation,  469  ;  application 
of  potassium  chromates,  470  ;  sodium  chromate,  470  ;  chromic  acid,  470 ;  chrome  yellow, 
lead  chromate,  470;  chrome  red,  471  ;  chromic  oxide  or  chrome  green,  472;  Guignet's 
green,  472  ;  chromic  hydrate,  472  ;  Dingler's  green,  472 ;  Casali  green,  473  ;  chrome  alum, 
473  5  chromium  chloride,  473  ;  basic  ferric  chromate,  473. 

IBON  COMPOUNDS,  INCLUDING  FERROCYANOGEN .        .        .  473 

Copperas  or  green  vitriol,  473  ;  preparation  as  a  bye-product  in  alum  works,  473  ;  in  beds, 
473  ;  green  vitriol  from  the  residues  of  pyrites  distillation,  473  ;  from  metallic  iron  and 
sulphuric  acid,  473  ;  from  spathic  iron  ore,  474  ;  uses,  474  ;  iron  minium,  474 ;  potassium 
ferrocyanide,  474;  theory  of  its  formation,  475;  applications  of  yellow  prussiate,  476; 
manufacture  of  ferrocyanide,  476  ;  potassium  ferricyanide,  477 ;  preparation,  477  ;  potas- 


TABLE   OF   CONTENTS.  xvii 

PAGE 

slum  cyanide,  477  ;  Prussian  blue,  477  ;  neutral  Berlin  blue,  478  ;  basic  Berlin  blue,  478  ; 
old  method  of  preparing  Prussian  blue,  478  ;  recent  methods  of  preparing  Berlin  blue,  479  ; 
Turnbull's  blue,  479  ;  Berlin  blue  as  a  bye-product  of  the  manufactures  of  coal-gas  and 
animal  charcoal,  479 ;  soluble  Berlin  blue,  479  ;  pure  Berlin  blue,  479. 

CONSPECTUS  OF  INORGANIC  PIGMENTS 480 

Whites,  reds,  yellows,  480  ;  greens,  blues,  481. 

THEEMO-CHEMISTEY 481 

Uses,  481 ;  the  unit  used,  482  ;  various  heat-units,  482  ;  production  of  chlorine,  483  ; 
Deacon's  oxidation  process,  483  ;  Pechiney's  'decomposition  furnace,  483  ;  various  appli- 
cations, 483. 


SECTION   IV. 

THE  ORGANIC  CHEMICAL  MANUFACTURES. 

ALCOHOLS  AND  ETHERS 486 

Methylic  alcohol,  486 ;  distillation,  486  ;  uses,  487 ;  ethyl  alcohol,  487  ;  percentage 
hydrometers,  487  ;  O.  Hehner's  alcohol  tables,  488  ;  chloroform,  490  ;  apparatus  used  for 
distilling,  490  ;  Giinther's  method,  491  ;  production  of  iodoform,  491  ;  chloral  hydrate, 
491  ;  ether,  491. 

ORGANIC  ACIDS 491 

Acetic  acid,  491 ;  various  kinds  of  vinegar,  491  ;  older  method  of  vinegar  making,  492  ; 
quick  vinegar  making,  492  ;  Singer's  vinegar  generator,  494 ;  Michaelis'  process,  494  ; 
Pasteur,  action  of  bacteria  on  the  formation  of  vinegar  from  alcohol,  494  ;  vinegar  by 
means  of  platinum  black,  495  ;  Dobereiner's  process,  495  ;  properties  and  examination  of 
vinegar,  496;  acetometry,  496;  apparatus  for  determining  the  value  of  vinegar,  496; 
testing  vinegar  essence,  497  ;  wood  vinegar,  497  ;  purifying  wood  vinegar,  497  ;  principal 
methods,  498  ;  Stoltze's  method,  498  ;  formic  acid,  498  ;  butyric  acid,  499  ;  valerianic  acid, 
499  ;  oxalic  acid,  499  ;  Thorn's  method  of  obtaining,  499  ;  Merz's  method,  500  ;  lactic  acid, 
500 ;  tartaric  acid,  500 ;  Dieter's  process,  501  ;  yearly  production  of  tartaric  acid,  501  ; 
citric  acid,  502  ;  benzoic  acid,  502  ;  sodium  benzoate,  502  ;  tannin,  502  ;  uses,  502. 

TREATMENT  OP  COAL-TAR 502 

Specific  gravity,  502  ;  distillation  of  tar,  503  ;  Lunge's  process,  503  ;  the  stills,  505  ;  cooler 
for  pitch,  507  ;  Haussermann's  analysis,  507  ;  value  of  pitch,  507  ;  light  oil,  508  ;  apparatus 
used  in  English  manufactories,  508;  Coupler's  apparatus,  509;  apparatus  for  obtaining 
pure  benzene,  510;  Bannow's  boiling  vessel,  510;  benzene,  511  ;  toluol,  511  ;  the  light 
oil,  511  ;  crude  carbolic  acid,  511  ;  phenol,  512;  cresol,  512  ;  subliming  chamber,  512  ; 
naphthaline,  513  ;  anthracene,  514. 

ORGANIC  COLOURING  MATTERS 514 

Red  colours,  514;  madder,  514;  madder  lake,  515  ;  flowers  of  madder,  515  ;  azale,  515  ; 
garancine,  515  ;  garanceux,  515  ;  colorine,  516  ;  safflower,  516  ;  cochineal,  516  ;  carthamine, 
516  ;  lac  dye,  517  ;  Tyrian  purple,  517  ;  weed  colours,  517  ;  less  important  red  dyes,  518  ; 
murexide,  518  ;  red  woods,  518  ;  production  of  red  ink,  518  ;  brasilein,  518;  adulteration 
ofdyewoods,  519;  blue  colouring  matters,  519;  indigo,  519;  properties  of  indigo,  520; 
testing,  520;  indigo  blue,  521  ;  artificial  indigo,  522  ;  logwood  or  campeachy,  522;  litmus, 

522  ;  hematine,   522  ;    turnesol  rags,  522 ;    yellow  colouring  matters,  522 ;   fustic,  522 ; 
young  fustic,  522  ;  annatto,  523  ;   berries — Persian,  French,  or  Turkey,   523 ;   turmeric, 

523  ;  weld  or  wold,  523  ;  quercitron,  523  ;  some  other  yellow  dye-wares,  523  ;  brown,  green, 
and  black  colours,  523  ;  tannin  ink,  524  ;  inks,  various,  524. 

TAR  COLOURS 524 

Arrangement  into  natural  groups,  524  ;  mtro-compounds,  524  ;  azo-colours,  524 ;  indamines 
and  indophenoles,  525  ;  saffranines,  525  ;  indulines  and  nigrosines,  526 ;  Schultz  and 
Julius'  arrangement  of  colouring  matters,  526. 

BaiNzoL  COLOURS 528 

Nitro-benzol,  528  ;  aniline,  528  ;  composition  of  aniline  oil,  530 ;  pure  aniline,  530 ; 
toluidine,  530;  aniline  red  (magenta),  530;  arsenic  acid  process,  531;  Schoop's  melting- 


xviii  TABLE   OF   CONTENTS. 

PAGE 

pot,  531  ;  purification  of  crude  magenta,  533  ;  Coupier's  process,  534 ;  rosaniline,  535 
aniline  blue,  535  ;  treatment,  536 ;  De  Laire  and  Girard's  treatment,  536  ;  aniline  violet, 
537  ;  methyl  violet,  537  ;  aniline  green,  537  5  fast  green,  538  ;  aniline  yellow,  538  ;  flav- 
aniline,  538 ;  aniline  black,  538 ;  formula,  538 ;  jetoline,  538 ;  benzaldehyd  green  or 
malachite  green,  539  ;  preparation,  539  ;  dimethyl  aniline,  539 ;  separation  of  oil  and  water, 
539  ;  Miihlhauser,  manufacture  of  malachite  green,  540  ;  obtaining  the  leuko-base,  540 ; 
production  of  liquid  colour,  543  ;  liquid  green,  543  ;  "  navy  blue,"  543  ;  brilliant  green, 
emerald  green,  new  Victoria  green,  543  ;  acid  green,  544  ;  apparatus  for  producing  leuko- 
base,  544  ;  for  obtaining  lead  peroxide  for  oxidation,  545  ;  acid  green,  545  ;  resorcine,  546 ; 
fluoresceine  colouring  matters,  547 ;  tetrabromfluoresceine,  547 ;  dibromfluoresceine, 
548 ;  ethyltetrabromfluoresceine,  548 ;  dibromdinitrofluoresceine,  548 ;  tetraiodofluor- 
esceine,  548;  di-iodofluoresceine,  548  ;  Miihlhauser's  method  of  obtaining  fluoresceine,  548  ; 
utilisation  of  the  residues,  55 1  ;  eosine  orange,  552  ;  spirit  cosine,  552 ;  dinitrodi- 
bromfluoresceine,  554 ;  erythrosine  B,  556  ;  erythrosine  G,  556  ;  phloxine,  556  ;  resorcine 
blue,  lacmoid,  557 ;  auramines,  557  ;  nitrosodimethyl  aniline,  558  ;  new  blue,  558  ;  gallo- 
cyanine,  558  ;  methylene  blue,  558  ;  zinc  sulphide  process,  562 ;  Lauth's  violet,  563 ; 
Bernthsen's  method,  563  ;  induline,  saffranine,  phenosaffranine,  neutral  blue,  giro  fie, 
imperial  yellow,  564 ;  phenol  colouring  matters,  564 ;  picric  acid,  564 ;  phenyl  brown, 
565  ;  flavaurine,  565  ;  Victoria  yellow,  565  ;  aurine,  565  ;  coralline,  565  ;  azuline,  565 ; 
quinoline,  565  j  Dobner  and  Miller's  experiment,  566  ;  quinoline  green,  blue,  red,  yellow, 
566 ;  salicylic  acid,  567  ;  salicyl  yellow,  567  ;  naphthaline  dye-stuffs,  567  ;  distillation  of 
naphthaline,  569;  phthalic  acid,  570;  naphthaline  red,  570;  Martius'  yellow,  570; 
naphthol  yellow,  570;  brilliant  yellow,  570;  sun  gold,  570;  naphthol  green,  571  ;  phen- 
anthrenered,  571 ;  anthracene  colours,  571  ;  alizarine,  571  ;  changes  in  the  melting  process, 
572  ;  purpurine,  573  ;  alizarine  orange,  573  ;  alizarine  carmine,  573  ;  alizarine  blue,573  ;  azo 
dyes,  574;  aniline  yellow,  574;  acid  or  fast  yellow,  574  ;  Bismarck  brown,  574  ;  benzopur- 
purine,  575  ;  a  scarlet  dye- ware,  576  ;  chrysophanine,  577  ;  croceine  scarlet,  577  ;  Biebrich 
scarlet,  577  ;  double  brilliant  scarlet,  578 ;  woollen  black,  578 ;  Congo,  578  ;  preparation 
of  mixed  azo-dyes,  578  ;  other  organic  colouring  matters,  379 ;  galleine,  579  ;  ceruleine, 
579;  galloflavine,  580;  the  Baden  Aniline  Company's  process,  580;  styrogallol,  580; 
tartrazine,  580;  canarine,  580;  murexide,  581  ;  lampblack  (soot),  581. 

EXAMINATION  OP  COLOURING  MATTERS 582 

Treatment  of  sample,  582  ;  Goppelsroeder's  method,  582  ;  acid  colouring  matters,  583. 

ARTIFICIAL  COLOURS  SOLUBLE  IN  WATEB 584 

Basic  colouring  matters,  584  ;  acid  colours,  584. 

SOLID  OR  PASTY  COLOURS,  INSOLUBLE  IN  WATER 585 

Treatment  of  dye-wares,  585  phasic  colouring  matters,  585  ;  acid  colouring  matters — 
phthaleines,  587  ;  sulphonised  rosaniline  derivatives,  587  ;  nitro-colouring  matters,  587  ; 
benzido-azo  colouring  matters,  588  ;  azo  colours — yellow  orange,  589  ;  Bordeaux  reds,  589  ; 
anthracene  derivatives,  590  ;  colouring  matters  insoluble  in  water,  591. 


SECTION   V. 


MANUFACTURE 592 

Antiquity,  592  ;  composition,  592  ;  soda  glass,  593  ;  potash  glass,  593  ;  Schott's  experiments, 
594 ;  E.  Weber's  analyses,  594  ;  Pelouze's  glasses,  595 ;  Lamy's  attempts  to  introduce 
thallium  into  glass,  595  ;  Maes'  optical  glass,  595  ;  bottle  glass,  595  ;  analysis  of  bottles, 
596  ;  lime-alumina  glass,  596  ;  phosphatic  glass,  596  ;  solubility  of  glass,  596  ;  Emmerling's 
analysis,  597;  Kreusler,  reactions  of  glass,  598  ;  Stass's  experiments,  598  ;  Weber  and  Wiebe's 
experiments,  598  ;  devitrification,  598  ;  coloured  glasses,  598  ;  hematinon,  598  ;  aventurine 
glass,  598  ;  gold  ruby  glass,  599  ;  red  glass,  599  ;  Venetian  mosaic  glass,  599  ;  composition, 
600 ;  physical  properties  of  glass,  600 ;  raw  materials  used  in  glass  making,  600 ; 
bleaching,  601  ;  utilisation  of  refuse  glass,  602  ;  melting  vessels,  602  ;  glass-furnace,  603  ; 
Siemens'  gas-oven,  604  ;  manufacturing  bottles,  605  ;  tank  furnaces,  606  ;  Boetius'  furnace, 
607  ;  glass  melting,  607  ;  melting  the  glass  material,  607  ;  clear  melting,  607  ;  cold- 


TABLE   OF   CONTENTS.  six 

rtm 

stoking,  608  ;  defects  in  glass,  608  ;  various  kinds  of  glass,  609  ;  plate  and  window  glass, 
609;  tools,  610;  crown  glass,  610  ;  sheet,  or  cylinder  glass,  611  ;  plate  glass,  612; 
melting  and  clearing,  613  ;  polishing,  613  ;  silvering,  614  ;  by  precipitation,  614;  platinis- 
ing, 614  ;  gilding,  614 ;  bottle  glass,  615  ;  details  of  manufacture,  615  ;  pressed  and  cast 
glass,  616;  hardened  glass,  616  ;  soluble  glass,  617  ;  water  glass,  618  ;  stereochromy,  618  ; 
crystal  glass,  619 ;  polishing,  620 ;  optical  glass,  620  ;  Rev.  Mr.  Harcourt's  researches, 
620  ;  strass,  621  ;  Donault-Wieland's  analysis,  621  ;  coloured  glass  and  glass  staining,  622  ; 
satin  glass,  623  ;  painting  on  glass,  623  ;  enamel,  bone  glass,  alabaster  glass,  624  ;  cryolite 
glass,  624  ;  ice  glass,  624  ;  muslin  glass,  625  ;  glass  relief,  625  ;  iridescent  glass,  625  ;  filigree 
or  reticulated  glass,  625  ;  millifiore  work,  625  ;  glass  pearls,  625  ;  solid  pearls,  625  ;  blown 
pearls,  626  ;  glass  etching,  626  ;  sand  blast  machine,  628. 

EAETHENWAEE  OB  CERAMIC  MANUFACTURE 628 

Weathering,  628  ;  clays  and  their  application,  628  ;  felspar,  628  ;  Seger's  examination 
of  clays,  629 ;  technical  qualities,  629  ;  colour,  629 ;  plasticity,  629  ;  kinds  of  clays,  630 ; 
chemical  composition,  631  ;  analyses,  631  ;  by  Sir  F.  A.  Abel,  631  ;  potter's  clay,  631  ; 
fuller's  earth,  631  ;  marl,  632  ;  loam,  633  ;  behaviour  of  clays  in  working,  633 ;  changes 
of  colour  in  burning,  634 ;  efflorescences,  634  ;  green  eruptions,  634 ;  black  spots,  634  ; 
Seger's  examination  of  change  of  colour,  635  ;  infusibility,  635  ;  experiment  determination 
of  the  behaviour  of  clay  under  heat,  636  ;  production  of  earthenware,  636  ;  classification  of 
earthenware,  637 ;  dense  clay  ware,  637  ;  porous  clay  ware,  637  ;  hard  porcelain ;  grinding 
and  mixing  the  material,  638  ;  drying  the  mass,  638 ;  kneading  the  dried  mass,  639 ; 
moulding,  639  ;  potter's  wheel,  639  ;  moulding  in  plaster  of  Paris  forms,  639 ;  casting,  640  ; 
preparation  of  porcelain  articles  without  moulds,  640  ;  drying  the  porcelain,  640  ;  glazing, 
640  ;  porcelain  glaze,  640  ;  applying  the  glaze,  641  ;  immersion,  641  ;  dusting,  641  ;  water- 
ing, 641 ;  volatilisation,  641  ;  lustres  and  flowing  colours,  641  ;  capsule  or  sagger,  641 ; 
porcelain  kilns,  641  ;  emptying  the  kiln  and  sorting  the  ware,  642 ;  faulty  ware,  642 ; 
porcelain  painting,  643 ;  ornamenting  the  porcelain,  643 ;  bright  gilding,  643 ;  silvering 
and  platinising,  644 ;  lithophanie,  644 ;  tender  porcelain,  644 ;  French  fritte,  644 ;  English 
fritte,  644 ;  Parian  and  Carrara,  645  ;  stoneware,  645  ;  ovens,  645  ;  lacquered  ware,  647  ; 
fayence,  647  ;  ornamenting  fayence,  648 ;  flowing  colours,  648 ;  lustres,  649  ;  Etruscan 
vases,  649  ;  clay  pipes,  649  ;  water  coolers,  649  ;  common  pottery,  650  ;  burning,  650 ;  brick 
and  tile  making,  650;  terra-cotta,  650;  brick  material,  651  ;  preparation  of  the  clays,  65 1  ; 
"treading,"  651;  the  furnace,  652;  Bock's  channel  furnace,  655;  gas-firing,  655; 
Escherich's  ring-furnace,  655 ;  Mendheim's  modification,  656 ;  kilns,  656 ;  clinkers, 
roofing  and  flooring-tiles,  657 ;  ballast,  657  ;  fire-bricks,  657  ;  crucibles,  659. 

MORTARS,  ETC 659 

Substances  used,  659 ;  gypsum,  660  ;  nature,  660  ;  burning,  66 1  ;  kilns,  or  burning  ovens,  66 1  ; 
grinding,  uses,  662  ;  casts,  hardening,  663  ;  lime,  664  ;  properties,  burning,  664 ;  occasional 
or  periodic  kilns,  665  ;  continuous  kilns,  666;  kilns  for  burning  lime  and  bricks,  667;  pro- 
perties of  lime,  667  ;  slacking,  667  ;  mortar,  668  ;  common,  hardening,  668 ;  hydraulic 
mortar,  668;  Roman,  Portland  cements,  669;  analyses,  671  ;  hardening  hydraulic  cement, 
67 1  ;  hardening  Portland  cements,  672  ;  hydraulic  admixtures,  674 ;  puzzolane  cements, 
674  ;  concrete,  675  ;  mixed  cements,  675. 


SECTION  VI. 

ARTICLES  OF  FOOD  AND  CONSUMPTION. 

STARCH  AND  DEXTRINE 676 

Nature  of  starch,  676 ;  sources,  678 ;  starch  from  potatoes,  678  ;  process  of  manufacture, 
678  ;  drying  potato  starch,  679  ;  preparation  of  wheat  starch,  679  ;  without  fermentation, 
680  ;  constituents  and  uses  of  commercial  starch,  680  ;  rice  and  maize  starch,  68 1 ;  chest- 
nut and  cassava  starch,  68 1  ;  arrowroot,  682  ;  sago,  683;  dextrine,  683;  preparation,  684. 

SUGAR 684 

Grape  sugar,  684  ;  preparation,  686  ;  boiling  starch  meal  with  dilute  sulphuric  acid,  686  ; 
separation  of  sulphuric  acid  from  the  sugar  solution,  687  ;  evaporating  and  drying  sugar 
solution,  687  ;  composition  of  starch  sugar,  687  ;  uses  of  grape  sugar,  687  ;  German  starch 


xx  TABLE   OF  CONTENTS. 

PAIR 

sugar,  688  ;  maltose,  688  ;  cane  sugar,  689  ;  the  sugar-cane,  689  ;  components,  689  ;  pre- 
paring raw  sugar  from,  690  ;  expressing  the  juice,  690  ;  refining  and  boiling,  690  ;  varieties 
of  sugar,  691 ;  molasses,  691 ;  refining  sugar,  691  ;  beet  sugar,  692  ;  species  of  beet,  692  ; 
chemical  constituents,  693  ;  saccharimetry,  693  ;  Stockbridge's  lixiviation  apparatus,  694  ; 
extraction  of  sugar  from  the  root,  694  ;  washing  and  cleansing  the  beets,  695  ;  separating 
the  juice  from  the  root,  695  ;  a  diffusion-battery,  697  ;  composition  and  treatment  of  juice, 
698  ;  de-liming  or  saturating  the  juice  with  carbonic  acid,  699  ;  other  methods,  699  ; 
purifying  with  baryta,  700  ;  filtration  through  animal  charcoal,  700  ;  Fichet's  furnace,  701 ; 
evaporation  pans,  702  ;  vacuum  pans,  703  ;  Derosne's  apparatus,  703  ;  Wellner  and  Jelinek's 
apparatus,  704  ;  separation  of  the  crystals,  706 ;  consumption  sugar,  706 ;  melis,  707  ; 
sugar-candy,  707  ;  beet  treacle,  708  ;  elution,  709  ;  substitution  and  separation,  709  ;  the 
strontia  process,  711 ;  palm,  maple,  and  sorghum  sugar,  712. 

FERMENTATION  ARTS  .        . ,  ,          712 

Fermentation  and  yeast,  712;  vinous  fermentation,  713  ;  yeast,  713;  E.  C.  Hansen's  ex- 
periments with  yeast,  714  ;  Niigeli  and  Low,  bottom  yeast  of  beer,  717  ;  conditions  of 
alcoholic  fermentation,  718  ;  dry  yeast,  718  ;  industries  based  on  alcoholic  fermentation,  719. 

WINE  MAKING 719 

The  vine  and  its  cultivation,  720 ;  vintage,  720 ;  pressing  the  grapes,  720 ;  centrifugal 
machine,  721  ;  chemical  constituents  of  must,  721  ;  the  sugar  of  the  grape,  722  ;  fermenta- 
tion of  the  grape  juice,  723  ;  drawing  off  and  casking  the  wine,  723  ;  constituents  of  wine, 
723  ;  average  composition  of  wine,  724  ;  ebullioscope  of  Tabarie,  725  ;  of  Malligandand  Vidal, 
725  ;  of  Amagat,  726  ;  amount  of  alcohol  in  various  wines,  726  ;  analyses  of  wine-ash,  727  ; 
diseases  of  wine,  727  ;  souring  of  wine,  728  ;  bittering,  728  ;  Pasteuring,  728  ;  hygrother- 
mant  of  Ballo,  729  ;  clearing  or  fining  the  wine,  730 ;  residues  from  the  production  of 
wine,  730  ;  effervescing  wines,  730  ;  improving  wine  musts  and  artificial  wines,  732 ;  use 
of  freezing,  734  ;  cider,  735  ;  appendix,  735. 

BEER  BREWING 735 

Materials,  735  ;  grain,  735 ;  hops,  736  ;  quality  of  the  hops,  737  ;  substitutes  for  hops,  737  ; 
malting,  738  ;  softening  or  soaking  the  grain,  738 ;  germination  of  softened  grain,  739 ; 
drying  the  germinated  grain,  739 ;  pneumatic  malting,  740 ;  Leicht's  malt  kiln,  741 ; 
nitrogen  in  barleys  and  malt,  743  ;  production  of  the  wort,  744;  preparation,  744  ;  bruising 
the  malt.  745  ;  mashing,  745  ;  decoction  and  infusion  method,  745  ;  thick  mash  boiling, 
746  ;  Augsburg  method,  747  ;  infusion  method,  747  ;  extractives  of  the  wort,  748  ;  boiling 
the  wort,  748  ;  adding  the  hops,  750;  cooling  the  wort,  751  ;  fermentation  of  the  beer- 
wort,  753  ;  sedimentary  fermentation,  754  ;  after-fermentation  in  the  casks,  755  ;  surface 
fermentation,  756  ;  steam  brewing,  757  ;  constituents  of  beer,  757  ;  beer  testing,  758  ; 
Balling's  saccharometrical  beer  test,  759. 

THE  MANUFACTURE  OP  SPIRITS 760 

Properties  of  alcohol,  760 ;  raw  materials,  761  ;  saccharification,  762  ;  mashing  process, 
762 ;  Bohm's  apparatus,  763  ;  preparation  of  a  vinous  mash,  764  ;  from  cereals,  764 ; 
spirits  from  sugar  waste,  766  ;  from  wine  and  lees,  767 ;  fermentation,  766  ;  distillation, 
767;  apparatus,  768  ;  Pistorius'  apparatus,  768  ;  Gall's,  770;  Schwarz's,  771 ;  Siemens',  772  ; 
continuous  distilling  apparatus,  773 ;  K.  Ilge's  apparatus,  775  ;  purification  of  the  crude 
spirit,  779  ;  yield  of  alcohol,  780. 

FLOUR  AND  BREAD 781 

Modes  of  bread  making,  781 ;  details,  781 ;  mixing  the  dough,  782  ;  kneading,  782  ;  baking, 
783  ;  substitutes  for  yeast,  784  ;  yield  and  composition  of  bread,  785 ;  impurities  and 
adulterations,  785. 

MILK,  BUTTER,  AND  CHEESE 786 

Milk,  786  ;  whey,  787  ;  lactose,  787  ;  uses  of  milk,  787  ;  condensed  milk,  788  ;  kefyr,  788  ; 
koumiss,  788  ;  butter,  788  ;  chemical  nature  of  butter,  789  ;  composition  of  butter  fats, 
789  ;  artificial  butter,  789  ;  margarine  and  oleomargarine,  789  ;  cheese,  790 ;  composition, 
791  ;  Payen's  researches,  791  ;  Lindt's,  791  ;  E.  Hornig's  analyses,  792. 

MEAT 792 

Constituents  of  meat,  792  ;  cooking,  793  ;  broth,  793  ;  boiling  meat,  794 ;  preservation  of 
meat,  794  ;  by  withdrawal  of  water,  795  ;  salting,  795  ;  Liebig's  researches,  795  ;  smoking 
or  curing  meat,  796. 

NUTRITION .^  797 

Effect  of  various  kinds  of  diet,  797. 


TABLE   OF  CONTENTS.  XT* 

SECTION   VII. 
CHEMICAL  TECHNOLOGY  OF  FIBRES. 

PAGK 

WOOL 798 

Origin  and  properties  of  wool,  798  ;  varieties,  801  ;  cashmere,  vicuna,  alpaca,  mohair,  801  ; 

chemical  composition,  80 1  ;  analysis  of  various  kinds  of  merino,  802  ;  suint,  802  ;  artificial 

wool,  802  ;  shoddy,  mungo,  803. 
BILK 803 

Production,  803 ;  sericiculture — varieties  of  silk  worms,  803  ;  rearing  and  culture,  804  ; 

chemical  composition  of  silk,  804  ;  manipulation  of  the  silk,  805  ;  sorting  the  cocoons,  805  ; 

winding  the  silk,  805  ;   throwing,  805  ;  testing,  806 ;  boiling  the  gum  out  of  silk,  806  ; 

means  of  distinguishing  silk  from  wool  and  from  vegetable  fibres,  807. 
VEGETABLE  FIBRES 808 

Flax,  808  ;   hot-water  cleansing,  809  ;   retted  flax,  809  ;   beating  or  batting  the  flax,  809  ; 

combing,  809  ;  tow,  809  ;  spinning,  809  ;  weaving  linen  threads,  810  ;  linen,  810;  hemp,  810  ; 

stalk  fibre,  810  ;  Chinese  grass,  810  ;  the  great  nettle,  811  ;   ramie  hemp,  rhea  grass,  jute, 

Bombay  hemp,  sun  hemp,  8n  ;   leaf  fibre,  811  ;   New  Zealand  flaxes,  8n  ;   aloe,  Manilla, 

ananas,  pikaba   hemp,  812;   cocoa-nut  fibre,  812;   cotton,  812;   species  of  cotton,  813; 

substitutes,  813  ;   detecting  cotton  in  linen  fibres,  813;   Kindt  and  Lehnert's  tests,  813; 

Stockhardt's  test,  814 ;  O.  Zimmermann's  test,  814  ;   separation  of  animal  and  vegetable 

fibres  by  singeing,  814  ;  adulteration  of  cotton  fabrics,  815. 
BLEACHING ...  815 

Grass  bleach,  815  ;  chlorine,  815;  various  methods  of  application,  816;  Lunge,  removing 

last  traces  of  bleaching  agents,  816  ;  Moyret's  method,  817  ;  Lauber's  method,  817  ;  cotton 

bleaching,  817;    H.  Koechlin's  method,  818  ;    J.  Thompson's  method,  818  ;    continuous 

bleaching  machine,  818;   Mather-Thompson  process,  819;   linen  bleaching,  820;   Kolb's 

method,  820  ;  jute  bleaching  by  Cross,  820  ;  silk  bleaching,  820  ;  wool  bleaching,  820. 

DYEING  AND  TISSUE-FEINTING 821 

Removing  the  solvent,  821  ;  oxidation,  821 ;  double  decomposition,  821  ;  mordants,  821  ; 
turkey -red  oil,  822  ;  alumina  mordants,  822  ;  aluminium  acetates  and  sulphacetates,  822  ; 

ageing,  822  ;  "  dunging,"  823  ;  iron  mordants,  823 ;  nickel,  824;  chrome,  824;  tin,  825; 
manganese,  825  ;  antimony,  825  ;  tannin,  825  ;  apparatus,  826  ;  colour-pans  for  laboratories, 
826 ;  machine  for  dyeing  piece-goods  and  yarns,  828  ;  Sulzer's  machine,  829 ;  dyeing 
woollens,  829  ;  blue  dyeing,  829  ;  indigo  blue,  830  ;  blue  vats,  830 ;  Saxony  blue,  832  ;  recovery 
of  indigo  from  rags,  832  ;  Berlin  blue,  royal  blue,  832  ;  logwood  and  copperas  blues,  833 ; 
dyeing  yellows,  833  ;'red  dyeing,  833  ;  green  dyeing,  834  ;  black  dyeing,  834 ;  silk  dyeing,  835; 
blue  dyeing,  836  ;  yellow  dyes,  837  ;  green  dyes,  837  ;  cotton  dyeing,  837  ;  Baden  Aniline 
Company's  process,  837  ;  C.  and  H.  Koechlin's  processes,  838  ;  turkey  red,  838  ;  aniline  black, 
839  ;  dyeing  linen,  839  ;  tissue-printing,  839  ;  thickenings,  840  ;  special  care  of  colour- 
mixer,  841  ;  madder  style,  842  ;  madder  printing,  843  ;  Witz's  method,  843  ;  "  padding 
on  mordants,"  843  ;  machine  used,  843  ;  printing  with  resists,  844 ;  fatty  resists,  844  ; 
white  resists,  844 ;  coloured  resists,  844  ;  lapis  style,  844  ;  discharges,  845 ;  China-blue 
style,  845  ;  pencil  blue,  845  ;  discharge  style,  846  ;  printing  aniline  blacks  on  dyed  cottons, 
846  ;  steam  colours,  847  ;  Schlieper  and  Baum  process  for  indigo  printing,  847  ;  Goppels- 
roder,  proposed  use  of  electrolysis,  848  ;  "  coppering,"  849 ;  Barlow's  process,  849 ;  topical 
or  application  colours,  849 ;  topical  black,  849  ;  use  of  ultramarine  in  printing,  849 ;  printing 
with  gold  and  silver,  849  ;  with  coal-tar  colours,  850 ;  Botsch,  preparation  of  Congo  colours, 
850  ;  finishing,  851  ;  examination  of  dyed  and  printed  textiles,  852  ;  Lenz,  Martin,  Hutamel, 
and  Lepetit,  detecting  colouring  matters  on  fibres,  852-61. 

PAPER  MANUFACTURE 853 

History  of  paper,  853  ;  materials  used,  853 ;  substitute  for  rags,  853 ;  F.  C.  Keller, 
mechanical  wood-stuff,  860  ;  chemical  production  of  cellulose,  862  ;  mineral  additions  to 
rags,  865  ;  manufacture  of  paper  by  hand,  865  ;  cutting  and  cleaning  the  rags,  865  ;  sepa- 
ration of  rags  for  half-stuff  and  whole-stuff,  866  ;  stamp  machine,  866  ;  bleaching  the  pulp, 
866  ;  antichlore,  867  ;  blueing,  867  ;  sizing,  867  ;  hand-made  paper,  867 ;  straining  the 
paper  sheets,  867 ;  pressing,  868  ;  drying,  868  ;  sizing,  868  ;  preparing  the  paper,  868  ; 
different  kinds  of  paper,  869  ;  machine  paper,  869  ;  manufacture,  869  ;  paper-cutting 
machine,  869 :  pasteboard,  870 ;  papier-mache,  870 ;  coloured  paper,  870 ;  graphite  paper, 
871 ;  parchment  paper,  871 ;  Fritsch's  machine,  871. 


xxii  TABLE  OF  CONTENTS. 

SECTION  VIII. 

MISCELLANEOUS  ORGANO-CHEMICAL  ARTS  AND  MANUFACTURES. 

PA&l 

TANNING 873 

Anatomy  of  animal  skin,  873  ;  red  or  bark  tanning,  874 ;  oak  bark,  874  ;  Biichner's  re- 
searches, 875  ;  sumac,  875  ;  dividivi,  875  ;  nut  galls,  876  ;  valonia  nuts,  876 ;  Chinese 
galls,  876  ;  cutch,  876  ;  kino,  877  ;  estimation  of  the  value  of  the  tanning  materials,  877  ; 
the  hides,  878  ;  cleansing,  879  ;  stripping  off  the  hair,  880  ;  swelling  the  hides,  880  ;  the 
tanning,  881  ;  in  bark,  881  ;  in  liquid,  882  ;  quick  tanning,  882  ;  dressing  or  currying  the 
leather,  883  ;  sole  leather,  883  ;  upper  leather,  883  ;  paring,  883  ;  scraping  or  smoothing, 
883  ;  graining,  883  ;  polishing  with  pumice-stone,  883  ;  raising  the  grain  with  pommels  of 
cork,  883  ;  smoothing  with  the  Tawer's  softening  iron,  884  ;  rolling,  884  ;  finishing  off,  884  ; 
greasing,  884  ;  yufts,  jufts,  or  jufti,  Russia  leather,  884  ;  morocco  leather,  885  ;  dressing 
morocco,  885  ;  cordwain,  Cordovan  leather,  885  ;  lacquered  leather,  885  ;  alum  tanning — 
tawing,  886  ;  common  tawing,  886  ;  Hungarian  tawing,  888  ;  glove  leather,  888  ;  Knapp's 
leather,  889  ;  electrical  tanning,  889  ;  oil-tawing  and  wash-leather  process,  890 ;  parch- 
ment, 891  ;  velin,  891  ;  shagreen,  891. 

GLUE,  SIZE,  GELATINE 892 

General  observations,  892  ;  leather  glue,  893  ;  treating  with  lime,  893  ;  boiling  the  mate- 
rials, 894 ;  fractionated  boiling,  894  ;  moulding,  895  ;  drying  the  glue,  895  ;  bone  glue, 
896 ;  boiling  out  the  grease,  896 ;  treating  the  bones  with  hydrochloric  acid,  896  ;  con- 
version of  the  organic  matter  into  glue,  896  ;  liquid  glue,  897  ;  tests  of  quality  of  glue, 
897. 

SIZES 898 

Isinglass,  fish  glue,  898  ;  substitutes  for  glue,  899. 

BONES 899 

Bone-black,  900  ;  properties  of  bone-black,  901  ;  testing  bone-black,  901  ;  revivification  of 
charcoal,  902 ;  substitutes  for  bone-black,  902. 

FATS 903 

Berthelot's  series,  903  ;  goose-grease,  904  ;  fish  oil,  904  ;  important  non-drying  oils,  904 
palm-oil,  904  ;  bassia-oil,  904  ;  olive  oil,  905  ;  rape  and  colza  oil,  906  ;  beech,  906  ;  sesame, 
906 ;  earth-nut,  906 ;  chief  drying  oils,  906  ;  hemp,  906  ;  nut,  906  ;  cotton,  906  ;  waxes, 

906  ;  beeswax,   906 ;  white,  906 ;  Chinese,  906 ;  andaquies  wax,   906  ;  vegetable  waxes, 

907  ;  Japan,  907 ;  carnauba  wax,  907 ;  palm,  907  ;  myrtle  wax,  907  ;  ucuhuba  wax,  907 ; 
lubricants,  907  ;  to  ascertain  the  fluidity  of  an  oil,  908  ;  varnishes,  908  ;  linseed-oil  var- 
nishes, 908  ;  for  paper-hangings,  909  ;  printing  ink,  909  ;  fat  varnishes,  909  ;  spirit  varnish, 
909  ;  lacquers,  910  ;  turpentine  oil  varnishes,  910 ;  polishing  the  dried  varnish,  910 ;  Pet- 
tenkofer's  process  for  restoring  pictures,  910  ;  G.  J.  Mulder's  researches,  911  ;  linseed-oil 
varnish  cement,  911  ;  cement  for  steam  pipes,  &c.,  911  ;  iron-putty,  911. 

SOAP 911 

Raw  materials,  911  ;  theory  of  saponifi cation,  911  ;  Chevreul's  researches,  911 ;  Berthelot's 
researches,  912  ;  soft  soaps,  912  ;  hard  soap,  912  ;  grain  soap,  912  ;  smooth,  912  ;  filled, 

912  ;  chief  varieties  of  soap,   913  ;  Mege-Mouries'   process,  913  ;  F.  Knapp's  researches, 

913  ;  German  curd  soap,  914  ;  Dr.  A.  C.  Oudemans'  researches,  914  ;  olive-oil  soap,  914  ; 
mottled  soap,  914;  Marseilles  mottled  soap,  914  ;  oleic  acid  soap,  915;;  Pitman's  process,  915  ; 
Morfit's  arrangement,  915  ;  resin-tallow  soaps,  915  ;  German  palm-oil  soap,  915  ;  cocoa-nut 
oil  soap,  915  ;  soft  soap,  916  ;  various  other  soaps,  917  ;  toilet  soaps,  917  ;  modes  of  pre- 
paring, 918  ;  Windsor  soap,  917  ;  rose,  917  ;  shaving,  917  ;  lather,  917  ;  palm  or  olive  oil, 
917  ;  transparent  soap,  918  ;  glycerine  soap,  918  ;  uses  of  soap,  918  ;  tests,  918  ;  Dr.  Leeds' 
method  for  the  examination  of  soap,  918;  insoluble  soaps,  918;  calcium,  magnesium, 
aluminium  soap,  918  ;  manganese,  zinc,  mercury,  silver,  gold,  platinum  soaps,  919  ;  washing 
powders,  extracts  of  soap,  soap  powders,  &c.,  919  ;  adulteration  of  soap,  919. 

STEARINE  AND  GLYCEEINE 921 

Saponification  with  caustic  lime,  921  ;  A.  Kind's  method,  922  ;  Messener's  apparatus,  922  ; 
Petit's  apparatus,  922 ;  saponification  with  a  reduced  proportion  of  lime  and  the  use  of  high 


TABLE   OF  CONTENTS.  xxiii 

MM 

pressure,  924  ;  the  Milly  process,  924  ;  Leon  Droux's  apparatus,  924  ;  saponification  with 
sulphuric  acid  and  subsequent  distillation  by  means  of  steam,  926 ;  with  water  and  high 
pressure,  929  ;  Tilghman's  apparatus,  929 ;  manufacture  of  fatty  acids  by  means  of  super- 
heated steam  and  subsequent  distillation,  930  ;  process  used  by  Price's  Candle  Company, 
Limited,  930;  Heckel's  apparatus,  931  ;  Korschelt's  researches,  931  ;  Bock's  process,  932  ; 
conversion  of  oleic  acid  into  palmitic  acid,  932  ;  glycerine,  933  ;  preparation,  933  ;  distil- 
lation, 934  ;  freezing  observed  by  W.  Crookes,  Sarg,  and  Woehler,  934  ;  applications,  934 ; 
"  scheelising,"  935. 

ESSENTIAL  OILS  AND  KESINS .  935 

Preparation,  935  ;  by  pressure,  935  ;  extraction,  936  ;  properties  and  uses,  936  ;  perfumery, 
936  ;  artificial  perfumes,  936  ;  preparation  of  cordials,  936  ;  Mxirile's  apparatus  for  the 
extraction  of  ethereal  oils,  938  ;  resins,  938  ;  sealing  wax,  938 ;  asphalte,  939 ;  caoutchouc, 
939;  solvents  of  caoutchouc,  940 ;  various  sorts  of,  940;  preparation,  940;  "Para,"  941: 
preparation  and  use  of  india-rubber,  941  ;  vulcanised  caoutchouc,  941 ;  Goodyear's  process, 
942 ;  gutta-percha,  942  ;  solvents  of,  943  ;  uses,  943  ;  mixture  of  gutta-percha  and  caout- 
chouc, 944 ;  balata,  944  ;  celluloid,  944. 

PBESERVATION  OF  WOOD    ..." 944 

Durability  of  wood,  944 ;  attack  of  insects,  945  ;  preservation  of  wood,  945  ;  by  drying, 
946  ;  elimination  of  the  constituents  of  the  sap,  946 ;  air  drains,  946  ;  chemical  alteration 
of  the  constituents  of  the  sap,  947  ;  danger  of  kyanised  wood,  947  ;  Burnett's  fluid,  947 ; 
Bethell's  method,  948  ;  Payne's  method,  948  ;  mineralising  wood,  948  ;  Boucherie's  method 
of  impregnation,  948. 


APPENDIX. 

USEFUL  TABLES. 

THEKMOMETEIC  SCALES 949 

To  convert  degrees  Centigrade  into  degrees  Fahrenheit,  949. 

HYDROMETER  TABLES 949 

For  converting  Twaddell  into  direct  specific  gravity,  949  ;  for  converting  direct  specific 
gravity  into  Twaddell,  949  ;  conversion  of  the  scale  of  Baume  into  degrees  Tw.,  949  ;  scales 
for  liquids  lighter  than  water,  950  ;  Gay-Lussac's  alcoholometer,  951 ;  comparison  of  metric 
system  with  English  weights  and  measures,  952. 

MEASURES  OP  CAPACITY 952 

MEASURES  OF  LENGTH 952 


SECTION    I. 
TECHNOLOGY     OF     FUEL. 


1.  FUEL  AND  ITS  TREATMENT. 

UNDER  fuel  we  understand  those  organic  substances  which,  if  suitably  heated, 
combine  with  the  oxygen  of  the  atmosphere,  evolving  light  and  heat,  and  forming 
carbon  dioxide  and  water.*  The  combustibles  chiefly  used  for  generating  heat — 
wood,  peat,  lignite,  and  coal  (which  will  be  considered  separately  from  the  fatty 
matters  and  mineral  oils,  used  principally  for  the  production  of  light) — consist  essentially 
of  cellulose,  C6H10O5,  and  are  derived  from  it  as  residues  richer  in  carbon,  after  car- 
bonic acid,  water,  and  methane  have  been  split  off,  as  is  shown  in  the  following  table, 
calculated  for  average  specimens  free  from  moisture  and  ash  : — 


Carbon 
per  cent. 

Hydrogen 
per  cent. 

Oxypen 
(+K) 

per  cent. 

Heat  Value 
in  Thermic 
Units.t 

Wood      . 

49 

6 

45 

4IOO 

Peat 

55 

5 

40 

4500 

Lignite  .        . 

66 

5 

29 

5700 

Coal 

S6 

4 

10 

8000 

Anthracite 

94 

3 

3 

820O 

Cellulose  is  formed  from  carbonic  acid  and  water  under  the  action  of  the  sun's 
rays-  6CO,  +  5H20  =  C6H1005  +  6O2, 

whilst  in  the  combustion  of  cellulose — 

C6H1005  H-  60,  m  6CO,  +  SHfO, 

the  same  substances  are  re-constituted  with  the  evolution  of  5150  thermic  units  for 
each  kilo,  of  cellulose.  Exactly  the  same  quantity  of  heat  must  have  been  supplied  by 
the  sun's  rays  for  the  formation  of  i  kilo,  cellulose  from  carbonic  acid  and  water. 
We  therefore  consume,  not  only  the  heat  which  is  now  being  yielded  by  the  sun,  but 
the  solar  heat  which  has  been  stored  up  for  thousands  of  years  in  vegetable  residues 
(lignite,  coal,  &c.), — a  supply  of  power,  heat,  and  light  which  is,  without  doubt,  daily 
decreasing,  and  must  gradually  become  exhausted. 

This  should  be  a  serious  warning  not  to  waste  fuel,  as  is  now  frequently  done, 
or  at  any  rate  to  attend  to  its  thorough  utilisation,  so  long  as  we  have  no  other 
means  of  producing  work,  heat,  and  light  in  sufficient  quantity.  The  application  of 
water-power  for  the  production  of  electricity  is  only  a  slight  attempt  in  this 
direction. 

The   importance,  or  rather,  so   far,  the  necessity  of  fuel  for  the  whole  of  our 

*  This  definition  excludes  chlorine  in  hydrogen,  &c.,  as  also  sulphur,  phosphorus,  and  the 
metals. 

t  A  thermic  unit  is  that  quantity  of  heat  which  raises  i  kilo,  water  from  o°  to  1°.  The 
mechanical  equivalent  of  heat  =  425  kilogrammetres. 


'.'V         V  :  CHEMICAL  TECHNOLOGY.  [SECT,  i, 

y/an^'iD^oai1  iatit-udes  fctvetiior  human  life,  justifies  a  more  thorough  attention 
to  the  utilisation  of  fuel'  than  it  has  hitherto  generally  received. 

THERMOMETRY. 

History.  —  The  first  thermometer  is  said  to  have  been  constructed  by  Galileo  in 
1556,  but  this  is  disputed,  and  the  invention  is  currently  ascribed  to  C.  Drebble  in 
1638.  It  consisted  of  a  globe  with  a  tube  welded  on,  and  dipping  with  its  open  end 
into  a  vessel  containing  a  dilute  solution  of  copper  nitrate.  Becher  (1680)  and 
others  improved  this  air  thermometer  by  taking  the  pressure  of  the  external  air  into 
account.  The  first  spirit  thermometer  was  made  about  1640  by  Moriani,  for  the 
Academy  of  Florence.  Reaumur  (1730)  also  used  spirit  ;  Neston  (1701),  linseed  oil  ; 
and  Fahrenheit  of  Dantsic  (1709)  first  used  mercury.  The  first  metallic  thermometer 
was  constructed  by  Mortimer  in  1746.  Renaldini  (1694)  introduced  the  use  of  ice 
and  of  boiling  water  for  ascertaining  the  fixed  points. 

As  Fahrenheit's  thermometer  is  still  almost  exclusively  used  in  Britain  and  North 
America  and  elsewhere,  in  addition  to  the  scale  of  Celsius  (Centigrade),  and  that  of 
Reaumur  (extensively  used  in  the  fermentation  industries),  it  may  not  be  superfluous  to 
remark  that  these  scales  may  be  converted  into  each  other  as  follows  :  — 


F.  =  9/4R.  +  32  -  V,C.  +  32; 
R.  -  V.  (F.  -  32);  0.  -  •/.  (F.  -  32)  = 


B. 


Fahren- 
heit. 

Celsius. 

Reaumur 
(de  Luc). 

Celsius. 

Reaumur 
(de  Luc). 

Fahrenheit. 

Re'aumur 
(de  Luc). 

Celsius. 

Fahrenheit. 

-    20 

-  28-88 

-   23-11 

-    20 

-   l6'0 

-      4-0 

-    2O 

-   25*00 

-    13-00 

-    10 

-  23-33 

-   18-66 

-    IO 

-     8-0 

+    14-0 

-     10 

-     I2-OO 

+      9-50 

O 

-  1777 

-    14-22 

O 

O'O 

32-0 

0 

O'OO 

32-00 

IO 

-    I2'22 

-    977 

+     10 

+    8-0 

50-0 

+     10 

+   12-50 

54-50 

20 

-     6-66 

-    5  '33 

2O 

16-0 

68-0 

20 

25-00 

77-00 

30 

-     I'll 

-    8-00 

30 

24-0 

86-0 

30 

37-50 

99-50 

40 

+    4-44 

+    3'55 

40 

32-0 

104-0 

40 

50-00 

I22'OO 

50 

lO'OO 

8-00 

5° 

40-0 

I22'O 

5° 

62-50 

I44-50 

60 

I5-5S 

12-44 

60 

48-0 

I4O-O 

60 

75-00 

I67-00 

70 

21-11 

16-88 

70 

56-0 

I58-0 

70 

87-50 

189-50 

80 

26-66 

21-33 

80 

64-0 

I76-O 

80 

1  00  '00 

212-00 

90 

32-22 

2577 

90 

72-0 

I94-0 

90 

112-50 

234-50 

100 

3777 

30-22 

100 

80-0 

212-0 

IOO 

125-00 

257-00 

2OO 

93  '33 

74-66 

2OO 

160-0 

392-0 

20O 

250-00 

482-00 

Conspectus  of  the  Ordinary  Thermometers. — The  numerous  instruments  devised  for 
measuring  temperatures  depend  on  the  utilisation  of  the  following  phenomena  : — 

1.  Expansion  of  matter,  solid,  liquid,  or  aeriform. 

2.  Alteration  of  the  state  of  aggregation. 

3.  Dissociation ;  optical  and  acoustic  phenomena. 

4.  Electric  manifestations. 

5.  Distribution  of  heat. 

i.  The  expansion  of  metals  has  been  used,  especially  for  the  determination  of  high 
temperatures.*  All  these  metal  thermometers  or  pyrometers  axe  untrustworthy. 

The  most  important  appliances  for  measuring  heat  are  the  mercurial  thermometers. 
For  temperatures  from  250°  to  350°  the  space  above  the  mercury  should  be  filled 
with  nitrogen-gas.  If  this  nitrogen  is  under  increased  pressure  the  thermometers  can 
be  used  up  to  400°  or  even  430°,  and  are  the  most  accurate  and  convenient  instru- 
ments for  measuring  such  temperatures. 

Attention  must  be  given  to  the  variability  of  thermometers  which  is  shown  in 

*  Fischer,  Chemische  Technologic  der  Brennstoffe,  pp.  7  and  313. 


SECT.    I.] 


THERMOMETRY. 


two  directions.  On  the  one  hand,  the  zero-point,  and  consequently  the  entire  scale, 
slowly  rises,  and  on  the  other  the  indications  after  any  exposure  to  a  strong  heat 
experience  a  temporary  depression.  In  these  thermometers  the  transient  influence  of 
subsequent  heatings  is  in  part  marked  by  the  temperature  to  which  the  instruments 
are  submitted  in  their  manufacture.  In  old  thermometers  this  latter  effect  is  weakened. 
Here  there  exists  between  the  rise  and  the  fall  a  relation,  in  as  far  as  the  magnitude  of 
the  latter  may  be  regarded  to  some  extent  as  a  standard  for  the  rise  to  be  subsequently 
expected.  To  a  large  extent  of  this  temporary  fall  there  corresponds  a  large  amount 
of  slow  rise  to  be  expected  in  the  course  of  years.  A  constancy  of  the  indications 
sufficient  for  practical  purposes  can  be  counted  on  only  if  the  temporary  fall  does  not 
exceed  a  certain  limit,  which  for  a  heating  up  to  100°  falls  distinctly  below  o'i°.  The 
magnitude  of  the  fall  depends  essentially  on  the  chemical  nature  of  the  glass.  Ther- 
mometers of  very  fusible  potash-soda  glass  are  subject  to  considerable  variations,  whilst 
pure  potash  glass  or  pure  soda  glass  behaves  more  satisfactorily,  as  it  has  been  shown 
by  R.  Weber  and  H.  F.  Wiebe.*  The  composition  of  three  kinds  of  glass  (Jena 
normal  glass),  made  by  Abbe  and  Schott  of  Jena  for  mercurial  thermometers  with 

an  invariable  zero,  is : — 

i.  ii.  in. 

.    67-50        ...        69-00       ...        52-0 


Si02 

Na.,0 

ZnO 

CaO 

AL.O 

BO, 

K,0 


14-00 
7-00 
7-00 
2-50 

2'OO 


II. 

69-00 
14-00 

7'OO 

7 'oo 

I'OO 

2'OO 


30-0 


9-0 
9-0 


Although  these  thermometers  are  very  decidedly  superior  to  those  previously 
known,  an  occasional  comparison  of  the  zero  (crushed  ice)  and  the  boiling  point  of 
water  should  be  made.  For  the  latter  determination  attention  must  be  paid  to  the 
connection  between  the  boiling-point  of  water  and  the  atmospheric  pressure  : — 


Barometer. 
720  millim. 
73° 
740 

75° 
760 

770 

780 


Boiling-point. 
98-49° 
98-88 
99-26 

99 '63 
ioo-oo 
100-36 
100-73 


Naphthaline  and  benzophenone  are  suitable  for  higher  temperatures.  The  follow- 
ing table  gives  the  boiling-points  of  naphthaline  and  benzophenone  at  various  pressures 
in  millimetres  of  mercury  (reduced  to  o°):  — 


Naphthaline. 

Benzophenone. 

Temp. 

Millimetres. 

Temp. 

Millimetres. 

Temp. 

Millimetres. 

\       Temp. 

Millimetres. 

215-8 

722-05 

217-2 

745'4i 

303-8 

72477 

305-2 

746-24 

2l6'0 

725-34 

217-4 

748-80 

304-0 

727-80 

305-4 

749-36 

2l6'2 

728-45 

217-6 

752-20 

304-2 

730-86 

305-6 

752-47 

216-4 

731'98 

217-8 

750-90 

3°4'4 

733-92 

305-8 

755-60 

216-6 

735-32 

218-0 

759-02 

304-6 

736-98 

306-0 

75874 

216-8 

738-67 

218-2 

762-46 

304-8 

740*06 

306-2 

761-90 

217-0 

742-03 

2I8-4 

765-91 

305-0 

743-14 

308-4 

765-09 

In   determining    the    boiling-point,^  the  direct  action    of   the   vapours   upon   the 

*  Jahresber.  1885,  p.  1234. 

f  Tliermometric  Correction  for  the  Projecting  Thread. — If  in  determination  of  temperature  the 
mercurial  thread  is  not  entirely  exposed  to  the  heat  in  question,  the  instrument  will  not  give  the 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


Fig.  i. 


thermometer  case  is  to  be  avoided  as  far  as  possible,   which  is  effected  by  inserting 

the  thermometer  in  a  narrow  tube  of  very  thin  sheet-metal,  closed  below  (Fig.  i). 

An  enclosure  of  the  entire  lower  part  of  the  thermometer  in  such  a  metal  casing, 
in  contact  with  the  atmosphere  above,  affords  the  advantage 
(especially  in  determinations  of  boiling-points  at  reduced  pres- 
sures that  the  difference  of  the  pressure  existing  within  and 
without  the  thermometer  is  very  much  smaller,  and  that  conse- 
quently a  correction  for  the  influence  of  the  pressure  upon  the 
height  of  the  thermometer  may  be  omitted.  The  compressibility 
of  the  glass  of  the  thermometer  may  be  approximately  ascertained 
by  determining  one  and  the  same  temperature  with  a  thermo- 
meter in  a  perpendicular  and  then  in  a  horizontal  position.  The 
difference  of  the  thermometer  in  these  two  determinations  is 
caused  by  the  pressure  of  the  mercurial  column  in  the  tube  upon 
its  case  when  in  an  upright  position.  This  effect  is  the  greater 
the  longer  the  thermometer,  and  consequently  the  longer  the 
mercurial  column  at  any  given  temperature.  If  the  temperatures 
found  by  a  mercurial  thermometer  are  to  be  calculated  for  an  air 
thermometer,  the  tables  of  Regnault  are  no  longer  available,  since 
different  kinds  of  glass  are  now  in  use. 

Air  thermometers  *  are  very  accurate,  but  not  well  adapted  to 
practical  purposes. 
2.  The  determination  of  high  temperatures  by  the  fusion  of  metals  and  alloys  has 

been  repeatedly  attempted.     Erhardt  and  Schertel  recommend  metal  balls  of  from  100 

to  150  milligrams  of  the  following  composition  : — 


Composition. 

Melting- 
point. 

Composition. 

Melting- 
point. 

Composition. 

Melting- 
point. 

per  cent. 

per  cent. 

per  cent. 

Silver 

954° 

95Au      5?t 

IIOO° 

65Au  35Pt 

1285° 

8oAg  2oAu 

975 

90         10 

1130 

60        40 

1320 

60        40 

995 

85          15 

1160 

55        45 

1350 

40        60 

1020 

80         2O 

1190 

50        50 

1385 

20        So 

1045 

75        25 

I22O 

45        55 

1420 

Gold 

1075 

70        30 

1255 

Platinum 

1775 

The  more  recent  determinations  of  melting-points  by  Violle  are : — 


Ir 
Pt 
Pd 


Cu 
Au 
Ag 


1054° 

1035 

954 


correct  indication.  If  we  call  the  temperature  to  be  determined  T,  the  mean  temperature  of  the 
mercurial  thread,  T,  and  its  length  /,  the  thread,  if  entirely  immersed  in  the  temperature  to  be 
measured,  will  be  longer  in  the  proportion  i  :  i  +  a  (T  -  r)  if  a  denotes  the  co-efficient  of  expansion 
of  the  mercury  in  the  glass.  Instead  of  /  the  length  would  be  I  +  I  a  (T-  r),  or  the  number  of  degrees 
which  go  to  the  unit  of  length  being  put  =  i>,  then  in  place  of  v  I  in  thermometer  degrees  the  length 
of  the  thread  would  be  vl  +  vl  a  (  T-  T}  or  the  thermometer,  if  v  I  is  put  =  n,  indicate  n  .  a  (T-  T). 
If,  therefore,  we  read  off  on  the  thermometer  the  temperature  t,  the  real  temperature  of  the  space 

in  question  T  =  t  +  n.a  (T -  T)  or  =  -        — .     The  mean  co-efficient  of  expansion  of  mercury 

between  o°  and  100°  being  assumed  as  0*000181,  and  that  of  glass  o>oooo26,  a  =  0*000155.  The 
mean  temperature  T  of  the  thread  is  generally  determined  by  hanging  a  small  thermometer  near 
the  middle  of  the  thread,  along  with  the  one  whose  indications  are  to  be  corrected,  and  assuming 
the  temperature  of  the  air  read  off  on  the  former  as  the  value  of  T,  On  account  of  the  con- 
ductivity of  the  mercurial  thread,  the  value  of  r  as  thus  determined  is  too  small,  and  the  calcu- 
lated value  of  T  is,  therefore,  too  great.  For  shorter  mercurial  threads  we  insert,  according  to 
Holtzmann,  for  compensating  this  error  only  0*000135  instead  of  a,  for  long  threads  the  value 
of  T  must  be  specially  determined  for  each  thermometer  as  j  ust  given. 
*  F.  Fischer's  Chem.  Technologic  der  Brennstoffe,  pp.  32  and  319. 


SECT. 


THERMOMETRY. 


For  high  temperatures  H.  Seger  recommends  tetrahedra  (normal  cones)  of  mixed 
glazes  composed  of  felspar,  marble,  quartz,  and  Zettlitz  kaolin  according  to  the  following 
formulae : — 


No. 

Chemical  Formula:  o'3K20,o'7CaO,  and 

No. 

Chemical  Formula  :  o^KjjO.o^CaO,  and 

I 

o-2Fe203,o-3Al.,O3,4SiO2 

ii 

r2Al203)i2SiO2 

2 

o  •  i  Fe2O3,o  -4  Al2O3,4Si02 

12 

i'4Al2O3,i4SiO. 

3 

o  -o5Fe203,o  -45  Al.,03,4Si02 

13 

i-6Al.,03,i6SiO; 

4 

o-5Al.,O3,4SiO2 

14 

i-8Al20.,,i8Si<X 

5 

o-5Al203,5Si02 

15 

2-iAl203,2iSi(X 

6 

o-6AL,O3,6Si02 

16 

2-4Al.,O3,24SiO2 

7 

o7ALAj,7SiO, 

17 

27Al."O3,27SiO., 

8 

o-8Al.,O3,8Si02 

18 

3'iAL203,3iSiO; 

9 

o-9AU),,9Si02 

19 

3'5Al,03,35Si02 

10 

i-oAL,Os,ioSiO, 

20 

3-9Al203)39Si02 

Fig.  2. 


The  fusion  of  the  cones  indicates  the  temperatures  between  the  melting-point  of 
90  parts  gold  and  10  parts  of  platinum — i.e.,  about  1145°  UP  to  *ne  mogt  intense  glow 
of  a  porcelain-furnace.  If  we  call  the  range  to  be  measured  600°,  each  cone  represents 
a  rise  of  about  30°.  It  must  be  remembered  that  the  cones  for  the  higher  figures  show 
phenomena  of  fusion  more  and  more  slowly.  This  is  intelligible  if  we  consider  that  at 
higher  temperatures  the  heat  of  the  furnace  rises  more  and  more  slowly  on  account  of 
the  increasing  losses  of  heat.  The  glazes  also  become  more  and  more  refractory,  and  sink 
down  less  readily.  In  setting  up  the  cones  care  must  be  taken  that  they  always  incline 
to  one  and  the  same  side,  the  open  side  of  the  form  on  which  the  number  is  impressed, 
and  which  almost  invariably  comes  upwards.  The 
cones  are  to  be  placed  so  that  the  sinking  of  the  point 
may  be  observed  until  it  touches  the  fire-clay  plate  be- 
neath. The  Royal  Porcelain  Works  at  Berlin  supply 
i  oo  cones  for  45.  6d.  The  cones  act  satisfactorily.* 

3.  The   determinations    of   heat   depending  upon 
dissociation,  optical  and  acoustic  phenomena  seem  to 
have  no  future,  t 

4.  Electric    Thermometers. — The    best    of    these 
devices  is  the  electric  pyrometer  of  C.  W.  Siemens. 
As    the   author    has   satisfied  himself   by  prolonged 
experiments,!  it  is  trustworthy,  but  it  requires  very 
careful  manipulation,  and  is  costly  (about  ^25). 

5.  Diffusion  of  Heat. — Among  instruments  of  this 
kind§  only  the  so-called  calorimeters  are  trustworthy. 
The  author  J[  recommends  the  following  arrangement  as 
satisfactory  : — The  cylinder  of  sheet-copper,  A  (Fig.  2), 
145  mm.  high  and  50  mm.  wide,  is  suspended  in  the 
wooden  case,  B,  which  is  provided  with  a  convenient 
handle.    The  space  between  the  wood  and  the  metal  is 
filled  up  with  asbestos  of  a  long  fibre.     The  apparatus 
is  closed  with  a  thin  plate  of  brass  which  has  a  large 
aperture,  d,  of  20  mm.  diameter,  for  the  stirrer,  c,  and 
for  introducing  the  metal  cylinder,  and  a  smaller  one 
for  the   thermometer,    t.     The   normal  thermometer 
with  a  very  small  bulb  for  mercury,  ranging  from  o° 

to  50°,  is  graduated  in  o-i0,  so  that  it  is  possible  to  estimate  o-oi°.     It  is  protected 
against  injury  from  the  stirrer  by  a  strap,  a,  of  thin  sheet-copper.    The  stirrer  consists  of 

J  Op.  cit.  p.  47. 


*  Jalir&sber.  1887,  p.  30. 
§   Op.  cit.  pp.  54  and  327. 


t  Brennstoffe,  pp.  45  and  326. 
||   Op.  cit.  p.  61. 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


a  round  disc  of  copper  soldered  to  a  stout  copper  wire,  which  is  melted  into  a  glass  rod, 
serving  as  a  handle.  The  copper  vessel  weighs,  e.g.,  35*9  grammes,  and  the  stirrer  with- 
out the  glass  rod  6 '4  grammes ;  hence  the  water- value  of  the  calorimeter  (specific  heat  of 
copper  0-094)  with  the  thermometer  4  grammes.  For  refrigerating  there  are  used  246 
grammes  of  water,  so  that  the  water-value  of  the  calorimeter  when  full  is  250  grammes. 
For  measuring  the  temperatures  the  author  uses  a  platinum  cylinder  weighing  20 
grammes,  or  a  cast-iron  cylinder  of  12  mm.  diameter  and  20  to  22  mm.  in  length,  weigh- 
ing 20  grammes,  and  having  two  perforations.  These  cylinders  are  exposed  to  the  heat, 
which  is  to  be  determined  in  a  small  covered  iron  vessel,  secured  to  an  iron  rod  from 
£  to  i  metre  in  length,  and  fitted  with  a  wooden  handle.  They  are  then  brought  to  the 
calorimeter  and  dropped  in  through  the  aperture  d.  The  metal  cylinder  falls  regularly 
upon  the  plate  of  the  stirrer ;  by  moving  this  up  and  down,  the  heat  is  rapidly  and 
uniformly  distributed  through  the  water,  so  that  within  a  minute  the  thermometer 
shows  the  final  temperature.  Corrections  for  evaporation  of  water  or  difference  of  the 
temperature  of  the  outer  air  are  not  necessary.  The  temperature  sought  for  appears 
from  the  following  table  : — 


T. 

i  kilo.  Water  and  i  kilo.  Metal 
«-*i 

250  grammes  Water  and 
20  grammes  Metal  t  -  <j 

Difference  per  10° 

for  Iron. 

for  Platinum. 

for  Iron. 

for  Platinum. 

for  Iron. 

for  Platinum. 

400° 

47  '4 

13-6 

3-8 

I  '09 

O'I2 

0-03 

5OO 

62-3 

17-4 

5-0 

I  '39 

0-13 

0-03 

600 

78-5 

21  '2 

6-3 

170 

0-14 

o'O3 

700 

96-2 

25-I 

77 

2'OI 

0-15 

0-03 

800 

1  15  '4 

29  '2 

9-2 

2'34 

0-17 

0-03 

900 

136-4 

33  '4 

io-9 

2-67 

0-18 

0-04 

IOOO 

159-2 

377 

127 

3-02 

If  the  thermometer  before  the  introduction  of  the  cylinder  marks  i1°,  and  afterwards 
t°  ;  and  if  the  increase  of  temperature  is  consequently  t  —  tv  the  temperature  sought 
for  is  =T  +  £.  If,  e.g.,  the  water- value  and  the  calorimeter  are  250  grammes  water, 
the  temperature  of  the  water  ^=12*0°,  and  after  the  introduction  of  the  iron  cylinder 
weighing  20  grammes,  2=  20-3°,  then  t— ^  =  8-3°.  The  nearest  value  in  the  table,  77, 
represents  T  =  760°  ;  for  the  remaining  0-6(8-3  —  77)  there  results  0-6:0-15=4,  i.e., 
40°,  to  which  £=  20,  so  that  the  temperature  sought  for  is  760°.  On  using  a  platinum 
cylinder  weighing  20  grammes,  let  the  temperature  ^  be=  15*15,  after  introducing  the 
cylinder  17-98°,  consequently  t  —  ^  =  2-83°  ;  2-67,  according  to  the  table,  correspond  to 
900°;  to  the  residue  2-83  — 2-67  =  0-16  ;  and  0-16  :  0*04  =  4,  i.e.,  40°.  Hence  the  total 
temperature,  958°. 

According  to  more  recent  experiments  by  Pionchon,*  the  specific  heat  of  iron  abovo 
660°  is  very  irregular,  so  that  the  platinum  cylinder  is  preferable. 

DETERMINATION  OF  THE  VALUE  OF  FUELS. 

The  value  of  fuel  employed  for  the  production  of  heat  chiefly  depends  on  the  quan- 
tity of  heat  liberated  on  combustion.  Instead  of  determining  this  value  it  is  often 
customary  to  be  satisfied  with  determining  the  water,  the  ash,  the  sulphur  (especially 
important  in  alkali  works,  smelting  works,  &c.),  the  nitrogen  (especially  for  obtaining- 
ammonia),  further,  the  carbon  and  the  hydrogen,  so  that  the  thermic  value  may  be 
calculated  according  to  the  formula  of  Dulong  (p.  8). 

Sampling. — From  every  load,  or  every  other  load,  barrow,  basket,  &c.,  of  the  coal 
as  delivered,  a  spadeful  is  thrown  into  a  chest  fitted  with  a  cover  ;  the  coal  is  then 
broken  up,  mixed,  and  spread  out  on  a  level  surface  in  a  rectangular  shape,  and  divided 
into  four  parts  by  two  diagonal  cuttings.  Two  of  these  portions  lying  opposite  to  each 

*  Jahresber.  1887,  p.  33. 


SECT,  i.]  DETERMINATION   OF   THE   VALUE   OF   FUELS.  7 

other  are  taken,  away  ;  the  two  remaining  are  again  comminuted  and  mixed  until  there 
remains  a  sample  of  about  2  kilos.,  which  is  put  into  a  closely  stoppered  bottle.  For 
more  careful  investigations  it  is  advisable  to  take  in  the  same  manner  an  average  sample 
of  the  other  half,  and  to  examine  it  separately.  As  a  loss  of  moisture  is  to  be  feared 
during  the  process  of  sampling,  smaller  average  samples  are  placed  from  time  to  time 
in  weighed  test-glasses  with  glass  stoppers  to  serve  for  the  determination  of  water. 

Samples  of  peat  are  taken  in  a  corresponding  manner. 

The  samples  given  in  to  the  laboratory  must  be  completely  pulverised  without 
rejecting  any  portions  which  may  be  hard  to  comminute.  The  determination  of 
moisture  must  not  be  effected  in  open  capsules,  since  many  fuels  become  slowly  oxidised 
if  heated  in  the  air.  For  technical  purposes  about  20  grammes  of  the  sample  are  heated 
for  two  hours  to  105°  or  110°  in  an  air-bath  either  between  two  watch-glasses  or  in  a 
crucible  with  a  well-fitting  cover,  let  cool,  and  weighed.  The  portion  intended  for 
analysis  is,  if  possible,  to  be  allowed  to  dry  in  a  current  of  nitrogen,  or  with  the  utmost 
possible  exclusion  of  air. 

For  the  determination  of  its  ash,  5  grammos  of  the  pulverised  fuel  are  incinerated  in 
a  platinum  capsule.  In  examining  coal,  the  sample  should  first  stand  one  or  two  hours 
in  an  open  capsule  over  a  small  flame,  and  be  heated  in  a  drying  closet  to  about  130°  ; 
the  incineration  is  then  completed  over  a  flame,  which  is  gradually  increased.  Coke 
and  anthracite  should  be  very  finely  powdered. 

To  determine  the  yield  of  coke,  from  i'8  to  2  grammes  of  powdered  coal  are  heated 
over  a  Bunseri  burner  in  a  platinum  crucible  with  a  well-fitting  cover  (the  distance 
between  the  mouth  of  the  burner  and  the  bottom  of  the  crucible  being  3  centimetres) 
until  flame  no  longer  issues  from  under  the  cover.* 

For  determining  the  nitrogen  by  the  Kjeldahl  process,  from  0-5  to  i  gramme  of  the 
coal  or  coke,  pulverised  as  finely  as 

possible  (peat  does  not  require  pul-  **&  3- 

verising),  is  boiled  for  about  three 
hours  with  i  gramme  mercuric  oxide 
and  20  c.c.  of  sulphuric  acid.  When 
cold  there  are  added  120  c.c.  soda- 
lye,  and  i -6  gramme  sodium  sul- 
phide (in  solution),  when  the  am- 
monia is  distilled  off  and  determined 
volumetrically. 

For  determining  carbon  and 
hydrogen,  the  author  uses  a  simple 
combustion-furnace  (Fig.  3).  The 
two  end  plates,  b  and  p,  are  con- 
nected below  with  the  bottom  plate, 

and  joined  to  each  other  above  by  the  two  iron  rods,  u,  against  which  the  tiles,  s, 
vest  above,  whilst  they  stand  below  in  the  grooves  running  along  each  side.  By  this 
means  the  flames  of  the  burners  below,  which  are  screened  from  currents  of  air  by  the 

Fig.  4. 


metal  sheets  placed  on  each  side,  are  compelled  completely  to  enfold  the  combustion 
tube  as  it  lies  in  the  open,  semi-cylindric  channel,  o.     The  combustion-tube  (Fig.  4),  of 

*  See  Fischer,  op.  cit.  p.  113. 


8  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

very  refractory  glass,  open  at  each  end,  contains  between  the  two  asbestos  plugs,  a, 
wrapped  in  very  thin  platinum  foil,  a  layer,  n,  of  granular  copper  oxide.  The  platinum 
boat,  m,  with  the  sample,  is  inserted,  and  the  end  of  the  tube  u  is  connected  with  a 
gas-holder  of  oxygen,  and  the  other  end,  w,  with  the  calcium-chloride  tube,  c. 

When  beginning  a  series  of  experiments,  the  combustion-tube  is  laid  in  the  sheet 
iron  channel,  o,  the  tiles  are  laid  against  the  rods,  u  (Fig.  3),  and  as  the  layer  of  copper 
oxide  is  heated  to  redness  by  the  lamp,  B,  provided  with  three  or  four  flat  burners  (for 
the  sake  of  distinctness  the  sheet-iron  screens  are  here  omitted),  whilst  a  single  Bunsen, 
A,  burner  suffices  for  the  other  half  of  the  tube.  A  current  of  atmospheric  air  is 
drawn  through  for  about  ten  minutes.  The  air  has  passed  first  through  a  flask  with 
potassa-lye,  and  then  through  another  of  undiluted  sulphuric  acid.  The  tube  is  then 
let  cool  in  the  current.  The  stopper,  u,  is  then  removed,  and  the  sample  (about  300 
milligrammes),  previously  dried  at  110°,  is  introduced  in  the  platinum  boat,  the 
stopper  is  again  inserted,  the  calcium-chloride  tube,  c,  is  connected  at  the  other  end, 
and  the  combustion  is  effected  as  usual  in  the  current  of  oxygen. 

The  volatile  sulphur  is  determined  in  a  corresponding  manner,  but  a  larger  sample 
is  used  (0*8  to  i  gramme),  and  the  combustion-tube  contains  asbestos  in  place  of  copper 
oxide.  The  sulphurous  and  sulphuric  acids  formed  are  passed  into  bromiferous  potassa- 
lye  and  into  hydrogen  peroxide,  and  precipitated  as  barium  sulphate. 

If  the  fuel  under  examination  contains  c  per  cent,  of  carbon,  h  per  cent,  of 
hydrogen,  s  per  cent,  of  sulphur,  o  per  cent,  of  oxygen,  and  w  per  cent,  of  water, 
i  kilo,  of  coal  requires  carbon  (2*667  c  +  8  h  +  s—o)  :  100  kilos,  or  (2*667  c  +  8  h  +  s 
—  o)  :  (100  .  1*43)  c.c.  oxygen  or  (2-667  c  +  Sh  +  s-  o)  :  (21.  1*43)  c.c.  of  atmospheric  air 
for  complete  combustion,  i  kilo,  coal  of  medium  composition  consists  of — 

Carbon 80  per  cent. 

Hydrogen 4  »» 

Oxygen 8  „ 

Nitrogen i  „ 

Sulphur 2  „ 

Water  3  }, 

Ash    ......  2  „ 

and  requires,  therefore,  2-667  .  o'8  +  8-004  +  0*02  -  o-o8  or  (2-667  .  80  -i-  8-4  +  2  -  8) : 
100  .  2-393  kilos,  or  1*673  c.c.  oxygen,  or  8  c.c.  of  atmospheric  air. 

The  thermic  value  according  to  Dulong's  formula,  referred  to  liquid  water  at  o°  as 
the  product  of  combustion  = 

8100  c  +  34220  (h  -  -  )  +  2500  s    : 
100  heat-units,  or  referred  for  convenience  to  steam  at  20°  = 

81000  +  28800  (ft j  +  2500  s  —  600  w  I:  i  oo  heat-units. 

Dulong's  formula  gives  approximately  accurate  values  for  wood,  peat,  and  lignite ; 
for  coal  they  are  generally  from  400  to  800  heat -units  too  small.  Accurate  values  are 
obtained  only  by  determining  the  combustion- value  (see  p.  9). 

In  this  determination  of  the  combustion-value  the  author  obtained  the  best  possible 
value  by  passing  the  gases  evolved  in  the  silver  combustion  vessel,  A  (Fig.  5),  down- 
ward through  the  tube  i  into  the  flat  space,  c,  where,  as  the  transverse  section  (see 
accompanying  figure)  shows,  they  are  compelled  in  the  first  place  to  go  to  the  external 
side,  escaping  finally  by  the  flat  tube,  e.  The  combustion-chamber  is  secured  by  the 
three  feet,  f,  to  the  bottom  of  the  copper  refrigerating  vessel,  which  is  strongly 
silvered,  by  corresponding  projections. 

The  glass  pieces,  a  and  b,  are  connected  with  this  silver  apparatus  at  the  water-level 
by  short  caoutchouc  pipes.  The  entrance  tube,  a,  for  the  supply  of  oxygen,  which  has 


SECT,  i.]  DETERMINATION   OF   THE   VALUE   OF   FUELS. 


Fig.  5- 


previously  been  dried,  is  prolonged  by  a  bent  tube  of  sheet-platinum,  which  has  some 
small  apertures  above.  The  platinum  crucible,  £,  can  be  coated  below  with  asbestos 
board  to  prevent  too  rapid  refrigeration,  and  it  is 
covered  with  a  net  of  platinum  wire,  u.  The 
gases  evolved  on  the  combustion  of  the  sample 
of  coal  rise  through  the  platinum  sieve,  warm  the 
oxygen  entering  through  the  tube  a,  mix  with  it 
as  it  enters  through  the  openings  in  the  platinum 
tube,  and  are  compelled  by  the  annular  plate,  v,  to 
pass  again  through  the  hot  wire  net,  u,  along  the 
glowing  side  of  the  crucible,  escaping  downwards 
through  the  aperture,  i.  The  refrigeration  at  the 
bottom,  c,  and  the  tube  g  is  so  complete  that  the 
gases  escape  at  the  tube  e  scarcely  o'i°  higher 
than  the  temperature  of  the  refrigerating  water. 
The  gases  for  the  determination  of  water  and 
carbonic  acid  pass  through  two  calcium-chloride 
tubes,  three  sets  of  potash  bulbs, and  then, for  deter- 
mining the  substances  which  have  not  been  per- 
fectly burned,  through  a  tube  with  ignited  copper 
oxide,  and  again  through  calcium  chloride  and 
soda-lime.  The  residual  oxygen  is  drawn  into  a 
bell  gas-holder,  and  can  be  used  again. 

The  space,  C,  between  the  silvered  copper 
vessel,  £,  and  the  wooden  case,  D,  is  filled  with 
glass-wool.  The  silvered  lid,  n,  consists  of  two 
halves,  one  of  which  has  two  semicircular  openings 
for  the  tubes  a  and  b,  an  aperture  for  the  ther- 
mometer, t,  and  two  for  the  silvered  stirring 
arrangement,  m.  The  thermometer  is  graduated 
in  -^  degrees,  so  that  o-oi°  may  be  accurately 
read  off  by  means  of  a  telescope. 

In  order  to  decrease  as  far  as  possible  the 
communication  of  heat  from  the  stirrer  to  it,  the 
two  last  apertures  in  the  lid  are  fitted  with  small 

ivory  inlets,  and  the  two  wires  which  support  the  disc,  r,  are  screwed  at  top  into  an 
ivory  support,  m.  To  move  the  stirrer  a  silk  cord,  o,  is  passed  over  a  pulley  supported 
by  a  brass  strap  (drawn  here  at  one  side  for  the  sake  of  distinctness),  so  that  during 
an  experiment  the  thermometer  may  be  watched  from  a  short  distance  by  means  of  a 
telescope,  and  the  stirrer  can  be  moved  at  the  same  time.* 

*  In  order  to  find  the  water- value  of  the  apparatus  it  was  completely  put  together  and  filled 
with  1500  grammes  water  at  different  temperatures — e.g.,  temperature  of  the  air,  14 '5°;  of  the 
water,  20 '5° ;  and  of  the  calorimeter — 

Empty I4'64° 

Filled,  after  2  minutes 20-09 


4 

6 

8 

10 

12 
14 


20-02 
I9-97 

I9-93 
I9-90 
I9-86 
19-84 


After  6  minutes  the  temperature  was  equalised,  and  then  decreased  at  each  reading  by  o'O3°. 
In  order  thus  to  heat  the  apparatus  from  14-64°  to  19-97°  the  water  was  cooled  down  from  20-5°  to 


10  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

With  charcoal,  peat,  &c.,  no  combustible  residue  remains  in  the  crucible.  In 
order  to  examine  the  carbonaceous  ash  left  by  coal,  the  lower  part  of  the  crucible  is 
lined  with  thin  sheet-platinum  or  asbestos  paper,  which,  after  the  ignition  is  completed, 
is  introduced  with  its  contents  into  a  combustion-tube,  when  the  combustible  parts  are 
converted  into  carbonic  acid  and  water,  which  are  determined  gravimetrically. 

A  part  of  the  pre-existing  water  as  well  as  that  formed  is  volatilised  in  the  condensa- 
tion-tube, and  a  part  escapes  as  vapour.  According  as  the  combustion-value  is  to  be 
referred  to  liquid  or  aeriform  water,  610  heat-units  must  therefore  be  added  or  de- 
ducted per  gramme  of  water,  which  seems  to  have  been  hitherto  neglected.  After  the 
combustion  is  complete,  the  increase  of  weight  in  the  calcium-chloride  tubes  gives  the 
quantity  of  the  aeriform  water.  The  combustion  chamber  is  now,  without  being  pre- 
viously opened,  again  connected  with  the  calcium-chloride  tubes,  carefully  heated  to 
about  60°,  and  dry  air  is  passed  through,  which  carries  the  watery  vapour  into  the 
calcium-chloride  tubes  for  weighing. 

In  carrying  out  the  experiment  the  calcium -chloride  tubes  and  the  potash  appa- 
ratus are  weighed  and  connected  suitably,  the  coal,  which  must  have  been  dried  at  no0 
in  a  current  of  nitrogen,  is  weighed  off  in  a  covered  crucible,  which,  after  its  lid  has 
been  removed,  is  rapidly  introduced  into  the  dry  combustion  chamber,  A,  the  lid  is 
screwed  up,  set  in  the  calorimeter  vessel,  the  tube  b  is  connected  with  the  absorp- 
tion-tubes and  the  tube  a  with  the  oxygen  tube  ;  1500  grammes  water  are  now  poured 
into  the  calorimeter  vessel,  the  lid  is  put  on,  the  stirrer  is  set  in  action,  and  the  tem- 
perature is  read  off.  In  about  five  minutes  from  i  to  i  J  litre  dry  oxygen  per  minute  is 
allowed  to  enter,  i  to  2  milligrammes  of  heavy  charcoal  splinters,  ignited,  are  thrown 
in  through  the  tube  a,  and  the  thermometer  is  observed  with  the  telescope  whilst  the 
agitator  is  kept  in  action.  If  the  combustion  is  completed  in  four  or  five  minutes  the 
current  of  gas  is  moderated.  In  four  to  five  minutes  more  the  heat  is  equalised,  so 
that  the  final  temperature  may  be  read  off.  The  absorption-tubes  are  weighed,  and 
the  volatilised  water  and  the  residue  of  the  combustion  are  examined  as  indicated. 
Employed  874  milligrammes  coal. 
Obtained  : 

Carbonic  acid,  2490  milligrammes,  representing  carbon  .     679  milligrammes 
Carbonic  oxide,    32          „                .....       14  „ 

Carbon  in  residue 16 


Water,  aeriform,  1  04  milligrammes)       ,     , 
„     liquid,       126           „             f      nyarogen 

769 
•       25-5 

26 '2  „ 

Hence  is  deduced  the  following  composition  of  the  coal,  compared  with  the  ultimate 
analysis : — 

Calorimeter.  Elementary  Analysis. 

Carbon        .         .        .         .     8i'i2  ...  80-91 

Hydrogen  .         .         .         .3-00  ...  3-11 

Nitrogen     ....        —  ...  0-91 

Oxygen      ....        —  ...  7-14 

Sulphur      ....        —  ...  0-51 

Ash 7-21  .,.  7-42 

19-97°  or  20-03°.  The  water- value  is  hence  (0-47  x  1500)  :  5-33  =  132  heat-units.  As  the  mean 
of  five  experiments  conducted  differently  there  was  found  the  figure  124.  The  water-value  of  the 
apparatus  containing  1500  grammes  is  therefore  1624  heat-units.  According  to  the  author's  subse- 
quent experiments,  it  is  preferable  to  fill  the  space  Q  with  eider-down.  If  the  exchange  of  tem- 
perature between  the  apparatus  and  the  external  air  is  not  to  be  brought  into  account,  its 
temperature  is  fixed  so  much  below  that  of  the  air  as  it  is  higher  after  the  experiment. 


SECT,  i.]  DETERMINATION  OF   THE   VALUE   OF   FUELS.  n 

The  temperature  of  the  air  was  14*9°,  that  of  the  calorimeter  i2'8i°;  the  final 
temperature  reached  in  nine  to  ten  minutes,  i6'86°.  Hence  we  have  the  following 
calculation : — 

Taken  up  by  calorimeter,  4/05  x  1624  =  6577  heat-units 
For  CO,  16  x    2-4  =    77} 

„    C,     16  x    8-1  =  130  j-          .        .      227        „ 
„     H,  07  x  28-8  =    20) 
„    higher  specific  heat  of  the  pro- 
ducts of  combustion  20        „ 

6824 

For  the  water  volatilised  we  must  deduct  0-126x610  =  77  heat-units ;  or  per  grammo 
coal,  6747  :  0*874  =  7720  heat-units  referred  to  watery  vapour  at  15°  to  20°,  whilst 
Dulong's  formula  (see  p.  8)  gives  only  (8i'i2  x  8100  +  2'i  x  28800)  :  100=  7175  heat- 
units.  Dulong's  formula  is  consequently  useless  for  mineral  coal.  With  1*4  per  cent, 
water  we  have  (7720  :  roi4)  —  (1*4  x  6)  =  7605  heat-units.  The  mean  of  three  experi- 
ments gave  7630  heat-units. 

The  combustion  of  coal  is  not  quite  perfect,  but,  as  the  products  of  combustion  are 
completely  determined,  and  as  the  combustion- value  of  carbon  monoxide  and  of  hydrogen 
is  accurately  known,  the  inaccuracy  which  may  possibly  arise  is  of  the  less  importance, 
as  any  error  of  moment  is  completely  excluded  by  a  comparison  with  the  elementary 
analysis.  If  it  is  desired  to  burn  also  the  residue  of  the  coal,  this  may  be  effected  by 
directing  upon  the  coal  a  small  hydrogen  flame  through  a  narrow  platinum  tube.  Its 
development  of  heat  can  be  easily  determined  with  accuracy.* 

Wood. — Wood  is  built  up  of  cells  and  vessels  which  consist  of  cellulose,  06H10O5 
(see  section  on  Paper),  and  contain  the  vegetable  juices.  The  latter  contain,  besides 
water  and  the  ingredients  of  ash  (see  Potash),  various  organic  matters  upon  which  the 
composition  of  the  different  woods  depends.  The  proportion  of  water  in  the  different 
woods  is  about — 

White  beech 18*6 

Birch 30-8 

Cluster  oak .         .         .         .         .         .         .         .  347 

Common  oa k 35-4 

White  pine 37'I 

Scotch  fir 397 

Red  beech 397 

Alder 41-6 

Elm 44-5 

Spruce  fir •  .45-2 

Air-dried  wood  contains  12  to  20  per  cent,  of  water.  The  water  diminishes  the 
value  of  the  wood  as  fuel,  not  merely  by  taking  up  the  room  of  combustible  matter,  but 
also  by  requiring  it  to  be  evaporated.  The  following  analyses  show  the  average  compo- 
sition of  wood  : — 

*  The  objection  that  such  small  samples  do  not  represent  the  true  average  is  ill-founded.  In 
an  elementary  analysis  still  smaller  quantities  are  employed.  If,  as  is  commonly  done,  we  take 
from  a  larger  average  sample,  say  of  I  kilo.,  two  specimens  of  i  gramme  each  for  the  calorimetric 
determination  and  for  the  ultimate  analysis,  we  have,  in  the  agreement  of  the  results,  a  much 
better  guarantee  for  accuracy  than  if  we  employed  ico  grammes  for  combustion,  and  were  conse- 
quently unable  to  determine  the  products  of  combustion  and  the  residues  with  accuracy,  whilst 
the  check  of  ultimate  analysis  is  also  wanting. 


12 


CHEMICAL   TECHNOLOGY. 


SECT.    I. 


Kind. 

Composition  dried  at  115°. 

Air-dry. 

C. 

H. 

N. 

o. 

Ash. 

Water. 

Value  of 
i  gramme.* 

per  cent. 

per  cent. 

per  cent. 

per  cent. 

per  cent. 

per  cent. 

heat-units. 

Oak  . 

50-22 

5-99 

0-09 

43-42 

0-28 

I3-30 

3990 

Ash  .                                       !    49-77 

6-26 

0-07 

4337 

0-53 

II-80 

4155 

4 

White  beech                           ,    49*48 

6-17 

O'o6 

4377 

0-52 

1  2  -O2 

4161 

I 

Beech,  old 

49-03 

6-06 

O'll 

44-36 

0-44 

12-95 

4168 

-g  \      „        young 

49-14 

6-16 

0-09 

44-07 

0-54 

I3-95 

4101 

$ 

Birch 

48-88 

6-06 

O'lO 

44-67 

0-29 

II-83 

4207 

Pine. 

50-36 

5-92 

0-05 

43'39 

0-28 

12-17 

4422 

^Spruce 

50-31 

6-20 

0-04 

43-08 

0-37 

1  1  -80 

4485 

Oak  . 

48-94 

5-94 

— 

43-09 

2-03 

N 

•H 

Beech 

46*02 

5-86 

— 

46-94 

1-18 

a  - 

41 

Birch 

48-89 

6-19 

— 

44-93 

0-99 

o 
ffi 

Fir,  old 

49-87 

6-09 

— 

43-4I 

0-63 

'    „    young 

50*62 

6-27 

— 

42-58 

o-53 

If  wood  is  heated  above  150°,  it  is  de-gasified;  there  escape  water,  carbon  dioxide 
and  monoxide,  hydrocarbons,  then  methylic  alcohol,  acetic  acid,  &c.,  whilst  the  residual 
charcoal  becomes  richer  in  carbon  as  the  temperature  rises.  Yiolette  on  heating  wood 
obtained  at — 


No. 

Temperature  of  Carbonising. 

Composition  of  the  Products  (per  Cent.). 

C. 

H. 

O. 

Ash. 

I 

I50°           .... 

47-5I 

6'12 

46-29 

0-18 

2 

2OO                .... 

51-82 

3-99 

43-96 

0-23 

3 

270°              .... 

70-45 

4-64 

24-19 

0-85 

4 

350°              .... 

76-64 

4-14 

18-44 

0-61 

5 

Melting-point  of  antimony 

81-64 

1-96 

I5-24 

•16 

6 

,                        silver    . 

81-97 

2-30 

14-15 

•60 

7 

,                       copper  . 

83-29 

170 

1379 

"22 

8 

gold      . 

88-14 

1-41 

9-26 

•20 

9 

,                        steel 

90-81 

1-58 

6-49 

'IS 

10 

,                        iron 

94'57 

074 

3-84 

•66 

ii 

,                        platinum 

96-52 

0-62 

0-94 

•94 

Samples  i  and  2  are  very  solid  and  imperfectly  burned,  since  decomposition  only 
begins  at  these  temperatures.  No.  3  is  red  charcoal,  which,  if  produced  at  this  tem- 
perature, begins  to  be  friable,  and  is  very  readily  combustible  (300°).  No.  4  and  all 
the  remainder  are  black  charcoal.  Nos.  6— 10  are  very  black,  dense,  solid,  and  difficult 
to  ignite.  No.  1 1  is  so  hard  that  it  cannot  be  easily  broken,  and  if  let  fall  upon  stone 
it  gives  a  metallic  sound.  It  is  very  sparingly  combustible,  so  that  it  only  begins  to 
burn  on  direct  contact  with  a  flame,  and  is  at  once  extinguished  if  taken  out  of  the  fire. 

MANUFACTURE  OF  WOOD  CHARCOAL. 

If  the  products  of  distillation  are  not  to  be  utilised,!  the  charring  is  effected  in 
kilns,  but  otherwise  in  retorts. 

By  a  kiln  we  understand  a  heap  of  large  pieces  of  wood  piled  up  and  covered  with 
earth,  or  with  a  mixture  of  earth  and  charcoal-dust.  The  logs  of  wood  are  laid  either 

*  Not  quite  trustworthy. 

t  The  formation  of  pyroligneous  acid  during  the  dry  distillation  of  wood  is  described  by  Glauber 
in  his  work  Miraculum  Mundi,  in  1658.  The  earliest  large  charcoal-kilns  were  set  in  action  in 
1819  at  Hausach  in  Baden,  but  were  abandoned  shortly  after.  The  increased  value  of  acetic  acid 
and  the  application  of  methylic  alcohol  (discovered  by  Taylor  in  1812  as  accompanying  wood 
vinegar)  for  the  production  of  tar  colours  have  latterly  given  scope  for  a  more  remunerative 
utilisation  of  the  products  of  the  distillation  of  wood. 


SECT,  i.]  MANUFACTURE  OF  CHAKCOAL.  13 

almost  at  right  angles  to  the  axis  of  the  kiln,  or  horizontally,  running  out  radially  from 
the  axis.  In  the  former  case  the  kiln  is  termed  standing,  and  in  the  other,  lying. 

An  Italian  kiln  (Fig.  6)  has  for  an  axis  a  shaft  consisting  of  three  or  four  poles, 
kept  asunder  by  wedges,  n,  and  consists  of  two  or  three  layers  of  wood.  The  conical 
mass  is  rounded  off  by  blocks  laid  horizontally. 

A  Slavonian  kiln  (Fig.  7)  is  distinguished  from  the  last-mentioned  by  its  axis, 

Fig.  6.  Fig.  7. 


which  consists  of  a  post  driven  in,  and  by  the  kindling  passage,  b,  a  channel  leading  to 
the  axis,  by  means  of  which  the  kiln  is  set  burning. 

The  Schwarten  kiln  (Fig.  8),  used  in  Norway,  is  composed  of  irregular  planks. 
Three  of  the  largest  form  the  axial  shaft,  a, 
around  which  combustible  matter  is  heaped, 
and  conically  arranged  heaps  of  the  largest 
wood  loppings  is  superimposed,  interspersed 
with  easily  combustible  matter.  This  heap 
forms  the  nucleus  of  the  kiln,  against 
which  the  planks  are  made  to  lean.  The 
horizontal  heaps  have  the  outward  appear- 
ance of  the  former,  but  the  blocks  of  wood 
are  placed  horizontally  and  radially.  The 
axis  is  either  a  shaft  or  a  post,  with  a  kindling  passage,  and  the  mound,  when  complete, 
is  covered  with  a  layer  of  earth. 

In  charcoal-burning  we  have  to  distinguish  three  stages  or  phases — ( i )  The  sweating ; 
(2)  The  full  combustion  ;  (3)  The  slow  smouldering.  The  kiln  requires  a  larger  supply 
of  air  in  its  interior  when  first  lighted,  in  order  to  effect  the  spreading  of  the  fire,  than 
does  one  which  has  been  burning  for  some  time.  To  this  end  the  foot  of  the  heap  is  at 
first  quite  or  partially  uncovered.  As  the  fire  spreads  there  is  evolved  watery  vapour 
mixed  with  products  of  the  dry  distillation  of  wood,  which  may  form,  by  mingling 
hydrocarbons  with  atmospheric  air,  mixtures  resembling  detonating  gas,  and,  by 
explosion,  may  occasion  a  partial  displacement  of  the  covering,  or  even  a  rupture  of  the 
heap.  By  the  rapid  spread  of  the  fire,  by  the  actual  consumption  of  a  part  of  the 
wood,  and  by  the  decrease  of  volume  due  to  desiccation  and  charring,  there  are  pro- 
duced hollow  spaces,  which  must  be  carefully  filled  up.  As  soon  as  the  vapours  escap- 
ing at  the  foot  of  the  mound  take  a  lighter  colour  comes  the  stage  of  slow  smouldering. 
The  access  of  air  must  be  diminished,  and  for  this  purpose  the  mound  is  covered  up 
wherever  it  had  become  open.  In  about  four  days  the  larger  portion  of  the  wood  is 
charred.  The  fire  must  now  be  managed  so  that  it  spreads  from  the  top  downwards, 
and  from  the  centre  towards  the  circumference.  If  the  smoke  from  the  draught-holes 
becomes  pale  and  blue,  it  is  a  sign  of  readiness,  and  the  air-holes  are  closed.  When  the 
heap  is  thus  ready  in  all  parts,  it  is  left  covered  for  about  twenty-four  hours,  and  let 
cool  whilst  protected  from  the  access  of  air.  The  mound  is  then  dressed  and  extin- 
guished. 

The  carbonisation  of  wood  in  heaps  for  horizontal  works  is  especially  practised  in 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


South  Germany,  Russia,  and  Sweden.  It  differs  from  the  process  just  described,  as  the 
wood  is  gradually  charred  in  portions,  whilst  the  carbonised  pieces  are  at  once  with- 
drawn. The  site  of  the  kiln  is  a  longish  rectangular  figure,  the  front  and  the  back 
being  shorter  than  the  two  sides.  The  heap  slopes  upwards  from  the  front  to  the  back, 
and  the  two  sides  are  both  secured  by  a  row  of  strong  perpendicular  wooden  posts  so 

that    the    two    run 

Jfjcy    q 

parallel.  Figs.  9 
and  10  show  such  a 
heap,  Fig.  9  in  ele- 
vation and  Fig.  10 
in  section.  The  heap 
is  surrounded  with 
the  posts,  a,  and 
with  shingles ;  it  has 
a  covering,  h,  and 
at  the  foot  a  vacant 
passage,  b,  for  kind- 
ling. As  the  fire  advances,  the  charcoal  produced  at  the  front  is  withdrawn,  the 
burner  having  merely  to  see  that  the  fire  does  not  spread  unequally. 

Charcoal-ovens  may  be  regarded  as  permanent  walled  mounds  in  which  the  heat  for 

charring  is  obtained,  exactly 

IO>  as  in  the  common  kilns,  by 

the  combustion  of  a  part  of 
the  wood  with  sparing  access 
of  air.  As  compared  with 
the  kilns  with  movable  cover- 
ings, they  have  the  advan- 
tage that  the  pyroligneous 
acid  and  the  tar  can  be  better 
and  more  completely  sepa- 
rated. On  the  other  hand, 

the  charcoal  obtained  is  said  to  be  inferior  both  in  quality  and  quantity  to  that  from 
the  common  kilns. 

Fig.  1 1  shows  one  of  the  simplest  kilns ; 


Fig.  n. 


the  wood  to  be  charred  is  heaped  up 
either  perpendicularly  or  horizontally. 
The  wood  is  introduced  either  by  the 
aperture,  a,  or  the  door,  b.  The 
kindling  passage  extends  from  the 
door  to  the  middle  of  the  sole — i.e., 
the  floor  of  the  kiln.  Except  a  small 
part  of  the  doorway  and  of  the  open- 
ing, «,  all  apertures  are  bricked  up, 
and  only  re-opened  when  the  charcoal 
is  withdrawn.  After  the  wood  has 
got  on  fire  sufficiently,  b  and  a  are 
closed.  The  small  openings  in  the 
upper  part  of  the  oven  correspond  to 

the  smoke  vents  in  the  common  kilns.  In  the  charcoal-oven  shown  in  Fig.  12  the 
two  doorways,  a  and  b,  serve  for  introducing  the  wood,  and  b  is  also  used  for  taking 
out  the  charcoal.  The  dampers  are  at  c,  and  the  volatile  products  are  carried  off  to  a 
condenser  by  the  iron  pipe,  d.  During  the  process  a  and  b  are  closed.  The  tar  collects 
chiefly  on  the  floor  of  the  oven  and  flows  into  a  suitable  recipient.  Beneath  the  arched 
doorway,  b,  there  is  a  small  aperture  which  serves  as  the  entrance  to  the  kindling  pas- 


SECT.    I.] 


MANUFACTURE   OF   CHARCOAL. 


sage.     In  the  oven  Fig.  13  the  access  of  air  takes  place  through  the  grating,  r.     The 
wood  is  introduced  through  a  and  b,  and  the  volatile  products  escape  by  the  pipe,  g. 

In  charring  wood  in  retorts,  the  wood  enclosed  in  iron  or  earthenware  retorts  is 
heated  from  without,  and  arrangements  are  made  for  the  escape  and  the  complete  utili- 
sation of  the  volatile  products.  In  some  cases  the  production  of  tar,  and  in  others  that 


Fig.  12. 


g.  13- 


Fig.  14. 


of  gas,  is  the  chief  object.  In  the  tube-furnace  the  heating  and  charring  of  the  enclosed 
mass  of  wood  is  effected  from  within  by  means  of  ignited  iron  tubes,  which  traverse  the 
furnace,  being  placed  externally  in  contact  with  a  fire,  and  opening  into  a  chimney. 
Instead  of  passing  the  hot  air  and  the  flame  through  iron  pipes,  the  wood  may  be  at 
once  charred  by  the  heated  air  if  care  be  taken  that  the  air  and  flame  are  deprived  as 
completely  as  possible  of  their  oxygen. 

If  the  chief  object  in  charring  wood  is  to  obtain  tar,  a  process  adopted  in  Russia 
may  be  employed  with  advantage.  According  to  Hessel's  description,  the  stems  and 
roots  of  coniferous  trees,  and  preferably  of  such  as  are  decaying,  are  chosen,  split  into 
pieces,  and  used  for  building  up  the  kiln.  The  site  for  the  kiln  (Fig.  14)  is  funnel- 
shaped,  and  provided  in  its 
middle  with  a  cavity ;  the 
entire  surface  is  coated  with 
clay  and  covered  with  roof- 
ing shingles,  over  which 
the  tar  flows  towards  the 
middle,  from  whence  it 
passes  through  a  pipe  into 
a  vessel  placed  in  a  sub- 
terranean vault.  The  wood 
is  piled  up  in  these  kilns  in 
six  to  eight  layers,  covered 
with  straw  or  dung,  and 
then  with  sand  or  earth. 
When  the  kiln  has  been  arranged,  it  is  kindled  at  forty  or  fifty  openings  around  its 
base,  which  are  afterwards  choked  with  sand  as  soon  as  the  fire  has  spread  upwards 
through  the  entire  heap.  In  about  six  days,  during  which  the  filling  is  kept  up  con- 
tinuously, the  apex  of  the  heap  begins  to  sink  in,  and  there  appears  a  high,  strong 
flame.  In  ten  to  twelve  days  the  removal  of  the  tar  begins,  and  is  continued  every 
morning.  As  this  process  is  simply  a  slow  combustion  from  without  inwards,  which 
is  preceded  by  dry  distillation  and  the  formation  of  tar  in  the  same  direction,  most  of 
the  charcoal  is  consumed  before  the  process  reaches  the  axis  of  the  kiln. 

In  Lower  Austria  (according  to  Thenius)  wood-tar  is  obtained  in  a  similar  manner 
from  such  wood  of  the  black  fir  as  yields  little  or  no  turpentine.     In  Bohemia,  on 


i6 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


the  contrary,  there  are  used  woods  rich  in  resin,  especially  tree-stumps,  which  contain 
many  particles  of  resin.  In  Russia  they  obtain  from  100  parts  of  wood  17-6  parts  of 
tar  and  23-3  of  charcoal. 

Since  1853  the  Swedish  so-called  "  thermo-kettles  "  have  been  used  in  Russia,  and 
deserve  to  be  preferred  in  every  respect  to  kilns  for  charring.  According  to  Hessel, 
such  a  kettle  (Fig.  15)  consists  of  strong  sheet-iron,  and  holds  about  8  cubic  metres.  The 

charge     is     introduced 

X5-  through  the  man-hole, 

g.  The  heat  passes 
from  the  fire,  a,  by 
means  of  the  flues,  b, 
round  the  side  walls. 
To  bring  the  wood 
rapidly  to  100°  a  cur- 
rent of  steam  is  passed 
into  the  kettle  through 
the  pipe  e.  The  tar, 
which  has  already  col- 
lected in  the  kettle, 
runs  through  the  pipe  c 

to  the  store-cask,  £,  whilst  the  tarry  vapours  arrive  through  d  into  the  collector,  B' ; 
what  is  here  condensed  descends  through  h  to  B,  and  what  remains  as  a  vapour  is 
liquefied  in  the  condensing  apparatus,  C.  The  combustible  gases,  which,  however, 
according  to  the  author's  experiments,*  have  only  a  low  heating  value,  are  led  into 
the  fire-box.  Besides  tar,  there  are  obtained,  at  the  beginning  of  the  distillation,  oil 
of  turpentine,  pyroligneous  acid,  and  methylic  alcohol.  The  residual  charcoal  is 
quenched  by  means  of  steam,  and  taken  out  through  the  aperture,  a.  In  Germany  and 
England  horizontal  iron  retorts  are  chiefly  used.f  (See  also  Methylic  Alcohol.) 


Green. 

Summer 
Dry. 

Dried. 

Exsiccated. 

Charred. 

Loss  per  Cent. 

Dried. 

Exsiccated. 

Charred. 

>i 

>^ 

ite 

^3 

>"» 

jr 

>-, 

S 

Kind  of  Wood. 

1 

1 

1 

•5? 

5 

i 

i 

1 

8 

B 

8 

C 

o 

CM 

o 

5 

o 

[T 

_• 

g 

_• 

a 
£ 

_• 

B 

«3 

B 

0 

O 

£ 

o 

«c 

° 

2 

J5 

"3 

1 

3 

E 

£ 

"3 

1 

1 

1 

o 

1 

>3 

c 
o 

| 

1 

c 
O 

0 

1 

1 

s 

"o 
H 

02 

C 

go 

00 

02 

.— 

E 

p.c. 

p.c. 

p.c. 

0 

G 

G 

Oak 

I  -0745 

0-9852 

0*804 

29*1 

0-766 

38-2 

0-387 

767 

_ 

3'i 

6-1 

0'2 

6-813-3 

6-0 

17-0 

35  '2 

Ash 

0-8785 

0-8304 

0771 

19-6 

0-746 

29*1 

0-371 

77*9 

- 

4'? 

8-4 

- 

8-616-5 

7-0 

25*0 

477 

Beech 

I  -0288 

o-8i6o 

0-747 

33  '5 

0-700 

417 

0*319 

82-3 

- 

4'3 

8-4 

- 

7-5  14-4 

6-5 

22  -O 

43*1 

Fir 

0-8734 

0-7828 

0-678 

27-6 

0-662 

377 

0-351 

80-1'  - 

3  '4 

67 

0*2 

6  '9  13  '5 

9-0 

26-5 

50*8 

Elm 

O-9I66 

0-7502 

0-635 

35'5 

o-595 

42*6 

0-284 

81-90-3 

3  '4 

7-0 

0*1 

9-0 

20'0 

41-4 

Yew 

0-9030 

0-7106 

0*696 

24-6 

0-642 

35  '3 

O'202 

76-2 

- 

i  'i 

0'5 

4'3   8-9 

10-5 

8-0 

19-6 

Plane 

O-92IO 

0-7044 

0-637 

33'i 

0-604 

40-3 

0-247 

81*4 

- 

1-7 

3'4 

4'5   8-9 

8-5 

I3-0 

307 

Aspen 

0-8809 

0-6398 

0-5I5 

46-1 

0*463 

54-0 

0-179 

86-3 

0-4 

3-8 

7*8 

0*3 

6-1  I2'I 

7-0 

I5-0 

32-8 

Larch 

07633 

0-61120-607 

27  '3 

o  560 

34'3 

0-238 

77-1 

0*23-4 

6*9 

0-4 

5'2'io-S 

8-5 

10*5 

267 

White  pine 

O-8O4I 

0-58780-529 

37  '3 

0*510 

43-8 

0*214 

81-0 

2  '3 

4*6 

0-4 

5711-4 

IO'O 

I  I'D 

287 

Lime 

0-7690 

0-5810 

0-505 

41-6 

0*484 

477 

0-240 

84-1 

-  57 

ii'i 

0*1 

8-816-9 

8*0 

25-5 

48*9 

Spruce 

0-5266 

0-4931  0-487 

13-1 

o-457 

23*1 

0-193 

73'3 

-  3'i 

6*1 

0-3 

57 

11-3 

9*0 

10-5 

27*1 

The  experiments  were  made  with  cubes  from  the  trunks  of  trees  from  seventy -five 
to  one  hundred  years  old.  For  obtaining  the  wood  in  the  state  named  "  exsiccated  " 
(German  durr)  the  attempt  was  first  made  to  render  the  wood  chemically  dry.  As  this 
was  a  failure,  the  cubes  were  placed,  at  the  beginning  of  May,  in  the  drying-room  of  a 
inanufactory  of  inlaid-wood  articles  at  Sulgenbach,  near  Berne.  The  results  of  this 
*Jahresler.  1880,  p.  417.  t  Ibi'l.  1866,  p.  477;  1871,  p.  659;  1880,  p.  417;  1884^.453;  l%%$  P-435- 


SECT.    I.] 


MANUFACTURE  OF  CHARCOAL. 


exsiccation,  continued  for  two  months  at  gradually  increasing  temperatures,  which  in 
the  last  fortnight  reached  100°,  were  at  once  determined  by  weight  and  measure.  For 
charring,  the  apparatus  of  the  gunpowder  works  at  Worblaufen  was  employed.  The 
cubes  were  carbonised  in  fixed  retorts,  and,  after  complete  charring  and  cooling,  they 
were  at  once  weighed  and  measured. 

The  yield  of  different  kinds  of  wood  on  dry  distillation  has  been  determined  by 
Senff,*  using  a  cast-iron  retort  of  60  centimetres  in  length  and  20  in  diameter.  The 
specimens  of  wood  were  air-dry.  In  order  to  determine  the  yield  on  slow  and  rapid 
distillation,  the  retort  was  either  first  charged  and  closed  and  then  submitted  to  a 
small  fire,  or  the  wood  was  thrust  into  the  ignited  retort,  which  was  then  quickly 
closed  and  strongly  heated.  For  4  to  6  kilos,  of  wood  the  slow  charring  took 
six,  and  the  rapid  process  only  three,  hours.  When  the  distillation  was  complete,  the 
retort  remained  closed  until  quite  cold.  Immediately  on  opening,  the  residual  char- 
coal was  weighed,  and  its  increase  of  weight  was  determined  after  remaining  for 
several  weeks  in  the  air  of  an  ordinary  dwelling-room.  In  the  distillate  the  tar  and 
the  crude  acid  were  separated  by  means  of  parting  funnels,  and  the  quantity  of  gas  was 
calculated  as  loss.  As  the  amount  of  methylic  alcohol  could  not  be  determined,  and 
as  it  generally  corresponds  to  that  of  the  pyroligneous  acid,  the  results  of  experiments 
are  arranged  according  to  the  yield  of  acetic  anhydride  on  slow  charring.  100  kilos, 
of  air-dried  wood  gave  the  values  laid  down  in  the  subjoined  table ;  s  denotes  slow,  and 
r  rapid,  action. 


Kind  of  Wood. 

1 

H 

kilos. 

H 
kilos. 

Crude  Acid. 

« 

•a 
'E 
•a 

>? 

•I 
kilos. 

Charcoal. 

i  Gas  not 
3  Condensed. 

kilos. 

S 
p.c. 

i 

o 
kilos. 

c 
1 

p.c. 

Carpinus  betulus,  L.     Stem      .         .      s 

52-40 

475 

47-65 

13-50 

6-43 

25-37 

6-09 

22-23 

r 

48-52 

5-55 

42-97 

12-18 

5'23 

2047 

10-03 

31-01 

Bhamnus  f  rangula,  L.     Peeled  )        .     a 

52-79 

7-58 

45'2I 

13-38 

6-05 

26-50 

5-09 

20-71 

shoots                                       J        .     r 

4538 

5-I5 

40-23 

11-16 

4'49 

22-53 

6-85 

32-09 

Alnus  glutinosa.     Stem,  peeled         .     s 

6'39 

44-14 

13-08 

577 

3I-56 

6-29 

17-91 

r 

47-76 

7-06 

40-70 

10-14 

4-I3 

21-11 

9-52 

Betula  alba,  L.     Stem      .         .         .     s 

5I-05 

5'46 

45-59 

12-36 

5-63 

29-24 

1-29 

1971 

r 

42-98 

3-24 

39-74 

11-16 

4  "43 

21-46 

7-37 

35-56 

Sorbus  aucuparia,  L.     Stem     .              s 

5^54 

7-43 

44-11 

1  2  '60 

5-56 

27-84 

4-62 

20-62 

r 

46-40 

6-41 

39-99 

10-41 

4-16 

2O  '2O 

872 

33-40 

Fagus  silvatica,  L.     Stem        .         .     s 

5I-65 

5-85 

45-80 

11-37 

5-21 

26-69 

4*61 

21-66 

r 

44-35 

4-90 

39-45 

978 

3-86 

21-90 

8-45 

3375 

Fagus  silvatica,  L.     Branch     .         .      s 

49-89 

4-81 

45-08 

11-40 

5-14 

26-19 

5-95 

23-92 

r 

43-I4 

2-90 

40-24 

10-89 

438 

2I-30 

8-99 

35-56 

Populus  tremula,  L      Stem       .         .     s 

47-44 

6-90 

40-54 

12-57 

5-10 

25-47 

27-09 

r 

46-36 

6-91 

39'45 

11-04 

436 

21-33 

— 

32-31 

Quercus  robur,  L.     Stem  .         .         .     s 

48-15 

370 

44'45 

9-18 

4-08 

34-68 

4-67 

17-17 

r 

45-24 

3"2o 

42-04 

8-19 

3'44 

2773 

6-36 

27-03 

Pinus  larix,  L.     Stem       .        .        .     s 

51-61 

9-30 

42-3I 

6-36 

2-69 

26-74 

8-08 

21-65 

r 

4377 

5-58 

38-19 

5-40)   2-06 

24-06 

872 

32-17 

Pinus  abies,  L.     Stem      .        .              s 

46-92 

5-93 

40-99 

5'6i  |   2-30 

34-30 

4-82 

1878 

r 

46*35 

6-20 

40*15 

4'44J    178 

24-24 

9*63 

29-41 

Pinus  abies,  L.     Branch  .         .              s 

46-34 

8-13 

38-2I 

5-82 

2  '22 

25-55 

9]33 

28-11 

r 

43-85 

5-44 

38-4I 

4-20 

1-61 

23-35 

32-80 

Pinus  abies,  L.     Bark       .         .              s 

40-53 

6-99 

33-54 

3'34 

I  '12 

30-24 

— 

29-23 

r 

37-8o 

5-36 

2-64  j   o'86 

3I-59 

— 

30-61 

The  yield  of  crude  acid,  tar,  and  charcoal  does  not  vary  essentially  in  the  several 
kinds  of  wood,  but  there  is  a  difference  in  the  percentage  of  acid  in  the  crude  acid, 
and  consequently  in  the  yield  of  acetic  anhydride.  The  wood  of  leaf -bearing  trees  is 
more  productive  than  that  of  the  conifers  ;  the  stem  more  than  the  branches,  the  wood 
more  than  the  bark,  and  sound  wood  more  than  that  which  is  decayed.  Rapid  car- 

*  Jahresber.  1885,  p.  433. 

R 


18 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


bonisation  produces  more  gas  at  the  expense  of  the  yield  in  tar  and  charcoal,  the 
distillate  contains  less  acid,  and  the  charcoal  is  more  hygroscopic. 

PEAT. 

Peat  *  is  the  product  of  the  spontaneous  decomposition  (decay)  of  plants,  especially 
swamp-plants,  in  many  cases  mixed  with  sand,  loam,  clay,  lime,  iron  pyrites,  ochres, 
&c.  Beds  of  peat  are  especially  formed  in  places  which  possess  a  sufficient  temperature 
for  the  development  of  the  plants,  and  standing  waters,  which  during  most  of  the  year 
cut  off  the  peat  from  contact  with  the  air.  The  chief  swamp  and  peat  plants  are : 
Eriophorum,  Erica,  Calluna,  Ledum  palustre,  Hypnum,  but  above  all  Sphagnum,  a  plant 
especially  adapted  for  the  production  of  peat,  as  it  never  entirely  dies  down,  but  con- 
tinues growing  and  ramifying  above  whilst  the  lower  parts  are  being  converted  into 
peat. 

The  varying  nature  of  peat  depends  in  part  on  the  different  character  of  the  plants 
from  which  it  is  formed,  on  their  more  or  less  complete  decomposition,  and  on  the 
nature  of  the  earthy  matter  which  becomes  mixed  with  the  vegetable  tissues.  The 
pressure  to  which  the  peat  is  exposed  during  its  formation  has  also  an  influence  on  the 
density  of  the  mass.  According  to  the  difference  of  the  plants  from  which  the  peat  has 
been  produced  we  may  distinguish  (i)  bog-peat,  consisting  principally  of  species  of 
Sphagnum;  (2)  heath-peat,  formed  chiefly  from  the  roots  and  stems  of  Erica  and  Calluna; 
(3)  meadow-peat,  formed  from  grass  and  sedges  ;  (4)  forest-  or  wood-peat,  formed  from 
the  wood  of  trees ;  (5)  sea-peat,  formed  from  sea- weeds. 

With  reference  to  its  extraction,  it  is  distinguished  as  spade-peat,  which  is  at  once 
dug  out  of  the  bogs  in  blocks;  (2)  strained  and  (3)  pressed  peat,  obtained  from  paste- 
like,  swampy  masses,  too  soft  to  admit  of  digging.  If  the  mass  is  too  liquid,  as  is  some- 
times the  case  in  Holland,  in  Westphalia,  and  in  Northern  France,  a  part  of  the  water 
is  strained  off  by  means  of  a  kind  of  net.  To  give  the  peat  more  solidity,  it  is  some- 
times submitted  to  pressure  in  presses  of  a  special  construction. 

The  percentage  of  water  in  recent  peat  is  very  high ;  when  air-dried,  it  still  retains 
15  to  20  per  cent.  The  ash  ranges  from  2  to  20  per  cent.;  that  with  more  mineral 
matter  is  not  worth  getting. 

The  following  analyses  show  the  composition  of  peat : — 


Peat  from 

In  ioo  parts  free  from  Ash 
and  Dry. 

Ash  in  ioo  parts 
Dry  Peat. 

Water  in 
Air-dried  Peat. 

Authority. 

C. 

H. 

N. 

O. 

Kolbermoor    . 
Markobach,  Eheinpfalz 
Steinwenden,       „ 

58-5I 
63-87 
58-70 
60-40 

59-84 
58-69 
60-48 
59-92 
6l'O2 

6-17 
6-46 
7-04 
5-96 
577 
6-97 
6-10 
6-61 
577 

0-88 
i  *6o 
170 

2'2I 

2'54 
1-45 

0-88 
1-26 
0-81 

34-44 
28-07 

32-56 
31-30 
3I-85 
32-88 

32-55 
32-21 
32-40 

4'2I 

2-70 
2'04 
5-58 
973 

I5-5 

8-0 

8-3 
25-6 

Wagner 
Walz 

» 
V.  Regnault 
Vaux 
Kane 

Sullivan 

England 
Philipstown,  light  . 
„            heavy 
Bog  of  Allen,  light  . 
»               heavy 

According  to  Wolff,  two  samples  of  peat-ash  from  the  Mark  Brandenburg  (I.  and 
II.),  and  according  to  R.  Wagner,  an  ash  from  pressed  peat  from  Kolbermoor,  in  Upper 
Bavaria  (III.),  contain — 

*  BIBLIOGRAPHY  :  Torfindmtrie  und  Moorcultur :  B.  and  K.  Birnbaum  ;  Braunschweig,  1880. 
Torfwirthschaft  Suddeutschland's  und  Oesterreich's :  A.  Hausding ;  Berlin,  1878.  Torf,  Natur  und 
Bedeutung :  A.  Vogel ;  Braunschweig,  1859. 


SECT,  i.]  LIGNITE   (BKOWN   COAL,   BOVEY  COAL).  19 

i.  ii.  in. 

Lime 15*25  ...  20-00  ...  18-37 

Alumina 20-50  ...  47 'oo  ...  45  -45 

Ferric  oxide f.        .       5-50  ...  7-59  ...  7-46 

Silica 41-00  ...  13-50  ...  20-17 

Calcium  phosphate  with  gypsum    .         .         .       3-10  ...  2'6o 

Alkali,  phosphoric  acid,  sulphuric  acid,  &c.     .       —  ...  ...  8-55 

Uses  of  Peat. — Peat  as  obtained  in  the  ordinary  manner  is  a  fuel  of  low  value,  as  it 
takes  up  a  large  space  in  proportion  to  its  combustive  efficacy.  This  defect  is  certainly 
reduced  by  pressing  the  peat,  but  this  operation  raises  the  price  to  such  a  degree  that 
it  can  be  used  only  at  or  near  the  place  of  production.  The  peat  charcoal  obtained  by 
carbonising  in  closed  receivers  has  found  only  a  limited  consumption,  as  it  is  too  soft. 
The  dry  distillation  of  peat  for  the  production  of  paraffine  and  solar  oil  can  now  be 
scarcely  remunerative  on  account  of  the  diminished  price  of  these  products.  The  same 
may  be  said  of  the  proposal  to  use  peat  as  a  source  of  ammonia.  Loose  peat  finds  a 
limited  employment  in  the  manufacture  of  pasteboards,  but  it  is  now  extensively  used 
as  litter  for  stables.* 

LIGNITE   (BEOWN   COAL,   BOVEY   COAL). 

Lignite  is  wood  modified  by  decay  in  contact  with  water,  but  the  process  of 
decomposition  is  here  much  more  advanced  than  in  the  case  of  peat.  If  we  look  merely 
to  chemical  and  physical  properties,  it  is  not  possible  to  draw  a  sharp  boundary  between 
coal  and  lignite.  The  geological  and  palseontological  relations  of  a  deposit  supply  data 
for  determining  these  fossil  carbons.  Every  fossil  coal  which  is  more  recent  than  the 
chalk,  and  is  met  with  in  superjacent  formations,  is  termed  lignite ;  every  specimen' 
found  in  formations  older  than  the  chalk  must  be  regarded  as  a  true  coal.  As  the 
proportion  of  nitrogen  in  coal  is  greater  than  that  in  lignite,  the  latter,  if  heated  in  a 
test-tube,  yields  vapours  which  have  an  acid  reaction  from  the  predominance  of  acetic 
acid.  Coal,  if  similarly  treated,  yields  vapours  which  have  a  basic  reaction  from  the 
presence  of  ammonia,  aniline,  lepidine,  &c.  Another  proposed  test  is  to  heat  the 
sample  in  question,  finely  pulverised,  with  potassa-lye.  Coal  leaves  the  liquid  colour- 
less, whilst  lignite  imparts  to  it  a  brown  colour  owing  to  the  formation  of  potassium 
humate  (and  perhaps  also  phlobaphen),  but  we  must  except  the  lignites  of  the  northern 
Alpine  tertiaries  as  soon  as  they  assume  the  character  of  fatty  coals.  According  to  the 
experiments  of  Schinnerer  and  Morawski  (1872)  on  the  action  of  melting  caustic  alkalies 
upon  lignite,  there  is  always  formed,  along  with  other  products,  pyrocatechine,  probably 
formed  by  the  decomposition  of  the  phlobaphenes  present  in  the  lignite,  which,  on 
treatment  with  a  melting  alkali,  form  at  first  protocatechuic  acid  and  subsequently 
pyrocatechine. 

According  to  A.  Bartoli  and  G.  Papasogli,  there  are  formed,  on  heating  lignite 
with  sodium  hypochlorite,  carbonic  acid,  chloroform,  oxalic  and  mellitic  acids.  Coal  is 
attacked  much  less  readily,  and  yields  no  oxalic  acid. 

According  to  the  degree  of  decomposition,  we  distinguish  (i)  the  light-brown 
fibrous  lignite,  of  the  appearance  of  wood,  in  which  portions  of  stems,  branches,  and 
roots  may  be  plainly  recognised  (fossil  or  bituminous  wood).  (2)  Pitch-coal,  shining  black 
pieces  of  a  conchoidal  fracture,  and  without  any  distinctly  perceptible  trace  of  woody 
structure.  If  the  fracture  is  lustrous,  such  specimens  are  known  as  jet  f  or,  in  German, 

*  Peats  containing  iron  pyrites  (sometimes  not  free  from  traces  of  arsenic)  cannot  be  used  for 
litter,  as,  when  subsequently  applied  to  the  land,  they  prove  destructive  to  vegetation.  On  the 
same  account  they  are  unfit  for  use  in  sewage-treatment,  the  construction  of  filters  for  waste 
waters,  &c. — [EDITOR.] 

t  Jet  is  the  English  word  for  gayat,  and  is  derived  from  the  Greek  yaydres,  through  the 
Vienchjayet,jais.  A  peculiarly  fine  deep-black  lignite  is  found  at  Whitby  and  in  the  Cleveland 


20 


CHEMICAL  TECHNOLOGY. 


[SECT. 


gagat.  (3)  The  earthy  lignite,  a  brown  mass  of  decayed  pulveriform  vegetable  matter. 
It  is  used  as  a  pigment,  Cologne  umber.  Lignites  suitable  for  the  production  of  solar 
oil  and  paraffine  are  found  in  Germany  (Weissenfels  and  Zeitz  in  Prussia,  Eschersleben 
and  Saarau  in  Silesia,  Borna  in  Saxony). 

The  average  composition  of  the  lignites  from  different  localities  is : — 


Lignites  from  ; 

ioo  parts  free  from  H2OS  Ash 
contain  : 

ioo  parts 
contain 
Ash. 

Authority. 

C. 

H. 

O  +  N. 

Gangelsberg,  Berlin 
Braunschweig 
Prussian  province,  Saxoi  y 
Kingdom  of  Saxony 
Hessen-Darmstadt  . 
Westerwald     . 
Kegensburg     . 

63-42 
7172 
65-01 
65-93 
57-63 
66-35 
6475 
81-41 
66-04 

4-18 

576 
6  -20 
6-03 
6-06 
S'43 
5-5i 
4'44 
5  '30 

32-20 
22-50 
2877 
28-03 

36-3I 
28-21 
2972 
14-14 
28-65 

8-1 
7-6 
14-2 
ii  -6 
0-6 

9'3 
4-0 

7'3 
3'4 

F.  Fischer 
Varrentrapp 
Bischoff 
Baer 
Liebig 
Casselmann 

Kiihnert 

„        ordinary     
* 

IIO°. 

870°. 

350°. 

450°. 

About  ioooc 

66-34   . 
4-34    •• 

23-38 

O'I2 

..  69-64  .. 
•  4-23  - 
•  I9-25  • 

•  74-92  .. 
•  3-28  .. 
.  14-40  .. 

.      77-98 
2*69 
II'OI 

...      87-11 
o'6i 
...       1-36 

O'4I       . 
5-4I      . 

O'2I  . 
..  6-67  . 

..  0-15  . 
..  7-25  . 

.  .     trace 
..       8-32 

...     10-92 

The  moisture  in  freshly  raised  lignite  amounts  up  to  60  per  cent.,  that  of  air-dried 
samples  to  15  to  20  per  cent.  The  combustion-value  varies  with  their  different  com- 
position so  greatly  that  it  must  be  determined  in  every  special  case  either  by  elementary 
analysis  and  calculation  according  to  Dulong's  formula  (which  only  yields  approximate 
results),  or  by  direct  determination. 

The  applicability  of  lignite  is  greatly  increased  by  drying  and  pressing.  In  order 
to  ascertain  the  behaviour  of  lignite  on  drying,  the  author  dried  at  150°  a  sample 
of  Gangelsberg  lignite  of  the  composition  stated  below  as  containing  60  per  cent,  of 
water.  If  slowly  cooled,  spontaneous  combustion  took  place.  If  air  was  excluded,  the 
sample,  after  being  heated  for  one  hour  each  to  the  following  temperatures,  had  the 
subjoined  composition  : — 

Carbon   . 

Hydrogen 

Oxygen  . 

Nitrogen 

Sulphur  . 

Ash          ... 

If  treated  with  superheated  steam  at  350°,  water-gas  was  formed,  i.e.,  coal  was 
gasified.  Drying  with  superheated  steam  is,  therefore,  not  to  be  recommended. 

Among  the  approved  systems  now  in  use  we  may  distinguish  four — (i)  Fire-plate 
ovens,  in  which  the  drying  is  effected  by  the  products  of  combustion ;  (2)  Steam 
ovens,  which  dry  by  steam  ;  (3)  Hot-air  ovens,  in  which  desiccation  is  effected  by  heated 
air  ;  (4)  Jacobi  ovens,  which  dry  by  means  of  steam  and  hot  air. 

Fire-plate  ovens  were  first  constructed  by  Biebeck,  of  Halle,  early  in  the  year 
1870.  They  are  now  at  action  in  all  the  briquette  factories  of  Biebeck's  mines,  and 
latterly  they  have  been  introduced  in  some  new  factories.  They  generally  contain 
fifteen  to  seventeen  round  cast-iron  plates,  of  4  metres  in  diameter,  arranged  above 
each  other  (Figs.  16  and  17).  An  axle  in  the  middle  of  the  plates  which  revolves 
when  the  oven  is  at  work  supports  over  each  dlate  two  arms  provided  with  sheet-iron 

Hills  in  England,  and  in  the  Departments  Aude  and  Hautes-Alpes.  At  Aude  there  existed  down 
to  the  seventeenth  century  a  guild  of  makers  of  jet  rosaries  (patendtriers  enjais).  The  jet  industry 
existed  formerly  at  Balingen  and  Gmund  in  Wurtemberg.  At  present  Whitby  is  celebrated  for 
the  occurrence  and  the  manufacture  of  jet. 

*  The  lignite  of  Bovey  Heathfield  contains,  according  to  Vaux,  carbon,  67-9,  hydrogen,  5-8, 
oxygen  and  nitrogen,  24-8  per  cent. — [EDITOR.] 


SECT.    I.] 


LIGNITE   (BROWN   COAL,   BOVEY  COAL). 


21 


shovels  fixed  obliquely.     On  turning  this  axle  the  coal  is  moved  and  turned  over  by 
means  of  the  shovels,  and  in  this  manner  conveyed  over  the  plates.     The  shovels  are 
fixed  in  such  a  manner  that  on  one  plate  the  lignite  is  moved  from  within  outwards, 
Fie.  16. 


Fig.  17. 


and  on  the  next  one  from  the  outside  inwards.  The  lignite  falls  through  notches  from 
plate  to  plate  in  such  a  manner  that  in  the  plates  where  the  shovels  work  outwards  the 
fall  is  at  the  margins,  but  in  the  other  plates  near  the  middle.  From  the  last  plate  the 
lignite  falls  through  a  shoot  into  the  store  chest.  The  plates  are  in  an  externally  quad- 
rangular furnace  of  masonry,  with  a  grate  in  front.  The  gases  of  combustion  pass  up 
through  a  channel  into  the  furnace,  passing  down  over  the  plates  and  the  lignite  upon 
them,  and  escape  at  the  chimney  along  with  the  watery  vapour.  These  ovens  are 
especially  adapted  for  lignites  which  contain  little  bitumen  for  which  a  high  temperature 
is  needed.  They  have  the  advantage  that  the  heat  can  be  raised  at  pleasure,  but  also 
the  defect  that  the  proper  drying  of  the  lignite  requires  very  close  attention.  Fires  and 
explosions  are  here  more  common  than  with  other  ovens,  and  hence  they  have  not  been 
generally  adopted.  For  dusty,  adhesive,  and  smelling  lignites  they  cannot  be  used. 

Of  the  steam  ovens,  we  mention  first  the  steam-plate  oven,  similarly  arranged  to  the 
fire-plate  oven,  and  with  the  same  appliance  for  moving  the  lignite.  The  difference 
is  that  the  plates  stand  free  in  an  open  space,  and  that  they  are  hollow  and  con- 
structed of  wrought  iron.  In  drying,  the  interior  of  the  plates  is  swept  by  steam. 
The  plates  are  supported  on  four  hollow  columns,  two  of  which  serve  to  convey  steam 
to  and  from  the  plates.  The  watery  vapour  escapes  by  a  chimney  erected  on  the  oven. 
A  valuable  improvement,  first  devised  by  Rowold,  of  Meuselwitz,*  consists  in  inclosing 
the  oven  in  a  sheet-iron  case,  by  which  the  space  in  which  the  oven  is  set  up  is  kept 
free  from  dust  and  its  working  can  be  conveniently  watched  and  regulated.  The  air 
and  the  temperature  in  the  oven-house  is  thus  prevented  from  becoming  unpleasant  or 
hurtful.  This  oven  is  suitable  for  most  kinds  of  lignite,  though  not  for  those  which 
need  a  very  high  temperature. 

The  tube  drying-oven  of  Schulz,  of  Halle  (Figs.  18  and  19),  is  a  cylinder  in 
which  are  a  great  number  of  smaller  tubes  ;  it  is  therefore  like  a  tubular  boiler.  It  lies 
on  an  incline,  and  revolves  on  its  longitudinal  axle.  The  axle  is  formed  of  two  cones, 
which  are  contracted  towards  the  middle,  where  they  are  connected  together.  They  are 
hollow,  and  their  covering  surfaces  are  perforated.  The  steam  for  drying — exhaust 
steam  from  the  engines — is  let  into  the  upper  cone,  and,  after  having  steamed  through 
the  apertures,  it  escapes  by  the  lower  cone.  On  the  higher  front  of  the  apparatus 
there  is  a  hopper  from  which  the  lignite  falls  into  the  tubes,  gradually  works  through 

*  Jahresber.  1883,  p.  I2II. 


22 


CHEMICAL  TECHNOLOGY. 


[SECT.  i.. 


Fig.  i 8. 


Fig.  19. 


in  consequence  of  the  rotation  and  the  inclined  position,  and  falls  out  at  the  lower 
end.  To  carry  off  the  condensed  steam  there  are  three  escape-pipes  at  the  lower  end. 

This  apparatus  can 
boast  a  simpler 
motory  arrangement 
than  any  other.  It 
has  been  recently  set 
up  at  Ackermann's 
works  at  Bitter f eld, 
and  experience  must 
show  if  it  has  fur- 
ther advantages,  and 
what,  if  any,  defects 
exist.  According  to 
Jacobi's  view,  it  is 
suitable  for  dusty 
lignite  and  such  as  is 
of  a  uniform  grain, 
less  suitable  for  unequal  grains,  and  not  at  all  for  adhesive  and  tumid  kinds. 

The  hot-air  oven  used  in  the  third  system  (Fig.  20)  consists  essentially  of  sheet- 
iron  plates,  arranged  like  a  Venetian  blind,  through  which 
the  lignite  falls  downwards ;  an  arrangement  for  emptying, 
consisting  of  a  metal  sheet  working  up  and  down,  effects 
the  gradual  transit  of  the  coal.  The  air  for  drying  is 
drawn  in  by  ventilators  in  so-called  wind-heaters,  i.e., 
tubular  boilers,  heated  by  the  spare  steam  of  the  engines, 
and  forced  through  the  oven  in  the  opposite  direction  to 
the  lignite. 

At  Frose  there  are  twenty-six  such  ovens,  each  4  metres 
long,  0*5  metre  broad,  and  5  metres  high,  which  furnish, 
every  twenty-four  hours,  material  for  700  hectokilos. 
"  press-coal."  The  temperature  of  the  air  forced  in  is  on 
the  average  60°  to  70°.  The  oven  is  easily  set  in  action, 
and  has  few  moving  parts.  As  defects,  must  be  mentioned 
the  high  temperature  in  the  oven-house,  the  dust,  and  the 

irregular  drying.  For  granular  lignites,  and  such  as  do  not  need  a  strong  heat,  this 
oven  suits  well,  but  not  for  those  which  retain  a  woody  texture  and  swell  up  or  become 
adhesive. 

The  fourth  system,  desiccation  by  means  of  steam  and  hot  air,  has  been  evolved  from 
the  third,  an  endeavour  being  made  to  remove  its  imperfections  by  means  of  steam- 
pipes.  As  appears  from  Fig.  21,  the  Jacobi  oven  is  merely  a  modification  of  the  hot- 
air  oven.  Instead  of  the  internal  wall  of  the  Venetians,  there  are  used  pent- 
angular or  triangular  tubes,  by  which  steam  is  introduced,  to  assist  in  drying  the 
lignite.  In  addition,  hot  air  is  passed  in  by  openings  between  the  tubes.  The 
working  and  the  moving  arrangements  are  the  same  as  in  the  hot-air  oven.  In 
comparison  with  the  latter  it  has  the  advantage  that  the  desiccation  is  more  uniform 
and  that  a  higher  temperature  can.  be  obtained ;  in  other  respects  it  has  the  same 
disadvantages. 

All  the  drying  arrangements  described  have  the  common  grave  fault  that,  in  pro- 
portion to  the  cost  of  installation,  they  effect  far  too  little  work.  The  manufacture  of 
"  press-coal "  (dried  and  compressed  lignite)  will  not  receive  its  full  development,  in- 
volving a  suitable  utilisation  of  the  deposits  of  lignite,  until  this  defect  is  overcome. 


SECT,  i.]  COAL.  23 

An  important  feature  in  drying  lignite  is  the  collecting  space ;  it  is  commonly  under- 
neath the  ovens,  or  sometimes  at  one  side  or  over  the  presses.  Here  the  dried  lignite 
is  collected  and  raised  to  the  presses  by  means  of  spirals  and  elevators.  This  collecting 
space  has  the  important  function  of  equalising  the  differences  of  the  dried  lignite 
arising  from  variations  in  the  proportion  of  moisture,  different  working  of  the  ovens, 
changes  in  the  temperature  of  the  hot  air,  &c.,  since  good,  marketable  press-coals  can 
only  be  produced  with  certainty  from  uniform  materials.  The  lignite  goes  on  drying 
in  this  space.  It  has  been  unjustly  charged  with  being  the  source  of  frequent  fires 
and  explosions,  and  latterly  attempts  have  been  made  to  abolish  it.  According  to 
experiments  at  Frose,  the  subsequent  desiccation  in  this  space  is  essential  for  the 
production  of  good  "  press-coal."  This  is  intelligible,  since  the  lignite  which  comes 
out  of  the  oven  at  46°,  rises  in  the  collecting-room  within  eight  hours  to  70°— 75°, 
the  correct  temperature  for  the  production  of  a  good  article.  The  fires  arise  mostly  in 
the  ovens  and  the  spirals ;  a  fire  in  the  collecting-room  is  never  formidable,  unless 
the  burning  material  is  moved,  when  it  may  become  dangerous  in  consequence  of 
explosions.  Whether  such  explosions  are  due  to  dust  or  gas,  or  both  together,  is  still 
a  matter  of  dispute.  According  to  Johanni's  views  we  have,  in  the  first  place,  an 
explosion  of  dust,  which  may  lead  to  a  gas  explosion  if  it  becomes  extensive. 

Many  kinds  of  lignite,  after  desiccation,  must  be  crushed  and  sifted  to  yield  a  good 
press-coal.  This  ensures  a  uniform  grain,  a  further  compensation  of  the  temperatures 
of  the  single  parts,  and  the  elimination  of  impurities. 

The  limit  of  compression  of  lignite  differs  according  to  its  texture ;  it  is  less  when 
the  material  is  granular  and  greater  when  it  is  dusty.  The  average  is  assumed  at 
45  to  50  per  cent.  The  thickness  of  press-coals  ranges  from  30  to  50  millimetres; 
the  transverse  section  of  the  smaller  is  100  and  of  the  larger  no  square  centimetres. 
The  presses  make  sixty  to  eighty  rotations  per  minute,  and  with  each  one  press-coal  is 
produced.  The  pressure  is  estimated  by  "Wendland  at  1200  to  1500  atmospheres,  and 
a  similar  value  has  been  found  experimentally. 

The  higher  value  of  press-coal  as  compared  with  the  original  lignite  appears  from 
the  following  figures : — 

Frose  Lignite.  Frose  Press-coal. 

Water 50*0  ...  16  per  cent. 

Combustible    .         .        .        .48*5  ...  74        „ 

There  are  at  present  in  action  in  Germany  56  press-coal  works,  with  about  142 
presses,  producing  in  1885  about  8  million  hectokilos.  of  press-coal.  If  we  reckon 
that  4  hectolitres  of  press-coal  are  produced  by  the  consumption  of  i  hectokilo.  of  fuel, 
the  manufacture  of  press-coal — i.e.,  32  million  hectolitres — consumes  about  y^th  of 
the  German  yield  of  lignite,  which  is  300  million  hectolitres.  The  value  of  i  hectokilo. 
of  press-coal  at  the  spot  is  on  the  average  o-8  to  o'9  of  a  shilling,  and  the  cost  of 
manufacture,  material  included,  o'6  to  07  of  a  shilling. 

COAL. 

The  great  importance  of  coal-mining  appears  from  the  following  figures.  The 
quantity  raised  has  increased  almost  threefold  in  twenty  years.  In  1885  Germany 
raised  58,320,398  tons  of  coal,  of  the  value  of  303  million  marks,  and  15,355,117 
tons  of  lignite,  of  the  value  of  40*4  million  marks.  This  continued  increase  should 
prompt  the  public  to  a  more  careful  and  thorough  utilisation  of  this  store  of  heat  and 
power. 

Coal  has  been  formed  from  lycopods,  equisetacese,  ferns,  and  other  cryptogamous 
plants.  It  occurs  in  the  Devonian  up  to  the  forest  clay,  but  especially  in  the  carboni- 
ferous formation.  The  most  important  localities  of  coal  are,  in  Britain,  the  Scottish, 


24  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

the  Newcastle,  the  Lancashire  and  Staffordshire,  the  Welsh,  and  the  Cumberland  beds. 
A  deposit  of  coal  has  recently  been  discovered  in  Sussex,  but  its  extent  is  not  yet 
known.  Altogether  the  coal  formation  occupies  about  TVth  of  the  total  surface  of  the 
British  Islands.  Ireland  is  supposed  to  have  possessed  at  one  time  very  important 
deposits  of  coal,  which  have  been  chiefly  destroyed  by  denudation.  In  France  the  most 
important  coal-beds  are  those  of  the  Loire,  of  Valenciennes,  of  Creusot  and  Blanzy,  of 
Aubin,  and  of  Alais.  In  Belgium  the  carboniferous  districts  take  up  about  -j^th.  of  the 
total  surface.  In  Germany  there  are  the  palatinate  or  Saar  basins ;  those  of  Aachen 
and  Liege,  which  lie  partly  in  Belgium  and  partly  in  Germany ;  the  Westphalian 
field  at  Essen,  Bochum,  and  Ibbenbiiren ;  the  small  beds  of  Merseberg ;  the  Silesian 
deposits,  extending  to  Gallicia  and  Cracow  ;  in  Saxony,  the  beds  of  Zwickau  and 
the  Plauen  valley  ;  and  in  the  Bavarian  province  of  Upper  Franconia,  the  field  of 
Stockheim.  Austria,  with  the  exception  of  Bohemia  and  South  Hungary,  yields 
more  lignite  than  coal.  The  production  of  coal  in  Spain,  Italy,  Russia,  and  Sweden  is 
unimportant. 

In  America  the  coal-fields  of  the  United  States  are  of  vast  importance.  There 
are  three  districts ;  those  of  Pennsylvania,  of  Illinois,  and  the  Western  fields  in 
Iowa,  Nebraska,  and  Texas  occupying  a  total  surface  of  at  least  250,000  square  kilo- 
metres. 

In  British  North  America  there  are  important  coal-fields  in  the  provinces  of  New 
Brunswick  and  Nova  Scotia,  having  areas  of  8000  square  miles.  In  British  Columbia 
there  are  also  extensive  coal  deposits,  the  area  of  which  has  not  been  ascertained.  In 
the  island  of  Trinidad  a  deposit  of  coal  of  superior  quality  occupies  318  square  miles, 
and  is  supposed  to  extend  underneath  the  great  pitch  lake.  The  extent  of  coal  in  the 
South  American  countries  has  still  to  be  determined. 

In  South  Africa  coal  is  abundant.  The  British  province  of  Natal  contains  more 
coal  than  Britain  ever  did,  and  the  fields  extend  into  the  Orange  Free  State. 

India  contains  coal-fields  of  the  area  of  3500  square  miles.  As  to  the  existence  of 
fossil  fuel  in  Burmah  we  are  still  in  doubt.  China  is  probably  richer  in  coal  even  than 
the  United  States.  The  coal  deposits  of  Japan  and  of  Yesso  are  also  of  considerable 
importance.  The  area  occupied  by  the  carboniferous  system  in  Australia  (Queensland 
and  New  South  Wales)  is  estimated  at  240,000  square  miles. 

According  to  the  researches  of  A.  Carnot,*  the  quality  of  coal  depends  not  merely 
on  its  age  and  on  the  circumstances  attending  its  formation,  but  on  the  kind  of  plants 
from  which  it  has  been  formed.  According  to  Stein,  the  behaviour  of  coal  on  coking 
does  not  depend  on  its  elementary  composition. 

Scheurer-Kestner — whose  results  are  confirmed  by  the  author — shows  that  the  com- 
bustion-value of  coal  is  considerably  higher  than  Dulong's  formula  requires. 

His  most  recent  experiments  with  coal  from  Ronchamp  (I.),  from  Altendorf  on 
the  Ruhr  (II.),  and  from  Glamorgan  (III.)  gave — 

Carbon  .  '  . 
Hydrogen  . 
Nitrogen  . 
Sulphur  .  . 

Oxygen  .  . 
Value  .  .  .  9130  heat-units  ...  9121  heat-units  ...  8864  heat-units 

Schwackhofer  obtained  the  following  results  for  the  combustion-value  of  coal : — 

*   Comptes-rendus,  99,  p.  253. 


I. 

II. 

III. 

89*09  per  cent. 

...  89-92  per  cent. 

...  90-27  per  cent. 

5  '09 

...   4-11 

...   4-39 

1-30 

I  -00     „ 

0-69 

i  -03 

I'OO    „ 

...   0-49 

3  '49 

-   3'97 

4-16    „ 

SECT.   I.] 


COAL. 


Name  of  Coal. 

C. 

H. 

0. 

N. 

HS05. 

Ash. 

Sul- 
phur. 

Heat- 
units. 

Wilczek,  Ostrau 

77-06 

4  'So 

1  1  '22 

0-19 

2-91 

4'12 

0-39 

7758 

Erzherzog-Albrecht,  Ostrau 

74-21 

4-19 

9-82 

0-33 

3-22 

8-23 

071 

7443 

Konigshutte,  Prussia 

70-38 

4-07 

1I-85 

0-59 

8-82 

4-29 

0-44 

6920 

Karwiner-Larisch,  Ostrau 

7372 

4-25 

10-39 

0-31 

3-96 

7'37 

0-50 

7368 

Morgenstern,  Prussia 

6i'io 

3-I7 

1  3  "93 

0-41 

9-07 

12-32 

0-57 

5728 

Hermenegilde,  Silesia 

71-02 

4-17 

11-46 

0-18 

2  '6O 

10-57 

0-21 

6992 

Dombrauer,  Polnisch-Ostrau 

74-69 

4-23 

12-42 

0-07 

3^3 

5-56 

0-50 

7280 

Carolinen,  Prussia  . 

61-42 

3-23 

1  3  '64 

0-24 

7-29 

14-18 

078 

5758 

Gliickshilf  I.  ,  Waldenburg 

70-50 

3  '94 

9-28 

0-19 

I  "6O 

14-49 

0-63 

6955 

Jaklowetz,  Silesia    . 

72-59 

3-90 

10-08 

O'2O 

2-40 

10-83 

o-35 

7044 

Waterloo,  Prussia   . 

69-70 

374 

13-60 

0-40 

6-28 

6-28 

0-40 

6571 

Anthracite  occurs  chiefly  in  transition  formations,  especially  between  the  strata  of 
clay-slate  and  of  grey-wacke  and  between  mica-slate  and  the  beds  by  which  it  is  inter- 
sected. It  is  deep  black,  brittle,  of  conchoidal  or  irregular  fracture,  burns  with  a  feebly 
luminous  but  smokeless  flame,  does  not  soften  in  the  fire,  but  often  crackles  and  decre- 
pitates. Jacquelain  obtained  the  following  results  on  the  analysis  of  certain  anthra- 
cites : — 

From                                 C.                            H.  O.  N.  Ash. 

Swansea  .  .  90-58  ...  3-60  ...  3*81  ...  0-29  ...  172 

Sabl6    .  .  .  87-22  ...  2-49  ...  I -08  ...  2-31  ...  6-90 

Vizille  .  .  .  94*09  ...  1-85  ...  I -08  ...  2-85  ...  1-99 

Isere-Dep.  .  .  94-00  ...  1*49  ...  I'o8  ...  0-58  ...  4-00 

Anthracite  owes  its  superiority  to  other  fuel  to  its  cleanliness,  hardness,  and  its 
smokeless  combustion.  In  Swansea  and  in  some  of  the  Eastern  American  States, 
especially  along  the  river  Lehigh  in  Pennsylvania,  it  has  been  used  since  1839  for  the 
reduction  of  iron  ores  in  blast  furnaces.  It  serves  also  in  lime-burning,  brick-burning, 
in  salt  works,  and  as  a  domestic  fuel.  Since  1875  the  attempt  has  been  made  to 
convert  anthracite  into  coke  by  breaking  it  up  previously  along  with  caking  coal  and 
coke. 

Boghead  Coal,  or  Torbane  Hill  mineral,  is  found  near  Bathgate,  at  Rocksoles 
near  Airdrie,  at  Pirnie,  Capeldrea,  Kirkness,  and  Wemyss  in  Fife.  The  Torbane  Hill 
•coal,  famous  for  the  unedifying  litigation  as  to  its  nature,  is  considered  the  most 
valuable  coal  known  for  gas-making.  It  is  amorphous,  with  a  conchoidal  fracture,  and 
contains  impressions  of  the  stems  and  roots  of  Sigillaria.  It  yields  a  coke  of  little 
value,  and  on  dry  distillation  it  gives  off  paramne,  photogejxe,  and  solar  oil,  whilst  true 
coal  produces  anthracene,  naphthaline,  and  benzene. 

Its  composition,  according  to  Dr.  Stenhouse,  F.R.S.,  is — 


Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Ash 


6572 
9-03 
072 
478 

1975 


The  ash  of  Torbane  Hill  coal  is  stated  by  the  same  authority  to  contain- 


Silica 5831 

Alumina        .        .        .        .        .        .  33*65 

Ferric  oxide 7-00 

Potash 0-84 

Soda 0*41 

Lime  and  sulphuric  acid       .        .         .  traces 


Boghead  coal  is  used  both  as  fuel  for  the  manufacture  of  gas,  and  for  the  pro- 


26 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


duction  of  paraffine  and  lubricating  oils.  Other  forms  of  brown  cannels  approximating 
to  the  original  Torbane  Hill  deposit,  which  is  now  nearly  exhausted,  are  found  at 
Wemyss,  at  Rigside  and  near  Lesmahagow  in  Lanark. 

Hilt  classifies  coals  according  to  their  yield  of  coke,  which  ranges  from  52  to  over 
90  per  cent. 

L.  Gruner  maintains  that  the  technical  value  of  a  coal  can  be  better  ascertained  by 
proximate  than  by  ultimate  analysis.  He  distils  the  coal  in  a  retort  and  incinerates 
the  residue.  In  true  coals  the  combustion-value  generally  coincides  with  the  quantity 
of  fixed  carbon  left  after  distillation ;  this  is  less  commonly  the  case  with  anthracites 
and  lignites.  He  distinguishes  five  kinds  of  coal — (i)  dry  coal,  with  a  long  flame,  yielding 
50  to  60  per  cent,  of  coke,  which  is  powdery  or  at  most  fritted  ;  (2)  fat  or  gas  coal,  with 
a  long  flame,  yielding  60  to  68  per  cent,  of  coke,  fused  and  tumid ;  (3)  smithy  coal, 
giving  68  to  74  per  cent,  of  coke,  fused  and  of  mean  density;  (4)  coking  coal,  with  a 
short  flame,  yielding  74  to  82  per  cent,  of  a  very  compact  coke  with  few  blisters ; 
(5)  anthracites,  giving  82  to  90  per  cent,  of  a  fritted  or  powdery  coke. 

The  following  analyses  of  the  ash  of  Upper  Silesian  coals  are  taken  from  E. 
Jensen  : — 


6. 

* 

' 

3- 

4- 

5- 

Sand 
Si02  (soluble) 

}   39-450 

26-070 

(     3-860 
(20-940 

6-890 

38'340 

6-430 
28-2OO 

9'2OO 
27-450 

Al.,0, 

18-230 

27-800 

20*630 

15-840 

23-820 

28-570 

FeA 

15-680 

19-840 

26  'O2O 

19-270 

18-580 

10760 

MnO 

i  '330 

0-420 

2-840 

1-170 

I-430 

O-2OO 

ZnO. 

0-260 

0-370 

I'I2O 

0*090 

0-550 

0-860 

PbO. 

O'O2I 

0-069 

0-058 

0-037 

O-O82 

0-056 

CdO 

O'OOS 

O'OOI 

0-003 

0-005 

O-OO4 

O'OO2 

CaO. 

6"O2O 

11-150 

6-4OO 

2-160 

3-290 

7-450 

MgO 

2-440 

4-210 

4-690 

0-810 

0-870 

2-000 

Alkalies 

2T70 

0-760 

2'98O 

2'IOO 

3-090 

2-O9O 

SOS  (total) 

I2-830 

7-380 

9-480 

1  1  -840 

I2'6lO 

10-880 

PA 

I  -290 

1-480 

0-850 

1-090 

0-970 

0-230 

The  presence  of  copper  is  to  be  ascertained  in  coals  used  in  iron  smelting.  Schulze* 
detected  thallium  and  lithium  in  coal. 

Coke. — The  object  of  the  coking  of  coal  is  (i)  to  increase  the  proportion  of  carbon 
and  thus  to  obtain  a  higher  temperature;  (2)  to  expel  evil-smelling  constituents 
(especially  for  household  consumption) ;  (3)  to  deprive  coal  of  the  property  of  caking 
together-,  whereby  the  due  access  of  air  is  hindered,  especially  in  blast  furnaces ;  (4)  to 
expel  a  part  of  the  sulphur  always  present  in  the  form  of  iron  sulphide. 

Coking  in  heaps  is  very  similar  to  charcoal-burning.     On  the  spot  selected  there  is 

Fig.  22. 


built  a  chimney  shaft  from  i  to  i  J  metre  in  height,  which  serves  for  the  axis  of  the 
heap.     It  is  0-3  metre  in  diameter,  and  is  provided  with  several  rows  of  air-holes,  by 

*  Jahresber.  1886,  p.  1069. 


SECT.    I.] 


COKE. 


27 


which  it  is  kept  in  connection  with  the  heap  of  coal.  The  largest  pieces  of  coal  are 
laid  round  the  chimney  and  smaller  pieces  towards  the  circumference  so  as  to  round  off 
the  heap  (Fig.  22).  The  intervals  between  the  lumps  are  filled  up  with  small  coal. 
At  the  sole  of  the  heap  there  are  formed  channels  or  air  passages  leading  from  the 
circumference  towards  the  shaft.  At  the  bottom  of  the  shaft  there  are  laid  dry  chips 
of  wood,  which  are  kindled  from  above.  The  heap  is  fired  as  long  as  smoke  is  given  off, 
the  top  of  the  chimney  is  then  closed  with  an  iron  cover,  and  the  mouths  of  the  air- 
channels  are  choked  with  earth.  Sometimes  cooling  is  promoted  by  the  application  of 
cold  water,  which  is  erroneously  thought  to  desulphurise  the  coke.  The  whole  process 
is  very  similar  to  charcoal-burning. 

Oven-coking. — At  present  coking  is  effected  almost  exclusively  in  special  fur- 
naces, coke-ovens,  in  which  the  management  of  the  fire  is  easier,  an  excessive  con- 
sumption of  the  coal  is  more  readily  avoided,  and  the  yield  is  in  general  greater. 
The  ovens  in  greatest  use  are  that  of  Appolt,  which  may  be  regarded  as  a  kind  of 
upright  gas  retort  with  openings  for  the  escape  of  the  gases,  and  latterly  the  Coppee 
oven. 

Of  the  closed  coke-ovens  of  earlier  construction  may  be  mentioned  one  used  at  the 
ironworks  at  Gleiwitz  in  Silesia,  shown  in  section  in  Fig.  23.  The  cylindrical  coke- 
room,  A,  with  a  perforated  arch  above,  is  provided 
with  register-openings  in  the  walls,  o,  which  can  be 
closed  from  without  by  means  of  plugs.  There  are 
also  similar  apertures  in  the  sole,  forming  a  kind  of 
grate.  But  the  sole  may  be  advantageously  con- 
structed solid  if  care  be  taken  that  the  lowest  row  of 
apertures  is  placed  immediately  above  the  sole.  The 
coal  to  be  coked  is  introduced  partly  through  the 
opening,  b,  in  the  arch,  and  partly  through  the  door, 
a.  First  the  larger  pieces  are  inserted,  though  a 
passage  opening  at  the  door  is  left  free  for  the  intro- 
duction of  burning  coals.  After  the  oven  is  filled  up 
to  the  lower  part  of  the  discharge-pipe,  r,  the  door 

is  bricked  up  to  the  mouth  of  the  kindling  passage,  all  the  register-openings  are  closed 
except  the  lowest  row,  and  the  opening  of  the  arch  is  closed  with  the  iron  cover,  d.  As 
soon  as  the  coals  display  an  average  redness  through  the  register-holes  of  the  lowest 
row,  these  are  closed  and  the  next  row  is  opened,  which  is  the  case  in  about  ten  hours  -r 
after  another  ten  hours,  the  second  row  is  closed  ;  after  sixteen  hours,  the  third ;  and 
after  a  further  three  hours,  the  fourth.  The  oven,  when  entirely  closed,  is  let  stand 
twelve  hours  to  cool ;  the  door,  t,  is  then  opened,  the  glowing  cokes  are  drawn  out  with 
a  hook  and  at  once  extinguished 

with  water.     The   above   furnace  *'£•  24- 

takes  2  tons  of  coal,  and,  on  an 
average  of  several  months,  it 
yields  53  per  cent,  of  coke  by 
weight  or  74  by  volume.  The 
gases  and  vapours  escape  through 
the  pipe,  r,  to  a  condensing  appa- 
ratus which  serves  for  two  adjacent 
ovens.  It  liquefies  and  receives 
the  tarry  vapours,  letting  the 
gases  escape. 

The  coking  of  small  coal  is  effected  on  hearths  arched  over  after  the  manner  of  a 
baker's  oven.  The  waste  of  the  coal  mines  may  be  very  advantageously  utilised  by 


28 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


coking,  since  the  particles,  when  heated,  cake  together  and  yield  as  firm  coke  as  does 
lump  coal. 

In  the  coke- works  on  the  Saar  and  at  Sulzbach,  as  well  as  formerly  in  some  iron- 
works in  Lorraine,  ovens  are  employed  as  shown  in  section,  Fig.  24  (p.  27),  and,  Fig.  25, 

in  ground  plan.  They  are  advan- 
tageously distinguished  from  the 
earlier  coke-ovens  (in  which  the 
access  of  air  took  place  through 
chinks  in  the  doors  and  the  chim- 
ney) by  the  circumstance  that  a 
regular  current  of  air  takes  place 
through  openings  in  the  vault. 
The  sole  of  the  oven  is  egg-shaped  ; 
the  length  is  3  metres,  the  breadth 
2,  the  greatest  internal  height  i 
metre.  The  chimney,  if  metre 
high,  serves  for  introducing  the 
small  coal.  A  peculiarity  in  this 
furnace  is  the  distribution  of  the 
air-supply.  At  the  height  of  0*3 

metre  above  the  sole  there  runs  a  draught  channel  of  horseshoe  shape  round  the  oven 
space,  and  opens  at  o'  on  each  side  of  the  door,  t.  The  air  streaming  into  these  open- 
ings is  distributed  through  nine  cross-channels,  o,  and  rushes  into  the  oven  space. 
The  door,  t,  closes  the  opening  almost  perfectly.  A  charge  of  i  to  i^  cubic  metre  of 
small  coal  is  coked  in  this  oven  in  twenty-four  to  thirty  hours. 

Coke-oven  of  Appolt  Bros. — The  first  of  these  ovens  was  erected,  in  1855,  at  St.  Avoid 
(German  Lorraine).  It  is  distinguished  by  the  form  of  its  standing  shaft,  which  is 
heated  from  without,  whilst  the  heating  of  the  oven  shaft  is  effected  merely  by  vapours 


Fig.  26. 


Fig.  27. 


and  gases  evolved  and  ignited  during  the  coking.  Fig.  26  shows  the  section,  and  Fig.  27 
a  horizontal  section  on  the  line  i  to  2.  In  order  that  the  heat  may  pass  better  into  the 
shafts,  a,  they  are  of  a  prolonged  quadrangular  section  (0*45  and  i' 24  metre  by  4  metres 
deep) ;  and,  the  better  to  utilise  the  heat,  every  twelve  shafts  are  united  in  two  rows 
to  a  general  oven.  The  several  shafts  (whose  walls  are  separated  by  hollow  spaces,  6) 


SECT,  i.]  COKE.  29 

are  connected  with  each  other  and  with  the  mantle  by  masonry ;  the  empty  spaces  are 
also  connected  with  each  other.  Each  compartment  has  two  apertures — an  upper  one 
by  which  the  coal  is  introduced,  and  a  lower  through  which  the  cokes  are  allowed  to 
drop  out.  In  the  lower  part  of  the  side  wall  of  the  compartments  there  are  left  between 
the  stones  narrow  slits,  e,  through  which  pass  the  gases  and  vapours,  which  are  burnt 
in  the  hollow  spaces  with  the  co-operation  of  the  air  which  enters  through  6.  The  heat 
thus  generated  effects  the  coking  of  the  coal  in  the  interior  of  the  compartments. 

The  products  of  combustion  escape  through  the  channels  g  and  h.  The  draught  is 
regulated  by  the  slide,  fi.  The  channels  g  vent  into  a  horizontal  channel,  *',  and  the 
channels  h  intoj.  The  two  channels  i  and  j  unite  in  the  flue,  k.  The  compartments 
of  the  oven  (Fig.  26)  are  contracted  at  their  upper  end  by  projecting  stones,  so  that 
there  remains  only  a  small  opening,  which  is  closed  with  an  iron  cover.  This  cover  has 
in  the  middle  a  pipe,  through  which  a  part  of  the  gaseous  and  vaporous  products  of  dis- 
tillation can  be  led  off.  A  tramway  running  along  over  every  series  of  oven  compart- 
ments receives  the  truck,  which  each  time  brings  to  a  compartment  its  charge  of  1200 
kilos,  of  coal.  In  the  solid  masonry  below  the  oven  there  are  two  passages,  in  which 
the  trucks  for  receiving  the  coke  travel  on  tram-lines. 

In  working  the  oven,  wood  fires  are  placed  in  the  compartments,  upon  which  coal  is 
then  placed.  The  interior  of  the  oven  is  rapidly  heated  by  the  combustion  of  the  gases 
which  issue  from  the  compartments  through  the  slits,  e.  When  the  oven  is  hot  enough 
to  effect  the  decomposition  of  the  coal  and  the  combustion  of  the  volatile  products,  the 
compartment  is  charged  with  coal,  and  the  upper  opening  is  closed  by  putting  on  its 
cover  and  luting  it  down.  Two  hours  later  the  same  operation  is  repeated,  and  so  on 
until  in  the  course  of  twenty-four  hours  all  the  compartments  are  charged.  By  that 
time  the  coking  in  the  first  compartment  is  completed,  and  the  coke  is  taken  out. 
When  empty,  the  compartment  is  charged  afresh,  and  two  hours  later  the  second  com- 
partment is  in  like  manner  emptied  and  re-charged. 

The  Appolt  ovens  are  expensive  to  build,  but  each  yields  daily  1 2  tons  of  coke,  and, 
as  there  is  scarcely  any  loss,  the  Duttweiler  coal  yields  66  to  6 7  per  cent,  of  coke,  whilst 
in  a  horizontal  oven  it  would  give  at  most  6 1  per  cent.  A  defect  of  the  Appolt  system 
is,  that  the  compartments  in  the  middle  of  a  row  receive  more  heat  than  those  at  the 
ends,  and  with  the  same  kind  of  coal  yield  a  denser  coke,  a  circumstance  which  is  dis- 
turbing in  metallurgical  operations. 

Of  great  importance  are  the  coke-ovens  arranged  for  securing  the  tar  and  ammonia. 
The  earliest  furnace  of  this  kind  was  constructed  by  Knab,  and  was  heated  from  the 
sole  only.  Carves  in  1863  added  heating  from  the  sides,  and  Hiissener  (1883)  im- 
proved the  access  of  gas  and  air.  In  the  fifty  ovens  erected  on  this  plan  in  Gelsen- 
kirchen,  the  retort  is  9  metres  long,  conical  in  shape,  0*575  metre  broad  in  the  middle, 
and  i '8  metre  high.  Its  available  capacity  is  88  per  cent,  of  the  total  space,  and  it  holds 
5^  tons  of  dry,  finely  sifted  coking  coal,  reckoning  i  cubic  metre  at  690  kilos.  The 
distillation  has  been  in  uninterrupted  work  since  November  1882.  At  first  there  were 
used  finely  sifted  coals  from  Gelsenkirchen  ;  they  were  relatively  too  impure,  not  having 
been  washed.  The  sale  was  difiicult,  and  the  impurities  produced  so  much  waste  that 
fat  coal  was  chiefly  used  in  place  of  gas  coal.  The  time  of  preparing  was  at  first  seventy- 
two  hours,  but  by  a  better  distribution  of  the  gases  in  the  channels  it  was  gradually 
reduced  to  fifty -two  to  fifty-six  hours.  la.  order  to  insure  a  periodical  regularity  in 
charging  and  emptying  the  retorts,  these  operations  are  effected  within  sixty  hours. 
The  yield  was — 

Gas  Coal.  Patty  Coal. 

Lump  coke      ....     61 700  per  cent.  ...  75  *oo  per  cent. 

Small  coke      ....       3*500        „  ...  0*80        „ 

Dirt 9-180        „  ...  1*20        „ 

Tar 2720        „  ...  277        „ 

Ammonium  sulphate       .         .       0*924        ,,  ...  i'io        „ 


.3° 


CHEMICAL  TECHNOLOGY. 


[SECT,  i, 


Boiling  between    80°  and  100° 
„  „         100°  and  140° 

Solvent  naphtha     . 
Phenol,  purified 
Pure  anthracene     . 


The  tar  is  very  thin;  100  kilos,  yielded  58*83  distillate;  39*51  pitch  distillate; 
1*65  loss.  A  closer  examination  of  the  tar  showed  :  Benzol,  purified  with  sulphuric 
acid  and  soda,  and  several  times  fractionated — 

.  0*59  per  cent. 

•  0-49 

-  0-39 
.  i'37 
.  0-95 

whilst  in  gas-tars  the  maximum  yield  is  only  0*25  to  0*3  per  cent. 

The  crude  gases  have  in  the  receiver  above  the  oven  a  pressure  =  2  mm.  of  water, 
and  a  temperature  of  75°  to  80°.  The  purified  gases  have  a  pressure  =  90  to  no  mm. 
of  water,  and  a  temperature  of  15°.  The  combustion  gases  contain  on  an  average — 

Carbon  dioxide 8'i  per  cent. 

Carbon  monoxide    .        .        .        .        .0*4        „ 
Oxygen   .        .        .        .        .        .        .0-3        „ 

and  evaporate  0*91  to  i  kilo,  water  for  each  kilo,  of  coal  put  in  the  retorts. 

G.  Hoffmann  (1884)  combines  the  coke-ovens  with  the  Siemens  heat  reservoirs.  This 
arx-angement  was  first  introduced  experimentally  in  the  Silesian  Coal  and  Coke  Works 
at  Gottesberg,  without  a  condensation  apparatus  for  the  gas,  then  with  very  perfect 
-apparatus  for  liquefaction  in  an  installation  of  twenty  ovens  at  the  Pluto  Mine,  near 

Fig.  28. 


Explanation  of  Terms. 


Maschimnhaus 
Ammoniakfabrik 


ftaskuhler 
Gaswascher 


Windleitung 
AmmoniaTc 
Theervorrathe 


Steam-engine  house. 
Ammonia-works. 
Condensation. 
Gas-coolers. 
Gas-mixer. 
Exhausters. 
Ventilator. 
Air-duct. 
Ammonia- tank. 
Tar-stores. 


ttetortenofen 

DrucklcituiHj 

Sauffle.itiing 

s 

Schornstein 

Maschinenseite 

Vorlage 

Koksofen 

Koksseite 


Ketort  furnace. 

Pressure-duct. 

Suction-duct 

Gasometer. 

( !himney. 

Machinery  shed. 

Receiver. 

('oke-oven. 

Coke-shed. 


SECT,  i.]  COKE.  31 

Wanne,  and  in  twenty  ovens  at  the  Gottesberg  works.  The  results  of  these  installa- 
tions are  so  exceedingly  favourable  that  at  present  120  ovens  have  been  built  in 
Germany  with  the  same  arrangement  for  securing  the  by-products.  Fig.  28  shows 

Fig.  29. 


^^ 


—  V-U 

rnr 

S5 

5 

i 

:::  -.::v 

.-:•:::.• 

= 

^pi 

^: 

w 

.  ^  ".:'.:: 

-/.-:..:.. 

-vv~ 

—•:•'::. 

^.—.~. 

r-:-..i 

S 

'-.-::':'•:. 

-..-.-;:: 

;:.':":. 

L'v.'... 

•  = 

_J 

E 

< 

L*_ 

Fig.  30.  Fig.  34. 

the  general  arrangement  of  the  ovens  and  condensation  at  the  Pluto  Mine,  and 
Figs.  29  to  34  represent  the  details.  The  coke-ovens,  with  vertical  draughts  in  the 
sidewalk,*  are  9  metres  long,  a  clear  width  of  o'6  metre,  a  height  of  r6  metre,  and 

*  See  Jahresber.  1883,  p.  1221. 


32  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

the  distance  from  middle  to  middle  is  0-95  metre.  In  ordinary  ovens  without 
arrangements  for  securing  tar  and  ammonia  there  are  openings  in  the  coking  cham- 
bers through  which  the  gases  first  pass  into  the  lateral  walls,  and  then  into  the  channels 
in  the  sole,  and  there  burn  along  with  atmospheric  air.  By  this  the  combustion 
chamber  is  heated  sufficiently  for  the  process.  In  the  oven  before  us  there  is  no 
direct  connection  between  the  coking  chamber  and  the  wall.  Besides  the  openings  for 
charging  and  emptying  (which  are  closed  during  the  process),  this  oven  has  only  two 
apertures,  a,  in  the  arch  by  which  the  gases  evolved  may  escape.  In  the  side  wall  of 
the  oven  there  is  a  channel,  m,  arranged,  which  passes  over  all  the  perpendicular 
draughts  of  the  side  wall,  and  renders  the  connection  possible.  Each  channel  in  the 
sole  is  divided  into  two  parts,  s  and  S,  in  the  longitudinal  direction  of  the  oven. 
Each  part  is  connected  with  two  regenerators,  which  lie  side  by  side.  Of  these  g  and  G 
serve  to  heat  the  gas  to  be  expended  in  the  combustion ;  I  and  L  serve  to  heat  the  air 
required.  These  regenerators  are  long  channels,  set  grate-like  with  stones  so  as  to 
expose  a  large  surface.  They  pass  underneath  the  entire  group,  and  at  their  end  are 
the  two  air-heaters,  I  and  Z,  connected,  by  an  alternating  valve,  either  with  the  pipe  for 
introducing  air  or  with  the  chimney.  The  gas-heaters,  g  and  G,  are  likewise  brought  in 
connection  either  with  the  gas-efflux  pipe,  or  with  the  chimney,  by  means  of  an  especial 
alternating  valve.  When  the  ovens  are  hot,  and  have  been  charged  with  coal  at/",  the 
gases  of  the  coals  which  are  coking  escape  by  the  aperture  a  into  the  ascending  pipe,  r, 
and  pass  through  the  open  valve,  v,  into  the  receiver,  F.  From  hence  they  proceed  to  the 
condensation  arrangement,  where  they  are  cooled  in  the  refrigerators,  JT,  and  are  washed 
in  the  scrubbers,  W  (Figs.  32  to  34).  The  gases  are  then  again  forced  from  the  con- 
densors  back  to  the  ovens  (by  means  of  the  same"  blast,  which  has  sucked  them  into 
the  refrigerators  and  occasioned  their  entire  movement),  and  according  to  the  position 
of  the  alternating  valve  of  the  gas-pressure  pipe,  either  to  the  regenerator  g,  or  to  the 
one,  G,  on  the  other  side.  If  we  assume  that  the  gas  passes  to  g,  the  alternating  valve 
of  the  air-regenerators  is  placed  so  that  the  air  blown  in  enters  the  regenerator  L 
This  and  the  gas-regenerator  g  open  in  every  oven  through  the  adjacent  apertures  o 
and  d  to  the  channel  s  in  the  sole.  The  total  current  of  the  gases  in  course  of  com- 
bustion and  of  the  hot  products  of  combustion  passes  through  the  ascending  channels 
c  into  the  horizontal  channel  m,  and  thence  descend  through  the  vertical  flues,  e, 
into  the  channel  S  in  the  sole,  where  the  spent  gases  escape  to  the  chimney  through  the 
air-regenerator  L  and  the  gas-regenerator  G,  and  give  off  their  remaining  heat  to  the 
grating  of  the  regenerators.  After  about  one  hour,  the  two  alternating  valves  are 
reversed,  and  the  current  then  takes  the  opposite  way.  The  gas  passes  from  the  con- 
densors  into  the  gas-regenerator  G,  and  the  air  into  the  air-regenerator  L.  The 
combustion  takes  place  in  S.  The  current  of  gas,  air,  and  of  the  products  of  combustion 
passes  through  e  towards  m,  and  then  through  c  towards  s,  and  through  the 
regenerators  I  and  g  to  the  chimney. 

Such  is  the  original  arrangement  of  the  coke-ovens  at  the  Pluto  Mine ;  but  the 
regeneration  of  the  gas  was  abandoned  at  the  very  beginning,  so  that  only  the  air  was 
heated,  and  on  the  following  grounds  : — The  proximity  of  the  long  gas-  and  air-regene- 
rators may,  in  the  possible  case  of  leakage  of  their  sides,  lead  to  a  mixture  of  air  and  gas 
in  the  regenerators,  and  consequently  to  fusions  in  them,  involving  irregularities  in 
working.  Further,  at  each  reversion  of  the  alternating  valve  the  whole  of  the  gas  con- 
tained in  the  regenerators  is  wasted,  which,  on  account  of  their  large  size,  demands  con- 
sideration. Besides,  at  the  reversal,  the  escaping  hot  gas  between  the  valve  and  the 
chimney  meets  with  the  hot  contents  of  the  air-regenerator,  when  explosions  may  ensue. 
Lastly,  the  volume  of  the  air  necessary  for  the  combustion  of  the  gas  is  about  sixfold  that 
of  the  latter.  It  seems,  therefore,  simpler  and  more  important  to  raise  the  large  volume 
of  the  air  alone  to  a  very  high  temperature  rather  than  to  heat,  in  addition,  the  small 


SECT,  i.]  COKE.  33. 

volume  of  the  gas  and  to  withdraw  the  heat  required  for  this  purpose  from  the  air. 
Hence  the  two  regenerators,  as  they  lie  side  by  side,  are  used  for  the  air  only,  and  the 
gas  is  led  out  of  the  pipe,  returning  from  the  condensation  either  to  n  or  N,  according; 
to  the  position  of  the  alternating  valve.  In  each  oven  a  connection  between  the  gas- 
pressure  tube  and  the  channel  in  the  sole  is  effected  by  means  of  a  small  pipe  fitted 
with  a  cock.  The  valve  in  the  gas-pressure  tube  and  that  at  the  end  of  the  air-regene- 
rators are  placed  to  correspond.  When  the  gas  passes  through  the  pressure  conductors 
into  the  sole  channels  on  one  side,  the  air  sweeps  through  the  regenerators  on  the 
same  side  into  the  same  sole  channels,  and  the  combustion  and  the  route  taken  by  its 
products  are  those  already  laid  down. 

At  present,  instead  of  two  regenerators  on  each  side,  there  is  only  a  single  one  in  use 
on  each  side  of  the  battery,  serving  merely  for  re-heating  the  air.  By  means  of  this 
arrangement  the  air  for  combustion  can  be  very  rapidly  and  intensely  heated.  By 
means  of  this  "  Siemens  regeneration  "  the  air  at  the  Pluto  Mine  can  be  raised  above 
1000°,  and  by  using  for  combustion  air  so  extremely  hot  it  is  possible  to  employ  only 
a  part  of  the  cold  air  returning  from  the  condensation  (impoverished  by  the  loss  of  the 
tar)  in  order  to  set  the  coking  process  in  action  and  keep  the  ovens  sufficiently  hot. 
It  has  been  found  in  practice  that  there  is  no  need  to  use  all  the  gas  for  heating  the 
ovens,  otherwise  the  combustion  spaces  would  become  too  hot.  Hence  there  is  much 
more  gas  than  is  needed  for  maintaining  the  coking  process,  the  excess  being  daily 
100  cubic  metres  per  oven.  The  temperature  is  so  high  that  the  process,  with  a  normal 
charge  (i.e.,  5750  kilos,  dry  coal  per  oven),  is  completed  in  forty-eight  hours ;  the  time  is 
often  less.  If  the  process  is  too  rapid  it  is  merely  requisite  to  introduce  less  gas,  so  as 
slightly  to  reduce  the  temperature  and  bring  the  time  to  forty-eight  hours.  The 
process  is  quite  under  control,  since  both  gas  and  air  are  forced  in,  and  the  quantities 
of  each  can  be  accurately  regulated.  The  quality  of  the  coke  is  excellent,  arid  the 
quantity  is  about  7  per  cent,  more  than  in  the  common  ov^ns. 

The  gas-refrigerators,  K  (Figs.  32  and  33),  are  upright  iron  cylinders  with  iron 
tubes,  x,  fixed  in  the  top  and  the  bottom.  From  the  top  piece,  w,  water  flows  down 
through  the  iron  pipes  and  cools  the  gas,  which  is  passing  between  these  cooling 
tubes  in  the  opposite  direction.  Several  gas- coolers  are  connected  together  in  such  a 
manner  that  the  cooling  water  which  flows  down  from  the  first  gas-cooler  enters  the 
second  from  above,  whilst  the  gas  travels  in  the  opposite  way.  The  gas,  after  its 
escape  from  the  oven  in  the  ascending  tube,  has  a  temperature  of  600° -7 00°  ;  in  the 
receiver  2oo°-4oo°,  according  to  the  distance  from  the  ascending  pipe.  Before  the 
gas-coolers  the  heat  is  75°-i 20°,  and  after  them  i7°-3o°.  By  cooling,  the  gas  parts 
with  a  large  portion  of  tar  and  ammoniacal  liquor,  about  75  per  cent,  of  the  total 
liquor  which  the  condensation  furnishes.  In  the  scrubbers,  W  (Fig.  34),  there  are 
arranged  a  great  number  of  perforated  metal  sheets  at  distances  of  about  10  centi- 
metres above  each  other.  Upon  the  topmost,  cold  water  is  constantly  dropping,  so 
that  a  drizzle  of  water-drops  is  always  falling  from  sheet  to  sheet  so  as  to  meet  the 
ascending  current  of  gas,  which  yields  up  its  ammonia  to  the  water.  The  ammoniacal 
water  flows  off  below,  and  if  not  sufficiently  strong  in  ammonia  is  pumped  up  again 
and  again  to  meet  the  current  of  gas  until  it  is  strong  enough  to  be  saleable.  Several 
scrubbers  are  placed  in  connection,  so  that  the  gas  in  passing  through  them  comes  in 
contact  in  the  last  with  pure  water  only,  and  is  enriched  with  ammonia  in  those 
scrubbers  into  which  the  gas  first  enters.  The  scrubbers  remove  the  25  percent,  of  the 
/tmmonia  which  still  remained  in  the  gas-coolers,  and  at  the  same  time  eliminate  very 
much  tar.  If  the  water  employed  in  the  scrubbers  is  sufficiently  cold,  the  temperature 
of  the  gas  falls  to  13°.  The  separation  of  the  tar  and  the  ammoniacal  liquor  is  effected 
in  cisterns  by  means  of  specific  gravity.  The  ammoniacal  water  is  enriched  in  the 
scrubbers  until  it  has  a  specific  gravity  of  40-4'50  Be,  representing  1-78  per  cent,  of 

c 


34  CHEMICAL  TECHNOLOGY.  [SECT-  I- 

ammonia.  As  the  yield  is  about  14  per  cent,  of  ammonia  at  3°,  the  yield  of  ammonia 
•calculated  as  ammonium  sulphate  is  about  i  per  cent,  of  the  dry  coal. 

At  the  Pluto  Mine  the  ammonia  water  is  not  converted  into  ammonium  sulphate, 
but  sold  as  liquid  ammonia  according  to  its  strength.  The  yield  of  tar  is  on  the  average 
3^46  per  cent,  for  the  best  working  month,  and  278  per  cent,  for  the  worst  month, 
•calculated  on  the  dry  coal.  These  fluctuations  are  owing  to  the  circumstance  that 
sometimes  the  supply  of  water  for  refrigeration  is  insufficient.  The  water  needed 
•daily  is  5  cubic  metres  per  oven. 

The  proportion  of  the  chief  constituents  of  the  tar  (calculated  as  anhydrous)  is, 
According  to  the  researches  of  Knublauch — 

Benzol 0^954-1 -o6  per  cent. 

Naphthaline 4  '270-5  '27        „ 

Anthracene 0-57  5-0 '64        „ 

Pitch about  50          „ 

A  greater  or  less  proportion  of  this  pitch  can  be  driven  off  on  prolonged  distillation. 
The  residue  insoluble  in  glacial  acetic  acid  or  in  benzene  is  10  to  25  per  cent,  of  the 
tar. 

In  each  oven  there  is  a  daily  excess  of  TOO  cubic  metres  of  gas  of  the  following 
•composition.  It  has  about  half  the  candle  power  of  that  of  the  Cologne  Gasworks. 
Small  quantities  of  this  gas  are  burnt  for  lighting,  with  very  large  burners.  It  may 
.also  serve  for  heating  boilers,  &c.  It  contains  : — 

Coking  Gas.  Ccbgne  Gas. 

Benzol  vapour         .         .         .        .  o'6o  ...  1^54 

Ethylene i'6i  ...  1*19 

ELS 0-42 

CO2          .         I 1-39  ...  0-87 

CO 6-41  ...  5-40 

H 52-69  ...  55  -oo 

Methan 35'67  ...  36-00 

Water 1-21 

This  gas,  as  a  source  of  heat,  has  the  advantage  that  it  can  be  conveyed  to  a  dis- 
tance. The  waste  heat  from  the  regenerators,  which  escapes  into  the  chimney  at  420°, 
•can  be  very  well  used  for  heating  boilers,  perhaps  most  advantageously  with  the  simul- 
taneous combustion  of  the  superfluous  gas  along  with  hot  air  from  the  cooling  channels 
of  the  coke-ovens  or  from  the  regenerators.  Such  a  utilisation  of  the  waste  heat  and 
of  the  superfluous  gas  for  heating  boilers  is  about  to  be  carried  out  at  a  Westphalian 
coke-works.  , 

The  return  from  collecting  the  by-products  depends,  independently  of  the  construc- 
tion of  the  ovens  and  the  condensations,  and  of  the  careful  working  of  the  process, 
essentially  on  the  quality  of  the  coal,  i.e.,  its  richness  in  gas,  tar,  and  ammonia.  Good 
coking  coals  are  especially  adapted  for  the  profitable  collection  of  the  by-products.  If 
we  assume  the  price  of  tar  to  be  55.  60?.  per  100  kilos.,  then  for  10  tons  of  dry  coal 
the  net  returns  in  tar  for  a  yield  of  3^  per  cent,  will  be  19*.  $d.  The  yield  of  ammonia 
from  the  Westphalian  coal  is  in  general  about  i  per  cent,  of  the  dry  coal,  calculated  as 
ammonium  sulphate.  In  Upper  Silesia,  the  coal  is  richer  in  ammonia,  and  reaches  1-37 
per  cent,  on  the  dry  coal.  If  we  take  the  market  price  for  100  kilos,  ammonium  sul- 
phate as  27$.  (it  has  since  fallen  to  2OS.-225.),  and  deducting  55.  for  the  cost  of  manufac- 
ture, the  net  returns  per  10  tons  dry  coals  (yielding  1*37  per  cent,  ammonium  sulphate) 
will  be  30*.  6d.  We  may  assume  that  a  coke-oven  fitted  with  all  appliances  for  securing 
the  by-products  will  cost  three  to  four  times  as  much  as  a  common  coke-oven.  Unless, 
therefore,  the  returns  of  such  an  establishment  are  good,  the  costliness  of  the  plant 
stands  in  the  way  of  a  rapid  extension  of  the  system. 


SECT,  i.]  DEGASIFYING,  GASIFYING,  COMBUSTION.  35 

It  has  never  been  found  practicable  to  convert  the  total  nitrogen  of  coal  into 
ammonia  by  dry  distillation.  Thus,  W.  Foster,  on  distilling  a  coal  containing  173  per 
cent,  of  nitrogen,  obtained  14*51  per  cent,  of  the  total  nitrogen  as  ammonia,  1-56  as 
cyanogen,  35*26  in  the  gases,  whilst  48*66  per  cent,  remained  in  the  coke.  Winkler* 
calculates  that  18,000,000  tons  of  coal  are  yearly  coked,  from  which  58,600  tons  of 
ammonia  might  be  obtained. 

The  cokes,  when  extracted  from  the  ovens  or  retorts,  are  quenched  with  water. 
The  three  main  strata  of  a  charge  of  coke  take  up  water  to  very  different  degrees. 
The  porous  top  layer  may  absorb  as  much  as  120  per  cent,  of  its  weight,  the  main 
mass  of  the  charge  in  the  middle  takes  up  only  i£  per  cent.,  and  the  bottom  layer  may 
absorb  13  per  cent.  As  a  rule,  we  may  assume  that  cokes  gain  6  per  cent,  of  their 
weight  if  they  are  moistened  with  that  quantity  of  water  only  which  is  needed  to 
quench  them.  Quenched  cokes  thrown  when  cold  into  water  do  not  take  up  one-third 
of  the  quantity  which  they  do  if  thrown  in  when  red  hot. 

Cokes,  when  properly  burnt,  form  a  uniform  dense  solid  mass  not  easily  broken  or 
crushed,  and  having  no  very  large  bubbles  or  blisters.  Coke  prepared  in  kilns  from 
baking  coal  has  a  surface  like  cauliflowers,  and  a  melted  appearance,  not  owing  to  fusion, 
but  to  a  fine  division  of  carbon,  which  is  separated  out  at  high  temperatures  from  the 
hydrocarbons  formed  at  the  beginning  of  the  process.  The  colour  is  a  black-grey  or 
iron-grey  with  a  dull  metallic  lustre.  The  sulphur  in  organic  combination  is  only 
driven  off  to  a  very  slight  extent  on  coking. 

On  account  of  its  density  and  the  absence  of  combustible  gases,  the  combustibility 
of  coke  is  so  slight  that  it  requires  for  ignition  a  strong  red  heat  and  a  concentrated 
stream  of  air  to  maintain  the  fire.  The  combustion  value  ranges  from  7000  to  8000 
heat-units,  according  to  the  proportion  of  ash. 

Briquettes ;  Block-coal. — Under  this  name  is  understood  a  fuel  originally  pulveru- 
lent, such  as  coal-slack,  sawdust,  &c.,  mixed  with  a  binding  ingredient,  such  as  tar  or 
clay,  and  pressed  into  blocks  or  brick-shaped  masses.  Here  might  rank  pressed  peat, 
pressed  lignite,  and  cakes  of  spent  tan  or  dye-woods. 

The  moulded  charcoal  (Paris  coal)  consists  of  charcoal  made  coherent  by  means  of 
tar  and  re-charring.  100  kilos,  of  charcoal-dust  are  worked  up  with  33  to  40  litres  of 
coal-tar,  and  the  mass  is  moulded  into  the  form  of  cylinders.  These  cylinders  are  then 
dried  from  thirty-six  to  forty-eight  hours,  and  then  charred  in  muffle  furnaces.  Here 
belongs  also  the  pressed  charcoal  (pyrolite),  consisting  of  charcoal-dust,  a  little  soda- 
saltpetre,  and  a  cohesive  ingredient,  such  as  dextrine  or  starch-paste.  Such  fuels  are 
<used  in  quantity  in  some  countries  for  heating  locomotives,  for  small  household  stoves, 
for  drying  rooms  in  newly  built  houses,  where  the  carbonic  acid  given  off  combines 
with  the  lime  of  the  mortar.  A  very  imperfect  fuel  is  the  carbonatron  introduced  into 
commerce  by  Nieske,  and  made  of  charcoal-dust. 

Coal  blocks,  &c.,  consist  of  small  coal  and  a  binding  agent  mixed  together  and 
pressed  into  shape.  The  binding  materials  are  coal-tar,  coal-pitch,  hard  and  soft, 
natural  asphalt,  potato  starch,  treacle,  <fec. ;  also  gypsum,  alum,  soluble  glass,  &c. 

DEGASIFYING,  GASIFYING,  COMBUSTION. 

The  important  point  in  the  application  of  the  fuels  already  mentioned  (wood,  peat, 
•coal)  is  their  behaviour  when  heated. 

1.  Heated  alone:  charring,  coking,  illuminating  gas. 

2.  Heated  with  access  of  combined  oxygen  (H2O,  CO2) :  water-gas. 

3.  With  limited  access  of  free  oxygen  (air)  :  generator-gas. 
.4.  With  sufficient  access  of  air :  ordinary  burning. 

*  Jahresber.  1884,  p.  1249. 


CHEMICAL   TECHNOLOGY. 


[SECT.  i. 


Gases, 
20  to  35  per  cent. 


The  processes  under  No.  i  are  known  as  degasifying:  those  under  2  and  3  as 
gasification,  i  and  2  take  place  with  absorption  of  heat ;  3  and  4  with  liberation  of 
heat. 

Degasifying. — If  wood  is  heated,  there  escapes  first  the  hygroscopic  moisture ;  at 
about  170°  a  part  of  the  carbon  is  given  off  as  carbon  dioxide,  carbon  monoxide,  and 
methan ;  hydrogen  and  oxygen  are  split  off  as  water,  and  there  gradually  appear  the 
constituents  of  methylic  alcohol,  &c.,  acetic  acid,  tar,  &c.,  whilst  the  residual  charcoal 
becomes  continually  richer  in  carbon  and  in  acetic  acid.  The  following  are  the  chief 
products  from  degasifying  wood  : — 

Carbon  dioxide 

Carbon  monoxide 

Hydrogen 

Methan,  CH4 
(  Acetylene,  C2H2 
]  Ethylene,  C2H4 

Propylene,  CSH6 

Butylene,  C4H8 
I,  Benzol,  C6H6 
/Benzol,  C6H6 

Toluol,  C7H8 

Xylol,  C8H10 

Styrolene,  C8H8 

Naphthaline,  CIOHg 

Retene,  C1SH,8 

Paraffine,  C^H^  to  C.,2H43 
,  Pyrogallic  dimethyl  ether,  CgH,aO, 
\  Phenol,  CfiH6O 

Cresol,  C.H80 

Phlorol,  C8H10O 

Pyrocatechine,  C6H6O2 

/  p     TT    Q 

Methylesters  of  pyrocatechine  I  Q7,r8  fi 
(guaiacol  and  homologues)     1  r,8iTlon2 
w»ni2u» 

\Pyrogenous  resins 
fFurfurol,  C5H4O2 

Formic  acid,  CH2O2 

Acetic  acid,  C2H4O2 

Propionic  acid,  CSH,.O2 

Butyric  acid,  C4H8O, 

Valerianic  acid,  CSH10O., 

Capronic  acid,  C6H12O2 

Crotonic  acid,  C4H6O.j 

Angelicic  acid,  CSH8O2 

Aceton,  C3H6O 

Methyl  acetate,  CSH,.O, 

Methylic  alcohol,  CH40 

Allylic  alcohol,  C3H4O 

Methylamine,  CHSN 

Hydroccerulignon,  CI5H18OS 
V  Phenoles,  guaiacoles,  and  pyrogenous  resins 
(Carbon 
\  Hydrogen  and  oxygen 

Ash 


Tar, 
3  to  9  per  cent. 


Wood  vinegar, 

water,  &c., 
35  to  45  Per  cent- 


Charcoal, 
20  to  30  per  cent. 


The  gases  evolved  on  the  distillation  of  beech  wood  contain,  according  to  the  author's 
investigations,  58-65  per  cent,  carbon  dioxide,  30-35  carbon  monoxide,  up  to  5  per 
cent,  methan  and  4  per  cent,  hydrogen.  The  combustion-value  of  these  gases  i» 
therefore  trifling.  The  products  of  the  distillation  of  peat  are  similar,  but  those  of 
lignite  have  a  higher  value. 

The  products  of  the  degasification  of  coal  are  more  completely  known  : — 


SECT.    I.] 


DEGASIFYING,   GASIFYING,   COMBUSTION. 


37 


1.  Coke. 


II. 


Illuminating 
gas. 


Luminiferous 
ingredients. 


Gases 


Vapours 


Diluents 


Impurities 


III.  Ammoniacal 
liquor 


IV.  Tar,  according  to  Schultz  and  others  : — 


Acetylene,  C2H2 
Ethylene,  C2H4 
Propylene,  CSH4 
Butylene,  C4Hg 
Allylene,  C3H4 
Crotonylene,  C4H6 
Terene,  C5Hg 
Benzol,  C6H6 
Thiophene,  C4H4S 
Styrolene,  CSH8 
Naphthaline,  C10H8 
Methylnaphthaline,  C,,H10 
Fluorene,  C):jH10 
Fluoranthene,  (J15H10 
Propyl,  C3H7 
Butyl,  C4H9 
Hydrogen 
Methan,  CH4 
Carbon  monoxide,  CO 
Carbon  dioxide,  C02 
Ammonia,  NHS 
Cyanogen,  CN 
Cyanmethyl,  C2H,N 
Sulphocyanogen,  CNS 
(  Hydrogen  sulphide,  SH2 
Sulphuretted  hydrocarbons 
Carbon  disulphide,  CS, 
Carbon  oxysulphide  (?j,  COS 
Nitrogen 

Ammonium  carbonate,  (NH4),CO, 
Ammonium  sulphide,  (NH4)2S 
Ammonium  sulphocyanide,  NH4CNS 
Ammonium  chloride,  NH4C1 
A  mmonium  cyanide,  NH4CN 


r 

Name. 

Formula. 

Melting-point. 

Boiling-point. 

r 

f                        i.  Fatty  Series. 

Crotonylene        * 

C4H6 

liquid 

25° 

Amylene     

C5H10 

„ 

30 

Hexylene    

C6H12 

„ 

71 

Hydrocarbon      

V<fiv> 

„ 

85 

Jacobsen's  hydrocarbon      .... 

1 

» 

150 

Paraffine     .         .         .         .         .        . 

t 

solid 

400  ? 

2.  Aromatic  Series. 

Benzol         

C6H6 

+  3° 

81 

Toluol         

C7H8 

liquid 

in 

n 

Orthoxylol  

^8^10 

„ 

141 

13 

a 

Metaxylol  

,, 

141 

a 

3 

Paraxylol   

(J 

15° 

J37 

o 
ja 

Styrol         

^8^8 

liquid 

146 

a 

o 

a 

Mesitylene  

C9H12 

„ 

163 

§  i 

o     , 

2 

Pseudocumol      

„ 

169 

1 

•o 

Hemellithol        

>» 

J75 

2 

t*i 

n 

Terpene      

Ci0HI6 

171 

01 

^ 

Cymol         

^10^14 

i) 

175 

£•+ 

< 

Tetramethylbenzol      

« 

Naphthaline  hydride  

CIOHIO 

liquid 

205 

Naphthaline        .         .         ... 

^lO^s 

80° 

217 

a-Methylnaphthaline  

CnHIO 

— 

243 

i2-?° 

24.1  '$ 

Diphenyl    

C,2H10 

J     D 
71 

*••+*  3 
254 

i 

Berthelot's  hydrocarbon     .... 

? 

85 

26O 

Aoenaphthene    

Ci2H10 

99 

280 

i 

Fluorene     

C]3H10 

"3 

294 

Pbenanthrene     

C,4H10 

IOO 

340 

Fluoranthen       

C15H)0 

109 

above  360 

Pseudophenanthrene  

C,8H12 

"5 

,, 

i 

^Anthracene         .         .         . 

C14H10 

213 

» 

CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


Nime. 

Formal*. 

Melting-point. 

Boiling-point. 

•f'  3.  Bases.  2.  Acids.  I.  Neutral  compounds. 

{>  '  •s 
%  B.  Other  neutral  A.  Hydro- 
|f  compounds.  carbons. 

Methylanthracene       
Pyrene        
Chrysene    
Chrysogen  
.  Parachrysene      

C1BHIO 

8? 
i) 

CS2 
C2H6O 
C2HSN 

C12H9N 
C16HUN 
C4H4S 
C6H.S 

H2S 
CNH 
CO, 
C2H402 
C6HB0 
C7H80 

C8HI00 

C10H12°2 

C^H,/), 

» 

C7H602 

NHS 

C6H5N 
C4H5N 
C6H7N 
C7H9N 
C8HUN 
C6H7N 
C9H1SN 
CIOHI5N 
CnH17N 
C9H,N 
C14H9N 
C12H19N 
CnHnN 

2OO 
119 

250 
290 
320 

liquid 

'o° 
238 
330 

liquid 

17° 
42 

liquid 
36° 

215 

121° 

gas 
liquid 

i 

> 
i 

i 
» 
» 
»» 
»> 
»> 

107° 

above  360 

M 

n 

>» 
)> 

47 
78 
82 

IOO 

u   35S 
above  440 

84 
137 

119 
182 
188 
20  1 
199 

195 
124 
104 
249 

"5 
126 

179 
182 
1  88 

211 
230 

239 
240 

251 
257 
360  + 

Ethylic  alcohol  
Acetonitrile        
Water         
Carbazol     
Phenylnaphthyl  carbazol    .... 
Thiophene  
/Ihioxene    

/Hydrosulphuric  acid  
Hydrocyanic  acid        .         .         .         .        ''.', 
Carbonic  acid              

Phenol        .                  

Orthocresol                  
Metacresol                   
Paracresol  .                 
Xylenol       .                  
Isodurol      .                  

|8-Pyrocresol                

\Benzoic  acid                .         . 

/Ammonia                      
Pyridine                       
Pyrrol                           

Lutidine                       
Collidine                       
Aniline                          
Parvoline                      
Corindine                              .    _  . 
Rubidine                      
Quinoline                       .         .                  . 

Viridine                        ..... 
Cryptidine                   
\Acridine                       

iigenous  compounds  ]  p^rP^eE 

.  These  products  are  modified  according  to  the  intensity  and  the  duration  of  the  heat. 
Wright  obtained  from  the  same  quantity  of  coal  from  8-25  to  12  cubic  metres  of  illu- 
minating gas,  according  to  the  temperature  used,  and  of  the  following  composition  : — 

Cubic  metres. 
Hydrogen 
Carbon  monoxide  . 
Methan   . 

Heavy  hydrocarbons 
,          Nitrogen 

Coal  which,  for  complete  degasifying,  required  six  hours  yielded  gases  of  the  follow- 
ing composition  after  the  times  specified  : — 


8-25. 

9'7- 

12. 

38-09  per  cent. 

872        „ 

•••    4377  Per  cent.     ... 
...     12-50 

48^02  per  cent. 
13-96 

4272 

7'55 
2-92 

...     34-50 
...      4-83        „ 
•••      3'4Q        

3°7o        ,„ 

4'5i        » 
2-81 

SECT.    I.] 


DEGASIFYING,   GASIFYING,   COMBUSTION. 


.     . 

.      , 

. 

. 

10  rn  nu    s. 

90      nu      . 

195  minutes. 

Sulphuretted  hydrogen 
Carbon  dioxide     

1-30 
2'2I 
2O'IO 

1-42 
2'09 
7.8-7.3 

0-49 
1-49 
52-68 

O'll 

1-50 
67-12 

Carbon  monoxide          .... 

6-19 
C7-78 

5-68 
44'OT, 

3     "u 
6'2I 

•*V?4 

6'12 

22-58 

Heavy  hydrocarbons     .... 
Nitrogen        

IO'62 
2'2O 

S-98 
2'47 

3'04 
2'5S 

1-79 
0-78 

H.  Bunte*  found  the  following  composition  of  the  purified  gas  during  the  dis- 
tillation of  Westphalian  coal  after  the  tenth  period  of  fifteen  minutes : — 


X 

2- 

Carbon  dioxide 

1-8 

2-0 

i  -i 

07 

07 

Heavy  hydrocarbons 

6-0 

4'2 

2-4 

I'4 

I'2 

Carbon  monoxide  . 

8-3 

7'4 

6-8 

6-6 

67 

Hydrogen 

37'i 

48-9 

53'5 

58-2 

6ri 

Methan  ...                                  - 

45  '4 

36'9 

34'2 

29-6 

27-6 

Nitrogen 

I  '4 

0-6 

2'O 

3'5 

27 

The  unpurified  gas  contained  at  the  commencement  4  per  cent,  of  carbonic  acid, 
and  towards  the  end  1-4. 

A  large  part  of  these  products  is  derived  directly  from  the  coal,  and  another  por- 
tion from  the  original  products  as  their  mutual  reaction  increases  with  the  height 
and  the  duration  of  the  temperature.  Ethylene,  e.g.,  is  resolved  into  hydrogen  and 
naphthaline. 

According  to  Berthelot's  researches  methan  forms  ethylene,  propylene,  and  perhaps 
the  entire  series  of  the  polymeric  hydrocarbons  ;  acetylene  yields  benzol  and  a  poly- 
meric series,  (C2H2)B,  &c. 

Watery  vapour  and  carbonic  acid  also  act  upon  coal,  as  mentioned  below. 

There  are  few  complete  analyses  of  purified  gas  known — i.e.,  Heidelberg  gas  by  R. 
Bunsen,  Konigsberg  gas  by  Blochmann,  and  Hannover  gas  by  Dr.  Fischer : — 




Bunsen. 

Blochmann. 

Fine 

ler. 

I. 

II. 

Benzol,  CdH6     . 
Propylene,  CSH8 
Ethylene,  O,H4 
Methan,  CH4     . 
Hydrogen 
Carbon  monoxide 

I  '33 

I  '21 

2  '55 
34-02 
46-20 
8-88 
3-01 
0-65 
2-15 

0-66 
0-72 

2'OI 
35^8 

5275 
4'00 
I'4O 

3-i8 

0-69 

0-37 
2'II 

37*55 
46-27 
H'19 

0-81 
trace 

I  '02 

0'59 
0-64 
2-48 

3875 
47-60 

7H2 
0-48 
O'O2 
2  -O2 

Oxygen 
Nitrogen  . 

The  combustion  value  of  the  components  of  coal-gas  appears  from  the  following 
conspectus  : — 


Water  at  o°  as  Product  of 

Steam  at  20°  as  Product  of 

Mol. 

Combustion. 

Combustion. 

i  Mol. 

i  Cubic  Metre. 

i  Mol. 

i  Cubic  Metre. 

Benzol,  C6H6      . 

78 

790,000 

35,400 

757,600 

34,000 

Propylene,  C,Hd 

42 

501,200 

22,500 

468,800 

21,000 

Ethylene,  C^  . 

28 

333,400 

15,000 

311,800 

I4,OOO 

Methan,  CH4     . 

16 

2I2,OOO 

9,500 

190,400 

8,540 

Hydrogen  . 

2 

68,400 

3,070 

57,600 

2,580 

CO     ... 

28 

68,OOO 

3,050 

68,000 

3,050 

Jahresber.  1887,  p.  97. 


CHEMICAL   TECHNOLOGY. 


[SECT.  i. 


For  i  cubic  metre  of  coal-gas  of  mean  composition  there  results  the  following 
combustion  value  calculated  for  water  at  o°  and  steam  at  20°  as  products  of  com- 
bustion : — 


Composition. 

Combustion  value. 

Water. 
Heat-units. 

Steam  at  20°. 
Heat-units. 

Benzol  

0-8 
07 

2  '3 
36-0 

48-0 

8-0 

283 
157 

345 
3.420 

1.473 
244 

272 

147 
322 

3.074 
1,238 
244 

Ethylene  
Methan  
H  

CO  

5.922 

5.297 

Now,  100  kilos,  of  good  gas-coal  (of  about  8000  heat-units  of  combustion  value) 
with  careful  working  yields  27  to  30  cubic  metres  of  coal-gas,  or  i  kilo,  of  coal  gives 
o'3  cubic  metre  of  gas,  representing  about  1600  heat-units.  The  gas  obtained  on  degasi- 
fying  coals  represents,  therefore,  20  per  cent,  of  the  total  combustion  value  of  the  coal. 

We  have  certainly  as  by-products  from  100  kilos,  of  coal  50  to  70  kilos,  of  coke,  of 
which  from  10  to  25  kilos,  are  consumed  in  heating  the  retorts,  also  tar,  ammoniacal 
liquor,  and  spent  purifying  mass,  the  value  of  all  which  is  very  fluctuating.  If  these 
substances  can  be  successfully  utilised,  the  expense  of  the  production  of  gas  may 
fall  very  low.  This  will  appear  from  a  comparison  of  the  reports  of  the  Cologne  Gas- 
works for  the  financial  years  April  i,  1882-83  an(^  1886-87. 


Total  product 


cubic  metres 


sold 


1882-83. 

13,447,780 
12,387,191 
1,058,489 


Loss  of  gas          ....  „ 

From  100  kilos,  of  Westphalian  coal  there  were  obtained : — 

1882-83. 
298-48 


1886-87. 
16,963,630 
15,605,456 

1,357,374 


6-87. 


Gas     .... 

„    sold 

Coke,  saleable     . 
Tar     .         .         .    ;   v 
Ammonium  sulphate  . 

Outgoings  . 

for  coal 


Coke  . 
Tar      . 
Ammonia    . 
Ammonium  sulphate 


cubic  metres 

kilos, 
is 
» 

marks 
>» 

Receipts : 
marks 


Total 


274-94 

60  roo 

49-00 

9-40 

640,516 
430,440 


255.387 

119,773 

133,693 

19,996 

528,849 


272-19 

620-00 

45  '°4 

lO'OO 

985,126 

575,551 


294,340 
31,988 
91,281 
17,293 

405,602 


Hence  i  cubic  metre  cost  at  the  works,  without  including  interest  and  cost 
of  mains,  in  1882—83  only  0-83  pfennig  (100  pfennige  =  is.) ;  but  in  1886—87  more 
than  3  pfennige.  The  cause  of  this  is  that  in  1882-83  the  receipts  for  the  by- 
products exceeded  the  cost  of  coal  by  nearly  100,000  marks,  but  in  1886-87  ^e^ 
short  of  the  cost  of  coal  by  170,000  marks.  100  kilos,  of  ammonium  sulphate  cost 
in  1882,  40-85  marks,  in  1885  only  22-90  marks;  100  kilos,  of  tar  in  1878  were 
worth  2'3  marks,  in  1883,  5-5  marks,  and  in  1887.  2  marks.  In  1881-82  it  was  even 


SECT,  i.]  DEGASIFYING,   GASIFYING,   COMBUSTION.  41 

found  advantageous  to  burn  20,077  cubic  metres  of  gas  under  the  retorts,  and  thus  to 
sell  the  main  coke.* 

The  value  of  the  by-products  would  probably  fall  still  lower  if  gas  was  generally 
used  as  a  source  of  heat  and  power.  This  would  be  very  difficult,  since  coals  suitable 
for  the  production  of  gas  are  relatively  scarce. 

Generator-gas. — In  order  to  gasify  the  coke  which  remains  after  the  degasification 
of  the  coal,  oxygen  must  be  supplied.  This  may  be  effected  either  with  free  oxygen 
(atmospheric  air)  or  with  combined  oxygen  (water  or  carbonic  acid).  The  following 
reactions  here  come  into  play : — 

1.  For  forming  carbon  monoxide :  C  +  O  =  CO  =  +  29,000  heat-units. 

2.  For  carbon  dioxide  :  C  +  O2  =  C02  =  +  97,000  heat-units. 

3.  For    gasification    with    carbon    dioxide:    C  +  CO2  =  2 CO  =  —97,000+  58,000  = 

—  39,000  heat-units. 

4.  For  decomposition  with  liquid  water :  C  +  H20  =  CO  +  H2  =  —  68,400  +  29,000  — 

—  39,400  heat-units, 

but  only  57,600  +  29,000  =  —  28,600  heat-units  with  watery  vapour  at  about  20°. 

5.  C  +  2H20  =  C02  +  2H2  =  -  136,800  +  97,000  =  -  39,800  heat-units  if  liquid  water 
was  used, 

but  —  115,200  +  97,000  =  —  28,200  with  watery  vapour  at  20°. 

Of  course  the  combustion  value  of  the  gases  formed  =  97,000  heat-units  less  heat  of 
formation.  According  to  the  equation  of  decomposition,  No.  4,  we  obtain,  e.g.,  from 
12  kilos,  carbon  and  18  kilos,  of  water,  28  kilos,  of  carbon  monoxide  and  2  kilos,  of 
hydrogen,  or,  jointly,  68,000  +  68,400  =  97,000  +  39,400  heat-units. 

Consequently,  heat  is  produced  only  on  the  gasification  of  the  carbon  by  free 
oxygen ;  if  combined  oxygen  is  used  heat  is  absorbed,  which  must  be  supplied  from 
without  (on  gasifying  in  retorts)  or  in  the  coal  itself,  by  the  introduction  of  free 
•oxygen  (air).  The  latter  can  take  place  separately  or  simultaneously. 

In  coke-generators  the  gasification  should  be  arranged,  as  far  as  possible,  in 
accordance  with  the  first  equation,  since  the  carbonic  acid  formed  according  to  the 
second  has  no  more  combustion  value.  The  28  kilos,  or  22^3  cubic  metres  of  carbon 
monoxide  formed  on  the  gasification  of  12  kilos,  carbon  have  consequently  a  com- 
bustion value  of  only  68,000  heat-units,  instead  of  the  97,000  heat-units  of  the 
original  coal.  The  29,000  heat-units  are  evolved  in  the  generator,  i.e.,  30  per  cent, 
•of  the  total  combustion  value  of  the  coke  is  likewise  utilised,  if  the  gases  enter  into 
the  fire  at  their  full  heat,  as  is  mostly  the  case  in  the  coke-generators  built  into  the 
retort-ovens  of  gasworks.  But  they  are  entirely  lost  if  the  gas  is  let  cool  down  to 
the  temperature  of  the  air,  as  it  would  be  doubtless  requisite  if  gas  were  universally 
introduced. 

Most  of  the  gas-fires  introduced  industrially  allow  a  part  of  this  heat  to  be  lost.  A 
portion  of  the  heat  is  even  sacrificed,  e.g.,  in  the  Siemens  gas-firing  used  in  glass- 
works, iron  furnaces,  &c.,  in  order  to  obtain  a  simple  and  regular  working. 

Independently  of  gasworks,  we  use  in  general  for  gas-firing,  not  coke,  but  coal. 
The  coals  are  first  degasified,  then  gasified  by  the  introduction  of  atmospheric  oxygen, 
so  as  to  obtain  a  mixture  of  coal-gas  and  coke  generator-gas.  In  Liirmann's  generator 
these  two  processes  are  kept  as  separate  as  possible.  The  coal  is  fed  uninterruptedly 
into  the  retort,  A  (Fig.  35),  by  mechanical  power,  and  pushed  forwards.  By  the 
channels,  D,  escape  the  combustion-gases,  which  pass  away  from  the  fire  still  hot,  in 
order  to  furnish  the  heat  required  for  the  partial  degasifying  of  the  coal.  The  coke 

*  Of  late  years  the  value  of  tar  has  fallen  so  low  that  it  has  been  sometimes  profitable  in  England 
to  burn  the  tar  under  the  retorts  instead  of  selling  it  for  the  manufacture  of  tar  products. — 
[EDITOK.] 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


formed  is  gasified  in  the  shaft,  b,  by  the  atmospheric  oxygen  entering ;  the  gaseous 
mixture  formed  escapes  at  (7. 

In  the  gas-firing  of  Boetius,  as  shown  in  longitudinal  and  transverse  section  (Figs. 
36  and  37),  there  lie  beneath  the  hearth  two  generators,  A.     They  are  formed  by 

inclined    planes,    C,    oblique 

Fig.  35.  gratings,   />,  and   side-walls, 

N,  which  are  contracted  up- 
wards. The  coal  introduced 
at  B  gives  off  its  gas,  the 
coke  is  gasified  upon  the 
grate,  D,  so  that  the  gases 
enter  the  flame-channel,  A", 
at  a  high  temperature.  The 
atmospheric  air  introduced 
through  the  side-channels,  F, 
is  heated  along  the  side- 
walls,  N,  of  the  generator, 
and  in  the  horizontal  chan- 
nels, Ht  enters  by  a  number 
of  lateral  apertures  into  the 
stream  of  gas  ;  the  flame  sur- 
rounds the  pots,  G,  whilst 
the  smoke-gases  escape  by 
small  chimneys,  m. 

The  generator  of  F.  Sie- 
mens is  in  extensive  use.  The  coal  introduced  through  the  shaft,  A  (Fig.  38),  slides 
gradually  down  upon  the  grate,  p  o,  the  slag  formed  is  removed  beneath,  and  the 
mixed  gases  escape  through  the  pipe,  V  U. 

Fig-  36-  Fig.  37. 


According  to  the  kind  of  coal  employed  and  the  manner  of  working,  the  composition 
of  generator-gas  differs.  A  part  of  the  coal-gas  is  decomposed,  since  coals  before  they 
are  degasified  come  in  contact  with  the  instreaming  oxygen,  and  the  gas  is  partially  burnt. 
Thereby  the  heavy  hydrocarbons,  and  especially  the  hydrogen,  are  consumed.  The 
water  formed  is  then  again  more  or  less  completely  decomposed  by  the  ignited  coke.  If 
the  generator  is  worked  hot,  as  is  generally  the  case  if  no  watery  vapour  is  passed  in 
below,  decomposition  sets  in,  whereby  the  proportion  of  the  heavy  hydrocarbons  is  like- 


SECT.    I.] 


DEGASIFYING,  GASIFYING,   COMBUSTION. 


43: 


wise  reduced.     Hence  it  is  intelligible  that  generator-gases  contain  so  little  heavy  hydro- 
carbons (about   o'2    per   cent.),    so  that   it   is 
preferable  not   to  determine   them   separately, 
but  along  with  the  methan. 

This  does  not  complete  the  number  of  the 
possible  transformations.  Watery  vapour  is 
decomposed  by  carbon.  According  to  Naumann 
and  Pistor,  charcoal  is  partially  converted  into 
carbon  monoxide  by  dry  carbon  dioxide  at 
530° -5 60°.  Dry  carbon  dioxide  is  not  reduced 
to  carbon  monoxide  even  at  900°.  The  action 
of  carbon  monoxide  upon  water  begins  at  about 
600°  with  the  formation  of  carbon  dioxide  and 
hydrogen.  But  if  mixtures  of  hydrogen  and 
carbon  monoxide  are  heated  with  insufficient 
proportions  of  oxygen,  then,  according  to  the 
experiments  of  R.  Bunsen,  decidedly  more 
hydrogen  is  burnt  than  carbon  monoxide,  so 
that  the  affinity  of  oxygen  for  hydrogen  is 
greater  than  for  carbon  monoxide.  The  pro- 
cesses in  the  generator  are  therefore  very  com- 
plicated, and  but  partially  known. 

The  gases  from  the  collecting-channels  of  eight  Siemens  generators  at  Essen  have^ 
according  to  the  author's  experiments,  the  following  composition  :— 


J 

II. 

III. 

IV. 

V. 

Mean. 

CO2       .                           ....,]      6-99 

5-50 

5-89 

3  '96 

4-04 

5'3) 

CO                                  .        .               22-84 

26-01 

22  '6  1 

24-02 

23-01 

237  r30'9 

Methan                          .        .           '••      2-99 

2-46 

I'39 

1-63 

0-92 

1-9) 

H  .        .                         .        .               10-30 

8-02 

5-50 

4-83 

3-92 

6-5 

N.        .                         .        .           |    56-88 

58-01 

64-61 

65-56 

68  -i  i 

62-6 

One  kilo,  of  coal  gave  4*52  cubic  metres  of  generator-gas  ;  i  cubic  metre  of  this  had 
a  combustion-value  of  1053  heat-units;  consequently,  the  4/52  cubic  metres  had  4760 
heat-units,  whilst  the  coal  expended  had  a  combustion  value  of  7950  (steam  at  20°). 
The  gas,  when  cooled  down  to  the  temperature  of  the  air,  contained,  therefore,  only 
60  per  cent,  of  the  combustion  value  of  the  coal,  the  rest  having  been  expended  on 
heating  the  gas. 

We  lose  here,  therefore,  not  merely  the  considerable  quantities  of  heat  which  the 
exposed  generators  give  off  by  conduction  and  radiation,  but,  further,  850  heat-units 
for  each  kilo,  of  coal  which  the  long  channel  gives  off,  whilst  only  about  140  heat-units 
of  the  specific  heat  of  the  gas  are  led  to  the  fire ;  together,  4900  heat-units.  This 
loss,  if  coal  is  not  very  dear,  is  amply  compensated  by  the  simplification  and  the  in- 
creased certainty  and  uniformity  of  working. 

The  gasification  of  carbon  by  carbon  dioxide  occurs  only  as  an  auxiliary  reaction,  in 
order  to  re-convert  the  carbon  dioxide,  formed  in  the  generator,  into  carbon  monoxide. 
In  gasifying  carbon  by  watery  vapour  there  are  required  almost  exactly  the  same 
quantities  of  heat  whether  CO  +  H2  or  CO2  +  2Ha  are  produced.  Of  course  the  gaseous 
mixtures  have  almost  the  same  combustion  value  if  referred  to  liquid  water. 

According  to  equation  4  the  decomposition  of  18  kilos,  of  watery  vapour  at  20°  re- 
quires 28,600  heat-units.  This  circumstance  comes  into  play  in  every  generator,  as 
the  atmospheric  air  introduced  always  contains  watery  vapour.  It  had  been  observed 
long  ago  that  by  letting  water  into  the  ash-pit,  especially  in  coke  generators,  the  grates 


44 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


and  the  masonry  of  the  generator  are  preserved,  and  the  removal  of  slag  is  often 
facilitated.  In  consequence,  water  or  steam  is  often  introduced  under  the  grate 
of  the  generator.  If  the  generator  is  walled  directly  into  the  retort  furnace,  this  intro- 
duction of  heat  certainly  involves  a  loss ;  the  higher  the  temperature  of  the  escaping 
gases,  the  greater  this  loss.  Every  18  kilos,  of  water  decomposed  in  the  generator 
carry  away,  according  to  equation  4,  39,400  heat-units,  which  the  hydrogen  formed 
certainly  liberates  on  combustion.  But  the  reconstituted  water  carries  off  as  steam  of 
1000°  about  20,000  heat-units,  and  if  heat  reservoirs  (regenerators)  at  500°  are  used, 
there  is  still  a  loss  of  about  1500  heat-units.  Whether  this  loss  is  compensated  by  the 
advantages  depends  on  local  conditions  ;  in  general  this  will  not  be  the  case.  But  if 
the  watery  vapour  introduced  is  generated  by  the  heat  of  the  escaping  combustion- 
gases  (which  would  otherwise  be  wasted)  the  loss  will  be  smaller  by  11,000  or  12,000 
heat-units.  It  would  entirely  disappear  only  if  watery  vapour,  produced  without 
expense,  could  be  introduced  into  the  generator  at  the  same  temperature  at  which  the 
combustion-gases  pass  away. 

The  introduction  of  watery  vapour  appears  more  favourable  when  the  generator  is 
at  a  distance  from  the  place  of  its  application,  so  that  a  part  (greater  or  smaller)  of  the 
specific  heat  of  the  gas  produced  is  given  off  to  its  surroundings.  If  the  gas  before  use 
is  cooled  down  to  the  temperature  of  the  air,  its  higher  combustion  value  seems  in  the 
first  place  an  immediate  gain,  but  this  becomes  the  smaller  the  higher  the  tem- 
perature at  which  the  products  of  combustion  escape,  and  the  less  is  the  refrigeration 
of  the  generator-gas.  The  introduction  of  watery  vapour  into  the  generators  cannot, 
hence,  be  universally  recommended,  as  in  most  cases  it  is  connected  with  loss  of  heat. 
Whether  this  waste  is  compensated  by  other  advantages  must  depend  on  local  circum- 
stances. 

Attempts  have  not  been  wanting  to  use  generator- gases  rich  in  hydrogen  for  the 
Fig.  39.  Fig.  40. 


production  of  heat  and  power.     This  idea  has  been  recently  practically  realised  by 
Dowson.     The  generator, «  (Figs.  39  and  40),  has  a  double  jacket,  b,  into  which  water 


SECT.   I.] 


WATER-GAS. 


45 


Fig.  41. 


is  driven.  That  part  of  the  inner  jacket  exposed  to  the  greatest  heat  is  lined  with 
a  fire-resisting  material,  c.  From  the  lower  part  of  the  space,  b,  the  water  flows  to 
the  lower  part  of  the  heating-worm,  d,  which  is  heated  by  a  fire,  and  in  which  steam 
is  constantly  evolved.  A  part  of  this 
steam  passes  through  the  pipe  e  to  the 
space,  6,  above  the  level  of  the  water 
which  it  contains.  The  other  part  of 
the  steam  goes  to  the  blast,  /,  through 
which  a  mixture  of  air  and  steam  is 
blown  into  the  fire  of  the  gas  generator. 
The  pressure  of  steam  in  b  compels  the 
water  under  pressure  to  flow  towards 
the  heating-worm,  d ;  the  pressure  in  b 
can  be  regulated  by  a  valve.  The 
Backet  of  the  space,  b,  is  covered  with 
any  bad  conductor  of  water.  The  heat- 
ing-worm, d,  is  also  fitted  with  a  jacket, 
the  lower  part  of  which,  enclosing  the 
worm,  is  screwed  to  the  upper  part,  so 
that  the  worm  may  be  easily  removed. 
The  gas  coming  from  the  generator 
passes  through  the  pipe  g  into  the  closed 
scrubber,  h,  partly  filled  with  water,  into 
which  the  pipe  g  dips,  so  as  to  be  discon- 
nected from  the  gas  in  the  gas-holder, 
and  to  wash  the  gas  coming  from  a  on 
its  way  to  the  gas-holder.  The  scrubber 
is  divided  into  two  parts  by  a  partition, 
which  has  an  opening  for  the  water, 
near  the  bottom.  The  one  compartment 
receives  the  pipe  g  and  a  pipe  i  (Figs.  39 
and  41),  the  latter  of  which  leads  to  the 
bottom  of  the  scrubber  j.  The  gas 

passes  through  i  into  j,  and  ascends  through  the  charge  of  coke  into  the  gasometer,  k. 
From  here  it  passes  through  the  pipe  downwards  into  the  second  compartment  of  the 
scrubber  h,  whence  it  passes  by  another  pipe  to  the  place  of  its  destination.  The  coke 
which  fills  the  scrubber  j  is  kept  moist  by  water,  which  is  conveyed  by  the  tube  in  to 
thexradial  tubes,  n,  fitted  with  perforations.  The  water  trickles  through  the  coke, 
and  flows  through  i  to  the  scrubber  h,  whence  it  is  carried  out  by  the  overflow,  o 
(Fig.  40).  Instead  of  taking  the  water  which  is  to  be  evaporated  in  the  worm,  d,  from 
the  jacket,  b,  of  the  generator,  it  may  be  effected  through  the  vessel  placed  above  the 
worm,  d. 

Water-gas. — That  steam  passed  over  ignited  coals  forms  hydrogen  along  with  carbon 
dioxide  and  monoxide  has  long  been  known.  Hence  the  attempt  has  often  been  made 
to  heat  charcoal,  coke,  or  anthracite  in  retorts,  upright  or  horizontal,  and  there  to 
introduce  steam.  As  carbonic  acid  was  principally  formed  along  with  hydrogen,  it 
\vas  sought  to  remove  the  former  by  means  of  milk  of  lime  or  caustic  soda.  Such  a 
gas  has  been  used  at  Narbonne  for  lighting,  but  the  process  has  everywhere  been 
abandoned  as  not  economical. 

In  order  to  render  the  water-gas  process  practicable,  there  were  used,  instead  of 
retorts  heated  from  without,  shaft  furnaces  into  which  air  and  watery  vapour  were 
blown  alternately.  Such  were  the  arrangements  of  Lowe,  Strong,  Dwight,  and  others, 


46 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


in  use  in  many  cities  of  North  America.    The  process  was  adapted  to  European  con- 
-ditions  by  Schulz,  Knaudt  &  Co.,  of  Essen. 

According  to  the  arrangements  at  Essen  and  Witkowitz  (V,  Figs.  42  to  44),  the 

Fig.  42.  Fig.  43. 


JJ 


,4rbeitsplatte 

Nach  dent  Gasbehalter 


Explanation  of  Terms. 

Working  floor. 
Scrubber. 

Pipe  leading  to  the 
gasometer. 


Wasstryekiiklter  Schieber 
Windleitung 
Wasserverschluss 
Nach  den  Kesseln 


Generator. 

Slide  cooled  by  water. 

Air-duct. 

Water-joint 

Duct  leading  to  boilers* 


steam,  which  can  be  regulated  by  a  sliding  valve,  enters  at  D,  a  generator  filled  with 
coke.  The  water-gas  formed  is  led  off  below.  The  slide,  S,  kept  cool  by  water,  closes 
the  air- channel  as  scon  as  the  gas-channel  is  open,  and  inversely.  In  the  same  manner 


SECT.    I.] 


WATER-GAS. 


44. 


AnsiM  da  \  \  Stemming 


zum 


the  valve,  d,  fixed  in  the  air-pipe  below  the  point  where  the  air  enters  W  is  closed  as 
soon  as  the  gas-pipe  is  open.  Thus,  the  air  is  doubly  shut  off  to  prevent  explosions. 
If  the  surfaces  of  the  slide  fit  loosely,  the  small  quantity  of  detonating  gas  puffs  out  at 
the  openings,  a.  In  Witkowitz,  during  the  hot  blast,  the  upper  part  of  the  slide  is  fixed 
so  that  the  air- pipe  is  connected  with  the  generator,  the 
throttle-valve  is  open,  and  the  gas-valve  of  the  generator, 
G  ;  the  pipe  through  which  the  gas  passes  to  the  scrubber 
and  the  slide-valve,  F,  are  closed.  Whilst  the  gas  is 
being  made,  G  and  d  are  closed ;  the  upper  part  of  the 
slide  shuts  off  the  airway,  and  establishes  the  connection 
from  the  generator  to  the  scrubber;  F  is  opened.  The 
connection  between  the  gasometer  and  the  generator  is 
then  disturbed  only  by  the  water-joint,  w,  in  the  scrubber, 
which  amounts  to  100  mm.  Upon  the  slide,  S,  there  are 
screwed  two  uprights,  on  which  is  fixed  an  axle,  3Sr  This 
axle  is  connected  with  the  driving  axle,  sjg2.  The  levers 
upon  $£gt  move  the  upper  part  of  S,  and  effect  the  opening 
and  shutting  of  d  and  of  the  slide  in  F.  A  lever  wedged 
upon  j>2}2  effects  the  opening  and  shutting  of  the  gas- 
valve  of  the  generator ;  *JJj2  is  turned  by  the  hand  wheel, 
//.  The  arrangement  is  such  that  by  turning  H  to  one 
side  the  upper  part  of  S  shuts  the  airway  and  opens  the 
gasway.  At  the  same  time  d  and  G  are  closed  and  the 
slide  of  F  is  opened.  By  turning  to  the  other  side,  the 
upper  part  of  S  closes  the  gas-channel  and  opens  the  air- 
channel;  at  the  same  time  d  and  G  are  opened  and  the 
slide  of  F  is  closed.  The  workman  has  therefore  merely 
to  turn  the  wheel,  H,  to  correspond  in  order  to  set  the 
apparatus  either  for  "  gas-making  "  or  "  hot-blowing,"  and 
no  accident  can  happen  from  his  inattention.  At  Wit- 
kowitz two  generators  are  in  action,  each  holding  10  cubic 
metres.  Alternately  steam  is  blown  in  for  five  minutes 
("  gas-making  ")  and  for  ten  minutes  there  is  hot-blowing, 
i.e.,  air  is  forced  in.  The  generator-gas  (Siemens-gas) 

obtained  on  hot-blowing  is  burnt  under  four  steam  boilers,  and  the  water-gas  is  used 
for  heating  the  Siemens-Martin  furnaces. 

For  larger  installations  it  is  more  advantageous  to  connect  each  two  generators  with 
a,  scrubber  and  a  dust-collector  (Figs.  44  and  46). 

The  generator-gas  made  at  Essen  produced  3690  cubic  metres  water-gas  (July  21, 
1887),  and  consumed  3256  kilos,  coke.     The  composition  of  the  coke  was — 

.    84-8 


Ansicht  der  Stetterunff  gum  Gene- 
rator =  Connection  of  the 
scrubber  with  the  generator. 


C  . 
H  . 
NO 
Ash 
Water 


2-1 

io-6 

2-0 


The  generator-gases  had  the  following  mean  composition  : — 

6 
4-03 

28-44 
0-39 
2  '2O 

64-94 


C02 
CO 

Methan 
H  . 

N  . 


In  i 

7-04 
23-68 

0-44 

2-95 
65.89 


10  Min. 
I -6O 

32-21 
O'l8 
2-JI 

63-90 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


Determinations  of  carbonic  acid  effected  at  the  generator  gave  1*5  to  7*2  per  cent. 
The  gases  would  have  contained  less  carbonic  acid  if  the  blast  had  been  less  strong, 
i  cubic  metre  of  these  gases  has  a  mean  combustion- value  of  950  heat-units  and 
contains  0718  kilo,  carbon.  The  temperature  of  the  gases  rose  to  505°.  After  making 


Fig.  45- 


SdinittAB-CV-EF. 


Explanation  of  Terms. 
Section  AB— CD— EF. 


StaubsammUr 


Scrubber. 
Generator. 
Dust  chamber. 


Wasseryas 
Windsammler 


Siemens-gas. 
Water-gas. 
Air  chamber. 


gas  respectively  for  one,  two  and  a  half,  and  four'  minutes,  the  water-gas  had  the 


following  mean  composition  : 


C02     . 
CO      . 

Methan 
H 

N 


In  i 

1-8 

45'2 

I'l 

44-8 
7-1 


2'5 

3-0 

44  -6 

0-4 

48-9 


4  Min. 

5-6 
40-9 

O'2 

51-4 


i  kilo,  of  coke  yielded  1*13  cubic  metre  of  water-gas,  representing  2970  heat-units, 
and  containing  1*13  x  0*477  x  °'5395  =  0*291  carbon.  The  remaining  0*557  kilo,  of 
carbon  yielded  3*13  cubic  metres  of  generator -gas.  Of  the  7000  heat-units  of  the  coke 
there  are  found  in  the  \ 


Water-gas 
Generator-gas 


2970  heat-units  =  42  per  cent. 
2970          „         =  42 


At  Essen,  to  a  small  extent  at  Sulzer,  and  in  some  other  places  water-gas  is  used 
to  give  light  by  means  of  Fahnehjelm's  magnesium  burner.     Taking  the  cost  of  the 


SECT. 


I.] 


WATER-GAS. 


49 


mains  into  account,  the  price  of  water-gas  would  in  many  places  be  higher  than  that 
of  coal-gas,  but  in  others  lower — lower  even  than  petroleum. 

Water-gas  may  find  extensive  application  in  metallurgical  operations,  in  chemical 
works,  and  in  the  laboratory,  especially  as  it  has  the  advantage  of  not  depositing  soot 
on  the  apparatus  to  be  heated,  and  of  giving  out  a  higher  temperature. 

Fig.  46. 
GrwtdriR. 


-•f 


StaubsbmjnZer. 


Explanation  of  Terms. 
GROUND  PLAN. 


Zum  Gasometer 


Scrubber 
Generator 


Pipe  leading  to — 
Gasometer. 
Scrubber. 
Generator. 


Staubsammler 
Siemens  Leitung 

Windsammler 


Dust  chamber. 
Siemens-conduc- 
tion. 
Air-collector. 


The  use  of  water-gas  will  become  more  general  as  soon  as  it  is  produced  from  coal 
instead  of  coke,  since  it  appears  irrational  first  to  coke  the  coal  in  a  separate  apparatus. 
A  remunerative  production  of  ammonia  is,  however,  scarcely  practicable  in  the  direct 
production  of  generator-gas  and  water-gas  from  coal,  and  that  of  tar  (even  at  improved 
prices)  seems  out  of  the  question. 

Whilst  i  kilo,  of  the  best  coal  gives  at  the  most  o-3  cubic  metre  of  illuminating  gas, 
we  obtain  from  i  kilo,  of  common  coke  1*13  cubic  metre  of  water-gas  and  3' 13  cubic 
metres  of  generator-gas,  which  together  contain  84  per  cent,  of  the  combustion  value  of 
the  coke  used.  If  the  coal  is  partially  degasified,  then  at  once  gasified,  and  the 
luminous  gas  mixed  with  the  water-gas,  we  have  a  gas  containing — 

Heavy  hydrocarbons  i  per  cent. 

Methan     .......       8 

Hydrogen 

Carbon  monoxide     .... 

Carbon  dioxide          .... 

Nitrogen 

and  having  a  combustion  value  of  about  3250  heat-units  per  cubic  metre.  Along  with 
this  richer  gas  we  have  as  by-products  tar,  ammonia,  and  cyanogen,  as  in  common  coal- 
gas,  and  the  corresponding  proportion  of  generator-gas,  as  in  the  ordinary  water-gas 
process.* 

*  The  great  objection  to  water-gas  has  been  its  dangerous  character.  As  will  be  seen  from 
the  above  analysis,  it  contains  from  30  to  upwards  of  40  per  cent,  of  the  fearfully  poisonous  con- 

D 


48 

37 
3 
3 


50  CHEMICAL  TECHNOLOGY.  [SECT.  i. 


HEATING      ARRANGEMENTS. 

If  wood,  peat,  lignite,  or  coal  is  heated,  it  is  degasified  in  the  manner  already 
described.  If  atmospheric  oxygen  is  present,  and  if  the  temperature  is  sufficiently  high, 
the  gases  take  fire  and  burn  with  a  luminous  flame.  The  residual  charcoal  or  coke  does 
not  burn  with  a  flame,  but  glows,  the  combustion  taking  place  only  on  the  surface.  If 
the  air,  after  its  oxygen  has  been  completely  converted  into  carbonic  acid,  remains  in 
contact  with  the  fuel,  and  if  the  temperature  is  sufficient,  the  carbonic  acid  (carbon 
dioxide)  takes  up  another  atom  of  carbon,  C02  +  C  =  2CO,  and  forms  carbonic  oxide 
(carbon  monoxide). 

In  our  ordinary  fires,  domestic  or  industrial,  these  processes  take  place  simultane- 
ously. To  effect  complete  combustion  there  is  required  a  sufficient  supply  of  oxygen  (or 
air)  and  a  sufficient  temperature. 

If  oxygen  is  deficient,  the  combustion  is  imperfect ;  from  the  charcoal  or  coke  there 
is  formed  carbon  monoxide  (a  colourless  gas) ;  the  gas  produced  on  the  degasifying  of 
wood  or  coal  gives  a  smoky  flame,  as  the  hydrogen  combines  with  the  oxygen  by  prefer- 
ence, so  that  the  heavy  hydrocarbons  and  the  other  constituents  of  tar  liberate 
more  or  less  free  carbon.  If  undecomposed  particles  of  tar  escape  along  with  the  soot, 
it  becomes  adhesive,  attaches  itself  to  solids,  and  has  a  very  unpleasant  smell.  If  a  fire 
is  to  be  smokeless,  the  complete  combustion  of  the  gases  and  the  accompanying  tarry 
vapours  must  be  effected ;  degasified  fuel  burns  without  smoke. 

For  the  complete  combustion  of  the  volatile  matter,  especially  the  tar,  a  sufficient 
temperature  is  necessary.  As  this  is  lowered  by  the  immediate  withdrawal  of  heat  by 
cold  surfaces,  water,  and  superfluous  air,  the  mixture  of  gases  or  vapours  to  be  burnt  must 
not  before  complete  combustion  come  in  contact  with  cold  surfaces  (stoves  should  be 
lined  with  fire-clay  or  stone,  not  with  iron),  and  the  fuel  must  be  employed  as  dry  as 
possible  (coal  should  not  be  moistened).  It  follows  that  the  numberless  proposals  for 
the  combustion  of  smoke  are  useless.  The  formation  of  smoke  can  be  prevented,  but 
smoke,  when  once  formed,  is  so  hard  to  burn  that  the  task  may  be  pronounced  practically 
impossible. 

Gas  Analysis. — A  correct  estimate  of  a  firing  can  be  effected  only  on  the  basis  of 
.gas  analysis.  With  the  following  apparatus,  made  by  W.  Apel,  mechanician  to  the 
University  of  Gb'ttingen,  the  author  has  executed  thousands  of  gas  analyses. 

The  lower  part — holding  45  c.c. — of  the  burette,  A  (Fig.  47),  used  for  measuring 
the  gas  under  examination,  which  is  enclosed  in  a  wide  cylinder  filled  with  water  in 
order  to  obviate  fluctuations  of  temperature,  is  divided  into  tenths  of  a  c.c.,  but  the 
upper  part  is  graduated  only  into  entire  c.c.  The  thick  glass  capillary  tube  with 
the  glass  cocks  is  fastened  at  both  ends  at  i  in  a  section  of  the  partition,  and  at  o  in  a 

stituent,  carbon  monoxide,  which,  in  good  coal-gas,  does  not  exceed  8  per  cent.  Hence  a  very 
slight  escape  is  sufficient  to  prove  fatal.  Two  men  at  Leeds  lost  their  lives  from  accidentally 
inhaling  air  thus  contaminated,  and  even  the  medical  men  commissioned  to  make  an  autopsy  of 
the  bodies  were  rendered  seriously  ill.  The  danger  is  the  greater  as  water-gas  is,  per  se,  inodorous, 
so  that  a  leakage  is  not  detected  as  rapidly  as  is  the  case  with  ordinary  coal-gas.  For  this  evil  a 
remedy  has  been  devised  by  Mr.  W.  Crookes,  F.R.S.,  and  Mr.  F.  I.  Ricarde-Seaver,  F.R.S.E.  The 
process,  which  is  simple  and  inexpensive,  is  fully  described  in  their  patent,  No.  10,164  of  1889. 
They  cause  the  water-gas,  as  at  present  produced,  to  pass  at  red  heat  over  a  mixture  of  caustic 
soda  and  quicklime.  The  water  in  the  soda  is  decomposed,  its  oxygen  going  to  the  carbon  mon- 
exide  and  converting  it  into  carbonic  acid,  which  latter  instantly  unites  with  the  soda  and  lime, 
while  the  hydrogen  is  liberated  and  takes  the  place  of  the  carbon  monoxide  in  the  water-gas. 
The  mixture,  when  spent,  can  be  revivified  by  dissolving  out  the  carbonate  of  soda  with  water  and 
causticising  it  afresh  in  the  ordinary  manner.  The  poisonous  character  of  the  gas  is  thus  entirely 
removed  without  injury  to  its  combustion  value,  and  it  can  be  easily  enriched  if  required  for 
illuminating  purposes. — [EmTOB.] 


SECT;     I.] 


GAS   ANALYSIS. 


small  support  in  the  cover  of  the  box.  The  four  glass  cocks  close  perfectly,  and  never 
stick  fast  if  handled  in  an  intelligent  manner.  The  cock  tube  is  bent  round  at  its  front, 
and  connected  with  the  U-tube,  B,  the  limbs  of  which  contain  cotton-wool,  whilst  there 
is  a  little  water  in  the  lower  bend,  in  order  to  keep  back  any  soot  or  dust,  and  to  satu- 
rate the  aspirated  gas  with  water  before  it  is  measured.  The  end  of  the  three-way 
cock  which  is  turned  backwards  is  connected  by  a  caoutchouc  tube  with  the  caoutchouc 

Fig.  47- 


sucker,  C,  by  means  of  which  it  is  easy  to  fill  the  gas  entrance  tube  and  B  with  the 
gases  to  be  examined.  The  combination  of  the  gases  takes  place  in  the  U-shaped  vessels, 
D,  E,  and  F,  fixed  below  in  notches  and  connected  by  short  caoutchouc  tubes  with  the 
cock  tube,  and  filled  with  glass  tubes  to  increase  the  surfaces  of  contact.  As  the  mark 
m  is  above  this  point  of  connection,  it  is  always  moistened  with  the  liquid  concerned, 
and  is  thus  easily  kept  perfectly  tight.  The  other  end  of  the  U-tube  is  closed  with  a 


52  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

caoutchouc  stopper  containing  a  small  glass  tube,  x ;  the  small  tubes  are  connected  in 
common  with  a  slack  caoutchouc  ball,  holding  about  200  c.c.  to  keep  off  oxygen. 

When  the  apparatus  is  to  be  used,  the  cylinder  inclosing  the  burette,  A,  and  the  flask, 
L,  are  first  filled  with  distilled  water.  To  fill  the  three  absorption  bottles,  the  stoppers 
with  the  glass  tubes,  x,  and  the  caoutchouc  ball,  G,  are  taken  off,  and  there  is  poured 
into  D  about  no  c.c.  potassa-lye  of  sp.  gr.  1*20  to  1-28,  so  that  it  is  about  half  full. 

Further,  we  dissolve  18  grammes  pyrogallol  in  40  c.c.  hot  water,  70  c.c.  of  potassa- 
lye  of  the  above  strength  are  added,  and  the  mixture  is  poured  into  E,  to  take  up 
oxygen.  For  determining  carbon  monoxide,  we  place  beforehand  35  grammes  copper 
chloride  with  200  c.c.  of  strong  hydrochloric  acid  and  a  few  clippings  of  sheet-copper  in 
a  well-stoppered  bottle,  and  let  them  stand  for  two  days  with  frequent  shaking;  120  c.c. 
of  water  are  added,  and  the  vessel  F  is  charged  from  this  solution.  The  three  glass 
cocks  are  closed,  the  cock  c  is  set  vertically,  and  the  bottle  L  is  lifted  up  so  that  the 
water  fills  the  burette,  A,  the  cock  c  is  turned  a  quarter  to  the  left  so  that  the  second 
aperture  leads  to  the  tube  B,  the  cock  of  D  is  opened,  the  bottle  L  is  lowered,  and  the 
pinch-cock  fixed  upon  the  tube  s  is  cautiously  opened  so  that  the  potassa-lye  rises  to 
the  mark  m  when  the  cock  is  closed.  In  like  manner  the  liquids  of  the  two  other 
vessels  are  drawn  up  to  the  mark  m,  keeping  the  eye  constantly  fixed  upon  the  ascend- 
ing liquid.  The  three  stoppers  with  the  glass  tubes,  x,  are  then  inserted  air-tight. 
Into  the  tube  B  there  is  first  poured  a  little  water,  both  limbs  are  loosely  filled  with 
cotton-wool,  the  stoppers  are  re-inserted,  and  the  little  tube,  n,  is  connected  by  a  caout- 
chouc tube  with  the  glass  tube,  or  at  high  temperatures  with  the  porcelain  tube,  which 
is  luted  with  clay  air-tight  into  the  chimney,  &c.,  in  order  to  prevent  the  access  of 
atmospheric  air. 

To  ascertain  if  the  apparatus  is  air-tight,  the  cock  c  is  placed  vertically,  the 
caoutchouc  pipe  is  pressed  closely  to  the  tube  in  the  chimney  either  with  the  pinch- 
cock  or  with  the  hand,  and  the  pinch-cock  of  s  is  opened.  The  water-column  in  A 
sinks  a  little,  but  it  must  then  remain  standing  immovably.  A  continued  slow 
sinking  must  be  remedied  either  by  fitting  the  caoutchouc  pipe  more  closely,  or 
pressing  in  the  stoppers,  or  lubricating  the  glass  taps  with  vaselin  mixed  with  a  little 
paraffine. 

After  the  burette,  A,  has  been  filled  with  water  up  to  the  mark  100,  by  lifting  the 
bottle  L,  the  cock  c  is  placed  so  that  the  connection  of  the  aspirator,  C,  with  the 
chimney  is  established  through  the  tube  B,  suction  is  effected  by  pressing  C  ten  to 
fifteen  times,  until  the  entire  channel  is  filled  with  the  gases  in  question.  This  is 
best  effected  by  pressing  C  with  the  left  hand,  closing  the  tube  r  with  the  thumb  of 
the  right  hand,  letting  the  ball  expand  by  opening  the  left  hand,  raising  the  thumb, 
compressing  C  again,  and  so  on  until  the  object  is  effected.  The  cock  c  is  then  again 
set  vertically,  the  pinch-cock  of  s  is  opened,  and  the  bottle  L  is  lowered,  so  that  the 
burette,  A,  is  filled  to  o°  with  the  gases  to  be  examined ;  thereupon  c  is  again  closed 
by  turning  it  a  quarter  to  the  left.  The  gas  is  now  shut  in  between  the  four  glass 
cocks  and  the  column  of  water  in  A. 

For  determining  the  carbon  dioxide,  the  cock  of  D  is  opened,  and  L  is  raised  with 
the  left  hand,  so  that  on  opening  the  pinch-cock  at  s  with  the  right  hand  the  gas  passes 
over  into  D,  L  is  lowered  again  until  the  potassa-lye  in  D  reaches  to  the  junction  of 
the  flexible  tube  under  m,  and  the  gas  is  once  more  driven  into  the  potassa  vessel  by 
raising  L.  On  lowering  L  and  cautiously  opening  the  pinch-cock,  the  potassa-lye  is 
again  allowed  to  rise  to  the  mark  m,  the  glass  cock  is  closed,  the  pinch-cock  is  opened, 
the  bottle  L  is  held  close  to  the  burette  so  that  the  water  in  both  vessels  stands  at  an 
equal  height,  the  pinch-cock  is  again  closed,  and  the  residual  volume  is  read  off. 
The  level  of  the  water  shows  directly  the  percentage  of  the  carbonic  acid  by  volume  in 
the  gas.  In  the  same  manner  the  gas  is  passed  two  or  three  times  into  E,  until  no 


SECT.    I.] 


GAS   ANALYSIS. 


53 


Fig.  48. 


further  decrease  of  volume  ensues ;  the  reading  gives  the  joint  volume  of  carbon 
dioxide  and  oxygen,  whilst  carbon  monoxide  is  further  absorbed  by  a  similar  treatment 
in  F.  In  ordinary  fires  it  is  generally  needless  to  examine  for  carbon  monoxide  if  a 
few  per  cents,  of  oxygen  have  been  found. 

When  the  analysis  is  thus  completed  the  cock  c  is  again  placed  horizontally,  L  is 
lifted,  the  pinch-cock  is  opened,  and  the  water  is  let  flow  up  to  100  in  the  burette,  c  is 
again  set  vertically,  the  channel  is  again  filled  with  the  gas  by  means  of  C,  and  a  fresh 
determination  is  made.  If,  as  is  usual,  no  carbon  monoxide  is  present,  with  a  little 
experience  it  will  be  found  practicable  to  effect  every  five  minutes  an  analysis  accurate 
to  one-tenth  per  cent. 

If  after  100  to  200  analyses  the  absorption  becomes  sluggish,  the  vessels  are 
emptied  by  means  of  a  siphon,  rinsed  with  distilled  water,  and  filled  anew  as  before. 
If  by  inattention  the  absorption  liquid  should  rise  in  the  cock-tube,  the  bottle  L  is 
raised,  the  pinch-cock  opened,  and  the  solution 
is  thus  rinsed  back  into  the  vessel  by  the  dis- 
tilled water.  If  this  is  not  quite  successful, 
the  flexible  pipe,  a,  is  taken  off  the  cock  c,  the 
latter  is  turned  half  way  round,  and,  by  lifting 
L,  water  is  let  flow  through  the  cock-tube  and 
the  cock  c  (the  others  are  closed)  until  perfectly 
clean.  If  the  water  in  the  burette  becomes  im- 
pure, it  must  be  changed.  Before  putting  the 
apparatus  away  all  the  glass  cocks  must  be 
lubricated  afresh  with  vaseline. 

If  in  examining  water-gas  or  generator-gas 
we  wish  also  to  determine  hydrogen  and  methan, 
we  may  connect  the  apparatus  above  described 
without  a  mercurial  trough,  as  follows : — The 
working-tube,  A  (Fig.  48),  is  closed  below  with 
a  caoutchouc  stopper  having  a  glass  tube,  g  (not 
too  narrow),  which  is  fixed  at  v  to  the  bottom 
plate,  and  connected  with  a  bottle  of  mercury, 
F,  by  means  of  a  strong  flexible  tube  with  a 
screw   pinch-cock.     The  platinum  wires  above 
are  fused  in  for  electric  ignition.     The  measur- 
ing-tube, M,  and  the  pressure-tube,  D,  are  like- 
wise connected  with  the  bottle  L  by  means  of 
a  glass  tube  and  a  flexible  pipe  inserted  by  a 
caoutchouc  plug  and   secured   to   the   bottom 
plate.      It  is  advisable  to 
fix  a  small  brass  cap  round 
the  point  of  connection,  e, 
since     it     may    otherwise 
happen  that,  on  exploding 
the    gaseous    mixture    by 
means    of     an     induction 
spark,  the  caoutchouc  con- 
nection may  spring  off. 

In  executing  the  analy- 
sis, the  tubes  A,  M,  D  (the 

latter  up  to  O),  are  filled  with  mercury  by  raising  the  two  bottles,  the  pinch-cocks  on 
the  flexible  pipes  and  the  three  glass  cocks  are  closed,  so  that  the  end  of  the  pipe  a 


54 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


remains  filled  with  water  (or  mercury),  one  of  the  drawn-out  ends  of  the  glass  globe  con- 
taining the  sample  of  gas  is  introduced,  the  point  is  broken  off  within  the  flexible  pipe, 
the  other  end  is  plunged  into  water  and  its  point  also  is  broken  off,  the  cock  d  is  turned 
so  as  to  make  connection  with  the  tube  A,  and  the  sample  of  gas  is  sucked  over  to  A  by 
lowering  the  mercury  bottle,  F.  The  cocks  d  and  h  are  now  turned  round  90°,  and  the 
needful  quantity  of  gas  is  forced  into  the  measuring-tube,  M,  by  raising  the  mercury 
bottle,  F,  and  lowering  the  other  bottle,  L.  If  there  is  contained  in  the  tube  A  a  residue 
of  gas  and  any  water  which  has  been  drawn  over,  they  are  forced  outwards  by  the  cock  d. 
The  sample  of  gas  is  measured,  0*6  to  o'8  c.c.  of  potassa-lye  are  introduced  into  the  tube 
A  through  the  funnel,  t,  the  sample  of  gas  is  passed  over  from  M  and  A,  and,  after  the 
carbon  dioxide  has  been  absorbed,  again  to  M.  The  potassa-lye  is  only  allowed  to  rise 
to  a  mark  immediately  before  d,  which  can  be  seen  during  the  calibration  of  the  tube. 
When  the  carbonic  acid  has  been  determined  and  the  presence  of  oxygen  tested  with 
pyrogallol,  the  tube  A  must  be  carefully  cleansed  up  to  the  cock  d,  as  otherwise  after 
the  explosion  a  part  of  the  carbonic  acid  formed  is  immediately  dissolved  and  the  con- 
traction is  thus  rendered  great.  This  is  effected  by  pouring  about  5  c.c.  water  into  the 
funnel,  t,  lowering  the  bottle  F,  and  then  lifting  it  so  that  the  liquid  flows  off  through 
the  flexible  pipe,  a,  into  a  bottle  connected  by  means  of  a  short  glass  tube  and  a  long 
flexible  pipe.  This  is  repeated  three  or  four  times.  If  by  inadvertence  any  potassa- 
lye  has  passed  beyond  d  up  to  h,  or  even  to  M,  after  the  cleansing  of  the  tube  A  has 
been  completed  water  is  again  let  enter  through  the  funnel,  t ;  F  is  raised  until  all  air 
has  been  removed  through  the  cock  n  and  the  flexible  pipe  a,  when  the  pinch-cock  is 
closed  on  a  and  the  water  is  allowed  to  pass  towards  M  by  turning  the  cocks  d  and  h 
round  for  90°.  Then  the  bottle  L  is  raised  and  F  is  lowered,  so  that  the  sample  of  gas,, 
the  water,  and  some  mercury  pass  over  to  A.  When  this  is  done  the  specimen  of  gas 
is  let  return  to  M,  the  cock  d  is  closed  towards  M  as  soon  as  the  liquid  almost  touches. 
it,  then  immediately  also  h,  and  the  water  is  again  let  flow  off  through  a.  Care  is 
taken  that  the  end  of  the  flexible  pipe  a  always  remains  filled  with  water  or  mercury. 
A  few  drops  of  liquid  should  also  remain  in  the  funnel,  t.  The  absorption  of  carbon 
dioxide  and  oxygen  is  much  promoted  by  letting  the  sample  of  gas  pass  ten  or  twelve 
times  from  one  tube  to  the  other  without  the  liquid  touching  the  cock -tube.  For  this 
purpose  the  bottles,  F  and  L,  are  taken  one  in  each  hand  and  lowered  alter- 
nately, keeping  the  eye  constantly  upon  the  liquid  as  it  ascends  in  A  and  M. 
The  oxygen  required  for  burning  the  combustible  gases  is  best  obtained 
electrolytically.  This  can  be  conveniently  effected  by  means  of  A.  W.  Hof- 
mann's  apparatus  for  the  decomposition  of  water,  or  with  the  U-tube  (Fig. 
49)  fixed  upon  a  simple  foot  and  filled  up  to  the  cock  with  water  containing 
sulphuric  acid.  The  point  of  the  tube  s  (its  platinum  electrode  is  connected 
with  the  positive  pole  of  a  Taucher  battery)  is  placed  in  the  end,  a,  of  the 
flexible  tube,  filled  with  water,  and  the  oxygen  is  let  pass  over  to  A  and 
thence  into  the  tube  M.  If  the  end  of  the  tube  a  is  completely  filled  with 
mercury,  the  oxygen  may  be  at  once  passed  into  M.  After  measurement,  the 
gaseous  mixture  is  driven  to  A,  the  spark  is  passed,  the  contraction  deter- 
mined as  usual,  the  carbon  dioxide  and  the  nitrogen  are  determined  and  cal- 
culated as  given  below.  If  the  gaseous  mixture  is  not  so  far  known  that  the 
effect  of  the  explosion  may  be  judged  with  certainty  in  the  first  place,  about 
100  vols.  are  allowed  to  pass  to  A,  the  cocks  d  and  h  are  closed,  the 
mercury-bottle  F  is  set  on  the  bottom  plate  of  the  apparatus,  the  pinch-cock 
is  opened  so  that  the  gas  is  strongly  expanded,  and  the  spark  is  let  pass 
over.  It  is  then  easily  seen  whether,  on  exploding  the  larger  residue,  a 
diminution  of  pressure  must  be  applied  to  reduce  the  force  of  the  explosion.  If  the 
gas  contains  less  than  30  per  cent,  of  combustible  ingredients,  it  may  be  placed  under 


Fig.  49. 


SECT.   I.] 


GAS  ANALYSIS. 


55 


an  increased  pressure  ;  if  up  to  30—40  per  cent.,  it  should  be  exploded  at  the  ordinary 
atmospheric  pressure ;  up  to  40-50  per  cent.,  at  a  reduced  pressure. 

In  manufacturing  laboratories  water  may  often  be  used  in  the  bottle  L,  but 
in  F  mercury  is  necessary.  The  tube  D  may  be  dispensed  with ;  M  is  graduated,  not 
in  millimetres,  but  in  100  vols. ;  the  water  level  in  the  bottle  L  and  the  tube  M  is 
placed  at  an  equal  height  before  reading  off,  so  that — as  during  the  short  time  required 
for  an  analysis  the  temperature  and  the  height  of  the  barometer  may  be  regarded  as 
constant — all  calculations  are  needless.  But  as  this  latter  advantage  can  only  be 
secured  by  placing  the  mercury  in  M  and  D  exactly  at  the  same  height  before  each 
reading,  the  author  prefers  the  apparatus  (Fig.  48)  with  mercury  in  both  bottles. 

As  a  lubricator  for  the  cocks,  the  author  recommends  a  mixture  of  melted  caout- 
chouc and  vaseline.  This  is  prepared  by  melting  two  parts  of  pure  caoutchouc  at  the 
lowest  possible  temperature  in  a  covered  porcelain  crucible,  adding  one  part  of  vaseline, 
and  stirring  till  cold.  The  readings  are  calculated  for  o°  and  1000  mm.  pressure  of 
mercury  according  to — 


with  the  aid  of  the  tables. 


___ _        - 
1000  (i  +  (0-00366  x  t] ) 


Tension  qftJie  Vapour  of  Water  according  to  jRegnault  :- 
i  =  temperature  Centigrade;  wi=tension  in  millimetres. 


t. 

m. 

t. 

m. 

t. 

m. 

t. 

m. 

I2'0 

10-46 

I5-0 

I2-7O 

18-0 

I5-36 

21  -O 

18-50 

12*2 

io-6o 

I5-2 

12-86 

18-2 

I5-55 

21'2 

1872 

I2'4 

1073 

I5-4 

I3'03 

18-4 

1575 

21-4 

18-95 

12*6 

10-88 

15-6 

I3-20 

18-6 

I5-95 

21'6 

I9-19 

12-8 

1  1  -02 

15-8 

I3'37 

18-8 

16-15 

21-8 

1942 

13-0 

ii'i6 

i6'o 

I3-54 

19-0 

16-35 

22'0 

19-66 

13-2 

11-31 

16-2 

I3'7I 

19-2 

I6-55 

22'2 

19-90 

»3  '4 

11-46 

16-4 

I3-89 

19-4 

1676 

22'4 

2O-I4 

13-6 

ii'6i 

16-6 

14-06 

19-6 

16-97 

22'6 

20-39 

13-8 

11-76 

16-8 

I4-24 

19-8 

I7-I8 

22-8 

20-64 

14-0 

11-91 

17-0 

I4-42 

20  '0 

I7-39 

23-0 

20-89 

14-2 

1  2  '06 

17-2 

14-61 

2O  '2 

I7-6l 

23-2 

21-14 

14-4 

I2'22 

I7-4 

1479 

20  '4 

I7-83 

23-4 

21-40 

14-6 

I2-38 

17-6 

14-08 

20  -6 

I8-05 

23-6 

21-66 

14-8 

12-54 

17-8 

I5-I7 

20-8 

I8-27 

23-8 

21-92 

Log.  i  +  0*00366  .  t. 


t. 

log. 

t. 

log. 

t. 

log. 

t. 

log. 

I2'O 

0-01867 

I5-0 

0-02321 

18*0 

0-02771 

21  *O 

O-O32I6 

I2'2 

0-01897 

I5-2 

0-02351 

18*2 

0-02801 

21'2 

0*03246 

I2'4 

0-01928 

I5-4 

0*02381 

18*4 

0*02831 

21*4 

0*03275 

I2'6 

0-01958 

I5-6 

0-02411 

18-6 

0*02861 

21*6 

0*03305 

12-8 

0-01989 

15-8 

0-02441 

18-8 

0*02891 

21*8 

0*03334 

13-0 

0*02019 

16-0 

0-02471 

19*0 

0*02921 

22*0 

0*03363 

13-2 

O-02O49 

16-2 

0-02501 

19-2 

0*02951 

22-2  ;  0*03393 

I3'4 

0*02079 

16-4 

0-02531 

19-4 

0-02980 

22  '4 

0*03422 

13-6 

O-O2IIO 

16-6 

0-02561 

19-6 

0-03009 

22'6 

0-03452 

13-8 

O-O2I4O 

16*8 

0*02591 

19-8 

0*03039 

22  8 

0*0348l 

14*0 

O-O2I7O 

17*0 

0*02621 

20*0 

0-03068 

23-0 

0-035IO 

14-2 

O'O22OO 

17-2 

0-02651 

2O  '2 

0*03098 

23-2 

0*03539 

14-4 

O-O223O 

17-4 

0-02681 

20-4 

0-03128 

23-4 

0*03568 

14-6 

O-O226I 

17-6 

0-02711 

20  -6 

0-03157 

23-6 

0*03598 

14-8 

O-O229I 

17*8 

0-02741 

20-8 

0-03187 

23-8 

0-O3627 

CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


Reduction,  of  the  Readies  of  the  Barometer  to  o~ 


B-6. 

Correct. 

B-6. 

Correct. 

B-4. 

Correct. 

40O 

0-0684 

600 

0*1027 

800 

0-1369 

420 

0'O7I9 

620 

0-1061 

820 

0-1403 

440 

0-0753 

640 

o'io95 

840 

0-1437 

460 

0*0787 

660 

0-1129 

860 

OT47I 

480 

0-0821 

680 

0-1163 

880 

0-1506 

500 

0-0856 

7OO 

0-1198 

900 

0*1540 

520 

0-0890 

72O 

0*1232 

920 

0-1574 

540 

0-0924 

740 

0-1266 

940 

0-1608 

560 

0-0958 

760 

0-1300 

960 

0-1643 

580 

0-0992 

780 

0-1335 

980 

0-1677 

E.g.,  in  an  analysis  the  reading  of  the  barometer  was  756*6  mm.  at  20-8°,  so  that, 
with  a  correction  of  2*7  mm.  for  the  glass  scale,  B,  =  753^9  mm.  To  the  reading  of  the 
measuring-tube,  M,  =  546-0,  corresponds  v,  —  5 53' 5.  The  position  of  the  mercury  in  the 
pressure  tube,  D,  was  also  546*0,  consequently  b-o,  and  as,  at  20*8°,  e=  18*3  mm., 
(B  -  b  -  e)  =  735-6  mm.  and  V  =  378*34,  as— 


Log-  553 '5 
Log.  735*6 
Log.  looo  (i+ 0-00366  x  20'8)  . 

Therefore  log.  V        .        .        . 
andV 

Collocated  with  the  second  reading : — 

M.  v.  D. 

546-0       ...       553-5       ...       546-0 
370-0       ...       378-8       ...         29-1 


2-74312 
2-86664 
3-03187 

2-57789 


(B-6-6.) 
735-6 


V. 

378-34 
378-41 


Mean  378-38 

If  the  two  readings  do  not  agree  to  at  least  0*4,  there  is  an  error,  and  the  experi- 
ment must  be  repeated. 


Fig.  50. 


Fig.  51- 


In  order  to  preserve  samples  of  gas  for  a 
length  of  time,  the  gas  is  drawn  by  means  of 
the  small  caoutchouc  aspirator, C  (Fig.47),through 
a  glass  globe  holding  100  c.c.  (Fig.  50),  and 
sealed  off  before  the  lamp  at  c,  c.  In  order  to 


Fig.  52. 


Mauerwerk    Masonry. 
Mauer  Wall. 


perform  this  sealing  even  in  the  open  air,  the  author  uses  a  small  oil  lamp,  n,  with 
a  brass  screen,  shown  in  section  (Fig.  51).     The  nozzle  of  the  blow-pipe,  e,  is  admitted 


SECT,  i.]  GAS  ANALYSIS.  57 

through  a  corresponding  aperture,  opposite  to  which  is  another  opening  through  which 
the  blow-pipe  flame  issues. 

The  sample  of  gas  must  be  drawn  through  a  glass  or  porcelain  tube  (not  iron),  and 
taken  at  a  point  where  the  gases  are  already  mixed.  In  ordinary  fires  this  takes  place 
where  the  gases  of  combustion  leave  the  apparatus  (steam  boiler,  &c.),  and  in  any  case 
before  the  draught-slide,  S  (Pig-  52),  as  cold  air  is  drawn  in  by  the  split  in  the 
masonry.  It  is  convenient  to  have  fixed  in  the  vault  of  the  smoke-channel  a  tube,  e, 
2  or  3  c.m.  in  width,  a  piece  of  a  gas-pipe,  luting  it  well,  and  inserting  in  it,  by 
means  of  a  caoutchouc  plug,  the  thermometer,  t,  and  the  glass  tube,  r,  for  taking 
specimens.  The  mercurial  vessel  of  the  thermometer  (i  metre  in  length)  and  the 
lower  aperture  of  the  glass  tube,  r,  should  be  in  the  middle  of  the  current  of  gas,  as 
the  figure  shows. 

The  loss  of  heat  in  the  smoke-gases  appears  from  the  following  calculations.  If 
the  gas-analyses  made  during  an  experiment  show  on  the  average  k  per  cent,  carbon 
dioxide,  o  per  cent,  oxygen,  and  n  per  cent,  nitrogen,  the  proportion  of  air  consumed 
to  that  theoretically  required  is,  when  the  air  contains  x  per  cent,  of  oxygen  and  z  per 
•cent,  of  nitrogen — 


x  -  (z  o  :  n)       n  -  (zo:x)       21  -  (79  o  :  n) 

for  2 1  per  cent,  oxygen  ;  i  kilo,  of  the  coal  with  o  per  cent,  of  carbon  gives  = 
1-854  c  :  100  =  K  cubic  metre  carbon  dioxide  (at  o°  and  760  mm.),  Ko  :  k  =  O  cubic 
metre  0  and  K  n  :  k  =  N  cubic  metres  of  nitrogen.  The  quantity,  W,  of  the  watery 
vapour  contained  in  the  smoke-gases  is  calculated  from  the  moisture  of  the  coal 
(o-oi  w),  that  formed  by  the  combustion  of  the  hydrogen  (0-09  h),  and  that  contained 
in  the  air  serving  for  combustion  (v  L/).  The  total  quantity  of  the  combustion-gases 
from  i  kilo,  of  coal  is  therefore — 

K  (o  +  n)          28  W 

K  + T H — ITT—  +  — o —  cubic  metre  at  o  and  760  mm. 

K  200  '4       o  '005 

or —  +  1-43  0  +  1-257  N  +  —  +  W  kilo. 

100  100 

If  the  smoke-gases  contain  carbon  monoxide  and  hydrocarbons,  it  must  be  remem- 
bered that,  according  to  the  formulae  C  +  02  =  CO2,  0  +  0  =  CO,  and  C  +  2H,=  CH4, 
each  cubic  metre  of  these  gases  contains  0-5395  kilo,  carbon.  If  the  analysis  shows 
k  per  cent,  carbon  dioxide,  d  per  cent,  carbon  monoxide,  m  per  cent,  methan,  h  per 
cent,  hydrogen,  o  per  cent,  oxygen,  and  n  per  cent,  nitrogen,  as  well  as  per  cubic 
metre  r  kilo,  carbon  as  soot,  then  i  cubic  metre  of  these  gases  contains — 

(k  +  d  +  m)  0-^395          ,  ..          , 

^ ' — ^^2  +  r  kilo,  carbon, 

100 


and  i  kilo,  of  coal  yields — 

cC  :  loo 


100 
in  which  we  have — 


d  +  m 

x  0-5395  + 


=  I  cubic  metre  dry  gcises, 


Gk  „„   Kd      Gd 

—  =  K  cubic  metre  CO,,,  -j-  or  —  CO, 

Gm  Gr  A  „  Go^        ,  G  ra    . 

—  methan,  —  H,  —  O,  and  —nitrogen. 

The  proportion  of  soot  is  so  trifling  that  it  may  be  neglected. 

Sulphurous  or  sulphuric  acid  and  the  vapour  of  water  may  be  calculated  as  above, 
the  weight  of  these  gases  being  readily  found  with  the  aid  of  the  following  table : — 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


,- 

Weight  of 

Specific  Heat  of 

Specific  Hent. 

i  Cubic  Metre, 
kilos. 

i  Cubic  Metre. 

CO.,  at  10°  to  isc 

f 

0*2091 

1-9781 

0-414 

20C 

> 

0-2156 

— 

0-427 

25< 

> 

O'222O 

— 

D'439 

3oc 

) 

O-228l 

— 

0-451 

35< 

> 

0-234I 

— 

0-463 

IOOC 

) 

O-289I 

— 

0-572 

I5cx 

) 

0-3I80 

— 

0-629 

2OOC 

) 

03290 

— 

0-651 

CO      . 

O-2450 

I  -2593 

0-308 

O 

0-2175 

I  -4303 

0-311 

N 

0-2438 

I  '2566 

0-306 

H 

3-4090 

0-0896 

0-305 

Steam 

0-4805 

0-8048 

0-387 

Methan  (CH4) 

0-5929 

07160 

0-424 

SO2     . 

0-ISS3 

2-8640 

0-445 

The  loss  of  heat  by  the  higher  temperature  of  the  smoke-gases  is  found  by  multi- 
plying the  separate  quantities  of  the  gases  by  the  specific  heat  and  the  excess  of 
temperature  of  the  gases  above  the  air  serving  for  combustion. 

The  loss  from  incomplete  combustion  is  found  from  the  combustion  value  of  the 
unburnt  coal  in  the  cinders  and  the  combustible  ingredients,  if  any  (carbon  monoxide, 
methan,  hydrogen,  soot),  of  the  smoke-gases. 

As  an  instance  of  the  loss  of  heat  by  the  imperfect  combustion  of  i  kilo,  of  coal, 
the  following  figures  may  serve  : — 


Combustion 

f  nil  if*  TVTAtrPs 

VllllP 

Heat-units. 

CO       .         . 

0-292 

0-3680 

893 

Methan 

0-073 

0-0520 

620 

H 

0-073 

0-0065 

I87 

Soot    . 

0-0080 

65 

Carbon  in  cinders 

— 

0-0050 

40 

1805 

On  the  basis  of  the  experience  which  the  author  has  collected  in  more  than  4000 
gas  analyses,  he  considers  the  apparatus  figured  and  described  above  (Fig.  47)  the  best 
and  the  most  convenient  for  judging  of  steam-boiler  furnaces,  domestic  stoves,  brick 
and  porcelain  furnaces,  ultramarine  furnaces,  and  alkali  furnaces,  and  as  also  well 
adapted  for  examining  blast-furnace  and  cupola  gases,  and  of  puddling  furnaces  ;  and 
even  for  examining  the  kiln-gases  in  sulphuric  acid  works,  the  saturation  gases  in  sugar- 
works,  and  for  petroleum  lamps  and  gas  engines.  In  order  to  determine  the  small 
quantities  of  combustible  gases  which  occur  in  normal  combustion-gases,  even  accurate 
volumetric  procedures  are  generally  insufficient.  Those  with  platinum  coils  (Orsat), 
palladium-asbestos,  &c.,  do  more  harm  than  good,  as  they  lead  to  wrong  conclusions. 
In  such  cases  gravimetric  determinations  must  be  made  with  a  sample  drawn  directly 
through  the  apparatus  for  a  considerable  time  without  the  interposition  of  a  gasometer. 
But  at  the  same  time  a  volumetric  test  should  be  made  every  five  or  ten  minutes  with 
the  apparatus  described  above,  in  order  to  watch  the  progress  of  the  combustion. 

For  gas  fires  the  same  apparatus  is  sufficient  for  ordinary  control.  Care  must  be 
taken  that  the  generator- gases  contain  a  minimum  of  carbon  dioxide  along  with  much 
carbon  monoxide,  whilst  the  gases  escaping  should  contain  a  maximum  of  carbon 
dioxide  and  no  monoxide. 

Steam-boiler  Firing. — By  far  the  majority  of  steam  boilers  have  too  large  a  grate, 
and  work,  in  consequence,  with  a  great  excess  of  air,  losing  much  heat  in  the  chimney. 


SECT,  i.]  STEAM   BOILER   FIRING.  59, 

The  gases  from  a  steam-boiler  fire,  for  instance,  contained  i'8  per  cent.  C02  and  19  per 
cent.  O  at  169°,  representing  a  loss  of  heat  of  3921  heat-units,  or  60  per  cent,  of  the 
total  combustion  value.  After  the  masonry  and  the  grate  were  thoroughly  repaired, 
and  the  strength  of  the  draught  was  regulated  according  to  the  indications  of  gas 
analyses,  the  gases  contained  18*7  per  cent,  of  carbon  dioxide  and  17  per  cent,  of 
oxygen,  corresponding  to  a  loss  of  heat  of  only  508  heat-units,  or  7  per  cent. !  In 
judging  a  fire  it  is  necessary  to  look  under  the  grate ;  all  the  intervals  between  the 
bars  must  be  equally  bright. 

For  ordinary  control  it  is  sufficient  to  determine  the  CO3  and  0  in  three  samples  of 
the  gas  taken  in  rapid  succession.  The  more  C02  (without  CO)  is  present,  the  better 
is  the  firing.  For  a  coal  fire  n  k  +  o  must  be  about  20,  if  the  combustion  is  complete. 
In  large  works  it  is  advisable  to  connect  a  narrow  lead  pipe  with  the  pipe  fixed  in 
the  flue  (inserting,  however,  a  tuft  of  asbestos  to  keep  back  soot  and  dust),  and  to> 
carry  it  into  the  laboratory.  In  order  to  take  samples  of  gas  at  any  time,  so  much  gas 
is  first  drawn  off  as  the  pipes  will  hold,  and  the  sample  is  then  taken. 

In  conducting  heating  experiments  (which,  according  to  the  importance  of  the  case, 
should  last  from  three  to  ten  hours),  six  to  twelve  samples  are  taken  hourly,  deter- 
mining their  proportion  of  C02  and  O,  and  of  CO  if  present.  If  the  gases  contain 
notable  quantities  of  the  latter,  which  is  the  case  only  in  defective  boiler  furnaces,  the 
stoking  must  be  altered,  or  samples  of  gas  must  be  sealed  up  in  bulbs  and  examined 
for  carbon  monoxide,  hydrogen,  and  hydrocarbon.  The  moisture  and  the  temperature 
of  the  air  entering  the  fire-box  should  be  determined  hourly. 

For  deciding  on  the  duty  of  a  steam  boiler  by  an  evaporation  experiment,  which 
should  be  continued  at  least  for  ten  hours,  the  Association  of  German  Engineers  and 
the  Steam  Boiler  Association  have  agreed  on  the  following  regulations  : — 

Before  beginning  the  experiments,  the  boiler  must  be  cleaned,  examined  within 
and  without,  and  tested  for  leakage;  the  flues  are  swept;  the  joints  of  the  walls 
pointed  and  plastered  over.  The  boiler  must  then  be  kept  for  at  least  one  day  in, 
normal  work,  in  order  that  it  may  be  in  its  ordinary  permanent  condition. 

The  level  of  the  water  and  the  pressure  of  steam  are  accurately  noted  at  the  com- 
mencement of  the  experiments,  and  are  kept  all  the  time  as  uniform  as  possible.  Th& 
pressure  of  steam  is  gauged  by  the  manometer,  and  noted  every  fifteen  minutes. 

The  feed-water  is  either  weighed  or  measured  in  tared  vessels,  the  contents  of  which 
are  regulated  according  to  the  temperature.  In  accurate  experiments  weighing  alone  is 
admissible.  The  feeding  must  be  effected  regularly,  and  with  a  minimum  of  interrup- 
tion ;  feeding  must  be  avoided  shortly  before  the  beginning  and  the  end  of  the  experi- 
ment. The  temperature  of  the  water  is  measured  in  the  cistern,  from  which  it  i& 
drawn  every  thirty  minutes,  and  just  before  its  entrance  into  the  boiler.  This  must  be 
done  with  every  feed.  Feeding  with  injectors  is  permissible  only  when  their  supply  of 
steam  is  drawn  from  the  boiler  in  question. 

If  simultaneously  with  the  examination  of  the  performance  of  the  boiler  there  is 
carried  on  an  inquiry  into  the  consumption  of  steam  in  a  machine  supplied  by  the 
boiler,  the  use  of  steam  pumps  for  feeding  is  inadmissible  if  they  derive  their  steam 
from  the  experimental  boiler  or  if  their  waste  steam  comes  in  contact  with  the  feed- 
water. 

All  leakage  from  the  boiler  fittings  and  all  water  blown  off  must  be  caught  and 
taken  into  account.  The  weight  of  water  thus  ascertained  must  be  recalculated  as 
feed-water  at  o°  and  steam  at  100°.  (See  Table.) 

In  determining  the  consumption  of  water,  care  must  be  taken  that  the  fire  at  the 
beginning  of  the  trial  is  charged  and  cleaned  normally,  ash  and  slag  being  removed 
from  the  ash-box.  If  the  ash  cannot  be  removed,  the  residues  therein  should  be 
brought  to  a  given  level  before  and  after  the  experiment.  The  fire  must  be  in  the 


6o 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


same  condition  at  the  end  of  the  experiment  as  at  the  beginning.  The  duration  of  the 
heating  and  the  consumption  of  fuel  are  noted.  The  fuel  consumed  during  the  experi- 
ment is  to  be  weighed  and  suitably  broken  up.  The  fire  is  fed  regularly.  Slags  and 
ash  are  weighed  and  examined  for  the  presence  of  combustible  matter. 

Experiments  in  which  notable  quantities  of  water  have  evidently  been  carried  away 
mechanically  by  the  steam  are  useless.  No  accurate  and  trustworthy  methods  are 
known  for  the  determination  of  such  water. 

Evaporation  experiments  without  a  simultaneous  examination  of  the  smoke-gases 
have  little,  if  any,  value. 

The  total  evaporation-heat  of  water  is,  according  to  Regnault,  =  606*5  +  °'3°5  ^ 


Temperature  t  of 
Saturated  Steam. 

Steam  Tension 

Pressure  on  i  Square 
Centimetre  in  Kilos. 

Evaporation-heat. 

in  mm. 

in  Aim. 

O° 

4-6 

.  



606-5 

20 

I7-4 

.  — 

— 

612-6 

40 

54  '9 

0-072 

0-075 

618-7 

60 

148-8 

0-196 

0-203 

624-8 

80 

354-5 

0-466 

0-482 

630-9 

IOO 

760-0 

I'OOO 

1-033 

637-0 

no 

1075  '4 

1-415 

1-462 

640-0 

1  20 

I49i  '3 

1-962 

2-027 

643-I 

130 

2030-3 

2-671 

2-760 

646-1 

140 

2717-6 

3-576 

3^95 

649-2 

150 

358I-2 

4-712 

4-869 

652-2 

1  60 

4651*6 

6'I2O 

6-324 

655-3 

170 

59617 

7-844 

8-105 

658-3 

1  80 

7546-4 

9-929 

10-260 

661-4 

190 

9442-7 

12-425 

12-834 

664-4 

Experiments  executed  by  the  author  showed  the  following  distribution  of  heat  in 
three  boilers : — 


123-8 


86-3 


26-6 


24-7 


46-9 
8-7 


7790 

...    7720     . 

..    7630 

74-9 

...     68-4     . 

..     83-6 

2-1 

...       3'6     • 

..      0-9 

— 

— 

..      0-3 

l6-7 

...     19-3     . 

..     10-6 

6-3 

...      8-7     . 

..       4-6 

Coal  to  each  square  metre  grate  surface       .  kilos. 
Water  to    each   square   metre    of    heating 

surface „ 

Combustion  value  of   the  coal  determined 

calorimetrically heat-units 

Percentage  of  heat  taken  up  in  water  . 

Loss  in  cinders,  &c per  cent. 

„     in  gases  imperfectly  burnt    ...  „ 

„    in  higher  temperature  of  the  smoke-gases        „ 

„     by  conduction  and  radiation         .        .  „ 

The  grate  of  the  boiler  furnace  should  be  easily  cleaned ;  hence  all  designs  of 
grates  which  obstruct  such  cleansing  with  the  object  of  giving  the  air  free  and  uniform 
access  to  the  fuel  cannot  be  recommended — e.g.,  that  of  Fletcher  (Fig.  53).  Those 

with  lateral  projections  on  the  bars,  the  so-called 

£'  53-  polygon  grates,  are  to  be  rejected.     For  fuel  which 

does  not  cake,  the  oblique  grates  (e.g.,  Tenbrinck) 
are  worth  attention,  as  here  there  occurs  a  partial 
degasifying  of  the  fuel  as  it  slides  downwards,  and 
thus  the  formation  of  smoke  is  to  a  great  extent 
prevented. 

This  object  is  more  perfectly  effected  by  the 
so-called  mechanical  grates,  which  drive  the  fuel  continuously  into  the  fire-box,  so 
that  the  gases  evolved  in  front  pass  over  the  ignited  coke  and  are  burnt.  One  of  the 
earliest  arrangements  of  this  kind  is  the  chain  grate.  It  is  costly,  soon  wears  out, 
and  has  been  gradually  abandoned.* 

*  We  have  observed  that  it  brings  out  a  considerable  quantity  of  imperfectly  burnt  fuel,  ami 
lets  it  fall  into  the  ashes,  as  waste. — [EDITOR.] 


SECT.   I.] 


HOUSE   HEATING. 


61 


The  arrangement  of  Dougal  works  well  in  practice.*  All  these  devices,  however, 
are  expensive  and  consume  mechanical  power. 

It  has  been  already  remarked  that  the  almost  numberless  devices  for  "  smoke  con- 
sumption "  are  impracticable.  Good  gas-firing  gets  rid  of  smoke  from  the  chimneys, 
but  it  cannot  be  recommended  for  steam  boilers.  The  best  solution  of  the  important 
smoke  problem  is  the  substitution  of  coal-gas  or  water-gas  burners  for  domestic  fires, 
and  of  the  gas  engine  for  the  steam  engine.  This  latter  step  will  probably  be  very 
generally  adopted  with  the  expiry  of  the  Otto  patent. f  At  Terni,  near  Rome,  a  mixture 
of  water-gas  and  generator-gas  is  used  for  a  gas  engine.  For  the  production  of  14*35 
horse-power  the  engine  consumes  hourly  ii'86  cubic  metres  water-gas  and  36' 66  cubic 
metres  generator-gas,  and  works  very  satisfactorily.  This  is,  per  horse-power — 

0-83  cubic  metre  water-gas        =2182  heat-units 
2'55  „  generator-gas  =  2422        „ 

or  about  4600  heat-units.  The  same  work,  if  performed  with  lighting-gas,  would 
require  at  least  0*9  cubic  metre,  representing  4770  heat-units.  For  producing  the 
above-named  quantities  of  water-gas  and  generator-gas  075  kilo,  of  coke  or  coal  will  be 
required,  whilst  for  obtaining  0*9  cubic  metre  of  coal-gas  there  would  be  consumed 
3  kilos,  of  the  best  gas-coal  (yielding  only  i  -8  kilo,  of  coke  as  residue),  whilst  a  steam 
engine  of  the  same  power  uses  4  kilos,  of  coals.  There  is  besides  the  ease  of  distributing 
the  power  from  gas  engines,  so  that  they  may  claim  the  future  both  for  small  and 
large  industries. 

House-heating. — The  object  here  in  view  is  to  heat  dwelling-rooms,  &c.,  uniformly, 
with  a  minimum  expenditure  of  fuel,  and  without  rendering  the 
air  impure.  Hence  all  kinds  of  heating  which  do  not  carry  off 
the  products  of  combustion  are  at  once  excluded — e.g.,  the  car- 
bonatro  stoves  of  A.  Nieske,  various  coal-gas  stoves,  <fec.  Such 
arrangements  testify  to  a  marvellous  thoughtlessness. 

The  forms  of  heating  may  be  divided  into  separate  arrange- 
ments (fires  and  stoves)  and  collective  arrangements  (heating  with 
hot  air,  steam,  or  hot  water). 

Heating  with  open  fires  involves  a  great  expenditure  of  fuel.f 
The  open  fire  is  used  in  Germany  only  where  appearance  is  aimed 
at  more  than  heating.  The  author  cannot  admit  the  alleged 
advantages  of  heating  with  radiant  heat.§ 

Stove-heating  is  most  common.  To  explain  the  action  of  an 
iron  stove  we  may  take  the  diagram,  Fig.  54.  The  fire-box,  A, 
-|  metre  in  height,  is  lined  with  fire-clay ;  the  door  to  the  fire- 
box, a,  with  an  oblique  grate,  and  that  to  the  ash-pit,  B,  are  fitted 
with  screws,  so  that  they  may  fit  closely,  as  does  also  that  through 
which  fuel  is  introduced,  6.  The  smoke-gases  pass  in  the  direc- 
tion of  the  arrow  through  the  top  piece,  C,  and  escape  through 
the  sheet-iron  pipe,  D,  to  the  chimney. 

At  the  aperture,  d,  the  thermometer,  t  (filled  with  nitrogen),  is  inserted  for  experi- 
mental purposes  by  means  of  a  good  cork,  the  tube,  e,  leading  to  an  apparatus  for 


a 


*  Dingier s  Journal,  232,  p.  346. 

t  Before  coal-gas  is  used  in  the  household  it  must  be  much  cheaper,  and  before  water-gas  can 
be  safely  introduced  to  warm  our  houses  and  cook  our  food  it  must  be  freed  from  carbon  monoxide, 
as  already  described. — [EDITOR.] 

$  Ninety  per  cent,  of  the  heat  generated  being  wasted.  The  recent  "  improvements  "  introduced 
in  England  have  been  steps  in  the  wrong  direction. — [EDITOR.] 

§  Jahresber.  1887,  p.  145. 


•62 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


measuring  the  draught  and  the  glass  tube,/",  which  is  connected  with  apparatus  for  the 
analysis  of  the  smoke-gases.  These  are  thoroughly  mixed  by  the  bendings  through 
which  they  pass,  so  that  specimens  taken  simultaneously  at  c  have  the  same  composition 
to  T^  per  cent.  If  anthracite  is  used,  the  gases  have  the  composition  given  in  the  sub- 
joined tables. 

The  results  indicate  a  total  loss  of  heat  in  the  chimney  of  only  8  per  cent.,  so  that 
92  per  cent,  of  the  heat  remains  in  the  room. 

To  obtain  such  favourable  results  the  fire-room  of  all  iron  stoves  must  be  lined 
with  fire-proof  stone,  or  tiles  of  fire-clay.  If  the  fuel  touches  the  iron  surfaces,  com- 
plete combustion  is  rarely  possible.  Further,  the  iron  plates  become  overheated,  so 
that  they  allow  carbonic  oxide  to  permeate  them,  and  they  certainly  singe  all  organic 
dust,  thus  spoiling  the  air  of  the  room.  It  would  be  desirable  for  the  gases  to  descend 
again  in  order  to  give  off  their  heat  still  more  completely  through  the  sides  of  the 
stove  to  the  air  of  the  room. 


Time, 
h.  m. 

C02. 

CO. 

0. 

N. 

Temperature  of 
Escaping  Gases. 

Remarks. 

2.50 

I2'S 



8-0 

79  '5 

240° 

Temperature  in  the  laboratory,  12°. 

3-00 

I2'6 

— 

7-9 

79'5 

241 

i  millimetre  draught. 

3.10 

11  "5 

— 

9-1 

79  '4 

240 

Fuel  added,  doors  a  and  b  closed. 

3.20 

u-8 

trace 

8-4 

79-8 

2O  I 

3-30 

137 

— 

6-4 

79  '9 

234 

3-40 

14-1 

— 

6-2 

797 

242 

3-50 

I3'6 

— 

67 

797 

248 

Fuel  added. 

4.00 

I3-5 

— 

6-9 

79-6 

206 

4.10 

I3H 

— 

7-2 

79  "4 

229 

4.20 

i3'5 

— 

7-0 

79  '5 

248 

4-30 

13-1 

— 

7'4 

79'5 

247 

4.40 

I2'0 

— 

8-6 

79  '4 

246 

If  the  stove  is  used  full,  the  lower  doors  must  be  kept  tightly  closed,  as  otherwise 
•  carbon  monoxide  may  be  formed,  which,  if  the  draught  is  defective,  may  pass  out  into 
the  room.  The  regulation  of  the  supply  of  air  is  very  important  for  the  utilisation  of 
the  heat.  If,  in  the  stove  Fig.  54,  the  ash-pit  door  is  opened,  so  that  the  air  passes 
through  the  horizontal  grate  into  the  fire-box,  and  also  the  door  a,  the  temperature  of 
the  escaping  gases  rises  so  rapidly  that  the  thermometer  has  to  be  removed,  whilst,  in 
accordance  with  the  increased  draught,  the  proportion  of  carbon  dioxide  falls,  and  the 
loss  of  heat  rises  up  to  40  per  cent. 

Hundreds  of  thousands  of  stoves  in  Germany  which  have  imperfect  doors  or  none 
at  all  allow  from  50  to  80  per  cent,  of  the  entire  combustion  value  of  the  fuel  to  pass 
up  the  chimney,  a  loss  which  amounts  yearly  to  millions  of  marks. 

Certain  stoves,  such  as  those  of  Sturm  and  Henschel,  are  not  used  or  known  in 
Britain,  and  their  description  may  therefore  be  omitted. 

Earthenware  stoves  are  generally  built  up  of  tiles.  A  Russian  stove,  e.g.,  is  a 
longish  rectangular  block,  and  has  six  smoke  channels.  Fig.  55  shows  the  plan, 
Fig.  56  an  elevation  of  the  broad  side,  Fig.  57  of  the  narrow  side,  and  Fig.  58  a 
longitudinal  section.  From  the  fire-box  covered  with  an  arch,  a,  the  fire  rises  up  in 
the  flue  i,  descends  again  in  flue  2,  rises  in  3,  falls  in  4,  rises  in  5,  and  falls  in  6, 
whence  it  escapes  through  the  stove-pipe  into  the  chimney.  Near  the  connection  of  the 
last  flue  with  the  stove-pipe  a  four-sided  plate  of  cast  iron  (Figs.  59,  60,  and  61)  is 
built  in  ;  this  plate  has  in  the  middle  an  aperture  of  2 1  to  24  centimetres  in  diameter, 
with  an  upright  neck  of  3  centimetres  and  an  internally  projecting  margin  of  2  centi- 
metres. A  cast-iron  cover,  a,  provided  with  a  handle,  fits  over  the  aperture,  a  second, 
larger,  cover,  6,  with  a  projecting  margin,  fits  over  the  neck  and  closes  the  whole.  For 
heating,  the  fire-box  is  filled  with  short  pieces  of  wood,  the  wood  is  kindled,  the  door 


SECT.    I.] 


HOUSE   HEATING. 


being  left  open  at  first ;  it  is  afterwards  closed  so  that  the  air  enters  through  its 
apertures. 

Experiments  which  the  author  carried  out  with  a  tile  stove,  1*2  metre  wide  and 
3  metres  in  height,  showed  that  with  a  coal  fire  from  40  to  80  per  cent,  of  the  heat 
escaped  up  the  chimney,  so  that  tile  stoves  are  less  suitable  for  giving  out  heat  than 
iron  stoves.  The  surfaces  which  come  in  contact  with  the  air  of  the  room  are  kept 
carefully  free  from  sharp  angles  and  roughnesses,  and  are  covered  with  a  glaze,  all  cir- 
cumstances which  impede  the  communication  of  heat  as  much  as  possible.  Hence  the 


Fig-  55- 


Fig.  58- 


Fig.  56. 


Fig-  57- 


S  I 


Fig.  59- 


Fig.  60. 


Fig.  61. 


gases  pass  into  the  chimney  with  about  100°  more  heat  than  that  from  the  iron 
stove  (Fig.  55),  the  surface  of  which  is  covered  with  small  ornaments  in  relief,  and  is 
consequently  well  adapted  for  throwing  off  heat.*  The  loss  of  heat  in  tile  stoves  can 
be  diminished  by  carefully  closing  the  doors.  If  the  supply  of  heat  to  an  iron  stove 
lined  with  fire-clay  or  tiles  is  properly  regulated  it  retains  the  heat  as  long  as  a  tile 
stove. 

Hot-air  heating  differs  from  stove  heating  by  the  circumstance  that  the  fire  is  not 
in  the  rooms  to  be  heated,  but  outside,  and  often  below  them.  As  a  specimen  of  a 
successful  arrangement  of  this  kind  the  author  describes  that  existing  in  his  own 
house.  It  has  to  supply  six  rooms  with  warm,  pure  air — below,  three  dwelling-rooms, 
A,  B,  C  (Fig.  62)  ;  V,  an  ante-room  ;  D,  kitchen  ;  above,  one  storey  high  (Fig.  63),  A, 


Tile  stoves  can  of  course  be  made  with  unglazed  surfaces  and  small  projecting  ornaments. 


64 


CHEMICAL  TECHNOLOGY. 


[SECT. 


library  ;  C,  work-room  ;  D,  laboratory.     The  heating  arrangements  are  in  the  space 
below  B. 

The  air-entrance,  K  (Figs.  64-68),  is  underneath  the  veranda,  on  the  south-western 

Fig.  62.  Fig.  63. 


P  Zufuhritngskana.!. 
mAUufikanal. 
B  Rauchka.na.1. 


Explanation  of  Terms. 


Zvfulinmgskanal     Access  for  air. 
Abluftkanal  Exit  for  air. 


llaiichhanal 
Ltiftschacht 


Smoke  channel. 
Air  shaft. 


side  of  the  house.     The  opening  is  covered  with  a  wire  grating,  before  which  stands  a 
triple  row  of  juniper  bushes,  so  that  all  the  coarser  impurities  are  kept  out. 

The  air-filter,  F,  is  2   metres  wide,  and  has  a  total  filtering  surface  of  50  square 
metres.     The  arrangement  is  adapted  for  5000  cubic  metres  air  per  hour,  whilst  the 

Fig.  66. 


heating  itself  requires  only  2000  to  3000.  Not  the  least  disturbing  influence  has  been 
felt  in  the  supply  of  air  in  three  years.  All  the  air  entering  has  to  pass  through  a 
dense  cotton  tissue,  which  keeps  back  soot  and  dust.  The  air,  freed  from  dust,  passes 


SECT,  i.]  HEATING  ARRANGEMENTS.  65 

tnrough  the  channel,  L,  into  the  heating-room,  becomes  warmed  in  the  tubes,  C,  and 
passes  at  IT  in  to  six  vertical  channels  of  smooth  masonry  (but  not  plastered),  of  which 
five,  as  shown  in  Figs.  62  and  63,  are  placed  in  a  niche  of  the  corner  room,  and  open 
into  the  rooms  2  metres  above  the  floor.  From  here  the  waste  air  escapes  through 
six  shafts  close  above  the  floor.  Coal  is  introduced  at  /,  whilst  the  door  t  is  opened 
only  to  stir  the  fire ;  the  door  a  regulates  the  supply  of  air. 

About  85  per  cent,  of  the  total  combustion-value  served  to  warm  the  rooms,  and 
5  to  7  per  cent,  more  are  not  wasted,  but  serve  to  warm  the  staircase  uniformly. 

The  greatest  consumption  of  fuel  in  twenty-four  hours  was  no  kilos,  of  coal  at  art 
outside  temperature  of  —15°  and  a  violent  east  wind  with  driving  snow.  At  4-3° 
and  calm  weather  only  25  kilos,  of  coal  were  used.  The  objections  raised  against  hot 
air  on  the  score  of  drying  the  air  are  completely  groundless. 

Water-heating. — As  is  shown  in  the  diagram,  Fig.  67,  the  water  heated  in  the 
boiler,  A,  rises  in  the  tube,  c,  up  to  d  ;  it  becomes  heavier  again 
by  giving  off'  its  heat  in  the  pipes,  f,  laid  down  in  the  rooms,  &c.,  Fig.  67. 

to  be  heated,  and  flows  back  to  the  boiler.  If  the  system  of 
pipes  is  left  open  at  its  highest  point,  e,  no  increase  of  pressure 
can  ensue,  and  we  have  a  low-pressure  water  heating ;  if  the 
system  is  closed  so  that  the  water  may  be  heated  to  1 80° -200° 
(Perkins'  tubes),  it  is  a  high-pressure  water  heating.  In  the 
latter  case  the  pipes  may  be  smaller,  but  there  is  the  possibility 
of  an  explosion.  The  warm  water  of  artesian  wells  and  that  of 
hot  springs  is  used  for  heating  conservatories,  factories,  &c.  The 
Catholic  town  church  at  Baden-Baden  has  been  heated  since 
1867  by  means  of  the  hot  springs  in  the  neighbourhood,  which 
have  a  temperature  of  67°. 

Steam  heating  may  be  effected  either  at  low  pressure  (|  atmosphere)  or  at  high 
pressure.  In  each  case  the  steam  passes  into  mains  laid  beneath  the  floors  of  the 
buildings  to  be  heated.  Here  it  is  liquefied  by  giving  off'  its  latent  (and  a  part  of  its 
specific)  heat,  and  flows  back  to  the  boiler. 

All  collective  heating  arrangements  have  the  great  advantage,  as  compared  with 
stoves  and  open  fires,  that  they  occasion  no  ash,  soot,  &c.  They  allow  also  of  a  great 
economy  of  labour,  as  only  a  single  fire  has  to  be  kept  up  to  warm  a  great  number  of 
rooms.  They  also  admit  of  a  more  perfect  utilisation  of  the  fuel  than  do  ordinary 
stoves,  and  they  enable  a  uniform  and  unchanging  temperature  to  be  kept  more  easily 
than  does  any  other  kind  of  firing. 

Hot-air  heating  involves  the  least  initial  outlay,  is  easily  attended  to,  and,  where 
the  ventilation  is  good,  it  produces  a  uniform  heat  in  the  rooms.  It  is  not  adapted  for 
distributing  heat  horizontally  in  large  halls  or  long  series  of  rooms,  since  hot  air 
should  ascend  vertically  as  nearly  as  possible.  In  such  places  steam  or  water  heating 
is  preferable.* 

Heating  with  Coal-gas. — This  is  a  very  pleasant,  but  a  very  expensive,  arrange- 
ment, i  cubic  metre  coal-gas  evolves  5300  heat-units,  watery  vapour  being  one  of  the 
products  of  combustion.  Of  this  total,  about  5000  heat-units  are  utilised.  For  a  small 
room  during  the  entire  winter  the  average  demand  for  heat  is  10,000  heat-units  daily. 
This  requires  2  cubic  metres  of  coal-gas,  which  may  cost,  according  to  the  locality,  from 

*  Hence  steam  or  hot  water  is  selected  for  heating  museums,  libraries,  galleries  of  pictures, 
conservatories,  &c.,  where  a  uniform  heat,  strictly  under  control,  is  required  in  all  parts.  It  must 
be  remembered  that  the  mains  should  never  be  allowed  to  lie  upon  wood,  still  less  sawdust, 
shavings,  &c.,  as,  though  the  temperature  may  never  exceed  100°,  wood  thus  heated  gradually 
undergoes  a  series  of  chemical  changes  which  render  it  spontaneously  combustible.  The  mains 
should  be  supported  upon  firebricks. — [EDITOR.] 

E 


66 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


o'24  to  0-40  shilling,  whilst  in  properly  arranged  hot-air  heating  the  coal  consumed 
•costs  merely  0*03  to  0-04  shilling.  In  heating  with  stoves  we  have,  on  the  other 
hand,  the  trouble  of  feeding  the  fires,  the  inevitable  dirt,  and  the  difficulty  of  main- 
taining an  even  temperature. 

Gas-firing. — Gas-firing  is  distinguished  from  ordinary  firing  by  the  circumstance 
that  the  fuel  is  first  gasified,  and  then  burnt,  atmospheric  air  being  introduced  at  two 
distinct  places.  The  air  required  for  gasifying  enters  the  fuel  through  the  grate.  The 
air  (called  secondary)  needed  for  burning  the  gas  thus  formed  enters  the  fire-box. 

A  system  of  gas-firing  adapted  for  lignite  is  shown  in  Figs.  68  and  69.     In  this 

Fig.  68.  Fig.  70. 


Sections  1-11. 


JTnh— Wood. 

Arrangement,  built  by  Heupel  at  the  Aussee  Saltworks,  the  boiling  pans,  Z,  are 
1 7' i  metre  long  by  7-6  broad,  so  that  each  has  a  heating  surface  of  130  square  metres, 
for  which  three  gas  generators,  A,  with  the  grates,  T  and  P,  were  placed  equally  dis- 
tributed over  the  breadth  of  the  pan.  The  regulation  of  the  production  of  gas  is 
•effected  by  means  of  tightly  fitting  air- valves  in  the  door,  E,  in  front  of  the  ash-pit. 
The  apparatus  for  burning  the  gas,  which  is  separated  from  the  feeding  shaft,  A,  by 
means  of  a  simple  vault,  consists  of  an  almost  horizontal  grating,  F,  constructed  of  fire- 
bricks, and  of  the  vertical  grating,  e,  between  which  is  the  true  fire-box,  7?,  and  in 
which  vent  the  air-passages,  n,  are  introduced  in  the  side  walls  of  the  generator.  The 
gases  evolved  in  the  generator  pass  through  the  grating,  F,  into  the  fire-box,  B  (closed 
above),  where  they  mix  with  the  air  warmed  against  the  stove  sides  and  streaming  in 
from  the  air-channels,  n,  and  are  ignited. 

The  forms  of  burners  by  which  a  perfect  combustion  is  effected  are  shown  in  the 
wood-gas  stove,  Fig.  70. 

If  the  generator  does  not  stand  directly  under  the  fire-box,  as  in  that  of  Boetius 
(Fig.  36),  gas-firing  involves  a  loss  of  heat.  As  compensation,  the  combustion-air, 
more  rarely  the  air  for  gasification,  is  strongly  heated  by  the  waste  heat. 

C.  W.  Siemens  effects  the  formation  of  gas  in  the  generator  by  means  of  heated  air 
(Fig.  71).  The  fuel  is  introduced  by  the  hopper,  £;  the  gases  are  carried  off  through  a 
great  number  of  channels  arranged  round  the  stove,  and  arrives  at  the  ring-shaped 
draught,  c.  which,  as  is  shown  by  dotted  lines  and  arrows,  leads  through  d  to  the 
furnace.  The  gases  meet  with  the  air  rising  from  the  regenerator  pipes  through  the 
channel  I,  and  burn.  After  the  flame  has  completed  its  work  in  the  heating  space  of 
the  furnace,  it  passes  out  opposite  to  the  entrance  through  apertures  which  lead  the 
gases  through  the  channels  &,  to  the  regenerator  flues,  e,  whence  they  ultimately 
arrive  at  the  chimney,  S.  The  air  required  for  the  combustion  of  the  gases  arrives  at 
the  regenerator  through  the  openings,  v,  which  lead  to  o,  which  in  turn  is  in  connection 


SECT. 


HEATING   ARRANGEMENTS. 


67 


at  the  other  end  with  the  channel  I,  already  mentioned.  A  part  of  the  air  coming 
from  the  regenerator  flues  may  be  led  to  the  generator  in  order  to  volatilise  the  fuel 
there,  or,  as  shown  in  the  figure,  the  air  needed  for  this  purpose  may  be  heated  in 

Fig.  71. 


separate  tubes  which  lead  to  a  blast,  s,  at  the  foot  of  the  generator.     The  ashes,  &c.,  fall 
into  a  reservoir  of  water  at  the  foot  of  the  generator.     The  steam  thus  produced  enters 


Fig.  73- 


Fig.  72. 


the  gas  generator,  where  it  is  de- 
composed on  contact  with  the  ignited 
coal,  and  serves  to  enrich  the  gases. 

The  preliminary  heating  of  the 
air  for  gasification  may  be  objec- 
tionable in  so  far  as  it  raises  the 
temperature  in  the  gas  generator, 
and  thus  increases  the  action  of 
the  slag  upon  the  masonry.  It  is 
of  value  only  when  the  generator- 
gases  enter  the  fire-box  at  a  high 
temperature. 

The  preliminary  heating  of  the 
air  for  combustion  is  of  much 
greater  importance.  It  is  effected  according  to  the  procedure  of  Fr.  Siemens  by 


Section  I. 


Section  III. 


passing  the  combustion- 
gases  which  leave  the  fur- 
nace at  a  high  tempera- 
ture through  a  grating  of 
stone  (regenerator),  and 
then  inverting  the  cur- 
rent and  causing  the  air 
for  combustion  to  ascend 
through  the  ignited 
stones.  According  to 
another  process  the  heat 
of  the  combustion-gases 
is  transferred  to  the 
ascending  air  by  partition 
walls  (Figs.  72  and  73). 


Fig-  74- 


68 


CHEMICAL   TECHNOLOGY. 


[SECT.  i. 


Fig.  74  shows  a  longitudinal  section  through  the  trough  and  the  regenerator  of  a 
Siemens  glass-melting  furnace  provided  with  regenerators  of  the  first  kind.  Fig.  75 
shows  a  horizontal  section  on  V,  VI,  and  Fig.  76  a  transverse  section  on  VII,  VIII r 
through  the  entire  furnace,  and  Fig.  7  7  the  section  of  a  work-place.  The  four  regene- 
rators, 72,  to  7?4,  lie  close 
alongside  each  other,  and 
form  a  connected  whole  with 
the  furnace,  thus  reducing 
the  loss  of  heat  by  radiation 
and  conduction.  The  greater 
part,  A,  of  the  regenerators 
is  lined  with  fire-stones,  but 
not  the  smaller  portion,  B, 
separated  by  the  wall,  m. 
This  part,  situate  next  to 
the  place  for  introducing  the 
materials,  takes  up  the  con- 
stituents of  the  charge,  so 
that  the  regenerators,  A, 
remain  clean ;  these  are 
easily  accessible  from  G,  as 
are  the  parts  B  from  the 
alternating  valves,  W.  The 
trough  itself  is  an  entire  whole,  in  consequence  of  which  repairs  are  seldom  needed. 
In  the  melted  glass  there  float  at  the  end  of  the  furnace  turned  towards  the  work- 
places, a,  rings  of  stoneware, 
whilst  the  flame  sweeps 
through  the  upper  part,  0, 
of  the  furnace,  so  that  the 
melting  of  the  glass  takes 
place  on  the  surface  only. 
The  bottom,  b,  and  the  sides, 
w,  of  the  trough  are,  as 
formerly,  surrounded  with 
air  refrigerators,  e,  in  which 
a  brisk  current  of  cold  air 
is  kept  up  by  means  of  the  chimneys,  s. 
The  trough  is  thus  not  only  better  pre- 
served, but  the  glass  is  prevented  from 
passing  through  the  joints. 

As  a  good  instance  of  the  second  method 
of  obtaining  heat  from  the  combustion- 
gases  we  may  take  the  so-called  Munich  generator  furnace  of  N.  H.  Schilling  (Figs.  78- 
to  82).  The  heat  necessary  for  gasifying  the  coke  enters  the  aperture,  A,  which  can  be 
Regulated  with  a  slide,  and  mixes  with  the  watery  vapours  rising  up  from  the  box,  B. 
The  gaseous  mixture  traverses  the  channels  c  to  c3,  is  heated  by  their  sides,  which  in 
turn  are  heated  by  the  escaping  smoke-gases,  passes  under  the  grate,  D,  and  through 
the  ash-pit,  w,  into  the  burning  stratum  of  fuel.  The  generator-gases  formed  pass 
through  the  channel  F  to  the  furnace,  and  meet  in  the  burners,  G,  with  the  air  pre- 
viously heated.  The  combustion-gases  traverse  the  retort  furnace  in  the  direction 
of  the  arrows,  leave  it  at  the  end  of  channel  z,  and  enter  into  the  regeneration 
system.  The  hot  gases  pass  through  channels  o  to  o3,  which  lie  between  the  channels 


Fig.  77. 


J3ECT.   I.] 


HEATING   ARRANGEMENTS. 


69 


CHEMICAL  TECHNOLOGY. 


[SECT. 


Fig.  82. 


n  to  w,,  for  warming  the  combustion-air,  then  through  channel  o4,  the  walls  of  which 
heat  the  mixture  of  gas  and  watery  vapour  passing  to  the  generator,  arrive  under  the 

water-cistern,  B,  at  r,  and  through  s  into  the 
smoke-pipe,  0. 

For  more  rapidly  transferring  the  heat  from 
the  smoke-gases  to  the  air  moving  towards  the 
furnace,  and  for  securing  the  structure  and 
tight  joints  of  the  so-called  regeneration,  the 
several  channels  are  traversed  by  perforated 
stones,  which  increase  the  heating  surface.  The 
slide  for  regulating  the  draught  in  the  chimney 
is  behind  the  regeneration,  not  behind  the  fur- 
nace. The  heating  surface  of  the  water-tank 
beneath  the  generator  is  arranged  so  that  the 
quantity  of  steam  which  is  sufficient  for  all 
cases,  1000  to  1300  kilos.,  may  be  produced, 
thus  completely  preventing  the  formation  of 
slag.  To  regulate  the  quantity  of  steam  pro- 
duced there  is  provided  a  valve,  P,  which  can  be 
set  at  pleasure,  thus  moderating  the  tempera- 
ture. If,  on  using  coke  with  from  14  to  16  per 
cent,  of  ash,  the  ash-pit  has  become  filled  in 
about  thirty -six  hours  with  the  residues  of  com- 
bustion, they  are  removed  as  follows : — Through 
the  openings,  e,  which  are  in  general  tightly 
closed,  there  are  thrust  iron  rods  to  catch  the 
fuel  in  the  generator.  The  covers,  R  and  S,  are 
removed,  and  the  ash  fallen  upon  the  grate  is 
taken  away.  All  the  apertures  for  cleansing 
are  closed  again.  The  water  which  has  evaporated  from  B  is  renewed  by  a  con- 
tinual flow  from  v ;  an  overflow  removes  any  superfluous  water.  In  order,  when 
setting  the  furnace  in  action,  to  remove  temporarily  the  regeneration  there  are 
connecting  channels,  U,  through  which  the  smoke-gases  may  be  passed  at  once  to  the 
chimney. 

Such  furnaces  have  been  in  regular  work  at  the  Munich  Gasworks  since  1881. 
Three  series  of  observations,  of  several  months  each,  gave  the  following  results : — 

Yield  of  gas  in  twenty-four  hours 2300  cubic  metres 

Coal  distilled  in  twenty-four  hours  in  eight  retorts          .        .         .  7350  kilos. 
Coke  consumed  per  furnace  in  twenty-four  hours  ....       800    „ 

Yield  of  gas  per  retort  in  twenty-four  hours 287  cubic  metres 

Gas  per  furnace  and  charge  in  four  hours 383  „ 

Gas  from  100  kilos,  of  coal 31  „ 

Coal  distilled  per  retort  in  twenty-four  hours 919  kilos. 

»>         »  -,         and  charge          ......       153      » 

Consumption  of  coke  (14  per  cent,  ash)  per  100  kilos  of  coal  dis- 
tilled       IO'9  „ 

Consumption  of  coke  (14  per  cent,  ash)  per  100  cubic  metres  of  gas        45^8  „ 

The  generator-gases  contain  as  a  mean  8'6  per  cent,  of  carbon  dioxide,  20-6 
of  carbon  monoxide,  15  of  hydrogen,  and  55-8  of  nitrogen.  They  enter  the  furnace 
at  about  1150°.  The  combustion-gases  contain  17  to  19  per  cent,  of  carbon  dioxide, 
about  2-5  per  cent,  of  oxygen  or  small  quantities  of  carbon  monoxide.  They  leave  the 
furnace  at  about  1400°.  After  having  traversed  the  flues  o  to  o3,  and  given  off  a  part 


Section  VII-VIJLI. 


SECT,  i.]  LIGHTING-GAS.  71 

of  their  heat  to  the  air  ascending  in  the  intervening  channels,  they  still  have  a  tempera- 
ture of  900°,  whilst  the  combustion-air  arriving  at  the  furnace  before  entering  the 
channels  m  to  m4,  has  become  heated  to  iooo°— 1100°.  Passing  further  down,  the 
smoke-gases  play  round  the  channels  c  to  c3,  and  heat  the  air  passing  to  the  generator 
to  350°  ;  finally,  on  passing  through  the  channels  r,  they  produce  the  steam  employed 
in  the  generator,  and  enter  the  chimney  at  about  550°. 

An  exit  temperature  of  1400°  without  regeneration  would  represent  a  loss  of  64 
per  cent,  of  the  heating  value  of  the  coke  ;  but  by  the  regeneration  process  the  smoke- 
gases  are  cooled  down  to  550°,  and  the  loss  is  reduced  to  about  25  per  cent.  The  heat 
thus  recovered  is  conveyed  back  to  the  furnace,  20  per  cent,  by  the  heated  combustion- 
air,  6  per  cent,  by  the  preliminary  heating  of  the  generator-air,  about  5  per  cent,  is 
used  in  evaporating  water,  whilst  the  rest  is  lost  by  conduction  and  radiation  out- 
wards.* 

This  latter  way  of  recovering  heat  has  the  advantage  that  the  direction  of  the 
draught  does  not  require  to  be  changed  every  fifteen  or  thirty  minutes.  Care  must  be 
taken  that  the  divisions  between  the  channels  for  air  and  combustion-gases  are  air- 
tight, so  that  no  disturbing  intermixtures  take  place.  This  point  has  to  be  deter- 
mined by  the  analysis  of  samples  of  gas  taken  from  channels  nv  z,  and  r. 

Gas-firing  gives  satisfaction  in  metallurgy,  in  glass  manufacture,  and  in  burning 
clay  and  cement. 

In  industrial  heating  operations,  the  dissociation  of  the  gases  of  combustion  is 
without  importance. 

LIGHTING-GAS. 

History. — As  far  back  as  1727-1739,  Clayton,  Bishop  of  Cork,  and  Dr.  Hales 
observed  the  escape  of  gas  on  heating  coal.f  In  1767,  Dr.  Watson,  Bishop  of  Llan- 
daff,  observed  that  combustible  air  could  be  conveyed  through  pipes.  Pickel,  Professor 
of  Chemistry  at  Wiirzburg,  lighted  up  his  laboratory  in  the  gardens  of  the  Julius 
Hospital  with  gas  obtained  from  bones,  in  1876.  About  the  same  time  Dundonald 
made  experiments  at  his  country  seat  of  Culross  Abbey  on  lighting  with  coal-gas.  The 
first  question  for  him  had  been  the  production  of  gas- tar  as  a  by-product  of  the  coke 
manufacture.  The  workmen  fixed  iron  tubes  in  the  condenser  in  which  the  tar  was 
deposited,  and  kindled  the  escaping  gas  for  light  in  the  night.  Strictly  speaking,  the 
beginning  of  gas-lighting  took  place  in  1792,  when  Murdoch  lighted  his  house  and 
works  at  Redruth,  in  Cornwall,  with  gas  obtained  from  coal.  His  process  did  not 
become  known  on  the  Continent  until  about  ten  years  subsequently  ;  hence  the  French 
claim  the  invention  for  their  countryman,  Lebon,  who  in  1801  illuminated  his  house 
and  garden  with  gas  produced  from  wood.  The  enterprise  proved  a  complete  failure, 
on  account  of  the  feeble  illuminating  power  of  wood-gas,  and  was  soon  abandoned.  The 
first  gas  illumination  on  the  large  scale  was  installed  by  Murdoch  in  1802,  at  the  works 
of  Watt  &  Boulton,  the  Soho  Foundry,  near  Birmingham.  In  1804  he  fitted  up  a 
similar  installation  at  a  cotton-spinning  establishment  in  Manchester.  J  From  this 
time  the  use  of  gas  became  extended.  But  for  some  time  it  was  confined  to  factories. 
Its  introduction  into  daily  life  dates  from  1812,  when  the  streets  of  London  were 
lighted  with  gas.  In  1824  gas-lighting  was  introduced  into  Hannover,  and  other 
continental  cities  followed  the  example.  The  wood-gas  introduced  at  Pettenkofer's 
suggestion  into  Munich  and  other  South  German  cities  has  probably  been  everywhere 

*  Dingler's  Journal,  248,  p.  27. 

t  Indeed,  in  1659  Thomas  Shirley  is  said  to  have  ascribed  the  burning  exhaldtions  from  the  well 
of  Wigan  to  the  subjacent  coal-beds. 

+  Winzer,  who  converted  his  name  into  Winsor,  is  sometimes  regarded  as  a  discoverer  of  gas- 
lighting,  but  he  was  merely  the  inventor  of  gas  companies. 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


abandoned  in  favour  of  coal-gas.     For  small  installations  oil-gas  and  resin-gas  are 
convenient,  as  they  require  little  purification. 

For  the  production  of  lighting-gas,  coal  is  hea,ted  to  whiteness  in  retorts,  formerly 
made  of  cast-iron,  but  latterly  of  fire-clay.  As  the  source  of  heat,  the  residual  coke  is 
used,  being  formerly  burnt  in  common  grates.  During  the  last  ten  years  the  firing 
has  been  improved,  so  that  the  consumption  of  fuel  has  been  reduced  one-half.  In  the 
half-gas-firing  of  J.  Hasse  and  M.  Vacherot  the  fuel  is  introduced  (Figs.  83-85)  through 

Fig.  83. 


an  opening,  J3,  provided  with  a  tightly  fitting  door  and  laid  upon  the  grate,  A .  Slags 
and  ashes  are  removed  through  the  air-tight  door,  E.  When  both  doors  are  closed  the 
combustion-air,  regulated  by  the  slide,  F,  into  the  furnace  right  and  left  at  G,  traverses 

the  channels  in  the  direc- 
tion of  the  arrows,  and 
passes  through  the  slit  J 
to  the  left  and  right 
under  the  grate.  Where 
circumstances  permit,  air 
can  also  be  introduced 
xinder  the  flues  M  and 
JV,  and  conveyed  from 
thence  to  the  channels  //. 
The  products  of  combus- 
tion, after  they  have 
passed  uniformly  through 
the  furnace,  enter  the 
smoke  flue,  K,  from 
before  backwards,  down- 
wards in  L,  in  M  from 
behind  forwards,  and  in 
N  in  the  reverse  direction  to  the  chimney.  In  this  manner  the  products  of  com- 
bustion give  off  a  great  part  of  their  heat  both  to  the  air  entering  through  the  air- 
channels  H,  and  to  evaporating  the  water  in  the  tank,  0,  under  the  grate.  As  the 
fuel  is  packed  high  up  on  the  grate  and  maintained  at  the  same  height,  a  complete 
combustion  does  not  take  place,  but  there  is  formed  a  considerable  percentage  of 
carbon  monoxide,  for  the  combustion  of  which  a  further  supply  of  air  is  needful.  This 
secondary  combustion-air  enters  from  the  back  of  the  furnace  at  P,  where  its  access  is 


SECT.    I.j 


LIGHTING-GAS. 


73 


Fig,  87. 


regulated  by  the  slide,  Q.     It  traverses  the  air  channels,  R,  in  the  direction  of  the 
arrows,  and  arrives  through  the  slit  S  in  contact  with  the  gases  coming  from  the  com- 
bustion hearth.      The   channels   R  are 
heated  by  radiation  from  the  surround- 
ing masonry.     The  channels  II  may  be 
connected  with  the  channels  R  in  such 
a  manner  that  the  air  passes  through  H 
into  R. 

In  the  retort  furnace  of  Stedman, 
provided  with  a  gas-firing,  the  combus- 
tion-gases, as  shown  in  Figs.  86  and  87, 
pass  from  A  to  E,  or  from  a  to  e,  down 
into  the  chimney.  The  air  for  gasifica- 
tion enters  on  both  sides  at  J,  traverses 
the  channels,  i  to  6,  and  enters  into  the 
bed  of  coke  at  r.  The  air  for  combus- 
tion enters  at  /,  passes  through  //  to 
V,  and  meets  with  the  generator-gases 
at  VI. 

The  furnaces  of  Liegel   and  Klb'nne,  in  which  the  generator   is   built  into  tho 
furnace,  have  given  satisfaction  in  practice. 

The  furnaces  of  Hasse  and  Didier  have  much  similarity  with  the  Munich  furnace. 
The  air  for  gasifying 
enters  at  P  (Figs.  88  and 
89),  and  is  warmed  in 
channels  left  in  the 
masonry  of  the  generator 
outside  the  furnace.  The 
air  for  combustion  enter- 
ing at  S,  rises  in  the 
channels,  0,  whilst  the 
products  of  combustion 
pass  from  the  furnace 
down  through  the  chan- 
nels, and  yield  the  heat 
necessary  for  producing 
steam  in  the  tank,  D. 
The  steam  passes  under  the  grate  of  the  generator. 

Tar-firing. — In  consequence  of  the  reduced  value  of  tar  and  its  products,  it  is  in 
many  gasworks  advantageous  to  use  it  as  fuel.  Tar 
has  a  combustion-value  of  8500  to  9000  heat-units, 
and  is  blown  into  the  fire  in  a  state  of  fine  division  by 
compressed  air  and  steam.  Kb'rting's  pulveriser  (Fig. 
90)  allows  the  steam  to  issue  from  four  apertures  of 
i  mm.  in  diameter.  At  a  pressure  of  3  atmospheres 
these  apertures  let  pass  5  '4  kilos,  of  steam,  pulverising 
30  kilos,  of  tar.  At  the  exit  the  steam  takes  the  tem- 
perature of  100°,  is  heated  to  the  temperature  of  the 
furnace,  gives  up  heat  to  the  retorts,  and  leaves  the 
furnace  at  about  1000°.  It  thus  occasions  a  loss  of 
heat  corresponding  to  the  rise  of  temperature  from 
100°  to  1000°,  i.e.,  900°.  Steam  has  a  specific  heat  of  0-475— ^ 


Fig.  90. 


2'Aeer— Tar.     Dampf—  Steam. 

to  heat  i  kilo,  of 


74 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


steam  to  i°,  0*475  heat-unit  is  needed.  To  heat  5-4  kilos,  to  900°  there  are  needed 
5*4  x  900  x  o-475  =  23°8'5  heat-units.  From  the  30  kilos,  of  tar  burnt  in  this  time 
there  are  produced  260,000  heat-units,  so  that  the  loss  as  steam  does  not  come  to 
0-9  per  cent.  At  the  Hannover  Gasworks  100  kilos,  of  coal  are  degasified  along  with 
13-5  kilos,  of  tar.  Sometimes  tar  is  let  flow  into  the  generator. 

As  already  mentioned,  the  composition  of  the  volatile  matter  given  off  on  heating 
coal  fluctuates  greatly.  The  Paris  Gas  Company  experimented  at  their  works  at 
La  Villette  with  fifty-nine  kinds  of  coal,  and  very  carefully  with  twenty-three  of  the 
same,  using  36  tons  of  each. 

The  nitrogen  was  not  determined,  but  assumed  as  i  per  cent,  in  each  case ;  all  the 
coals  were  grouped  in  five  classes. 


I 

II 

III 

IV 

V 

[Oxygen     ..... 

5-56 

6-66 

771 

lO'IO 

11-70 

Composition  of 

Hydrogen           .... 

5-06 

S'37 

5*40 

5-53 

5-64 

coal. 

88-^8 

86.97 

8  5  -89 

8r^7 

8  1  -66 

I  "OO 

I'OO 

I'OO 

I-QO 

I'OO 

100  '00 

lOO'OO 

lOO'OO 

lOO'OO 

lOO'OO 

Moisture  .         .         .   per  cent. 

2-17 

2-70 

3-31 

4'34 

6-17 

Products  of 

[Volatile    .                           „ 

26-82 

31-59 

33-80 

37'34 

39-27 

distillation. 

Coke         .                 .         ,, 

73-18 

68-41 

66  -20 

62-66 

6073 

(Coal          .                 ... 

0*04 

7-06 

7  -2i 

8-18 

10-73 

Ash  in 

Coke 

12-35 

10-32 

10  -80 

I3-05 

17-76 

rGas  .                       cubic  metres 

30-13 

31-01 

30-64 

2972 

27-44 

loo  kilos,  of 
coal  yield 

„    .                           .          kilos. 
Coke 
Tar   . 

13-70 
77-81 
3-90 

15-08 
74-70 
4-65 

15-81 
72-31 
5-08 

16-95 
68-96 

5-48 

17-00 
67-36 
5-59 

lAmmoniacal  liquor   .              „ 

4-59 

5'57 

6-80 

8-61 

9-86 

The  gas,  on  a  very  imperfect  examination,  showed- 


I 

II 

III 

IV 

y 

Carbon  dioxide     . 

1-470 

1-580 

1-720 

2-790 

3-130 

„       monoxide 

6-680 

7-190 

8-210 

9-860 

11-930 

Hydrogen     . 

54-210 

52-790 

50-100 

45-450 

42-260 

Methan  +  nitrogen 

34-370 

34-430 

35-030 

36-420 

37-140 

Benzoles 

0-790 

0-990 

0-960 

1-040 

0-880 

Other  gases  absorbed  in  bromine 

2-480 

3-020 

3-980 

4440 

4-760 

lOO'OOO 

lOO'OOO 

100  'OOO 

IOO.OOO 

loo-ooo 

Specific  gravity    

0-352 

0-376 

0-399 

0-441 

0-482 

Required  per  carcel     .         .          litres 

132-100 

III  -700 

103-803 

IO2-IOO 

ioi'8oo 

The  Scottish  cannels,  the  Boghead  minerals,  which  produce  no  residue  applicable  as 
fuel,  and  the  Australian  kerosene  shales,  which  likewise  leave  no  coke  on  distillation, 
are  almost  exclusively  used  at  gasworks  to  improve  the  gas  from  common  coal,  and  are 
added  in  proportions  varying  from  5  to  50  per  cent.  The  following  are  the  yields 
obtained  from  these  ingredients  : — 


Coal. 

Gas  per  100  Kilos. 

Luminous  Power 
of  150  Litres  of 
Gas. 

Coke  from 
100  Kilos. 

Scotch  cannel      ....... 

30-4-35-2 

18-1-43-4 

30-65 

Boghead. 

Scotch         

29-2-38-8 

26-3-62-6 

23-62 

Australian  

39-5-4I-5 

48-0-53-6 

30-36 

Of  the  nitrogen  in  coal,  according  to  Schilling,  u  to  17  per  cent,  are  given  off  as- 
ammonia,  57  to  70  per  cent,  are  left  in  the  coke,  and  the  rest  is  not  determined. 


LIGHTING-GAS. 


75 


Purification  'of  the  Gas. — The  crude  gas  evolved  in  the  retorts  rises  through  a  wide 
iron  pipe,  and  enters  by  way  of  the  bent  tube,  B  C,  the  hydraulic  main,  D  (Fig.  91),. 

Fig.  91.  Fig.  92. 


Fig-  93- 


which  runs  over  the  entire  range  of  furnaces,  so  as  to  receive  the  delivery  pipes  of  all 
the  retorts.  Here  a  portion  of  the  tar  and  the  ammoniacal  liquor  are  condensed,  and 
are  run  off  only  so  far  that  the  exit-pipes  may  plunge  in  to  the  depth  of  a  few  centi- 
metres to  prevent  the  gas  from  going  back  into  the  retorts.  An  exhauster  is  intro- 
duced into  the  system,  generally  after  the  washing  apparatus,  to  prevent  over-pressure. 

From  the  main  the  gas  arrives  at  the  condenser.  This  generally  consists,  as  shown 
in  section  (Fig.  92),  of  a  series  of  vertical  iron  pipes,  connected  above  by  arched  pipes, 
and  standing  below  on  the  rectangular  cast-iron  chest,  P.  The  latter  is  divided  into 
compartments,  both  in  length  and  breadth.  Each  compartment  has  an  entrance  pipe, 
TO,  and  an  exit  pipe,  n.  The  partitions  do  not  reach 
quite  down  to  the  bottom,  so  that  the  liquid  which 
closes  the  compartments  can  move  freely  through 
the  entire  chest.  In  this  chest  the  gas-liquor  and 
the  tar  are  collected.  The  level  of  the  liquid  is 
regulated  by  the  exit  tubes,  d,  through  a  pipe  bent 
as  a  siphon.  The  entrance  pipes,  which  lead  down- 
wards, dip  a  little  into  the  liquid,  so  that  the  gas 
is  compelled  to  pass  through. 

For  separating  the  residue  of  tar  and  ammonia 
the  gas  is  conducted  into  a  scrubber.  It  consists 
generally  of  cylinders,  A  (Fig.  93),  3  or  4  metres 
in  height,  filled  with  fragments  of  coke,  upon  which 
a  hollow  rotating  cross  tube  constantly  sprinkles 
water.  The  gas  enters  through  the  pipe,  i,  moves 
upwards  among  the  wet  coke,  passes  down  through 
the  tube,  m,  and  then  enters  a  second  scrubber. 
At  the  lowest  part  of  the  pipe  there  is  an  arrangement  for  removing  the  washing 
water  and  the  tar  which  collects  in  the  receiver,  M.  Of  late  the  gas  is  often  caused 


7 6  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

to  pass  through  sieves  which  dip  into  water  or  over  which  water  flows.  For  the 
complete  separation  of  the  tar  it  is  desirable  that  the  gas  should  be  compelled  to 
impinge  repeatedly  on  cold  surfaces. 

Finally,  the  gas  is  led  into  the  purifiers  in  order  to  remove  carbon  dioxide  (other 
than  that  combined  with  ammonia),  sulphuretted  hydrogen,  carbon  disulphide,  ammo- 
nium cyanide,  &c. 

The  milk-of-lime  purifier,  introduced  by  Clegg,  has  been  superseded  by  the  dry- 
lime  purifier  (moist  calcium  hydroxide).  In  order  to  give  the  slacked  lime  a  loose 
consistence,  and  to  facilitate  the  passage  of  the  gas  to  be  purified,  it  is  mixed  with 
sawdust,  spent  tar,  &c.  Such  mixtures  are  so  loose  that  they  may  be  laid  on  sieves  in 
layers  of  1 5  to  20  centimetres  in  thickness  without  presenting  any  important  resistance, 
and  that,  in  five  layers  of  20  centimetres  each  and  spread  out  in  the  purifiers,  they  do 
not  require  a  pressure  of  more  than  2  or  3  centimetres  of  water. 

According  to  Veley,  the  first  product  formed  in  this  process  is  calcium  hydro- 
sulphate.  Gas  lime  contains,  along  with  unchanged  calcium  hydroxide  and  a  little 
calcium  cyanide,  calcium  hydrosulphate  in  such  quantity  that  gas  lime  is  used  by 
tanners  for  unhairing  hides. 

Purifying  with  Oxide  of  Iron. — Though  copperas  was  proposed  for  removing 
ammonium  sulphide  from  gas,  and  used  as  early  as  1835,  Mallet  (1840)  was  the 
first  to  introduce  metallic  salts,  and  especially  manganous  chloride  (which  was  then 
produced  extensively  at  the  chloride  of  lime  works),  and  also  ferrous  chloride  for  the 
purification  of  gas  on  the  large  scale. 

Of  much  greater  importance  is  the  so-called  "  Laming's  mass,"  introduced  by 
Laming  in  1847.  As  at  present  used,  it  consists  of  ferrous  sulphate  with  lime,  to 
which  sawdust  is  added  to  render  the  mass  loose.  The  ferrous  sulphate  is  converted, 
with  the  lime,  into  ferrous  oxide  and  calcium  sulphate ;  the  original  blackish-green 
•colour  of  the  mixture  is  changed,  by  turning  over  and  exposure  to  the  air,  to  a  red,  when 
we  have  a  mixture  of  ferric  hydroxide  and  gypsum.  The  mass  is  used  in  dry  purifiers. 
Since  it  has  been  observed  that  the  lime  is  of  no  consequence,  iron  or  manganese  oxide, 
or  preferably  bog-iron  ore,  is  almost  universally  used  instead  of  Laming's  mass.  It  is 
ground  fine,  mixed  with  an  equal  bulk  of  sawdust,  moistened,  and  used  for  purifying. 
Instead  of  the  natural  oxide,  the  residues  from  the  reduction  of  nitrobenzol  by  means 
of  iron-filings  (in  the  aniline  manufacture)  may  be  used. 

According  to  R.  Wagner,  the  ferric  oxide  of  Laming's  mass  is  first  converted  by 
the  hydrogen  sulphide  into  iron  sesquisulphide,  and  this  compound  then  passes  into 
ferric  oxide,  giving  up  its  entire  amount  of  sulphur. 

If  Laming's  mass  has  been  in  use  for  a  long  time,  its  efficacy  falls  off,  since  the 
sulphur  accumulates  up  to  40  per  cent.,  and  the  particles  are  coated  with  a  glutinous 
layer,  which  prevents  contact  with  the  gas.  From  the  exhausted  mass  the  sulphur 
•can  be  recovered  by  fusion  under  water  at  high  pressure  or  by  extraction  with  carbon 
disulphide ;  or,  after  the  ammoniacal  salts  and  the  iron  cyanide  (the  latter  in  the  form 
of  calcium  ferrocyanide)  have  been  removed  by  lixiviation,  the  mixture  is  roasted  in 
kilns,  thus  producing  sulphurous  acid  for  the  manufacture  of  sulphuric  acid ;  and,  on 
the  other  hand,  iron  oxide,  which  may  be  employed  anew  in  the  purification  of  coal-gas. 

For  desulphurising  coal-gas  the  mass  of  Lux  has  been  found  satisfactory.  It  consists 
of  65  parts  ferric  hydroxide,  5  parts  sodium  carbonate,  and  30  parts  clay,  sand,  &c. 
The  recent  mass  takes  sulphuretted  hydrogen  completely  up  at  a  velocity  of  16  mm. 
per  second.  For  old,  regenerated  mass  the  limit  is  a  velocity  of  5  mm.  per  second.  For 
«very  100  cubic  metres  of  gas  daily  the  purifiers  must  have  at  least  a  transverse  section 
of  0^23  square  metre. 

Ammoniacal  Purifying. — According  to  Glaus,  the  gas  when  freed  as  completely  as 
possible  from  tar  passes  through  six  scrubbers  (Fig.  94).  Almost  all  the  carbon 


SECT.    I.] 


LIGHTING-GAS. 


dioxide  is  removed  in  the  first,  A.  In  the  second  it  loses  the  last  trace  of  carbon  dioxide, 
together  with  the  larger  portion  of  hydrogen  sulphide.  At  the  upper  end  of  this 
scrubber,  Av  the  ammonia  arriving  from  the  stills  enters  in  a  continuous  current,  and,, 
flowing  along  with  the  partially 

purified  coal-gas,    it    passes   into  Fig-  94- 

the  next  scrubber,  Ar  Here  the 
last  trace  of  hydrogen  sulphide  is 
removed,  and  at  the  same  time  a 
great  part  of  the  carbon  disulphide 
contained  in  the  crude  gas  is 
eliminated.  In  the  liquid  con- 
tained in  this  scrubber  the  chief 
part  of  the  ammonia  is  free,  and 
much  of  the  rest  exists  as  ammo- 
nium sulphide.  Hence  the  con- 
ditions for  removing  carbon  disulphide  from  crude  gas  in  this  scrubber  are  favourable. 
However,  in  this  washer  alone  there  is  not  presented  to  the  gas  a  sufficiently  large 
surface  moistened  with  the  liquid  to  effect  the  maximum  possible  removal  of  carbon 
disulphide.  On  this  account  the  contents  (e.g.,  coke)  of  the  fourth  and  fifth  scrubbers, 
which  may  be  named  carbon  disulphide  scrubbers,  are  kept  moistened  with  a  small 
portion  of  the  liquid  from  the  bottom  of  the  second  or  third  scrubber.  From  the  fifth 
scrubber  the  gas  passes  into  A.a.  Here  the  last  trace  of  ammonia  is  washed  out  and 
the  gas  issues  perfectly  purified.  Over  this  scrubber  is  a  cistern  into  which  the 
exhausted  liquid  from  the  distillation  of  ammonia,  after  it  has  passed  through  a  refri- 
gerator, is  pumped. 

A  quantity  of  ammonia  is  stored  up  in  the  scrubbers  and  in  the  apparatus  for  the 
recovery  of  ammonia,  thirty  to  fifty  times  larger  than  the  quantity  required  for 
taking  up  the  impurities  in  the  largest  quantity  of  crude  gas  which  passes  hourly 
through  the  scrubbers. 

If  only  an  open  fire  or  enclosed  steam  were  used  for  the  distillation  of  the 
ammoniacal  liquid,  after  a  short  time  it  would  become  a  saturated  solution  of  cyanides 
and  would  have  to  be  removed  from  time  to  time.  Hence  the  distillation  is  preferably 
effected  with  open  steam,  for  which  the  waste  steam  of  the  engine  may  be  employed. 
An  essential  feature  in  the  purification  of  crude  gas  with  ammonia  is  the  recovery  of 
the  cyanides.  The  liquid  contains  ammonium  ferro-cyanide  and  sulpho-cyanide. 

Whilst  Glaus  distils  off  the  gas-liquor  and  passes  the  gaseous  ammonia  into  the 
scrubbers,  F.  C.  Hills  proposed  to  pump  the  liquor,  freed  from  carbon  dioxide  and 
hydrogen  sulphide,  direct  into  the  scrubbers.  In  consequence  of  successive  improve- 
ments the  two  processes  almost  coincide,  as  appears  from  the  following  report  by 
Watts  on  Hill's  process,  as  carried  out  by  the  South  Metropolitan  Gas  Company.  The 
five  scrubbers,  A  to  A4  (Fig.  94),  are  1-3  metre  in  width  and  6  metres  in  height ;  the 
sixth  scrubber  A5  is  1*5  metre  in  diameter  and  9  metres  high.  The  crude  gas  enters  the 
first  scrubber  at  a,  passes  through  the  tube  e,  to  the  following  scrubbers,  and  escapes, 
purified,  at  g.  The  drawn-out  lines  show  the  circulation  of  the  liquid.  The  towers  B  are 
0-6  metre  broad  and  4-5  metres  high.  To  two  of  them  steam  is  conveyed  by  the  piped, 
so  that  the  liquid  trickling  through  the  towers  (fitted  up  in  the  manner  of  scrubbers) 
is  warmed  so  much  that  carbon  dioxide  and  hydrogen  sulphide  escape  whilst  the 
ammonia  is  distilled  off  in  the  tower  C.  The  washing  liquid  in  the  five  scrubbers 
contains  :  — 

A.  A4.  A3.  A2.  AI. 

Ammonia         .         .        .01  ...  1-5  ...         3'5  ...  5'o  ...  4-o 

Sulphuretted  hydrogen    .  ..  o'i  ...         I'S  ...  2'o  ...  i'5 

Ammonium  as  carbonate  ...  ...  i'O  ...  3'° 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


The  gas-liquor  on  entering  (I.)  and  leaving  (II.)  the  decomposers  B  contained  : — 

i.  ii. 

Ammonia .     4-50  ...         4-50 

Ammonium  as  carbonate   ....     4*00  ...         i'io 
Sulphuretted  hydrogen      .         .         .         .     1-08 

The  crude  gas  contains  o*  i  per  cent,  hydrocyanic  acid,  which  forms  this  cyanide  : — 

NH4CN    +    (NH4)S2    =    NH4CNS    +    (NH4),S ; 
then  with  carbon  disulphide — 

(NH4)2CS3    -    NH4CNS    +    2H2S. 

The  finished  gas  is  stored  in  large  bell-gasometers  and  conveyed  for  consumption  in 
cast-iron  mains  tarred.  The  distribution  in  houses,  &c.,  is  effected  through  wrought- 
iron  tubes,  more  rarely  leaden  ones.  [In  England  lead  and  composition  pipes  are 
unfortunately  the  most  common].  Copper  pipes  are  costly  and  may  become  dangerous 
from  the  formation  of  acetylene  copper: 

Examination. — For  checking  the  process  of  manufacture  the  carbon  dioxide  is 
determined  with  the  apparatus  already  described. 

The  amount  of  sulphur  is  determined  with  the  arrangement  shown  in  Fig.  95. 
The  tube  B,  about  25  centimetres  long,  is  secured  by  a  cork  to  the  lateral  neck  of  the 
"bottle  A,  which  is  also  25  centimetres  high.  The  gas,  accurately  measured,  is  con- 
veyed to  the  glass  tube  b  on  a  small  plate,  and  over  its  efflux 
point  there  is  an  under  glass  tube  e,  which  slides  up  and 
down  in  a  simple  holder,  so  that  the  whole  arrangement 
represents  a  glass  Bunsen  burner.  The  supply  of  gas  is  so 
arranged  that  about  20  litres  are  burnt  hourly.  Above  the 
repeatedly  bent  tube  c,  a  small  dropping  vessel  a  is  fixed, 
by  means  of  which  during  the  experiment  hydrogen  per- 
oxide, free  from  sulphuric  acid  and  slightly  ammoniaca!*,  can 
be  let  drop  so  slowly  that  every  hour  2  c.c.  may  flow  down 
into  the  tube  c  to  dissolve  the  last  traces  of  the  sulphurous 
and  sulphuric  acids  formed  out  of  the  gases  of  combustion 
as  they  ascend.  When  about  100  litres  of  gas  have  thus 
been  consumed,  the  tubes  B  and  c  are  taken  off,  rinsed  out 
with  a  little  water,  the  contents  of  the  bottle  A,  together  with 
the  rinsings,  are  heated  to  boiling,  acidified  with  hydrochloric 
acid,  and  precipitated  with  barium  chloride  in  the  ordinary 
manner.  If  the  ambient  air  is  not  free  from  sulphuric  acid 
and  hydrogen  sulphide,  the  whole  arrangement  is  fixed  higher 
and  the  interval  at  e  is  closed  in  a  suitable  manner,  so  that 
no  air  can  enter  except  through  pumice,  moistened  with 
strong  potassa  lye.  One  cubic  metre  of  gas  should  not  con- 
tain more  than  o-3-o'4  grain  sulphur.  In  London  0-57  grain 
sulphur  per  cubic  metre  is  permitted  ;  in  Leeds  0-45  grain  ; 
in  Cologne  0*23  to  0*39. 

For  determining  ammonia  in  purified  gas  200  litres  are 
drawn  through  10  c  c.  of  decinormal  hydrochloric  acid,  and 
the  excess  of  acid  is  titrated  back. 
The  complete  analysis  of  gas  is  effected  with  the  author's  apparatus,  Fig.  48. 
Carbon  dioxide  and  oxygen  are  determined  as  already  described,  the  tube  A  is  re- 
peatedly rinsed  with  water,  which  is  drawn  ofi  at  the  cock  d ;  to  remove  the  last  traces 
of  water  a  few  drops  of  sulphuric  acid  are  allowed  to  enter  A  through  the  funnel  t, 
the  mercurial  column  is  lowered  in  A»  and  the  acid  is  driven  out  with  mercury  through 


SECT.    I.] 


LIGHTING-GAS. 


79 


the  tube  d.  About  0-5  c.c.  of  strong  fuming  sulphuric  acid  is  allowed  to  enter  the 
tube  A  through  the  funnel  t,  and  then  the  sample  of  gas  from  the  tube  M.  In  about 
three  minutes  the  sample  of  gas  is  forced  back  into  M,  the  sulphuric  acid  is  let  out 
through  the  cock  d ;  the  funnel  t,  and  the  tube  A  are  repeatedly  rinsed  with  water,  and 
the  sample  is  measured  in  M. 

Of  this  gas  freed  from  CO2,  O,  and  from  heavy  hydrocarbons,  so  much  is  let  escape 
through  the  three-way  cock  that  there  only  remain  50-60  vols.  (at  ordinary  pressure) 
in  the  measuring  tube  M.  60  to  70  vols.  oxygen,  and  about  150  vols.  atmospheric  air 
(containing  a  known  amount  of  oxygen),  are  allowed  to  enter,  measured  ;  the  mixture  is 
ignited  by  a  spark  between  the  platinum  wires,  the  quantity  of  the  residual  gas  is 
determined  and  its  proportion  of  COa  and  O. 

The  composition  of  a  sample  of  gas  from  the  Hannover  works  was : — 


Benzol,  C,.H6 

Propylene,  C3H(. 

Ethylene,  C,H4 

Methane,  CH4 

H 

CO 

CO2      . 

O    "      . 

N 


0-69 
0'37 

2'II 

37*55 
46-27 
II-I9 

0-81 

trace 

i -or 


For  checking  the  production  Lux  recommends  a  continuous  determination  of  the 
specific  gravity.  The  gas  enters  through  the  flexible  pipe  a  (Fig.  96),  the  mercurial 
joint  and  the  narrow  tube 

into  a  hollow  glass  ball,  fixed  N 

on  ,one  arm  of  a  lever,  and 
escapes  again  at  z.  If  the 
gas  becomes  heavier,  the  ball 
winks ;  if  lighter,  it  rises. 

Wood-gas. — Lebon,  as 
far  back  as  1799,  busied 
himself  with  the  preparation 
of  illuminating  gas  from 
wood.  His  "  thermo-lamp  " 
was  quickly  abandoned,  as 
its  light  was  not  compar- 
able with  that  of  coal-gas. 
Pettenkofer  found  in  1849 
that  if  wood  is  carbonised 
at  a  high  temperature  the 
gas  is  more  luminous.  But,  as  already  stated,  even  this  superior  wood-gas  has  been 
generally  superseded  by  coal-gas. 

Resin-gas. — Colophonium  was  temporarily  used  for  the  production  of  illuminating 
gas  in  several  cities  in  England  and  the  Continent,  but  it  has  been  given  up. 

Peat-gas. — Purified  peat-gas,  according  to  Reisig,  contains — 


Heavy  hydrocarbons 

Methan  . 

Hydrogen 

Carbon  monoxide  . 

C02andH2S  . 

Nitrogen 


I. 

9-52 

42-65 

27-50 

20-33 

traces 


II. 

13-16 
33-00 
35-18 
18-34 

0-32 


Peat-gas  will  probably  never  be  used  on  a  large  scale. 


So 


CHEMICAL   TECHNOLOGY. 


[SECT. 


i. 


Oil-gas. — If  fats,  paraffine  oil,  petroleum  residues,  &c.,  are  strongly  heated  they  are 
almost  entirely  gasified,  and  form  a  heavy  gas  of  great  illuminating  power. 

For  this  purpose  the  apparatus  of  J.  Pintsch  is  most  generally  used.  He  lets  the 
oil  flow  slowly  down  through  a  U-tube  into  the  iron  retort  d  (Figs.  97  and  98),  falling 


Fig.  97- 


Fig.  98. 


Sections  I-II. 

into  the  vessel,  e,  where  it  is 
completely  evaporated,  thus 
facilitating  the  cleansing  of 
the  retorts.  The  vapours  of 
oil  produced  here  and  already 
partially  gasified,  pass  through 
the  connection,  i,  into  the 
lower  cast-iron  retort,  /,  in 
which,  for  the  promotion  of 
gasification  there  is  inserted  a 

piece,  s,  of  clay  or  iron,  composed  of  discs  connected  by  a  longitudinal  rod.     The  gas 
passes,  now,  to  deposit  tarry  vapours,  through  the  pipe,  </,  to  the  receiver,  h.     The 
pipe,  g,  is  provided  with  ball  joints,  so  as  to  follow  the  expansion  of  the  retort. 
Other  devices  have  been  proposed  by  Hirzel,  Kiihnel,  Macadam,  and  Briehm. 
Oil-gas  generally  requires  no  particular  purification.     According  to  Hilger  (1874), 
paraffine- oil  gas  has  the  following  composition  : — 


Heavy  hydrocarbons 
Methan 
Hydrogen     . 
Carbon  monoxide 
dioxide    . 


28-91 

54 '92 

5-65 

8-94 

0-82 


Oil-gas  compressed  in  iron  cylinders  at ,  a  pressure  of  six  to  eight  atmospheres  is  of 
great  value  for  lighting  railway  carriages.  Oil-gas  is  also  suitable  for  small  installa- 
tions. 

Air-gas. — If  atmospheric  air  is  saturated  with  the  vapours  of  volatile  hydrocarbons, 
especially  the  so-called  petroleum  ether,  it  yields  an  illuminating  gas  which  can  only 
l>e  conveyed  to  short  distances,  and  cannot  bear  low  temperatures. 

The  uses  of  coal-gas  are  too  familiar  to  need  description.* 


MINERAL  OIL. 

According  to  Herodotus,  the  mineral  oil  of  the  Island  of  Zante,  which  he  names 
pissasphaltum,  was  used  for  embalming  corpses.  Plutarch  describes  a  burning  pool 

*  W.  J.  Cooper  has  patented  a  process  for  improving  the  quality  both  of  coal-gas  and  of  coke, 
by  adding  to  the  coal  before  distillation  a  quantity  of  lime.  The  coke  as  well  as  the  gas  is 
alleged  to  be,  to  a  great  extent,  freed  from  sulphur,  so  that  the  purification  of  the  gas  is  much 
simplified.  Experimental  working  seems,  in  some  cases,  to  have  given  satisfactory  results,  but  we 
<lo  not  know  that  the  process  has  as  yet  been  formally  adopted  by  any  gas  company. 


SECT,  i.]  MINERAL   OIL.  8t 

of  oil  near  Ecbatana,  and  Pliny  and  Dioscorides  assert  that  the  petroleum  of  Agri- 
gentum,  in  Sicily,  was  used  by  the  inhabitants  for  lighting  purposes.  The  mineral  oil 
wells  of  Baku  were  known  in  pre-historical  ages,  and  the  same  may  be  said  of  the 
springs  of  Rangoon.  The  Hannoverian  oil-wells  were  probably  found  by  the  first  settlers 
in  that  district,  and  their  product  was  used  as  a  lubricant  and  a  medicine  500  years 
ago.  The  small  spring  at  Tegernsee  has  been  known  since  1430.  But  mineral  oils 
have  first  become  of  importance  in  commerce  since  1879,  when  the  deposits  of  North 
America  were  systematically  worked. 

Several  deposits  in  Hannover,  Holstein,  and  Alsace  have  been  discovered  in 
Germany.  In  the  Austrian  Empire  the  Galician  springs  are  of  importance,  and 
petroleum  extends  from  Austrian  Silesia,  through  Hungary,  to  Transylvania,  as  also 
in  Lower  Austria,  Salzburg,  Carinthia,  Tyrol,  Croatia  and  Dalmatia.  In  Roumania 
there  is  mineral  oil  to  a  considerable  extent.  In  Russia,  the  springs  of  Baku  appear 
inexhaustible ;  in  some  places  fountains  of  oil  shoot  up  to  the  height  of  30  metres,  and 
flow  away  unutilised. 

There  are  oil-springs  in  Burma  (Rangoon),  in  Assam,  and  in  the  North-western 
Provinces  of  India ;  in  Java  and  China.  In  Japan  petroleum  has  been  known  to  occur 
for  1200  years,  but  it  has  only  been  collected  during  the  last  ten  years;  there  are  now 
five  refineries  at  work.  Mineral  oil  has  been  found  in  South  Australia  and  New 
Zealand.  The  islands  of  Cuba,  Trinidad,  and  Barbadoes  produce  petroleum,  as  do  also 
Mexico,  Bolivia,  Brazil,  and  the  province  Jujuy,  in  La  Plata.  North  America  is  espe- 
cially rich  in  petroleum.  The  oil  region  of  Pennsylvania  is  a  narrow  belt  of  country 
about  100  kilometres  in  length,  between  Lake  Erie  and  Pittsburg.  There  is  also  an 
important  oil  region  in  Canada. 

Concerning  the  origin  of  petroleum,  the  most  conflicting  views  have  been  advanced 
by  ehemists  and  geologists.  Some  authorities  (Berthelot,  Byasson,  and  Mendeleeff} 
hold  that  it  has  been  formed  from  inorganic  materials.  Dumas,  Rose,  and  Bunsen 
assume  that  mineral  oil  is  derived  from  the  hydrocarbons  of  the  deposits  of  rock  salt. 
Gregory  and  Kobell  asserted  that  it  was  a  product  of  the  distillation  of  coal,  of  which 
anthracite  is  the  solid  residue.  The  predominating  view  at  present  is  that  petroleum 
has  been  formed  by  the  decomposition  of  organisms  at  low  temperatures.  Well, 
Kruger,  and  Windakiewicz,  ascribe  to  it  a  vegetable  origin,  whilst  Hoefer,  Bertels, 
Miiller,  and  Fraas  consider  it  as  a  product  of  the  remains  of  animals. 

Mineral  oil  is  rarely  obtained  by  mining.  In  North  America  deep  borings  are  the 
usual  source,  and  the  same  system  is  extending  in  Hannover,  Galicia,  and  at  Baku.  It 
is  noteworthy  that  the  upper  oil  region  of  Pennsylvania,  once  so  productive,  has  been 
almost  entirely  exhausted  in  ten  years,  whilst  the  lower,  more  southern  oil  region, 
which  was  only  opened  up  in  October  1865,  now  supplies  all  the  petroleum  exported 
from  Pennsylvania.  The  Canadian  wells  generally  run  dry  in  about  three  years.  As 
the  total  average  yield  of  a  well  is  10,540  hectolitres,  and  as  15  per  cent,  of  the  borings 
in  Pennsylvania  are  unsuccessful,  Hoefer  calculates  the  cost  of  i  hectolitre  of  crude  oil 
at  the  well  at  5-8  shillings ;  after  carriage  in  a  pipe  line  6|  shillings,  or  for  a  barrel  of 
42  gallons  2-58  dollars,  so  that  in  the  years  1873  *°  J^75>  an(*  again  in  the  first  seven, 
months  of  1876,  the  oil  proprietors  were  working  at  a  decided  loss.  In  Galicia,  accord- 
ing to  Strippelmann,  the  cost  of  100  kilos,  of  crude  oil  is  6'i  shillings. 

Hannover  and  Alsace  yield  but  little  oil ;  Galicia  produces  yearly  800,000  hecto- 
litres, and  the  Caucasus  4  millions.  The  production  of  crude  oil  in  Pennsylvania  rose 
from  2000  barrels  (at  159  litres)  in  1859  to  ten  million  barrels  in  1874.  In  1859  the 
price  was  20  dollars  per  barrel,  and  in  1874  it  had  fallen  to  1*29  dollar.  The  total 
exportation  of  the  United  States  in  1886  and  1887  was  : — 


82 


CHEMICAL   TECHNOLOGY. 


[SECT.  i. 


1886. 

1887. 

1887. 

hectolitres. 

hectolitres. 

dollars. 

Crude  oil     .... 
Benzene       ....                          . 
Lighting  oil         ...                           . 
Lubricating  oil  and  Paraffine                       _. 
Residues     .... 

289,320 
54,223 
1,793.750 
52,111 
7,556 

305,640 
46,786 
1,759,108 
77,091 
",325 

5,HO,737 
10,439,195 
35,401,044 
3,504,942 
I4I>350 

The  total  value  was — 


1886. 
1887. 


47,016,095  dollars 
45,231,988      „ 


ioo  litres  of  crude  oil  yield  on  the  average  76  litres  of  lighting  oil,  12  litres  of 
gasoline,  benzene,  &c.,  3  litres  lubricating  oil,  and  9  litres  of  residues. 

In  Pennsylvania,  where  most  of  the  wells  are  exhausted,  boring  is  now  not  remune- 
rative. The  Bradford  district,  which  for  years  produced  more  than  the  total  consump- 
tion in  the  world,  furnishes  now  but  little ;  the  total  production  in  the  remaining 
districts  is  estimated  at  58,000  barrels  daily,  while  the  world's  consumption  is  now 
daily  70,000  barrels.  The  consumption  of  mineral  oil  has  increased  not  only  in  America 
— in  1882,  14,288,905  barrels — but  in  India,  China,  Japan,  England,  France,  Spain, 
and  along  the  Mediterranean.  The  increase  from  1876  to  1882  is  estimated  at  150  per 
cent.,  and  the  world's  consumption  for  1876  is  taken  at  10,000,000  barrels. 

The  Bradford  oil  now  produced  is  not  nearly  so  good  as  it  v/as  formerly  obtained 
from  Parker's  district  in  Pennsylvania.  Of  the  latter,  ioo  barrels  give  75  barrels  of 
refined  oil,  whilst  ioo  of  the  former  yield  only  66  barrels.  The  present  so-called 
refined  oil  is  a  product  of  very  light  and  heavy  oils ;  a  complete  intermixture  is  not 
always  practicable.  The  lighter  portions  rise  to  the  top  and  burn  first ;  whilst  the 
heavier  oils  collect  at  the  bottom,  and,  if  the  wick  is  too  thick  and  too  compactly 
woven,  and  if  the  burners  are  not  very  carefully  cleaned,  the  light  is  unsatisfactory. 
The  American  refineries  are  incessantly  striving  to  remedy  these  evils.  But  it  cannot 
be  denied  that  oils  which  have  passed  the  German  imperial  test  are  often  affected  with 
all  these  disadvantages.  The  consumption  in  Germany  for  1882  was  2,001,136  barrels. 

Natural  Gas. — The  gases  escaping  from  the  oil  wells  at  (i)  Cherrytree,  (2)  Burns, 
(3)  Leechburg,  (4)  Harvey,  and  (5)  Bloomfield,  have,  according  to  Sadtler  and  Wurtz, 
the  following  composition : — 


! 

2 

Carbon  dioxide    . 
Carbon  monoxide 
Hydrocarbons  (CnH2n)  . 
Methan  (CHJ       . 

2-28 

60-27 
22"  SO 

0'34 

trace 

75  '44 
6'io 

0'35 
0-26 
0-56 
89-65 
4*70 

0-66 
trace 

80-11 

I  2  -CO 

lO'II 

2-94 
82-41 

Ethylhydrogen  (C2Ha)  . 
Propylhydrogen  (C3H8) 
Oxygen 

Nitrogen 

6-80 

0-83 
7-32 

18-12 

trace 

4-39 

trace 

572 

trace 

0-23 
4'3i 

According  to  Fouque,  these  American  gases  belong  to  the  series  CnH2n+2 ;  these  are 
much  used  for  heating  steam  boilers,  for  smelting  furnaces,  &c. 

Mineral  oil  varies  in  consistence  from  a  thin  liquid  to  a  butter-like  fat ;  its  colour 
ranges  from  that  of  water  to  black,  and  it  has  sometimes  a  blue  fluorescence;  the 
specific  gravity  fluctuates  between  o'8  and  o'96. 

According  to  Boussingault,  the  oil  from  Bechelbronn  contains  hydrocarbons  of  the 
series  CnH2W+2,  petrolene  corresponds  with  the  formula  C9H16;  Blanchet  and  Sell  found 
in  their  researches  compounds  C^H^  and  CBH2JH., ;  Warren  de  la  Rue  and  Miiller 
found  CjjHjn  and  CBH2B+1.  The  oil  from  Sehnde  is  CnH2B,  but,  according  to  TJelsmann, 


SECT.   I.] 


MINERAL   OIL. 


it  belongs  to  the  series  CnH2rH_r  Bussenius  obtained  from  the  products  boiling 
between  90°  and  140°  a  trinitropetrol  C8H7(NO2)3;  according  to  Eisenstuck,  a  mixture 
chiefly  of  C9H7(N"O2)3  and  CgH7(NOj)3.  According  to  Le  Bell,  the  mineral  oil  of  the 
Lower  Rhine  consists  of  hydrocarbons  of  the  methan  and  ethylene  series ;  Joffre 
detected  in  the  mineral  oil  of  Bruxiere  de  la  Grue  and  Cordesse  hydrocarbons  absorbed 
by  sulphuric  acid  belonging  to  the  series  CnH3B  and  others  not  absorbed  of  the  series 
CnH2B+J,  especially  of  C8H18  to  C^H^.  In  the  Pennsylvanian  oil  Warren  found 


G6H14,  Pelouze  and  Cahours 


as  the  most  volatile  constituent  C5H12,  Lefebvre 


C4H10  and  C3H8,  Ronalds  C3H8  and  C2H6. 

According  to  Chandler  and  Schorlemmer,  the  oil  contains  the  following  hydro- 
carbons : — 


Name  (C«Hji2  +  2). 

Formula. 

Boiling-point. 

Specific  Gravity. 

Methan        ........ 
Ethan  

CH4 

C2H6 
CSH 

Gas 
» 

0*559 
i  x>^6 

Butane         
Pentane       

C4H10 

C5H)2 

i° 

30 

0-600 
0-628 

Name. 

Formula. 

Boiling- 
point. 

Specific 
Gravity. 

Name  (CnH«2). 

Formula. 

Boiling- 
point. 

Specific 
Gravity. 

Hexane 

C«H14 

69° 

0-664 

Ethylene 

C2H4 

Gas 

0-978 

Heptane 

C7HI6 

97'5 

0-699 

Propylene 

C3H8 

-18° 

Octane 

CSH13 

125 

0-703 

Butylene 

C4H8 

+  3 

Nonane 

CgH^ 

136 

0741 

Amylene         . 

C5H,0 

35 

O'663 

Dekane 

C10Ho,, 

158 

0770 

Hexylene        . 

C6H12 

69 

Endekane 

C,,H24 

182 

0-765 

Heptylene 

C,H14 

95 

Dodekane 

C12H2J 

198 

0776 

Octylene          . 

C8H,B 

104 

Tridekane 

('    H 
V-13rl2S 

216 

0-792 

Nonylene 

CUH18 

140 

Tetradekane 

^lAo 

238 

Dekatylene 

Cl0H'.0 

160 

Pentadekane 

C15H32 

258 

Endekatylenc 

C11H22 

195 

0782 

ClgH.jg 

Dodekatylene  . 

C12H24 

216 

C20H42 

Dekatritylene  . 

Ci3H2s 

235 

0791 

C23H4S 

Cetene    . 

Ci6Ha2 

275 

C^H^ 

? 

^20^40 

Paraffine 

C27H5i 

Cerotene 

C«HM 

ti                 • 

CsoHffi. 

370 

Melene    .         . 

CsoH,,, 

375 

Hemilian  has  furthur  obtained  from  the  Pennsylvanian  oil  a  hydrocarbon  melting 
above  300°,  petrocen  C32H22;  Rbttger  separated  from  the  fraction  boiling  between 
55°  and  65°  a  white  body  C5H10S03.  If  the  vapours  of  mineral  oils  boiling  at  low 
temperatures  are  passed  through  ignited  tubes,  we  obtain,  according  to  Prunier,  hydro- 
carbons of  the  series  0,11^. 

By  fractionated  distillation  of  the  crude  American  oils  the  following  average 
products  are  obtained  : — 


Rhigolen     

l*< 

-    18° 

—    4Q 

0-625 
o-66s 

IO'O 

82-150 

'  ««3 

0-706—0-742 

A'Q 

Kerosene     ........ 
Paraffine  oil         ...... 

55'0 

iq-tr 

-     I67 

too 

0-804 
0-85-088 

Eesidue  and  loss          .         .         . 

IO'O 

1 

Other  experiments  show  a  very  different  percentage  of  products. 


84 


CHEMICAL  TECHNOLOGY. 


[SECT.  i.. 


Manufacture. — According  to  Engler,  100  parts  of  crude  oil  contain — 

Pennsylvania.  Galicia.  Boumania.  Alsace. 

Easily  volatile  oils         .     10-20  ...  3-6  ...  4 

Lighting  oils          .         .     60-75  ...  55-65  ...         60-70  ...         35~4O 

Eesidues        .        .        .       5-10  ...  30-40  ...        25~35  ••        55~6o 

The  residues  of  the  refineries  at  Baku  are  the  most  valuable  ingredients,  on  account 
of  their  suitability  for  lubricants.  In  these  establishments  Engler  saw  only  the 
following  three  forms  of  boilers  : — 

(1)  Upright  wrought-iron  boilers,  of  a  cylindrical  shape  as  tall  as  wide,  with  a 
bottom  arching  upwards,  and  a  common  capital  leading  to  the  refrigerator.     Capacity, 
80  to  100  hecto-kilos,  if  filled  from  £  to  ^.     They  are  heated  with  naphtha  residues. 

(2)  The  so-called  waggon-boiler  (Figs.  99  and  100)  consists  of  the  chest-shaped 

Fig.  99. 


boiler  of  wrought-iron  plates  rivetted  together.  The  largest  size  are  7  metres  long, 
4  metres  wide,  and  3  metres  high  from  the  lowest  part  of  the  bottom  to  the  capital. 
It  has  a  bottom  with  three  undulations,  a  top  slightly  arched  upwards,  and  three 
capitals,  a,  which  carry  away  the  vapours  to  the  condenser ;  b  is  a  man-hole ;  c  are 
exit  supports  for  the  residues.  The  inner  arrangements  of  the  boiler  and  the  setting 
with  the  flues,  B  and  Bv  can  easily  be  understood  from  the  figures.  From  the  burner, 
r,  of  which  there  are  always  two  side  by  side,  and  which  open  into  the  arched  fire-flues, 
B,  Bv  the  flame,  for  the  protection  of  the  bottom  of  the  boiler,  strikes  first  through 


Fig.  101. 


Fig.  102. 


fire-proof  vaults,  turns  at  the  end  of  the  boiler,  the  bottom  of  which  is  here  lined  with 
fire-clay  tiles,  again  to  the  front,  ascends  and  turns  at  both  sides  of  the  boiler,  first 
backwards  and  then  downwards,  and  escapes  into  the  chimney  through  the  flue,  £2 
The  distillation  is  assisted  by  the  introduction  of  high-pressure  steam. 

If  such  a  boiler  (smaller  size)  contains  350  hecto-kilos.,  and  is  charged  with  300 
hecto-kilos.  of  crude  oil,  z|  distillations  can  be  effected  in  twenty-four  hours,  so  that 
700  to  800  hecto-kilos.  of  crude  oil  are  distilled,  which  corresponds  to  a  daily  production  of 


SECT.  I.]  MINERAL   OIL.  85 

200  to  250  hecto-kilos.  of  kerosene.  The  older  setting  in  which  the  supporting  walls 
fitted  into  the  depressions  of  the  wave-shaped  boiler,  so  that  the  three  protuberances 
lay  free  below  and  formed  three  fire-spaces,  has  been  abandoned,  as  it  caused  a  rapid 
destruction  of  the  bottom  of  the  boiler. 

3.  Roller-boiler.  Such  a  boiler  is  cylindrical,  and  is  shown  in  Figs.  101  and  102. 
The  materials  are  wrought-iron  plates,  10  mm.  in  thickness ;  the  length  is  from  5  to 
6  metres,  the  diameter  from  2  to  3  metres ;  the  smaller  make,  if  filled  to  |  or  £,  hold 
170  hecto-kilos.  (=1000  pud.),  the  largest  270  hecto-kilos.  It  has  not  been  found 
practicable  to  exceed  the  latter  size.  The  boiler,  A,  lies  on  bars,  a,  built  into  the  wall, 
and  is  further  kept  in  its  place  by  a  number  of  flanges  rivet  ted  to  its  sides.  As  a  pro- 
vision against  boiling  over,  there  is  a  large  dome,  B,  from  which  the  vapours  escape 
through  an  opening,  c,  into  an  iron  conductor  of  the  same  width,  by  which  they  are 
led  to  the  refrigerator.  The  apparatus  for  burning  residues  is  introduced  at  C ;  its 
flame  strikes  first  through  under  the  vault,  passes  at  the  opposite  end  over  the  vault 
into  the  space  Clt  draws  forward  in  the  opposite  direction  directly  under  the  boiler, 
distributes  itself  here  BO  as  to  pass  on  both  sides  of  the  boiler  in  its  original  direction 
through  (7,,  thus  arriving  into  the  common  exit  flue  and  into  the  chimney.  If  the 
flames  of  the  residues  were  let  pass  underneath  the  boiler  without  the  protective  vault, 
the  burner  would  have  to  be  placed  at  least  175  metre  below  the  bottom  of  the  boiler, 
on  account  of  the  intense  heat.  In  most  refineries  a  number  of  distilling  boilers  are 
fixed  side  by  side,  and  behind  them  runs  a  common  tube  with  naphtha,  from  which 
branch  pipes,  n,  pass  off  for  feeding  the  several  boilers,  as  also  a  steam-pipe,  d,  with  the 
branch -pipe  dv  in  order  to  assist  the  distillation  in  each  by  the  introduction  of  high- 
pressure  steam.  E  is  the  outflow  for  the  residues  placed  at  the  lowest  point.  The 
man-hole  serves  for  cleaning  out  the  boiler.  As  condensers,  water  refrigerators  are 
uniformly  used  ;  they  are  generally  placed  behind  the  distilling  boilers,  and  connected 
with  the  capitals  by  means  of  iron  pipes,  either  directly  or  with  the  interposition  of 
one  or  more  dephlegmators. 

As  wood  and  coal  are  wanting  at  Baku,  the  residues  boiling  at  high  temperatures 
are  largely  used  as  fuel.  For  distilling  100  parts  of  crude  F- 

oil  there  are  used  3  to  4  parts  of  these  residues,  called 
by  the  Tartar  workman  "  Massud,"  and  by  the  Russians 
"  Astatki." 

The  combustion  of  these  residues  is  effected  by  pulver- 
ising them  by  means  of  high-pressure  steam  ;  pulverising 
by  means  of  air  does  not  answer.  The  air  entering  is  sufficient  for  combustion,  and 
the  temperature  of  the  flames  is  enough  to  melt  wrought-iron.  Fig.  103  shows  a 
burner  much  used  at  Baku ;  it  consists  of  an  iron  tube,  D,  of  the  internal  diameter 
of  26  mm.,  flattened  at  its  front  end,  so  that  there  only  remains  a  slit  of  £  to  i 
millimetre,  through  which  the  steam  can  pass.  The  residues  are  brought  up  through 
the  tube,  N ;  the  thick  oil  running  out  at  its  end  is  distributed  so  as  to  flow  down 
over  the  steam  slit,  when  it  is  finely  pulverised  and  then  burnt.  The  arrangement 
of  this  burner  under  a  boiler  maybe  seen  from  Figs.  99  and  100. 

The  chemical  purification  of  the  kerosene  obtained  on  distillation  is  effected  by 
treatment  with  sulphuric  acid,  caustic  soda,  and  water.  The  apparatus  consists  of  two 
iron  receivers  of  a  cylindrical  shape,  set  above  each  other  like  steps.  The  bottoms  are 
shaped  like  funnels,  with  an  outflow  valve  at  the  bottom,  so  that  the  contents  of  the 
upper  tank  can  conveniently  flow  into  the  lower,  and  from  this,  again,  into  the  store 
tank.  The  upper  receiver,  for  treating  the  crude  oil  with  sulphuric  acid,  is  lined  with 
lead. 

The  "  souring  "  of  the  oil  is  effected  by  an  intimate  mixture  with  strong  sulphuric 
acid  containing  at  least  92  per  cent,  of  monohydrate.  The  quantity  used  must  be  the 


86  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

larger  the  more  rapidly  the  oil  has  been  distilled.  In  well-managed  works  it  does  not 
exceed  0*9  per  cent.  The  acid  trickles  in  slowly  through  a  ring  of  perforated  tubes 
with  constant  stirring,  which  is  kept  up  for  one  and  a-half  to  two  hours;  the  oil 
becomes  heated,  and  sulphurous  acid  is  given  off.  It  is  let  settle ;  the  acid  which  col- 
lects below  is  let  off  at  a  special  branch-pipe,  so  that  it  may  be  used  again,  and  the 
kerosene  is  treated  a  second  time  with  fresh  acid.  After  this  second  souring  follows  a 
washing  process  with  cold  water,  which  is  not  especially  mixed  with  the  oil,  as  the 
separation  would  be  too  tedious.  After  settling  for  one  hour,  the  oil  is  run  off  into  the 
lower  tank  for  treatment  with  soda-lye.  The  lye  is  used  first  at  sp.  gr.  1*28  to  i  '35,  and 
then  a  weaker  lye  is  introduced.  The  quantity  of  caustic  soda  used  should  not  exceed 
0*3  per  cent. 

An  exactly  neutral  reaction  is  aimed  at  in  many  refineries.  Water  is  not  applied 
after  the  soda  process.  To  test  kerosene  for  organic  acids  (derived  from  the  oil),  a 
sample  is  shaken  up  with  2  per  cent,  of  soda-lye  at  sp.  gr.  1-2,  let  settle,  and  the  clear 
soda-liquid  is  acidified.  The  turbidity  -arising  shows  the  amount  of  the  existing  acid. 
To  ascertain  if  the  treatment  with  sulphuric  acid  has  been  sufficient,  a  specimen  is 
shaken  up  with  a  few  drops  of  soda-lye  to  form  an  emulsion,  which  by  reflected  light 
must  appear  of  a  pure  white  without  any  yellow  tinge.  The  colorimetric  test  is  effected 
with  Stammer's  colorimeter.  A  good  burning  oil  is  colourless  and  clear  as  water. 

The  photometric  test  is  executed  with  Bunsen's  photometer  with  the  mirror  com- 
parison, the  German  normal  candle  being  used  as  a  standard.  The  distillation  trial  is 
carried  out  with  a  Glinsky  dephlegmater,  filling  the  boiling  flask  each  time  with  250  cc. 
of  the  oil,  and  taking  two  hours  for  the  distillation  working  more  slowly  towards  the 
end.  The  flashing-point  is  determined  with  Abel's  apparatus.  Hitherto  the  limit  in 
Russia  has  been  28°  to  30°,  but  the  manufacturers  have  resolved  on  a  limit  of  25°. 

The  yield  of  the  various  products  of  the  distillation  differs  according  to  the  manner 
of  working.  The  more  benzene  and  heavy  oils  are  taken  along  with  the  true  burning 
oils — boiling  between  150°  and  290° — the  higher  is  the  yield  of  the  latter  and  the 
lower  its  quality.  From  numerous  reports  the  following  values  may  be  taken  : — 

Benzene  with  gasoline       .        .        .5-7  per  cent. 
Kerosene  I.  (burning  oil)    .         .         .     27-33        „ 
Kerosene  II.  (solar  oil)        .        .        .5-8        „ 
Residues 50-60        „ 

In  general,  3^  parts  crude  oil  are  used  to  obtain  i  part  of  kerosene.  The  quicker 
the  distillation  the  more  abundant,  but  the  poorer,  is  the  product.  At  Nobel's  refinery 
the  yield  of  kerosene  of  32°  flashing-point  is  27  per  cent.;  of  50°,  23  per  cent.  The 
specific  gravities  for  benzene  are  0754,  for  gasoline  0787,  for  kerosene  0-820-0-822. 

The  cost  of  production  for  i  hecto-kilo.  (=  100  kilos.)  burning  oil  (kerosene)  are — 

Shillings. 
3i  hecto-kilos.  crude  naphtha     .         .         .        .1-78 

Sulphuric  acid 0*15 

Caustic  soda o'li 

Wages 0-06 

Management 0-07 

Boiler  repairs O'i8 

Sinking  fund,  15  per  cent 0-24 

2-59 

Besides  the  kerosene  there  is  50  per  cent.  (17  hecto-kilos.)  of  residues,  and  26  per 
cent,  of  residues  are  used  in  heating  the  works. 

The  residues  are  especially  adapted  for  the  production  of  lubricating  oils.  These 
oils  are  valuable  from  their  viscosity,  their  resistance  to  cold,  and  their  non-liability  to- 
spontaneous  combustion. 


SECT,  i.]          THE   PARAFFINE    AND    SOLAR   OIL   INDUSTRY.  87 

Not  merely  kerosene,  but  the  lighter  products,  gasoline,  naphtha,  and  ligroine 
are  often  burnt  in  lamps  of  special  construction.  The  residues,  as  well  as  the 
crude  oil,  may  be  heated  in  retorts  for  the  production  of  gas.  Compressed  cymogen, 
boiling  at  o°,  is  used  in  the  production  of  artificial  ice  ;  Rhigolene  Rhyolan,  boiling  at 
1 8°,  serves  as  an  anaesthetic;  naphtha  (petroleum-ether,  or  canadol)  for  extracting 
fatty  oils ;  benzene  for  colours,  varnishes,  and  for  taking  out  spots,  and  the  heavier  oils 
(vulcanol,  vaseline,  and  valvoline)  serve  as  lubricants. 

THE  PARAFFINE  AND   SOLAR   OIL   INDUSTRY. 

Paraffine  was  first  discovered  in  1830  by  Reichenbach  in  beech- wood  tar,  and 
received  its  name  from  its  disinclination  to  combine  with  other  bodies.  It  was  sub- 
sequently obtained  by  the  dry  distillation  of  peat,  lignite,  Boghead  coal,  oil-shales,  &c. 
It  occurs  also  in  nature  ready  formed  in  mineral  oil,  which  may  contain  from  6  to  40 
per  cent. ;  in  ozokerite  (mineral  wax)  and  in  bitumen,  or  asphalte.  The  American 
mineral  oils  contain  little  paraffine,  but  those  of  India  (Rangoon  tar)  and  of  Java  con- 
tain large  proportions.  Warren  de  la  Rue  in  1854  obtained  a  patent  for  the  extraction 
of  paraffine  and  hydrocarbons  from  mineral  oils.  The  paraffine  obtained  as  a  residue  in 
refining  the  Pennsylvanian  mineral  oil  is  now  met  with  in  commerce  and  extensively 
used  under  the  name  vaseline.  It  is  employed  in  ointments,  pomades,  and  for  protect- 
ing metal  articles  from  oxidation.  Very  similar  preparations  are  sold  as  "  ozokerine  " 
and  "  Virginia." 

Paraffine  has  been  obtained  for  ten  years  from  ozokerite.  This  mineral  is  found  in 
Galicia,  on  the  northern  slope  of  the  Carpathians,  in  Roumania,  Bulgaria,  and  various 
places  in  Austria  and  Germany.  It  occurs  also  in  Texas,  Arizona,  and  Utah. 

Paraffine  is  obtained  in  Scotland  from  asphalt.  The  bitumen  of  Trinidad,  Cuba, 
Canada,  &c.,  forms  a  source  for  the  preparation  of  paraffine  and  liquid  fuels. 

The  manufacture  of  paraffine  by  the  dry  distillation  of  peat,  lignite,  oil-shales,  &c., 
resolves  itself  into  two  branches — the  preparation  of  tar,  and  the  extraction  from  it  of 
photogen,  solar  oil  and  paraffine.  The  former  process  is  difficult  and  important ;  it  is 
now  generally  performed  in  upright  retorts,  preferably  of  fire-clay. 

Preparation  of  the  Tar. — i.  This  operation  is  one  of  the  most  important  and  difficult 
parts  of  the  industry,  and  during  the  last  fifty  years  many  enterprises  undertaken  for 
the  application  of  fossil  fuel  to  the  preparation  of  illuminating  materials  have  failed 
solely  on  account  of  the  imperfect  preparation  of  the  tar.  The  making  of  the  tar  is 
carried  on  in  retorts  or  in  peculiarly  constructed  ovens,  the  distillation  being  in  many 
cases  assisted  by  the  application  of  superheated  steam.  The  principle  of  the  construc- 
tion of  the  tar-oven  is  very  simple,  being  that  of  a  portion  of  fuel  burning  in  the  lower 
part  of  the  oven,  a  layer,  more  or  less  thick,  of  superincumbent  fuel  is  submitted  to  a 
slow  carbonisation,  resulting  in  the  production  of  tar,  which  flows  downwards,  while 
the  gaseous  products  are  lost.  In  order  to  prevent  its  violent  combustion,  the  fuel  is 
covered  with  a  layer  of  clay.  But  as  experience  has  shown  that  this  mode  of  distilla- 
tion is  not  well  suited  for  the  production  of  tar  intended  to  yield  paraffine  and  the  oils, 
it  is  not  generally  in  practice  on  the  large  scale,  although  it  has  the  advantage  of  being  a 
continuous  and  uninterrupted  process.  According  to  report,  an  oven  constructed  by 
L.  Unger,  the  manager  of  a  paraffine  works  at  Dollnitz,  near  Halle,  yields  suitable  pro- 
ducts, while  a  saving  is  effected  in  labour  as  well  as  in  the  quantity  of  fuel  required  for 
the  distillation. 

Horizontal  retorts  are  frequently  used  for  the  preparation  of  tar,  but  experience 
has  taught  that  if  in  the  construction  of  the  furnaces  containing  the  retorts  tie 
arrangement  is  similar  to  that  of  a  gasworks  where  four  to  eight  retorts  are  worked 
in  one  furnace,  no  satisfactory  results  can  be  obtained,  one  of  the  reasons  being  that 


88  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

the  principles  of  gas-  and  of  tar-making  are  entirely  opposed.  It  appears  to  be  neces- 
sary to  construct  a  furnace  for  every  retort,  and  that  the  furnace  should  be  of  such 
dimensions  as  to  be  suited  to  hold  a  retort  10  feet  long,  30  inches  wide,  and  15  inches 
high,  forming  in  section  a  shallow  oval.  More  recently  there  have  been  built  in 
Bohemia  and  elsewhere  brickwork  retorts,  shaped  somewhat  like  a  baker's  oven.  These 
seem  to  answer  well,  but  are  difficult  to  repair,  although  of  small  first  cost.  Vohl 
observed  that  a  quantity  of  20  to  25  per  cent,  of  water  present  in  the  fossil  material 
very  greatly  assists  the  formation  and  increases  the  yield  of  tar,  owing  to  the  super- 
heated steam  formed  from  the  water  during  the  distillation  carrying  off  the  vapours  of  the 
tar  rapidly  from  the  hot  retort.  This  has  given  rise  to  the  construction  of  Lavender's 
tar-producing  apparatus,  the  principle  of  which  is  the  same  as  that  of  Violetti's 
wood-charring  apparatus  used  for  the  preparation  of  the  charcoal  in  gunpowder  manu- 
facture. Lavender's  apparatus  consists  of  an  iron  cylinder  provided  with  holes  at  the 
bottom  for  the  purpose  of  admitting  superheated  steam,  while  to  the  top  of  the  cylinder 
a  tube  is  fitted  for  carrying  off  the  products  of  the  distillation.  It  would  appear  that 
L.  Ramdohr's  method  of  preparing  tar  from  brown-coal  by  means  of  steam  yields  a  tar 
which  contains  22  to  24  per  cent,  of  paraffine,  and  36  to  38  per  cent,  of  oil. 

Condensation  of  the  Vapours  of  the  Tar. — The  condensation  of  the  products  of  the 
dry  distillation  is  one  of  the  most  important  operations,  and  greatly  influences  the 
yield  of  tar.  Vohl  has  lately  proved  that  even  when  the  construction  of  the  retorts  is 
not  of  the  best,  an  average  yield  of  tar  may  be  obtained  by  attention  to  the  condensa- 
tion of  the  vapours.  The  complete  condensation  of  the  vapours  of  the  tar  is  one  of  the 
most  difficult  problems  the  paraffine  and  mineral  oil  manufacturer  has  to  deal  with, 
while  the  means  usually  adopted  for  condensation,  such  as  large  condensing  surfaces, 
injection  of  cold  water,  and  the  like,  have  proved  ineffectual.  It  has  often  been 
attempted  to  condense  the  vapours  of  tar  in  the  same  manner  as  those  of  alcohol,  but 
there  exist  essential  differences  between  the  distillation  of  fluids  and  dry  distillation. 
In  the  former  case  the  vapours  soon  expel  all  the  air  completely  from  the  still  and  from 
the  condenser,  and  provided,  therefore,  that — in  reference  to  the  size  of  the  still  and 
bulk  of  the  boiling  liquid — the  latter  be  large  and  cool  enough,  every  particle  of  vapour 
must  come  into  contact  with  the  condensing  surfaces.  In  the  process  of  dry  distilla- 
tion the  case  is  entirely  different,  because  with  the  vapours,  say  of  tar,  permanent  gases 
are  always  generated.  On  coming  into  contact  with  the  condensing  surfaces,  a  portion 
of  the  vapours  is  liquefied,  leaving  a  layer  of  gas  as  a  coating,  as  it  were,  on  the  con- 
densing surface.  The  gas  being  a  bad  conductor  of  heat,  prevents  to  such  an  extent 
the  further  action  of  the  condensing  apparatus,  that  a  large  proportion  of  the  vapours 
is  carried  on  and  may  be  altogether  lost.  A  sufficient  condensation  of  the  vapours  of 
tar  can  be  obtained  only  by  bringing  all  the  particles  of  matter  which  are  carried  off 
from  the  retorts  into  contact  with  the  condensing  surface,  which  need  neither  be  very 
large  nor  exceedingly  cold,  because  the  latent  heat  of  the  vapours  of  tar  is  small,  and 
consequently  a  moderately  low  temperature  will  be  sufficient  to  condense  these  vapours 
to  the  liquid  state.  The  mixture  of  gases  and  vapours  may  be  compared  to  an  emul- 
sion, such  as  milk,  and  as  the  particles  of  butter  may  be  separated  from  milk  by  churn- 
ing, so  the  separation  of  the  vapours  of  tar  from  the  gases  can  be  greatly  assisted  by 
the  use  of  exhausters  acting  in  the  manner  of  blowing  fans.  It  is  of  the  utmost  im- 
portance in  condensing  the  vapours  of  tar  that  the  molecules  of  the  vapours  be  kept  in 
continuous  motion,  and  thus  made  to  touch  the  sides  of  the  condenser.  The  condenser 
should  not  be  constructed  so  that  the  vapours  and  gases  can  flow  uninterruptedly  in 
one  and  the  same  direction.  The  temperature  at  which  the  distillation  is  conducted 
greatly  influences  the  yield  of  tar,  and  consequently  of  the  paraffine  and  oil.  As 
regards  the  influence  of  the  shape  of  the  retorts  and  mode  of  distillation,  H.  Vohl  made 
the  undermentioned  comparative  researches  by  distilling  French  and  Scotch  peat  in 


SECT,  i.]         THE   PARAFFINE   AND   SOLAK  OIL   INDUSTRY. 


89 


horizontal  retorts  (No.  I.),  in  vertical  retorts  (No.  II.),  and  in  ovens  somewhat  like 
coke-ovens  (No.  III.). 

100  parts  of  peat  yield  of  tar, — 

i.  n.  in. 

French  peat          .        .        .     5-59  ...        4-67        ...  2-69 

Scotch  peat ....    9-08  ...        6-39        ...  4-16 

The  sp.  gr.  of  the  tar  from  the  different  kinds  of  apparatus  was  as  follows : — 

i.  IT.  in. 

French  peat    .        .        .    0-920        ...        0-970        ...         roo6 
Scotch  peat    .        .        .    0-935        •••        0-970        ...         1-037 

It  appeal's  from  these  results  that  horizontal  retorts  yield  the  largest,  and  ovens 
the  smallest,  quantity  of  tar  ;  moreover,  the  duration  of  the  operation  of  distilling  is 
shortest  in  horizontal  retorts,  which  also  yield  less  gas,  while  in  the  ovens  both  tar  and 
coke  are  burnt  away  to  a  considerable  extent  by  the  too  great  supply  of  oxygen. 

Properties  of  Tar. — The  tar  obtained  from  the  retorts  in  distilling  peat,  brown-coal, 
lignite,  bituminous  shales,  Boghead  coal,  &c.,  at  as  low  a  temperature  as  possible,  and 
hardly  higher  than  dull  red-heat  even  towards  the  end  of  the  operation,  exhibits  a 
coffee-brown  colour,  generally  an  alkaline,  but  in  some  instances  an  acid,  reaction,  and 
possesses  the  very  penetrating  odour  characteristic  of  tar.  By  exposure  to  air  the 
colour  of  the  tar  becomes  deeper,  and  sometimes  even  brownish-black.  This  tar  often 
semi-solidifies  at  a  temperature  of  9°  to  6°,  owing  to  the  paraffine  it  contains.  The 
sp.  gr.  varies  from  0*85  to  0*93,  and  consequently  the  tar  floats  on  water.  The  so- 
called  steam-tar,  obtainedby  the  aid  of  superheated  steam  from  brown-coal  (according 
to  Ramdohr's  plan,  1869)  always  has  an  acid  reaction,  and  is  completely  saponified  by 
alkalies ;  this  tar  becomes  solid  at  a  temperature  of  55°  to  60°,  and  can  therefore  be 
preserved  in  solid  blocks  in  summer  time.  Its  sp.  gr.  is  0*875. 

As  regards  the  quantity  of  tar  obtained  from  100  parts  of  raw  material,  the  follow- 
ing results  are  most  general : — 


Sn     Pi- 

Crude 

Paraffine. 



per  cent. 

Foliated  bituminous  shale,  Siebengebirge         .        .        .        .; 
,,                „               „       Hesse      
Brown-coal,                            Prussian  Saxony    . 
»                  .... 

_>»                  .... 

2O'OO 

25-00 
7-00 

lO'OO 

6-00 
5-00 

II'OO 

0-880 
0-880 
O^IO 
O-92O 
0-9I5 
0'9IO 
0-860 

0-750 
i-ooo 
0-500 

0750 
0-500 
0-250 

Westerwald    .        .        .        .     .'.- 
Nassau    

5-50 
3-50 

4-00 
3'OO 

O^IO 
O^IO 
O-9IO 
O^IO 

Frankfort        
Lignite,                                   Silesia     

9-00 
3-00 
14-00 

0-890 
O-89O 
0^70 

0-250 

I'OOO 

„                                           Westphalia     .        .        .        •        .; 
Schist,                                     Wiirtemburg  

Peat,                                        Neumark        .        .        .        .      •  v 

5-00 

9-63 
5-00 
9  -co 

O-92O 

0*975 
O^IO 
O-92O 

0-050 
0-124 
0-330 

O'«O 

„                                           Erzgebirge      .                 ... 
»                                                   »••••• 

570 
5-30 
V86 

O-902 
0^5 

0-350 

0-400 

7  -oo 

3VOO 

0-860 

i—  i  '4 

Cannel  coal,                                   „               .... 

i-i-3 

I'OOO 

Coarse  coal,                                   ,,               ..... 

9-00 

O-9IO 

I-I  -25 

Mode  of  Operating  with  the  Tar. — The  first  thing  to  be  done  with  the  crude  tar 
us  to  separate  the  water,  which  is  effected  by  pumping  the  tar  into  the  dehydrating 


9o  CHEMICAL  TECHNOLOGY.  [SECT.  i. 

apparatus.  These  apparatus  consist  of  tanks  of  boiler-plate,  placed  within  a  larger  tank, 
so  that  a  space  of  10  centimetres  intervenes,  into  which  water  is  poured  and  maintained 
by  means  of  steam  at  a  temperature  of  60°  to  80°  for  ten  hours.  After  this  time  the 
ammoniacal  water  and  other  impurities,  together  about  one-third  of  the  bulk  of  the 
crude  tar,  have  become  separated,  while  the  small  quantity  of  water  still  adhering  to 
the  tar  is  of  no  consequence  in  the  further  operations.  The  tar  is  decanted  by  opening 
a  stop-cock  or  valve  placed  near  the  top  of  the  tank,  and  the  ammoniacal  water  is 
removed  by  opening  a  stop-cock  at  the  bottom. 

Specifically  light  tars  are  of  course  readily  separated  from  the  water,  while  heavy 
tars  are  more  difficult  to  deal  with.  If  to  the  ammoniacal  water  of  such  tars  salts  are 
added — for  instance,  common  salt,  Glauber  salt,  chloride  of  calcium,  and  the  like — the 
specific  gravity  of  the  water  is  increased,  and  the  heavy  tar  more  readily  separated  ; 
but,  according  to  Dullo,  these  means  are  either  too  expensive  or  do  not  quite  answer  the 
purpose.  The  complete  separation  of  the  tar  from  the  water  is  of  the  greatest  import- 
ance, because  in  the  subsequent  distillation  the  presence  of  water  may  cause  the  tar  to 
boil  over  and  give  rise  to  serious  accidents  by  coming  in  contact  with  the  fire  under 
the  stills. 

Distillation  of  the  Tar. — This  operation  is  usually  carried  on  in  cast-iron  stills  large 
enough  to  hold  20  cwt.  of  tar.  In  order  to  prevent  the  flame  impinging  on  the  bottom 
of  the  still,  it  is  protected  by  a  fire-brick  arch.  The  still  is  usually  built  in  two  separate 
parts,  which  are  joined  with  a  flange  and  bolts,  so  that  if  the  lower  part  is  burnt  out, 
only  that  requires  to  be  renewed. 

The  capitals  of  these  stills  are  rather  flat  and  the  spout  very  wide.  The  vapours  of 
the  various  oils  have  a  high  density  and  low  latent  heat,  so  that  these  vapours  have  a 
tendency  to  condense  readily  and  flow  back  into  the  still ;  therefore  the  capital  is  covered 
with  sand  or  ash,  being  bad  conductors  of  heat.  When  the  tar  is  thoroughly  dehydrated, 
the  distillation  proceeds  quietly  and  without  ebullition ;  but  if  any  water  be  mixed  with 
or  adheres  to  the  tar,  the  liquid  in  the  still  boils  violently  and  is  very  apt  to  boil  over. 
At  below  1 00°  the  tar  loses  the  very  volatile  sulphide  of  ammonium  and  the  pyrrhol 
bases,  while  gases  are  evolved  which  ought  to  be  allowed  to  escape  by  a  safety-valve. 
The  true  distillation  begins  at  1 00°,  yielding  at  first  a  distillate  consisting  of  very  strong 
ammoniacal  liquor  and  some  light  oils.  The  boiling-point  of  the  tar  is  not  constant, 
the  oil  coming  over  uninterruptedly  when  the  temperature  has  risen  to  above  200°  ; 
then  the  boiling-point  becomes  somewhat  constant,  while  with  the  oil  some  water  comes 
over,  due  to  the  chemically  combined  water  of  the  carbolic  acid  being  set  free.  The 
distillation  then  again  becomes  somewhat  interrupted,  and  can  be  maintained  only  by 
stronger  firing  of  the  retort.  The  oils  now  distilling  over  become  solid  on  cooling, 
owing  to  the  large  proportion  of  paraffine  they  contain.  The  distillation  is  continued 
to  dryness,  the  asphalt  left  in  the  still  being  removed  after  about  four  or  five  opera- 
tions, and  for  this  purpose  the  still  is  somewhat  cooled,  and  the  molten  asphalt  run  off 
by  a  tap  at  the  bottom  of  the  still.  If  the  distillation  is  carried  to  dryness,  some  water 
finally  distils  over,  due  to  the  decomposition  of  the  organic  matter.  A  still  of  500  litres 
capacity  can  be  distilled  off  in  twelve  to  fourteen  hours,  if  the  operation  is  pushed  so  far 
as  to  decompose  the  asphalt,  leaving  only  a  carbonaceous  residue  ;  but  if  the  asphalt  is 
to  be  collected,  the  distillation  must  be  stopped  after  eight  to  ten  hours.  The  still  is 
separated  from  the  condensing  apparatus  by  a  massive  wall,  through  which  the  spout 
of  the  capital  is  passed  into  the  leaden  worm,  serving  as  a  condenser,  and  kept  cool  by 
being  placed  in  a  wooden  tank  filled  with  cold  water.  But  as  soon  as  the  paraffine 
magma  begins  to  come  over  the  water  is  allowed  to  become  warm,  in  order  to  prevent 
the  paraffine  solidifying  in  the  worm.  The  gases  which  are  evolved  towards  the  end  of 
the  distillation  are  carried  off  by  a  pipe  communicating  with  the  chimney. 

Treatment  of  the   Products   of  Distillation. — The   mixed   products  of   raw  oils 


SECT,  i.]         THE   PARAFFINS  AND  SOLAR  OIL   INDUSTRY.  91 

obtained  by  the  distillation  are  poured  into  a  large  cast-iron  cylinder  and  mixed  with  a 
solution  of  caustic  soda  so  as  to  cause  the  latter  to  act  upon,  and  intimately  combine 
with,  the  acid  substances  (homologues  of  carbolic  acid) — simply  termed  creosote  in  the 
works — and  pyroligneous  acid,  which  impart  an  offensive  odour  and  dark  colour  to  the 
oils.  When  the  mixture  of  the  oils  and  caustic  soda  solution  has  been  effected,  the 
fluid  is  run  into  an  iron  tank  and  allowed  to  settle ;  the  creosote-soda  is  then  removed, 
and  the  oil  washed  with  water  to  eliminate  any  adhering  alkali.  The  crude  oil  is  next 
similarly  treated  with  sulphuric  acid  for  the  purpose  of  removing  basic  substances, 
which  impart  odour  and  colour.  The  quantity  of  acid  to  be  used  and  the  duration  of 
its  action,  aided  sometimes  by  heat,  depend  upon  the  nature  of  the  crude  oil — 5  per 
cent,  of  acid  of  i"jo  sp.  gr.  and  five  minutes'  action  are  sometimes  sufficient,  while  in 
other  cases  25  per  cent,  of  acid  will  be  required,  and  three  hours'  contact  with  the  oil. 
The  action  of  the  sulphuric  acid  should  be  carefully  watched,  as  it  may  injure  the 
quality  of  the  oil  by  decomposing  some  of  the  lighter  hydrocarbons,  whereby  sulphur- 
ous acid  is  given  off.  The  mixture  of  acid  and  oil  is  allowed  to  settle  ;  the  former  is 
run  off,  and  the  latter  washed  first  with  water,  then  with  very  dilute  soda-lye,  and  is 
finally  poured  into  the  rectifying  stills.  The  solution  of  creosote-soda  is  neutralised 
with  the  sulphuric  acid  from  the  preceding  operation,  the  result  being  that  crude 
carbolic  acid  is  obtained,  which  is  used  for  various  purposes ;  such  as  impregnating 
wooden  railway  sleepers,  as  a  disinfecting  material,  or  for  preparing  certain  tar-colours. 
More  recently  the  creosote-soda  has  been  used  for  gas  manufacture,  leaving  a  coke  con- 
taining soda,  the  soda  being  abstracted  by  lixiviation  with  water. 

Rectification  of  the  Crude  Oils. — This  operation  is  conducted  precisely  as  the  distil- 
lation of  the  tar.  The  oils  are  separated  according  to  their  greater  or  less  volatility 
and  specific  gravity,  or  are  kept  mixed,  as  parafline  oil,  at  a  sp.  gr.  of  0-833,  and  sent 
as  such  to  the  market.  When  the  oil  which  comes  over  begins  to  solidify  on  cooling  or 
exhibits  a  sp.  gr.  of  o-88  to  0*9,  it  is  separately  collected  and  placed  in  a  cool  situation 
for  the  purpose  of  crystallising  the  paraffme.  The  vessels  in  which  the  parafline  magma 
is  placed  for  the  purpose  of  solidifying  are  rectangular  iron  tanks,  fitted  with  a  tap,  or 
are  conical,  sugar-loaf-shaped  vessels,  made  of  iron  or  wood,  and  from  1*6  to  2  metres 
high,  and  i  metre  wide  at  the  top,  being  provided  with  a  tap  for  the  purpose  of  remov- 
ing the  oily  matter  which  has  not  solidified  after  the  lapse  of  about  two  to  four  weeks. 
This  thick  oil  is  next  cooled  to  far  below  the  freezing-point  of  water,  in  order  to  obtain 
more  parafline  and  other  hydrocarbons  mixed  with  it.  Any  still  non -solidified  matter  is, 
when  it  has  a  low  specific  gravity,  again  refined  by  distillation,  and  will  yield  parafline 
oil ;  but  if  its  sp.  gr.  is  high — say  from  0^925  to  0*940 — it  is  used  as  a  lubricating  oil, 
known  abroad  as  Belgian  waggon  grease. 

Refining  the  Crude  Parafline. —  The  crude  parafline  is  in  England  sold  to  the 
refiners,  who  are  also  paraffine-candle  makers ;  but  on  the  Continent  every  manufacturer 
of  crude  parafline  refines  his  products  and  converts  it  into  candles.  The  crude  parafline, 
so-called  parafline  butter,  is  treated  in  various  ways  :  some  manufacturers  crystallise  it 
by  the  aid  of  cold,  and  press  it  for  the  purpose  of  removing  any  oil ;  others,  again,  first 
treat  the  crude  material  with  caustic  alkali-lye,  next  with  sulphuric  acid,  and  then  again 
distil  it  or  leave  it  to  crystallise.  The  caustic  soda-lye  removes  from  the  parafline  all  the 
acid  substances  and  other  impurities  it  may  contain.  The  partly  purified  parafline  is 
now  treated  with  6  to  10  per  cent,  of  sulphuric  acid,  whereby  alkaline  and  resinous 
matters  are  removed.  The  loss  in  bulk  of  the  crude  material  by  these  operations 
amounts  to  about  5  per  cent.  The  purified  parafline  is  next  allowed  to  remain  in  a 
very  cool  place  for  some  three  or  four  weeks,  after  which  the  nearly  solid  mass  is 
filtered,  then  submitted  to  the  action  of  centrifugal  machines,  and  finally  strongly 
pressed.  The  oil  which  is  separated  from  the  parafline  is  again  distilled,  yielding  paraf- 
fine  oil  and  parafline  butter.  The  solid  parafline  is  molten,  cast  into  blocks,  and  these 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


submitted  to  very  powerful  hydraulic  pressure.  The  pressed  cake  is  next  treated  at 
1 80°  with  10  per  cent,  of  sulphuric  acid  for  two  hours,  then  washed  with  hot  water, 
again  cast  into  blocks,  again  pressed,  and  then  washed  with  a  solution  of  caustic  soda. 
Instead  of  treating  the  paraffine  with  active  agents,  it  has  been  proposed  to  use  neutral 
solvents  for  the  removal  of  the  oily  materials  ;  for  this  purpose,  benzol,  light  tar  oils, 
benzolene,  and  sulphide  of  carbon,  have  been  employed  in  the  following  manner  : — The 
crude  paraffine  is  first  hot-pressed,  and  the  pressed  mass  fused  with  5  to  6  per  cent,  of 
the  solvent ;  having  been  again  cast  into  blocks,  these  are  pressed,  and  the  operation 
repeated  if  necessary.  The  paraffine  having  thus  been  made  quite  white  and  pure,  is 
again  fused  and  treated  with  high-pressure  steam,  forced  into  the  molten  mass  for  the 
purpose  of  volatilising  the  last  traces  of  the  solvents.  The  sulphide  of  carbon,  first  em- 
ployed by  Alcan  (1858)  for  refining  paraffine,  is  used  in  the  following  manner: — The 
paraffine  is  melted  at  the  lowest  possible  temperature,  then  well  mixed  with  10  to  15 
per  cent,  of  sulphide  of  carbon,  after  which  the  cooled  and  solidified  mass  is  strongly 
pressed,  the  expressed  fluid  being  submitted  to  distillation  for  the  purpose  of  recovering 
the  sulphide  of  carbon.  The  paraffine  is  next  fused  and  kept  in  liquid  state  for  some 
time  for  the  purpose  of  eliminating  the  adhering  sulphide  of  carbon. 

Hubner's  Method  of  Preparing  Paraffine. — Instead  of  following  the  preceding 
method  with  the  crude  tar,  Hubner  treats  it  first  with  sulphuric  acid,  and  next  distils 
the  tar,  separated  from  the  acid,  over  quicklime.  The  crude  paraffine  obtained  is 
pressed,  and  then  further  refined  by  treating  it  with  colourless  brown-coal  tar  oil.  The 
advantages  of  this  method — by  which  one  distillation  is  saved — are  : 

a.  A  larger  yield  of  paraffine. 

jQ.  A  material  of  better  quality  and  greater  hardness  than  by  the  usual  method. 

With  the  paraffine  the  so-called  paraffine  oils  are  obtained  ;  but  this  industry  has 
been  greatly  crippled  by  the  extensive  importation  of  paraffine  oils  (really  petroleum 
oils)  from  America,  so  that  the  aim  of  the  paraffine  makers  is  to  increase  the  yield  of 
paraffine.  By  Hubner's  method  of  distillation  over  quicklime,  40  to  50  per  cent,  of 
impurities  (chiefly  empyreumatic  resins  and  creosote)  are  removed,  which  by  the  old 
process  are  only  got  rid  of  at  greater  expense  by  the  use  of  caustic  soda. 

Yield  of  Paraffine. — As  regards  the  yield  of  paraffine,  paraffine  oil,  and  lubricating 
oil,  from  the  various  kinds  of  raw  materials,  we  quote  the  following  particulars.  At 
the  Bernuthsfeld  works,  near  Aurich,  the  excellent  peat  yields  6  to  8  per  cent,  of  tar ; 
20  per  cent,  of  paraffine  oil,  of  sp.  gr.  =  0-830  ;  and  0*75  per  cent,  of  paraffine. 
H.  Vohl  obtained  from  100  parts  of  peat-tar  from  the  peat  of  undermentioned 
localities  : — 


1  — 

1                     .  r  • 

Paraffine  Oil. 

Lubricating1  Oil. 

i 

Sp.  gr.  o'82o. 

Sp.  gr.  o'86o. 

\ 
Celle  (Hannover)  
Coburg  

34'6o 
20-62 

IQ-41? 

36-00 
26-57 
19-54 

8-01 
3-12 
3-31 

;  Zurich  (Switzerland)     

I4"4O 

8-66 

0-42 

Russia  .                  ....... 

2O*^Q 

20  -30 

3'36 

Westphalia    .                

II'OO 

19-48 

2-25 

Brown-Coal. — In  the  works  situated  in  the  Weissenfels  brown-coal  mineral  district, 
275  to  300  Ibs.  of  the  mineral  yields  35  to  50  Ibs.  of  tar.  100  Ibs.  of  this  tar 
yield  8  to  10  Ibs.  of  hard  paraffine  suited  for  candle-making,  and  further  8  to  10  Ib.  of 
soft  paraffine  for  use  in  stearine-candle  making,  as  well  as  43  Ibs.  of  paraffine  oil. 
Hubner's  works  at  Rehmsdorf,  near  Zeitz,  yield  annually  from  360,000  cwts.  of  brown- 
coal,  about  40,000  cwts.  of  tar,  yielding  18,000  cwts.  of  crude  oil,  4000  cwts.  of  refined 
paraffine  oil,  and  6000  cwts.  of  paraffine. 


SECT,  i.]          THE   PARAFFINE   AND   SOLAR   OIL   INDUSTRY.  93 

i  oo  parts  of  retort-tar  (in  contradistinction  to  steam-tar)  from  brown-coal  yield  : — 


Brown  Coal  from  — 

Paraffine  Oil. 
Sp.  gr.  o'82o. 

Lubricating  Oil. 
Sp.  gr.  o-86o. 

Paraffine. 

Analysed  by 

33-50 

4O'OO 

3  '3 

\ 

33'4I 

40-06 

67 

17-50 

26-2I 

5-0 

Oldisleben           „           

1772 

26-60 

4'4 

16*42 

27-14 

4'2 

Wohl. 

Der  Rhon,  Bavaria 

IO-62 

I9-37 

I  '2 

Tilleda,  Prussia      ... 

I6'66 

18-05 

4'4 

Stockheim,  near  Diiren,  Prussia 

I7-SO 

26-63 

3'2 

Bensberg,  near  Cologne      „ 

16-36 

I9-S3 

3-4 

/ 

Tscheitch,  Austro-  Hungary  . 

9-04 

28-86 

3-2 

Eger 

9-14 

54-00 

5'2 

•  C   Miiller 

Herwitz                   „ 

22-OO 

48-32 

5  '2 

Schobritz                „                 ..  •.  • 

21-68 

46-33 

4'3 

Ramdohr  obtained  (1869)  from  steam-tar  from  brown-coal  on  an  average  — 

'5  Per  cent-  fusing  afc 
9 
36  to  38  per  cent,  of  oil. 


22  to  24  per  cent,  paraffine   , 
\  7 


to  58;jand 
"°  47  ) 


With  careful  management  steam-tar  may  yield  from  28  to  30  per  cent,  paraffine. 
The  quotations  of  the  yield  from  cannel  and  Boghead  coals  vary  very  much.     100 
parts  of  tar  from  bituminous  shale  were  found  to  yield  :  — 


Mineral  Oil. 

Lubricating  Oil- 

Paraffine. 

English  bituminous  shale       
Bituminous  shale  from  Romerickberg,  Prussia 
„              „               Westphalia              „ 
„             „     Oedingen  on  the  Rhine   „           . 

24-28 
25-68 
27-50 
18-33 

40*00 
43-00 
13-67 
38-33 

O'I2 
O'll 
I'll 
5.00 

According  to  Miiller  (1867),  100  parts  of  Galician  mineral  wax  (ozokerite)  yield 
24  per  cent,  of  paraffine  and  40  per  cent,  of  oil. 

Paraffine  when  purified  is  a  white,  waxy,  tasteless,  and  inodorous  mass,  slightly 
greasy  to  the  touch,  harder  than  tallow,  but  softer  than  wax.  Its  sp.  gr.  varies  from 
0-869  to  0-943,  and  its  specific  heat  =  0-683.  If  heated  for  days  with  access  of  air  it 
takes  up  oxygen  and  turns  brownish.  Its  properties  vary  according  to  its  origin. 
Paraffine  from  the  Boghead  coal  melts  at  45°,  and  is  either  crystalline  or  granular  ;  but 
it  has  been  known  to  melt  at  80°.  Paraffine  from  Rangoon  tar  melts  at  61°,  that  from 
peat  at  47°,  that  from  ozokerite  at  56°  to  82°.  Paraffine  seems  to  be  a  mixture  of 
hydrocarbons  homologous  with  methan  (of  the  formula  C«H2«  +  2),  and  especially  of 
members  of  this  series  containing  more  than  16  atoms  of  C.  The  softer  paraffines  have 
the  formulae  C18H40,  and  C20H42 ;  whilst  the  harder  varieties  are  C21H44  and  C22H46. 
Grotowsky  found  in  paraffine  from  Saxon  lignite  3-4  per  cent,  of  oxygen,  and  gave  it 
the  formula  C32H33O. 

Paraffine  is  insoluble  in  water,  but  soluble  in  alcohol,  ether,  oil  of  turpentine,  olive 
oil,  benzol,  chloroform,  and  carbon  disulphide.  Acids  and  alkalies  do  not  attack  paraffine 
at  common  temperatures ;  neither  does  chlorine,  but  if  it  is  allowed  to  act  for  some 
time  upon  melted  paraffine,  hydrochloric  acid  is  evolved,  and  chlorised  products  are 
formed.  If  heated  with  bromine  it  forms  hydrobromic  acid  in  abundance,  and  with 
sulphur  sulphuretted  hydrogen.* 

Paraffine  can  be  melted  along  with  wax,  stearine,  and  palniitine  in  any  proportion. 

The  main  application  of  paraffine  is,  of  course,  in  the  manufacture  of  candles.  Its 
minor  uses  are  for  saturating  matches,  greasing  leather,  preparing  wax-papers,  polish- 
ing glazed-paper,  &c. 

*  The  latter  reaction  has  been  proposed  as  a  means  of  obtaining  sulphuretted  hydrogen,  abso- 
lutely free  from  arsenic,  for  use — e.g.,  in  toxicological  cases. 


94  CHEMICAL   TECHNOLOGY.  [SECT.  i. 

Along  with  paraffine,  Eeichenbach  discovered  in  tar  eupion  a  very  light  mobile  fluid, 
which  burns  with  aluminous  flame.  Its  boiling-point  varied  from  47°  to  169°  so  that 
it  was  doubtless  a  mixture. 

Solar  Oil. — Tar-oil  can  be  resolved  by  further  rectification  into  paraffine  and  into 
oily  liquids,  which,  after  the  acid  and  the  heavy  constituents  are  removed,  occur  in 
commerce  as  a  mixture  under  the  names  photogene,  mineral  oil,  solar  oil,  paraffine 
oil  (which  in  England  denotes  the  lamp  oil  obtained  from  the  Boghead  mineral). 
These  oils  are  very  similar  to  petroleum  oils  and  consist  only  of  carbon  and  hydrogen. 
When  thoroughly  purified  they  are  colourless  and  have  only  a  slight  smell. 

The  mineral  oils  are  thus  distinguished — photogene  is  a  mixture  of  liquid  hydro- 
carbons of  the  ethase  series  (C^H^  +  2)  especially  of  Leptase,  C7H16  and  benzyl-hydride, 
C15H33.  It  is  a  clear,  very  mobile  liquid  of  sp.  gr.  0*80  to  o-8i ;  the  earlier  light 
photogenesof  078  sp.  gr.  contain  chiefly  essences  of  sp.  gr.  0720,  boiling  below  60°. 
They  have  hence  been  long  ago  proscribed  as  dangerous.  The  low-boiling  oils  from 
lignite  tar  and  mineral  oil  are  sold  by  the  names  benzene  (benzolene,  naphtha,  ligroine) 
and  are  used  for  taking  out  fat  and  oil  stains,  for  removing  the  grease  of  wool,  as  a 
substitute  for  oil  of  turpentine,  for  enriching  gas,  &c.  The  solar  oil,  which  is  being 
substituted  as  an  illuminant  for  the  photogenes  and  the  fatty  oils  of  the  past,  is  a 
clear  oil,  colourless  and  slightly  yellowish,  of  sp.  gr.  0-825  *°  °'83O.  The  boiling-point 
is  on  the  mean  178°.  At  10°  no  solid  paraffine  should  separate  out.  Its  flashing 
point  is  above  100°.  On  fractionation  no  products  having  a  flashing  point  below  70° 
should  separate  out. 

Along  with  solar  oil  follows  the  pyrogene  of  Breitenlohner,  obtained  from  the 
residuary  crude  oils,  having  a  sp.  gr.  of  0-895  to  0-945,  which  accumulate  in  the  tar- 
works.  Pyrogene  is  a  light  wine-yellow  oil  of  sp.  gr.  0-825  to  0-845. 

Lubricating  oil,  known  also  as  "vulcanol,"  is  a  thick  oil  of  sp.  gr.  0*845  *° 
o'86o,  and  at  low  temperatures  deposits  abundance  of  fine  crystals  of  paraffine.  It  is 
formed  in  great  quantities  in  the  petroleum  refineries  and  in  the  paraffine  and  solar 
oil  works.  The  vulcanol  imported  from  America  is  not  a  distilled  product,  but  a  heavy 
mineral  oil  decolorised  by  means  of  bone-black.  Sometimes  it  is  mixed  with  a  few 
per  cents,  of  animal  or  vegetable  fats. 

The  manufacture  of  mineral  oil  is  developed  simultaneously  with  that  of  paraffine. 
Solar  oil  gives,  in  suitable  lamps,  a  light  equal  in  intensity  to  that  of  kerosene.  It 
has,  however,  an  unpleasant  smell  and  is  apt  to  smoke.* 

PRODUCTION   OF   LIGHT. 

If  solids  are  heated  they  become  feebly  luminous  in  the  dark  about  400°  ;  at  600° 
they  are  red-hot,  at  90o°-iooo°  white  hot,  whilst  gases  even  at  i5oo°-2ooo°  do  not 
become  luminous.  The  luminosity  of  flame  is  therefore  not  the  ignition  of  the  products 
of  combustion.  If  the  gases  arriving  at  combustion  are  more  quickly  mixed,  the  flame 
becomes  shorter,  since  the  process  is  effected  more  rapidly,  and  at  the  same  time 
hotter,  since  less  cold  air  is  mixed  with  the  products  of  combustion.  In  the  same 
manner,  the  flame  becomes  shorter  and  hotter  if  the  gases  are  heated  prior  to 
combustion.  As  the  ascending  products  of  combustion  retain  for  a  short  time  nearly 
the  temperature  of  the  flame,  the  reverse  behaviour  would  occur  if  the  gases  were 
self-luminous.  The  light  of  the  flame  ceases  at  a  sharply  marked  upper  boundary, 
and  evidently  coincides  with  the  completion  of  the  chemical  action.  This  action 
consequently,  and  not  the  ignition  of  the  products  of  burning,  must  be  the  cause 
of  the  light. 

*  It  must  seem  strange  that  the  author  should  have  made  no  mention  of  the  merits  of  the  late 
James  Young  in  connection  with  the  paraffine  industry.  The  only  mention  of  his  name  is  in  n 
note  giving  the  statistics  of  Young's  Mineral  Oil  Company.— [EDITOR.] 


SECT.    I.] 


PHOTOMETEY. 


95 


In  the  flame  of  a  candle  we  may  distinguish  four  layers.  The  dark  nucleus  is 
formed  by  the  gasification  of  the  fuel  (tallow,  paraffine,  &c.)  rising  up  in  the  wick, 
which  may  be  kindled  at  the  orifice  of  a  fine  glass  tube  cautiously  inserted  into  the 
flame.  The  rush  of  air  is  directed  towards  the  axis  of  the  flame,  whence  the  blue  portion 
has  a  lower  temperature.  In  the  luminous  layer  the  oxygen  of  the  air  is  only  in  part 
sufficient  for  combustion,  whilst  in  the  non-luminous  veil  externally  the  products  of 
the  imperfect  oxidation  burn  in  an  excess  of  air. 

In  opposition  to  the  well-known  theory  of  Davy  that  the  luminosity  of  a  flame  is 
due  to  particles  of  carbon  ignited  to  whiteness  by  the  combustion  of  the  hydrogen, 
Frankland  and  Tyndall  maintain  that  the  luminosity  is  due,  not  to  the  separation  of 
solid  carbon,  but  to  the  presence  of  dense  vapours  of  the  higher  hydrocarbons. 


PHOTOMETRY. 

Attempts  at  measuring  the  luminosity  of  a  flame  were  made  as  early  as  1700. 
Lambert  (1760)  utilised  the  circumstance  that  an  object  illuminated  by  two  flames 
throws  two  shadows  of  unequal  depth  if  the  action  of  both  flames  upon  the  screen 
receiving  the  shadows  is  unequal.  Let  C  D  (Fig.  104)  be  a  white  screen,  before  which 

Fig.  104. 


stands  at  some  distance  a  thin  round  rod,  blackened  with  soot,  s,  and  let  1  be  the  one 
and  L  the  other  source  of  light.  The  two  lights  are  placed  so  that  the  two  shadows  of 
the  rod,  a  and  b,  do  not  coincide,  but  fall  upon  the  screen,  C  D,  at  no  great  distance 
from  each  other.  The  stronger  light  is  then  pushed  so  far  from  the  screen,  C  D,  that 
the  shadows  are  equally  dark — i.e.,  the  shadow,  b,  is  as  strongly  illuminated  by  the 
light,  L,  as  is  the  shadow,  a,  by  the  light,  1.  The  process  is  not  adapted  for  accurate 
measurements,  but  it  is  simple  and  easy,  and  may  even  now  serve  for  the  purposes 
of  daily  life. 

Bunsen's  photometer  is  chiefly  used  for  measuring  different  sources  of  light.  It 
consists  of  a  paper  screen  stretched  in  a  frame,  and  in  the  middle  is  a  spot  made  trans- 
lucent with  wax  or  stearine.  It  appears  light  on  a  dark  ground  if  the  screen  is 
illuminated  more  strongly  at  the  back  than  at  the  front,  and  in  the  reverse  case  dark 
on  a  light  ground.  The  normal  flame  is  placed  on  one  side  of  the  screen,  and  on  the 
other  the  flame  to  be  measured,  and  this  is  displaced  until  the  spot  nearly  disappears. 
If,  e.g.,  the  distance  of  the  normal  flame  from  the  screen  is  2  decimetres,  and  that  of 
the  flame  to  be  measured  8  decimetres,  the  latter  =  82  :  22—  16  candles. 

During  such  measurements  all  other  sources  of  light  must  be  carefully  excluded. 

As  unit,  the  flame  of  a  candle  is  generally  used.  In  Germany  the  photometric 
candle  has  a  diameter  of  20  mm. ;  it  must  be  accurately  cylindrical,  and  so  long  that 
twelve  candles  weigh  i  kilo.  The  wicks  must  be  twisted  as  uniformly  as  possible,  of 


96 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


twenty-four  threads  of  cotton,  and,  when  dry,  must  weigh  668  m. grammes  per  metre 
run.  They  are  distinguished  from  other  wicks  by  the  introduction  of  a  red  thread.  The 
material  must  be  paraffine,  as  pure  as  possible,  congealing  not  under  55°.  The  flame 
must  be  50  mm.  in  height. 

In  Munich  there  is  used  as  the  unit  a  stearine  candle  made  from  a  stearine  con- 
taining 76  to  76^6  per  cent,  of  carbon.  It  consumes  hourly,  according  to  Schilling,  on  an 
average  io'4  grammes  stearine,  and  has  a  flame  of  52  mm.  in  height.  The  English  sper- 
maceti candle  has  a  wick  platted  of  three  strands,, 
each  containing  seventeen  threads ;  it  consumes 
hourly  120  grains  (7'78  grammes)  spermaceti,  the 
height  of  the  flame  being  45  mm.  In  France  the 
carcel  lamp  is  used,  burning  hourly  42  grammes 
colza  oil. 

The  relation  of  these  normal  flames  is,  accord- 
ing to  Schilling — 


Figs.  105  and  106. 


German  Candle. 

Munich  Candle. 

English  Candle. 

Carcel  Lamp. 

IOOO 
1128 

887 
IOOO 

977 

1  102 

I  O2 
H5 

1023 
9826 

907 
8715 

IOOO 
9600 

104 
IOOO 

Monier  found  i  carcel  =  7-5  German  candles  = 
7'5  bougies  d'etoile  =  6'5  Munich  candles  =  8'3 
English  candles.  If  we  compare  with  these 
figures  the  experiments  of  Violle,  we  may  be  able 
to  compare  the  luminosity  of  paraffine  and  sper- 
maceti candles. 

According  to  the  newest  reports  of  the  Ger- 
man Normal  Candle  Commission,  candles  of  paraf- 
fine, stearine,  and  spermaceti  give  almost  exactly 
equal  lights  if  the  wicks  and  the  height  of  the 
flame  are  kept  alike. 

The  conflicting  statements  concerning  the 
value  of  the  normal  candles  induced  Hefner- 
Alteneck  to  propose  the  following  unit  of  light  • 
it  is  the  light  of  a  flame  burning  in  pure  motion- 
less atmospheric  air,  arising  from  the  section  of  a 
massive  wick  saturated  with  amyl  acetate.  The 
wick  completely  fills  a  round  socket  of  nickel 
silver  of  8  mm.  inner  and  8*3  outer  diameter,  and 
of  25  mm.  length.  The  flame  is  40  mm.  in  height, 
measured  from  the  margin  of  the  wick-holder,  and 
is  shown  by  the  sight-line  over  the  angles,  a  and 
b  (Figs.  105  and  106).  It  is  arranged  by  look- 
ing through  the  point  of  the  flame  to  the  angles, 
a  and  b,  upon  which  the  light  shows,  and  regu- 
lating the  height  of  the  flame  by  turning  the 
milled  head,  S,  so  that  the  point  of  the  bright  nucleus  of  the  flame  just  touches  the 
line  from  below.  The  angles,  a  and  b,  are  kept  bright.  The  wick  does  not  extend 
into  the  flame.  Its  nature  has  no  effect  upon  the  light  as  long  as  it  fills  up  the  socket, 
and  is  able  to  suck  up  the  fuel  in  sufficient  excess.  Hence  it  must  not  be  pressed 
too  tightly  into  the  socket.  The  wick  consists  of  threads  laid  parallel  to  (and  not 


SECT.    I.] 


PHOTOMETRY. 


97 


twisted  or  plaited)  its  length,  so  thick  that  it  can  be  easily  fitted  to  the  diameter  of 
the  socket.  The  wick  is  cut  level  and  horizontal  with  sharp  scissors.  The  quantity  of 
fuel  in  the  lamp  is  not  important,  so  long  as  the  wick  dips  well  in  with  all  its  threads. 
From  time  to  time  the  wick-holder  must  be  cleaned  from  a  thick  brown  deposit.  The  air 
must  be  perfectly  calm,  as  the  slightest  draught  causes  the  point  of  the  flame  to  rise 
and  sink.  This  light-unit  is  equal  to  an  English  spermaceti  candle  at  a  flame-height 
of  43  mm. 

The  International  Conference  held  in  Paris  in  1883-84  adopted  as  the  unit  of  white 
light  the  quantity  of  light  radiated  out  by  i  square  centimetre  of  pure  melted  platinum 
at  the  temperature  of  solidification. 

To  produce  this  platinum  light-unit,  Violle  used  a  platinum  mlting-furnace  of 
lime  which  admits  an  oxy-hydrogen  flame  to  play  upon  the  platinum  through  its  cover. 
When  all  the  platinum  is  fused  the  liquid  mass  has  a  much  higher  temperature  than 
its  melting-point  (1775),  anc^  *ne  liquid  metal  is  placed  behind  or  under  a  double  screen 
with  an  aperture  of  a  certain  width,  through  which  the  light  falls.  The  screen  is 
made  of  platinum  or  copper ;  it  is  double,  and  is  kept  cool  by  a  stream  of  cold  water. 
The  light  rays  passing  through  the  opening  are  thrown  upon  the  photometer  screen. 

Fig.  107  shows  the  apparatus  for  comparing  the  platinum  unit  with  the  carcel 
lamp,  as  constructed  by  Deleuil  of  Paris.  The  carcel,  C,  can  be  moved  upon  a  sledge 

Fig.  107. 


before  the  screen,  E,  of  a  Foucault  photometer.  The  rays  coming  from  both  sources 
of  light  are  separated  by  the  screen,  K.  The  apparatus  for  producing  the  platinum- 
unit  is  on  the  left  side.  F  is  the  Deville  furnace,  the  lid  of  which  is  pushed  back  in 
front  to  uncover  the  surface  of  the  melted  metal.  D  is  the  lid  cooled  with  water,  A 
and  A'  the  entrance  and  exit  for  water.  The  blowpipe  is  connected  with  the  oxygen 
gasometer,  and  the  supply  of  common  coal-gas  by  the  pipes,  O  and  H.  The  whole 
smelting  apparatus  rests  upon  a  little  table,  which  can  be  fixed  at  any  height  by  means 
of  the  screw,  g.  The  mirror,  M,  reflects  back  upon  the  screen  of  the  photometer  the 
rays  which  have  been  let  through  from  the  cover.  If  the  kind  of  light  to  be  compared 
— e.g.,  a  glow-lamp — permits  any  desired  position,  the  disc  of  the  photometer  is  brought 
to  bear  vertically  upon  the  crucible  containing  the  platinum  ;  if,  as  is  usual,  this  is 
impracticable,  the  rays  proceeding  from  the  metal  bath  must  be  deflected  horizontally 
by  a  mirror  or  a  prism,  as  shown  in  Fig.  107.  The  co-efficient  of  absorption  of 
the  mirror  and  the  prism  must  of  course  be  taken  into  account.  When  the  adjustment 

o 


98 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 


has  been  effected,  and  the  rays  of  both  the  sources  to  be  compared  fall  upon  the  screen 
of  the  photometer,  an  equal  illumination  is  obtained  by  displacing  either  the  screen  or 
one  of  the  sources  of  light.  The  equality  is  very  brief,  as  the  melted  metal  cools,  and 
the  emission  of  light  rapidly  decreases.  The  measurement  must  be  effected  whilst  the 
temperature  and  the  light  are  constant.  Violle  gives  the  following  comparison  of  the 
measure  of  light : — 


Platinum- 
unit. 

Carcel. 

French 
Candle. 

German 
Candle. 

English 
Candle. 

Platinum-unit        . 

I 

2'08 

16-100 

l6'4OO 

18-50 

Carcel    

0-481 

I 

7750 

7-890 

8-91 

French  stearine  candle 

0-062 

0-130 

I 

I'O2O 

«*IS 

German  normal  candle 

o'o6i 

0*127 

0-984 

I 

I-I3 

English  candle      

0-054 

0-II2 

0-870 

0-886 

I 

Unfortunately,  little  is  gained  by  proposing  this  international  unit,  as  it  cannot  be 
carried  about  like  a  standard  measure  of  weight,  but  must  be  produced  afresh  on  every 
occasion,  and  requires  preparations  which  will  rarely  be  practicable.  The  amyl  acetate 
lamp  appears  most  practical,  and  will  probably  in  time  supersede  the  other  units. 

Illumination  is  effected — 

1.  By  the  combustion  of  solids  made  up  in  the  form  of  candles,  such  as  tallow, 
stearine,  paraffine,  and  wax. 

2.  By  means  of  liquids  burnt  in  lamps,  either  (a)  liquid  fats,  rape  oil,  olive  oil,  or 
train  ;  (b)  volatile  oils,  petroleum,  solar  oil,  camphine  (purified  oil  of  turpentine). 

3.  By  gases  which  are  either  luminous  in  themselves,  as  coal-  and  oil-gas,  or,  like 
water-gas,  act  by  rendering  solids  incandescent,  such  as  platinum,  magnesia,  zirconia, 
<kc. 

4.  By  electricity. 

LIGHTING  WITH  CANDLES. 

Wax  candles  appear  not  to  have  been  made  prior  to  the  beginning  of  the  fourth 
century ;  tallow  candles  made  their  appearance  in  the  twelfth  century ;  spermaceti 
candles  in  the  beginning  of  the  eighteenth  century;  stearine  candles  in  1834,  and 
paraffine  candles  in  1850.* 

LIGHTING  WITH  LAMPS. 

As  liquid  capable  of  serving  for  the  production  of  light  we  have  (a)  the  fatty  oils, 
(b)  the  volatile  oils,  which  latter  are  either  ethereal  oils,  such  as  camphine,  products  of 
the  treatment  of  the  tar  from  lignite — e.g.,  photogen  and  solar  oil — or  oils  supplied  by 
nature  (petroleum  and  naphtha).  Of  the  fatty  oils  the  most  common  are  rape,  colza, 
olive  oil,  train,  and,  more  rarely,  poppy  oil. 

In  order  to  refine  the  fatty  oils,  they  are  mixed  with  2  per  cent,  of  sulphuric  acid, 
or  a  strong  solution  of  zinc-chloride,  and  well  shaken  up.  These  reagents  do  not 
attack  the  oil  itself,  but  destroy  all  the  mucilaginous  and  other  foreign  matter,  and 
separate  it  out.  On  washing  with  water,  the  acid  and  the  zinc-chloride  are  removed, 

*  Notwithstanding  the  introduction  of  gas  and  of  petroleum  lamps,  the  demand  for  candles  is 
still  increasing.  The  preparation  of  wicks  and  the  process  of  moulding  candles  are  mechanical 
rather  than  chemical  operations  ;  and,  as  much  space  will  be  required  below  for  the  introduction  of 
matter  not  contained  in  the  German  edition,  they  are  omitted.  A  light  obtained  by  the  com- 
bustion of  magnesium  wire  must  not  be  overlooked.  It  is  certainly  expensive,  but  it  resembles 
solar  light  more  closely  than  even  the  electric  light,  and  is  therefore  unequalled  for  use  in  the 
tinctorial  arts  if  it  is  required  to  match  off  colours  after  sunset,  or  in  foggy  or  cloudy  weather. 
If  metallic  magnesium  can  be  produced  more  cheaply,  this  light  will  have  a  great  future. 


SECT,  i.]  LIGHTING   WITH   LAMPS.  99 

and  the  oil  is  thus  purified.  Since  the  rise  of  the  paraffine  and  petroleum  industry  the 
importance  of  the  fatty  oils  as  sources  of  light  has  much  declined. 

Lamps  were  in  use  in  pre-historical  ages.  Elegant  as  were  the  forms  of  those 
employed  by  the  Greeks  and  Romans,  their  construction  was  technologically  most 
imperfect.  If  we  except  a  few  empirically  discovered  improvements,  such  as  the  lamp- 
glass  (chimney)  introduced  by  Quinquet,  and  the  invention  of  the  hollow  circular  wicks 
by  Argand  in  1786,  the  construction  of  a  normal  lamp  has  been  rendered  possible  by 
the  development  of  chemistry — e.g.,  the  theory  of  combustion  and  illumination,  the 
application  of  physical  data  to  the  supply  of  oil  to  the  burner,  and  the  determination 
of  the  illuminating  power  of  the  lamp-flame,  the  refining  of  oils,  and  the  supply  of 
solar  oil  and  petroleum.  In  1850  the  camphine  lamp  was  introduced,  and,  soon  after, 
the  elegant  but  costly  regulators  and  moderators.  In  the  fifties  began  a  struggle  of  the 
oil-lamps  among  themselves,  and  at  the  same  time  against  gas.  In  the  sixties  the 
petroleum-lamp  appeared,  and  has  almost  entirely  superseded  the  oil-lamp.  A  lamp 
contains  the  same  parts  as  a  candle — the  luminiferous  material  and  the  wick.  In  each 
the  material  is  liquid,  and  the  difference  is  merely  that  in  the  candle,  in  the  cup- 
shaped  depression  round  the  wick,  the  fat  (stearine,  tallow,  paraffine,  &c.)  is  burnt  in  a 
melted  condition,  whilst  in  a  lamp  the  material  is  liquid  at  common  temperatures,  and 
requires  a  vessel  in  which  the  liquid  fuel  is  contained,  so  as  to  feed  the  flame  con- 
tinuously and  as  equally  as  possible.  The  great  variety  which  we  see  in  lamps 
resolves  itself  into  the  character  of  the  fuel,  the  form  of  the  wick,  and  the  manner  of 
supplying  air  to  the  flame,  whether  with  or  without  a  draught ;  in  the  shape  of  the  oil 
cistern,  its  position  with  respect  to  the  wick,  and  in  the  conveyance  of  the  oil  to  the 
wick,  whether  by  capillarity  alone  or  in  connection  with  hydrostatic  or  mechanical 
pressure. 

Rape  oil  and  mineral  oil,  whatever  the  character  of  the  latter,  differ  in  the  fact 
that  the  former  at  common  temperatures  does  not  evaporate.  Hence  it  is  inodorous, 
and  cannot  be  ignited.  Only  when  it  has  been  heated  to  such  a  degree  that  the 
products  of  dry  distillation,  especially  inflammable  gases,  are  formed,  do  ign  ion  and 
combustion  of  the  oil  take  place.  Mineral  oil,  even  the  so-called  "  inodorous  "  quality 
of  the  factories,  has  a  smell,  and  on  prolonged  exposure  to  the  air  it  gradually  loses 
weight.  At  higher  temperatures  it  evaporates,  and  may  be  distilled  unchanged.  At 
a  still  greater  heat  it  is  gasified,  and  becomes  chiefly  illuminating  gas.  Refined  rape 
oil  in  a  properly  constructed  lamp  burns  only  in  a  gaseous  form,  and  completely,  yield- 
ing merely  the  inodorous  products,  carbonic  acid  and  watery  vapour.  Solar  oil  and 
mineral  oil  are  mixtures  of  various  hydrocarbons.  They  begin  to  boil  at  250°,  and  at 
higher  temperatures  are  resolved  into  gaseous  products,  and  into  free  carbon.  The 
proportion  of  carbon  in  mineral  oils  is  far  greater  than  in  rape  oil,  as  is  here  shown  : — 


Per  Cent.  Composition. 

i  Kilo. 

i  Kilo  yields  : 

Names. 

for 

Carbonic 

Wntor 

Carbon. 

Hydrogen. 

Oxygen. 

Combustion. 

Acid. 

kilos. 

kilos. 

kilos. 

Stearine 

76*1 

I2'5 

11-4 

2  '92 

279 

•13 

Rape  oil 

77  -2 

I3'4 

9  '4 

3  '°4 

2-83 

'21 

Tallow 

78-1 

117 

9  '3 

2'9I 

2-86 

'OS 

Spermaceti 

8r6 

12-8 

5'6 

3'14 

2-99 

'IS 

Wax   . 

81-8 

127 

5'5 

3'I4 

3'°° 

'14 

Petroleum 

85-2 

14-8 

3'45 

3'12 

'33 

Paraffine 

857 

I4-3 

— 

3  '43 

3'i4 

•29 

Hence  the  first  burns  in  the  open  air  with  a  smoky  flame,  which,  by  the  use  of  a 
draught-glass,  is  at  once  rendered  of  a  dazzling  whiteness  and  strongly  luminous,  the 
combustion  of  the  excess  of  carbon  being  thus  effected  by  the  increased  supply  of  air ; 
whilst  rape  oil  arrives  at  the  flame  only  in  a  gasified  condition,  solar  oil  and  the  less 


IOO 


CHEMICAL  TECHNOLOGY. 


[SECT. 


volatile  part  of  petroleum,  similar  in  its  composition,  enter  the  flame  as  a  vapour. 
Mineral  oil  lamps  must  therefore  be  so  arranged  that  the  combustion  is  effected  as  per- 
fectly as  possible,  and  that  no  trace  of  the  malodorous  vapour  escapes  unconsumed. 

A  normal  lamp,  whatever  its  fuel,  must  be  so  constructed  that  it  gives  out  a  maxi- 
mum of  light  during  a  certain  time,  and  that  as  uniformly  as  possible ;  the  light  pro- 
duced must  also  be  utilised  to  the  beet  advantage. 

Lamps  may  be  classified  according  to  the  manner  in  which  the  fuel  arrives  at  the 
point  where  the  light  is  to  be  evolved.  Thus  we  have — 

(i)  Suction  lamps,  in  which  the  oil  is  brought  up  by  capillary  action  alone  from  a 
lower  receiver.  (2)  Pressure  lamps,  in  which  a  mechanical  or  physical  arrangement 
conveys  the  oil  to  the  wick.  Pressure  lamps  are  again  subdivided  into  (a)  aerostatic 
lamps,  in  which  the  principle  of  Heron's  lamp  comes  into  play ;  (b)  hydrostatic  lamps, 
depending  on  the  principle  of  communicating  tubes  according  to  the  levels  of  liquids  of 
different  specific  gravities  in  connected  tubes ;  (c)  static  lamps,  in  which  the  oil  is 


Fig.  108. 


Fig.  109. 


Fig.  no. 


driven  up  by  a  weight  or  a  piston,  and  (d)  mechanical 
lamps,  in  which  the  oil  is  pumped  up  to  the  burner  by 
means  of  a  train  of  wheel  work  or  by  the  action  of  a 
spring. 

Mineral  oil  lamps  always  act  on  the  principle  of 
suction,  and  they  are  now  the  only  kind  which  require  to 
be  described  and  figured.  Of  the  older  forms  must  be 
mentioned  that  designed  by  R.  Ditmar.  It  consists  (Fig.  108)  of  a  metal  oil- holder,  b, 
which  surrounds  the  wick-holder  in  the  form  of  a  ring,  and  is  connected  with  the 
latter  merely  by  a  horizontal  tube  in  order  to  convey  the  oil  to  the  wick.  An  aperture 
closed  by  a  perforated  screw,  a,  serves  to  introduce  the  oil  into  the  holder,  6.  The 
lamp  has  a  circular  wick  and  a  double  current  of  air ;  it  has  a  glass  chimney  con- 
tracted at  e,  and  resting  on  a  movable  support.  The  chief  part  of  the  luminous 
flame,  which  should  be  altogether  from  6-8  centimetres  in  height,  is  above  the  con- 
tracted part.  The  oil-holder  does  not  become  appreciably  heated. 

In  the  lamp  of  Schuster  and  Baer  of  Berlin,  intended  for  heavy  oils  (Figs.  109 
and  no)  the  air  is  supplied  by  means  of  a  perforated  box,  e,  an  air-tube,  v,  within  the 
combustion  tube  and  the  perforated  support  of  the  disc.  f.  This  lamp  gives,  with 
solar  oil,  a  bright  white,  steady,  and  perfectly  inodorous  flame. 


SECT.    I.] 


GAS   LIGHTING. 


JOI 


The   "  Imperial  lamps "   recently  introduced   give   an-  ,ilb,iaiiB&ting  power'  up  to 
no  candles.     Their  characteristic  feature  is  that  the  air-pipe,  G  (Fig.    in),  passes 


Fig.  in. 


Fig.  112. 


through  the  oil-holder,  F,  with  the  wick,  H. 
The  star-shaped  piece,  J3,  with  the  disc,  A, 
regulates  the  distribution  of  air. 

In  study-lamps  the  radiant  heat  must  be 
guarded  against.     Schuster  and  Baer,  in  their 
"  normal  hygienic  lamp,"  surround  the  ordi- 
nary  cylinder,   a   (Fig.    112),  with  a  second 
cylinder,  so  that  the  dome,  c,  is  kept  cool  by 
the  current  of  air  ascending  between  both. 
The  ligroine  and  sponge  lamp,  proposed  some  thirty  years  ago,  has  not  come  into 
general  use. 

GAS  LIGHTING. 

Burners  for  gas  are  constructed  of  iron,  brass,  porcelain,  or  steatite.  Those  of  the 
two  latter  materials  are  never  choked  in  consequence  of  oxidation.  The  chief  classes 
of  burners  are  the  following  : — (i)  The  single-hole  burner,  a  short,  hollow  cylinder, 
closed  at  top  with  a  plate  having  a  fine  aperture.  (2)  The  slit-burner  has  in  its  button- 
shaped  top  a  cut  like  that  made  by  a  saw.  The  flame  is  flat,  broader  than  high,  and 
is  hence  known  as  the  bat's-wing  burner.  If  two  such  burners  are  inclined  towards 
each  other,  so  that  the  flames  intersect  each  other,  we  have  the  twin-burner,  which  gives 
out  more  light  than  the  two  flames  of  which  it  is  composed.  (3)  The  Manchester 
burner — a  fish-tail — has,  instead  of  the  slit  of  the  bat's-wing,  two  apertures  inclined 
towards  each  other  at  an  angle  of  90°.  (4)  In  the  Argand  burner,  chiefly  used  in 
rooms,  the  flame  consists  of  a  circle  of  small  rays,  each  issuing  from  a  separate  orifice. 
(5)  In  the  Dumas  burner  there  is  a  circular  slit  instead  of  the  circle  of  orifices.  (6)  In 
the  sun-burner,  a  number  of  slit-burners  are  so  placed  that  the  flames  coalesce. 

Of  prominent  importance  are  the  so-called  regenerative  gas-burners,  in  which  the 
gas  and  the  air  are  heated  before  ignition.  The  most  widely  known  of  these  burners  is 
that  of  Fr.  Siemens  (Figs.  113  to  117),  consisting  of  several  upright  receivers  placed 
one  within  the  other.  The  air  entering  through  the  slits  at  a  takes  the  way  indicated  by 


10? 


'*  CHEMICAL   TECHNOLOGY.  [SECT.  i. 

1  ••  >  • 1 1. 

i   ,\ 

arrows  through  the-exterual  ^generation  cells,  d,  in  order  to  burn  outside  the  porcelain 
cylinder,  z,  with  the  gas  escaping  from  the  circular  tubes,  r,  placed  in  the  regenerator. 
The  products   of    combustion   escape   in  part    down   through   the   hollow   porcelain 
Fig.  113.  Fig.  114.  Fig.  115. 


Luft=Air. 


Fig.  116. 


Fig.  117. 


cylinder,  z,  and  the  internal  regenerator,  s,  through  the  support,  g,  into  the  flue  which 

(Fig.  113)  leads  up  on  the  side  of  the  main  body  into  the  chimney  above  the  cylinder,  z  ; 

Fig.  118.  Fig.  119.  Fig.  120.  Fig.  121. 


another  part  of  the  products  of  combustion  passes  directly  upwards  into  the  chimney, 
whilst  the  latter  is  directly  heated  by  a  part  of  the  products  of  combustion  ;  the  portion 
drawn  downwards  through  the  regenerator,  s,  serves  to  heat  the  air  and  the  gases, 


SECT.   I.] 


GAS    LIGHTING. 


103 


Fig.  122. 


The  heated  air  is  especially  divided  and  conducted  by  means  of  the  so-called  dis- 
tributing-combs placed  at  and  above  he  uorifices  of  the  gas-pipes. 

When  it  is  required  to  throw  the  light  downwards,  the  inverted  regenerative 
burner  of  Fr.  Siemens  is  to  be  recommended.  Here  (Fig.  118)  the  gas-pipe,  G,  leads 
into  the  horizontal  gas-ring,  R.  This  has  on  its  lower  side  a  number  of  small  burner 
tubes,  r,  screwed  in  or  wedged  in,  which,  as  shown  in  Fig.  119,  collect  below  to  a 
smaller  circle.  At  the  lowest  and  narrowest  point  of  the  circle  formed  by  the  burner 
tubes,  r,  are  their  orifices,  where  the  gas  meets  with  the  necessary  air  for  combustion 
brought  from  below  (see  the  arrows)  into  the  external  mantle,  M,  and,  with  the  gas,  it 
escapes  downwards  as  flame.  For  the  better  joint  conveyance  of  gas  and  air,  the 
inner  mantle,  m,  has  at  its  lower  end  a  surface  whereby  the  transverse  section  of  the 
transit  is  much  contracted.  (For  further  details  see  the  inventor's  English  patents, 
Nos.  13,701  and  13,788  for  1886.) 

The  regenerative  slit  burner  of  Fr.  Siemens  has  an  ordinary  slit  burner  (Figs. 
1 20  and  121)  with  a  steatite  orifice  so  arranged  as  to  give  a  rounded  flame.  This 
expands  in  the  form  of  a  shell  beneath  the  reflector,  c,  provided  with  many  fine 
apertures,  whilst  the  products  of  combustion  escape  through  the  circular  opening,  i, 
into  the  cast-iron  regenerator,  b,  and  escape  through  the  flue,  d.  The  air  drawn 
through  the  openings  of  the  screen  passes,  strongly  heated,  in  the  direction  of  the 
arrows,  through  the  bottle-shaped  space,  n,  and  the  per- 
forated reflector,  c,  to  the  flame.  A  part  of  the  gas  goes  through 
the  tube,  g,  to  the  arrangement  for  lighting,  h.  This  apparatus 
surpasses  in  power  and  economy  all  the  prior  devices  of  Siemens 
as  well  as  of  others. 

Regenerative  burners  have  also  been  designed  by  J.  R. 
Foster,  and  Wenham. 

Auer  von  Welsbach  deluminises  coal-gas,  burning  it  in  a 
Bunsen  burner  and  igniting  then  in  a  cylindrical  earthen 
screen.  In  this  arrangement  the  quantity  of  light  decreases 
rapidly,  and  the  screen  is  easily  broken,  so  that  the  general 
adoption  of  that  light  is  out  of  the  question. 

Fahnehjelm's  "  globe-light "  has  proved  successful.  A  fish- 
tail burner  is  fed  with  water-gas,  and  rods  of  magnesia,  lime, 
zirconia,  kaolin,  silica,  &c.,  are  ignited.  If  the  iron  comb,  n 
(Fig.  122),  supporting  two  rows  of  magnesia  rods,  is  set  up,  the 
flame  of  the  water-gas  strikes  between  the  rows  of  the  rods  and 
ignites  them  to  whiteness,  when  a  powerful  and  perfectly  white 
light  is  radiated  out.  The  mass  of  which  the  rods  consist  is  chiefly  burnt  magnesia, 
rendered  plastic  by  means  of  starch  and  other  suitable  material.  The  arch  supporting 
the  comb  can  be  fixed  lower  or  higher  by  means  of  a  steel  bar  working  on  a  tapped 
spindle. 

Gillard's  "Platinum  Gas." — In  1846  Gillard  established  works  in  which  hydrogen 
was  obtained  for  illuminating  purposes.  The  hydrogen-flame  was  made  to  play 
through  a  net-work  of  fine  platinum  wire,  which  was  shortly  heated  to  whiteness,  and 
rendered  luminous.  It  was  called  in  Paris  "platinum-gas,"  and  has  been  everywhere 
abandoned. 

Tesste  du  Motay  obtained  hydrogen  by  heating  hydrated  lime  with  coal.  Oxygen 
J  p  obtained  by  first  heating  pyrolusite  with  caustic  soda  to  450°  in  the  air,  forming 
sodium  manganate,  and  then  passing  superheated  steam  over  the  mixture,  when  the 
reverse  reaction  takes  place. 

If  the  mixture  of  caustic  soda  and  sesquioxide  of  manganese  is  heated  in  a  current 
of  air,  it  is  again  converted  into  sodium  manganate.  The  ignited  oxyhydrogen  gas 


104 


CHEMICAL  TECHNOLOGY. 


[SECT.  i. 
The  process 


thus  obtainable  was  passed  over  small  cylinders  of  magnesia  or  zirconia. 
has  been  everywhere  abandoned. 

The  Drummond  light,  obtained  by  exposing  caustic  lime  to  the  flame  of  oxyhydro- 
gen  gas,  has  been  everywhere  superseded  by  the  electric  arc-light. 

H.  Cohn  endeavoured  to  find  the  limit  at  what  quantity  of  light  it  is  still  possible 
to  read  and  write  without  straining  the  eyes.  He  determined  the  time  necessary,  at 
different  grades  of  illumination,  to  read  36  hook-shaped  figures  at  6  metres  distance, 
stating  whether  the  hooks  were  open  upwards,  downwards,  to  the  right  or  to  the  left. 
He  found  that  with 

I  candle   0-12  hooks  were  read  in  40-60  seconds  with  very  many  faults 
5  candles      36      „  „  48-73        „        with  many  faults 

10      „  36      „  „  30-60        ,,        with  some  faults 

20       „  36      „  „  22-26        „        correctly 

50      „  36      „  „  l7-25        i>         as  in  good  daylight. 

He  determined  also  that  in  a  minute  twelve  lines  of  newspaper  print  could  be  read 
with  ten  candles,  sixteen  lines  with  fifty  candles,  as  in  the  daylight ;  ten  candles  are 
therefore  the  lowest  light  which  a  work-room  should  have. 

The  following  conspectus  shows  the  cost  of  the  chief  kinds  of  illumination  for  100- 
candle  hours  : — 


How  the  Hourly  Production  of  100  Candles  are  required. 

Thereby  Evolved. 

Kind  of  Light. 

Quantity. 

Price  in  Shil- 
lings and  lOOths 
of  a  Shilling. 

Water, 
kilos. 

Carbonic 
Acid. 

cub.  met. 

Heat. 

ihermic-units. 

Electricity,  arc  light      .        .        . 
„            glow  light  . 
Gas,  Siemens  regen.  burner  . 
„     Argand  burner       .        .        . 
„    two-hole  burner     .        .        . 
Petroleum,  round  burner 
flat 
Solar  oil,  Schuster  and  Baer's  lamp 
flat  

O'09-O'25  h.p. 
o  '46-0  "85    „ 
0-35-0-56  c.m. 
0'8-(2) 
0'2-(8) 
O'20 

o'6o 

0-28 

o-6o 

o'43 
0-70 
077 
077 
077 
0-92 

I  '00 

O  'Ofo-O*  1  2O 
O'150-O  '3OO 

o-o63-o'ioi 
o'  144-0-360 
0-360-1-440 
0-040 

0-120 

0-062 

0-132 
0-413 

0-672 

1-390 

2-700 

3-080 
1-660 

I  -600 

0-86 
2-14 

O'22 
0-80 

0'37 
0-80 
0-52 
0-85 
0-99 
0-89 

0-88 
1-04 
1-05 

traces 

0*46 
1-14 
0-32 

0-95 
0-44 

0'95 
o-6i 

I'OO 
I  '22 

I-I7 

1-18 
1-30 

i'45 

57-158 
290-536 
1,500 
4,860 
1  2,  1  50 
2,4OO 
7,20O 
3.360 
7,20O 
4,2OO 
6,800 
9,20O 
7,960 
7,960 
8,940 
9,700 

Kape  oil  (carcel)    .         .         .         . 
„         (study  lamp)    . 

Wax                

As  regards  the  pollution  of  the  air,  carbonic  acid  and  watery  vapour  have  to  be 
first  considered.  From  the  figures  in  the  table,  it  follows  that  solar  oil  and  mineral  oil 
give  off  the  least  carbonic  acid  and  watery  vapour,  gas  and  tallow  the  most.  In  the 
Siemens  regenerative  burner  they  are  conveyed  outside. 

A  contamination  of  the  air  with  carbon  monoxide  and  hydrocarbons  is  not  to  be 
apprehended  in  the  case  of  burners  furnished  with  cylinders.  Petroleum  lamps  smell 
only  if  the  flame  is  much  too  large  or  too  small,  or  if  the  lamp  is  not  kept  clean.  With 
free-burning  flames,  as  the  air  is  rarely  quite  steady,  a  contamination  of  the  atmosphere 
with  carbon  monoxide  is  likely  to  occur.  Coal-gas  always  contains  sulphur,  and  yields 
on  combustion  sulphurous  and  sulphuric  acids,  which  act  injuriously  upon  window- 
plants,  possibly  upon  the  inhabitants,  as  well  as  upon  books,  pictures,  articles  of  metal, 
and  upon  curtains,  &c.  The  mineral  oils  of  commerce  often  contain  sulphur.  Ordinary 
gas-lighting  occasions  more  heat  than  oil -lighting.  Among  candles,  those  of  tallow  are 
the  least  advantageous. 

"Where  economy  is  considered,  solar  oil,  and  especially  petroleum,  are  to  be  employed ; 


Fig.  123. 


SECT,  i.]  ELECTRIC    LIGHT.  I05 

gas-lighting  is  dearer,  and  pollutes  the  air  more,  but  it  is  convenient.     When  other 
circumstances  allow,  gas-lights,  with  regenerative  burners  or  electric  glow-lamps,  are 

preferable,  as  they  do  not  pollute  the  air,  and  give  the  least  heat.     For  a  study or 

generally  a  working  light — the  author  prefers  a  good  mineral  oil  lamp  as  giving  the 
steadiest  flame. 

ELECTRIC   LIGHT. 

The  electric  light  is  suited  for  large  halls  and  gardens,  where  beauty  is  to  be  con- 
sidered rather  than  economy.  For  lighting  up  streets,  manufactories,  and  railway 
stations,  it  is  cheaper  than  gas  only  where  a  cheap  motive  power  is  available. 

In  estimating  the  arc-light,  we  must  consider  that  with  continuous  currents  the 
positive  carbon,  which  is  always  placed  as  the  upper  one,  takes  the  form  of  a  blunt 
point,  often  with  a  small  hollow  in  place  of  its  point ;  whilst  the  lower,  negative  car- 
bon, remains  pointed,  or  has  in  any  case  a  very  convex  summit.  At  the  lower  point 
only  a  small  part  is  luminous,  whilst  by  far  the  chief  portion  of  the  light  comes  from 
the  internal  side  of  the  concavity  of  the  upper  carbon,  and  is,  of  course,  thrown  entirely 
downwards.  This  is  best  seen  if  the  light  is  enclosed  in  a  globe  of  translucent  glass. 
The  upper  part  of  the  globe  is  comparatively  dark ; 
the  lower  very  luminous  except  quite  at  its  bottom, 
where  the  shadow  of  the  lower  carbon  is  visible. 
The  limits  between  the  two  zones  are  never  hori-  **-, 
zontal,  but  more  or  less  slanting,  especially  when  the 
carbons  are  not  quite  straight.  It  is  seen  at  once 
that  measurements  of  the  free  light  in  a  horizontal 
direction — as  was  formerly  customary — give  very 
uncertain  results.  According  as  the  naked  light 
happened  to  be  measured  from  the  one  side  or  the  %«£ 
other,  it  might  be  taken  in  the  dark  or  the  light 
zone. 

Fig.  123  shows  the  little  apparatus  with  which 
such  measurements  are  conducted  by  the  firm  of 
Siemens  &  Halske.  It  consists  chiefly  of  a  small  mirror,  S,  fixed  to  a  movable 
curved  arm,  A.  The  supporter  of  the  entire  apparatus,  I),  can  be  fixed  to  an 
electric  lamp  (of  which  only  the  upper  part  is  shown)  by  means  of  the  screw,  R.  This 
is  effected  so  that  the  prolongation  of  the  axle  on  which  the  arm,  A,  turns,  passes 
through  the  arc.  This  prolongation  is  brought  into  the  axis  of  the  photometer  (placed 
at  a  distance),  to  which  the  arrows  in  the  figure  are  pointing.  The  mirror,  $,  in  every 
one  of  its  positions  is  equidistant  from  the  arc,  and  so  inclined  that  it  reflects  to  the 
photometer  the  rays  falling  from  the  arc  upon  its  middle  always  at  a  right  angle, 
Z,  p,  o.  Between  tho  photometer  and  the  arc  is  the  metal  disc,  B,  which  prevents  the 
passage  of  the  direct  rays  to  the  photometer.  On  the  other  hand,  the  cone  of  rays 
from  the  image  of  the  arc  in  the  mirror  arrives  unhindered  at  the  photometer.  The 
inclination  to  the  horizon  at  which  these  rays  are  emitted  corresponds  to  the  inclina- 
tion of  the  arm,  A.  It  is  read  off  on  the  index,  z,  and  the  graduated  dial,  C.  The 
counterpoise,  G,  serves  for  the  mirror  and  the  arm,  A,  which  is  kept  in  each  of  its 
positions  by  a  slight  friction.  In  order  to  deduce  the  absolute  value  from  the  measured 
results,  the  co-efficient  of  absorption  of  the  mirror  must  be  ascertained  and  taken  into 
account.  As  the  angle  of  reflection  is  always  the  same,  this  co-efficient  does  not  vary ;  it 
may  be  determined  once  for  all.  For  this  purpose  the  mirror  is  turned  downwards, 
and  the  lamp  is  turned  90°  round  the  perpendicular,  so  that  the  rays  fall  directly  from 
the  arc  towards  the  photometer  in  the  same  plane  as  they  are  to  be  previously  or  after- 
wards measured  by  means  of  the  mirror,  also  in  horizontal  radiation.  The  very  trifling 


io6 


CHEMICAL  TECHNOLOGY. 


[SECT.  .  i. 


alteration  which  the  angle  of  incidence  of  the  rays  undergoes  in  the  photometer  in 
consequence  of  the  lateral  application  of  the  mirror  is  measured  simultaneously,  and 
therefore  compensated. 

In  Fig.  1 24  the  intensities  of  light  are  shown  graphically  in  the  curve,  a  ;  they  are 
measured  by  means  of  the  apparatus  Fig.  123,  from  a  light  having  9*4  amperes  strength 
of  current  and  45  volts  difference  of  tension  at  the  carbons.  The  upper  carbon  is 
1 1  mm.  and  the  lower  9  mm.  in  thickness.  The  line  OB  shows  the  horizontal,  and 
0  the  source  of  light.  The  strengths  of  the  light  from  0  onwards  are  plotted  out  upon 
lines  which  have  the  same  inclination  as  OB.  The  values  given  are  the  means  of 
many  measurements ;  indeed,  in  the  measurement  of  the  electric  light  we  must  never 
be  content  with  single  observations,  but  must  collect  copious  experience  to  escape  very 
glaring  errors.  From  the  course  of  this  curve  we  see  at  once  that  the  maximum  of 
light  is  given  off  at  an  angle  of  about  37°  with  the  horizon,  where  it  is  more  than  six 
times  greater  than  in  the  horizontal  plane. 

But  the  case  is  complicated  by  the  circumstance  that  in  practical  use  the  question 

becomes  involved  by  the  enclosure  of  the  light  in 
translucent  globes  or  lanterns.  These  are  used, 
not  merely  to  prevent  dazzling,  but  chiefly  be- 
cause all  the  lower  parts  of  the  lamp,  every 
spoke  of  the  lamp,  and  every  irregularity  in 
clear  glass  would  throw  very  sharp  and  ugly 
shadows.  In  so-called  mat  and  alabaster  glass 
the  loss  thus  occasioned  is  15  per  cent.,  in  opal 
glass  above  20,  and  milk  glass  above  30  per  cent. 
This  loss  of  light  is  greatest  in  the  direction 
of  the  strongest  rays,  the  inequalities  of  the 
illumination  being  thus  equalised  at  the  cost  of 
the  maxima. 

Von  Hefener-Alteneck  made  accurate  ex- 
periments with  a  larger  mirror  apparatus.  The  curve  c  (Fig.  124)  thus  ascertained 
corresponds  to  a  lantern  of  ground  glass ;  the  curve  b  to  a  new  globe  of  a  glass  not 
very  opaque.  Reflectors  placed  above  are  of  little  value,  as  the  smallest  part  of  the 
light  is  thrown  upwards,  so  that  the  gain  is  trifling  in  comparison  with  the  incon- 
venience and  the  expense. 

With  reference  to  the  values  determined  by  the  Paris  Commission,  and  to  the 
assumption  that  i  cubic  metre  of  coal-gas  yields  hourly  i  horse-power,  Voit  has  calcu- 
lated the  following  table  : — 


i  cubic  metre  of  gas  yields— 
in  a  one-hole  burner  . 
in  an  Argand  burner  . 
in  a  small  Siemens  burner 
in  a  large        „  „ 

in  glow-lamps    . 
in  arc-lamps 


80-160  (mean) 
250-750 


45  units  light 

7o 
141 
145 
110  „ 

490 


Hence  gas  is  used  for  lighting  more  appropriately  (though  not  always  more  cheaply) 
if  it  is  burnt  in  a  gas  engine  which  drives  a  dynamo  and  feeds  an  electric  lamp  than  if 
it  is  used  directly  in  a  burner. 

The  disposable  work  in  gas  is  not  entirely  utilised  as  light,  but  to  a  great  degree  as 
heat.  From  other  considerations,  it  appears  that  a  body  at  higher  temperatures  emits 
a  greater  proportion  of  external  work  as  light,  and  a  smaller  as  heat.  It  may  therefore 
be  understood  that  i  cubic  metre  of  gas  can  develop  larger  quantities  of  light  at  the 
higher  temperatures  of  the  above  table. 


SECT,  i.]  ELECTRIC   LIGHT.  107 

We  must  notice  the  intensity  of  light.  Two  sources  of  light  may  send  out  the  same 
quantity  of  light,  but  one  of  them  has  a  large  and  the  other  a  small  surface,  so  that  the 
former,  from  a  given  unit  of  surface,  emits  a  smaller  quantity  of  light  than  the  other. 
This  light  sent  out  from  a  superficial  unit  is  called  the  intensity  of  the  source  of  light. 
If,  for  the  sake  of  simplicity,  we  assume  that  each  part  of  the  surface  of  the  two  sources 
of  light  emits  the  same  quantity,  we  find  the  intensity  by  dividing  the  total  light  emitted 
by  the  surface  of  the  luminous  body.  The  rays  of  the  sun  passing  through  an  orifice 
of  o-9  mm.  diameter  correspond,  according  to  Sir  W.  Thomson,  to  126  candles  =  about 
20,000  candles  per  square  centimetre.  Moonlight  is  equal  to  the  light  of  a  normal 
candle  at  the  distance  of  2*3  metres. 

In  this  manner  the  luminosity  of  i  square  centimetre  of  surface  is  found  :  — 

Single-hole  burner      .        .        .        .        0*06  candles 

Argand       ......        0*30      „ 

Small  Siemens    .....         0-38      „ 

Large       „  .....         o'6o      „ 

Glow-lamps  '•      .....       40x10      „ 

Arc-lamps  ......     484x10      „ 

*  The  glow-lamp,  or  incandescent  lamp,  is  a  mode  of  obtaining  light  by  electric  action 
perfectly  distinct  from  the  arc  light.  It  is  well  known  that  if  in  a  good  electric  conductor,  through 
which  a  current  is  being  passed,  there  is  introduced  a  short  piece,  having  a  very  high  resistance, 
we  have  in  such  a  short  piece,  in  accordance  with  Joule's  law,  a  very  considerable  evolution  of 
heat,  which,  if  the  current  is  sufficiently  powerful,  renders  it  incandescent  and  luminous.  If  such 
a  short  and  resistant  piece  is  enclosed  in  a  vacuum,  and  if  it  is  relatively  long  in  proportion  to 
its  diameter,  so  as  to  increase  the  resistance,  we  have,  in  substance,  the  glow  lamp.  A  variety  of 
practical  conditions  are  essential  —  the  vacuum,  which  should  be  very  high,  has  to  be  enclosed  in  a 
glass  globe,  or,  more  commonly,  a  pear-shaped  vessel.  This  vessel  must  be  so  constructed  that  the 
air  may  be  readily  exhausted,  and  be  then  sealed  up  so  as  to  allow  no  entrance  of  air.  The  two 
wires  are  also  sealed  into  the  neck  of  the  vessel  in  such  a  manner  that  the  current  can  pass  from 
the  one  to  the  other  only  by  traversing  the  filament  which  is  to  be  rendered  incandescent.  The 
nature  and  preparation  of  this  filament  have  been  the  critical  points  of  the  invention.  The 
earliest  glow-lamps  constructed,  those,  e.g.,  of  Lontin  de  Clangy,  King,  and  Lodyguine,  had  spiral 
platinum  wires,  as  had  also  those  of  Edison  in  his  first  attempts.  The  conclusion  was  soon  reached 
that  a  filament  of  carbon  was  preferable  to  one  of  metal,  on  account  of  its  higher  durability. 
Wood  charcoal,  retort  charcoal,  &c.,  were  successively  tried,  and  in  1879  Edison  prepared  filaments 
from  carbonised  bamboo.  Other  materials  have  since  been  used  by  Swan,  Lane  Fox,  Crookes,  and 
others,  such  as  gelatine,  collodion,  cotton,  &c.,  the  main  condition  being  the  production  of  a  fibre 
equally  thick  and  strong  throughout  its  entire  length.  Before  carbonising,  therefore,  the  fibres  are 
carefully  examined  with  an  apparatus  capable  of  indicating  the  hundredth  of  a  millimetre.  They 
are  then  charred  in  a  fire-clay  muffle,  or  in  a  Hessian  crucible,  every  layer  of  fibres  being  covered 
with  charcoal  dust  or  graphite.  The  crucible  is  then  filled  up  with  the  same  material,  and  the  lid  is 
carefully  luted  on.  When  the  luting  is  dry  the  crucibles  are  placed  in  the  furnace  and  ignited  for 
five  hours  to  iooo°-i2OO0.  The  higher  and  more  uniform  the  heat  the  better  is  the  quality  of  the  fila- 
ments. The  specific  resistances  of  the  different  materials,  that  of  mercury  being  taken  =  i,  are  — 

Charred  bamboo  fibre         .....     62-56 


Unprepared  collodion  carbon    ....     39'9o 
Prepared  „  .        ...     22*00 

Chemical  retort  carbon      .....       7*17 

Lamps  are  classified  according  to  their  luminous  power.  They  are  generally  made  to  give  the 
light  of  8,  10,  1  6,  20,  25,  and  32  candles,  those  of  i6-candle  power  being  in  greatest  demand. 
In  gauging  the  lamps,  accurate  photometry  is  essential.  Silvanus  Thompson,  instead  of  the  grease 
spot  on  the  screen,  uses  two  pieces  of  paraffine  or  milk  glass,  between  which  is  laid  a  polished 
slip  of  sheet  silver.  This  arrangement  is  more  convenient  and  more  sensitive  than  the 
fat  spot.  The  duration,  or,  as  it  is  technically  called,  the  lifetime,  of  a  glow-lamp  varies, 
according  to  the  current  used,  from  300  to  2400  hours.  The  great  recommendation  of  the  glow- 
lamp  is  its  universal  applicability.  It  gives  off  very  little  heat,  does  not  contaminate  the  air  with 
the  products  of  combustion,  and  reduces  the  risk  of  fire  to  a  minimum.  As  compared  with  the 
arc  light,  the  glow-lamp  has  the  advantage  of  absolute  steadiness. 


SECTION    II. 
METALLURGY. 


ONLY  the  chemical  processes  of  metallurgy  can  here  be  discussed,  as  the  mechanical 
arrangements  form  a  part  of  mechanical  technology. 

Few  metals  occur  native;    most  of  them  are  found  in  the  mineral  kingdom   in 
chemical  combinations  known  as  ores  and  as — 

(1)  Elements  :  e.g.,  gold,  platinum,  bismuth,  copper. 

(2)  Chlorides  and  fluorides :  Compounds  of  the  monovalent  elements  chlorine  or 
fluorine  with  metals  (if  heated  with  sulphuric  acid,  they  give  off  HC1  or  HF) — e.g., 
sodium  chloride,  carnallite,  cryolite. 

(3)  Oxides  :  Oxygen  compounds  of  the  metals  with  or  without  hydrogen — e.g.,  red 
copper  ore,  hydroferrite,  and  anhydroferrite. 

(4)  Sulphides  and  corresponding  compounds  :  Sulphur  and  arsenic-combinations  of 
the  metals  (if  laid  on  ignited  charcoal,  they  give  off  S02  or  the  odour  of  arsenic — e.g., 
iron-pyrites,  galena,  blende,  proustite). 

(5)  Sulphates :  Compounds  of  the  general  formula  RUS04  (if  melted  upon  charcoal 
with  soda,  they  give  sodium  sulphide  ;  heated  with  soda  in  a  tube,  their  watery  solution 
gives  with  BaCl2,  BaS04  insoluble  in  hydrochloric  acid — e.g.,  gypsum  and  heavy-spar). 

(6)  Borates :  If  heated  on  a  platinum  wire  with  H2SO4,  they  tinge  the  edge  of  the 
flame  a  fine  green — e.g.,  boracite. 

(7)  Nitrates :  Compounds  of  the  general  formula  RjNOg  (they  are  soluble  in  water, 
and  deflagrate  on  charcoal — e.g.,  cubic  nitre). 

Dressing. — Ores  mostly  require  to  be  broken  up  and  separated  from  foreign  ores 
and  from  the  accompanying  earthy  or  stony  masses  (gangue).  This  separation  is,  of 
course,  mechanical,  and  is  often  begun  at  the  mine.  The  ores  are  generally  sorted  into 
three  heaps  :  the  first  heap  is  so  rich  that  it  can  be  at  once  smelted  ;  the  second  heap 
contains  medium  ore,  which,  before  smelting,  has  to  be  further  freed  from  mechanical 
impurities ;  whilst  the  third  heap  consists  chiefly  of  gangue,  so  that  the  little  metal 
which  it  contains  is  not  worth  the  cost  of  extraction. 

Preparation. — By  the  above-mentioned  dressing  the  ores  are  rendered  rich  enough 
for  further  treatment.  Before  smelting,  a  preparation  of  the  ores  is  often  required, 
which  in  some  cases  consists  of  exposure  to  the  air — weathering  ;  or  in  heating  without 
access  of  air — burning  ;  or  heating  with  access  of  air — roasting.  Weathering  effects  a 
mechanical  separation  of  the  clay,  shales,  &c.,  from  the  nodules  of  ore,  as  it  is  chiefly 
done  in  iron  ores  and  calamine ;  sometimes  it  effects  also  an  oxidation  of  iron  ores  and 
of  accompanying  pyrites  to  form  copperas,  which  is  then  washed  away  by  the  rain. 
Burning  or  calcination  loosens  the  texture  of  certain  ores,  such  as  ironstone,  calamine, 
copper- shales,  by  expelling  volatile  matter  such  as  water,  carbon  dioxide,  bitumens,  or 
merely  by  the  expansive  power  of  heat.  Roasting  effects  merely  an  oxidation — e.g., 
magnetic  iron  ore  ;  or  a  simultaneous  expulsion  of  certain  matters.  Blende,  e.g.,  on 
roasting,  yields  zinc  oxide  and  S02  (see  Zinc),  arsenides  evolve  arsenious  acid,  and 
cinnabar  is  split  up  into  mercury  and  sulphurous  acid.  Ores  are  in  some  cases 
roasted  with  the  addition  of  common  salt  (see  Silver). 

Smelting. — Single  kinds  of  ore  are 'rarely  smelted  by  themselves;  in  general,  richer 


SECT.    II.] 


METALLURGY. 


109 


and  poorer  qualities  are  mixed  together,  so  as  to  bring  the  whole  to  a  medium  standard. 
Attention  has  also  to  be  paid  to  the  portions  of  gangue  which  still  accompany  the  ore,  so- 
that  the  slag  produced  may  be  of  a  suitable  quality.  For  this  purpose,  certain  materials 
are  in  most  cases  added,  which  are  known  as  roasting  materials  (charcoal,  coke,  coal, 
quicklime,  and  common  salt) ;  or  as  fluxes,  quartz,  and  certain  silicates  (hornblende, 
felspar,  augite,  chlorite,  and  old  slags) ;  calcareous  minerals,  such  as  limestone,  fluor- 
spar, gypsum,  and  heavy  spar ;  aluminous  minerals,  such  as  clay  slate  and  clay,  &c. ;  saline 
fluxes,  such  as  potash,  soda,  borax,  salt-cake,  soda,  saltpetre  ;  metallic  additions,  such  as 
iron  (in  the  decomposition  of  cinnabar  and  galena),  zinc  (for  the  separation  of  silver  from 
lead),  arsenic  (for  increasing  the  proportion  of  nickel  and  cobalt  in  speiss),  iron-slack,  red 
and  brown  haematite  in  the  puddling  process;  additions  rich  in  such  materials,  as  puddling- 
slags,rich  in  ferrous  oxide,  and  which  act  either  by  their  proportion  of  oxygen  (in  puddling 
iron),  or  by  their  iron  as  a  precipitant  (in  separating  lead  from  galena).  Fluxes  merely 
promote  the  separation  of  the  metal  by  increasing  the  fluidity  of  the  melted  mass,  so  that 
the  particles  of  metal  may  unite  more  easily.  They  may  be  arranged  in  three  classes — ( i ) 
such  as  have  little  chemical  action,  but  merely  promote  fusibility,  such  as  fluor-spar,  borax, 
common  salt ;  (2)  those  which  in  addition  have  a  reducing  action,  such  as  black  flux  (a  mix- 
ture of  tartar  and  saltpetre) ;  (3)  those  which  act  by  absorbing  either  acids  or  bases. 

Mixing  is  the  operation  by  which  the  ore  and  the  additional  materials  and  fluxes  are 
mixed  together.  The  quantity  used  in  a  period  of  twelve  to  twenty-four  hours  is  called 
the  charge. 

Furnace  Products. — The  products  of  the  smelting  process  are  either — (i)  Metals 
(educts).  The  degree  of  purity  in  the  precious  metals  is  expressed  by  fine  (fine  silver, 
fine  gold) ;  in  the  base  metals  we  speak  of  raw  or  crude  metal,  whilst  a  higher  grade  of 
purity  is  indicated  as  refined.  (2)  Such  furnace  products  as  are  not  already  contained  in 
the  ores,  but  are  formed  by  the  reactions  taking  place  during  smelting,  are  many  of  them 
articles  of  commerce,  such  as  hard  lead  (antimonial  and  arsenical),  spiegeleisen,  the 
various  sorts  of  steel  (such  as  Bessemer  steel,  cement  steel,  &c.),  the  arsenical  products 
(arsenious  acid,  orpiment,  and  realgar),  antimony  sulphide,  &c.  There  are  often  also 
by-products,  which,  if  capable  of  further  elaboration,  are  (3)  intermediate  products,  or, 
in  the  opposite  case,  (4)  waste  or  dross. 

The  intermediate  products  are  alloys,  "  teller  silver,"  consisting  of  silver,  copper,  and 
lead ;  work-lead,  lead  containing  some  silver  or  copper ;  black  copper,  consisting  of 
copper  with  iron  and  lead,  &c. ;  arsenides,  speises ;  carbides,  crude  iron  and  steel ;  and 
oxides,  such  as  litharge. 

Slags. — The  chief  waste  products  of  smelting-furnaces  are  slags,  vitreous  masses 
resulting  from  most  smelting  processes,  the  most  important  of  which  are  silicates,  i.e., 
compounds  of  silica  with  earths  (especially  lime,  magnesia,  alumina)  and  with 
metallic  oxides  (ferrous  and  manganous  oxides).  In  smelting  processes  they  are 
formed  from  the  impurities  never  absent  in  the  ores  and  in  the  admixtures,  and  sub- 
serve the  important  task  of  protecting  the  metal  as  it  is  liberated  from  the  oxidising 
action  of  the  blast.  Their  nature  depends  on  their  proportion  of  silica,  whence  they 
are  divided  into  sub-,  mono-,  bi-,  and  tri-silicates.  The  proportion  of  the  oxygen  of  the 
silica  to  that  in  the  bases  is  as  follows  : — 


Proportion 
ot  O. 

Metallurgical  Name. 

Old  Equivalent. 

New  Atomic  Weights. 

Dualistic  Formula. 

Molecular  Formula. 

B.  |  A. 

I  =3 

Trisilicate 

R2Si3  or  R,,Si9 

2R«0.3Si02  or  2R".,Os.9Si02 

Ru2Si,08  or  R^Si.Og, 

I  :  2 

Bisilicate  . 

RSi  or  RSis 

R»O.Si02  or  R2Os.3SiO, 

R»SiOs  or  Rvi2Si3O8 

l:i| 

Sesquisilicate  . 

R4Si,  or  R4Si9 

4R«O.3Si02  or  4RaO3.9SiOs 

R«4Si3010  or  R^SiAo 

i  :  i 

Monosilicate    . 

R2Si  or  R2Si, 

2RiiO.SiO2  or  2R2Or3Si02 

R»2SiO4  or  R"4Si,0I2 

4:1 

Subsilicate 

R,Si  or  RSi 

3R»O.SiO2  or  R2O3.SiO2 

RiisSiO5  or  RrfjSiO., 

no 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Whilst  in  slags  the  degree  of  silication  does  not  exceed  the  stage  of  a  trisilicate, 
and  it  is  not  yet  ascertained  whether  trisilicates  do  not  owe  their  high  percentage  of 
silica  to  the  presence  of  quartz,  subsilicates  may  occur  of  various  capacities  of  saturation. 
Excesses  of  infusible  bases,  e.g.,  lime,  are  not  uniformly  distributed  in  the  slag. 
Aluminates  are  more  rarely  formed. 

Slags  are  either  vitreous  or  crystalline.  From  the  latter,  crystalline  silicates  often 
separate,  which  exactly  agree  with  natural  minerals,  e.g.,  augite,  olivine,  Wollastonite, 
mica,  idocrase,  chrysolite,  felspar,  &c.  The  mixtures  of  the  monosilicates  generally 
yield  easily  fusible  (basic)  silicates,  whilst  the  bi-  and  tri-silicates  are  acid,  and  solidify 
less  readily.  The  phosphatic  slags  are  of  the  greatest  importance. 

If  a  slag  is  to  have  an  appropriate  composition  it  should  be — (i)  Specifically  lighter 
than  the  product  to  be  obtained,  so  that  it  may  cover  the  surface.  (2)  It  must  be  homo- 
geneous throughout,  as  otherwise  the  smelting  process  is  not  normal.  (3)  It  must  be 
easily  fusible,  so  that  the  particles  of  metal  when  separated  out  may  easily  sink  down 
through  the  liquid  mass.  (4)  A  chemical  composition  such  that  the  slag  cannot  react 
•upon  the  product  obtained. 

Properties  of  Metals. — The  extraction  of  the  various  metals  depends  essentially  on 
their  properties,  and  in  the  first  place  on  their  melting  and  boiling  points.  Arsenic,  e.g., 
melts  only  under  pressure  and  not  below  redness,  whilst  it  sublimes  at  450° ;  it  is 
therefore  separated  by  distillation,  not  by  smelting.  Cadmium  distils  sooner  than 
zinc,  and  can  therefore  be  removed  from  the  latter  by  a  separate  condensation  of  the 
portion  which  first  volatilises.  Cobalt,  manganese,  and  platinum  require  the  highest 
temperatures  for  fusion.  Even  very  small  traces  of  foreign  substances  may  affect  the 
melting-point,  as  may  be  seen  in  the  subjoined  table  : — 




Melting-point. 

Boiling-point. 

Specific 
Heat, 
0-100°. 

Latent 
Melting 
Heat. 
Heat- 
units. 

Heat  of 
Combustion. 

Sp.  Gr. 

Product 
of  Com- 
bustion. 

Heat- 
units 
per 
Kilo. 

Aluminium     . 

600-850° 

above  whiteness 

O'2IO 







2  '60 

Antimony 

425-450 

1040-1050° 

0'050 

— 

— 

— 

6-70 

Arsenic  . 

—  - 

450 

0-076 

— 

ABA 

1030 

570 

Lead 

326-335 

1450-1600 

O-O32 

5'8 

PbO 

243 

11-40 

Cadmium 

310-320 

720-772 

0-055 

137 

— 

8-60 

Iron,  pnre 

1600-1800 

OTI4 

FeO 

1353 

7-90 

„     white,  cast 

1050-1100 

— 

— 

33-o 

— 

7'6o 

„      grey      . 

IIOO-I275 

— 

— 

23-0 

— 

— 

7'10 

„      steel 

1300-1400 

— 

O'll8 

— 

— 

— 

770 

Gold       . 

1035-1250 

— 

0-032 

— 

— 

— 

19-30 

Potassium 

62 

7I9-73I 

— 

— 

K.,0 

*745 

0-87 

Cobalt    . 

1500-1800 

O'IO7 

— 

— 

8-60 

Copper  . 

1050-1300 

— 

0-093 

— 

f  Cu2O 
'(  CuO 

321) 
593! 

8-90 

Magnesium    . 

700-800 

above  whiteness 

0-245 

— 

MgO 

6078 

1-70 

Manganese     . 

1900 

— 

O'I22 

— 

— 

— 

8-00 

Sodium  . 

96 

861-954 

— 

— 

Nap 

3293 

0-98 

Nickel    . 

1400-1600 

— 

0-IO9 

— 

— 

8-90 

Platinum 

I775-200O 

— 

0-032 

27-2 

— 

— 

21-50 

Mercury 

-38-5 

357 

0-034 

2-8 

HgO 

153 

13-60 

Silver     . 

954-1040 

— 

0-056 

2I'I 

Ag20 

27 

10-50 

Bismuth 

260-270 

1090-1450 

0-030 

I2'6 

Bi208 

96 

9-80 

Zinc 

412-420 

930-954 

0-094 

28T 

ZnO 

1300 

7-10 

Tin 

227-230 

— 

0-056 

I3-3 

SnO 

574 

7  '30 

The  specific  heat  of  the  metals  generally  increases  with  the  temperature.  Un- 
fortunately, the  determinations  at  high  temperatures  are  either  very  uncertain  or 
altogether  wanting.  Thus  Bystrb'm,  e.g.,  found  for  iron  at  1400°  0-403,  whilst 
Pionchon  found  considerable  variations  in  its  specific  heat.  The  latent  melting  heat 


SECT.    II. J 


METALLURGY. 


and  the  combustion  or  reduction  heats  are  known  only  for  few  metals  and  even 
these  determinations  can  only  be  regarded  as  approximative.  We  are  therefore  still 
far  from  being  able  to  calculate  the  various  metallurgical  processes,  though  we  see  from 
the  table  that  lead,  bismuth,  and  tin  are  easily  obtained,  and  that  the  separation  of 
mercury  is  easier  than  that  of  zinc. 

If  lead  is  reduced  by  carbon,  with  the  formation  of  carbon  monoxide,  we  have 
for  lead,  -  PbO  +  C  =  Pb  +  CO  -  (206  x  243  =  50,000)  +  29,000  =  -  21,000  heat-units, 
therefore,  for  206  kilos,  of  lead  we  need  only  21,000  heat-units.  But  for  magnesium, 
MgO  +  C  =  Mg  +  CO  -  146,000  +  29,000  =  -  1 1 7,000  heat-units.  In  fact,  the  reduction 
of  magnesia  by  charcoal  or  coke  is  practically  impossible.  For  zinc  we  have: 
ZnO  +  C  =  Zn  +  CO  —  85,000  +  29,000  =—  56,000  heat-units.  For  mercury  only 
HgO  +  C  =  Hg  +  CO  —  30,500  +  29,000  =  -  1500  heat-units,  so  that  in  this  case  scarcely 
any  heat  is  required. 

For  accurate  determinations  the  specific  heats  of  the  metals  must  be  known  at  all 
temperatures,  as  also  the  specific  and  latent  heat  of  the  residues,  especially  the  slags, 
the  latent  boiling-heat  of  the  zinc,  &c.,  which  are  not  yet  determined. 

The  thermo-conductivity  of  the  metals  is  for  a  plate  of  i  mm.  in  thickness  for 
each  i°  difference  of  temperature  of  the  two  sides  and  i  square  metre  per  second,  in 
heat  units  : — 


Metnl. 

Temperature. 

Conductivity. 

Temperature. 

Conductivity. 

Aluminium         ...... 

_^_  —  -^—  —  «^_  ^_ 
0° 

34  '4 

100° 

36-2 

Antimony  .                 

0 

4-2. 

IOO 

4'° 

Lead  

o 

8-4 

IOO 

7'6 

Cadmium  

o 

22  '0 

IOO 

2O'4 

Iron  

o 

W9 

IOO 

14-2 

„      wrought,  &c  

o 

2O'7 

IOO 

IT7* 

Copper       

o 

***  / 
98-2 

IOO 

13   / 
83-3 

Silver         

o 

IO9'6 

Bismuth    

o 

[« 

IOO 

1-6 

Zinc  

o 

*3'5 

Tin    



!5'3 

IOO 

14-2 

(Glass        

60 

0-045) 

The  hardness  of  metals,  as  shown  in  their  resistance  to  cutting,  filing,  boring, 
turning,  and  planing,  is  given  below,  the  hardness  of  lead  being  taken  as  unity  : — 

Lead 

Tin   .        . 
Bismuth    . 
Cadmium 
Gold 
Zinc  . 


Silver 


i-oo 

173 

3'34 

6'95 

10-70 

11-70 

I3-3Q 


Aluminium 

Copper 

Platinum  . 

Wrought  iron  . 

Steel 

Cast  iron,  grey 


17-30 
19-30 
24-00 
60-70 
61-40 
64-00 


Fig.  125. 


Turner,  for  determining  the  hardness  of  metals,  uses  the  arm  of  a  lever,  A,  exactly 
brought  into  equilibrium  by  the  counterpoise,  F,  and  the  screw,  G  (Fig.  125),  upon  the 

*  At  275°=  12-4  heat-unit,-. 


ii2  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

blade,  B.  The  supporter,  0,  rotates  upon  D,  so  that  the  diamond  point,  E,  can  be 
pushed  laterally  on  the  piece  of  metal  in  question,  J,  which  is  held  by  K.  The 
diamond  point  is  loaded  by  means  of  the  weights,  H  and  /,  so  that  it  leaves  a  distinct 
scratch  upon  the  metals.  Results  : — 

Hardness  according  Weight, 

to  Mohs.  grammes. 

Steatite ro  ...  i'o 

Lead 1-5  ...  ro 

Tin 2-0  ...  2-5 

Rock  salt .  2-o  ...  4-o 

Zinc 2'5  ...  6~o 

Copper,  pure 2-5  ...  8*0 

Calc.  spar 3-0  ...  I2'O 

Soft  iron —  ...  15-0 

Fluorspar 4-0  ...  19x5 

Steel  for  wheels 4-5  ...  20-24 

Soft  cast  iron 4-5  . . .  20-24 

Apatite       .        .        .        .•       .        .        .  5-0  ...  34-0 

Hardest  cast  iron       .        .        .        .  •      .  —  ...  72-0 

The  resistance  of  the  most  important  metals  to  rupture  is  expressed   in   kilos. 
for  i  square  mm.  section  as  follows,  according  to  Hugo  Fischer : — 


Tin        .        .      .  .        .        .1 

Lead      .....       I 
Gold      .        ...        .11 

Zinc 13 

Aluminum     .         -        .        .14 
Magnesium  .         .         .         .14 


Silver    .         .         ,         .         .17 
Platinum       .        .         .         .22 

Copper 24 

Iron 30 

Nickel 48 

Steel     .  .80 


The  resistance  to  pressure  in  kilos,  per  square  mm.  is — 

Lead 5 

Bar  iron         ......  30 

Copper .-  57 

Steel 55-79 

The  hardness  and  tenacity  of  metals  are  often  greatly  modified  by  small  admixtures 
and  also  by  mechanical  treatment ;  most  metals  are  rendered  harder  and  more 
tenacious  by  rolling,  hammering,  and  drawing.  This  is  the  case  with  brass,  iron,  and 
platinum  ;  less  so  with  copper,  silver,  and  gold,  and  not  at  all  with  tin  and  lead.  As 
increased  hardness  often  means  increased  brittleness,  it  is  sometimes  necessary,  in  the 
mechanical  manipulation  of  iron  and  brass,  to  heat  the  metal  under  treatment  from  time 
to  time,  so  as  to  render  it  again  soft  and  ductile,  (i)  If  hardness  accompanied  by 
elasticity  is  to  be  obtained,  the  metal  is  hammered,  rolled,  or  drawn  in  the  cold.  (2) 
The  influence  which  the  speed  of  cooling  after  ignition  or  fusion  has  upon  the  hardness 
of  a  metal  is  particularly  manifested  in  the  case  of  steel  and  cast  iron.  (3)  The  tem- 
perature to  which  the  metal  is  raised  before  casting  is  not  without  influence  upon 
the  hardness.  If,  e.g.,  tin  is  heated  to  incipient  redness  and  then  speedily  cooled,  the 
objects  cast  become  hard  and  sonorous ;  hence  tin  for  tin-foil,  tin-paper,  &c.,  which 
must  be  soft  and  flexible,  must  not  be  heated  above  the  melting-point. 

"Very  closely  connected  with  the  crystalline  nature  and  hardness  of  metals  come 
malleability  and  ductility,  collectively  known  as  pliancy.  This  signifies  the  property 
of  metals  to  spread  out  into  thin  sheets  under  the  hammer  or  between  rollers.  For 
this  purpose  a  certain  softness  is  necessary,  so  that  the  metal  may  yield  to  a  moderate 
pressure  or  thrust,  yielding  to  the  force  at  the  point  of  attack,  but  tenacity  is  also 
needed  to  prevent  the  metal  from  losing  its  continuity.  A  hard,  tenacious  metal  is 
pliant  only  when  tenacity  and  hardness  are  in  the  right  proportion.  The  highest 
degree  of  pliability  is  found  in  metals  like  silver,  gold,  and  soft  wrought  iron.  Soft- 


SECT.    II.]  IRON.  tl^ 

ness,  with  deficient  tenacity,  as  in  lead,  does  not  produce  pliability.     Antimony  and 
bismuth  are  brittle. 

In  order  to  convert  the  malleable  metals  into  sheets  they  are  beaten  out  with  the 
hammer  or  rolled  between  steel  and  chilled  iron  rollers.  Those  metals  which  can  be 
rolled  are  also  capable  of  being  drawn  into  wire,  but  the  degree  of  ductility  does  not 
always  coincide  with  their  degree  of  malleability  or  of  being  rolled.  The  metals  are 
the  most  malleable,  reliable,  or  ductile  in  the  following  decreasing  order : — 


Reliable. 
Gold 
Silver 
Aluminium 
Copper 
Tin 

Platinum 
Lead 
Zinc 
Iron 
Nickel 


Malleable. 
Lead 
Tin 
Gold 
Silver 
Aluminium 
Copper 
Platinum 
Iron 


Ductile. 
Platinum 
Silver 
Iron 
Copper 
Gold 

Aluminium 
Nickel 
Zinc 
Tin 
Lead 


Closely  connected  with  tenacity  is  the  resistance  to  mechanical  wear  and  tear,  e.g.t 
friction.  This  resistance  is  high  in  steel,  and  in  cast-iron  poor  in  silicon  and  rapidly 
cooled  on  casting  ;  medium  in  wrought  iron  and  in  cast-iron  cooled  normally,  in 
platinum,  silver,  gold  and  aluminium ;  slight  in  zinc,  lead,  and  tin.  The  power  of 
resistance  can  be  increased  by  suitable  alloying  with  other  metals,  as  lead  with  antimony, 
silver  and  gold  with  copper. 

Certain  malleable  metals,  such  as  soft  iron,  nickel,  and  platinum,  can  be  welded,  i.e., 
pieces  of  such  metals  after  being  softened  by  heat  to  a  certain  degree  can  be  united  into 
one  pjece  by  hammering  and  pressure.  This  can  be  effected  in  other  metals  only  by 
the  use  of  a  suitable  solder. 

IRON. 

The  most  important  iron-ores  (iron  stones)  of  commerce  are : — 

(1)  Magnetic  Ironstone  (Fe304)  ;  it  contains  72  per  cent,  of  iron  and  is  very  widely 
distributed,    especially    in    northern  countries,    Canada,    the    United    States,    Russia, 
Norway,  and  Sweden,  in  the  crystalline  slate  formation.     From  this  ore  is  obtained 
the  celebrated  Swedish  iron,  e.g.,  that  of  Dannemora.     Frequently  it  is  accompanied  by 
pyrites,  galena,  copper  pyrites,  apatite,  and  other  minerals,  which  reduce  its  value  as 
an  iron  ore.     It  is  known  by  its  black  streak. 

(2)  Red  Ironstone  and  Specular  Iron  (Fe203)  contains  69  per  cent,  of  iron.     Red  iron- 
stone, the  massive  or  earthy  variety  of  native  ferric  oxide,  occurs  in  beds  in  primitive 
formations  and  in  quartz,  granite,  &c.     It  occurs  also  in  transition  formations,   and, 
according  to  its  physical  properties,  it  is  known  as  haematite,  iron-ochre,  &c.    It  is  found 
mixed  with  silica  (chamoisite),  with  alumina  (red-clay  iron  ore),  with  compounds  of 
lime  (minette).     Iron  glance  is  crystalline  ferric  oxide ;  its  most  important  deposit  is 
in  Elba.     All  the  red  iron  ores  have  a  more  or  less  decided  iron  colour  and  always  a 
red  streak. 

(3)  Iron  Spar  (FeC03  with  48  per  cent,  of  iron)  contains  almost  invariably  larger 
or  smaller  proportions  of  manganese  carbonate.     It  occurs  in  Styria  and  in  Carinthia. 
Kidney-shaped  or  globular  iron  spar  is  known  as  spherosiderite.     It  is  also  met  with 
as  coaly  iron  ore,  or  black  band  (with  35  to  40  per  cent,  of  iron).     It  is  a  mixture  of 
iron  spar  with  coal  and  clay-slate  deposited  in  the  upper  beds  of  the  carboniferous 
formation  (Scotland,  Westphalia).     Clay  ironstone,  or  clay  band,  especially  in  England, 
Scotland,  Westphalia,  Silesia,  and  the  Banate,  is  an  intimate  mixture  of  iron  spar  with 
clayey  minerals. 

(4)  Iron  spar,  when  exposed  to  the  action  of  air  and  of  water  containing  carbonic 

B 


ii4  CHEMICAL   TECHNOLOGY.  [SECT,  n- 

acid,  forms,  as  secondary  products,  brown  iron  ores  (H3Fe204  to  H6Fe2O6),  which, 
according  to  their  physical  properties,  bear  the  names  lepido-crocite,  pyrosiderite,  and 
stilpnosiderite.  These  ores  often  contain  calcium  carbonate,  silica,  clay,  &c. 

(5)  Bean  ore,  globular  grains  formed  of  concentric  layers,  occurs  in  some  parts  of 
Germany  and  France  in  the  jura  formation.     It  consists  either  of  silica,  ferrous  oxide 
and  water,  or  of  brown  hsematite  and  siliceous  clay. 

(6)  Bog  iron  ore  (limonite,  meadow-ore)  is  found  in  the  alluvium  of  the  North 
German  Plain,  in  Holland,  Denmark,  Poland,  and  Southern  Sweden,  in  peat  bogs, 
beneath  the  grass  of  meadows,  and  at  the  bottom  of  lakes.     It  is  found  in  tuberous 
and  muddy  masses  of  a  brown  or  black  colour,  and  consists  of  hydrated  ferrous  and 
ferric  oxides,  manganic  oxide,  phosphoric  acid,  organic  matter,  and  sand.     The  iron 
which  it  yields  is  well  suited  for  castings,  as  it  is  very  fluid  and  fills  the  moulds  well. 

(7)  Franklinite  (Fes03(ZnOMnO),  with  45  per  cent,  of  iron,  21  percent,  of  zinc, 
and  9  of  manganese,  is  used  as  an  iron  ore  in  New  Jersey,  yielding  also  zinc. 

From  a  metallurgical  point  of  view,  iron  ores  are  classified  according  as  they  are 
easy  or  difficult  to  reduce  and  smelt.  Among  the  former  rank  those  which,  after  a 
preparatory  roasting,  have  a  porous  texture,  so  that  they  are  easily  reduced  and 
smelted  in  the  furnace.  This  is  the  case  with  iron  spar  and  brown  ores,  which  lose  on 
roasting  carbon  dioxide  and  water  respectively.  Specular  iron,  red  haematite,  and 
magnetic  ore  are  hard  to  reduce. 

The  burnt  ores  from  sulphuric  acid  works,  after  their  copper,  zinc,  and  silver  have 
been  extracted  in  the  moist  way,  are  smelted  for  grey  cast  iron. 

(1)   Crude  Iron. 

In  ancient  times,  and  to  a  small  extent  even  yet  in  some  districts,  a  direct  prepara- 
tion of  iron  from  its  ores  was  very  general.  In  this  manner  very  pure  and  tough 
bar-iron  was  obtained,  but  the  process  admitted  only  of  a  limited  extension,  and  the 
ores  were  imperfectly  utilised. 

The  ores  are  roasted  in  heaps  or  in  special  kilns,  in  order  to  expel  carbonic  acid 
and  water,  to  make  the  mass  more  brittle  and  porous,  and  thus  more  susceptible  to 
reduction,  and  to  convert  any  ferrous  oxide  present  into  the  ferric  state,  so  as  to  be  less 
readily  convertible  into  slag.  The  ores,  roasted  or  raw,  are,  if  necessary,  broken  up  by 
means  of  stamps,  rollers,  or  special  crushing  machines  (such  as  Blake's  ore-breaker) ; 
the  richer  ores  are  mixed  with  lower  qualities  (assorted)  in  proportions  which,  accord- 
ing to  experience,  yield  the  best  returns.  The  coal  acts  in  smelting  as  a  source  of 
heat  and  (per  se  as  well  as  in  the  state  of  carbon  monoxide  and  dioxide)  as  a  reducing 
agent.  In  order  to  unite  the  reduced  iron  into  a  mass  before  smelting,  materials  are 
added  which  combine  with  the  gangue  to  form  a  readily  fusible  slag.  This  slag  serves 
for  removing  foreign  matter,  partly  injurious  to  the  quality  of  the  iron,  by  facilitating 
the  coalescence  of  the  reduced  metallic  particles,  and  by  protecting  the  crude  iron  already 
formed  from  the  oxidising  action  of  the  blast.  If  silica  is  deficient,  sand  or  quartz  is 
added ;  if  bases  are  wanting,  limestone  or  fluor-spar  is  supph'ed.  The  charge  as  intro- 
duced into  the  furnace  should  not  contain  more  than  50  per  cent,  of  iron. 

The  smelting  process  is  almost  exclusively  executed  in  so-called  blast  furnaces.  A 
blast  furnace  is  a  round  shaft-oven  (Fig.  126),  surrounded  with  a  strong  wall,  A ;  it  is 
15  to  30  metres  in  height,  the  inner  part  of  which  has  the  shape  of  two  truncated  cones 
fixed  to  each  other  at  their  bases.  The  wall  of  the  shaft,  B,  is  enclosed  by  a  second,  A , 
which  joins  up  to  the  massive  brickwork  of  the  furnace.  Between  the  two  there  is 
left  a  space,  which  is  filled  up  with  a  bad  conductor  of  heat,  such  as  ashes,  and  which 
gives  the  necessary  play-room  for  the  expansion  of  the  inner  shaft  by  heat.  The  part 
from  B  to  C  is  the  shaft ;  that  from  D  to  E,  the  boshes ;  the  part  B,  where  the 
diameter  is  greatest,  is  the  belly  or  upper  part  of  the  boshes.  Below  the  boshes  the 


SECT.    II.] 


IKON. 


space  contracts  to  F,  the  crucible  or  hearth.  Here  the  smelting  process  takes  place, 
and  here  are,  opposite  to  each  other,  apertures  with  conical  tubes  into  which  enter  the 
mouth-pieces  or  tuyeres  of  the  pipes  which  supply  the  furnace  with  air.  The  open  top  or 
mouth  of  the  furnace,  A,  serves  for  introducing  the  charge.  Such  furnaces  were 
formerly  built  on  a  declivity,  so  that  fuel  and  ore,  &c.,  could  be  conveyed  to  the  mouth 
on  a  sloping  road,  or  it  was  brought  over  the  bridge  P.  The  lower  part  of  the  hearth 
is  prolonged  towards  the  front,  forming  the  hearth-pan  or  fore-hearth,  which  is  enclosed 
by  the  dam-stone,  M.  This  stone  stands  off  a  little  from  the  wall  and  forms  a  slit, 

Fig.  126. 


the  so-called  tap-hole,  which  is  stopped  with  clay  during  smelting,  and  serves  afterwards 
to  discharge  the  molten  metal  and  the  slag. 

Latterly,  the  furnaces  are  no  longer  built  so  massive.  The  bridge,  w  (Fig.  127), 
leading  to  the  top,  and  the  upper  wall  of  the  furnace  rest  upon  iron  pillars.  The 
hot  blast  is  introduced  through  a  ring-shaped  pipe,  r,  lying  round  the  furnace  through 
tuyeres  cooled  by  water.  The  furnace  mouth  is  provided  with  a  moveable  cover ;  ore, 
coke,  etc.,  are  thrown  into  the  funnel,  e  ;  the  cover  is  then  raised  for  a  moment  to  let 
the  charge  slide  down  into  the  furnace,  and  it  is  then  immediately  closed,  so  that  the 
gases  are  compelled  to  pass  through  the  top-piece,  g,  and  the  connecting  pipes,  to  the 
apparatus  for  heating  the  air,  or  to  the  boiler  fires. 

Air-Heating. — One  of  the  most  important  modern  improvements  has  been  the  use 
of  the  hot  blast.  The  influence  of  the  raised  temperature  of  the  air  upon  the  con- 
sumption of  fuel  arid  the  performance  of  the  furnace  is  shown  in  the  following  table. 
The  addition  of  purple  ore  served  for  closing  the  joints  of  the  funnel : — 


n6 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Charge  per  Ton  of  Crude  Iron. 

Silicon 

Weekly  Production. 

Heat  of  Blast. 

Coke. 

Limestone. 

Roasted  Ore. 

Purple  Ore. 

per  Cent,  in 
Crude  Iron. 

metric  tons. 

kilos. 

kilos. 

kilo?. 

kilos. 

406 

532 

1209 

584 

2398 

18 

2-4 

415 

631 

"79 

584 

2408 

18 

2-6 

456 

702                    1169 

616 

2408 

18 

2'5 

568 

722 

1157 

618 

2400 

18 

2'5 

465 

760 

1132 

620 

2388 

18 

2'6 

The  heating  apparatus  may  consist  either  of  a  single  chamber  built  of  stone,  serving 
both  for  air  and  heating  gas,  and  which  works  alternately  and  with  interruptions,  or 


Fig.  128. 


it  may  comprise  two  iron  cham- 
bers working  continuously. 
The  stone  apparatus  bears  a 
higher  temperature,  but  re- 
quires a  larger  heating  surface 
in  order  that  the  variation  of 
temperature  on  changing  may 
be  the  smaller.  Hence,  they  aue  more  expensive  to  erect,  but  eheaper  to  maintain, 
though  they  require  trustworthy  attendants  during  the  change.  In  the  iron  apparatus, 


SECT.    II.]  IRON. 

the  temperature  of  the  air  is  limited  (up  to  the  point  at  which  cast-iron  softens),  the 
heating  surfaces  and  the  cost  of  erection  are  smaller ;  the  maintenance  is  more  costly, 
though  the  cleaning  is  easier. 

The  air-heater  of  Whitwell  consists  of  a  sheet-iron  cylinder  A  (Fig.  128),  lined  with 
fire-stone  and  fitted  with  partitions,  a.  The  furnace  gases  led  in  through  B  pass 
through  the  valve-box,  C,  into  the  first  chamber,  where  they  burn  along  with  air  which 
is  introduced  simultaneously,  and  pass  in  the  direction  of  the  arrows  through  the 
apertures,  b,  and  the  valve-box,  D,  to  the  flue,  E.  If  the  stone  lining  is  sufficiently 
heated  the  connection  with  B  and  E  is  closed,  and  blast-air  is  driven  in,  which  takes 
up  the  heat  stored  in  the  stones,  and  passes  through  F  into  the  furnace.  The  top  and 
the  floor  are  provided  with  apertures,  e  e,  for  cleaning. 

In  Macco's  heater,  the  furnace  gases  pass  through  the  flue,  a  (Figs.  129  and  130), 
pass  upwards  in  the  chamber,  b,  of  the  apparatus,  enter  the  grated  chamber,  6,  passing 
downwards,  and  unite  again  in  the  lower  chamber,  e.  Hence  the  gases  pass  into  the 
second  grated  compartment,/,  in  which  they  move  upwards,  arriving  through  the 
aperture,  g,  into  the  last  compartment  of  the  apparatus,  turning  downwards  and 
escaping  through  the  chimney,  at  i.  Both  immediately  after  entering  the  apparatus 
at  the  lower  part  of  compartment,  6,  and  in  the  lower  middle  compartment,  e, 
heated  air  is  conveyed  to  the  gases  for  their  more  complete  combustion.  The 
air  to  be  heated  takes  the  opposite  direction.  By  the  use  of  the  intermediate 
chambers,  d  and  /,  a  large  heating  surface  is  supplied  and  the  air  is  raised  to  a  high 
temperature. 

The  Smelting  Process. — The  furnace  is  heated  first  by  kindling  wood  on  the  hearth 
and  then  introducing  the  fuel  (generally  coke,  sometimes  anthracite,  rarely  crude  coal) 
until  the  entire  shaft  is  filled  with  ignited  matter.  At  the  same  time,  the  blast  is 
turned  on  and  ore  and  fuel  are  introduced  in  successive  layers.  As  the  fuel  burns,  and  the 
ore  and  fluxes,  &c.,  melt,  the  layers  sink  gradually  down.  The  silica  melts  with  the 
earths  and  oxides,  forming  slag,  whilst  the  reduced  semi-liquid  iron  unites  with  carbon 
to  form  an  easily  fusible  crude  iron.  The  melted  iron  collects  at  the  bottom  of  the 
hearth,  and  upon  it  floats  the  slag,  which  is  let  flow  off.  The  liquid  iron  is  from  time 
to  time  run  off  by  opening  the  tap-hole,  and  conveyed  to  the  moulds  through  a 
channel  prepared  in  the  sand  in  front  of  the  furnace.  During  tapping,  the  blast  is 
stopped. 

Heat-conditions  of  the  Blast  Furnace. — According  to  Liirman,  we  must  not  think 
of  the  heat  as  being  distributed  in  successive  zones  of  the  blast  furnace.  The  charges 
tend  towards  the  axis  of  the  melting  column,  and  the  gases  to  the  circumference,  so 
that  here  the  reactions  take  place  more  rapidly  than  in  the  middle.  Heat  is  con- 
sumed— 

(i)  For  the  evaporation  of  water  and  for  the  escaping  gases.  Samples  of  gas  are  to 
be  taken  where  they  are  in  a  state  of  mixture.  For  the  evaporated  water  it  is  not 
sufficient  to  calculate  637  heat-units,  but — 

Heat  =  606-5  +  0-305  (100)  +  0-48  (t-  100). 

For  the  remaining  gases  the  calculation  is  carried  out  in  the  usual  manner.  As  to 
the  quantity  of  dust  thrown  off  at  the  top,  there  are  few  trustworthy  statements. 
Independently  of  the  character  of  the  ores,  the  quantity  of  dust  will  depend  on  the 
rapidity  of  the  charges  and  the  temperature  of  the  furnace.  At  any  rate,  the  escape 
of  dust  is  a  cause  of  the  expenditure  of  heat  and  the  loss  of  material  which  must  be 
taken  into  account.  No  great  error  will  be  committed  if  we  take  as  specific  heat  the 
figure  which  has  been  established  for  porous  refractory  stones  and  fire-bricks  (about 
=  o-22),  and  multiply  it  by  the  temperature  of  the  gas  and  the  quantity  of  dust.  For 
5  per  cent,  of  dust,  or  50  kilos,  per  ton,  and  100°  as  the  temperature  of  the  gas,  the 
•quantity  of  heat  would  be  50  x  400  x  0*22  =  4400  heat-units  per  ton  yield  of  crude  iron. 


n8  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

For  hotter  working,  10  per  cent,  of  dust,  and  a  gas  temperature  of  600°,  we  have 
100  x  600  x  o'22  =  13,200  heat-units. 

(2)  The  liberation  of  carbonic  acid  from  the  carbonates  of  the  ores  and  the  additions 
has  a  great  influence  on  the  entire  character  of  the  blast -furnace  process.     It  absorbs  a 
very  considerable  quantity  of  heat,  and  the  course  of  its  evolution  extends  over  a  great 
space  in  the  furnace  shaft.     Where  there  are  very  abundant  additions  of  limestone, 
the  liberation  of  carbonic  acid  extends  down  to  the  region  of  the  smelting  (strictly 
speaking),  and  perhaps  the  last  traces  of  the  volatile  constituent  of  the  carbonates  is 
expelled  only  by  the  silica,  which  is  already  active  in  the  formation  of  slag.   It  is  decided 
that  the  expulsion  of  carbonic  acid  in  the  blast  furnace,  though  it  probably  begins  at 
800°,  requires  for  its  completion  about  1700°,  whence  the  final  decomposition  of  the 
carbonates  takes  place  in  the  zone  of  the  most  dazzling  white  heat. 

(3)  Processes  of  Reduction. — The  most  important  compound  of  iron  is  the  magnetic 
oxide,  Fe304.     Here  there  must  be  utilised  a  reduction-heat  of  only  1648  heat-units, 
instead  of  the  mean  value  of  1887  heat-units  proposed  by  Grimer  for  iron  oxide;  the 
expenditure  of  heat  per  iron  unit  is  certainly  smaller.     The  decomposition  heat  of  iron 
carbonate,  when  split  up  into  carbon  dioxide,  and  ferrous  oxide  (half  of  which  has  to 
be  further  oxidised  to  ferric  oxide)  has  not  been  measured.     Diirre  takes  in  its  place 
the  heat  of  calcium  carbonate.    The  silicate  is  more  important,  as  considerable  portions 
of  slags  undergo  refining.     For  the  combination-heat  of  ferrous  oxide  and  silica  there 
are  no  accurate  determinations.     According  to  Tholander,  310  heat-units  would  be 
calculated  as  the  combination-heat  of  ferrous  oxide  and  silica.     For  i  kilo,  of  crude 
iron,  containing  95-5  per  cent.  Fe,  there  would  then  be  0-955  x  3IC>  or  296'!  heat-units 
used  in  the  decomposition  of  silicate,  besides  the  reduction-heat  of  the  liberated  ferrous 
oxide  (according  to  Favre  and  Silbermann,  =  1352  heat-units).     We  see  that  the  sum 
1352  heat-units  +  296-1  heat-units  =  1648-1  heat-units  coincide  almost  exactly  with  the 
reduction  heat  of  magnetic  oxide,  1648  heat-units,  whence  we  should  conclude  that  a 
pure  ferrous  silicate  and  the  magnetic  oxide  are  almost  equally  reducible  if  Tholander's 
supposition  is  correct,  and  there  remained  on  the  i-eduction  of  ferrous  silicate,  metallic 
iron  and  free  silica.     It  is  only,  however,  reduced  to  a  small  extent,  whilst  most  of  it 
passes  into  the  slag.     Ferrous  silicate  is  usually  considered  difficult  to  reduce,  though 
easily  fusible,  and,  as  it  generally  holds  in  solution  variable  quantities  of  magnetic  oxide, 
its  reductibility  cannot  be  pronounced  great.     For  the  manganese  compounds  we  may 
provisionally  assume  for  Mn3O4  =  u/8  x  1648  =  2264  heat-units;  for  Mn203  n/8  x  1887  - 
2595  heat-units;  for  sulphur  from  sulphur  acids  3226  heat-units;  for  phosphorus  from 
phosphoric  acid   (P205)    5747;    from  H3PO4  =  9662   heat-units.     Whether  the  lower 
value  is  accurate  must  remain  a  question,  and  only  the  circumstance  that  also  the 
combination-heat  of  iron  phosphide,  as  well  as  the  heat  evolved  by  the  combination  of 
lime  and  magnesia  with  the  slag  cannot  be  determined,  causes  the  proposal  to  use  5747 
instead  of  9662  heat-units  to  appear  less  questionable. 

The  heat  capacity  of  the  reduction  products  is  known  only  in  part,  and  it  is  hence 
difficult  to  form  a  correct  conception  of  the  temperature  at  which  phosphoric  acid  is 
reduced.  In  any  case,  this  reduction  occurs  at  so  high  a  temperature  that  it  takes 
place  on  the  hearth  of  the  furnace  and  in  presence  of  solid  carbon.  Carbon  monoxide 
can  scarcely  be  active  here ;  at  least,  laboratory  experiments  show  that  the  phosphates 
cannot  be  reduced  by  a  current  of  carbon  monoxide  alone.  How  far  the  liquefied  iron 
in  the  blast  furnace  participates  in  the  reduction  of  the  phosphoric  acid  is  hard  to  say. 

Experiments  in  the  refining  process  show  that  the  prolonged  contact  of  metallic 
iron  and  phosphatic  slags  reduces  the  phosphoric  iron  contained  in  the  latter  to 
phosphorus.  On  the  other  hand,  the  first  experiments  with  the  Thomas  and  Gilchrist 
process  have  shown  that  dephosphorised  iron  covered  with  a  phosphatic  slag  can  take 
up  phosphorus  again  on  treatment  with  highly  carburetted  iron  (spiegel-eisen  and 


SECT.    II.]  IRON".  119 

ferromanganese),  which  can  only  have  been  isolated  by  the  transit  of  carbon  monoxide 
through  the  layer  of  slag  or  in  consequence  of  the  action  of  the  same  compound  upon 
finely  divided  iron-phosphates  in  the  liquid  iron.  All  these  processes,  if  further  studied, 
may  lead  to  important  conclusions  on  the  behaviour  of  phosphoric  acid  in  the  blast 
furnace.  Arsenic  acid  scarcely  comes  into  question. 

Of  especial  importance  is  silica.  As  soon  as  from  any  cause  a  very  infusible  slag 
is  formed,  or  is  intended  to  be  formed,  there  is  seen  in  the  crude  iron  a  separation  of 
graphite  regularly  preceded  by  the  taking  up  of  silicon.  The  medium  for  the  reduction 
of  silicon  is  partly  the  silica  in  the  slag,  partly  that  of  the  furnace  walls,  though  these 
first  yield  silica  for  reduction.  According  to  experiments  on  the  reductibility  of  iron 
ores,  we  must  assume  that  a  charge  free  from  slag,  i.e.,  without  the  addition  of  puddling 
slags,  as  it  is  generally  made  up  from  brown  iron  ore,  haematite  and  roasted  iron-spar 
for  the  production  of  Bessemer  iron  is  chiefly  reduced  in  the  shaft,  and  that  by  means 
of  carbon  monoxide,  whilst  a  charge  containing  a  large  proportion  of  slags  is  reduced 
only  on  the  hearth  in  the  state  of  complete  fusion. 

The  nature  of  the  slags  is  here  nearly  indifferent,  since  both  in  acid  and  in  basic 
slags,  in  those  Avhere  calcium  silicates,  and  in  those  where  aluminates  predominate,  the 
iron  takes  up  silicon  and  liberates  carbon  as  soon  as  the  temperature  is  high  enough. 
The  reduction -heat  with  the  combustion-heat  of  silicon  may  be  estimated  at  7830  heat- 
units,  referred  to  the  silicon  of  crude  iron.  The  reduction-heat  of  the  earths  and  the 
alkalies  does  not  come  under  notice. 

(4)  Melting-heat  of  Crude  Iron. — Griiner  has  proposed  mean  values  for  practical 
utilisation,  to  be   applied   when   direct   calorimetric   determinations   have   not  been 
simultaneously  made  on  the  iron,  the  slag,  the  hot  blast  and  the   escaping   gases. 
These  mean  values  are :  300  heat-units  for  grey  cast  iron,  275  for  white  cast  iron,  25 
of  which  may  be  considered  as  latent  in  the  grey  and  35  in  the  white  iron. 

(5)  Melting -heat  of  Slags. — The  most  comprehensive  experiments  have  been  made 
by  Akermann.     For  blast  furnace  slags  he  found  340-410  heat-units.     The  quantity 
of  heat  ascertained  at  the  furnace  itself  will  always  be  greater  than  that  found  in  an 
unmelted  slag,  for  in  addition  to  the  true  melting-heat,  the  slag  flowing  out  of  the 
furnace  contains  the  sum  of  the  heats  of  combination  and  decomposition,  whilst  in 
measuring  the  heat  in  an  unmelted  slag,  the  mere  melting-heat  alone  comes  in  question. 
In  slags  worked  for  grey  cast-iron  we  may  assume  500  heat-units,  and  in  those  for 
white  iron  450  heat-units. 

(6)  Decomposition  of  the  Atmospheric  Moisture. — Griiner  in  his  calculations  assumed 
an  atmospheric  moisture  of  at  least  0^0062  in  his  calculations.     The  influence  of  foggy  or 
wet  weather,  both  upon  the  course  of  the  process  and  the  results,  is  sufficiently  known  to 
every  practical  man,  and  shows  that  attention  to  the  moisture  of  the  air  is  justifiable. 

(7)  Water  and  Air  used  for  Refrigeration. — Some  observers  have  attempted   to 
determine  the  quantities  of  heat  which  have  been  transmitted  to  the  water  and  the 
air  used  for  refrigeration. 

(8)  Losses  include  all  the  heat  expended  upon  the  furnace  itself.     They  can  be 
found  only  in  and  by  subtracting  all  the  known  and  determinable  expenditures  of  heat 
from  the  total  heat  produced,  and  in  spite  of  repeated  experiments  they  have  not  been 
determined  with  certainty.     There  occurs  in  the  first  place  a  transfer  of  heat  from 
the  interior  of  the  furnace  to  the  substance  of  the  walls,  which,  in  the  layers  next  to 
the  interior,  have  almost  the  same  temperature  as  the  adjacent  zone  of  the  furnace. 
A  part  of  the  heat  is  conveyed  through  the  entire  thickness  of  the  walls  according  to 
their  conductivity,  the  size  of  the  surface,  &c.,  to  the  outer  surface  of  the  walls  and 
thence  to  the  ambient  air,  partly  by  radiation  and  partly  by  conduction.     This  quantity 
of  heat  can  scarcely  be  regarded  as  total  loss,  since  the  interior  of  the  furnace  must  of 
necessity  have  the  temperature  of  the  process  going  on  within. 


120  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

The  consumption  of  fuel  in  the  working  of  the  blast-furnace  depends  essentially  on 
the  reducibility  of  the  ores.  The  experiments  of  Akermann  and  Sarnstrom  prove  that 
ferric  oxide  is  reduced  by  carbon  monoxide  to  magnetite.  Already,  at  450°  the 
carbon  monoxide  may  already  contain  20  per  cent,  of  carbon  dioxide  and  still  has  a 
reductive  action  upon  the  oxides ;  at  900°  the  oxide  loses  oxygen  even  in  carbonic 
acid  free  from  carbon  monoxide.  In  order  to  deoxidise  magnetite  at  850°,  the  gas 
must  not  contain  more  than  3  vols.  of  carbon  dioxide,  and  if  the  reaction  is  to  be 
effected  at  300°  to  350°,  the  carbonic  acid  must  not  exceed  2  parts.  To  produce 
ferrous  oxide,  not  more  than  o-5  part  of  carbonic  acid  must  be  present  to  i  part  of 
carbon  monoxide. 

Hence,  the  smallest  consumption  of  fuel  for  a  blast-furnace  may  be  calculated  if  it  is 
possible  to  effect  the  reduction  of  the  ora  with  carbon  monoxide  exclusively. 

According  to  the  formula,  3CO  +  FeO  =  2CO  +  C02  +  Fe,  for  each  mol.  of  iron  there 
must  be  present  at  least  3  mols.  of  carbon  monoxide.  If  the  ore  higher  up  in  the 
furnace  is  in  the  stage  of  oxidation  of-  magnetite,  then,  according  to  the  formula, 
pCO  +  Fe304  =  5CO  +  4C02  +  3Fe,  five  parts  carbon  monoxide  must  be  accompanied  at 
most  by  4  parts  of  carbonic  acid,  whilst  the  same  5  parts  of  carbon  monoxide,  as  far 
as  the  reduction  of  magnetite  is  concerned,  may  be  accompanied  by  at  least  10  parts  of 
carbonic  acid.  If  the  ore  consisted  at  first  of  oxide,  the  equation  3CO  +  Fe2O3  = 
3C02  -i-  2Fe  signifies  that  the  escaping  gases,  if  the  final  reaction  with  carbon  monoxide 
is  to  be  produced,  must  contain  at  least  equal  volumes  of  carbon  monoxide  and  carbonic 
acid,  whilst  oxide  can  be  reduced  to  magnetite  even  with  a  gaseous  mixture  containing 
20  parts  of  carbonic  acid.  Hence,  it  follows  that  the  difficulties  of  reduction  grow 
enormously  with  the  decreasing  grades  of  oxidation  of  the  iron,  and  that  the  final 
reduction  of  ferrous  oxide  requires  much  more  carbon  monoxide  than  is  necessary  for 
the  partial  reduction  of  the  higher  grades  of  oxidation.  For  the  mere  reduction  of 
the  ore  by  means  of  carbon  monoxide,  there  must  be  burnt  by  the  blast  at  least 
3C  :  Fe  =  0*643  kilo,  carbon.  If  we  further  consider  the  4  per  cent,  of  carbon  taken  up 
by  the  raw  iron,  we  have  0-657  carbon.  If  the  ore  was  pure  magnetite,  then  for 
each  kilo,  of  non-volatile  carbon  we  should  have  at  most — 

(3  x  56  +  4  x  16)  :  [(9  x  12)  x  (3  x  12  +  0-04  x  56)  :  (3  x  12)]  =  2-03  kilos, 
of  pure  magnetite ;  then  percentage  of  the  escaping  gases  in  carbonic  acid  and  carbon 
monoxide  would  be  in  volume  o-8o  and  in  weight  1*26.     If  the  ore  was  pure  oxide,  we 
should  have — 

(2  x  56  +  3  x  16)  :  [(6  x  12)  x  (3  x  12  +  0-04  x  56)  :  (3  x  12)]  =  2'io  kilos. 
oxide,  and  the  mixture  of  gas  would  be  roo  or  1*57. 

If  the  reduction  is  thus  to  be  effected  by  carbon  monoxide  alone,  there  must  be 
burnt  with  the  air  of  the  blast  at  least  64*3  kilos,  of  carbon  to  100  kilos,  of  reduced 
iron.  But,  contrary  to  expectation,  this  quantity  in  blast-furnaces  is  often  smaller, 
whilst  the  gases  are  not  richer  in  oxide.  Hence,  it  follows  that  the  reduction  is 
effected  not  only  by  carbon  monoxide,  but  also  by  carbon.  The  fear  of  loss  of  heat  in 
the  carbon-reduction  as  compared  with  the  oxide-reduction  has  been  the  cause  that 
the  consumption  of  coal  is  now  in  that  case  less  than  it  ever  could  have  been  in  oxide 
reduction.  The  lost  heat  is  substituted  by  hotter  air  from  the  blast,  whereby  the  crude 
iron  is  rendered  again  poorer  in  carbon  and  richer  also  in  silicon  by  overheating  in  the 
moulds. 

The  consumption  of  fuel  can  scarcely  be  reduced  lower  in  many  cases.  Fuel  could 
be  further  economised  only  by  very  hot  air  from  the  blast,  with  a  simultaneous  intro- 
duction of  carbon  monoxide ;  but  this  gas  would  have  to  be  produced  more  cheaply 
than  in  the  blast  furnace  itself.  The  oxide  gas  must  thereby  not  be  mixed  with 
hydrogen,  as  Bell  proposes,  since  this  chiefly  promotes  reduction  by  carbon,  to  which 
the  supply  of  oxide  gas  would  act  antagonistically. 


SECT.    II.]  IRON.  121 

The  following  calculation  shows  the  average  heat  required  for  smelting  crude  iron 
in  charcoal  furnaces.  For  comparison  there  are  also  given  the  corresponding  values 
which  express  the  consumption  of  heat  in  smelting  100  kilos,  of  coke  iron : — 


Consumption  of  Heat  for — 


Swedish 

Charcoal  Furnaces, 
heat-units. 


Evaporation  of  moisture  of  fuel 8,155 

Reduction  of  iron  from  ore 158,805 


Saturation  of  reduced  iron  with  carbon 
Expulsion  of  carbonic  acid  from  limestone 
Its  decomposition  by  carbon 
Decomposition  of  moisture  of  air 

„  of  phosphoric  acid  and  silica 

Fusing  crude  iron 

,,      slag 

Heat  escaping  through  masonry,  estimated 
Absorption  by  refrigerating  water 
Escape  of  heat  in  gases  at  mouth 


9,600 

7,105 

7,36o 

6,800 

2,610 

33,000 

41,35° 

12,715 

5-545 

34,565 


Cleveland 

Coke  Furnaces. 

heat-units. 

I,62O 
165,540 

7,20O 
20,065 
2O,8oo 
I2,2OO 
20,870 

33,000 
72,600 
18,290 
9,090 
37,7io 


Total  heat-units  required 327,610 

Heat  evolved,  calculated  according  to  composition,  weight, 
and  temperature  of  fuel  of  escaping  gases  and  of  air      .    318,175 


419,005 


423,860 


Hence  fully  30  per  cent,  more  heat  is  required  for  smelting  Cleveland  irons  than 
for  the  richer  haematites  and  magnetites  of  Sweden.  The  consumption  of  materials  for 
100  kilos,  crude  iron  was  as  follows  : — 


Fuel 

Limestone 

Ore 

Temperature  of  blast 

„  of  escaping  gases 


Sweden. 
97  -4  kilos. 
I9-2      „ 
197-8      „ 


211 
28Q 


Cleveland. 
IO2'O  kilos. 

46.9     » 
2347      .. 
5630 
262 


It  is  known  that  the  ore  is  the  source  of  the  oxygen  which  converts  carbon  mon- 
oxide into  carbon  dioxide.  In  addition  to  the  carbon  dioxide  thus  formed,  a  certain 
quantity  is  contributed  by  the  limestone,  and  a  further  portion  by  the  dissociation  of 
the  carbon  monoxide,  since  two  equivalents  of  this  gas  are  resolved  into  carbon  dioxide 
and  carbon  within  the  pores  of  the  ore  undergoing  reduction.  But  as  soon  as  the 
carbonic  acid  exceeds  a  certain  proportion,  there  sets  in — the  temperature  and  other 
circumstances  permitting — an  opposite  reaction :  carbonic  oxide  is  formed  by  the  carbon 
of  the  fuel. 

The  gases  of  the  Cleveland  blast  furnaces,  those  especially  of  23  to  24  metres  in 
height,  are  notable  for  the  small  quantity  of  carbonic  acid  contained  in  them  below  a 
certain  depth.  The  following  examples  illustrate  this  proposition  for  a  furnace  of  the 
capacity  of  496  cubic  metres — 


Beneath  the  Mouth. 

No.  I. 

No.  II. 

CO,. 

CO. 

CO2. 

CO. 

5  metres    

2'22 
0-67 
I'09 

i'S« 

0-50 

O'OO 

0-81 

34-08 
35'" 
3496 
35  '24 
35  '92 
36-63 
3770 

2*25 

073 
I  '00 

0-49 

O'OO 

073 

33-31 
34-84 
35-08 

36-03 
37-60 

37-86 

16       

21'5      , 

A  charcoal  blast  furnace  of  15-95  metres  in  height  and  101  cubic  metres  capacity 
.gave,  in  the  average  of  two  determinations — 


122 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


coa.  co. 

3 "4  metres  below  mouth       .....     16*39  •••  13*1 1 

5'2      „               „                  17-80  ...  10-89 

7-0      „               „                  9-60  ...  21-59 

8-2      „               „                  2-68  ...  30-66 

10-4      „                „                  ii'6o  ...  20-06 

Various  samples  of  flue  dust  had  the  following  composition  : — 


KO. 

NaO. 

CaO. 

MgO. 

Fe20s- 

MnO. 

ZnO. 

PbO. 

Si02. 

A1203. 

8.         ZnS. 

Gleiwitz     . 

.     12-28 

12-58 

6-15 

5-87 

9'5° 

0-3I 

25-SI 

1373 

1772 

3-94 

O'24        — 

Tarnowitz  . 

— 

— 

— 

— 

— 

— 

35-65 

10-64 

I5-55 

4-21 

—            — 

? 

.     17-05 

9'53 

2S-95 

2-31 

O'9I 

0'37 

I-30 

— 

24-05 

10-90 

171         — 

Cleveland  . 

— 

4-70 

12-30 

5-03 

14-22 

— 

10-48 

— 

22'6O 

8.20 

0-17      1370 

The  proportion  of  cyanogen  compounds  in  the  gases  and  the  dust  deserves  notice. 
According  to  the  views  of  Berthelot,  there  is  first  formed  in  the  blast  furnace  potassium 
acetylide,  C,K,,  which  then  combines  directly  with  nitrogen  to  potassium  cyanide, 
2(CNK).  How  considerable  may  be  the  production  of  metallic  cyanides  in  blast 
furnaces  worked  with  coal  appears  from  an  investigation  by  Bunsen  and  Playfair  on 
the  English  manufacture  of  crude  iron,  according  to  which  112*5  kilos,  of  potassium 
cyanide  were  produced  daily  in  a  blast  furnace.  According  to  Bell,  the  following 
quantities  of  potassium  and  sodium  were  found  in  combination  with  carbon  dioxide, 
oxygen,  or  cyanogen  in  i  cubic  metre  of  the  gases  of  a  Cleveland  coke-blast  furnace  of 
495  cubic  metres  capacity,  and  a  height  of  24*4  metres.  The  gases  were  drawn  on  six 
successive  days  at  the  height  of  2^44  metres  above  the  hearth  : — 


Potassium  and  sodium 
Cyanogen    . 


I. 

46-49 
19-00 


II. 

30-17 
12-93 


III. 

33-I5 
17-32 


IV. 

21-09 


V. 

31-65 

2C'6l 


VI. 

11.83 

9-16 


Average. 
29.11  gramme 
15-06      „ 


On  the  same  days  the  escaping  gases  contained  : — 

Potassium  and  sodium       .     12-20        15*30          6*68          5-89          4*29  9-07      „ 

Cyanogen.        .        ,        .      4-00          6-60          3-57          2-91          1-79  377      „ 

Slags. — The  composition  of  the  slag  is,  to  an  experienced  eye,  an  important  indica- 
tion of  the  working  of  the  furnace.  The  composition  is,  of  course,  widely  different — 
e.g. :— 


Mariazell 
(Styria). 

Scotch. 

Granular. 

Vitreous. 

Silica     
Alumina        
Manganous  oxide  

43-850 
4-650 
2'6lO 

0-540 
0-850 

23-300 

22-700 
0-480 
0-050 

I'OIO 

0-009 

57-95 
21-96 

0-37 
0-05 

16-24 
0'43 

3-00 

5271 
21-44 
0*64 
0-36 

19-13 
370 

2  -O2 

Magnesia 
Potash  . 
Soda 
Calcium  sulphide 
Phosphoric  acid 

The  crude  grey  iron  from  Mariazell,  in  Styria,  belonging  to  the  first  slag  contained : — 

Carbon   .        .        .        .        .        .        .  0-354 

Graphite         . 2-837 

Silicon 2-953 

Sulphur 0-018 

Phosphorus 0-045 

Copper 0-220 

Cobalt  and  nickel 0-013 

Manganese 2.980 


SECT,  ii.]  IRON.  123, 

The  blast  furnace  works  of  Ougre"e  exhibited  at  Antwerp  the  following  analyses  of 
slags,  together  with  the  accompanying  kinds  of  iron  : — 


White 
Iron. 

Spiegel. 

Spiegel 
Bessemer. 

Semi- 
Bessemer. 

Bessemer. 

Bessemer, 
Extra. 

Thomas. 

Crude  Iron 
for 
Castings. 

Crude  Irons. 

Grey, 

Nucleus 

Great 

Radiating 

— 

— 

Coarse, 
with 
Spiegel. 

Fine 
Grain. 

Coarse, 
Exterior 
Fine. 

Separa- 
tion of 
Graphite. 

Specular, 
Grey 
Points. 

Strong 
Grey. 

Carbon 

4-400 

5-800 

5'ioo 

4"OOO 

4-500 

4-500 

4^25 

3-987 

Silicon 

0*409 

0-503 

1-127 

l'I21 

2-463 

2-845 

0-807 

1-307 

Manganese 

0-131 

7-232 

4-213 

2-988 

2*042 

0-9-0-4 

1-820 

0-407 

Sulphur 

0-329 

O'OOO 

trace 

trace 

O-OI4 

O'OIO 

0-054 

0-056 

Phosphorus 

1-528 

0-892 

0-223 

0-093 

0-060 

0-048 

2-344  ? 

0-157 

Slags. 

Dark 
Brown, 
Firm. 

Light 
Green. 

Light 
Grey, 
Firm. 

Light 
Grey. 

Light 
Crumb- 
ling. 

Crumb- 
ling. 

- 

Chiefly 
Crumb- 
ling. 

Silicon 

3435 

32-25 

33-io 

34-00 

32-21 

30-00 

32-97 

35-50 

Alumina     . 

14-66 

11-17 

10-33 

979 

11-57 

12-34 

12-44 

8-72 

Lime  . 

42-66 

46-20 

49-70 

47-00 

50-42 

5I-00 

47-95 

46-50 

Magnesia    . 

2'OO 

2  -O2 

i-34 

3  "30 

I'37 

2'34 

1-37 

3  -20 

Manganous  oxide 

0-92 

5-07 

2-04 

2-32 

0-85 

0-30 

2-26 

1-58 

Ferrous  oxide 

3  '30 

o'6o 

0-67 

0-65 

0-76 

1-05 

1-47 

1-16' 

Sulphur 

1-42 

2*52 

2-69 

I  -80 

272 

273 

1-42 

1-64 

Phosphorus 

0*14 

0'02 

0-03 

O'OI 

O'OI 

0-O2 

0-08 

O'O2 

Blast  furnace  slags  are  used  for  the  preparation  of  artificial  stone,  for  road-making, 
as  a  material  for  cement,  for  bottle-glass,  for  enamelling,  for  manures.*  Slags,  if  not 
basic,  are  also  used  for  the  manufacture  of  aluminous  products.t 

Crude  Iron. — The  iron  run  off  from  the  blast  furnace  contains  carbon  (both  free,  as 
graphite,  and  in  combination,  as  iron  carbide),  silicon,  sulphur,  phosphorus,  manganese, 
&c.  According  to  the  nature  of  the  carbon,  it  is  distinguished  as  white  and  grey  crude 
iron. 

The  white  iron  is  distinguished  by  its  silvery  white  colour,  hardness,  brittleness, 
brightness,  and  high  specific  gravity  (7-58  to  7-68).  Its  carbon  is  in  a  state  of  chemical 
combination.  Sometimes  it  displays  prisms,  and  is  then  known  as  spiegel-eisen,  which 
is  obtained  from  manganif erous  iron  spar.  It  may  contain  from  4  to  1 5  per  cent,  of 
manganese.  In  the  production  of  steel  from  such  spiegel-eisen  the  manganese  protects 
the  carbon  against  too  rapid  combustion. 

Grey  crude  iron  varies  in  colour  from  a  light  grey  to  a  deep  blackish  grey,  and  is  of 
a  granular  or  scaly  texture.  It  is  softer  than  white  iron  and  more  fusible.  It  contains 
much  graphite  and  little  carbon  in  chemical  combination.  It  is  used  for  castings,  as  it 
fills  the  moulds  more  sharply  and  cleanly  than  white  iron,  which  hardens  with  blunt 
extremities  and  a  concave  surface.  White  (especially  manganiferous)  crude  iron  is 
particularly  suited  for  the  preparation  of  bar  iron  and  steel  (Bessemer  steel). 

The  character  of  crude  iron  depends  not  merely  on  the  charge,  but  on  the  tempera- 
ture of  the  furnace  and  the  way  of  working.  White  iron  seems  to  be  first  formed  in 
the  furnace,  and  to  pass  into  grey  iron  at  a  very  high  temperature.  If  ore  additions 
(fluxes,  &c.)  and  fuel  are  duly  proportioned,  the  product  is  chiefly  white  iron,  and  the 
slag  is  never  dark.  If  the  fuel  is  deficient,  much  ferrous  oxide  passes  into  the  slag, 
and  gives  it  a  dark  colour.  If  there  is  an  excess  of  fuel,  grey  iron  is  produced. 

*  This  use  is  practicable  only  with  the  basic  slags  of  the  Thomas  and  Gilchrist  process,  which 
are  very  rich  in  phosphates. 

t  E.g.,  crude  aluminium  chloride  for  the  treatment  of  sewage.  See  J.  W.  Slater's  process, 
patent  No.  12,830,  A.D.  1884.  It  has  been  proposed  to  make  bricks  of  slag,  but  houses,  &c.,  built 
of  such  material  never  become  dry,  as  there  is  no  interchange  of  air  through  the  walls. 


124 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


(2)  Examination  of  Iron  and  Steel. 

The  most  important  points  to  be  determined  are  the  quantities  of  carbon,  silicon, 
phosphorus,  sulphur,  manganese ;  secondarily,  those  of  tungsten  and  titanium.  The 
microscopic  examination  is  acquiring  importance.* 

In  determining  total  carbon  in  iron  according  to  Wohler's  process  (heating  the 
sample  in  a  current  of  chlorine,  and  burning  the  residue  for  converting  the  carbon  into 
carbon  dioxide),  we  obtain,  according  to  Gintl,  defective  values,  as  it  is  not  possible  by 
ordinary  means  to  obtain  a  current  of  chlorine  absolutely  free  from  oxygen,  perhaps  in 
consequence  of  the  formation  of  oxides  of  chlorine  obtained  during  the  action  of  hydro- 
chloric acid  upon  manganese  peroxide.  This  error  is  avoided  by  passing  the  current  of 
chlorine  (freed  from  hydrochloric  acid  and  watery  vapour  by  washing  and  careful 
drying)  over  a  stratum  of  fragments  of  charcoal  of  about  the  size  of  lentils,  about 
10  centimetres  in  length,  and  kept  at  a  red  heat.  The  charcoal  must  have  been 
previously  ignited  in  chlorine.  The  gas  so  purified  is  then  allowed  to  act  upon  the  iron, 
which  must  be  used  as  borings.  Ullgren  oxidises  the  carbon  by  means  of  chromic  acid, 
and  weighs  the  carbonic  acid  produced ;  Wiborgh  determines  it  volumetrically. 

For  determining  the  carbon  present  as  graphite  the  sample  is  generally  dissolved  in 
dilute  hydrochloric  acid  in  the  absence  of  air,  when  the  residual  carbon  is  washed  out 
and  weighed.  The  combined  carbon  appears  as  a  residue.  Eggertz  determines  com- 
bined carbon  by  dissolving  the  sample  in  nitric  acid  and  comparing  the  solution  with 
known  standards.  The  process  is  adapted  for  checking  work. 

For  determining  sulphur  the  sample  is  dissolved  in  nitric  acid,  and  the  sulphuric 
acid  formed  is  precipitated  with  barium  chloride.  Less  accurate  are  the  processes  in 
which  the  sample  is  dissolved  in  hydrochloric  acid ;  the  sulphur  being  driven  off  as 
hydrogen  sulphide  and  conducted  into  metallic  solutions. 

For  determining  silicon  5  grammes  of  the  sample  are  dissolved  in  nitric  acid  or 
bromiferous  hydrochloric  acid,  or  in  sulphuric  acid  with  potassium  chlorate ;  it  is  then 
evaporated  to  dryness,  moistened  with  hydrochloric  acid,  dissolved,  and  the  silica  is 
filtered  off. 

For  determining  phosphorus  the  sample  is  dissolved  in  nitric  acid,  evaporated  to 
dryness,  slightly  ignited,  re-dissolved ;  the  phosphoric  acid  is  precipitated  with  molybdic 
acid,  the  precipitate  dissolved  in  ammonia  and  reprecipitated  with  magnesia  mixture. 

The  following  analyses  of  crude  iron  may  be  appended  : — 


n. 

TV 

. 

IV. 

. 

Graphite 
Combined  carbon 

0-086 

3-156 

1-347 

}  6-05 

Carbon 
Sulphur 

4-323 

0-014 

4-166 
0-035 

Phosphorus 

0-459 

0-842 

6-37 

Phosphorus 

0-059 

0-090 

Sulphur 

0-036 

1-267 

0-06 

Silicon 

0-997 

0-584 

Silicon 

3-265 

2-721 

2-41 

Manganese  . 

10-707 

5-920 

Manganese 

0-388 

2-401 

6-28 

Cobalt 

trace 

trace 

Aluminium 

0*028 

— 

0-08 

Nickel 

0-016 

- 

Chrome 

0-027 

Zinc    . 

Vanadium 

O'OI2 

Copper 

0-066 

0-046 

Copper 

0-OO9 

Lead   . 

Arsenic 

0-OI5 

Potassium  . 

0-063 

Antimony 

O'OII 

Aluminium 

0-077 

0-068 

Cobalt  and  nickel 

0-035 

Calcium 

0-091 

trace 

Zinc    . 

trace 

Magnesium 

0-045 

0-058 

Calcium 

0-072 

— 

0-46 

Titanium     . 

0.006 

Magnesium 

O'lOO 

— 

0*25 

Arsenic 

0-007 

0-032 

Titanium     . 

0-024 

Antimony    . 
Tin      . 

0-004  1 

0-026 

Nitrogen 

0*014 

Oxygen  (in  slag) 

0-665 

*  See  Select  Methods,  by  W.  Crookes,  F.K.S.,  pp.  145-195. 


SECT.    II.] 


IRON, 


I25 


I.  is  a  black  crude  iron,  according  to  Fresenius ;  II.  is  a  very  grey  crude  iron  from 
Gartsherrie ;  III.  grey  crude  iron  from  bog-ore  at  Helbo  (charcoal)  ;  IV.  Spiegel  iron, 
from  Lohe,  according  to  Fresenius ;  V.  Spiegel -eisen  from  St.  Louis. 

The  analysis  of  Gleiwitz  coke  iron  has  given  the  following  results  :— 


Spiegel,  crude  . 

White 

Finely  granular 

Coarse 


c. 

Si. 

S. 

p. 

Mn. 

3-35 

...   0-317   ... 

0-030      . 

1-29 

...     3-60 

5'49 

...    0800 

O'OIO      . 

..    0-28 

•••     373 

3-20 

I'2IO      ... 

0-114     . 

,.     0-81 

...     1-70 

4-38 

...      2'O2O      ... 

0-118    . 

.  .    0-90 

...     1-65 

(3)  Iron  Founding. 


Fig. 


Although  iron  can  be  cast  direct  from  the  blast-furnace  it  is  generally  preferred 
to  re-melt  the  pigs ;  this  is  effected  either  in  crucibles  in  shaft-  or  cupola  - 
furnaces,  or  in  reverberatories.  The 
cupola-furnaces  are  by  far  the  most 
generally  used,  the  preference  being 
given  in  Germany  to  the  design  pro- 
posed by  Krigar.  The  cylindrical 
shaft,  a  (Fig.  131),  has  a  short  cham- 
ber, b  ;  the  compressed  air  issues  from 
the  ring-shaped  channel,  d,  through 
slits,  f ,  into  the  melting-box,  c,  e.  The 
melted  iron  collects  in  the  fore-hearth, 
g,  from  which  the  slag  can  flow  off  at 
s  or  t.  The  door,  o,  lined  with  fire- 
clay, is  provided  with  an  aperture 
above  the  out- flow  channel,  p.  At  q 
there  is  an  eye-hole,  and  at  r  an  open- 
ing for  cleaning  the  slits.  The  lower 
part  of  the  furnace  is,  with  the  sheet- 
metal  screen,  h,  and  stands  on  the 
ribbed  cast-iron  plate,  k,  which  lies  on 
the  iron  pillars,  m.  When  the  melt 
is  complete,  the  last  residues  are  re- 
moved through  the  trap  door,  n.  In 
the  cupola-furnaces  of  Greiner  and 
Erpf  the  air  enters  through  different 
rows  of  tuyeres  to  burn  the  carbon 
monoxide. 

The  author  found  on  examining 
Krigar  furnaces  that  the  ratio  C03 : 
CO  in  the  escaping  gases  is  now  2  to 
3,  whilst  it  was  formerly  about  0*8  ;  the  Consumption  of  coke  per  100  kilos,  iron  is  now 
reduced  from  20  to  6  kilos.  The  sulphur  escapes  partly  in  the  gases,  and  in  part,  if 
sufficient  lime  is  present,  it  enters  the  slags,  as  the  following  analyses  show  : — 


126 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Slags  from 
Former 
Times. 

Slags  from  Hannoverian 
Cupolas. 

From 
Spiegel. 

Slags  from  Irons  for  Basic 
Process. 

HO, 

60-05 

5604 

SS'oi 

50-48 

36-56 

37-05 

42-08 

52-96 

Al,63 

lS-00 

H-55 

11-61 

10-68 

H-57 

II-08 

10-81 

1  2  -80 

Fe203 

— 

— 

— 

— 

0-85 

1-25 

FeO 

4-61 

IS'34 

14-91 

20-98 

078 

1-59 

6-28 

4-36 

MnO 

8-29 

4'02 

I  -06 

4-01 

19-80 

14-09 

5-66 

4-3I 

CaO 

6-29 

9'74 

I5-05 

9-85 

28-97 

29-64 

29-50 

19-63 

MgO 

0-25 

0-51 

0-49 

0-84 

1-92 

20-79 

3-65 

.       2'12 

Ca   . 

}      0-41 

O'2I 

0-28 

O'22 



1-98 

) 

S      . 

)       0-33 

O'I7 

O'22 

0-18 

0-40 

1-58 

0-48 

1    0-47 

PA 

— 

— 

— 

0-04 

O'lO 

I  '00 

O'H 

sos. 

— 

— 

— 

— 

0*05 

— 

0-04 

0-40 

The  iron  present  in  the  cupola  slag  is  derived  partly  from  the  ash  and  partly  from 
the  crude  iron ;  the  latter  is  the  more  strongly  oxidised  the  less  carbon  monoxide  is 
formed,  as  shown,  e,g.,  in  the  slags  of  the  Hannover  cupolas.  The  richer  the  crude  iron 
is  in  manganese  the  more  both  the  iron  and  the  silicon  are  protected  from  oxidation. 

The  changes  which  iron  undergoes  on  re-melting  in  the  cupola  were  examined  by 
Ledebur : — 


Q 

Si 

Pll 

P 

Pig    ... 

After  ist  smelting 
„     2nd      „ 
»     3rd       „ 
„     4th       „ 

4-I73 
3-586 
3-860 
3763 
3-686 

1-528 

1-447 
I-370 
I-378 
I'334 

2-084 
I'599 
1-399 
1-038 
0736 

0-079 
0-150 
0-080 
0-079 
0-079 

0-331 

0-475 

On  melting  pig-iron  with  lime  and  fluor-spar  Rollet  obtained : — 


] 

1 

I. 

I] 

I. 

Before 
Smelting. 

After 
Smelting. 

Before 
Smelting. 

After 
Smelting. 

Before 
Smelting. 

After 
Smelting. 

Ca 
Si         
Mn       
S  
P  

3-500 
0-900 
I-300 
O'220 
O"O7O 

3-500 
0-380 
0-815 
0-015 
OXK8 

2*900 

0-655 
traces 

0-375 

O'^O 

3-088 
0-060 
traces 
0-015 
O'o68 

2-550 
0-450 
traces 
0-520 
I  "Q"iO 

2  '800 
0'120 
traces 
0*040 
0*4.1  c 

Good  casting-iron  should  contain  as  much  carbon  as  possible,  in  the  form  of  graphite, 
and  be  consequently  very  coarse  in  grain  (generally  3  to  3-5  per  cent.)  ;  the  manganese 
should  be  low,  not  exceeding  0*75  per  cent.  A  high  proportion  of  silicon — at  least 
2  per  cent. — is,  according  to  Schmidt,  indispensable.  A  low  proportion  of  phosphorus 
is  advantageous,  and  i  per  cent,  is  the  utmost  limit.  For  castings  which  must  have 
great  absolute  strength  the  margin  lies  at  0*5  per  cent.  Sulphur  must  not  exceed 
<ro6  at  the  outside. 

Melting  in  a  reverberatory  furnace  has  the  advantage  that  the  iron  does  not  come 
in  contact  with  the  coke  or  its  ashes,  and  is  consequently  less  modified  than  in  the 
cupola.  On  account  of  the  high  temperature  required,  only  furnaces  with  a  storage  for 
heat  can  be  advantageous.  The  reverberatory  designed  by  Fr.  Siemens  has  a  round 
chamber  K  (Figs.  132  and  133),  with  a  vault  as  shown  by  dotted  lines.  To  the  furnace 
chamber  there  are  joined  two  pairs  of  gas  and  air  flues,  Fl  and  F3,  situate  high  up  in 
the  vault,  leading  down  in  such  a  manner  from  the  furnace  chamber,  K,  to  the  heat- 
storage  chamber,  R,  that  the  sides  of  the  hearth  are  freely  accessible.  The  chamber  is 
built  upon  pillars,  and  hence  the  furnace  is  accessible  also  from  below.  The  furnace  is 
provided  with  doors,  F,  for  introducing  the  metal  to  be  melted,  and  with  an  upper  and 
.a  lower  tap-hole,  Sl  and  Ss.  The  lower  hole,  Sa,  permits  of  the  entire  charge  being 


SECT.    II.] 


IRON. 


127 


drawn  off,  whilst  the  upper  tap-hole  serves  merely  to  draw  off  the  upper  portion  of  the 
melted  steel,  together  with  the  slag.     The  zone,  Z,  in  contact  with  the  slag,  is  without 

Fig.  132. 


Fig.  133- 

an  iron  coating,  and  is  hence  accessible  on  all  sides  and  can  be  repaired  even  during 
work. 

(4)  Wrought  or  Bar  Iron. 

As  already  mentioned,  wrought  iron  was  formerly  obtained  by  heating  the  ores 
•with  charcoal  upon  a  hearth  and  forging  out  the  spongy  iron  thus  produced.  This  so- 
called  "  direct  "  process  has  been  of  late  much  improved,  especially  by  Siemens,  who 
vised  firstly  a  rotatory  furnace  and  then  a  reverberatory  (Figs.  134  to  137).  The 
bottom  of  the  melting  chamber  forms  a  tank,  s,  to  collect  the  melted  metal,  and  one 
side  is  a  sloping  hearth,  /,  upon  which  the  mixture  of  ore,  coal,  and  fluxes  to  be  smelted 
moves  downwards.  For  the  convenient  introduction  of  this  mixture,  a  slit,  o,  is  left 
free  in  the  vault  above  the  sloping  hearth,  and  above  it  a  space  is  set  off,  in  which  a 
large  quantity  of  the  mixture  can  be  collected  and  sink  gradually  down  through  the 
slit  as  the  charge  already  upon  the  hearth  melts  away.  The  tank,  s,  is  fitted  at 
different  heights  with  three  tap-holes  Z,  Z^  and  Zv  the  upper  one  being  permanently 
open  and  serving  for  the  continued  removal  of  the  slag,  Z,  is  the  general  tap-hole  for 
running  off  the  melted  iron  from  time  to  time,  whilst  the  lowest  hole,  Zv  is  used  only 


128 


CHEMICAL  TECHNOLOGY. 


[SECT. 


if  the  furnace  is  to  be  completely  emptied.  Thus,  a  part  of  the  iron-bath  remains  in 
the  furnace,  so  that  the  slag  never  touches  the  bottom  of  the  tank,  and  the  iron,  which 
is  constantly  being  formed  in  the  shape  of  fine  globules,  can  sink  down  in  the  mass  of 
metal  upon  the  hearth.  In  order  to  render  the  slag  suitably  mobile  and  to  remove 
impurities  from  the  iron,  lime,  and  potassium  and  sodium  salts  are  added  to  the 


Fig.  134- 


Fig.  135- 


Fig.  136 


j^xpu 

FIG.  134. — Schnitt  =  Section  A,  B,  a,  b. 
FIG.  135. — Schnitt  —  Section  C,  D,  E,  F. 


Explanation  of  Terms. 

a.  b.  FIG.  136.—  Schnitt  =  Section  G,  H",  I,  K,L,  M. 

FIG.  137.— Schnitt  =  Section  N,  O,  P,  Q. 

mixture,  inot  generally,  but  under  certain  circumstances.    The  addition  of  such  salts" 
renders  the  slag  more  fit  for  the  glass  manufacture. 

Opinions  on  the  value  of  the  direct  processes  are  very  varied.  Ledebur  considers 
them  as  unpromising.  Westmann  contests  this  view  if  the  ores  used  contain  at  least 
50  per  cent  of  iron.  For  obtaining  pig-iron,  the  following  quantities  of  heat  are 
needful : — 

For  reducing  ores        .        .        .        .  .        .         .     1588 

„   expelling  H2O  and  CO._, 158 

„   reducing  SiCX,  and  P..O.J 29 

„   smelting  iron  and  slags 774 

To  which  come  further  for  O  '0428  kilo,  carbon  taken  up 

by  the  crude  iron 173 

Heat-units 2722 

In  the  production  of  spongy  iron  the  following  items  are  dispensed  with  : — 

For  expelling  H30  from  fuel 82 

„   carbon  taken  up  by  crude  metal 173 

„   reduction  of  SiO,  and  P..O5 29 

„   half  heat  expended  in  smelting     .        .        .        .        .  372 


Heat-units 


656  =  24  % 


SECT,  ii.]  IRON.  129, 

By  far  the  largest  quantity  of  bar-iron  is  prepared  from  crude  iron. 

Refining  Process. — This  process  depends  on  the  removal  by  oxidation  of  the  bulk  of 
the  carbon  and  the  other  foreign  matters,  especially  silicon,  from  crude  iron.  Only 
white  pig  is  used,  as  poor  as  possible  in  carbon,  since  before  smelting  it  softens,  remains 
for  a  long  time  as  a  thin  liquid,  and  hence  presents  a  larger  surface  to  the  oxidising 
agents.  Its  combined  carbon  burns  more  readily  than  the  graphite  of  grey  pig.  This 
process  may  be  effected  either  (i)  on  a  hearth  (sometimes  called  the  German  pro- 
cess), (2)  in  reverberatories  (the  puddling  process),  or  (3)  by  forcing  air  into  the 
melted  crude  iron  (the  Bessemer  process). 

In  the  hearth-refining  process,  white  pig  is  melted  in  the  four-sided,  depressed  fire- 
space,  «,  of  the  hearth,  b  (Fig.  138),  in  such  a  manner  that  it  is  not  exposed  to  the 
blast  until  it  is  liquefied.     The  depression  is  lined  with  iron  plates  and  receives  the 
necessary  current  of  air  through  the 
pipe,  c.     The  fire-box  is  first  filled  with 
glowing  charcoal,  the  blast  is  turned 
on,  and   the    iron   is    laid    upon   the 
hearth   and    pushed    down   into   the 
depression    as    it    melts   off    at    the 
end. 

The  air  of  the  blast  constantly 
burns  the  carbon  of  the  crude  iron  to 
carbonic  acid,  and  thus  effects  its  de- 
carbonisation.  The  sand  adhering  to  the  pigs,  the  silica  formed  by  the  oxidation  of 
their  silicon  and  that  introduced  by  the  ash  of  the  charcoal,  combine  with  the  ferrous 
oxide  simultaneously  formed  to  bisilicate,  FeSi03,  the  so-called  "crude-slag"  (68'8 
per  cent,  ferrous  oxide  and  31*2  silica)  which  floats  above  the  melted  iron  and  is 
run  off  from  time  to  time,  though  the  iron  is  never  left  quite  uncovered.  This  slag, 
mixed  with  anvil-dross  (ferroso-ferric  oxide),  is  used  for  the  next  operation  to  decarbonise 
the  iron.  In  fining,  all  the  other  foreign  matters  contained  in  the  iron,  such  as  phos- 
phorus, &c.,  pass  into  the  slag  in  the  state  of  phosphoric  acid,  &c.  After  the  iron 
is  melted  the  slag  is  drawn  off,  and  the  pieces  of  iron  are  exposed  to  the  blast 
whilst  being  frequently  turned.  The  slag  now  being  formed  becomes  the  richer 
in  ferrous  oxide  as  the  metal  becomes  purer,  and  contains  73-7  per  cent,  ferrous 
oxide  and  21*4  silicic  acid.  It  is  never  crystalline,  but  compact,  of  a  dark  grey  colour, 
and  of  a  higher  specific  gravity  than  the  crude  slag.  The  whole  mass  of  iron  is  made 
semi-fluid  by  an  increase  of  the  temperature  to  promote  the  separation  of  the  slag. 
The  fined  lump  (ball  or  bloom)  is  lifted  out  of  the  fire  and  brought  under  the  lift- 
hammer.  By  its  blows  all  particles  of  slag  are  forced  out.  The  bloom  is  then  cut 
into  pieces,  which  are  forged  into  bars.  From  100  parts  of  pig  iron  there  are  obtained 
on  the  average  70  to  75  parts  of  bar  iron. 

The  Swedish  fining  process  acts  at  once  upon  small  portions  of  iron  only.  The 
decarbonisatioii  is  effected  by  the  oxygen  of  the  air.  Much  fuel  is  consumed,  and  a 
not  inconsiderable  part  of  the  iron  is  oxidised,  but  the  iron  obtained  contains  no  slag, 
and  is  more  compact. 

The  puddling  process  is,  in  fact,  fining  in  a  reverberatory  furnace.  In  countries 
where  charcoal  cannot  be  used  for  fining  crude  iron  on  account  of  its  high  price,  coal  is 
used.  As  the  immediate  contact  of  coal  with  the  iron  must  be  avoided  on  account  of 
the  sulphur  which  it  contains,  reverberatory  or  puddling  furnaces  are  used  for  effecting 
the  elimination  of  the  carbon.  This  is  effected  by  agitation,  either  by  hand  or  by 
machinery,  or  by  means  of  a  revolving  hearth.  Thus  we  have  hand  puddling,  machine 
puddling,  and  rotatory  puddling. 

Preparatory  to  the  puddling  process  is  the  refining,  by  which  the  free  carbon  is 


130 


CHEMICAL  TECHNOLOGY. 


[SECT.  n. 


brought  into  the  combined  state  and  the  silicon  is  burnt.     This  refining  consists  in 
re-melting  upon  a  bed  of  coke  under  the  action  of  a  blast.     A  grey  pig-iron  contained  — 


Before  Refining.        After  Refining. 


Carbon 

Silicon 

Sulphur 

Phosphorus 

Manganese 


ro 

o'5 
07 

O'2 


0'2O 

0x15 


Fig.  139- 


Hence  it  appears  that  the  proportion  of  carbon  in  crude  iron  is  not  reduced  by 
refining,  but  the  silicon  is  chiefly  removed. 

A  puddling  furnace  is  shown  in  front  elevation  in  Fig.  139,  and  in  Fig.  140  in 

section.  The  hearth,  A,  is  a  rect- 
angular iron  chest,  into  which  air 
can  stream  in  freely  through  the 
grate,  F.  Upon  this  hearth  there 
is  placed  a  layer  of  refining  slag, 
to  which  forge  scales  have  been 
added,  and  the  mass  is  heated 
until  its  surface  is  softened.  The 
pig-iron  to  be  treated  is  heated 
until  it  is  soft,  spread  about  over 
the  surface  of  the  hearth  by 
means  of  a  stirrer,  and  heated 
with  constant  agitation  (pud- 
dling). The  working  door,  D,  can 
be  easily  opened  and  closed.  There 
appear  small  blue  flames  of  carbon 
monoxide  upon  the  pasty  iron,  and 
the  metal  becomes  stiffer  and 
tougher.  The  greater  part  of  the  slag 
formed  during  puddling  flows  away  from 
the  iron  to  the  front  of  the  furnace,  down 
the  inclined  plane,  B,  and  it  is  let  off 
through  an  opening  from  time  to  time. 
When  the  puddling  is  completed  the  iron 
spread  out  on  the  hearth  is  collected  into 
balls  arid  freed  from  slag  by  the  hammer. 
By  the  access  of  the  air  or  of  oxy- 
genous fire-gases  to  the  molten  crude  iron 
upon  the  hearth  of  the  reverberatory,  there  is  formed  ferroso-ferric  oxide,  the  oxygen 
of  which  removes  the  carbon  of  the  crude  iron  in  the  form  of  carbon  monoxide,  which 
burns  with  a  blue  flame.  As  the  mass  is  decarbonised  it  becomes  less  fusible,  and 
there  are  formed  in  its  interior  solid  masses  of  wrought  iron,  which  increase  in  quantity 
and  which  are  collected  with  the  stirrer  and  slightly  welded  together.  In  practice  the 
process  is  not  so  simple,  because  (i)  it  is  not  possible  to  bring  all  the  ferroso-ferric  oxide 
in  contact  with  the  carboniferous  iron,  so  that  oxide  is  easily  left  in  the  iron  and  prevents 
the  coherence  of  its  parts.  To  remove  this  superfluous  oxide,  crude  slag  is  added, 
which  is  converted  into  refinery  slag.  The  elimination  of  the  oxide  involves  a  loss  of 
iron  of  4  to  5  per  cent.,  to  which  must  be  added  5  per  cent,  more  by  the  combustion 
of  the  carbon  ;  (2)  another  difficulty  arises  from  the  presence  of  blast-furnace  slag,  and 
of  mechanically  adhering  silica,  &c.  During  puddling  the  free  silica  unites  with  the  blast- 
furnace slag;  if  this  comes  in  contact  with  the  ferroso-ferric  oxide  with  deficient 


Fig.  140. 


SECT.    II.] 


IRON. 


carbon,  it  gives  its  silica  partially  to  the  ferroso-ferric  oxide,  forming  with  it  a  refinery 
slag,  which  adheres  to  the  walls  and  the  sole  of  the  furnace,  and  a  basic,  very  infusible 
blast-furnace  slag,  which  remains  mixed  with  the  iron.  The  puddling  process,  as  at 
present  carried  out,  is  quite  unable  to  remove  this  slag.  Recent  studies  of  irons  and 
slags  in  the  various  stages  of  the  puddling  process  have  proved  that,  in  puddling,  the 
oxidation  of  the  combined  carbon,  silicon,  sulphur,  manganese,  and  iron,  is  effected 
much  more  by  the  combined  oxygen  of  the  slag  and  the  fluxes  than  by  the  free  oxygen 
of  the  air,  which  is  especially  active  only  at  the  period  of  melting.  In  the  first  portion 
of  time  after  melting,  the  iron  re-dissolves  the  non-combined  carbon.  Hence,  the 
silicon  is  separated  as  silica,  the  proportion  of  combined  carbon  increases,  and  the 
graphite  diminishes.  At  the  same  time,  much  of  the  manganese  is  oxidised.  After 
this  fining  process  is  completed  the  boiling  period  sets  in,  with  separation  of  carbon  and 
partial  reduction  of  iron,  when  the  particles  of  iron  separated  are  in  the  state  of  steel. 
In  the  third  period,  soft  iron  is  formed  with  further  decarbonisation,  when  the  bulk  of 
the  phosphorus  is  separated  out  as  iron  phosphide  and  ferric  phosphate,  and  passes 
into  the  slag. 

Iron  which  contains  too  much  phosphorus  is  purified  by  adding,  during  puddling, 
the  so-called  "  Schafhautel's  mixture  "  (manganese,  common  salt,  and  clay).  According 
to  Richter,  litharge  is  better  than  manganese  for  oxidising  the  sulphur  in  crude  iron. 
Superheated  steam  has  also  been  proposed  for  the  removal  of  sulphur.  The  volatilisa- 
tion of  sulphur  and  phosphorus  has  also  been  attempted  by  the  addition  of  fluor-spar 
(Henderson's  process),  and  of  iodine  compounds  such  as  potassium  iodide.  Others  add 
soda. 

The  tendency  to  displace  manual  labour  more  and  more  led,  firstly,  to  the  con- 
struction of  the  mechanical  puddler,  and,  as  the  results  were  not  completely  satisfac- 
tory, to  the  invention  of  rotatory  puddling  furnaces,  among  which  that  of  Danks 
(Fig.  141)  deserves  notice.  The  furnace,  A,  has  a  grate  apparently  similar  to  the 
'Common  puddling  furnace,  but  the  necessary 
air  is  admitted  also  by  a  row  of  tuyeres, 
placed  above  the  grate.  The  rotatory 
hearth,  B,  consists  of  cast-iron  segments, 
lined  within  with  a  mixture  of  iron-ore  and 
bauxite.  The  rotatory  hearth  has  a  two- 
fold arrangement  supporting  two  rails  for 
the  rollers  upon  which  the  apparatus  rests 
movably,  and  a  toothed  wheel,  E,  to  which 
the  motion  is  communicated  by  means  of  a 
small  engine.  Whilst  one  opening  of  the 
hearth  is  in  contact  with  the  furnace  bridge, 
the  other  serves  for  introducing  the  charge 
and  taking  out  the  finished  blooms. 

Bar-iron,  Wrought  or  Malleable  Iron,  has  a  light  grey  colour  and  a  granular  and 
jagged  fracture ;  its  specific  gravity  is  7'6o-7'9O,  that  of  chemically  pure  iron  being 
7  844.  Its  carbon  is  from  0-20  to  0-84  per  cent.,  traces  of  which  only  are  in  a  state 
of  mechanical  mixture. 

Chemical  examination  of  bar-iron  give  the  following  results — (i)  English  bars 
from  South  Wales,  (2)  soft  bars  from  Magdesprung  in  the  Harz,  (3)  Swedish  Danne- 


smora  iron : 


Iron  . 

Carbon 
Silicon 
Copper 
Phosphorus 


98-904 
0-411 
0-084 

0-041 


98-963 
0-400 
0-014 
0-303 


3- 

98775 
0-843 

0-118 
0-054 


1 32  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

Wrought  iron,  if  heated  to  redness  and  plunged  into  cold  water,  does  not  become 
harder  and  more  brittle,  and  can  still  be  forged.  It  is  much  softer  than  grey  or 
white  pig,  and  can  be  easily  filed,  cut,  planed,  &c.  It  is  far  less  fusible  than  crude 
iron ;  at  a  white  heat  it  becomes  so  soft  that  two  pieces  can  be  united  together  by 
hammering,  pressing,  or  rolling. 

Iron  shares  this  property  of  welding  with  platinum,  palladium,  potassium,  and 
sodium.  Iron  is  less  easily  welded  the  more  carbon  it  contains.  The  bar-iron 
obtained  by  fining  and  puddling  is  more  or  less  contaminated  with  foreign  matter. 
If  it  contains  sulphur,  arsenic,  and  much  copper,  it  is  red  short,  i.e.,  it  crumbles  under 
the  hammer  at  a  red  heat ;  silicon  renders  it  hard  and  brittle,  and  the  presence  of 
phosphorus  makes  it  cold-short,  i.e.,  it  can  be  worked  when  hot,  but  when  cold  it  breaks 
on  bending.  Calcium  renders  iron  incapable  of  being  welded.  Hard,  crystalline  sorts 
are  preferred  for  articles  which  have  to  resist  friction  and  take  a  permanent  polish. 
Tough,  stringy  irons  serve  for  parts  of  machinery,  for  chains  and  anchors,  &c. 

The  puddling  process  has  lost  much,  of  its  importance,  and  will  probably  be  entirely 
superseded  by  the  Siemens-Martin  and  the  Bessemer  processes,  both  of  which  produce 
steel  as  well  as  wrought  iron.  The  treatment  of  350  kilos,  of  iron  in  Danks'  furnace 
appears  feeble  in  comparison  with  the  manipulation  of  10,000  kilos,  in  the  Bessemer 
converter. 

STEEL. 

Steel. — This  substance  differs  from  crude  pig-iron  and  from  bar-iron  in  the  amount 
of  carbon  it  contains :  from  crude  iron,  moreover,  by  being  capable  of  welding  ;  and, 
again,  from  bar-iron,  by  being  comparatively  readily  fusible :  in  reference  to  the  amount 
of  carbon  present,  steel  holds  a  position  between  crude  pig-iron  and  bar-iron.  Recent 
researches  have  revealed  the  fact  that  steel  contains  nitrogen ;  but  whether  this  element 
really  contributes  to  the  peculiar  properties  of  steel  obtained  from  different  sources  is 
not  a  definitely  settled  point.  Steel  is  obtained  of  various  qualities  by  a  number  of 
processes,  as  will  be  seen  in  the  following  brief  reference — 

a.  Directly  from  iron  ores — 

1 .  By  the  reduction  of  iron  ores  directly  with  the  aid  of  fuel  (chiefly  charcoal), 

and  a  blast  on  the  hearth,  the  steel  being  obtained  in  the  form  of  lumps 
(so-called  natural  steel). 

2.  By  the  heating  of  certain  iron  ores  along  with  coal,  but  without  fusion 

(cementation  steel  from  ores). 

3.  By  the  fusion  of  iron  ores  along  with  charcoal  in  crucibles  (cast-steel  from 

ores). 

6.  By  the  partial  decarbonisation  of  pig-iron  (rough  steel,  furnace  steel,  or  German 
steel) — 

4.  By  the  refining  (partial  decarbonisation)  of  pig-iron  by  means  of  charcoal 

fuel  on  the  hearth  (sheer  steel). 

5.  By  treating  pig-iron  in  reverberatory  furnaces  fed  by  coal  or  blast-furnace 

gases  as  fuel  (puddled  steel). 

6.  By  forcing  air  through  molten  cast-iron  (Bessemer  steel). 

7.  By  heating  cast-iron  to  redness  along  with  substances  which  will  effect 

decarbonisation  below  the  fusion-point  of  the  metal ;  if  the  substances 
employed  for  partial  decarbonisation  are  iron  ores,  the  steel  is  called  iron 
ore  steel. 

8.  By   melting   crude   cast-iron   with  such   substances   as   those  just   men- 

tioned. 

9.  By  treating  crude  cast-iron  with  sodium  nitrate  (Heaton  steel,  Hargreave 

steel). 


BECT.  ii.]  STEEL.  133 

c.  By  imparting  carbon  to  bar  or  malleable  iron — 

10.  By  ignition  with    carbonaceous    matter,  but  without  fusion  (cementation 

steel). 

11.  By  fusion  with  charcoal  (cast  steel). 

d.  By  combination  of  methods  b  and  c,  as  in  fluxed  steel — « 

12.  By  melting  crude  pig-iron  and  malleable  iron  together. 

In  India  a  kind  of  steel  is  still  made  directly  from  iron  ores,  and  known  as  wootz 
(as  to  the  composition  of  this  substance,  see  the  Chemical  News,  vol.  xxii.  p.  46) ; 
it  is  possessed  of  excellent  qualities.  The  Japanese  also  understand  the  art  of  making 
steel  of  most  excellent  quality  by  rather  rough  and  primitive  means. 

According  to  the  degree  of  hardness  we  distinguish  mild  and  hard  steel,  and  accord- 
ing to  its  applications  tool  steel  and  machine  steel. 

The  finery  steel  obtained  by  the  partial  decarbonisation  of  crude  iron  may  be  either — 

(1)  Rough  Steel  or  Natural  Steel,  prepared  chiefly  from  the  "crude  steel-irons" — a 
crude  iron  prepared  from  iron  spar,  and  made  in  Styria,  Carniola,  Carinthia,  &c.,  also 
as  spiegeleisen,  generally  with  charcoal,  but  partly  with  coke.     Steel-fining  is  distin- 
guished from  iron-fining  chiefly  by  the  application  of  the  blast,  which  is  directed  so 
that  the  carbon  may  be  burnt  gradually,  and  the  workman  has  it  in  his  power  to 
interrupt  the  process  at  the  moment  when  the  steel  is  ready. 

(2)  Puddled  Steel. — Steel  may  be  produced   by  the  puddling  process  from  very 
different  kinds  of  ore,  and  is  furnished  very  cheaply  for  the  wheels  of  locomotives, 
railway  carriages,  and  other  large  and  heavy  objects. 

(3)  Bessemer  Steel. — The  pneumatic  process  invented  by  J.  Bessemer,  of  Sheffield,  in 
1856,  consists  in  forcing  into  liquid  crude  iron  (whether  direct  from  the  blast  furnace  or 
such  as  has  been  re-melted  in  cupola  or  reverberatory  furnaces)  a  strongly  compressed 
blast  of  air.     Without  the  addition  of  especial  fuel  a  sufficient  temperature  is  produced 
by  the  combustion  of  silicon,  manganese,  and  iron  to  maintain  the  process  and  form 
ferro-  silicate,  which  takes  up  f erroso-ferric  oxide,  and,  as  in  the  other  refining  processes, 
exerts  an  oxidising  action  upon  the  carbon  and  other  foreign  matter.     Phosphorus  is 
removed  only  by  the  basic  process  (Thomas  &  Gilchrist);  sulphur  to  a  small  extent 
only ;  copper,  nickel,  and  cobalt  not  at  all.     The  process  may  be  either  continued  until 
wrought  iron  is  formed  (which  may  then  be  converted  into  steel  by  the  addition  of 
spiegeleisen  or  ferro-manganese)  or  the  carbon  is  removed  only  to  the  degree  necessary 
to  form  steel. 

On  account  of  the  energetic  oxidation,  the  process  is  much  more  rapid  than  the 
fining  on  hearths  and  in  reverberatories,  and  during  the  oxidation  of  the  silicon  a  part 
of  the  carbon  is  burnt  off  also.  To  treat  10  tons  of  crude  iron  by  this  process  requires 
from  10  to  20  minutes,  whilst  to  puddle  the  same  weight  requires  three  days,  and  to 
convert  it  on  the  hearth  about  three  weeks. 

The  best  crude  iron  for  the  Bessemer  process  in  converters  with  an  acid  lining 
(quartz,  gannister)  is  a  grey  pig  containing  silicon  and  manganese,  but  as  little  phos- 
phorus and  manganese  as  possible.  On  forcing  in  strongly  compressed  air  into  this 
liquid  iron,  the  silicon  and  manganese,  along  with  some  iron,  burn  first,  and  yield  so 
high  a  temperature  that  it  suffices  to  keep  the  mass  liquid  during  the  remainder  of  the 
process.  The  presence  of  manganese,  which  is  oxidised  almost  simultaneously  with 
silicon,  retards  the  process.  The  behaviour  of  graphite  in  the  first  part  of  the  process 
is  similar,  as  it  has  to  be  converted  into  combined  carbon  before  it  is  oxidised.  In 
manganif  erous  grey  pig  the  silicon  seems  to  be  chiefly  combined  with  the  manganese.  In 
white  pig,  poor  in  silicon  and  containing  carbon  only  in  a  state  of  chemical  combination, 
the  process  is  more  rapid,  which  does  not  conduce  to  a  good  result.  There  is  produced 
a  thickly  liquid  steel  mixed  with  slag,  which  cannot  be  rendered  compact  by  forging. 
As  a  small  percentage  of  sulphur  is  less  hurtful  in  steel  than  in  wrought-iron,  good 


CHEMICAL  TECHNOLOGY. 


[SECT.  n. 


Fig.  142. 


coke-pig  may  give  satisfactory  results,  especially  if  manganese  is  present,  which  helps. 

to  remove  sulphur,  but  not  phosphorus. 

The  apparatus  consists  of  a  pear-shaped  converter  of  sheet-iron,  A  (Fig.  142).     It 

is  lined  with  a  fire-proof  mixture,  and 
turns  on  two  horizontal  points  by  means 
of  a  toothed  wheel,  K,  which  catches  into 
a  tQothed  rod  moved  by  the  piston  of  a 
hydraulic  press.  At  the  bottom  of  the  retort 
there  is  applied,  by  means  of  hydraulic 
pressure,  a  wind-chest,  M,  from  which 
tuyeres  with  forty-nine  to  eighty-four  aper- 
tures convey  the  air,  with  thorcmgh  distri- 
bution, into  the  interior  of  the  converter. 
The  blast  streams  out  from  the  pipe,  L, 
through  o,  into  a  space  round  the  pivot, 
d,  passes  downwards  in  the  pipe,  e,  and 
enters  the  wind-chest,  M,  through  the  pipe, 
D,  which  is  secured  to  e  by  means  of  a 

Fig.  143. 


bent  iron  strap.     The  case,  m,  surrounding  the  pivot,  d,  rests  upon  the  support,  Er 
and  is  connected  with  the  tube,'  o,  by  means  of  a  stuffing  box. 

In  working,  the  converter  is  first  properly  heated,  and  then  from  3  to  10  tons  of 
iron  melted  in  reverberatories,  or  cupolas,  F  (Fig.  143),  are  run  in  a  channel  through 
the  neck  of  the  converter,  J4,  inclined  more  than  90°  (and  shown  in  Fig.  143  by  dotted 


SECT,  ii.]  STEEL.  135 

lines),  in  such  a  manner  that  it  does  not  enter  into  and  clog  the  tuyeres  at  the  bottom, 
The  blast  is  turned  on,  and  the  converter  is  then  raised  to  an  upright  position.  The 
blast  must  have  so  strong  a  pressure  that  it  forces  the  iron  out  of  the  jets  of  the  tuyeres, 
and  distributes  itself  in  fine  streams.  In  the  first  period  which  thus  begins  (fining 
or  slagging  period),  a  temperature  is  produced  exceeding  the  melting-point  of  wrought- 
iron ;  and  silicon,  manganese,  and  a  part  of  the  iron  are  oxidised  ;  a  slag  is  produced 
consisting  of  ferrous  and  manganous  silicate  ;  and  the  graphite  is  converted  into  com- 
bined carbon,  but  without  the  combustion  of  much  of  it.  The  indication  for  judging 
the  process  is  chiefly  the  flame  issuing  from  the  mouth  of  the  converter,  £,  into  the 
chimney,  C  D,  the  sparks  and  the  matter  thrown  out,  as  well  as  the  spectroscopic 
character  of  the  flame,  and  the  appearance  of  samples  taken.  During  the  first  four 
minutes  no  flame  is  visible,  in  the  next  two  minutes  there  appears  a  small  pointed 
flame,  and,  after  six  or  eight  minutes,  an  unsteady  flame,  with  explosions.  In  these 
three  intervals  of  time  there  are  seen,  by  means  of  the  spectroscope,  at  first  a  faint 
continuous  spectrum  from  the  sparks  of  ignited  metal,  then  a  light  spectrum  with 
flashes  of  the  sodium  line,  and,  lastly,  a  bright  spectrum  with  a  permanent  sodium 
line,  a  red  lithium  line,  and  both  the  potassium  lines. 

With  the  explosions  there  begins  the  second  period  (the  period  of  eruptions  or 
boiling),  in  which  the  carbon  is  burnt  by  the  abundant  formation  of  ferroso-ferric 
oxide,  in  consequence  of  the  more  violent  and  copious  formation  of  carbon  monoxide ; 
the  mass  rises  up  (boils),  and  slags  and  particles  of  iron  are  thrown  forcibly  out  of  the 
neck  of  the  retort.  The  flame  becomes  bright  and  dense,  then  bright,  but  less  dense 
below.  With  the  spectroscope  there  are  seen,  in  addition  to  the  lines  above  mentioned, 
bright  carbon  monoxide  lines  in  the  red,  the  green,  and  the  blue,  and  the  bright  lines 
in  the  green.  In  about  fourteen  minutes  after  the  beginning  of  the  process  this  period 
is  at  an  end.  In  the  third  period  the  bath  has  become  quieter ;  the  eruptions  have 
ceased,  and  much  iron  is  burnt  along  with  the  carbon  still  remaining  ;  this  is  indicated 
by  a  brisk  rain  of  sparks,  whilst  the  flame  becomes  less  vivid  and  smaller.  With  the 
disappearance  of  the  flame  and  the  change  of  the  green  line  of  carbon  monoxide  into  a 
continuous  spectrum,  the  carbon  is  consumed  within  about  eighteen  to  twenty  minutes. 
The  iron  at  the  end  of  the  third  period  is  present  as  decarbonised  iron  (bar  iron).  If, 
as  is  generally  the  case,  the  production  of  steel  is  intended,  the  fourth  period  begins. 
For  this  purpose  the  blast  is  shut  off,  the  converter  is  inclined,  and  so  much  liquid 
manganiferous  spiegeleisen  or  ferro-mangan  is  introduced  at  the  neck  as  will  produce 
steel  containing  a  given  proportion  of  carbon.  The  converter  is  again  placed  upright, 
and  the  masses  are  allowed  to  mix,  or  the  blast  is  turned  on  again  for  a  moment  to 
effect  a  more  perfect  intermixture.  The  converter  is  then  turned  to  the  right,  and  the 
steel  is  poured  into  the  pan,  T,  and  thence,  by  means  of  the  hydraulic  crane,  P,  into  the 
moulds.  By  means  of  the  wheels,  S  and  K,  the  crane  can  be  turned  on  the  pivot,  Q, 
and  the  pan,  T,  tilted  by  means  of  q  r.  The  iron  screen,  F,  is  to  protect  the  workman, 
and  the  counterpoise,  U,  keeps  the  plate,  P,  in  equilibrium.  The  ferro-manganese  is 
not  merely  to  supply  carbon  to  the  iron,  which  has  been  decarbonised  by  the  Bessemer 
process,  but  as  the  manganese  present  is  more  readily  oxidised  than  the  carbon,  it  is  bo 
keep  the  proportion  of  the  latter  constant. 

Dahlems  has  followed  the  Bessemer  process  analytically  in  four  Swedish  establish- 
ments. (See  Table.) 


136 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


T 

.Langshjt  tan. 

.Nykroppa. 

ang  ro. 

es  an  ors. 

Crude  Iron. 

0  
Si  
Mn        

3  "94 
1-14 

o"6d. 

4'35 
0-88 
I'lS 

4-00 

I'02 

1-83 

4'22 
I  -06 
$•12 

Metal. 
I.                    time 

C  
Si           

2  min.  15  sec. 

4  '02 

0*04 

2  min.  30  sec. 
4'oi 

O'lO 

3  min. 

4  '03 
0-03 

4  min.  1  5  sec. 

4-02 
0-43 

Mn        

O'I2 

0-15 

O'22 

3-26 

II.                   time 

c  

4  min.  30  sec. 

I'lO 

5  min.  30  sec. 

I  'CO 

4  min.  45  sec. 
0-90 

8  min.  35  sec. 
1-30 

Si                            .... 

O'O^ 

0-05 

0-03 

0'12 

O'I2 

1-15 

O'I2 

0-85 

III.                  time 

c  

5  min.  30  sec. 
0-05 

6  min.  30  sec. 
0-08 

5  min.  45  sec. 

O'lO 

9  min.  20  sec. 
°'55 

Si           

O'OI 

0-04 

0-03 

0-07 

Mn         

o-o6 

0-08 

0-09 

o-43 

Slag. 
I. 

3472 

13-50 

14*20 

4-20 

Mangan  oxide       .... 
Magnesia      ..... 

1  3  '95 

O"24 
2  '60 

2976 
0-23 
0-42 

26-31 

O"22 
0-62 

46-38 
0-54 
1-26 

Alumina        

078 
4876 

2-28 
53-26 

2-86 
55-26 

3-08 
45  '87 

II. 
Fe  O 

2  1  '08 

9  '34 

18-52 

6-24 

Mn2Os   
Magnesia      

I3-48 
0-30 
3-25 

2370 
0-28 
o'6o 

31-01 

0-14 
0-38 

52*26 
0-29 
0-70 

Alumina        
Silica    

III. 
Fe  O 

0-98 

59  '92 

3C-S2 

3-90 
62-34 

7O'6O 

2-70 
47-20 

"U  '19 

2-49 
39  '07 

9-4.1: 

Mn203   . 
Magnesia 
Lime 
Alumina 
Silica     . 

I2'29 
O'2I 

2'3S 

072 
48-48 

21-39 

O'2I 

0-38 
2-14 

44^4 

25  '43 

O'll 

0-32 

2-24 
40-50 

48-92 
0-46 

I  -00 

2-94 
37-63 

In  the  basic  process  (of  Thomas  &  Gilchrist),  the  converter  is  lined  with  a  mixture 
of  burnt  dolomite  and  tar.  Besides  freshly  burnt  lime  is  introduced  into  the  heated 
converter  to  about  10  per  cent,  of  the  intended  charge  of  metal;  the  liquid  iron  is 
then  run  in  and  the  blast  is  turned  on. 

Finkener  showed  that  first  the  proportion  of  silicon  and  manganese  decreases,  then 
that  of  carbon,  and  lastly,  that  of  phosphorus  and  manganese,  if  the  latter  has  not 
already  disappeared  along  with  the  silicon.  The  removal  of  these  substances  is  the 
consequence  of  their  oxidation,  and  of  the  property  of  the  products  of  oxidation  to 
separate  from  the  liquid  iron  which,  however,  can  take  place  only  when  the  substances 
eliminated  under  the  above  circumstances  have  no  especial  decomposing  action  upon  each 
other.  Experiments  show  that  the  carbon  escapes  chiefly  as  carbon  monoxide,  with 
a  small  proportion  of  dioxide,  which  is  such  that  the  transit  of  carbon  dioxide  to  the 
iron  is  compensated  by  the  carbon  given  to  the  iron  by  the  carbon  monoxide.  The 
proportion  between  carbon  monoxide  and  carbonic  acid  may  vary  with  the  temperature 
and  the  quality  of  the  iron  exposed  to  the  action  of  the  gaseous  mixture,  but  the 
carbonic  acid  does  not  entirely  disappear  except  the  proportion  of  carbon  in  the  iron  is 


SECT,  ii.]  STEEL.  137 

very  high.  The  phosphorus  is  oxidised  to  phosphoric  acid  along  with  iron  enough  to 
form  a  ferrous  phosphate,  containing  3  mols.  iron  to  i  mol.  of  phosphoric  acid.  A  com- 
pound of  phosphoric  acid  with  a  smaller  proportion  of  iron  cannot  separate  from  the 
liquid  iron,  as  it  would  be  decomposed.  The  silicon  is  converted  into  silicic  acid,  which, 
like  the  phosphoric  acid,  enters  into  the  slag  as  a  ferrous  compound,  containing  i  mol. 
silica  to  i  at.  iron  or  manganese.  The  oxygen  entering  into  the  liquid  mass  will  at 
first  burn  all  the  constituents  with  which  it  comes  in  contact,  but  of  the  compounds 
formed  only  those  will  remain  undecomposed  which  are  equally  fusible  with  the  liquid 
mass.  As  long  as  silicon  is  present  the  carbon  will  not  decrease ;  the  carbon  monoxide 
as  it  is  formed  decomposes,  forming  silicate  and  metallic  carbide.  The  iron  silicide  has 
such  a  reducing  action  that  it  reduces  a  part  of  the  iron  present  in  the  normal  ferrous 
silicate  to  the  metallic  state.  The  phosphate,  which  is  more  readily  reduced,  cannot 
remain  ;  it  is  decomposed  in  contact  with  the  metallic  silicide  to  silicate  and  metallic 
phosphide.  A  decrease  of  the  phosphoric  acid  does  not  occur  so  long  as  silicon  is 
present.  Iron  is  protected  from  oxidation  by  manganese,  just  as  is  phosphorus  by 
silicon ;  the  chief  product  of  the  oxidation  is,  in  the  beginning,  manganous  bisilicate. 
After  removal  of  the  silicon,  carbon  monoxide  appears,  with  a  proportion  of  carbon 
dioxide,  which  increases  somewhat  as  the  carbon  dioxide  decreases.  Manganous  and 
ferrous  phosphates  are  found  in  perceptible  but  not  large  quantities,  and  are  chiefly 
decomposed  by  the  iron  carbide  which  still  exists.  This  reduction  can  only  be  ascribed 
to  the  mixture  of  carbon  monoxide  and  dioxide,  on  the  supposition  that  the  reducing 
power  of  the  mixture  increases  more  rapidly  as  the  temperature  rises  than  that  of  iron 
carbide.  Against  the  assumption  that  carbon  monoxide  has  a  reducing  action  upon 
ferrous  phosphate,  must  be  put  the  small  proportion  of  phosphorus  in  the  metallic 
iron  selected  from  different  slags.  If  iron  carbide  is  the  reducing  agent,  the  iron 
phosphide  formed  immediately  comes  in  contact  with  iron,  and  there  is  no  inducement 
for  the  formation  of  an  iron  rich  in  phosphorus.  When  the  carbon  has  disappeared  the 
separation  of  the  iron  phosphate  is  effected.  The  iron  sulphide  remains  undecomposed 
even  after  the  removal  of  the  phosphorus.  After  the  addition  of  spiegeleisen  the  pro- 
portion of  phosphorus  increases  by  the  reduction  of  ferrous  phosphate  by  iron  carbide. 
Fig.  144  shows  the  changes  taking  place  in  iron,  and  Kg.  145  those  in  slag,  according 
to  an  experiment  made  at  Horde. 

According  to  Hilgenstock,  the  quadri-basic  calcium  phosphate,  Ca4P2O9,  is  the  sup- 
porter of  the  basic  process.  In  a  crude  iron  which,  when  put  into  the  converter, 
contained  3  per  cent,  phosphorus,  i  per  cent,  manganese,  0^15  per  cent,  silicon,  2"j 
carbon,  and  0*15  sulphur,  the  silicon  is  soon  removed,  the  combustion  of  the  carbon 
begins,  and  with  it  the  oxidation  of  the  manganese  and  the  phosphorus,  so  that  after 
decarbonising  it  retains  o'oi  to  0*02  Si,  o'io  to  0*15  C,  0*2  to  0-3  Mn,  i'5  to  2  P,  and 
o- 1 o  to  0-128.  After  the  dephosphorising  process,  during  which  the  metal  mostly 
requires  to  be  cooled,  the  bath  retains — Si,  O'o8  to  o'oi  ;  C,  o'o6  to  0-14;  Mn,  0-07 
to  0-25 ;  P,  0-05  to  0*07  ;  S,  o'o8  to  0-09,  but  as  much  as  0*3  per  cent,  of  oxygen. 

After  the  bath  has  been  reduced  by  ferro-manganese,  the  finished  steel  contained 
Si,  o-o8  to  o-oi  ;  C,  o-io  to  0-20 ;  Mn,  0*35  to  0*45  ;  P,  0-05  to  0-09,  and  S,  0-04  too-o6. 
Among  the  oxidation  products  silicon  as  manganous  silicate  is  not  reduced  at  the 
initial  low  temperature  of  the  bath,  or  afterwards  at  a  higher  temperature  as  calcium 
silicate  by  any  constituents  of  the  bath  ;  hence  the  rapid  and  almost  total  disappear- 
ance of  the  silicon ;  silicon  if  once  oxidised  remains  in  the  slag  as  a  basic  silicate. 
Carbon  monoxide  disappears  without  any  noteworthy  reductive  action  either  upon 
metal  or  slag,  so  that,  save  the  action  of  the  current  of  the  air,  we  have  only  the 
reactions  of  the  two  (igneous)  liquids,  the  metal  and  the  slag,  to  consider.  At  the 
beginning  of  the  dephosphorising  process  we  have  to  do  with  them  only.  After  the 
bath  is  decarbonised  the  manganese  is  reduced  to  a  few  tenths  and  the  phosphorus  to 


CHEMICAL  TECHNOLOGY. 


[SECT.  n. 


one-half.  The  oxidation  and  separation  of  the  phosphorus  takes  place  as  tribasic 
ferrous  phosphate.  The  iron  phosphate  is  at  once  converted  into  calcium  phosphate 
by  the  more  powerful  base  lime,  and  there  is  formed  the  quadri-basic  phosphate,  which 
is  not  reduced  by  metallic  iron.  The  liberated  ferrous  oxide  is  again  reduced  by 
contact  with  phosphorus  in  the  bath,  so  long  as  the  proportions  are  suitable.  If 
there  is  from  0-5  to  0-3  per  cent,  of  phosphorus  in  the  bath  no  notable  quantity  of 


Fig.  144. 


c 

^ 

\ 

\ 

\ 

ft 

t-o 

»:* 
P 

t-o 
Si 

OS 

MD 
S 

\ 

\ 

x, 

\ 

1 

^ 

'  C 

\ 

\ 

\ 

/ 

s^ 

\ 

a 

N 

\ 

i 

\ 

< 

\\ 

I 

••s. 

V 

I 

\ 

\ 

i 

\ 

I 

i 

\ 

•» 

V 

\ 

•\ 

V 

~\ 

... 

— 
" 

\" 

\ 

M 

W  ' 

- 

\ 

Y 

,i  ' 

C 

£ 

>. 

_j  . 

5  "••• 

S 

—A 

' 

P 

Fig.  145- 


12.        14Min 


ferrous  oxide  remains  unreduced,  and  not  until  afterwards  does  the  iron  increase  in 
the  slag.  It  is  one  of  the  grandest  industrial  reactions  that  in  masses  of  crude  iron 
of  the  weight  of  ten  tons  the  phosphorus  in  contact  with  three  tons  of  slag  is  reduced 
within  a  few  minutes  to  some  tenths  per  cent. 

The  Slag. — The  basic  process  yielded  in  1886,  in  round  numbers,  400,000  tons  of 
slag  containing  from  30  to  35  per  cent,  calcium  phosphate  ;  its  utility  in  agriculture  is 
therefore  of  the  highest  importance.  At  first  the  slag  was  prepared  in  a  variety  of 
ways ;  now  it  is  simply  ground  to  a  fine  powder,  since  experience  has  proved  that  it  is 
soluble  in  the  soil. 

In  experiments  on  the  value  of  the  phosphoric  acid  in  the  "  Thomas  slags,"  Miircker 
proved  that  when  finely  ground  it  had  56  per  cent,  of  the  efficacy  of  the  soluble  phos- 
phoric acid  in  superphosphates,  even  on  superior  soils.  On  moorland  soils  it  was  of 
equal  value  to  the  "  precipitated  phosphates."  Slag  has  no  injurious  effects  upon  the 
crops.  The  only  condition  is  very  fine  grinding. 

The  Siemens-Martin  Process. — In  this  process  the  decarbonising  agent  is  iron 
oxide,  iron  ores,  and  iron  waste.  The  crude  iron  is  melted  in  a  Siemens  reverberatory, 
and  it  is  introduced  into  the  bath,  covered  with  a  layer  of  slag,  old  iron,  &c.,  until  a 
sample  drawn  shows  that  the  entire  mass  has  assumed  the  fibrous  nature  of  bar-iron. 
By  adding  a  certain  quantity  of  crude  iron  the  entire  mass  is  converted  into  steel. 
The  table  on  p.  140  shows  the  working  of  this  Siemens- Martin  process  at  the  rolling 
works  at  Graz. 


SECT.    II. J 


STEEL. 


Very  important  experience  has  been  gained  with  the  use  of  water-gas  ia  this 
process.    The  furnaces  employed  at  Witkowitz  have  good  heat-stoves  (Figs.  1 46  to  149)  ; 


Fig.  146. 


Fig.  147. 


Fig.  148. 


-lli'JCf) 

SchnHt  ARC1)  Section  ABCD 


Gasletiung 
Windleitunfi 


Gas-pipiug 
Air-pipe 


Explanation  of  Terms. 
R^™  Schnitt  ED 

Kinyuss 


Fig.  149. 

Section  ED. 
Inflow. 


they  are  round  and  enclosed  with  a  sheet-metal  screen  ;  the  bottom  is  cooled  with  air,. 
The  vaults  of  the  Martin  furnaces  can  be  lifted  off.  For  this  purpose  a  powerful  cran& 
is  fixed  between  the  two  Martin  furnaces,  and  it  serves  also  to  raise  the  steel  pan  to 
the  necessary  level.  Each  gas  tuyere  has  a  cock  connected  by  a  rod  to  the  rest  in  such 
a  manner  that  all  the  cocks  can  be  turned  at  once.  The  two  gas-pipes  from  which  the 
gas  tuyeres  branch  off  to  each  furnace  have  throttle  valves.  The  air  is  forced  by  a 
blast  under  a  small  bell,  which  always  maintains  the  necessary  pressure  (no  mm.,  equal 
to  the  pressure  of  the  gas).  The  air-pipes  branch  off  in  two  arms  at  each  furnace  and 
discharge  into  the  furnace  channels  through  which  the  flue-gases  pass  from  the 
regenerators  to  the  chimney.  Each  of  these  channels  can  be  shut  alternately  by  the 
slide,  S,  whilst  the  other  is  connected  with  the  flue. 


140 


CHEMICAL    TECHNOLOGY. 


[SECT.  n. 


* 
Charge. 

Iro 

Mn. 

n. 
Si. 

Slag. 

C. 

SiOjj. 

A1203. 

MnO. 

FeO. 

CaO. 

6.40  A.M.,  ist  charge  of  — 

2100  kilos,  white  pig, 

1500     „      grey  pig, 

1000     „      steel  ends, 

Sample  when  smelted     .... 

1-13 

O'i4 

O'OI 

42-56 

I  -46 

28-39 

29-47 

9.10  A.M.,  2nd  charge— 

500  kilos,  hoop-iron, 

500     .,     turnings, 

2000     „      old  boiler  plates 

1000     „      old  rails, 

Sample  when  smelted     .         .        .        .0*69 

O'll 

— 

42-94 

I'53 

22-23 

3^47 

11.20  A.M.,  3rd  charge  — 

i 

3900  kilos,  old  rails, 
Sample    

0*27 

0-13 

__ 

48-03 

1-76 

18-48 

30-I5 

078 

I2.2O  P.M.,  Sample   .                                                         O'2O  :     O'I2 

— 

47-87 

2-34     I9-53 

29-99 

1.40  P.M.,  sample     o'ia 

0-08 

— 

48-90 

2"OI 

I9'37 

28-88 

1.45  P.M.,  added   120    kilos,    silico 

ferro-manganese, 

Average  sample  of  day's  work        .        .  ]    0*31 

0-45      o.oi 

49-63 

— 

20-89 

25-42 

In  a  water-gas  Martin  furnace  200  hectokilos  of  steel  were  produced  in  twenty-four 
hours.  The  consumption  of  gas  is  about  8  cubic  metres  per  minute.  The  air  in  the 
regenerators  is  heated  to  1200°  to  1400°,  whilst  the  temperature  in  the  furnace  is  near 
the  melting-point  of  platinum.  The  heat  of  the  escaping  gases  behind  the  regenerators 


Fig.  150. 


Fig.  152. 


Acid. 
Basic. 

is  still  400°  to  500° ;  60  cubic 
metres  of  water-gas  are 
used  for  i  oo  kilos,  of  finished 
steel,  including  the  prelim- 
inary heating,  &c.,  of  the 
bottom. 

In  a  common  Siemens- 
Martin  stove  50  kilos,  of 
Ostrau  coal  are  used  for  100 
kilos.  Hence,  for  the  same 
amount  of  work,  the  water- 
gas  Martin  furnace  con- 
sumes only  47  per  cent,  of 
the  quantity  of  heat  which 
an  ordinary  Siemens-Martin 
furnace  requires. 

Basic  Hearth-Smelting. — This  process  promises  to  be  of  great  importance  now  the 
difficulties  of  producing  a  lining  of  magnesia  have  been  overcome.  Figs.  150  to  152 
show  a  furnace  suitable  for  charges  of  1 2  tons.  The  vault,  built  of  an  acid  stone,  is 
supported  by  a  strong  furnace  frame,  whilst  the  upper  acid  part  of  the  hearth-walls 
consists  of  separate  parts  built  in  boxes,  which,  if  needful,  e.g.,  for  mending  the  furnace, 
can  be  turned  back  on  the  arm,  a,  which  rotates  on  the  furnace-frame,  or  may  be 


SECT.    II.] 


STEEL. 


141 


entirely  changed.  By  this  arrangement  all  strain  is  removed  from  the  basic  hearth- 
walls — a  point  of  great  importance,  as  basic  materials  are  mostly  very  sensitive  to 
pressure.  The  basic  stones  consist  of  burnt  dolomite,  and  are  submitted  to  a  pressure 
of  150  tons  on  the  flat  side,  and  then  immediately  built  into  the  furnace  and  heated  as 
quickly  as  possible.  In  small  furnaces  the  basic  walls  reach  up  to  the  vault,  otherwise 
only  up  to  the  upper  angle  of  the  charging  apertures;  below  the  slag-line  8  to  10  per 
cent,  of  sand  is  mixed  with  the  basic  mass.  The  upper,  changeable  part  of  the  walls 
(45  centimetres  high)  is  built  of  2000  ordinary  acid  stones,  separated  from  the  basic 
lining  by  a  layer  of  chrome  iron  and  retort-coke,  mixed  with  lime  and  tar.  The  vault, 
consisting  of  3000  acid  stones,  is  luted  with  clay  to  the  walls. 

When  the  furnace  has  been  duly  heated  it  is  charged  with  ore  or  anvil-dross  and 
lime,  upon,  which  crude  and  wrought  iron  are  laid.  During  heating  care  must  be  taken 
that  the  slags  are  sufficiently  basic.  The  duration  of  the  heat  is  generally  shorter  than 
that  of  an  acid  furnace,  since  the  dephosphoration  is  complete  as  soon  as  the  iron  is 
entirely  melted.  It  might  then  be  tapped,  only  that  a  higher  temperature  is  necessary 
for  compact  castings,  and  a  further  decarbonisation  is  often  necessary.  Hence  it  is 
proposed  to  heat  with  water-gas,  in  the  expectation  of  finishing  a  process  in  four 
and  a  half  hours. 

Dolomite  powder,  raw  or  burnt,  and  mixed  with  8  to  1 2  per  cent,  of  sand,  is  used 
for  repairs. 

Further  experiments  were  made  on  a  5 -ton  Martin  furnace  with  a  basic  lining.  Two 
charges  were  melted  of  60  parts  crude  iron,  30  parts  granulated  steel,  and  three  parts 
spiegeleisen,  and  a  third  of  70  crude  iron,  30  steel,  and  4  spiegeleisen.  After  the 
mass  was  in  flux  a  sample  of  metal  and  one  of  slag  was  drawn  every  half -hour,  and 
besides  a  sample  of  slag,  A,  after  the  charge  was  one-third  melted,  and  another,  B, 
after  it  was  two-thirds  melted. 


Metal.                              i. 

2. 

3- 

4- 

5.     1    6. 

7- 

8. 

9- 

10. 

12. 

13- 

Steel. 

C  1760 
Si  10-075 
P  ii'400 
Mn  o-ioo 
S  0-180 

1-680 
0-075 
I-370 

o-ioo 
0-169 

I-390 
0-070 
I-320 
O'II5 
0-I62 

I-260 
O-O9O 

rno 

0-090 
0-150 

Q-840^-5  100-400 
0-080^-060  o-o6o 
0-990:0-900  0-8  10 
o-ioo  0-080  0-090 
0-145  0-140  0-145 

0-220 

0-040 
0700 

0-075 
0-147 

O'OgO 
0-035 
0-62O 
0-085 
0-137 

0-075 
0-030 
0-460 
O'lOO 

0-133 

0-075 

0-018 
0-180 
0-125 

O'I2O 

0-070 

O'OIO 

0-085 

O'I2O 
O'lII 

0-140 
trace 
0-075 
0-370 
0-089 

Slag. 

A. 

B. 

i. 

2. 

3. 

4- 

5- 

6. 

7- 

8. 

13. 

Si02 

14-40 



23-60 











— 

— 

17-40 

FeA 

6-81 

0-40 

073 

3'80 

077 

0-90 

2-60 

2-30 

I  -60 

I-I7 

1-64 

FeO 

44-20 

21-50 

8-07 

675 

7-28 

6'2I 

6-35 

7-38 

477 

5-3I 

4'53 

ALA 

6-80 

— 

7-00 

— 

— 

— 

— 

— 

7-50 

MnO 

2-04 

— 

8-15 

— 

— 

— 

— 

— 

— 

— 

4-60 

CaO 

14-00 

— 

38-10 

— 

— 

— 

— 

— 

— 

— 

44-00 

MgO 

0-84 

— 

1-28 

— 

— 

— 

— 

— 

— 

— 

2-80 

PoOB 

lO'OO 

— 

12-45 

— 

— 

— 

— 

— 

— 

— 

1575 

Fe 

38-90 

17-09 

679 

7'93 

6-10 

5  '40 

6-90 

7-41 

4-80 

4-90 

4  '63 

The  separation  of  the  substances  in  question  from  the  iron  in  the  basic  reverbera- 
tory,  the  basic  converter,  and  the  puddling  furnace  is  shown  in  the  diagrams  Figs.  153 
to  155.  The  processes  in  the  basic  reverberatory  have,  as  the  lines  show,  the  greatest 
resemblance  to  those  in  the  puddling  furnace.  The  lines  of  phosphorus  and  sulphur 
run  in  a  similar  manner,  a  difference  existing  only  in  the  quantities  of  these  sub- 
stances eliminated.  In  the  Siemens  process  18  to  19  per  cent,  of  phosphorus  is 
separated  more  than  in  the  puddling  furnace ;  but  the  puddling  furnace  oxidises  5  per 
cent,  more  sulphur  than  the  basic  reverberatory.  In  both  furnaces  almost  the  total 
silicon  and  manganese  are  conveyed  into  the  slag  in  the  first  two  periods  of  time,  and 
about  40  per  cent,  of  phosphorus  is  removed.  The  lines  indicating  the  oxidation  in 


142 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Fig.  153- 


the  basic  converter  take  a  quite  different  course  from  those  in  the  basic  reverberatory, 
although  the  results  obtained  by  the  oxidation  are  equal.  The  silicon  line  only 
resembles  that  of  the  other  processes.  The  separation  of  carbon  in  the  basic  reverbera- 
tory is  so  irregular  that  it  cannot  be  represented  by  a  line. 

Carbonisation  Steel. — The  second  principal  kind  of  steel  (cement  steel)  is  produced 

by  the  prolonged  ignition  of  bar-iron 
along  with  carbonaceous  substances, 
which  generally  contain  at  the  same 
time,  nitrogen.  To  obtain  normal 
cement  steel  it  is  necessary  to  use 
good  bar -iron.  The  Swedish  iron 
(from  magnetic  ore  and  red  haema- 
tite) is  brought  in  large  quantities 
to  England  for  conversion  into  ce- 
ment steel,  as  even  the  best  English 
iron  is  suitable  only  for  ordinary 
steels. 

The  process  for  the  manufacture 
of  cement  steel  is  as  follows  : — The 
iron  bars  are  laid  in  layers,  along 
with  the  carbonaceous  powder,  in 
earthen  boxes,  closed  air-tight.  Two 
such  boxes  (a  pair  of  pots)  are  placed 
in  a  furnace  which  is  fired  with  coal, 
rarely  with  wood,  and  kept  at  a  red 
heat  for  one  to  three  weeks.  It  is  then  let  cool,  and  the  bars  are  taken  out.  A 
furnace  contains  about  15  tons  of  iron.  About  5  per  cent,  of  carbon  penetrates  by 
molecular  migration  without  the  iron  being  fused ;  the  action  of  gases  falls  quite  into 
the  background 

Sheer  Steel. — Both  crude  and  cement  steel  are  very  unequal  in  their  composition, 
and  cannot  therefore  be  used  immediately,  but  must  be  rendered  uniform  by  refining. 

Fig-  154- 


Explanation  of  Terms. 

1'eriode  von  4  Stunden  Period  of  4  hours. 

Abscheidung  in  % 
Kohlenstoff  unbestimmt 
Aiifnahme  in  %  Ge&chmolzen 
Zritcinheiten 
fiasiacher  Flammofen 


Separation  in  per  cents. 
Carbon  not  determined. 
Taken  up  in  per  cerrt.  fused. 
Units  of  time. 
Basic  reverberatory. 


flasischer  Converter 
Abscheidung  in  % 
Aufnahme  in  % 
Zeiteinheiten 


Basic  converter. 
Matter  eliminated  in  per  cents. 
Matter  taken  up  in  per  cunts. 
Units  of  time. 


Explanation  of  Terms. 

I'uddelofen 
Abscheidung  in  % 
Aufnahme  in  % 


Puddling  furnace. 
Matter  eliminated  in  per  cents. 
Matter  taken  up  in  per  cents. 
Units  of  time. 


To  this  end  the  crude  bars  are  forged  out  to  thin,  flat  slips,  which  are  thrown  into  cold 
water  when  red  hot ;  several  of  them  are  collected  in  a  sheaf,  heated  to  whiteness,  and 
again  wrought  out  under  the  hammer  or  between  rollers.  For  cement  steel  a  simple 
re-melting  is  more  suitable. 

Cast  Steel. — This  material,  so  widely  used  in  modern  industry  for  the  manufacture 


SECT.    II.] 


STEEL. 


143 


of  cannons,  tyres  for  railway  wheels,  axles,  anchors,  pump-rods,  and  for  tools,  is  pro- 
duced by  re-melting  finery  steel,  Martin  steel,  Bessemer  metal,  or  carbonised  steel. 
Every  desired  property  can  be  obtained  by  a  due  selection  of  materials. 

The  melting  is  effected  in  fire-proof  crucibles  (without  a  blast)  in  a  fire  of  coke,  or 
in  a  coal  reverberatory,  or  with  a  gas  fire  and  Siemens  regenerators.  The  melted 
steel  is  cast  in  bars  in  iron  moulds.  When  cold,  the  bars  are  again  heated  to  redness, 
wrought  out  under  the  hammer  or  between  rollers.  The  metal  thus  treated  is  refined 
cast  steel. 

Run  Steel. — This  kind  is  formed  by  melting  together  crude  iron  and  wrought-iron. 
The  quality  of  steel  thus  obtained  (known  in  Italy  as  Glisenti  steel)  depends  on  the 
quantity  (and  quality)  of  the  wrought-iron  used. 

As  a  welding  agent  for  cast  steel,  a  mixture  of  borax  with  sal-ammoniac  and  potas- 
sium ferrocyanide  is  in  use. 

A  remarkable  phenomenon  is  the  infiltration  of  cast  blocks.  A  steel  block  had 
above  and  below  the  following  compositions— 


Fe 

C 

Si 

S 

P 

Mn 


Top. 

98-304 
0760 

traces 
0-187 
0-191 
0-5S8 


Bottom. 
99-038 

0-350 

traces 

0-044 

0-044 


lOO'OOO  99'990 

Iron  and  steel  castings  not  unfrequently  contain  hollows,  the  outer  layer  especially 
containing  numbers  of  bubbles,  a  (Fig.  156).  The  bubbles  more  in  the  interior  arise 
during  progressive  cooling,  having  a  pear  shape,  with  the  point 
turned  outwards,  and  forming  the  series  b.  Other  hollows,  c, 
appear  in  the  midst  of  the  casting,  and  decrease  from  above 
downwards ;  a  and  b  arise  from  the  liberation  of  gas  dissolved 
in  the  liquid  metal,  but  c  in  consequence  of  the  condensation  of 
the  iron  on  becoming  solid.  Manganese,  silicon,  and  magnesium 
have  been  used  as  a  remedy  for  these  bubbles.* 

Steeling. — For  certain  technical  purposes  it  is  sufficient  to 
convert  iron  into  steel  superficially.  This  steeling  or  case  hard- 
ening is  effected  by  cleaning  the  surface  of  the  article  with 
emery,  and  heating  it,  along  with  a  carbonaceous  powder,  in 
an  air  furnace  without  a  blast.  Or  the  surface  iron  may  be 
steeled  by  covering  it  when  red  hot  with  potassium  ferrocyanide 
or  with  a  mixture  of  clay  and  borax. 

Properties  of  Steel. — Steel  is  generally  of  a  pale  greyish- 
white  colour,  moderate  lustre,  granular,  and  of  homogeneous 
fracture ;  the  better  the  sample  the  finer  is  the  grain.  The 
granular  texture  of  steel  is  characteristic ;  good  mild  steel  has 
never  the  coarse  grain  of  grey  crude  iron  nor  the  fibrous  texture 
of  wrought-iron.  Hardened  steel  resembles  in  its  fracture  the  finest  silver,  and  the 
grains  can  scarcely  be  distinguished  with  the  naked  eye.  Like  wrought-iron,  it  may 
be  cut  and  welded  when  hot,  but  it  must  be  cautiously  heated  to  avoid  decarbonising. 
It  is  fusible  like  cast-iron.  Its  specific  gravity  is  7-62  to  7*92,  and  is  diminished  on 
tempering — e.g.,  from  7*92  to  7*55.  Its  proportion  of  carbon  varies  from  0-25  to  2 
per  cent.  With  higher  proportions  of  carbon,  its  solidity  and  hardness  increase,  but 
its  elasticity  decreases.  It  contains  no  graphite.  If  quenched  when  ignited,  it  becomes 

*  A  small  addition  of  aluminium  has  latterly  been  found  successful. 


144 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


harder  and  brittle,  so  as  to  scratch  glass  and  resist  the  file.  Polished  steel  assumes 
various  colours  when  gradually  heated.  These  colours  are  used  for  determining  the 
temperature  and  the  consequent  degrees  of  hardness.  For  this  purpose  metallic  baths 
are  used,  heated  to  their  melting-point.  Into  such  melted  metal  the  steel  is  plunged 
until  it  assumes  the  temperature  of  the  bath.  The  following  table  gives  the  com- 
position of  the  baths  found  convenient  for  different  kinds  of  cutting  and  piercing 
instruments : — 


Instruments. 

Metal  Bath. 

Heat. 

Colour. 

Lead. 

Tin. 

Lancets    ..... 

7'0 
8-0 

8-5 
14-0 
19-0 
-48-0 
50  'o 
boiling  li 

4 
4 

4 

4 
4 
4 

2 

nseed  oil 

220° 

228 
232 

254 
265 
288 
292 
316 

pale  yellow 
straw  colour 
brown  yellow 
brown,  purple  spots 
purple 
light  blue 
royal  blue 
black  blue 

Penknives        .... 
Scissors  and  chisels 
Axes,  pocket-knives,  plane-irons 
Blades,  watch-springs,  crinoline  steel 
Daggers,  gimlets,  rapiers,  fine  saws 
Hand-saws       

The  lower  the  heat  of  the  steel,  the  harder,  but  the  more  brittle,  it  remains.  It 
cannot  be  denied  that  iron  may  be  converted  into  steel  by  other  substances  besides 
carbon,  which  may  probably  be  replaced  by  its  near  ally,  boron,  and  possibly  by 
silicon. 

Admixtures  of  other  materials  confer  upon  steel  valuable  properties  ;  thus  tungsten 
steel  owes  its  peculiar  firmness  to  the  presence  of  tungsten.  Samples  of  tungsten  steel 
(I.)  and  tungsten  iron  (II.)  had  the  following  composition — 


Fe  . 

W  . 

Mn     . 
Co  and  Ni 

Si  .        . 
P 
S 

c 


I. 

85-000 
11-028 

1-493 

trace 
0-263 
0-007 
trace 
2-147 

99-938 


II. 

68-363 
28-181 
0-986 
trace 
0-233 
0-008 
trace 
1-882 


Similar  assertions  are  made  concerning  titanium-  and  chromium-steels,  but  whether 
•with  justice  must  remain  for  the  present  undecided. 

A  celebrated  kind  of  steel  is  that  of  Damascus,  used  for  the  Damascus  sword-blades, 
though  the  raw  material  was  brought  from  Cabul.  If  its  surface  is  moistened  with  an 
acid  it  displays  an  uneven  veining,  a  property  which  is  not  lost  by  re-melting.  Such 
steel,  Wootz,  is  made  in  India  by  the  natives.  Crude  iron,  obtained  by  a  very 
imperfect  process,  is  broken  up,  mixed  with  10  per  cent,  of  the  chipped  wood  of  Cassia 
auriculata,  placed  in  a  crucible,  covered  with  leaves  of  Asdepia  gigantea  ;  the  crucible 
is  coated  with  moist  clay  and  heated  in  a  furnace  for  two  and  a  half  hours,  at  the 
lowest  available  temperature.  The  steel  thus  obtained  is  re-heated  before  forging. 

Two  samples  of  Wootz  had  the  following  composition — 

Combined  carbon    .....    4-333 
Graphite 0-312 


Si 
S 
Al 
P 

As 


0-045 
0-181 


0-037 


0*0167 

0-0035 
0*0006 
trace  • 


trace 


Steel  Engraving. — For  engraving  and  etching  on   steel  there  are  used  plates  of 


SECT.    II.] 


COBALT. 


cast  steel,  which  are  decarbonised  on  the  surface,  and  after  engraving  are  re-converted 
into  steel. 

An  excellent  fluid  for  etching  is  a  solution  of  2  parts  iodine  and  5  parts  potassium 
iodide  in  40  parts  of  water. 

MANGANESE. 

Occurrence. — The  most  important  ore  of  manganese  is  pyrolusite,  Mn02,  often 
spoken  of  in  commerce  simply  as  "  manganese."  It  contains  generally  small  quantities 
of  baryta ;  silica  and  water,  and  sometimes  larger  proportions  of  nickel,  cobalt,  and 
some  thallium.  Other  manganese  ores  are  braunite,  Mn203,  manganite,  Mn2O3H20, 
hausmannite,  in  which  the  manganous  oxide  is  in  part  replaced  by  potassa,  baryta, 
magnesia,  and  cuprous  oxide,  and  manganese-spar,  MnC03.  The  manganese  of  commerce 
is  often  a  mixture  of  pyrolusite,  hausmannite,  braunite,  &c. 

Preparation. — Manganese  is  prepared  by  reducing  the  ores  in  crucibles.  Latterly 
it  has  been  obtained  on  the  large  scale  along  with  a  larger  or  smaller  proportion  of 
iron  as  ferromanganese.  Its  preparation  is  effected  in  blast  furnaces  with  a  plentiful 
addition  of  lime.  Manganese  has  a  great  tendency  to  pass  into  the  slags,  so  that  in  a 
well-worked  blast  furnace  from  40  to  50  per  cent,  of  the  manganese  in  the  ores  is  to 
be  found  in  the  slags,  which  contain  from  6  to  9  per  cent,  of  metallic  manganese.  Ta 
extract  more  than  60  per  cent,  of  the  ores  is  rarely  remunerative,  as  the  consumption 
of  coke  is  very  high  and  the  spiegel  acquires  grey  spots  by  taking  up  silicon. 


Ferromanganese 

Crude 

I. 

II. 

III. 

Manganese. 

c 

6-21 

6  '600 

5-874 

6-0-6-5 

tti 

0-28 

0-093 

0'2IO 

0-5-1-2 

P 

. 

0-06 

0-300 

0-305 

Cu 

0*14 

— 

O-O9O 

Mn 

69-64 

8  1  -240 

57-608 

90-0-92-0 

Fe 

23-25 

I2-OOO 

35-03I 

0-5-1-5 

Co 

— 

— 

O-O7O 

Alloys  of  copper  and  manganese  have  been  produced  by  Gersdorff  and  then  by 
Schroter,  by  heating  a  mixture  of  copper,  manganic  oxide,  and  carbon  in  a  crucible. 
They  are  very  hard  and  take  a  polish ;  their  colour  is  white  to  rose.  Manhes  has 
used  them  to  reduce  cuprous  oxide  in  fining  copper.  Manganese-silver,  an  alloy  of  80 
parts  copper,  1 5  manganese,  and  5  zinc,  is  white,  works  well  and  takes  a  fine  polish. 

COBALT. 

Cobalt  is  chiefly  met  with  as  speiss,  CoAs2,  and  as  cobalt  glance,  CoAsS.  Recently 
metallic  cobalt  has  been  prepared  on  a  large  scale  at  Iserlohn,  and  at  Pfannenstiel, 
near  Aue  (Saxony).  It  has  a  silvery  white  colour  with  a  reddish  cast,  a  higher  lustre 
than  nickel,  and  polishes  well.  When  obtained  by  electrolysis  or  by  reduction  as 
a  pure  metal,  it  is  flexible  and  ductile,  but  as  found  melted  under  ordinary  circum- 
stances it  is  porous  and  crystalline,  and  can  neither  be  hammered  nor  rolled.  This  evil 
is  due,  according  to  Fleitmann,  to  the  absorption  of  carbon-monoxide,  and  can  be  removed 
by  the  addition  of  o'i  per  cent,  of  magnesium.  It  fuses  at  a  very  high  temperature. 
At  a  white  heat  steel  and  iron  may  be  welded  together  with  cobalt,  and  iron,  plated 
on  both  sides  with  cobalt,  can  be  rolled  out  very  thin.  It  is  slowly  dissolved  by 
dilute  acids ;  more  rapidly  by  nitric  acid  and  aqua  regia. 

Cobalt  Colours. — The  ores  to  be  worked  for  cobalt  colours  are  roasted,  and  are  then 
called  safflor  or  zaffre.  According  to  their  purity,  they  are  distinguished  as  ordinary 
(SO),  medium  (MS),  and  fine  (FS  and  FSB1).  They  consist  essentially  of  cobalt  oxide. 


146  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

nickel,  arsenic,  with  traces  of  manganese,  and  bismuth  oxides,  &c.  In  Sweden,  zaffre 
is  prepared  by  precipitating  a  solution  of  cobaltous  sulphate  with  a  solution  of  potassium 
carbonate.  From  zaffre  are  prepared  :  smalts,  cobalt  ultramarine,  creruleum,  Binmann's 
green  (cobalt  green,  or  Saxon  green),  with  which  are  connected  cobalt  yellow,  cobalt 
violet,  and  cobalt  bronze. 

Smalts. — Glass  is  coloured  blue  by  compounds  of  cobalt.  If  zaffre  (impure 
cobalt  oxide)  is  fused  with  silica  and  potash,  we  obtain  a  deep-blue  glass,  which, 
when  finely  ground,  is  known  as  smalts.  The  best  sort,  i.e.,  that  richest  in  cobalt,  is 
called  king's  blue.  According  to  Ludwig  it  contains  : — 

Norwegian.  German. 

Couleur.  Eschel.  Coarse. 

Si     .         .         .         .         .     70-86  ...  66-20         ...  72-11 

Co    .         .         .         .         .       6-49  ...  6-75         ...  1-95 

K  and  Na         .         .         .     21-41  ...  16-31         ...  i'8o 

A120S        ....       0-43  ...  8-64         ...  20-04 

It  contains,  besides,  small  quantities  of  ferrous  and  nickelous  oxide,  lime,  arsenic 
flcid,  carbonic  acid,  and  water,  sometimes  also  lead.  Soda  cannot  be  used  in  place  of 
potash  in  the  manufacture  of  smalts,  as  soda  cobalt  glasses  have  not  a  pure  colour. 

Smalts  are  used  for  blueing  paper,  linen,  and  starch,  and  for  colouring  and  paint- 
ing on  glass  and  porcelain,  and  for  enamels. 

Cobalt  Speiss. — As  in  roasting  cobalt  ores  the  heat  is  not  prolonged  sufficiently 
to  oxidise  the  nickel  present  in  the  ores,  it  melts  with  the  other  metals  and  the 
ansenic  to  a  white  mass,  with  a  reddish  cast,  a  strong  metallic  lustre,  and  a  finely 
granular  fracture.  It  consists  of  40  to  56  parts  of  nickel,  26  to  44  of  arsenic,  along  with 
copper,  iron,  bismuth,  and  sulphur. 

Cobalt  Ultramarine. — This  substance,  also  known  as  Thenard's  blue,  is  a  pigment 
consisting  of  alumina  and  protoxide  of  cobalt.  Curiously  enough,  this  pigment  has 
been  discovered  and  prepared  at  three  several  periods  and  localities  by  different  people ; 
first  by  Wenzel,  at  Freiberg,  Saxony ;  next  by  Gahn,  at  Fahlun,  Sweden ;  and  lastly, 
simultaneously  at  Paris  and  Vienna,  by  Thenard  and  von  Leithener.  The  pigment  is 
prepared  either  by  mixing  solutions  of  alum  and  a  salt  of  protoxide  of  cobalt,  pre- 
cipitating the  mixture  by  a  solution  of  carbonate  of  soda ;  or  by  the  decomposition  of 
aluminate  of  soda  by  means  of  chloride  of  cobalt.  The  ensuing  precipitate,  consisting 
of  an  intimate  mixture  of  hydrate  of  alumina  and  hydrate  of  protoxide  of  cobalt,  is 
first  well  washed,  then  dried,  and  heated  for  some  time.  The  pigment  thus  produced 
is,  when  seen  in  daylight,  of  course  after  pulverisation,  very  similar  to  ultramarine, 
but  by  artificial  light  its  colour  is  a  dirty  violet.  It  is,  however,  not  acted  upon  by 
acids,  as  distinguished  from  artificial  ultramarine ;  neither  is  it  affected  by  alkalies  nor 
heat,  as  is  copper  or  mineral  blue.  Cobalt  ultramarine,  chiefly  under  the  denomination 
of  Thenard's  blue,  is  employed  as  a  paint  in  oil-  and  water-colours,  and  also  for  staining 
glass  and  porcelain. 

Cceruleum  is  a  pigment  prepared  in  England,  exhibiting  a  bright  blue  colour, 
not  changing  in  artificial  light,  and  consisting  of  stannate  of  protoxide  of  cobalt 
(SnO2,CoO),  mixed  with  stannic  acid  and  gypsum  in  the  proportions,  in  100  parts,  of 
49-6  of  oxide  of  tin,  i8'6  protoxide  of  cobalt,  31-8  gypsum.  This  pigment  is  not 
affected  by  heat,  or  the  action  of  dilute  acids  and  alkalies ;  nitric  acid  dissolves  the 
protoxide  of  cobalt,  leaving  the  other  ingredients,  from  which  the  gypsum  may  be 
cleared  by  water. 

Rinmann's,  or  Cobalt  Green. — This  substance,  also  known  as  cobalt  green,  zinc 
green,  and  Saxony  green,  is  a  compound  similar  to  the  cobalt  ultramarine,  for  the 
alumina  of  which  oxide  of  zinc  is  substituted.  This  green  is  prepared  by  mixing  a 
solution  of  white  vitriol  with  a  solution  of  a  salt  of  protoxide  of  cobalt,  precipitating 
by  carbonate  of  soda,  and  washing,  drying,  and  heating  the  precipitate.  This  pigment 


SECT,  ii.]  NICKEL.  J47 

when  pure  contains  88  per  cent,  of  oxide  of  zinc  and  1 2  per  cent,  of  protoxide  of  cobalt. 
It  is  not  affected  by  strong  heat,  tinges  the  borax-bead  blue,  dissolves  in  warm  hydro- 
chloric acid,  forming  a  blue  colour,  which,  upon  water  being  added,  becomes  a  pale  red. 
Treated  with  caustic  potassa,  the  oxide  of  zinc  is  dissolved,  and  may  be  detected,  after 
previous  dilution  with  water,  by  the  addition  of  a  solution  of  sulphuret  of  potassium. 

Pure  Protoxide  of  Cobalt. — This  substance  is  occasionally  employed  for  the  pre- 
paration of  fine  colours.  It  may  be  obtained  by  heating  one  part  of  previously 
roasted  and  finely  pulverised  cobalt  ore  with  two  parts  of  sulphate  of  potassa  until  no 
more  sulphuric  acid  is  given  off.  The  fused  mass,  consisting  of  sulphate  of  potassa, 
sulphate  of  protoxide  of  cobalt,  and  insoluble  arsenical  salts,  is,  when  cooled,  first 
treated  with  water,  and  next  digested  with  hydrated  protoxide  of  cobalt  to  precipitate 
any  iron  which  may  happen  to  be  present,  and  in  order  to  eliminate  the  oxide  of  that 
metal  the  solution  is  filtered.  It  is  next  precipitated  with  carbonate  of  soda,  and, 
finally,  the  precipitate  is  washed  and  heated. 

Nitrite  of  Protoxide  of  Cobalt  and  Potassa. — This  double  salt,  known  by  its 
trade  name  of  cobalt  yellow,  is  obtained  by  mixing  a  solution  of  protoxide  of  cobalt 
with  nitrite  of  potassa;  it  is  a  yellow  crystalline  precipitate,  perfectly  insoluble  in 
water.  M.  Saint-Evre  first  investigated  this  body,  and,  struck  with  its  beautifully 
yellow  colour,  quite  like  that  of  purrhee  (euxanthinate  of  magnesia),  and  with  the 
fact  that  cobalt  yellow  resists  oxidising  and  sulphuretting  influences,  suggested  its 
applicability  to  artistic  purposes.  He  prepares  this  pigment  by  precipitating  with  a 
slight  excess  of  potassa  the  double  salt  of  protoxide  of  cobalt  and  potassa,  obtaining  a 
rose-red-coloured  protoxide  of  cobalt  and  potassa.  Into  this  thickish  magma  deutoxide 
of  nitrogen  gas  is  passed.  According  to  Hayes,  this  pigment  is  readily  obtained  by 
causing  the  vapours  of  hyponitric  acid  to  pass  into  a  solution  of  protonitrate  of  cobalt, 
to  which  some  potassa  has  been  added  ;  the  whole  of  the  cobalt  is  then  converted  into 
cobalt  yellow.  As  the  nitrite  of  protoxide  of  cobalt  and  potassa  can  be  obtained  even 
from  impure  solutions  of  protoxide  of  cobalt,  so  as  to  be  quite  free  from  any  nickel,  iron, 
&c.,  the  use  of  this  preparation  of  cobalt  is  preferable  for  glass  and  porcelain  staining 
when  a  pure  blue  is  required. 

Cobalt  Bronze. — This  substance,  a  double  salt  of  phosphate  of  protoxide  of  cobalt 
and  ammonia,  prepared  at  Pfannenstiel,  near  Aue,  in  Saxony,  has  been  but  lately 
brought  into  commerce.  It  is  a  violet-coloured  powder,  very  much  like  the  violet- 
•coloured  chloride  of  chromium,  and  exhibits  a  strong  metallic  lustre. 


NICKEL. 

Nickel  occurs  in  the  following  ores  : — Kupfer  nickel,  NiAs,  antimony  nickel,  NiSb, 
diosmose,  NiAs3,  and  especially  in  the  nickeliferous  varieties  of  speiss  cobalt,  nickel 
pyrites,  NS,  and  nickel-antimony  glance,  NiS2  +  Ni  (SbAs2).  In  New  Caledonia  occurs 
garnierite  (pimelite  or  numeite),  a  nickel  magnesium  hydrosilicate  (containing  n  to 
1 6  per  cent,  of  nickel),  at  present  the  most  important  ore  of  nickel.  At  Rewdansk,  in 
the  Ural,  there  is  found  rewdanskite,  a  hydrated  nickelous  silicate.  Often  magnetic 
pyrites  and  iron  pyrites  yield  nickel,  as  does  the  cobalt-speiss  of  the  blue  colour  works, 
and  certain  products  obtained  in  copper  works— e.g.,  nickel  vitriol — nickel  is  found  in 
many  kinds  of  pyrolusite  and  in  some  magnetic  irons.  It  was  formerly  obtained  in 
England  from  the  residues  of  the  chlorine  stills.  According  to  Gerland,  i  ton  of  pyro- 
lusite yielded  on  an  average  2'5  kilos,  of  nickel  and  5  kilos,  of  cobalt. 

A  concentrative  treatment  has  to  precede  the  smelting  of  nickel  ores.  If  nickel  is 
present  as  a  sulphide,  iron  pyrites  are  used  for  concentration;  if  the  nickel  is  an 
arsenide,  arsenic  is  employed.  The  product  is  in  the  former  case  matte,  in  the  latter 
speiss.  From  these  nickeliferous  products  metallic  nickel  or  its  alloy  with  copper  is 


148  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

obtained,  either  in  the  dry  or  the  wet  way.     Hence  the  metallurgy  of  nickel  is  resolved 
into — 

(I.)  The  concentration  fusions,  which  aim  at  the  accumulation  of  the  nickel  present 
in  an  ore,  either  (a)  in  matte,  (6)  in  speiss,  or  (c)  in  black  copper ; 

(II.)  In  the  elimination  of  nickel  or  its  alloy  from  the  products  of  the  concentration 
fusions,  which  may  be  effected  in  the  dry  or  the  wet  way. 

Since  it  has  been  understood  that  by  preparing  nickel-copper  alloys  the  most  valu- 
able properties  of  nickel — its  white  colour  and  its  resistance  to  chemical  reagents — are 
masked,  it  is  preferred  to  prepare  pure  nickel. 

The  concentration  fusion  of  nickel  ores  is  especially  applicable  if  they  occur  among 
iron  pyrites.  The  ferric  oxide  produced  by  smelting  the  partially  roasted  ores  with 
quartz,  or  substances  rich  in  silica,  is  chiefly  slagged  whilst  the  nickel,  which  is  also 
oxidised,  but  which  is  more  readily  reduced  than  ferric  oxide,  becomes  metallic,  and 
collects  in  the  matte  formed  from  the  undecomposed  sulphides  and  the  reduced  sul- 
phates. If  the  ore  contains  also  copper,  it  concentrates  in  the  matte  more  completely 
than  does  the  nickel.  If  too  much  ferrous  oxide  is  present,  a  part  of  it  is  reduced  to 
metallic  iron  in  contact  with  charcoal,  and  is  either  taken  up  in  the  matte  or  separates 
out  as  nickeliferous  pig  iron.  An  improved  result  is  obtained  if  the  matte  is  concen- 
trated in  a  reverberatory  with  the  addition  of  quartz,  heavy  spar,  and  charcoal,  forming 
barium  sulphide.  This  liberates  baryta,  and  sulphurises  the  oxidised  nickel  and  copper 
contained  in  the  charge,  whilst  the  baryta  combines  with  the  quartz  and  the  ferrous 
oxide  to  form  a  very  fusible  slag. 

At  the  Isabella  Works  at  Dillenburg  a  nickeliferous  sulphur  and  copper  pyrites, 
containing  on  an  average  7*5  per  cent,  ofnickel,  is  first  roasted,  broken  up  with  coke, 
fused,  roasted  again,  and  finally  smelted  with  the  addition  of  slags,  to  form  concentration 
matte.  In  order  to  diminish  the  iron  and  yet  leave  so  much  sulphur  that  the  matte 
may  be  brittle  and  break  easily,  it  is  melted  before  the  blast  on  the  hearth,  forming  a 
refinery  matte,  from  which  nickel  or  a  nickel  alloy  may  be  produced  in  the  wet  way. 

The  methods  hitherto  devised  for  obtaining  nickel  in  the  dry  way  have  not  given 
fully  satisfactory  results.  In  the  wet  way  the  first  step  is  generally  to  roast  the  ores 
or  the  nickeliferous  furnace  products  in  order  to  convert  the  iron  present  into  an 
iron  oxide  soluble  in  acids,  and  to  render  the  nickel,  copper,  and  cobalt  soluble 
either  in  water,  as  sulphates,  or  in  acids,  as  oxides  or  basic  salts.  From  the  solution  the 
nickel  is  thrown  down  as  oxide  or  as  sulphide,  and  from  the  precipitate  metallic  nickel 
or  the  alloy  of  copper  and  nickel  is  obtained. 

The  wet  process  for  nickel  consists  of — 

(i)  The  preparation  of  the  solution  of  nickel.  If  nickeliferous  mattes  are  roasted, 
there  are  first  formed  the  sulphates  of  the  four  metals  iron,  copper,  nickel,  and  cobalt, 
which,  at  increasing  temperatures,  are  decomposed  at  different  degrees  of  heat :  ferrous 
and  ferric  sulphate  the  most  easily,  and  cobalt  sulphate  with  the  greatest  difficulty. 
From  the  roasted  mass  the  chief  part  of  the  nickel  and  cobalt  are  dissolved  out  in 
water,  as  is  also  a  little  copper,  whilst  the  iron  and  a  part  of  the  copper  with  a  little 
nickel  and  cobalt  remain  undissolved.  From  the  residue,  cuprous  and  nickelous  oxides 
may  be  extracted  by  acids.  If  the  roasted  mass  is  at  once  treated  with  hydrochloric 
acid,  copper  oxide  is  dissolved  rather  than  nickelous  oxide,  and  nickelic  and  ferric 
oxides  may  be  extracted  from  the  residue  by  hot  concentrated  acids. 

From  speiss  arsenic  may  be  removed  and  the  nickel  dissolved  by  igniting  the  roasted 
speiss  with  a  mixture  of  soda-saltpetre  and  soda,  extracting  the  sodium  arseniate  with 
water,  treating  the  residue  with  sulphuric  acid,  when  nickel  and  cobalt  sulphates  are 
dissolved  and  ferric  oxide  is  left.  According  to  Wbhler's  proposal,  the  arsenic  can  be 
removed  as  a  sulpho  salt  by  melting  the  speiss  with  sodium  sulphide  and  lixiviating  the* 
mass. 


SECT,  ii.]  NICKEL.  149 

(2)  The  nickel  is  thrown  down  from  the  solution  by  fractionated  precipitation  with 
chalk,  which  separates  first  iron  and  arsenic  and  then  copper,  so  that  only  nickel 
remains  in  solution,  and  is  thrown  down  by  means  of  milk  of  lime,  free  from  iron.    At 
Joachimsthal  the  copper  is  removed  from  the  acid  solution  by  means  of  sulphuretted 
hydrogen,  the  nickel  is  precipitated  by  potassium  bisulphate  in  the  state  of  sparingly 
soluble  potassium  nickel  sulphate,  when  cobalt,  free. from  nickel,  remains  in  solution, 
and  can  be  thrown  down  by  sodium  carbonate. 

(3)  The  conversion  of  the  nickel  precipitate  into  metallic  nickel  or  copper  nickel 
can  be  effected  thus  : — The  hydrated  nickelous  oxide  precipitated  from  the  solution  of 
the  metal  by  lime-water  is  separated  by  filtration  and  pressing  so  that  it  may  be  dried. 
When  dry,  the  precipitate  is  ground  up  with  water,  and  washed  with  water  containing 
hydrochloric  acid  until  all  gypsum  is  removed ;  the  pure  nickelous  oxide  stamped  to  a 
stiff  paste  with  rye-meal  and  beetroot  treacle,*  and  cut  into  cubes  of  1*5  to  3  centi- 
metres in  diameter.     These  cubes  are  dried  rapidly  and  reduced  to  metal  by  heating 
strongly  in  crucibles  or  upright  fire-clay  cylinders.     This  is  easily  effected  in  one  and  a 
half  hour,  but  pure  nickel  requires  three  hours  of  an  intense  white  heat.    Since  the  intro- 
duction of  galvano-nickeling,  nickel  is  met  with  in  commerce  in  ingots  of  great  purity. 

L.  Mond  has  devised  the  following  process  for  obtaining  pure  nickel.  He  finds  that 
the  liquid  and  volatile  compound  of  Ni  and  oxide  of  carbon  has  not  a  corresponding 
Co  compound.  On  passing  the  vapour  of  this  liquid  through  a  red-hot  tube,  the  nickel 
is  deposited  alone. 

The  New  Caledonian  nickel  ores  which  are  now  the  chief  material  of  the  French 
nickel  industry,  consists  of  fine  green  hydrosilicates,  and  are  free  from  arsenic  and  sulphur 
and  poor  in  copper  and  cobalt.  In  consequence  of  the  difficulty  of  working  these  ores  in 
the  dry  way,  Christofle  treats  them  with  hydrochloric  acid,  and  precipitates  the  nickel 
alone  as  oxalate,  which  is  calcined  in  crucibles.  On  account  of  the  high  price  of  oxalic 
acid,  it  is  better  to  precipitate  ferric  oxide  and  alumina,  and  then  nickel  as  oxide  or 
sesqui-oxide,  but  the  removal  of  the  sulphuric  acid,  introduced  along  with  the  commercial 
hydrochloric  acid,  is  difficult.  The  nickel  thus  obtained  is  very  pure.  Riche  found  in 
it  9775  nickel,  1*25  carbon,  0*54  silicon,  and  0*36  manganese.  Subsequently  Christofle 
has  introduced  a  mixed  process :  he  separates  the  ore  as  well  as  possible  from  ferric 
oxide  in  the  wet  way,  and  then  reduces  the  purified  ore  in  the  dry  way. 

Samples  of  cast  nickel  have,  according  to  Gard,  the  following  composition  : — 
C         .        .    0-530  ...  i -104  ...  1-900 

Si         .        .    0-303  ...  0-130  ...  0-255 

Fe        .        .     0-464  ...  0-108  ...  0-301 

Co        .         .     0.446  ...  trace  ...  trace 

S  .        .     0-049  •••  0-266  ...  0-104 

Ni         .         .  98-208  ...  98-392  ...  97  -440 


loo-ooo  ...          loo-ooo  ...          loo-ooo 

Nickel  is  almost  silver  white,  with  a  faint  yellowish  cast,  very  infusible,  extensible, 
and  capable  of  taking  a  polish.  Its  specific  gravity  is  8*97  to  9-26.  When  pure  it  may 
be  forged,  rolled,  and  drawn  to  wire.  The  tenacity  of  nickel  to  that  of  iron  is  as  9  to  7. 
It  has  a  considerable  resemblance  to  iron,  but  is  distinguished  by  its  greater  resistance 
to  chemical  agents.  Hence,  it  is  suitable  for  crucibles  and  other  laboratory  implements. 
On  account  of  its  silvery  colour  and  its  resistance  to  the  action  of  air,  water,  and  many 
acids,  it  is  used  for  the  manufacture  of  alloys  resembling  silver.  It  is  a  constituent  of 
the  smaller  coins  in  Germany,  the  United  States,  Brazil,  &c.  It  serves  also  for  coating 
other  metals.  Its  porosity  and  crystalline  texture,  when  melted  on  the  large  scale,  can 
be  removed  by  the  addition  of  o-i  per  cent,  of  magnesium.  At  a  white  heat  nickel 
may  be  welded  with  steel  and  iron. 

*  The  latter  article  is  not  fit  for  human  consumption. 


1 5o  CHEMICAL   TECHNOLOGY.  [SECT.  n. 


COPPER. 

Copper,  one  of  the  most  common  metals,  was  known  in  prehistorical  ages.*  The 
Greeks  and  Romans  obtained  this  metal  chiefly  from  Cyprus,  whence  the  name  cuprum. 
It  occurs  sometimes  native,  but  more  commonly  as  oxide  and  sulphide. 

Copper  Ores. — Metallic  or  native  copper  occurs  in  quantity  near  Lake  Superior, 
where,  in  1857,  a  mass  was  found  weighing  450  tons,  and  measuring  13*75  metres  in 
length,  by  6-7  in  breadth,  and  z"j  in  thickness.  It  is  also  found  in  Peru,  Bolivia,  and 
Chili,  from  which  last  country  it  is  brought  to  England  under  the  names  of  copper 
sand  and  copper  barilla  (!),  containing  60  to  80  per  cent,  of  copper,  and  20  to  40  percent, 
of  quartz. 

Red  Copper  Ore,  ruberite,  or  ruby  copper,  C\i2O,  is  found  crystalline  in  regular 
octohedra  as  well  as  massive  and  diffused.  It  occurs  in  Cornwall  and  in  large  quan- 
tities in  the  Burraburra  mine  in  South.  Australia.! 

Tile  ore  is  an  intimate  mixture  of  cuprous  oxide  with  iron  ochres. 

Azurite  (cuprazurite,  copper  lazulite,  or  azure  malachite),  2CuC03.Cu(OH)2,  is  found 
in  beautiful  blue  crystals  as  well  as  massive  and  diffused.  It  is  found  in  Cornwall,  at 
Chessy  formerly,  and  in  South  Australia. 

Malachite  (a  green  copper  carbonate),  CuC03.Cu(OH)2,  occurs  in  oblique  rhombic 
crystals,  or  stalactitic  and  fibrous  (Atlas  ore),  or  massive  (copper  green),  generally 
mixed  with  azurite  (Ural,  South  Australia,  Canada). 

Chalkosine  (vitreous  copper,  copper  glance),  Cu2S,  and  phillipsine,  or  purple  pyrites, 
3Cu2S.Fe2S3,  and  copper  pyrites,  CuFeS2,  are  the  most  important  sulphur  compounds 
used  for  the  extraction  of  copper.  Copper  pyrites  is  often  accompanied  with  iron 
pyrites,  arsenical  pyrites,  and  fahl  ore  (grey  copper),  and  also  with  silver,  gold,  and 
nickel. 

Copper  slate  is  a  bituminous  marly  slate  finely  interspersed  with  sulphuretted 
copper  ores.  It  occurs  chiefly  at  Mansfeld,  at  Stollberg  in  the  Hartz,  and  at  Riechels- 
dorf  in  Hessia. 

Enargite,  Cu3AsS4,  is  found  at  Manilla,  in  Peru,  and  in  Hungary. 

The  Fahl  ores  (grey  copper)  are  composed  of  copper  sulphide  with  silver  sulphide, 
accompanied  with  arsenic  and  antimony  sulphides.  On  account  of  the  presence  of 
silver,  they  of  ten  rank  among  silver  ores.  They  contain  14  to  41*5  per  cent,  of  copper. 

Atakamite,  3Cu(OH)2.CuCl2,  contains  56  per  cent,  of  copper.  It  is  found  in  Chile 
and  other  parts  of  the  west  coast  of  South  America,  as  also  in  South  Australia,  and  is 
worked  at  Swansea.  When  ground  to  powder,  it  is  brought  from  Peru  under  the 
name  "  arsenillo,"  and  is  used  for  sprinkling  sand  (to  take  up  ink). 

Several  atakamites  contain  iodine  as  copper  iodide.  Since  1869  important  quantities 
of  copper  have  been  obtained,  in  the  wet  way,  from  the  burnt  copper  pyrites,  the  refuse 
of  the  sulphuric  acid  manufacture. 

Copper  is  obtained  from  its  ores  either  by  the  dry  or  the  wet  way. 

In  spite  of  concentration,  it  is  rarely  practicable  to  enrich  copper  ores  so  that 
they  yield  on  smelting  more  than  8  to  10  per  cent,  of  copper.  Only  pyritic 
ores  are  prepared  by  roasting.  When  the  ores  to  be  roasted  consist  essentially  of 
copper  pyrites,  and  are  strongly  contaminated  with  iron  pyrites  (sulphur  ore),  the 
attempt  is  made  to  utilise  a  part  of  the  escaping  sulphur,  and  to  concentrate  the  copper 
(which  often  forms  not  more  than  3  to  4  per  cent,  of  the  mixture)  by  means  of  nucleus 
roasting.  If  a  mixture  of  sulphur  ore  with  a  little  copper  ore  is  roasted,  the  copper 

*  It  seems  to  have  been  used  for  tools  and  weapons  prior  to  bronze,  and,  of  course,  before  iron, 
t  It  is  also  found  at  Chessy,  in  France,  along  with  copper  carbonate,  in  the  Bannat,  and  in 
Siberia  in  primitive  rocks. 


SECT,  ii.]  COPPER.  151 

retires  into  the  middle  of  the  lumps,  whilst  the  outer  coating,  which  can  easily  be 
removed  by  mechanical  means,  consists  of  loose  iron  oxides  very  poor  in  copper.* 

In  certain  cases  the  roasting  is  intended,  not  merely  to  expel  sulphur,  but  to  burn 
off  the  bitumen  with  which  some  ores  are  interpenetrated — e.g.,  the  bituminous  copper 
shales.  The  fluxes  in  copper  smelting  are  added,  not  only  to  make  the  charge  more 
fusible,  but  to  promote  the  separation  of  the  iron  from  the  copper  oxide. 

(A)  Production  of  Copper  in  the  Dry  Way. — In  pyritic  ores  this  process  is  effected 
either  in  shaft  furnaces  or  in  reverberatories.  In  the  latter  the  reduction  of  the 
copper  oxide  is  effected  by  the  sulphur  itself.  Thus  the  copper  is  more  and  more 
concentrated  in  the  matte,  until  it  is  possible  to  proceed  to  the  decomposition  of  the 
last  portions  of  the  sulphides.  This  decomposition  is  conducted  by  roasting  the  concen- 
trated ore  and  its  simultaneous  smelting,  whereon  the  air  can  have  free  access  until 
the  sulphur  is  entirely  eliminated.  There  is  then  always  a  formation  of  cuprous 
oxide,  so  that  the  purified  copper  is  in  the  state  known  as  "  overdone."  In  melting 
copper  ores  in  shaft  furnaces  the  same  process  is  followed,  of  first  concentrating  the 
copper  in  a  "copper  matte ;"  but  the  reduction  of  the  copper  oxide  after  roasting  is 
effected  by  means  of  charcoal,  with  which  the  charge  of  the  shaft  furnace  is  inter- 
stratified.  In  shaft  furnaces  the  product  is  never  overdone  or  contaminated  with 
cuprous  oxide,  but  always  carboniferous  copper.  Consequently,  malleable  copper 
is  obtained  neither  by  means  of  the  shaft  furnace  nor  the  reverberatory,  but  the 
means  for  rendering  it  fit  to  bear  the  hammer  are  completely  different  in  the  two 
cases. 

The  treatment  of  pyritic  ores  in  shaft  furnaces  consists  in  roasting  the  ores, 
whereby  a  part  of  the  sulphur,  antimony,  and  arsenic  is  volatilised ;  a  part  of  the 
metals  present  is  converted  into  sulphates,  arseniates,  and  antimoniates ;  whilst  a  part 
of  the  ore  escapes  roasting.  In  smelting  the  roasted  mass  with  the  addition  of  sub- 
stances which  form  slag,  the  copper  oxide  is  first  converted  to  metallic  copper ;  whilst 
the  sulphates  are  again  reduced  to  sulphides,  which,  with  the  metallic  copper  and  the 
sulphides  remaining  undecomposed,  form  a  richer  crude  matte  (copper  matte) ;  whilst  a 
speiss  (antimonide  and  arsenide)  is  formed  by  the  reduction  of  the  existing  metallic 
arseniates  and  antimoniates.  The  remaining  metallic  oxides,  especially  ferrous  oxide, 
formed  by  reduction,  combine  with  the  fluxes  to  form  slag. 

By  repeating  the  roasting  and  reducing  processes  there  is  ultimately  obtained, 
along  with  a  small  quantity  of  matte,  metallic  copper  (crude  or  black  copper)  contami- 
nated with  foreign  metals,  from  which  it  is  freed  by  an  oxidising  fusion,  in  which  the 
foreign  metals  are  partly  volatilised  as  oxides  and  partly  taken  up  in  the  slag.  The 
finished  copper  (rosette  copper,  disc  copper)  contains,  as  the  roasting  process  has 
generally  been  carried  too  far,  cuprous  oxide,  by  which  its  malleability  is  decreased. 
By  a  rapid  reducing  fusion,  and  by  remelting  upon  a  hearth  between  charcoal,  the 
cuprous  oxide  is  reduced,  and  there  is  formed  malleable  copper. 

The  crude  smelting  of  the  roasted  ores  to  form  crude  matte  (copper  matte)  is  effected 
in  cupola  furnaces.  Fig.  157  shows  the  section  of  the  cupola  furnace,  and  Fig.  158  its 
front  elevation,  with  a  removal  of  the  front  wall,  to  show  the  interior  arrangements. 
Fig.  159  shows  the  interior  of  the  furnace.  Through  the  apertures,  t,  there  pass  the 
tuyeres  of  the  blast.  The  liquid  contents  of  the  furnace  flow  through  the  two  aper- 
tures, o  (eyes),  situate  above  the  sole,  and  two  short  channels  into  the  two  depressed 
basins,  C.  As  the  roasted  copper  ore  always  contains  iron  oxide,  a  simply  reducing 
fusion  might  readily  reduce  the  iron.  To  prevent  this,  substances  capable  of 
forming  slag  (quartz  or  silicates)  are  added,  so  that  the  iron  oxide,  when  reduced 
to  the  ferrous  state,  combines  with  the  silica  present  to  yield  a  readily  fusible  slag. 

*  When  the  sulphur  amounts  to  30  per  cent,  or  upwards,  the  ores  should  always  be  roasted  in 
kilns,  not  merely  to  utilise  the  sulphur,  but  to  obviate  the  nuisance  of  escaping  sulphur  dioxide. 


152 


CHEMICAL  TECHNOLOGY. 


[SECT.  n. 


The  cupric  and  cuprous  oxide  formed  are  reduced  to  metallic  copper  by  the  iron 
sulphide  present— (^CuO  +  FeS  =  SO,  +  FeO  +  jCu). 

During  the  formation  of  slag,  sulphides  separate  out,  and  collect  in  the  lower  part 


Fig.  157- 


Fig.  158. 


m  m-mm  w  KM  aM" 
nfi  tnnn  tnnn  innnn  m||Ji8'nnn  iui!iiimin_ni"H'n 


Fig.  159- 


of  the  furnace  as  copper  matte  (crude  matte),  amixture  of  copper  sulphide,  iron  sulphide, 
and  other  sulphides,  containing  on  an  average  32  percent,  of  copper.  The  slag  formed 
at  the  same  time  is  the  crude  slag. 

The  roasting  of  the  copper  matte  is  to  effect  its  complete  oxidation  and  the  removal 
of  the  sulphur  present.  The  matter  resulting  is  melted  in  a  cupola  furnace  with  an 
addition  of  slag,  a  process  known  as  concentration  work.  The  product  is  the  concen- 
tration matte,  containing  about  50  per  cent,  of  copper ;  it  is  thoroughly  roasted  off  and 
melted  to  black  copper.  If  silver  is  present  this  is  extracted  prior  to  any  further  treat- 
ment. This  was  effected  formerly  by  amalgamation,  but  at  present  by  the  Ziervogel 
process  (see  SILVER),  if  it  is  not  preferred  to  separate  the  silver  from  the  copper  by  the 
eliquation  process  with  lead. 

In  richer  copper  ores  the  concentration  work  is  dispensed  with,  and  the  thoroughly 
roasted  copper  matte  is  smelted  at  once  as  black  copper  (crude  copper,  yellow  copper). 
This  takes  place  in  cupola  furnaces  of  less  height  than  those  used  for  smelting  the 
roasted  ores.  The  sulphur  of  the  matte  has  been  so  much  diminished  by  roasting  that 
it  can  no  longer  take  up  the  reduced  copper.  It  separates  out  (along  with  a  small 
quantity  of  matte)  as  black  copper,  with  93  to  95  per  cent,  of  copper.  Black  copper 
from  Mansfeld,  according  to  Flach  (1866),  contained : — 


Copper          . 

Lead    . 

Zinc 

Iron 

Nickel  and  Cobalt 

Silver  . 

Sulphur 


93 '49 
i '49 
1-47 
1-03 
1-25 
0-03 
0-99 

9975 


The  black  copper,  or  crude  copper,  is  freed  from  impurities  (sulphur  and  foreign 
metals)  by  a  powerfully  oxidising  fusion,  as  the  impurities  are  slagged  more  rapidly 
than  the  copper.  This  process — the  finishing  or  cooking  the  black  copper — is  carried 
out  (i)  in  a  small  finishing  hearth,  (2)  in  a  large  hearth  or  speiss-furnace,  or  (3)  in  a 
draught  flame  furnace  or  refining  furnace. 

The  finishing  hearth  is  shown  in  section  in  Fig.  160,  and  in  elevation  in  Fig.  161. 
The  hearth  consists  of  masonry,  on  the  upper  surface  of  which  is  a  hemispherical 
depression,  a,  the  hearth-pit  with  a  cast-iron  covering  plate,  6.  Black  copper  is  melted 
down  with  the  addition  of  charcoal,  using  the  blast,  h. 


SECT.    11.  J 


COPPER. 


'53 


Sulphur,  ars'enic,  and  antimony  are  volatilised ;  ferric  oxide  and  the  other  non 
volatile  oxides,  along  with  cuprous  oxide,  separate  out  as  slag  in  combination  with  silica 
from  the  mass  of  the  hearth,  and  collect  on  the  surface  of  the  copper,  where  it  is  drawn 
off  from  time  to  time.     When  the  copper  is  finished,  the  blast  is  turned  off,  the  surface  of 

Fig.  1 60.  Fig.  161. 


the  copper  freed  from  charcoal  and  slag,  and  cooled  by  sprinkling  with  small  coal  so  far 
that  it  may  be  chilled  superficially  by  means  of  water,  without  danger  of  an  explosion. 
There  is  thus  formed  a  thin  disk  (rosette),  which  is  lifted  off  and  immediately  quenched 
in  water  to  prevent  the  oxidation  of  the  copper.  Water  is  again  sprinkled  on,  and  another 
disc  lifted  off  until  the  hearth  is  almost  empty.  This  work  is  called  resetting,  and  the 
metal  obtained  is  rosette,  or  disc-copper.  This  operation  is  better  conducted  in  large 
blast-flame  furnaces.  The  melting-hearth,  A  (Fig.  162),  is  provided  with  a  fire-box,  I, 
and  apertures,  n,  for  the  blast.  When  it  is 
finished,  it  is  let  off  into  the  pan,  B,  and  there 
converted  into  rosettes  in  the  manner  already 
described.  As  in  this  method  the  fuel  is  com- 
pletely separated  from  the  metal,  the  copper  is  more 
completely  purified  than  in  the  small  hearth. 

Eliquation. — In  working  argentiferous  copper 
ores,  the  black  copper  before  refining  is  submitted 
to  liquation,  if  it  is  not  thought  preferable  to 
employ  the  Ziervogel  method  (see  SILVER).  This 
process  depends  on  the  principle  that  copper  and 
lead  may  be  fused  together,  but  they  do  not 
remain  combined  on  cooling.  There  is  formed  an  alloy  of  much  copper  with  little  lead, 
whilst  the  remaining  lead  separates  out.  The  separation  takes  place  chiefly  in  accord- 
ance with  specific  gravity,  the  lowest  stratum  being  argentiferous  lead.  If  the  liquid 
mass  is  allowed  to  cool  slowly,  the  lead  flows  out  in  combination  with  the  silver,  but  on 
rapid  cooling  there  is  formed  an  intimate  mixture  of  both  metals.  The  silver  is 
separated  from  the  lead  either  by  the  refining  process,  by  Pattinson's  process,  or  by 
means  of  zinc  (see  SILVER). 

Copper,  whether  refined  on  a  large  or  a  small  hearth,  generally  contains  cuprous 
oxide.  If  this  oxide  is  present  to  the  extent  of  1*1  per  cent.,  the  metal  is  so  deficient 
in  tenacity  and  malleability  that  it  cannot  be  forged  at  common  temperatures  without 
splitting  at  the  edges.  If  it  contains  1*5  cuprous  oxide  the  decrease  of  tenacity  is  per- 
ceptible, even  when  hot,  and  the  copper  is — both  cold  and  hot — short.  In  this  state  it  is 
said  in  Germany  to  be  "  overdone."  Such  copper  contaminated  with  cuprous  oxide  can 
only  recover  its  tenacity  by  the  reduction  of  the  oxide  in  order  to  become  malleable. 

The  great  wealth  of  Britain  in  coal — the  best  fuel  for  the  reverberatory  process — 
probably  first  led  to  the  idea  of  refining  copper  in  reverberatories  instead  of  shaft 
furnaces.  The  chief  English  copper-works  are  at  Swansea  ;  they  obtain  their  ore  from 
the  mines  of  Cornwall,  North  Wales,  Westmoreland,  the  adjoining  parts  of  Lancashire 
.  and  Cumberland ;  but  very  large  quantities  of  ores  imported  from  Australia,  Chile,  Peru, 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Cuba,  and  Norway  are  also  smelted.  There  are  also  copper  works  in  Anglesea,  Stafford- 
shire, and  South-west  Lancashire.  The  English  copper  ores  consist  chiefly  of  copper 
pyrites  accompanied  by  iron  pyrites,  also  stannine  and  arsenical  pyrites  and  gangue. 

The  chief  processes  of  the  English  system  of  copper  smelting  consist  of — (i)  Calcin- 
ing the  pyritic  copper  ores  ;  (2)  melting  the  roasted  ores  for  coarse  metal ;  (3)  roasting 
or  calcining  the  coarse  metal ;  (4)  preparation  of  the  concentrated  white  metal  by  melt- 
ing the  roasted  coarse  metal  with  richer  ores;  (5)  preparation  of  the  concentrated  blre 
metal  by  melting  the  calcined  coarse  metal  with  calcined  ores  of  a  medium  percentage 
of  copper ;  (6)  preparation  of  a  red  and  white  metal  by  smelting  the  slags  obtained  in 
the  previous  operations  ;  (7)  calcination  fusion  of  the  blue  metal  No.  5,  and  production 
of  white  extra-metal ;  (8)  calcination  fusion  of  the  white  extra-metal,  and  production 
of  the  concentrated  metal ;  (9)  calcination  of  the  ordinary  white  metal  and  the  cupri- 
ferous bottoms  for  the  production  of  blister  copper  (black  copper)  ;  (10)  refining  the 
blister  copper. 

The  fusion  of  the  calcined  ores  for  coarse  metal  is  conducted  in  the  smelting  furnace 
generally  used  at  Swansea,  and  shown  in  Fig.  163.  The  hearth  is  contracted  towards  its 

mouth, forming  a  kind  of 

'     l63'  tray.  The  object  of  smelt- 

ing the  coarse  metal  by 
the  reverberatory  process 
is  the  separation  of  the 
copper  from  the  gangue, 
and  from  a  part  of  the 
foreign  metallic  oxides 
contained  in  the  roasted 
ore  by  means  of  a  re- 
ducing and  dissolving 
fusion.  The  sulphur  is 
of  importance,  since  the 
undecomposed  sulphides 
during  fusion  decompose 
the  oxides  and  the  sul- 
phates. Ferric  oxide  and  iron  sulphide  are  first  converted  into  sulphur  dioxide  and 
ferrous  oxide,  the  latter  often  combining  with  the  silica  present  to  form  slag.  As  the 
heat  rises  the  copper  oxide  is  decomposed  by  the  iron  and  copper  sulphides  with  forma- 
tion of  ferric  oxide  and  metallic  copper,  the  latter  of  which  partly  dissolves  in  the 
coarse  metal,  and  is  partly  converted  by  the  ferric  cxide  into  cuprous  oxide,  which 
becomes  slagged  at  the  highest  temperature  of  the  furnace.  As  the  coarse  metal  and 
the  slags  are  brought  into  intimate  contact  in  the  fused  mass  by  means  of  constant 
stirring,  the  iron  sulphide  contained  in  the  coarse  metal  and  the  cuprous  oxide  contained 
in  the  slags  undergo  a  double  decomposition  into  copper  sulphide  and  ferrous  silicate, 
so  that  the  slagging  of  the  copper  is  almost  totally  prevented. 

The  calcination  of  the  coarse  metal  is  mostly  conducted  in  the  same  reverberatories 
which  serve  for  calcining  the  ores.  The  purpose  of  this  calcination  or  roasting  is 
chiefly  to  oxidise  the  iron  and  to  volatilise  a  part  of  the  sulphur.  A  certain  proportion 
of  sulphur  in  the  calcination  products  is  necessary,  since  otherwise  the  concentration 
could  not  be  effected  without  a  loss  of  copper. 

For  the  production  of  the  concentrated  white  metal  the  roasted  coarse  metal  is 
charged  along  with  rich  copper  ores,  which  contain  scarcely  any  iron  sulphide,  but 
copper  sulphide,  copper  oxide,  and  quartz  in  such  proportions  that  the  iron  pyrites  is 
oxidised  by  the  oxygen  of  the  oxides,  whilst  all  the  copper  coalesces  to  metal,  and  the 
iron  oxidised  to  the  ferrous  state  forms,  with  the  quartz,  ferrous  silicate.  The  smelting 


SECT.    II.] 


COPPER. 


'55 


is  conducted  similarly  to  that  of  coarse  metal.  The  concentrated  white  metal  formed! 
has  almost  the  same  composition  as  copper  glance  (Cu2S),  and  is  run  off  into  moulds  of 
sand. 

The  white  metal  is  melted  for  blister  copper.  The  metal  is  placed  on  the  sole  of  a 
furnace,  which  does  not  differ  from  the  smelting  furnace,  and  the  fire  is  allowed  to  act 
for  twelve  to  twenty-four  hours.  At  first  the  heat  must  not  reach  the  melting-point, 
but  it  is  raised  towards  the  end.  By  this  process  the  sulphur  is  removed  in  the  state 
of  sulphurous  acid,  and  at  the  same  time  the  impurities,  such  as  arsenic,  cobalt,  nickel, 
tin,  iron,  &c.,  are  removed  either  by  volatilisation  alone  or  by  oxidation  and  slagging. 
Meantime  the  cuprous  oxide  and  copper  sulphide  are  mutually  decomposed,  forming 
sulphur  dioxide  and  metallic  copper  (2Cu20  +  Cu2S  =  S02  +  6Cu).  The  melted  copper 
is  run  off  into  moulds,  and  is  covered  on  the  surface  with  black  bubbles,  whence  it& 
name,  blister  copper.  The  fracture  has  also  a  porous,  honeycombed  aspect.  Blister 
copper  is  already  moderately  pure  and  almost  free  from  sulphur,  arsenic,  and  foreign 
metals.  The  last  stage  of  the  English  process  is  refining  the  blister  copper,  which  is 
effected  on  the  sole  of  a  reverberatory.  The  heat  is  gentle  at  first,  to  complete  the 
oxidation.  After  about  six  hours  the  copper  is  in  flux.  When  it  has  been  all  melted 
down  into  the  sump,  and  the  furnace  is  at  a  strong  heat,  the  reddish  slag,  rich  in 
cuprous  oxide,  is  drawn  off.  The  surface  of  the  molten  copper  is  covered  with  charcoal 
powder,  and  a  wooden  stirring  rod,  generally  of  birch,  is  thrust  down  into  the  liquid 
metal.  The  object  of  this  operation — "  poling  " — is  the  reduction  of  the  cuprous  oxide 
by  means  of  the  gases  evolved  out  of  the  cuprous  oxide.  The  copper  is  then  malleable. 

For  refining  copper  in  the  United  States  the  native  metal  from  Lake  Superior  is 
almost  exclusively  used  in  the  three  works  at  Hancock,  Detroit,  and  Pittsburg.  Pure 
copper  and  rich  slag  are  obtained  in  a  reverberatory.  At  Detroit  and  Hancock  the 
refinery  slags  are  worked  up  in  shaft  furnaces  for  blister  copper  and  poor  slags.  The 
furnaces  used  at  Lake  Superior  and  Detroit,  each  for  10  tons  of  crude  copper,  are 
4-3  metres  in  length  ;  the  fuel  is  Ohio  coal,  giving  out  a  long  flame.  The  slag,  formed 
by  smelting  crude  copper  with  cupriferous  slags  and  limestone,  containing  mostly  from 
5  to  14  per  cent,  of  copper,  is  drawn  out  four  to  six  times,  and  finally  freed  from 
copper  in  a  reverberatory  or  a  shaft  furnace.  Five  slags  from  Pittsburg  had  the  fol- 
lowing composition : — 


j_ 

II. 

III. 

IV. 

V. 

Cu2O 

12*46 

"'43 

12  -OI 

1  2  -O2 

10-53 

Cu 

4-82 

4  '93 

5  '05 

5-80 

5  '44 

Oin  Ct 

I  '22 

1-24 

1-28 

1-46 

1-37 

Zn 

0'37 

0-56 

1-52 

075 

0'43 

Ni 

o-o6 

— 

0-47 

0-18 

0-08 

MnO 

0x15 

0-04 

0-15 

0-13 

O'I2 

A1A 

i57i 

14-52 

15-21 

14-48 

I5-36 

CaO 

I4-34 

1475 

1479 

i5'25 

11-81 

MgO 

4-07 

3  '99 

4-11 

3-90 

2'57 

Si02 

45  '32 

46-94 

45'Si 

44*66 

49'83 

100*42 

98-40 

100-40 

98-23 

97  '54 

The  copper  now  contains  about  0-72  per  cent,  of  oxygen.  It  is  further  heated  with 
access  of  air  through  the  arch,  through  the  ash-door  and  the  furnace  bridge,  and  it  is 
constantly  stirred.  The  slags  produced,  containing  from  12  to  40  per  cent,  of  copper, 
are  drawn  off  from  time  to  time  in  order  to  add  them  to  the  next  charge  along  with 
the  finery  slags,  until  the  copper  is  overdone,  containing  about  i  per  cent,  of  oxygen. 
It  is  now  refined  by  means  of  poling,  for  the  removal  of  the  oxygen,  the  surface  of  the 
metal  being  entirely  cleared  from  slag,  covered  with  charcoal  and  split  wood,  and  the 
pole  introduced.  Samples  are  taken  every  ten  or  fifteen  minutes  until  black  spots  are 


CHEMICAL  TECHNOLOGY. 


[SECT.  u. 


no  longer  seen  upon  the  fracture,  which  becomes  fibrous  and  of  a  silky  lustre.  At 
some  works  there  is  added  during  the  refining  0-05  to  0-07  of  lead,  especially  if  the 
copper  is  to  be  wrought  into  sheets,  and  the  pole  is  then  introduced  as  soon  as  the  lead 
distributed  over  the  surface  is  melted.  The  poling  is  effected  at  the  highest  possible 
temperature,  and  with  the  greatest  possible  exclusion  of  air.  Over-poling  renders  the 
copper  brittle,  light  yellow,  very  shining,  and  mirror-like.  Over-poled  copper,  appa- 
rently containing  carbon,  still  retains  oxygen.  In  presence  of  much  carbon  and  oxygen 
there  is  formed  carbon  dioxide,  which  renders  the  copper  porous.  The  withdrawal  of 
the  copper  (which  is  to  be  kept  covered  with  charcoal)  is  effected  with  a  flame  as 
neutral  as  possible,  samples  being  frequently  taken. 

Manhes  has  carried  out  Holvay's  proposal  to  work  copper  ores  in  the  Bessemer 
converter.  The  furnace  consists  essentially  of  a  horizontal  cylinder  of  sheet  iron,  A 
(Figs.  164  and  165),  lined  with  fire-proof  stones  acid  or  basic,  which  can  be  made  to 
revolve  on  its  axis  by  means  of  rollers.  The  external  apertures,  c,  of  the  wind-chest,  c?, 
are  opposite  to  the  air-pipes,  e,  and  can  be  closed  with  plugs.  At  F  there  enters  the 
flame,  which  may  be  supplied  from  any  kind  of  a  fire-box,  whilst  the  products  of  corn- 


Fig.  164. 


Fig.  165. 


A 


Fig.  166.      Fig.  167.     Fig.  168. 


Mstion  escape  at  G.  When  the  apparatus  is  sufficiently  heated  it  is  brought  up  to  the 
furnace  containing  the  melted  ore,  the  cylinder  is  turned  (the  arched  pieces,  K,  lying 
upon  the  rollers,  r)  by  means  of  the  handle,  IT,  which  catches  into  the  circle  of  teeth,  n, 
fixed  to  the  cylinder,  until  A  takes  the  position  shown  in  Fig.  166,  and  allows  the 
melted  metal  to  run  to  the  mouth,  H.  It  may  also  be  baled  in  with  a  ladle,  or  the 
fusion  may  be  effected  in  the  cylinder  itself  by  means  of  the  flame  striking  in  laterally. 
After  the  apparatus  is  sufficiently  filled  it  is  removed  to  a  fit  place  by  turning  the 
wheels,  R,  which  run  on  rails;  the  wind-chest  is  filled  with  compressed  air  or  gas, 
and  the  cylinder,  A,  is  placed  in  a  proper  position  (Figs.  167  and  168).  According  to 
the  action  intended,  the  air  flue,  w,  is  connected  with  the  recipient,  V,  so  that  the 
powdery  substances  which  it  contains  may  be  blown  into  the  liquid  mass.  By  suitably 
inclining  the  melting  furnace  the  slag,  and  afterwards  the  metal,  can  be  run  off 
(Fig.  169). 

For  working  crude  regulus,  it  is  run  into  the  heated  cylinder,  A,  from  an  ordinary 
fixed  smelting  furnace ;  the  cylinder  is  moved  to  the  proper  place  and  turned  until  the 
•current  of  air  passes  through  a  sufficiently  thick  stratum  of  the  liquid  mass.  The 


SECT,  ii.]  COPPER.  157 

oxygen  of  the  air  combines  with  the  sulphur,  forming  sulphurous  acid ;  and  with  the 
other  substances,  forming  oxides,  which  are  carried  with  the  gases  to  condensation 
chambers,  and  are  there  precipitated.  The  sulphurous  acid  can  be  passed  to  the  lead 
chambers  and  converted  into  sulphuric  acid.  Of  the  ferric  oxide  formed,  the  greater 
part  remains  in  the  bath,  and  would  soon  make  the  stone  lining  useless  if  silica  were 
not  constantly  blown  in.  Therefore,  when  the  current  of  air  begins,  the  recipient,  U, 
filled  with  silica,  is  connected  with  the  air-pipe.  As  the  more  oxidisable  substances 
escape  first,  there  remains  in  the  cylinder  only  copper  sub-sulphide,  which  may  be  plainly 
seen  by  the  colour  of  the  flame.  The  cylinder  is  then  turned  so  that  the  air  is  caused 
to  play  more  and  more  on  the  surface  of  the  metals.  From  this  moment  the  copper  is 
in  excess — as  the  sulphur  is  continually  being  burnt — and  separates  out  from  the  com- 
bination. The  copper,  by  reason  of  its  superior  density,  sinks  down  below  the  remaining 
copper  sub-sulphide,  and  the  tuyeres  are  gradually  so  raised  that  the  air  only  enters 
this  sub-sulphide,  which  is  thus  gradually  decomposed.  There  now  remains  in  the  cylinder 
merely  crude  copper,  which  is  run  out  or  can  serve  for  refining  copper  in  the  ordinary 
manner.  If  the  temperature  is  no  longer  sufficient,  the  cylinder  may  be  heated  afresh. 
If  it  is  noticed  during  working  that  all  the  iron  is  oxidised,  no  more  silica  is  blown  in. 
The  cylinder  is  turned  to  the  position,  Fig.  166,  and  the  slag,  if  sufficiently  liquid,  is 
run  out.  The  current  of  air  which  then  strikes  the  back  of  the  bath  on  the  surface 
drives  out  the  slag.  With  this  apparatus  very  poor  ores  can  be  worked  up,  and  refined 
copper  can  be  obtained. 

For  producing  copper  from  oxidised  ores,  they  are  smelted  down  with  coke  in  a 
cupola  furnace,  after  the  addition  of  the  fluxes  necessary  to  produce  an  easily  fusible 
slag  which  takes  up  no  copper.  The  blister  copper  is  then  refined,  and  is  introduced  in 
commerce  as  rosette  copper.  At  Chessy,  near  Lyon,  malachite,  azurite,  and  ruberite 
are  smelted.  There  is,  however,  a  considerable  loss  of  copper  by  slagging.  In  the 
Siberian  works  on  the  Ural,  sulphuretted  copper  ores  and  iron  pyrites  are  added  to 
the  oxidised  copper  ores.  The  copper  is  thus  protected  from  slagging  by  the  sulphur. 

(B)  Production  of  Copper  in  the  Wet  Way. — This  process  is  coming  more  and  more 
into  use.  The  great  ease  with  which  copper  is  dissolved  and  precipitated  from  its 
solutions  suggested  the  moist  way  for  obtaining  copper  when  the  dry  way  gave  no 
advantageous  results  on  account  of  the  poverty  of  the  ores,  or  when  it  was  desired  to 
utilise  intermediate  metallurgical  and  chemical  products. 

Cementation  consists  in  precipitating  copper  from  solutions  of  copper  sulphate 
(blue  vitriol,  blue  stone)  by  means  of  metallic  iron.  Such  waters  occur  in  nature  in 
cupriferous  districts.  The  metallic  copper  obtained  by  precipitating  such  solutions  with 
iron  is  known  as  cement  copper.  At  the  Amlwch  copper  works  in  Anglesea  the 
cement  water  is  stored  first  in  a  large  tank,  to  become  clarified  by  the  deposit  of  iron 
ochre,  and  is  then  run  into  the  cement  pits,  in  which  has  been  placed  scrap-iron,  &c., 
for  the  decomposition  of  the  copper  sulphate.  From  time  to  time  the  sediments  are 
stirred  up,  and  the  turbid  liquor,  with  all  the  deposit,  is  led  into  large  sumps,  in  which 
the  mud  is  deposited  and  dried  in  a  reverberatory  drying  furnace.  It  contains  as 
much  as  50  per  cent,  of  copper — on  an  average  30  per  cent. — the  chief  constituent 
being  basic  ferric  sulphate. 

Latterly  the  wet  way  for  obtaining  copper  has  been  extensively  used  for  the  treat- 
ment of  poor  ochre  and  pyritic  copper  ores,  weathered  pyrites,  and  burnt  ores  containing 
copper  pyrites.  In  general,  the  copper  cannot  be  at  once  extracted  by  water  or  acids 
from  ores  and  furnace  products,  but  preparatory  operations  are  needed.  In  cupriferous 
sulphur  ores  we  use  weathering  or  roasting  (both  oxidising  and  chlorising).  The  ores 
to  be  extracted  are  sometimes  sulphated  by  means  of  roasting-gases.  For  lixiviation 
there  are  used,  besides  water,  dilute  hydrochloric  or  sulphuric  acid,  solutions  of  ferric 
and  ferrous  chloride,  and  of  common  salt.  Other  solvents,  such  as  ammonia,  sodium 


CHEMICAL   TECHNOLOGY. 


[SECT.  ii. 


sulphite,  and  thiosulphate,  have  not  given  satisfaction.  The  precipitation  of  the 
copper  from  its  solutions  is  effected  either  by  iron,  or,  as  in  Norway  (Binding's 
process),  by  sulphuretted  hydrogen,  the  precipitated  sulphide  being  afterwards  con- 
verted into  copper  sulphate  or  metallic  copper. 

Cupreous  pyrites  (as  at  Duisburg),  after  having  given  off  their  sulphurous  acid  by 
roasting  (for  the  manufacture  of  sulphuric  acid),  are  freed  from  copper  and  silver  in 
the  moist  way ;  the  copper  may  be  extracted  by  a  solution  of  iron  chloride  and  the 
copper  precipitated  with  iron  sulphide. 

In  the  Db'tsch  process  (worked  at  Rio  Tinto)  the  pyrites  are  treated  with  ferric 
chloride :  CuS  +  Fe,Cl6  =  2FeCl8  +  CuCl2  +  S  and  Cu2S  +  Fe8Cl6  =  2FeCl2  +  Cu2Cl2  +  S. 
The  practical  utility  of  these  reactions  is  that  the  ferric  chloride  in  solution  preferably 
attacks  the  cuprous  sulphides,  whilst  the  iron  pyrites  remain  almost  unchanged. 
Instead  of  ferric  chloride  there  may  be  used  a  solution  of  ferric  sulphate  and  common 
salt,  which  is  distributed  uniformly  over  the  tops  of  the  heaps.  The  solution  penetrates 
downwards  and  runs  into  a  tank,  where  it  settles,  and  is  next  led  into  the  precipitating 
tank.  Before  making  up  the  heaps,  0-5  per  cent,  of  common  salt  and  an  equal  quantity 
of  ferric  sulphate  are  mixed  with  the  pyrites.  The  height  of  the  heaps  varies  from 
4  to  5  metres.  By  means  of  methodic  lixiviation  1-34  per  cent,  of  copper,  that  is,  the 
half  of  the  2'68  per  cent,  originally  present,  can  be  removed  in  four  months ;  in  two 
years,  2-2  per  cent. ;  whilst  by  the  old  process  of  roasting  in  free  heaps  and  lixiviation 
with  pure  water  only,  ri  per  cent,  can  be  obtained  in  the  same  time.  The  cuprous 
chloride  is  precipitated  with  iron ;  the  lye  is  treated  with  chlorine  and  used  afresh. 
The  chlorine  is  obtained  by  igniting  a  mixture  of  sea-salt  and  iron  sulphate  with  access 
of  air :  2FeS04  +  4NaCl  +  30  =  Fe2O3  +  2Na2S04  +  4C1. 

An  average  sample  of  cement  copper  obtained  by  the  Witkowitz  Mining  and 
Metallurgical  Company,  from  the  lixiviation  of  burnt  ore,  and  also  the  crude  copper 
obtained  by  melting  it  in  crucibles  without  additions,  had,  according  to  L.  Schneider 
{1884),  the  following  composition: — 


Cement  Copper. 


Copper 

Silver 

Gold 

Arsenic 

Bismuth 

Lead 

Iron 


1  1  -30  per  cent. 
0-521 
trace 

Ferrous  chloride 
Cobaltous  chloride 
Nickelous  chloride 

65-3I 
0-19       •  • 

0'45 
1-18 

0'20 

Arsenious  chloride 
Lead  sulphate 
Sodium  sulphate 
Calcium  sulphate 
Magnesium  sulphate 
Water 

0-32 

Crude 
92-752  per  cent. 
0-699 

Copper. 
Cobalt 
Nickel 

O'OOI 

Zinc    .         .         . 

I-452 
0-188 
0760 
3-1" 

Phosphorus 
Sulphur 
Oxygen 

o-i6  per  cent. 

0-29 

0-07 

1-32 

2-19 

3'39 

5-32 

0'59 

2-98 


0-178  per  cent. 

0-051 

traces 

0-055 

0-190 

0-360 


All  cement  copper,  in  consequence  of  the  treatment  with  iron,  contains 
generally  considerable  admixtures  of  basic  ferric  salts,  which  delay  the  refining,  and 
occasion  a  loss  of  copper,  if  chlorine  is  present.  For  the  removal  of  these  salts  there 
is  required  a  mechanical  preparation  by  washing,  so  that  the  proportion  of  copper  is 
raised  to  94-05  or  95-93  There  may  besides  be  present,  iron,  antimony,  arsenic,  lead, 
nickel,  cobalt,  lime,  sulphuric  acid,  and  chlorine  (the  last  from  0-06  to  0-21  percent-.). 
Blister  copper,  obtained  chiefly  from  rich  ores,  contained  in  three  samples  87-02  to 


SECT,  ii.]  COPPER.  159 

94-31  copper,  besides  iron,  antimony,  arsenic,  lead,  nickel,  cobalt,  silver,  and  sulphur 
— the  last  from  ro6  to  2*11  per  cent.  Cement  copper  may  be  combined  with  lime  to 
promote  the  formation  of  slag  and  to  render  the  chlorine  harmless. 

The  fusion  with  a  reducing  flame  (the  lateral  draughts  being  closed),  for  the  purpose 
of  volatilising  antimony  and  arsenic,  lasts  from  nine  to  fourteen  hours,  according  to  the 
quality  ;  the  treatment  is  then  continued  with  open  draughts,  in  order  to  slag  the 
foreign  materials,  producing  either  a  thinly  fusible  slag  (cement  copper  after  treatment 
with  lime),  or  a  basic,  and  merely  fritted  slag,  containing  iron  and  nickel,  along  with 
which  there  appears,  if  the  mass  in  fusion  contains  arsenic,  antimony  or  lead.  A  slag 
consists  of  nickel  and  lead  antimoniates  or  arseniates,  until  a  sufficiency  of  cuprous 
oxide  has  been  formed,  and  this  in  the  period  of  reaction  is  decomposed  with  copper 
sulphide,  accompanied  with  strong  effervescence  (copper-rain)  occasioned  by  the  escape 
of  sulphurous  acid,  as  follows  :  Cu4S  +  2Cu2O  =  6Cu  4-  S02.  When  the  frothing  and 
b  ubbling  of  the  bath  have  ceased,  the  copper  is  more  or  less  pure,  but  still  contains 
antimoniates  and  arseniates  in  such  quantity  that  a  purification  with  soda  is  advisable 
for  their  removal,  until  a  sample  of  the  copper  shows  a  crystalline  fracture  and  a  deep 
red  colour.  The  copper  then  contains  cuprous  oxide,  is  overdone  and  porous,  in 
consequence  of  sulphurous  acid,  which  is  still  retained.  Samples  taken  a  short  time 
before  the  apparent  completion  of  the  period  of  reaction  have  an  earthy,  very  porous 
fracture,  often  of  a  greenish  grey  colour.  After  oxidation  for  some  hours,  and  after  the 
still  existing  impurities  have  become  slagged,  the  fracture  is  densely  earthy  and  red ;  on 
further  oxidation,  corresponding  to  a  proportion  of  0-7  to  i'o  per  cent,  of  oxygen,  it  is 
crystalline  and  deep  red. 

Poling  then  follows  to  expel  the  gas  until  the  samples  taken  have  the  required 
compactness,  shown  by  a  finely  earthy  fracture.  To  render  the  copper  ductile,  the 
oxygen  is  expelled  by  means  of  tough  poling,  the  metallic  bath  being  covered  with 
charcoal,  with  the  draughts  closed,  and  poled  until  the  metal  has  a  pure  green  colour, 
and  samples  taken  have  a  silky  lustre  at  the  fracture,  can  be  forged  at  a  red  heat 
without  cracking,  and  at  common  temperature  admit  of  stretching,  bending,  and 
twisting,  and  have  a  fibrous  fracture.  Lots  containing  bismuth  and  lead  must  not  be 
over-poled,  lest  they  entirely  lose  their  oxygen,  but  only  until  a  sample  is  sufficiently 
tenacious  to  be  used  for  common  sheet-copper.  After  the  metal  has  become  malleable, 
it  is  baled  out,  with  iron  ladles  coated  with  clay,  into  moulds  of  iron  or  copper  coated 
with  clay ;  samples  are  often  taken,  and  the  poling  is  regulated  accordingly.  If  the 
poling  gases  (hydrogen  and  carbon  monoxide)  do  not  meet  with  sufficient  oxygen  for 
combustion  they  may  be  absorbed  by  the  copper,  rendering  it  porous  and  unfit  for 
mechanical  treatment.  To  prevent  this  absorption,  especially  in  the  case  of  copper 
free  from  bismuth  and  lead,  red  phosphorus  wrapped  up  in  thin  sheet-copper  has  been 
used  with  success.  According  to  Stahl,  the  phosphorus  is  best  added  to  each  lot  of 
copper  poured  into  the  mould.  On  examining  the  following  refined  coppers — 

I.  II.  III.  IV. 

Ou  .  .  99-365  ...  99*842  ...  99778  •••  99'662 
As  .  .  0-466  ...  0-052  ...  0-004  •••  0-066 
Sb  .  .  trace  ...  ...  ...  0-028 

Fe    .     .    O-OO4     •••      O'OOI     ...      O'OO2     ...      O'OO2 

Ni  .  .  o-oi6  ...  0-004  •••  O'ooi  ...  trace 

Co  .  0-034  •••  0-008  ...  0-003  ...  trace 

O  .  .  0-050  ...  0-062  ...  0-206  ...  0-042 

S  .  .  c'ooi 

Pb  .  .  0-015  •••  trace  ...  trace  ...  0-043 

Sn  .  .  o'ooS  ...  ...            —  Bismuth  o-io2 

Au  .  .  ...  0-004 

99  "959        —         99  "973         •••         99 '994         •••         99 '945 
Sp  gr.        .         .       8-904         ...  8-4*8        ...  8-908         ...  8-468 


160  CHEMICAL   TECHNOLOGY.  [SECT.  n. 

the  arseniferous  copper  I.  was  tougher  than  II.  and  III. ;  the  latter  not  tougher 
than  at  common  temperature,  but  in  a  red  heat  more  easily  forged  and  rolled  than  II. ; 
IV.  was  both  hot  and  cold  short.  This  behaviour  shows  that  corresponding  quantities 
of  arsenic  prevent  the  absorption  of  the  poling  gases,  and  thus  give  a  denser  copper, 
which  is  tougher  than  the  porous  qualities,  because  the  molecules  remain  more  united,  and 
the  intervening  substances,  in  this  case  arsenic,  in  the  quantities  present  do  not  exert 
an  injurious  effect  upon  the  properties  of  the  copper.  Whilst  II.,  on  account  of  its 
larger  percentage  of  copper  and  oxygen,  might  lead  us  to  expect  a  higher  degree  of 
toughness,  its  lower  sp.  gr.  indicates  porosity,  whence  the  copper  is  in  reality  less 
tough  than  II.  The  high  precentage  of  copper  and  the  considerable  density  of  III. 
render  it  fit  to  be  forged  and  rolled  at  a  red  heat,  but  its  proportion  of  oxygen  is 
enough  to  render  it  cold  short  on  working  at  a  common  temperature.  IV.  is  both  hot 
and  cold  short,  on  account  of  the  presence  of  metallic  bismuth. 

In  general,  the  coppers  treated  during  refining  for  the  partial  removal  of  oxygen 
with  phosphorus,  manganese,  phosphide,  &c.,  prove  tougher  and  firmer  than  such  as 
have  been  poled  tough.  At  the  conclusion  of  the  dense-poling,  the  copper  contains 
about  0-2  per  cent,  of  oxygen,  which  allows  it  to  be  rolled  and  forged  at  a  red  heat, 
but  not  at  common  temperatures.  If  an  attempt  is  made  to  reduce  the  oxygen  to 
0*07  or  0*05  by  continuous  tough  poling,  in  order  to  get  rid  of  the  cold  shortness,  the 
metal  absorbs  pole  gases  to  such  an  extent  that  it  fulfils  the  required  conditions  even 
less  by  its  porosity  than  by  the  former  presence  of  oxygen.  Melted  copper  dissolves 
gases  (sulphur  dioxide,  hydrogen,  and  carbon  monoxide),  which  are  expelled  by  carbon 
dioxide.  At  the  Olper  Works  a  sample  of  copper  purposely  over-poled  was  converted 
into  a  very  dense  and  tough  copper  by  passing  into  it  a  current  of  carbon  dioxide. 
The  absorption  of  gases  involves  the  so-called  rising  or  running  of  the  copper.  Bottcher 
has  found  the  cause  of  his  phenomenon  to  be  the  absorption  of  sulphurous  acid  into 
refined  copper.  As  the  copper  cools,  the  gas  becomes  liberated  again.  It  is  formed  by 
the  action  of  copper  sulphide  upon  cuprous  oxide :  2Cu_O  +  Cu2S  =  3Cu,  •+-  Sor 

Whilst,  according  to  Ledebur,  with  the  decrease  of  copper  sulphide  and  cuprous  oxide 
in  the  metal-bath,  the  transformation  of  these  substances  is  proportionately  retarded, 
Hampe  shows  that,  in  spite  of  the  presence  of  oxygen,  copper  may  contain  copper 
sulphide  and  sulphurous  acid. 

Three  Mansfeld  coppers  had,  e.g.,  the  following  composition  : — 

i.  ii.  in. 

Cu  .  .  98-9048  ...  99-5200  ...  99-6125 

Ag  .  .  0*0287  •••  0-0280  ..  0-0292 

Pb  .  .  0*0208  ...  0-0232  ...  0*0200 

As  .  .  0*0223  ...  0-0228  ...  0-0172 

Sb  .  .  0-0059  ...  0-0031  ...  0-0023 

Ni  .  .  0-2200  ...  0*2142  ...  0*2112 

Fe  .  .  0-0029  ...  0-0039  ...  0-0039 

O  .  .  0-7464  ...  0-1546  ...  0-0752 

S      .     .    0-0036       ...        O'OO2I        ...        0*0024 


99-9627  ...  99  -97 19  99  -9739 

I.  is  overdone  copper,  after  nine  hours'  melting  and  four  hours'  poling ;  II.,  dense 
refined  copper  after  dense-poling  for  one  and  a  half  hour  ;  III.,  refined  copper  after 
tough  poling  for  one  hour. 

If  the  quantity  of  copper  sulphide  is  sufficiently  small  it  cannot  be  detected  during 
dense  poling  in  the  ladle  samples,  because  a  sufficiency  of  oxygen  for  transformation  and 
for  the  formation  of  sulphuric  acid  is  wanting.  It  passes  through  the  stage  of  tough 
poling,  and  finally  comes  to  be  cast,  but  meets  here  with  the  newly  formed  cuprous  oxide, 
and  form's  with  it  sulphurous  acid,  which  occasions  the  rising  of  the  copper.  This 


SECT,  ii.]  COPPER.  161 

behaviour  occurs  if  the  dense  poling  stage  is  begun  at  that  point  which  is  indicated  by 
samples  with  a  dense  earthy  fracture,  since  the  proportion  of  oxide  at  this  stage  is  mostly 
not  sufficient  for  conversion  with  all  the  copper  sulphide,  however  uniformly  the  particles 
are  mixed  by  the  poling,  along  with  the  demands  of  the  reducing  gases.  If,  on  the 
contrary,  the  dense  poling  has  been  begun  at  the  point  characterised  by  a  crystalline 
fracture,  the  proportion  of  oxygen  of  the  cuprous  oxide,  which  is  formed  more  abund- 
antly, suffices  for  complete  conversion  with  the  copper  sulphide ;  and  the  copper  does 
not  rise  on  casting,  if  this  is  not  produced  by  pole-gases  or  by  sulphurous  acid  evolved 
from  pyritic  fuel,  which  were  absorbed  by  the  copper  after  tough  poling.  This  may  be 
ascertained  by  a  sample  before  casting.  That  it  is  not  always  sulphurous  acid  which 
occasions  the  rising  of  the  copper,  but  that  this  phenomenon  may  be  due  to  the  pole- 
gases  (hydrocarbons,  carbon  monoxide,  hydrogen),  is  proved  by  the  fact  that  even  the 
best  coppers,  smelted  with  the  best  fuel,  rise  the  more  the  longer  the  period  of 
toughening  lasts.  Stahl  has  shown  that  there  was  no  trace  of  sulphur  in  some  highly- 
poled  coppers  which  had  risen.  If  the  rising  has  been  occasioned  by  sulphurous  acid, 
sulphur  is,  as  a  rule,  still  demonstrable  in  the  copper.  It  is  very  difficult,  whilst 
ladling  out  the  copper,  to  regulate  the  access  of  air  so  that  all  the  combustible  gases 
are  burnt,  whilst  the  copper  remains  unchanged.  If  the  supply  of  air  is  too  scanty, 
there  is  a  reducing  atmosphere  in  the  furnace,  the  copper  absorbs  carbon  monoxide,  it 
becomes  porous,  and  it  must  be  again  rendered  dense  by  oxidation  or  by  the  method 
stated  below.  If  the  access  of  air  is  too  free,  the  copper  goes  back,  takes  up  oxygen, 
and  must  be  again  poled  until  it  is  tough.  Combustion  gases  are  not  absorbed,  since 
their  ultimate  products,  carbon  dioxide  and  watery  vapour,  are  not  absorbable. 

The  presence  of  oxygen,  lead,  arsenic,  or  phosphorus  has  a  marked  influence  on 
the  density  of  copper.  As  the  proportion  of  oxygen  decreases  on  poling  from  0*210  to 
0*05 1  per  cent.,  the  porosity  of  the  copper  increases  by  taking  up  pole-gases.  With  a 
proportion  of  oxygen  of  0*160  per  cent,  the  absorption  of  gases  is  just  perceptible  ;  but 
lower  down  it  becomes  very  distinct,  and  as  the  oxidation  of  the  copper  increases  its 
density  follows.  An  absorption  of  the  gases  makes  itself  perceived  before  the  propor- 
tion of  oxygen  has  been  reduced  by  tough  poling  as  far  as  necessary  for  producing 
sufficient  toughness,  and  if  the  period  of  tough  poling  is  too  much  prolonged  the  gas- 
absorption  goes  to  such  an  extent  that  the  copper  is  worse  than  when  it  contained  from 
0*200  to  0*160  per  cent,  of  oxygen. 

The  addition  of  lead  is  said  to  prevent  the  rising  of  copper  from  sulphurous  acid, 
becoming  converted  by  the  acid  into  lead  sulphide  and  lead  oxide,  and  also  to 
render  the  copper  fitter  for  forging  and  rolling,  by  purifying  it  from  antimony  and 
arsenic.  According  to  Stahl,  it  condenses  porous  copper  by  dissolving  therein,  becoming 
partly  evaporated,  and  expelling  the  gases,  just  as  do  watery  vapour  and  carbon  dioxide. 
An  excess  of  lead  added  in  refining  makes  the  copper  exfoliate  on  rolling.  Under 
certain  circumstances  arsenic  prevents  the  absorption  of  the  pole-gases  and  keeps  the 
copper  dense.  Such  arsenif erous  copper,  obtained  even  after  prolonged  poling,  has,  along 
with  a  low  proportion  of  oxygen,  the  property  of  being  better  adapted  for  working 
than  less  dense  refined  copper  richer  in  oxygen,  even  up  to  a  proportion  of  arsenic  of 
i  per  cent.  Antimony  acts  similarly  to  arsenic.  In  copper  free  from  lead  and 
bismuth,  phosphorus,  as  a  reducing  agent,  acts  favourably  upon  the  density  of  copper. 
The  porosity  of  copper  occasioned  by  sulphurous  acid  or  pole-gases  is  distinct  from  that 
which  arises  during  casting,  by  air  bubbles  carried  along  mechanically. 

Obtaining  and  Refining  Copper  by  Electricity. — The  installation  erected  by  Mar- 
chese  for  a  company  at  Genoa  consists  of  20  Siemens  machines  for  electrolysis,  each  of 
which,  with  a  tension  of  15  volts  and  a  current  of  250  amperes,  serves  12  baths. 
A  part  of  the  ores  to  be  treated  are  smelted,  according  to  their  nature,  to  a  raw 
matte,  which  serves  in  the  process  as  an  anode  (positive  pole),  and  consists  of  about 

L 


162  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

30  per  cent,  copper,  30  sulphur,  and  40  iron.  Another  portion  of  the  ores  is  roasted  to 
produce  a  liquor  containing  as  much  copper  sulphate  as  is  necessary  to  utilise  the  iron 
sulphate  of  the  anodes  for  the  electrolytic  decomposition  of  the  same  solution  of  copper 
sulphate.  That  part  of  the  mineral  which  is  reserved  for  anodes  is  melted  to  raw 
metal  in  the  ordinary  manner.  The  crude  metal  is  cast  in  thin  plates  corresponding 
to  the  sizes  of  the  troughs,  and  into  each  there  is  inserted  a  slip  of  copper  to 
effect  the  connection  with  the  circuit.  The  kathodes  (negative  poles)  are  formed 
of  thin  sheets  of  copper.  The  roasted  ores  are  systematically  lixiviated  with  the  addi- 
tion of  sulphuric  acid,  in  order  to  dissolve  the  metal  present  as  oxide,  and  the  solution 
obtained,  a  mixture  of  copper  and  iron  sulphate,  is  passed  into  cisterns.  Copper  sul- 
phate is  decomposed  by  the  electric  current,  the  copper  being  deposited  upon  the 
kathodes ;  at  the  same  time  the  metallic  sulphates  forming  the  anodes  are  attacked ; 
there  are  formed  iron  salts  and  sulphuric  acid,  which  prevent  the  precipitation  of  iron 
from  the  copperas  (iron  sulphate)  and  the  development  of  hydrogen.  In  order  to  keep 
the  solution  saturated  and  of  correct  composition,  it  is  passed  through  the  collecting 
pipes  from  the  separate  baths  to  the  cisterns  for  liquor,  and  thus  a  regular  and  constant 
circulation  is  maintained  between  the  baths  and  the  cisterns.  The  tension  required  is 
about  one  volt.  The  worn-out  anodes  are  utilised  for  sulphur  or  sulphuric  acid.  If 
the  solution  contains  too  much  iron  it  is  removed;  the  last  traces  of  copper  are 
precipitated  by  the  sulphuretted  hydrogen  evolved  by  the  action  of  the  liquor  upon 
the  raw  metal.  In  the  same  manner,  the  ferrous  sulphate  is  reduced  and  the  free 
sulphuric  acid  is  neutralised.  The  ferrous  sulphate  is  crystallised  out,  if  it  is  saleable, 
by  a  suitable  arrangement  of  the  baths,  a  proper  composition  of  the  solution,  and  a 
well-managed  circulation ;  the  daily  yield  of  pure  copper  is  said  to  be  20  kilos,  per 
horse-power. 

The  diagram  (Fig.  170)  makes  the  succession  of  the  operations  more  intelligible. 

Siemens  and  Halske  use  as  depolarising  agent  a  liquid  in  connection  with  insoluble 
anodes,  and  separate  the  salt  of  copper  to  be  decomposed  at  the  kathode  from  the 
liquid  to  be  oxidised  at  the  anode  of  a  non-metallic  septum.  The  liquid  submitted  to 
electrolysis  consists  of  a  solution  of  iron  and  copper  sulphates,  with  the  addition  of 
some  free  sulphuric  acid  to  increase  its  conductivity, 

If  single  decomposition  cells  are  used,  this  liquid  is  best  introduced,  without  inter- 
ruption, near  the  bottom  of  the  solution  surrounding  the  kathode  plates  (Fig.  171); 
it  rises  here  whilst  a  part  of  the  copper  is  deposited  by  the  electric  current  at  the 
kathodes,  Ou,  and  flows  over  the  upper  edge  of  the  membrane,  C,  into  the  anode-spaces, 
which  it  traverses  in  order  to  be  drawn  off  again  at  the  bottom,  through  JRa. 

During  this  descent  the  ferrous  sulphate  is  first  decomposed  into  basic  ferric 
sulphate,  and  then,  by  taking  up  the  sulphuric  acid  liberated  in  the  decomposition  of 
the  copper  sulphate,  it  is  converted  into  neutral  ferric  sulphate,  which,  on  account  of 
its  greater  specific  gravity,  sinks  to  the  bottom  at  the  carbon  rods  or  plates.  The 
liquid  flowing  off  has  therefore  become  poorer  in  copper  and  consists  in  part  of  neutral 
ferric  sulphate.  This  solution  has  the  property  of  converting  copper  sub-sulphide, 
copper  mono-sulphide  and  copper  oxide  into  copper  sulphate.  Hence,  by  the  solution 
of  the  two  copper  compounds,  the  ferric  sulphate  is  reconverted  into  ferrous  sulphate, 
whilst  the  oxygen  liberated  oxidises  the  copper  sulphide.  By  previously  roasting  the 
copper  pyrites  at  a  gentle  heat,  a  product  has  been  obtained  in  which  the  copper  exists 
chiefly  as  copper  hemi-sulphide  and  the  iron  as  oxide,  the  latter,  therefore,  in  a  state  in 
which  it  is  not  attacked  by  ferric  sulphate  and  very  slightly  by  sulphuric  acid,  whilst 
the  copper  hemi-sulphide  is  powerfully  dissolved  by  the  solution  of  ferric  sulphate. 

The  process  is  continuous,  the  same  liquid  serving  until  it  is  rendered  unfit  for 
galvano-deposition,  by  having  taken  up  foreign  metals. 


SECT.  II.] 


COPPER. 


163 


The  chemical  processes  involved  appear  from  the  following  equations  :  _ 
i.       xH2SO    +  2CuS0    +  4FeSO4  =  2Cu  +  2JTe2(S04)3  +  xH2S04. 

xH8SO4. 


2.  «.  xH2S04  +  Cu2S  +  2Fe2(S04)3  =  2CuS04  +  4FeS04  + 

b.  CuO  +  H2SO4  =  CuSO4  +  H2O. 

c.  3CuO  +  Fe2(S04)3  =  3CuS04  +  Fe2O3. 

d.  CuO  +  2FeS04  +  H20  =  CuS04  +  (Fe203  +  SO3)  + 

Fig.  170. 


Explanation  of  Terms. 
Kupfererze  Copper  ores. 

Schmelzen  zu  Kupferstein  fiir    Fusion  to  copper  matte 

Anoden 
Riisten 
Anoden 
Gen'istete  Erze 
Kammersaure 
Unverandecte  Riickstande 
Losuny  imd  Auslaugen 


H 


Cmcentriruny 
Kreislauf 
Bdder 
Electrolyte 
Schicefelsiiiirc 
Chemisch.   reines 
Flatten 


Kupfer    in 


Schicefel  haltende  Rilckstande 
Xiederschlag  von  Kupfer,  CuS, 

Fiillung  des  Kupfers  und  Re- 

duction 
Kisenvitriol  oder  Ablauf 

Eisenvitriol 
Krystallisation 
Rolunaterial 
Verkaufliche  Producte 
Nebenproducte 


for  anodes. 

Boasting. 

Anodes. 

Eoasted  ores. 

Chamber  acid. 

Unchanged  residues. 

Solution  and  Lixivia- 
tion. 

Concentration . 

Circulation. 

Baths. 

Electrolyte. 

Sulphuric  acid. 

Chemically  pure  cop- 
per in  plates. 

Solution. 

Sulphurous  residues. 

Precipitate  of  copper, 
CuS. 

Precipitation  of  cop. 
per  and  reduction. 

Copperas  or  waste 
liquor. 

Copperas. 

Crystallisation. 

Raw  material. 

Saleable  products. 

Bye-products. 


On  comparing  the  formulae  i,  and  2  a,  we  perceive  that  if  the  ore  contains  all  its 
copper  in  the  form  of  a  hemi-sulphide  the  electrolyte  contains,  after  the  transflux 
of  the  lixivium,  exactly  the  same  quantity  of  copper  sulphate,  iron  sulphate,  and 
sulphuric  acid  as  before  electrolysis,  and  is  therefore  completely  regenerated  and  can 
be  again  used  for  electrolysis.  If,  on  the  contrary,  the  copper  is  partly  present  in  the 
ore  as  oxide,  it  is  seen  from  equations  2  b,  c,  and  d  that  in  this  case  after  lixiviation  the 
electrolyte  is  richer  in  copper  but  poorer  in  iron  than  it  was  before  electrolysis. 

It  need  scarcely  be  mentioned  that,  instead  of  roasted  copper  pyrites,  unroasted  raw 
matte  in  which  the  copper  is  almost  exclusively  present  as  hemi-sulphide  may  serve 
for  lixiviation.  Here  not  only  copper,  but  iron,  is  dissolved,  so  that  a  complete  uni- 
formity of  the  solution  in  copper  and  iron  is  not  reached. 


164 


CHEMICAL  TECHNOLOGY. 


[SECT.  n. 


Fig.  171. 


In  the  galvanic  process  described,  no  polarisation  occurs,  and  the  different  position 
of  the  anode  and  kathode  in  the  series  of  tension  does  not  occasion  any  counter  electric 
force. 

Whilst,  on  using  anodes  of  raw  metal,  there  is  required  a  potential  difference  of 
about  i '5  volt  in  the  processes  above  described,  there  is  needed  a  tension  of  only  0*7 
volt  for  the  same  density  of  current.  Whilst,  further,  in  using  anodes  of  copper 
matte,  about  one-third  of  the  current  is  used  in  other  reductions  and  is  consequently 
wasted,  there  is  here  no  loss  of  current. 

For  refining  copper  the  distance  of  the  electrodes  is  5  centimetres,  the  density  of 
the  current  is  20  to  30  amperes  per  square  metre  of  kathode  surface,  and  the  bath  is  a 
solution  of  1 50  grammes  copper  sulphate  and  50  grammes  sulphuric  acid  to  i  litre  water. 
The  tension  for  the  bath  is  o-i  to  o-2  volt.  Manganese,  zinc, 
iron,  cadmium,  tin,  antimony,  arsenic,  lead,  and  bismuth  pass 
into  the  liquid,  remaining  in  the  mud  at  the  anodes  only 
if  insoluble  compounds  are  formed.  Silver,  platinum,  and 
gold  are  deposited  on  the  anode  in  the  metallic  state.  It  is 
essential  that  the  bath  must  remain  acid  and  must  be  kept 
constantly  in  motion. 

\  |  If  the  tension  at  the  terminals  of  the  dynamo  is  1 5  volts,  the 

^J)  tension  in  the  bath  0*25  we  might  put  (15  :  0-25)  =  60  baths 

in  series.  For  the  sake  of  safety,  40  are  used.  If  the  dynamo 
yields  240  amperes  hourly,  corresponding  to  283*6  grammes 
copper,  we  obtain  in  twenty -four  hours  in  40  baths,  arranged 
in  series,  272  kilos.  The  work  required  is  (240  x  1 5)  :  736  =  4-9 
horse-power  in  the  dynamo  or  6  horse-power  in  the  engine. 
If  the  tension  in  the  bath,  using  plates  of  very  impure  copper 
matte,  and  impure  solutions,  is  1*2  volt,  so  that  only  10  baths 
can  be  arranged  in  series,  we  obtain  only  one-fourth  of  the 
quantity  of  copper  from  the  same  machine-power. 


Explanation  of  Terms. 

FUissigkeitshuhe — Level  of 
liquid. 

At  Oker  there  are  now  6  dynamos  in  action,  5  of  the  type  Ct  and  one  C,8,  each 
of  which  daily  deposits  250  to  300  kilos,  of  copper,  with  the  expenditure  of  7  to  8  horse- 
power. The  yearly  output  is  therefore  500  to  600  tons  of  copper.  The  copper  to 
be  refined  has  already  undergone  a  furnace  refining,  and  contains  only  g  to  ^  per  cent, 
of  impurity.  Nevertheless,  the  electrolytic  process  is  financially  remunerative,  as  the 
removal  of  the  last  impurities  considerably  raises  the  value  of  the  product. 

The  great  advantage  of  the  electrolytic  process  as  compared  with  furnace-refining 
is,  that  the  precious  metals,  especially  silver,  do  not  pass  into  solution,  but,  as  the 
anode  is  gradually  destroyed,  they  fall  down  into  the  mud.  To  obtain  all  the  silver 
present  in  the  crude  material,  it  is  merely  necessary  to  remove  from  time  to  time  the 
mud  which  collects,  and  to  extract  the  silver.  The  greatest  difficulty  of  the  electrolytic 
process  lies  in  the  behaviour  of  arsenic  and  antimony.  They  pass  into  solution,  and 
as  soon  as  they  exceed  a  certain  proportion  they  begin  to  combine  with  the  deposit  of 
copper,  and  render  it  hard  and  brittle.  In  order  to  meet  this  difficulty  there  is  no 
expedient  except  to  purify  the  solution  or  to  prepare  a  fresh  solution  in  its  stead. 
Both  the  crude  copper  and  the  refined  copper  are  used  in  plates  i  metre  in  length  and 
0-5  metre  in  breadth.  The  plates  of  crude  copper.^  about  15  millimetres  in  thickness, 
are  fixed  in  boxes  at  the  mutual  distance  of  10  to  15  centimetres,  and  plates  of  copper 
are  inserted  between  them  as  kathodes. 

Each  dynamo  Ct  with  a  tension  at  the  terminals  of  3-5  volts,  and  a  current  of  1000 
amperes  in  strength,  works,  as  a  rule,  1 2  baths  introduced  in  series,  the  whole  occupying 
a  space  of  80  square  metres.  The  dynamo  C18  gives  a  tension  of  30  volts  and  a  current 


SECT,  ii.]  COPPER.  !65 

of  1 20  amperes  (or  in  other  cases  15  volts  and  240  amperes).  It  actuates  at  Oker  80 
smaller  baths.  The  room  occupied,  the  quantity  of  liquor,  the  working-power,  and  the 
deposit  of  copper  are  in  this  case  quite  similar  to  the  arrangements  with  CL  dynamos. 
The  expense,  however,  differs,  and  a  decided  advantage  of  the  installation  018  is  that  the 
baths  can  be  placed  at  a  considerable  distance  from  the  machine,  which  is  not  the 
case  with  Or 

Hilarion  Roux,  of  Marseilles,  has  a  5  horse-power  Gramme  and  40  baths,  with  a 
surface  of  anodes  —  900  square  metres.  The  kathodes  are  only  o-5  millimetre  in 
thickness,  and  are  fixed  at  the  distance  of  5  centimetres  from  the  anodes.  The 
machine  consumes  daily  240  kilos,  of  coal  and  yields  at  8  volts  and  300  amperes  250 
kilos,  of  purified  copper  or  10*4  kilos,  hourly.  The  machine  utilises  85  per  cent,  of 
the  power  supplied  =  3 19  kilogrammetres ;  240  of  which,  according  to  Gramme,  are 
spent  in  overcoming  resistance,  and  79  in  transporting  the  metal  between  the  poles ; 
chemical  work  has  not  here  to  be  performed. 

In  order  to  calculate  the  necessary  expenditure  of  work,  the  potential  difference 
between  both  electrodes  must  be  measured  in  a  laboratory  experiment,  with  that 
density  of  current  which  has  been  found  most  favourable  for  general  working,  and  with 
the  intended  distances  of  the  electrodes.  If,  e.g.,  the  tension  at  the  terminals  of  the 
machine  is  15  volts,  and  the  tension  at  the  bath  0*25  volt,  we  might,  if  we  quite  over- 
look the  resistance  of  conduction  outside  the  baths,  at  most  introduce  (15  :  0*25)  =  60 
baths  in  a  series,  but  40  are  generally  found  sufficient.  If  the  machine  at  the  above 
tension  gives  a  current  of  the  strength  of  240  amperes,  representing  238-61  grammes 
copper  hourly,  we  obtain  in  40  baths  arranged  in  series  11*344  kilos,  hourly,  or  in 
twenty-four  hours  272-26  kilos,  of  copper.  The  work  consumed  is  (240  x  15)  :  736  =  4-9 
horse-power  for  a  dynamo,  or  6  horse- power  for  the  steam-engine.  Such  an  installation 
takes  up  a  surface  of  80  square  metres,  and  five  months  are  required  for  producing  a 
copper  plate  of  i  centimetre  in  thickness,  with  a  current  of  20  amperes. 

Properties  of  Copper. — Copper  is  red,  strongly  lustrous,  and,  though  consider- 
ably hard,  it  is  so  ductile  that  it  may  be  drawn  out  to  very  fine  wires  and  rolled  into 
thin  leaf.  It  has  a  granular  fracture,  a  spec.  gr.  (pure)  of  8*955  to  8*956  ;  the  best 
commercial  samples  have  only  8*2  to  8*5  ;  it  fuses  rather  less  readily  than  silver. 
Pure  copper  flows  in  a  thin  stream,  which  quickly  solidifies ;  if  contaminated  with  cuprous 
oxide,  it  flows  more  sluggishly  and  solidifies  less  rapidly.  Melted  copper  has  a  peculiar 
sea-green  colour.  For  castings  copper  is  not  good,  since  it  gives  porous  articles 
full  of  air-bubbles,  probably  because  cast  too  hot.  At  high  temperatures,  and  with 
access  of  air,  copper  burns  with  a  fine  green  flame.  If  exposed  to  moist  air,  it 
gradually  becomes  coated  with  copper  hydrocarbonate,  commonly  but  improperly 
called  verdigris.  If  heated  with  access  of  air,  it  takes  at  first  rainbow  colours,  and 
then  becomes  covered  with  a  reddish-brown  film  of  cuprous  oxide,  which  by  degrees 
turns  black,  and  on  quenching  the  ignited  metal  in  hot  water,  or  on  hammering  or 
bending,  falls  off  in  scales. 

Copper  is  used  for  boiling-vessels  and  coolers  in  distilleries,  breweries,  and  sugar- 
works,  for  sheathing  ships,  for  money,  for  rollers  in  tissue-printing,  for  making  copper 
sulphate,  nitrate,  and  copper  colours,  for  engraving,  and  especially  in  the  production 
of  alloys.  The  Mining  Journal  estimates  the  quantity  used  yearly  in  cartridges  at 
7500  tons. 

Among  samples  of  refined  copper  examined  in  1884  by  Pupahl,  two  brands  were 
found  unsuitable  for  brass  castings,  on  account  of  their  high  percentage  of  arsenic : — 


i66 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Cu 
O 
Pb 
Fe 

Ni 

Ag 

Au 

8 

As 

Sb 


Wallaroo. 

99795 
0-127 
0-004 

O'OOI 

0-039 
0-015 


Chm.  Co. 

Mansfelder  R. 

99-864 

99'49i 

O'I20 

0-145 

— 

0-038 

trace 

O'OOI 

0-002 

...              O'2OI 

0-028 

0-031 

trace 

... 

99-981 


trace 


100*014 


0-072 
trace 

99-979 


Bede. 
99-148 
0-090 
0-023 
O'OOI 

o'oSi 
0-058 
trace 
0-005 
0-600 

O'OO2 

100-008 


Grange. 

98-961 
0-160 
0-005 
0-004 
0*066 

O'OIO 

trace 
0-766 

O'OII 

99-983 


Copper  obtained   from   Colorado  ores   contains,  according  to   Eggleston  (1883), 
tellurium,  which  renders  it  brittle. 


Cu 

Au        . 

Ag        . 

Pb 

Zn&Ni 

Fe 

S 

Te 

As 

Slag     . 


Stone. 

55-02 
0-06 
0-40 

17-87 

2'22 

4'l8 

2OX>2 

O'I2 


Black  Copper. 


97-120 

0-132 
0-777 
0-070 
0-130 
0-236 
0-093 
0-006 
1-270 


98-090 

0-128 
0757 

O'lOO 

0-080 

0-097 
0-192 


Eefined  Copper. 
99705 

0-135 

0-024 
0-031 
trace 
0-083 
0-091 


Refined  Mansfeld  copper  (1880)  contains  : — 


Cu 
Ag 
Pb 
Fe 

Ni 
As 


A. 

99-394  to  99-550 
0-028  „  0-030 
0-043  »  0-103 
0-025  „  0-132 
0-239  „  0-275 


B. 

99-110  to  99-270 

0-016  „  0-020 

0-134  „  0-259 

0-019  I.  0-024 

0-314  „  0-405 

o-ioi   „  0-144 


The  total  production  of  copper  in  1879  amounted  to  149,000  tons,  and  in  1884  to 
about  208,000  tons,  of  which  the  United  States  furnished  63,950,  Chili  41,648,  Spain 
and  Portugal  43,664  (chiefly  from  Eio  Tinto),  Australia  13,300,  South  Africa  5000, 
and  England  only  2500. 

Copper  Alloys. — Among  the  copper  alloys,  the  most  important  are  bronze,  brass, 
and  nickel-silver,  commonly  called  German  silver.  Bronze  is  an  alloy  of  copper  and 
tin,  or  copper,  tin,  and  zinc  ;  or,  latterly,  of  copper  and  aluminium.  By  these  addi- 
tions copper  is  rendered  more  fusible,  and  hence  easier  to  cast;  denser,  and  thus 
more  susceptible  of  polish,  it  is  also  harder,  more  brittle,  sonorous,  and  resonant,  and 
is  (with  the  exception  of  the  aluminium  alloys)  cheaper,  and  thus  more  suitable  for  a 
variety  of  purposes.  Lead  renders  bronze  more  fusible  and  denser,  but  has  a  great 
disposition  to  separate  out  on  the  surface  in  combination  with  copper.  Hence  a  per- 
centage exceeding  3  per  cent,  is  to  be  avoided.  On  slow  cooling  bronze  becomes 
soft  and  malleable,  but  on  rapid  cooling  hard  and  brittle.  A  small  addition  of 
phosphorus  (0-12  to  0-7 6 ''per  cent.)  makes  some  of  these  alloys  more  homogeneous 
and  pliable.  The  chief  kinds  of  bronze  are  bell-metal,  gun-metal,  art-bronze, 
phosphor-bronze,  and  aluminium-bronze,  the  last  of  which  will  be  described  under 
ALUMINIUM. 

Bell-Metal,  of  spec.  gr.  8-368,  consists  of  78  parts  copper  and  22  parts  tin.  It 
must  combine  sonorousness  with  hardness  and  tenacity.  It  is  a  brittle  metal,  and  its 
treatment  in  the  turning-lathe  is  therefore  difficult.  A  bell  must  obtain  its  intended 
sound  in  the  casting,  by  its  form  and  by  its  composition.  It  is  an  error  to  suppose 


SECT,  ii.]  COPPER.  167 

that  silver  has  to  be  mixed  with  bell-metal  to  yield  a  good  sound.  The  alloy  for 
certain  instruments  of  military  music,  such  as  cymbals,  as  well  as  of  tom-toms  and 
gongs,  is  similar  to  bell-metal. 

Gun-Metal  consists,  on  an  average,  of  90  parts  copper  and  9  tin.  It  has  the 
defect  of  becoming  gradually  decomposed,  either  by  a  kind  of  eliquation,  more  fusible 
alloys  richer  in  tin  separating  out  from  less  fusible  parts  richer  in  copper,  or  by 
combustion,  since  tin  burns  more  readily  than  copper,  the  alloy  thus  becoming  poorer 
in  tin. 

Art-Bronze,  for  statues,  busts,  decorations,  &c.,  consists  of  copper  and  tin.  It 
must  be  so  composed  that  when  melted  it  fills  up  the  mould  completely,  giving  a  clear, 
sharp  casting,  which  admits  of  being  easily  retouched,  and  takes  a  fine  patina.  A 
normal  bronze,  according  to  Elster,  consists  of  86-6  copper,  6-6  tin,  3-3  lead,  and 
3'3  zinc- 

Bronze  is  valued  for  its  property  of  quickly  becoming  coated  with  a  uniform  fine 
green  layer  of  oxide  (patina),  the  formation  of  which  is  often  expedited  by  chemical 
means.  According  to  Weber,  zinc  hinders  the  formation  of  patina;  he  recommends 
that  copper,  as  free  as  possible  from  arsenic,  should  be  used  with  tin  alone.  A  bronze 
statue  having  a  remarkably  fine  patina  consisted  of  88'6  per  cent,  copper,  9-1  per  cent, 
tin,  i -3  zinc,  and  0*8  lead.* 

Phosphor-Bronze  (90  parts  copper,  9  tin,  and  0-5  to  075  phosphorus)  was  in- 
vented in  1871  by  C.  Kiinzel.  It  has  been  latterly  used  for  gun-metal,  bell-metal, 
art-bronze,  for  the  bearings  of  axles,  &c.  The  elasticity  is  considerably  heightened  and 
its  absolute  tenacity  is  increased  more  than  twofold  by  the  introduction  of  phosphorus, 
and  the  hardness  is  augmented  to  such  a  degree  that  some  specimens  resist  the  file. 
The  metal  when  melted  flows  well  and  fills  the  mould  perfectly. 

Brass. — Zinc  and  copper  combine  with  each  other  in  all  proportions,  some  of  which 
are  well  known  as  brass,  and  find  numerous  applications.  The  following  are  instances : — 

Cu.  Zn.  Pb.                            Sn. 

Clock  wheels            .    60-66  ...  36.88        ...                         ...          1-35 

Cast  brass         .         .     6370  ...  33'5o        ...          0-30        ...          3-50 

Sheet  brass       .        .     70*10  ...  29-90 

Brass  wire        .         .     71-89  ...  27-63         ...           0-85 

In  general,  a  reduction  of  the  proportion  of  zinc  gives  the  brass  a  darker  and  a  redder 
colour ;  a  larger  proportion  of  zinc  gives  a  paler  and  yellower  metal.  The  larger  the 
proportion  of  copper  the  more  extensile  is  the  brass.  When  cold,  brass  is  malleable 
and  can  be  rolled  and  drawn  to  wire.  When  hot,  it  easily  breaks  and  cracks.  A 
malleable  brass  (yellow  metal)  which  can  be  forged  and  rolled  is  obtained  by  melting 
together  60  parts  of  copper  with  40  of  zinc. 

Brass  is  superior  to  pure  copper  in  several  respects.  It  has  a  more  pleasing  colour, 
does  not  oxidise  so  readily,  is  harder  and  stifier  (whence  its  use  for  pins) ;  has  a  lower 
melting-point,  and  when  melted  flows  more  easily  and  does  not  become  blistery ;  hence, 
and  from  its  lower  cost,  it  is  preferred  for  castings.  The  addition  of  i  or  2  per  cent, 
of  lead  makes  the  brass  more  suitable  for  turning ;  it  also  files  better,  and  does  not 
clog  the  file. 

Brass  was  formerly  manufactured  by  fusing  together  calamine  with  black  copper 
and  charcoal.  Now  it  is  produced  by  melting  metallic  zinc  with  refined  copper. 

Alloys  similar  to  brass  are  pinchbeck  (tombak),  containing  85  parts  copper  with 
15  zinc.  Spurious  gold-leaf  is  made  in  Germany  from  2  parts  zinc  and  n  copper. 

Other  alloys  are  prince's  metal,  similor,  ore'ide,  Mannheim  gold,  &c.  Delta  metal 
is  composed  of  60  parts  copper,  32-2  zinc,  and  1*8  iron.  Sterro-metal  is  similar  in 

*  The  formation  of  patina  is  now  found  to  be  due  to  the  action  of  certain  minute  organisms. — 
[EDITOB.] 


168  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

composition,  but  much  harder.  Muntz's  metal,  used  for  sheathing  ships,  for  bolts, 
ships'  nails,  &c.,  consists  of  copper  and  zinc  in  proportions  fluctuating  between  50  per 
cent,  zinc  to  63  copper  and  37  zinc  to  50  copper.  The  alloy  for  the  bronze  coinage 
of  France,  Sweden,  Britain,  Spain,  Russia,  Norway,  Greece,  Servia,  and  Boumania 
consists  of  95  parts  copper,  3-5  tin,  and  1-5  zinc.  In  Denmark  the  alloy  is  90  copper, 
5  tin,  and  5  zinc.  The  German  bronze  coins  (2  and  i  pfennig  pieces)  consist  of  95 
copper,  4  tin,  and  i  zinc.  So-called  white  brass  consists,  like  bath  metal,  of  55  copper 
and  45  zinc.  Button  metal  is  composed  of  20  copper  and  80  zinc. 

The  Bronze  colours  used  for  bronzing  objects  of  plaster  or  wood,  as  also  for  cast- 
metal  articles,  in  letter-press  and  lithographic  printing,  in  lacquering,  and  in  the  manu- 
facture of  paper-hangings,  &c.,  are  made  from  the  powders  resulting  from  forging  metals, 
which  are  ground  up  and  heated  with  oil,  tallow,  wax,  or  parafnne  ;  the  colours  which 
they  assume — violet,  red,  orange,  gold-colour,  and  green — are  due  to  superficial 
oxidation.* 

German  silver  (Argentan,  Pakfong,  Mail  lech  ort)  is  an  alloy  of  copper,  nickel,  zinc, 
or  tin,  which  may  be  regarded  as  brass,  with  an  addition  of  \  to  |  of  nickel.  It  has 
a  yellowish  white  colour,  a  densely  granular  or  jagged  fracture,  a  spec.  gr.  of  8*4  to 
8- 7,  and  it  is  harder  than  common  brass,  but  almost  equally  extensile.  It  takes  a 
very  high  polish.  In  its  preparation  there  are  used  zinc,  copper,  and  nickel  in  a 
comminuted  state.  The  metals  are  put  in  a  crucible,  a  part  of  the  copper  being 
laid  at  the  top  and  the  rest  at  the  bottom.  The  whole  is  then  covered  with  charcoal 
powder  and  melted. 

German  silver  takes  a  fine  polish,  and  remains  for  a  long  time  unchanged  on  expo- 
sure to  the  air  ;  it  is  less  readily  attacked  by  acid  liquids  than  are  copper  and  brass. 
The  proportions  of  the  ingredients  are — copper  50  to  66  per  cent.,  zinc  19  to  31,  nickel 
13  to  18*5.  Latterly,  smaller  proportions  of  nickel  are  found  in  cheap  sorts  of  German 
silver. 

•  German  silver  can  scarcely  be  distinguished  on  the  touch-stone  from  a  silver- 
alloy  of  0-750.  If  the  streak  is  moistened  with  nitric  acid,  it  disappears  more 
rapidly  than  that  of  silver,  and  on  the  addition  of  a  solution  of  sodium  chloride,  no 
turbidity  is  produced.  It  is  chiefly  used  in  rolled  sheets.  Alfenide,  used  for  candle- 
sticks, milk-cans,  tea  services,  forks,  spoons,  &c.,  is  German  silver  electro-plated, 
containing  about  2  per  cent,  of  silver.  Other  plated  nickel  alloys  are  Peru  silver, 
China,  silver,  Christofle,  and  Alpacca.  Tiers  Argent  consists  of  27-5  silver,  62^5  copper, 
nickel,  and  zinc. 

An  alloy  of  nickel  and  silver  has  been  used  in  Switzerland  since  1850  for  small 
coinage.  It  contains  pieces  for — 

Silver.  Copper.  Zinc.  Nickel. 

20  raps      ...         15  ...         50  ...  25  ...         10 

1°    ii         •                 .        10  ...        55  ...  25  ...        10 

5    i.                                   5  ...        60  ...  25  ...        10 

A  metal  formerly  met  with  under  the  name  Suhler-white  copper,  contained  88 
parts  copper,  875  nickel,  1-75  antimony.  It  was  obtained  from  old  slag-heaps,  and  is 
the  first  nickel  alloy  which  was  used  in  the  arts. 

Copper  Amalgam. — A  compound  of  30  parts  copper  and  20  mercury,  obtained 
by  moistening  copper-powder  with  mercurous  nitrate,  covering  with  hot  water,  and 
adding  the  required  amount  of  mercury  by  grinding.  It  is  also  known  as  metallic 
putty,  and  is  a  soft  mass,  which  softens  in  a  few  hours.  It  is  also  (most  injudi- 
ciously) used  for  stopping  hollow  teeth. 

*  Bessemer  has  effected  great  improvements  in  the  preparation  of  bronze  colours.— [EDITOR.] 


SECT.    II.] 


LEAD. 


i6g 


Fig.  172. 


Fig.  173- 


LEAD. 

Lead  has  been  known  from  the  remotest  antiquity.  It  rarely  occurs  native,  but  fre- 
quently combined  with  sulphur,  as  galena  (PbS),  and  as  Bournonite,  a  lead  and  anti- 
mony sulphide.  The  latter  ore  consists  of  lead  41*77  parts,  copper  1 2*76,  antimony  26-oi, 
and  sulphur  19-46.  It  is  worked  for  lead  and  copper.  Lead  is  found  also  as  cerus- 
site,  white  lead  ore  (PbCO3),  pyromorphite,  or  green  lead  ore  (3Pb3(PO4)2  +  PbCl,), 
mimetesite,  a  lead  arseriiate  (3Pb3(As04)2  +  PbCl2),  as  Anglesito  (lead  sulphate,  PbSO4), 
yellow  lead  ore  (lead  molybdate,  PbMo04),  and  as  crocoisite,  or  red  lead  ore  (a  lead 
chromate,  PbCr04). 

Production. — Lead  is  obtained  almost  exclusively  from  galena.  Its  extraction 
depends  on  the  behaviour  of  galena  with  metallic  iron.  If  lead  sulphide  is  heated  with 
metallic  iron,  there  are  formed  iron  sulphide  and  metallic  lead  :  PbS  +  Fe  =  FeS  +  Pb. 
The  galena,  previously  freed  from  gangue  by  smelting  or  elutriation,  is  mixed  with 
granular  iron  and  smelted  down  in  a  shaft-furnace.  The  products  are  metallic  lead 
and  a  lead  matte.  Instead  of  metallic  iron,  there  may  be  used  iron  ores  and  slags, 
which  exert  a  desulphurising  action  by  means  of  their  oxygen. 

Figs.  172,  173,  and  174  show  a  lead  smelting  furnace  (sump-furnace).  The  hearth 
and  the  sump  lie  partly  outside  the  furnace.  The  gases  escaping  from  the  shaft  B, 
before  reaching  the  chimney  T,  pass  through  chambers  in  which  they  deposit  the 
particles  of  ore  carried  away  by  the  blast  o. 
The  assorted  ores  mixed  with  granular  iron 
are  thrown  into  the  furnace  in  alternate 
layers.  The  liquid  products  collect  in  the 
sump  C.  The  products  are  slag  floating 
on  the  surface,  argentiferous  lead  and  lead 
matte.  The  latter  is  either  roasted  and 
worked  up  for  vitriol  or  cement  copper  or 
smelted  with  rich  lead  slags  and  granular 
iron,  and  worked  for  lead.  The  slag  as  it 
forms  is  allowed  to  flow  off  down  an  in- 
clined plane  until  the  sump  is  filled  with 
the  other  products.  The  tap-hole  is  then 
opened,  and  the  product  run  off  into  the 
lower  hearth.  In  this  hearth  the  matter 
as  it  congeals  is  taken  off  in  discs  ;  the 
subjacent  work-lead  is  desilverised  by  the 
Pattinson  process. 

The  production  of  lead  from  galena  by  roasting  in  the  reverberatory  depends  on 
the  behaviour  of  lead  oxide  and  lead  sulphate  with  galena.  By  the  action  of  the 
oxygen  of  the  air,  a  part  of  the  galena  is  oxidised  to  lead  oxide  and  sulphurous  acid, 
whilst  lead  sulphate  is  also  formed.  By  means  of  the  oxygen  of  the  lead  sulphate  and 
the  lead  oxide  the  sulphur  of  the  undecomposed  part  of  the  galena  is  oxidised  and 
removed  :— 2PbO  +  PbS  =  3Pb  +  S02  ;  PbS04  +  PbS  -  2Pb  +  2S02. 

If  an  excess  of  galena  is  present  in  the  roasting  process,  there  is  formed  lead 
sub-sulphide  (Pb2S),  from  which  metallic  lead  is  eliquated,  whilst  the  residue  takes  up 
more  sulphur  :  Pb2S  =  PbS  +  Pb. 

Upon  this  process,  combined  with  the  use  of  a  reverberatory  with  a  depressed 
hearth,  is  founded  the  English  process  for  the  production  of  lead.  The  ordinary 
arrangement  of  the  reverberatories  for  melting  lead  ores  in  Derbyshire  and  Cumber- 
land is  shown  in  Fig.  175.  The  hearth,  formed  of  slags  fluxed  together,  rests  on  a 


170 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Fig.  175- 


Fig.  176. 


massive  wall.  Its  surface  is  inclined  from  all  sides  towards  the  tap-hole,  from  which 
the  lead  flows  down  into  the  anterior  crucible.  The  furnace  has  six  doors  o,  three  of 
which  are  at  the  tapping  side,  and  three  at  the  back.  The  ores  are  let  down  through  a 
funnel  T,  capable  of  being  closed  down  upon  the  hearth.  In  general  800  kilos,  of 
ore  are  introduced  and  worked  up  in  six  to  seven  hours.  The  consumption  of  coal  is 

about  half  the  weight  of  the  ore.  The  ore 
is  spread  level  over  the  hearth,  and  the  doors 
of  the  furnace  are  closed,  that  it  may  be 
heated  uniformly.  In  two  hours  they  are 
opened,  until  the  smoke  filling  the  furnace 
has  disappeared,  when  they  are  closed  .and 
a  strong  heat  is  given.  Subsequently  the 
doors  are  opened  for  the  second  time  and 
the  ore  is  alternately  stirred  through  one  or 
other  of  the  side  doors.  The  mass  becomes 
pasty,  and  the  lead  runs  off  on  all  sides.  The 
stirring  is  kept  up  for  an  hour,  and  then 
the  mass  becomes  almost  liquid.  This  liquefaction  is  promoted  by  additions  of  fluor- 
spar. As  soon  as  it  is  sufficiently  fluid,  the  upper  layer  of  the  slag  is  run  off 
and  caused  to  solidify  by  wetting  with  water.  It  is  called 
white  slag ;  it  has  an  appearance  like  enamel,  and  it  often  con- 
tains 22  per  cent,  lead  sulphate.  Coal  is  introduced  through 
the  middle  door  to  congeal  the  refractory  and  abundant  slag, 
which  has  remained  upon  the  metal.  Lastly  the  tap-hole  is 
opened,  and  the  lead  runs  off  into  the  tap-crucible. 

At  Alternau  the  lead  ore  washings  of  the  Upper  Harz, 
containing  54-55  per  cent,  lead,  o-o8  silver,  0^9  copper,  7-8 
zinc,  and  14-18  silica,  are  roasted  in  a  reverberatory  with  one 
hearth.  For  smelting  there  are  used  two  shaft -furnaces  (Figs. 
176,  177),  the  shaft  of  which,  A,  rises  from  the  form  4  metres  in  a  width  of  1*2  metre, 
and  then  ends  in  a  wrought-iron  top-piece  i  metre  in  height,  which  expands  above  to 

1 1  metre.  Up  to  i  metre  above  the  form  the  shaft  has  a 
gentle  slope  to  form  and  rest,  with  which  the  front  wall  of 
d,  the  furnace,  runs  parallel.  A  wrought-iron  water  re- 
frigerator, e,  which  forms  a  jacket  for  the  back  wall  of  the 
furnace,  protects  it  against  any  corrosive  action  of  the 
charge,  without  having  too  strong  a  cooling  action  upon 
the  melting  mass. 

At  present  4  tons  of  roasted  ore  are  sorted  with  i  ton  of 
raw  slick,  and  these  5  tons  are  charged,  according  to  the  pro- 
portion of  silica  and  zinc,  with  i  to  1*25  ton  of  puddling- 
slag,  i  to  1-25  ton  of  extraction  residues  from  Oker,  and 
0-75  to  1-5  ton  lime,  in  all  3^25  to  3-5  of  basic  materials. 
To  this  come  slags  from  the  same  works  as  they  may  be 
needed.  From  such  a  charge  there  are  obtained  32  to  34 
tappings  each,  with  50  kilos,  of  coke,  and  60  such  lots  are 
worked  through  in  twenty-four  hours,  the  pressure  of  the 
blast  being  14  to  20  millimetres  of  mercury.  The  slag 
drawn  off  in  the  first  quarter  of  1882  contained — 


Fig.  177. 


SECT,  ii.]  LEAD.  171 


Silica    ....  30*32 

Barium  sulphate  .        .  0*19 

Lead     ....  ri3 

Copper          .        .        .  0*18 

Silver    ....  0-0007 

Antimony     .        .        .  0-09 

Ferrous  oxide       .        .  35*72 

Alumina        .         .        .  3-20 


Zinc  oxide     .        .  .  7-27 

Manganous  oxide  .  i'66 

Cobalt  and  Nickel  .  traces 

Lime     .        .       _.  .16-15 

Potassa         .         .  .  0-67 

Soda     .        .        .  o'6i 

Sulphur         .        .  i -47 

Phosphoric  acid    .  .  2-04 


If  the  proportion  of  metal  in  the  slag  is  higher,  it  is  a  sign  that  more  bases  are 
needed  for  the  decomposition  of  the  lead  silicate.  If  separation  takes  place  in  the 
sump  of  the  furnace,  and  the  slag  falls  below  the  normal  amount,  this  indicates  an 
excess  of  basic  additions.  The  influence  of  the  zinc  present,  which  interferes  with  the 
course  of  the  smelting,  must  be  counteracted  by  decreasing  the  lime  and  increasing  the 
iron  in  the  charge,  and  by  the  addition  of  slags  from  the  same  work. 

At  Mechernich  the  ores  are  roasted  in  eighteen  furnaces  with  double  sides,  with 
working-doors  on  both  sides,  and  with  rails  laid  on  both  the  longer  sides  of  the  furnaces, 
for  the  sake  of  possible  working  on  the  sole  of  the  upper  hearth.  Each  furnace  is 
15  metres  long  by  4  in  breadth,  and  the  whole  length  available  for  roasting  is 
24  metres,  with  a  width  of  3*1  metres.  There  is  room  to  receive  50,000  to  55,000  kilos, 
of  ore,  and  the  production  of  roasted  ore  is  8000  to  10,000  kilos,  in  twenty-four  hours, 
so  that  a  lot  of  ore  remains  from  five  to  six  days  in  the  furnace,  which  is  always 
kept  full.  The  ore  is  kept  constantly  stirred  up  as  it  approaches  the  bridge.  The 
imperfectly  liquefied  mass  is  let  off  every  six  hours  in  a  form  made  of  rails  laid  together 
in  front  of  the  furnace,  and  broken  up  when  cold.  There  are  used  15  per  cent,  of 
fuel  for  the  vitreous  product,  which  resembles  obsidian,  and  has  the  following 
composition  : — 

Lead       .        .     58*85  corresponding  to  PbS  .        .      3-47 

PbO          .        .    60-57 
Copper    .        .      0-38  Cu2S          .        .      0-48 


Antimony  .  0*22 

Iron         .  .  2-70 

Zinc         .  .  0-82 

Nickel     .  .  0-75 

Manganese  .  0-36 

Alumina  .  4*80 


Sb2Ss  .  .  0*30 

Fe20s  .  .  3-90 

Zno  .'  .  1-05 

NiO  v  .  0-92 

Mn20g  .  .  0-51 

A1208  .  .  4-80 


Lime        .        .       0-31  „  CaO  .        .      0-31 

Silica       .        .     23-65  „  SiO2          .        .     23-65 

Sulphur  .        .      o'66 

The  fumes  given  off  in  roasting  traverse  a  system  of  chambers  of  10,015 
metres,  and  then  a  chimney  66  metres  in  height.  The  ore  is  melted  in  nine  shaft- 
furnaces  of  7  metres  in  height  and  4-8  metres  in  length.  The  height  of  the  furnace- 
shaft  from  the  forms,  which  are  placed  in  four  bronze  water-troughs,  along  the  back 
wall  to  the  mouth  of  the  funnel  of  the  working-door  is  3*8  metres ;  the  depth  of  the 
level  of  the  forms  i'2  metre,  with  an  enlargement  to  1*5  metre  at  the  top;  the  height 
of  the  crucible,  moulded  of  sweepings,  is  i  metre.  For  letting  off  the  lead  are  two 
lateral  tapping-channels  opening  into  the  crucible,  13  to  15  centimetres  above  its 
bottom ;  the  tapping-hole  for  slags  is  40  centimetres  below  the  diameter  of  the  forms. 
Iron  pots  suspended  in  trucks  serve  to  receive  the  slag  in  such  a  manner  that  it  flows 
over  from  a  larger  pot  (interposed  to  keep  back  lumps  of  lead  matte)  into  a  smaller 
one.  The  charges  for  the  furnace  are  placed  in  tilting-trucks,  which  (with  the 
exception  of  the  limestone)  are  raised  by  tackle  to  the  level  of  the  furnace-mouth. 
The  charge  consists  of  100  parts  of  roasted  ore,  5  parts  of  furnace  bottoms,  35  iron- 
finery  slags,  15  raw  sparry  iron,  45  limestone,  10  lead  slags,  and  25  coke.  Of  the  nine 
shaft-ovens  only  four  are  in  regular  work,  which  get  through  282,400  kilos,  of  charge 
in  twenty-four  hours,  and  yield  73,000  kilos,  of  work-lead.  If  the  slag,  which  is  daily 


172 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


PbS 

Cu2S 

Sb2Ss 

FeS 

NiS 

Si02 


9-24 

i'9S 
0*40 

32-34 
0-40 
0-31 


tested  in  an  iron  crucible  with  borax,  soda,  and  a  little  tartar,  yields  more  than  0*7  lead, 
it  is  re-smelted.     The  matte  is  ground,  roasted,  and  mixed  with  the  raw  ores. 

Matte.  Lead  Slag.  Work-Lead. 

Si02         .  .  27*00  Silver     .         .     0-0215 — 0-0250 

P205         .  .  3-79  Copper   .        .     0-1332—0-1396 

A12O,        .  .  5'6i  Antimony       .     0-2180 — 0-1586 

CaO          .  .  20-30  Iron        .         .     0-030  — 0-014 

Sulphur  .  .  1*26  Nickel    .         .     trace 

Lead        .  .       1-02  Zinc        .        .    o'oo6 

Copper    .  .  0-35 

Antimony  .  trace 

Iron          .  .  25-81 

Manganese  .  0-62 

Flue-dust. — According  to  Freudenberg,  the  deposit  of  flue-dust  is  proportional  to 
the  temperature  of  the  gases  and  the  size  of  the  surface  of  the  walls.  Hence  the 
deposit  decreases  more  rapidly  in  the  upper  compartments  of  the  chambers  than  in  the 
lower.  The  proportions  of  silver,  zinc,  and  antimony  are  greatest  near  the  furnace, 
and  decrease  with  the  length  of  the  flues.  Samples  taken  contained  60-5  to  67  per 
cent,  of  lead,  3-2  to  4*2  zinc,  0*003  silver,  14-1  to  14*8  sulphuric  acid,  5-4  to  6'2  sulphur, 
i  to  2'i  ferric  oxide  and  alumina,  5-8  to  8  coal,  0-3  to  o'4  antimony,  o'i6  to  0*24 
arsenic,  and  o'6  to  4-1  lime.  It  appears,  further,  that  the  quantities  of  metals  deposited 
in  the  smoke-channels  as  flue-dust  are  proportional  to  the  square  surface  of  the  sides 
of  the  flues.  He  recommends,  therefore,  that  metal  sheets,  &c.,  should  be  suspended 
parallel  to  the  direction  of  the  draught.  Schlosser  proposes  the  use  of  refrigerating 
pipes,  and  Walker  that  of  electricity,  which  latter  process  is  said  to  have  proved  unsuc- 
cessful. 

Work-lead. — The  work-lead  obtained  contains  silver,  copper,  antimony,  &c.  For 
the  separation  of  the  silver,  see  SILVER.  The  litharge  produced  is  either  used  as  such 
or  reduced  to  metallic  lead.  The  reduction  is  effected  in  a  reverberatory,  the  litharge 
being  mixed  on  the  hearth  with  charcoal.  The  lead  thus  obtained  contains  a  little 
copper,  antimony,  and  perhaps  some  silver.  It  is  therefore  less  soft  than  lead  produced 
from  pure  litharge.  The  composition  of  different  sorts  of  Freiberg  leads  appears  from 
the  following  analyses  by  Reich  : — 


i. 

3. 

3- 

4- 

&• 

Lead    . 
Arsenic 

97-72 
1-36 

99-28 

O'i6 

87-60 
7-90 

90-76 
1-28 

87-60 
0*40 

Antimony 

0-72 

trace 

2-8o 

7'3i 

1  1  -60 

Iron 

0-07 

0-05 

trace 

0-13 

trace 

Copper 
^Silver  . 

0-25 
0-49 

0-25 
0'53 

0*40 

o'35 

trace 

Electric  Production  of  Lead. — The  process  of  Bias  and  Miest  is  based  on  the  fact 
that  the  native  sulphides  conduct  electricity  when  they  are  compressed  into  plates,  with 
the  aid  of  heat.  To  this  end  zinc  blende,  galena,  &c.,  are  comminuted  to  grains  of  about 
5  millimetres  in  diameter,  pressed  into  plates  in  metal  moulds,  under  a  pressure  of  100 
atmospheres,  heated  to  600°  in  a  furnace,  pressed  again  and  quickly  cooled,  that  they 
may  be  easily  extracted  from  the  moulds.  Plates  of  galena  thus  obtained  are  suspended 
as  anodes  in  a  bath  of  lead  nitrate.  There  is  here  little  chemical  work  to  be  performed, 
as,  according  to  PbfNO,),  +  PbS  =  Pb(NOa),  +  Fb  +  S,  the  work  needed  at  the  negative 
pole  for  the  decomposition  of  the  lead  nitrate  is  compensated  at  the  positive  pole,  so 
that  chemical  work  is  needed  only  for  decomposing  the  lead  sulphide;  hence,  for  i  kilo, 
lead  18-328  :  207  =  89  heat-units.  If  we  take  into  account  resistance,  transportation 


SKCT.  ii.]  LEAD.  173 

of  ions,  &c.,  or  only  a  30  per  cent,  utilisation  of  the  power  of  the  machine,  we  should 
have  hourly  for  each  horse-power  2  kilos,  of  lead  and  an  equivalent  quantity  of  sulphur. 
Practically  speaking,  the  matter  is  still  involved  in  difficulties. 

Keith's  process  for  refining  lead  by  electrolysis  is  carried  out  by  the  Electrometal 
Refining  Company  of  New  York.  In  each  of  a  set  of  30  vats,  i  metre  in  height  and 
1*83  metre  wide,  there  are  immersed  as  kathodes  13  cylinders  of  thin  sheet  brass, 
arranged  concentrically,  so  that  they  are  o'6i  to  1*83  metre  in  diameter.  They  are 
immersed  to  a  depth  of  o'6  metre.  The  crude  lead,  smelted  in  a  reverberatory,  is 
poured  into  12  moulds  61  centimetres  long,  15  broad,  and  3  millimetres  in  thickness,  to 
form  plates  for  the  anodes.  The  solution  of  lead  sulphate  (nitrate  ?)  and  sodium  acetate 
is  forced  from  below  continuously  into  the  vats,  through  wooden  pipes  laid  below  the 
vats,  whilst  it  flows  off  above  to  be  heated  in  a  cistern  to  38°  by  means  of  steam  pipes, 
and  again  conveyed  to  the  vats,  so  that  it  is  in  constant  circulation.  The  muslin  bags 
enclosing  the  anodes  retain  silver,  along  with  arsenic,  antimony,  &c.  The  silver  is 
melted  along  with  saltpetre  and  soda.  The  lead,  before  and  after  this  treatment,  has 
the  following  composition  : — 

Crude.  Refined. 

Lead 96*36  ...  99-9 

Silver 0-554  ...  0-00007 

Copper          ....      0-315  ...  o 

Antimony     ....       1-070  ...  trace 

Arsenic         .        .        .        .1-22  ...  trace 

Zinc  and  Iron       .         .         .       0-489  ...  o 

If  12  h.-p.  are  used,  10  tons  of  lead  are  refined  in  24  hours,  in  48  vats,  each  containing 
50  plates  weighing  each  16  kilos.  Consequently,  if  i  h.-p.  requires  1*75  kilos,  of  coal 
hourly,  67-1  kilos,  of  coal  are  used  per  ton  of  lead. 

Properties. — Lead  as  it  occurs  in  commerce,  refined  and  Pattinsonised,  has  a  peculiar 
light  grey  colour.  It  is  little  disposed  to  assume  a  crystalline  texture,  and  has  on  its 
fracture  a  uniformly  melted  appearance.  In  certain  metallurgical  processes  it  may  be 
obtained  crystallised  in  the  forms  of  the  tesseral  system  (combination  of  cubes  and 
octahedra).  Lead  is  distinguished  by  softness  and  flexibility ;  hence,  it  has  a  somewhat 
high  degree  of  malleability,  but  little  absolute  tenacity.  If  freshly  scraped  or  cut,  it  is 
very  brilliant,  but  it  soon  becomes  dull  on  exposure  to  the  air.  It  marks  strongly  on 
the  hands,  on  paper,  and  on  linen  fabrics.  The  spec.  gr.  of  refined  lead  is  1 1*370 ;  that 
of  cast  lead,  11-352,  and  that  of  rolled  lead,  11-358.  In  the  manufacture  of  sheet  lead 
oxidation  has  to  be  avoided.  Lead  is  one  of  the  easily  fusible  metals  ;  it  solidifies  quietly, 
i.e.,  without  spirting,  and  with  a  concave  surface.  If  heated  almost  to  the  melting- 
point  it  becomes  brittle,  and  breaks  under  the  hammer  in  fragments  of  a  peculiar  rod- 
like  structure.  If  heated  to  a  certain  degree,  it  may  be  pressed  into  solid  or  hollow 
cylinders :  the  former  serve  for  projectiles  and  the  latter  for  pipes,  which  are  now 
manufactured  on  a  large  scale.  At  a  full  white  heat,  and  if  air  is  excluded,  it  enters 
into  ebullition  and  evaporates.  Lead  takes  up  at  most  1*5  per  cent,  of  zinc  and  0-07  per 
cent,  of  iron,  but  so  much  the  more  copper  as  the  temperature  rises. 

The  uses  of  lead  are  very  various.  It  is  employed  in  the  form  of  rolled  plates  for 
roofing,  for  boiling-pans  for  sulphuric  acid,  copperas,  and  alum ;  lead  chambers  in  the 
manufacture  of  sulphuric  acid ;  water-  and  gas-pipes  and  retorts ;  in  thin  leaves  for 
wrapping  up  snuff;  in  the  manufacture  of  small  shot  and  bullets;  in  metallurgical 
processes  for  the  extraction  of  certain  metals,  e.g.,  silver  and  gold ;  for  the  production 
of  sugar  of  lead,  red  lead,  white  lead,  and  other  lead  preparations. 

Manufacture  of  Small  Shot. — Shot  is  remarkable  as  no  moulds  are  needed  in  its 
preparation.  It  consists  of  solidified  drops  of  lead.  The  lead  is  not  used  pure,  but 
alloyed  with  a  small  quantity  of  arsenic,  0-3  to  o-8  per  cent.,  which  gives  it  the  power 
of  granulating  more  easily.  Too  much  arsenic  gives  the  grains  a  flattened  aspect,  and 


i74  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

too  small  a  proportion  renders  them  longish.  The  arsenic  is  added  either  as  such,  as 
sulphide,  or  as  arsenious  acid.  If  it  is  used  in  the  last  state,  the  surface  of  the  lead 
is  covered  with  charcoal  powder,  the  heat  raised  to  redness ;  the  arsenic,  wrapped  in 
coarse  paper,  is  placed  in  a  basket  of  iron  wire,  plunged  into  the  melted  lead,  and  well 
stirred.  For  granulating  the  lead  there  are  used  iron  kettles,  with  a  flat  bottom, 
provided,  like  a  sieve,  with  round  holes  of  equal  diameter.  If  the  lead  were  at  once 
poured  into  the  kettles,  there  would  be  produced  more  oval  than  round  grains. 
There  is  therefore  placed  in  the  kettle  a  porous  mass,  which  attaches  itself  to 
the  sides,  and  keeps  the  lead  at  such  a  temperature  that  it  flows  through,  neither 
too  easily  nor  too  tardily.  The  substance  used  is  the  dross  drawn  off  from  the  surface 
of  the  molten  metal.  As  the  liquid  metal  oozes  through  this  mass,  and  flows  in  single 
drops  through  the  holes  in  the  kettle,  it  takes  a  globular  form  in  falling,  like  every 
other  liquid.  The  grains,  congealed  whilst  falling  from  a  great  height,  are  received  in 
water  which  holds  in  solution  in  100  parts  0-025  sodium  sulphide.  A  thin  film  of 
lead  sulphide  is  thus  formed  round  the  grains,  and  defends  them  from  oxidation. 

Alloys. — Soft  solder,  for  tinmen,  &c.,  consists  of  equal  parts  lead  and  tin ;  organ- 
pipe  metal  (96  parts  of  lead  and  4  of  tin) ;  antifriction  metal  (4  tin,  5^  lead,  and 
i  antimony) ;  hard  lead  (an  alloy  of  lead  and  antimony)  ;  the  alloy  for  ships'  nails  (3 
parts  tin,  2  lead,  i  antimony) ;  the  calain  of  the  Chinese,  used  in  foil  for  lining  tea- 
chests  (126  parts  lead,  17' 5  tin,  1*25  copper,  and  a  trace  of  zinc).  Other  alloys,  such 
as  type-metal,  are  mentioned  under  ANTIMONY. 

Production  of  Lead. — The  annual  production  of  lead  for  the  whole  of  Europe  was, 
in  1885,  330,000  to  350,000  tons,  and  that  of  North  America  120,000  tons.  The  annual 
average  consumption  of  lead  maybe  estimated  as: — North  America,  13  5,000  tons; 
Britain,  115,000  ;  France,  6500  ;  Germany,  45,000 ;  and  the  rest  of  the  world,  100,000 
tons :  in  all,  460,000  tons.  The  consumption  in  France  for  lead  pipes  and  lead  plates  has 
decreased  to  a  very  remarkable  degree. 

SILVER. 

Silver  occurs  in  nature  very  abundantly;  partly  metallic  (usually  auriferous); 
partly  combined  with  arsenic,  antimony,  tellurium,  and  mercury ;  partly  as  sulphide, 
mingled  with  other  sulphides ;  and  partly  as  a  chloride.  The  most  abundant  silver 
ores  are  : — Argyrose  (silver  glance),  Ag2S ;  argyrythrose  (dark-red  silver),  Ag3SbS3 ; 
proustite  (light-red  silver),  Ag3AsS3 ;  miargyrite,  Ag2SbsS4,  with  small  proportions 
of  copper  and  iron;  psaturose  (prismatic  melane  glance,  brittle  silver  sulphide), 
CuAg2S  +  Sb2S3 ;  polybasite,  [(Ag2SCu2S)9Sb2S3] ;  and  freieslebenite  [(FeS,ZnSCu2S)4, 
Sb,S3  +  (PbSAg2S)4Sb2S3]. 

As  chloride  (horn  silver),  AgCl2,  silver  occurs  in  some  quantity  in  Utah.* 

Lastly,  silver  occurs  in  galena,  which  contains  o'oi  to  0-03,  sometimes  0-5,  rarely 
i  per  cent. ;  in  copper  ores,  copper  pyrites,  chalkosine,  and  phillipsine,  with  0-020  to 
i 'i  per  cent,  of  silver;  in  cupriferous  pyrites  (from  which,  when  burnt,  silver  and 
copper  are  now  obtained) ;  in  the  fahl  ores,  in  blende,  and  calamine. 

Extraction. — Silver  is  obtained — 

I.  In  the  wet  way. 

1.  By  means  of  mercury  amalgamation. 

2.  By  solution  and  precipitation,  on  the  systems  of  Augustin,  Ziervogel,  and 

other  procedures. 

II.  In  the  dry  way. 

1.  Obtaining  argentiferous  lead. 

2.  Extraction  of  silver  from  argentiferous  lead. 

*  Silver  chloride  exists  in  solution  in  sea  water,  but  the  quantity  is  so  small  that  its  extraction 
is  not  remunerative. 


SECT,  ii.]  SILVER.  175 

Silver  is  rarely  smelted  out  from  its  ores,  which  can  be  undertaken  only  with  such 
as  are  rich  in  native  silver.  The  silver  thus  obtained  is  mostly  rich  in  gold,  and  is 
submitted  to  the  process  of  refining. 

Amalgamation. — The  extraction  of  silver  by  means  of  mercury,  or  the  amalga- 
mation process,  is  followed  in  the  case  of  very  poor  silver  ores  (argentiferous  copper 
matte,  speiss,  &c.). 

In  the  process  as  formerly  used  in  Europe,  10  per  cent,  of  common  salt  was  added 
to  the  ores  to  be  amalgamated,  and  the  mixture  was  roasted  to  drive  off  antimony 
and  arsenic.  By  the  mutual  action  of  the  salt  and  the  roasted  pyrites,  were  formed 
sodium  sulphide,  ferric  chloride,  and  escaping  sulphurous  acid ;  further  copper  sulphate, 
and  ferric  sulphate,  which  oxidised  the  untransformed  part  of  the  silver  sulphide 
to  silver  sulphate,  being  themselves  reduced  to  cuprous  and  ferrous  sulphates.  By 
the  action  of  the  residual  salt  were  formed  silver  chloride  and  sodium  sulphate. 
The  other  metals  present  were,  like  the  silver,  converted  into  chlorides.  When  the 
roasting  was  completed  the  brown  mass  was  ground  and  placed  in  the  amalgamation 
vats,  in  which  they  were  mixed  with  water,  scrap  iron,  and  mercury,  and  turned  for 
1 6  to  1 8  hours.  The  metals  were  precipitated  on  the  iron  and  became  amalgamated 
with  the  mercury. 

To  explain  the  nature  of  the  amalgamation  process,  let  us  suppose  that  a  silver 
ore  :  Cu2S,  Ag2S,  FeS  +  As2S3,  Sb2S3,  is  being  worked.  After  the  roasting  with  salt  there 
are  found  CujCl.,  2AgCl,  Fe012,  3Na2S04,  and  As203,  Sb203,  6S02. 

For  the  amalgamation  vats  there  are  produced  by  the  joint  action  of  the  iron, 
mercury,  and  water : 

Cu2012,2AgCl,FeCl2  +  Na2S04  +  2Fe  +  nHg  =  Na2S04  +  (Cu2,Ag2,nHg)  +  3FeCl3. 
The  amalgam  collects  at  the  bottom  of  the  vats,  and  is  let  off  by  means  of  a  spigot 
turning  downwards,  through  straining  cloths  of  ticking,  into  stone  troughs. 

In  order  to  separate  the  superfluous  mercury,  the  sack  is  tied  at  its  mouth  and 
pressed  between  boards.  The  solid  amalgam  remaining  in  the  bag,  and  containing  about 
1 1  per  cent,  of  silver  and  3  to  4  per  cent,  of  copper,  is  laid  on  iron  plates  in  the 
apparatus  for  distilling  mercury  (q.v.).  The  cupriferous  silver  (plate  silver)  is  left 
behind. 

The  American,  or  wet  amalgamation  (patio  process)  is  practised  in  Mexico,  Peru, 
Chile,  Bolivia,  and  in  the  Western  States  of  North  America.  The  silver  ores  are  stamped 
whilst  dry,  and  then  finely  ground  with  water.  The  stamped  ore  is  conveyed  to  the 
ore-mills  (Ai'rastras)  and  ground  with  the  addition  of  water.  The  thin  mud  is 
conveyed  to  a  court  (patio)  laid  with  stone  flags  slightly  sloping,  so  that  the  rain- 
water may  run  off.  The  ore-mud,  to  which  from  2  to  5  per  cent,  of  common  salt 
is  added,  is  well  trodden  by  mules  or  horses.  After  a  few  days  there  is  added 
magistral,  roasted  copper  pyrites,  therefore  essentially  copper  sulphate.  This  is  also 
well  trodden  in,  and  by  degrees  mercury  is  added,  about  six  times  the  weight  of  the 
silver  contained  in  the  ore  (Incorporation).  The  treading  is  continued  on  alternate 
days  for  a  term  of  two  to  five  months,  until  the  mass  seems  completely  de-silvered.  The 
mud  is  then  washed  in  cisterns  of  masonry  to  separate  the  amalgam,  which  is  freed 
from  superfluous  mercury  by  pressing  in  bags  of  ticking,  and  distilled  at  a  reduced 
pressure. 

In  the  amalgamation  process  as  generally  followed  in  America,  copper  chloride  and 
silver,  according  to  Rammelsberg,  form  cuprous  chloride  and  silver  chloride — 

2CuCl2  +  2Ag  =  2AgCl  +  Cu2012. 
Silver  sulphide  is  completely  decomposed  at  a  boiling  heat  by  copper  chloride — 

Ag2S  +  Cud,  =  2AgCl  +  CuS. 

Sodium  chloride  has  a  solvent  action  upon  silver  chloride  and  accelerates  the  process  of 
decomposition.     Cuprous  chloride  and  silver  sulphide  yield  silver  chloride  and  dicuprous 


176  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

sulphide  :  Ag2S  +  Cu2Cl2  =  2AgCl  +  Cu2S.  If  cuprous  chloride  is  previously  dissolved 
in  sodium  chloride  the  transformation  is  more  rapid,  but  a  quantity  of  silver  chloride 
remains  in  the  liquid.  If  zinc  is  added  to  the  separated  mixture  and  the  solution  of 
common  salt  is  heated,  there  remains  a  mixture  of  z  molecules  silver  and  i  molecule 
CuaS.  Copper  chloride  and  arsenic  sulphide  yield  quickly  copper  sulphide  and  arsenious 
chloride  :  As2S3  +  aOuCl,  =  3CuS  +  2  AsCl3.  On  the  other  hand,  the  greenish  grey  deposit 
obtained  by  the  action  of  copper  chloride  upon  antimony  sulphide,  Sb2S3,  contains,  along 
with  sulphur  and  copper,  much  antimony,  as  also  chlorine  and  oxygen,  in  consequence 
of  the  decomposition  of  antimony  chloride  by  water  and  formation  of  oxychloride.  But 
a  great  part  of  the  antimony  remains  in  the  solution,  which  contains  sulphuric  acid. 
As  the  analysis  shows  that  the  separated  copper  and  chlorine  exist  in  the  same 
proportions  as  in  cuprous  chloride,  we  may  assume  that  the  rest  of  the  chlorine  has 
oxidised  a  part  of  the  sulphur.  Cuprous  chloride  and  antimony  sulphide  behave  in  a 
similar  manner,  but  the  copper  seems  to  be  present  chiefly  in  the  metallic  state  in 
the  matter  deposited,  which  also  contains  antimony  oxychloride  and,  on  standing, 
antimonic  acid  is  deposited  from  the  richly  cupriferous  nitrate.  Both  kinds  of  red 
silver  ore  (argyrythrose  and  proustite)  are  decomposed  by  cupric  chloride.  In  the 
separated  mass,  which  is  black  in  the  arsenical  ore  and  grey  in  the  antimonial,  there 
are  found  the  silver,  the  antimony,  but  only  half  the  arsenic.  The  silver  is  entirely 
found  as  chloride  in  argyrythrose,  but  only  to  the  extent  of  one  half  as  proustite  ;  the 
rest  of  the  deposit  consists  of  copper  sulphide  and  free  sulphur. 

Among  the  usual  modifications  of  the  amalgamation  process,  one  treats  the  ore  with 
water,  salt,  and  mercury,  in  presence  of  iron  or  copper ;  the  other  employs  water,  salt, 
copper  chloride,  and  mercury.  The  first  method  figures  in  the  tina  process,  using  a 
wooden  vat  with  an  iron  bottom,  and,  in  the  cazo-oder  calderon  process  worked,  with 
the  addition  of  salt,  in  wooden  or  stone  vessels,  and  the  washoe  process,  which  requires 
iron  kettles  and  runners.  The  two  latter  methods  require  the  aid  of  heat. 

The  second  method  comes  into  play  in  the  patio  process,  above  described ;  and 
characterised  by  the  use  of  magistral.  The  choice  of  the  two  principal  processes 
depends  on  the  chemical  character  of  the  ores.  The  first  requires  that  the  main  mass 
of  the  silver  should  be  native,  as  is  the  case  in  the  pacos  in  Peru,  in  the  metas 
calidos  in  Chile,  and  the  Colorados  in  Mexico,  which  often  contains  silver  chloride  and 
bromide.  The  silver  is  easily  amalgamated,  as  are  also  the  chloride  and  bromide  if 
copper  or  iron  is  present.  The  sulphur  compounds  existing  at  greater  depths — silver 
glance,  argentiferous  fahl-ores,  and  pyrites — must  be  treated  by  the  patio  process. 
Though  Rammelsberg's  experiments  prove  that  silver  sulphide  and  argyrythrose  can, 
under  favourable  circumstances,  be  reduced  by  copper  chloride,  it  is  still  very  doubtful 
whether  this  process  can  extract  the  whole  of  the  silver  from  sulphur  ores  on  the 
large  scale. 

The  Kroncke  process,  which  has  been  in  use  in  Northern  Chile  for  some  time, 
consists  in  amalgamation,  in  vats,  in  which  the  agents  are  cuprous  chloride,  zinc,  and 
mercury.  The  air  is  almost  excluded,  and  the  amalgamation  is  effected  within  a  few 
hours.  Experiments  have  shown  that  the  sulphur  ores  can  thus  be  completely  decom- 
posed, and  the  results  of  the  process  are  described  as  very  satisfactory. 

Extraction  of  Silver  "by  Solution  and  Precipitation. — The  ores  are  here  roasted, 
either  alone  or  after  the  addition  of  salt.  For  the  latter  method  the  roasting  furnace 
of  Stetefeld  has  proved  successful.  The  ore,  mixed  with  from  2-5  to  18  per  cent,  of 
sodium  chloride,  slides  down  in  the  shaft  B  (Fig.  178),  from  9  to  14  metres  in  height, 
meeting  at  0  the  hot  gases  coming  from  the  fires  at  6f,  whilst  air  enters  at  M.  The 
doors,  P  and  7?,  serve  for  watching  and  regulating  the  process.  The  roasted  ore  is  let 
fall  into  the  recipients,  N,  by  opening  a  trap,  C,  at  the  bottom,  and  is  here  slowly  cooled 
to  complete  the  chlorination.  The  gases  escape  through  the  shaft  H,  provided  with 


SECT.    II.] 


SILVER. 


177 


man-holes,  S,  and  additional  fire,  E,  in  order  to  deposit  their  flue-dust  in  the  funnels, 
F.  With  large  furnaces  and  great  quantities  of  ore  operated  upon,  50  per  cent,  of  the 
ore  collects  in  the  flue-dust  chambers,  of  which  80  per  cent,  settles  in  the  first  compart- 
ment. In  order  to  effect  the  chlorination  of  any  silver  that  has  escaped  the  action  of 
chloride  in  the  furnace,  the  flue-dust  chambers  are  only  emptied  occasionally,  the  last 
compartment  once  weekly.  The  escaping  gases  enter  a  chimney  not  less  than  16 
metres  in  height.  In  the  same  furnace  the  weight  of  ore  worked  iu  24  hours  is 


Fig.  178. 


Fig.  179. 


70  tons  of  ores  poor  in  sulphur, 
but  only  30  tons  of  ores  of  such  as 
contain  pyrites  and  blende.  As 
the  roasting  is  very  rapid  the  loss 
of  silver  here  is  said  to  be  smaller 
than  in  a  reverberatory.  The 
coarseness  or  fineness  of  the  ore 
is  regulated  by  the  manner  in 
which  it  is  to  be  afterwards 
treated.  If  the  ore  is  intended 
for  amalgamation  it  must  be 
ground  more  finely  than  if  it  is 
to  be  submitted  to  lixiviation 
(with  sodium  thiosulphate)  as  mercury  cannot  be  entirely  washed  out  from  coarsely 
ground  ores.  The  rotatory  fvirnace  of  Bruckner  is  used  in  many  places.  The  modi- 
fication proposed  by  Arent  (Fig.  179)  has  the  object  that  in  the  part  of  the  cylinder, 
c,  situated  nearest  to  the  fire,  A,  the  ore  is  more  heaped  up  than  towards  d.  The 
revolving  furnace  is  filled  through  the  hopper,  e,  and  the  aperture,  o,  and  emptied 
through  p  into  the  iron  chest,  k,  or  the  recipient,  f,  provided  with  a  sliding  door,  g. 
The  rotation  is  effected  by  the  rollers,  I,  and  the  cast-iron  rings,  ra. 

Augustiris  Process. — The  most  ancient  hydro-metallurgical  process  for  extracting 
silver  is  that  of  Augustin — the  so-called  salt  lixiviation.  It  depends  on  the  formation 
of  an  easily  soluble  double  chloride  when  silver  chloride  is  brought  in  contact  with 
an  excess  of  strong  solution  of  common  salt  with  the  aid  of  heat,  and  on  the  power  of 
copper  to  expel  the  silver  completely  from  the  saturated  solution  of  this  compound. 
The  copper-matte,  consisting  chiefly  of  silver,  copper,  and  iron  sulphides,  are  reduced 
to  fine  powder  by  stamping  and  grinding,  and  are  roasted  at  first  without  salt.  There 
is  then  formed,  first  iron  sulphate,  then  copper  sulphate,  and  lastly,  as  the  temperature 
is  raised,  silver  sulphate,  by  which  time  all  the  iron  sulphate  and  a  great  part  of  the 
copper  sulphate  are  decomposed,  so  that  the  mixture  at  the  end  of  this  preliminary 


1 78  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

roasting  consists  of  iron  oxide,  copper  oxide,  and  small  quantities  of  copper  sulphate. 
By  continuous  roasting  with  common  salt  the  silver  sulphate  is  converted  into  silver 
chloride.  The  mass  is  then  lixiviated  with  a  hot  saturated  solution  of  salt,  which 
dissolves  the  silver  chloride.  From  the  liquid  the  silver  is  precipitated  by  metallic 
copper,  and  the  copper  is  recovered  from  the  coppery  solution  by  means  of  metallic 
iron. 

(For  the  extraction  of  silver  from  burnt  pyrites  see  SULPHURIC  ACID.) 

Ziervoyel's  Process. — In  this  lixiviation  process  no  salt  is  added  on  roasting.  The 
roast  ore,  consisting  mainly  of  silver  sulphate,  a  little  copper  sulphate,  much  copper 
oxide  and  iron  oxide  is  extracted  with  hot  water,  which  dissolves  the  silver  and  copper 
sulphates.  From  this  solution  silver  is  precipitated  by  metallic  copper,  and  copper 
sulphate  is  obtained  as  a  by-product. 

At  Mansfeld  this  process  has  been  in  use  for  many  years  for  desilverising  copper 
matte.  The  lixiviation  is  rapidly  effected  ;  whence  there  is  a  less  outlay  for  fuel  and  for 
labour  than  in  the  Augustin  process.  On  the  other  hand,  the  roasting  is  less  easily 
effected,  richer  materials  are  needed,  and,  as  a  rule,  the  residues  are  richer.  In 
presence  of  arsenic  and  antimony  the  Ziervogel  process  is  inapplicable,  since  on 
roasting  there  are  formed  silver  arseniate  and  antimoniate,  insoluble  in  water.  The 
presence  of  lead  easily  leads  to  fritting,  which  makes  the  roasting  difficult. 

Other  Procedures. — Of  late  ores  of  gold  and  silver  have  been  extracted  with 
sodium  thiosulphate  (formerly  known  as  hyposulphite  of  soda).  This  process  is  in 
use  in  California  and  Nevada,  after  the  ores  have  been  roasted  with  3  per  cent,  of 
common  salt  :  AgCl  +  Na2S203  =  NaCl  +  NaAgS203.  The  solution  is  mixed  with  a 
solution  of  calcium  sulphide  : 

2NaAgS203  +  2NaCl  +  CaS  =  Ag2S  +  2Na2S203  +  CaCl2. 

The  lye  drawn  off  from  the  precipitated  silver  sulphide  is  used  again.  Care  must 
be  taken  that  no  excess  of  calcium  sulphide  is  present,  as  this  would  subsequently 
occasion  a  precipitation  of  the  dissolved  silver  in  the  lye-vats  in  the  state  of  silver 
sulphide.  Such  silver  would  not  be  redissolved  in  the  thiosulphate,  and  would  conse- 
quently be  lost.  If  the  ore  contains  gold  it  is  preferable  to  use  calcium  thiosulphate. 
This  salt  is  prepared  by  boiling  lime  with  sulphur,  3CaO+ 128=  2CaS5  +  CaS203, 
letting  the  solution  subside,  and  passing  sulphurous  acid  into  the  clear  lye  till  the  sulphide 
is  converted  into  thiosulphate  and  a  dilute  solution  of  silver  is  no  longer  precipitated. 

According  to  Russel,  ores  which  contain  silver  in  combination  with  arsenic  and 
antimony,  and  from  which  the  precious  metals  cannot  be  extracted  by  lixiviation  with 
sodium  thiosulphate,  can  be  treated  either  at  once  or  after  mixing  with  thiosulphate, 
with  a  solution  produced  by  mixing  thiosulphate  with  a  solution  of  copper,  preferably 
copper  sulphate.  There  is  formed  according  to  the  equation  : 

4Na2S203  +  2CuS04  =  aCuS,O,.Na,S,O,  +  2Na2S04  +  Na2S203, 
a  sodium  copper  thiosulphate,  in  which  silver  is  easily  substituted  for  copper. 

Extraction  of  Silver  in  the  Dry  Way. — The  extraction  of  silver  from  its  ores  by 
means  of  lead  depends — (a)  On  the  property  of  lead  to  act  upon  silver  sulphide  with 
formation  of  lead  sulphide  and  separation  of  metallic  silver.  Other  sulphides  accom- 
panying the  silver,  especially  copper  and  iron  sulphides,  are  less  readily  decomposed  by 
lead.  The  products  of  the  fusion  are  argentiferous  lead  and  a  matte  free  from  silver, 
but  containing  lead,  copper,  and  iron  sulphides.  The  extraction  of  silver  by  lead  is  the 
more  complete  the  poorer  are  the  ores  in  copper. 

(b)  On  the  decomposing  action  of  lead  oxide  or  lead  sulphate  upon  silver  sulphide : 

Ag2S  +  2PbO  =  Pb2Ag2  +  SO,. 

(c)  On  the  reducing  action  of  lead  upon  silver  oxide  or  silver  sulphate : 

3Pb  +  Ag2SO4  =  PbAg2  +  2PbO  +  S02. 

(d)  On  the  greater  affinity  of  silver  for  lead  than  for  copper.      If  argentiferous 


.SECT,  ii.]  SILVER.  179 

copper  is  melted  up  with  lead  there  is  formed  an  easily  fusible  argentiferous  lead  and 
an  alloy  of  copper  and  lead  which  melts  with  difficulty.  The  former  can  be  separated 
from  the  latter  by  eliquation. 

To  this  process  there  are  subjected  genuine  silver  ores,  roasted  pyritic  ores,  argenti- 
ferous copper  and  lead  ores  raw  or  roasted,  and  roasted  argentiferous  native  arsenic. 
The  essential  feature  of  the  process  is  the  treatment  of  the  materials  with  melted  lead. 
An  argentiferous  work-lead  is  formed  just  as  in  the  treatment  of  galenas  containing 
.silver. 

The  treatment  of  the  work-lead  may  be  effected  (i)  on  the  refiner's  hearth,  (2)  by  the 
Pattinson  process,  and  (3)  by  the  Parkes  process  (by  means  of  zinc). 

The  refining  on  the  hearth  turns  on  the  fact  that  the  readily  oxidisable  lead  is 
separated  by  a  simple  oxidising  fusion  from  the  non-oxidisable  metals,  care  being  taken 
that  the  lead  oxide  formed  is  partly  drawn  off  and  partly  absorbed  into  the  pores  of 
the  hearth.  The  surface  of  the  metallic  bath  is  oxidised  as  long  as  the  alloy  contains 
lead,  and  the  silver  remains  behind. 

The  hearth  is  a  round  reverberatory,  with  a  fire-box  F  built  up  to  it  (Fig.   180). 

'The  hearth  A  is  covered  with  a  hood  a, 

Fig.  1 80 
of  sheet-iron,  lined  with  fire-clay  B  which 

•can  be  raised  or  lowered  by  the  arrange- 
inent  D.  The  hearth  is  made  of  lixi- 
viated ashes,  or  preferably  of  calcareous 
marl ;  in  the  middle  is  a  depression 
to  collect  the  silver.  In  the  space  sur- 
rounding the  health  is  the  litharge-hole, 
•during  working  kept  closed  with  the 
same  material  of  which  the  hearth  is 
made  so  far  that  it  is  on  the  same  level 
as  the  upper  surface  of  the  melted  lead  in 
the  furnace,  so  that  the  litharge  formed 
upon  the  metal  may  flow  off.  As  soon  as  the  quantity  of  the  work-lead  decreases  the 
mass  in  the  litharge-hole  is  partially  removed ;  this  channel-like  depression  is  called 
the  litharge  road.  The  hole  P  opposite  the  fire-bridge  serves  for  introducing  the 
hearth-mass  and  the  materials.  The  tuyeres  of  the  blast  open  at  a. 

The  refining  is  continued  until  the  silver  on  the  hearth  is  covered  only  with  a  thin 
film  of  litharge,  which  disappears  as  rapidly  as  it  is  formed.  The  formation  and  dis- 
appearance of  the  film  is  recognised  by  a  play  of  colour — the  brightening  of  the  silver. 

As  soon  as  this  phenomenon  is  recognised  the  firing  is  ceased,  the  silver  is  cooled 
by  sprinkling  with  water,  and  lifted  out  of  the  furnace.  The  liquid  lead-oxide  flowing 
off  congeals  on  cooling  to  a  foliaceous  crystalline  mass  of  a  yellow  or  reddish- 
yellow  colour,  litharge. 

The  Pattinson  Process. — The  rule  holds  good  that  work-lead  with  a  percentage  of 
silver  less  than  0-12  cannot  be  further  refined  by  cupellation.  The  process  indicated  by 
Pattinson  (in  1883)  is  based  on  the  phenomenon  that  if  we  melt  a  sufficient  quantity 
of  lead  in  an  iron  kettle  and  let  the  liquid  mass  cool  uniformly  there  are  formed  small 
octahedral  crystals  which  cohere  at  their  ends.  These  crystals  are  much  poorer  in 
silver  than  the  original  alloy,  whilst  the  silver  is  concentrated  in  the  part  which 
remains  liquid.  If  we  melt  these  crystals  and  proceed  as  before,  there  are  again 
formed  crystals,  which  are  still  poorer  than  the  foregoing.  By  a  succession  of  such 
separations  the  lead  is  resolved  into  two  portions,  a  small  part  rich  in  silver,  rich  lead 
(containing  0-5  to  1-5  per  cent,  of  silver),  and  a  larger  portion,  very  poor  lead  (contain- 
ing o-oo i  to  0-003  per  cent,  of  silver).  As  the  limit  up  to  which  the  lead  can  be 
•enriched  by  the  Pattinson  process,  we  may  fix  2*5  per  cent,  of  silver. 


i8o 


CHEMICAL  TECHNOLOGY. 


[SECT.  IT. 


A  desilvering  of  lead  by  means  of  zinc  was  proposed  by  Parkes  in  1850. 

Work-lead  is  placed  in  an  iron  pan ;  when  melted  5  per  cent,  of  melted  zinc  is 
added,  and  after  thorough  stirring  the  mixture  is  let  stand  until  the  zinc  congeals  to  a 
cake,  which  is  lifted  off.  The  zinc  in  the  earlier  process  was  separated  from  the  silver 
by  distillation.  After  the  completion  of  the  distillation  the  residue  is  taken  out, 
mixed  with  some  lead,  and  refined  on  the  hearth.  According  to  a  modification,  intro- 
duced by  Cordurie,  the  zinc  is  oxidised  by  superheated  steam  (Zn  -f  H20  =  ZnO  +  H2). 
The  zinkiferous  work-lead  left  after  being  thus  desilverised  is  freed  from  zinc  by  heat- 
ing with  lead  chloride,  as  a  mixture  of  lead  sulphate  and  sodium  chloride,  then  lead 
chloride  is  formed  (Zn  +  PbCL,  =  ZnCl2  +  Pb).  According  to  Flach's  proposal  the  zink- 
iferous lead  is  treated  with  puddling  slags  in  a  shaft-furnace  to  scorify  and  volatilise 
the  zinc.  The  zinc  process  has  become  almost  universal  in  Britain,  France,  and 
Germany. 

The  advantages  to  which  this  process  is  indebted  for  its  rapid  introduction  consist, 
according  to  Plattner,  especially  in  the  circumstances  that — 

1.  The  process  does  not  require  the  work-lead  to  be  previously  refined,  so  far 

as  the   removal   of   inconsiderable   quantities   of   copper,  arsenic,   and 
antimony  is  concerned ; 

2.  The  work  is  effected  with  only  small  quantities  of  intermediate  products ; 

3.  That  it  requires  a  smaller  apparatus  with  fewer  workmen  and  a  reduced 

outlay  for  fuel ; 

4.  That  it  effects  the  separation  of  silver  from  lead  in  much  shorter  time  than 

the  Pattinson  process ; 

5.  That  it  yields  a  decidedly  smaller  and  proportionally  richer  quantity  of  rich 

lead,  to  be  refined ;  and  lastly, 

6.  That  the  process  involves  a  more  moderate  loss  of  lead. 

A  further  advantage  of  the  Parkes  process  is  that  a  minimum  proportion  of  gold, 
present  in  the  work-lead,  can  be  first  extracted  by  a  small  addition  of  zinc,  and  a  zinc 
scum  obtained  which  furnishes  a  small  quantity  of  auriferous  silver,  whilst  the 
subsequent  main  quantity  of  silver  extracted  by  a  second  treatment  with  zinc  is  free 
from  gold. 

At  the  Mulden  Works  at  Freiberg  the  Pattinson  and  Parkes  processes  are  combined 
in  such  a  manner  that  the  former  process  is  interrupted  in  that  pan  where  it  is  expected 
that  bismuth  may  be  obtained,  which  passes  into  the  rich  lead.  In  the  Pattinson 
process  there  is  here  employed  a  battery  of  9  cast-iron  pans,  each  of  1-75  metre 
diameter  at  top,  0*90  metre  in  depth,  and  receiving  each  a  charge  of  150  hectokilos. 
For  the  Parkes  process  (Figs.  181-184)  there  are  set  up,  with  separate  fires:  2  cast- 
Fig.  181. 


iron  desilvering  pans,  a,  of  1-98  metre  top-diameter,  i-o  metre  in  depth,  and  each 
holding  200  hectokilos.;  3  cast-iron  hemispherical  eliquation  pans,  b,  of  0-55  metre;  i 
refining  furnace,  c  with  a  fire-clay  hearth  3  metres  long,  2  metres  wide  and  0-45  metre 


SECT.    II.] 


SILVER. 


181 


deep  for  freeing  the  poor  lead  from  zinc,  and  i  cast-iron  pan,  d  of  1-9  metre  diameter 
at  top  and  i  metre  deep  to  receive  the  poor  lead  when  freed  from  zinc. 

The  apparatus  for  the  Parkes  process  is  so  united  with  the  Pattinson  apparatus 
that  the  two  desilvering  pans  and  the  three  eliquation  pans  of  the  Parkes  process,  placed 
at  the  same  level,  lie  with  their  edge  2  metres  higher  than  the  edge  of  the  Pattinson  pans, 

Fig.  182. 


JL 


so  that  the  zinkiferous  poor  lead  can  be  conveyed  by  means  of  syphons  (Fig.  185) 
whilst  still  liquid,  into  the  following  refining-furnace  placed  with  its  sole  2  metres 
lower  than  the  margin  of  the 
desilvering  pans.     The  pan  for 
the  de-zinkified  poor  lead  is  built 
in   with   its   margin    10    centi- 
metres  below  the   sole   of    the 
refining  furnace. 

From  it  the  poor  lead  can  be 
led  off  through  pipes  (which  can 
be  closed  by  a  conical  valve)  and 
a  movable  channel.  It  is  then 
run  into  cast  iron  moulds  to  give 
it  a  form  suitable  for  trade.  The 
conveyance  of  the  lead  from  the 
Pattinson  battery  and  of  other 
refined  work-leads,  poor  in  silver, 
to  the  level  of  the  desilvering 
pans  is  effected  by  a  simple  steam 
lift.  The  last  pan  of  the  Pat-  % 
tinson  battery  is  emptied  of  the 
work-lead  containing  o'i  per  cent,  of  silver  and  destined  for  the  Parkes  process  by  means 
of  the  Rosing  steam-pump.  For  mixing  in  the  zinc  there  is  used  an  agitating  scoop,  2-3 
metres  in  length  with  100  to  1 20  holes  to  let  the  lead  drop  through  (Fig.  186) ;  for  lifting 
off  the  zinc  scum  there  is  used  a  similar  scoop  with  a  shorter  handle.  For  distilling 


182 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


the  rich  scum  there  are  used  two  wind-furnaces  (Fig.  187)  with  a  round  shaft  0-75 
metre  in  width  and  0^9  metre  deep  down  to  the  level  of  the  grate.  On  the  movable 
ring  e,  of  angle  iron  and  strong  sheet  iron  lined  with  fire-clay  lies  a  cover,  f,  of  clay 
plates  resting  in  a  ring  of  angle  iron.  The  ring  and  the  cover  can  be  lifted  off  either 
separately  or  jointly  by  means  of  pulleys. 

The  graphite  crucible  is  55  centimetres  high,  with  sides  5  centimetres  thick;  the 


Fig  185. 


cover,  of  graphite,  A,  20  centimetres;  the  graphite  pipe,  i,  is  50  centimetres  in  length, 
with  sides  2-5  centimetres  in  thickness.  The  iron  receiver  k,  ^  metre  in  height  rests  on 
an  iron  bottom  plate  and  has  a  movable  lid.  All  the  refined  work-leads  containing 
more  than  0*1  per  cent  of  silver,  if  not  worth  separate  treatment  on  the  hearth,  are 
conveyed  to  a  pan  of  the  Pattinson  battery,  according  to  their  proportion  of  silver,  and 
are  there  worked  to  a  rich  lead  of  2  per  cent,  and  a  poor  lead  of  o'i  per  cent.  The 
rich  lead  goes  to  the  refinery  hearth  and  the  poor  lead  to  the  Parkes  process. 

To  desilver  this  work-lead  by  means  of  zinc,  after  the  lead  has  been  fused  in  the 
desilvering-pan,  the  solid  pieces  formed  are  lifted  off  with  the  scum  scoop,  until  the 
lead -bath  has  a  perfectly  clean  surface.  When  the  lead  has  been  heated  up  to  the  melting 
point  of  zinc  (by  means  of  a  cover),  the  first  addition  of  zinc  takes  place.  When  it 
has  been  thoroughly  stirred  into  the  lead,  the  mixture  of  metals  is  left  undisturbed 
until  a  crust,  about  3-4  centimetres  in  breadth,  has  been  formed  at  the  edge  of  the 
pan.  The  zinc  scum,  which  has  come  to  the  surface  and  covered  it,  must  be  lifted  off 
with  the  perforated  scoop,  letting  the  adhering  lead  carefully  drop  back.  The  zinc 
scum  from  the  first  additions  of  zinc  being  rich  in  silver  (rich  scum)  is  transferred  to 
the  adjacent  eliquation  pans,  whilst  the  scum  poorer  in  silver  (poor  scum),  obtained 
from  the  subsequent  additions  of  zinc,  is  thrown  into  iron  pans,  and  is  afterwards 
used  in  desilvering  a  fresh  charge  of  work-lead,  so  as  to  utilise  its  zinc.  At  the  same 
time  that  the  scum  is  removed,  the  fire  under  the  pan  is  strengthened,  in  order  to  give 
the  lead  the  high  temperature  required  for  the  next  addition  of  zinc.  The  entire 
treatment  is  repeated  as  often  as  additions  of  zinc  are  necessary,  in  order  to  extract  the 
silver  from  the  work-lead,  and  convert  it  into  poor  lead. 

After  the  (supposed)  last  skimming,  the  sides  of  the  pan  are  carefully  scraped  with 
a  chisel,  in  order  to  remove  any  adhering  scum  and  bring  it  to  the  surface,  lest  the 
accuracy  of  the  determination  of  silver  in  the  poor  lead  should  be  endangered.  An 
intensified  fire  promotes  the  fusion  of  the  scum.  Before  each  fresh  addition  of  lead  the 


SECT,  ii.]  SILVER.  !83 

metallic  bath  is  well  stirred  up,  and  several  samples  of  lead  are  taken  from  the  middle 
with  a  sampling-spoon,  cast  into  ingots,  and  tested  for  their  contents  of  silver.  If  the 
assay  gives  a  result  of  o'ooi  per  cent,  no  more  zinc  is  added,  and  the  process  is 
regarded  as  complete.  As  soon  as  the  zinkiferous  poor  lead  has  been  rendered 
sufficiently  hot,  it  is  drawn  off  from  the  pan  (by  means  of  the  syphon,  previously 
heated  and  filled  with  melted  lead)  into  the  sheet-iron  gutter,  leading  to  the  hearth  of 
the  refining  furnace,  and  the  desilvering  pan  when  empty  is  filled  again  for  a  new 
operation. 

Simultaneously  with  the  desilvering,  goes  on  the  eliquation  of  the  rich  scum  in 
the  first,  and  afterwards  in  the  second,  eliquation  pan.  The  argentiferous  zinkiferous 
lead  obtained  by  this  process  goes  back,  like  the  poor  lead,  to  the  desilvering  process, 
whilst  the  rich  silver  scum,  which  has  been  taken  off,  is  reserved  for  distillation.  The 
average  time  needed  for  melting  the  work-lead  and  taking  off  the  cakes  is  five  hours, 
and  for  each  period  of  the  desilvering,  i.e.,  from  one  addition  of  zinc  to  the  next,  is 
altogether  five  hours,  namely  : 

hr.    min. 

Heating  the  lead-bath 115 

Adding  and  melting  zinc o    45 

Stirring  in  zinc     .        .        .        .        .        .        .    o    30 

Cooling  metallic  bath 20 

Lifting  off  zinc  scum  o    30 

As  for  the  work-lead  from  the  Pattinson  process  containing  o'i  per  cent,  of  silver 
at  the  most  three  additions  of  lead  are  sufficient  ;  the  duration  of  the  desilvering  of 
such  work-lead,  the  time  required  until  a  zinkiferous  poor  lead  is  produced,  may  be 
taken  at  the  most  as  twenty  hours. 

Every  charge  of  200  hectokilos.  (20  tons)  of  work-lead  of  the  above-mentioned  per- 
centage of  silver,  with  the  additional  use  of  the  zinkiferous  eliquation  lead  and  the 
poor  scum,  requires  for  desilvering,  215  kilos,  of  zinc,  100  kilos,  for  the  first  addition, 
75  for  the  second,  and  40  for  the  third.  The  addition  of  zinc  required  for  desilvering 
runs  up  to  1-485  per  cent.,  whilst  the  actual  consumption  of  zinc,  deducting  that 
recovered  on  the  distillation  of  the  rich  scum,  is  only  0-832  per  cent.,  the  original 
proportion  of  silver  o'i  per  cent.,  and  the  gold  averaging  0*0004  per  cent,  of  the  work- 
lead,  is  reduced  after  the  first  addition  of  zinc  to  0-0250  silver  and  a  trace  of  gold  ; 
after  the  second  to  <roo2o  silver,  and  after  the  third  to  0-0007  per  cent,  silver,  and 
no  gold.  As  a  rule,  the  decrease  of  the  proportion  of  silver  is  most  striking  after 
the  first  addition  of  zinc,  whilst  the  last  small  quantities  of  silver  are  more  difficult  to 
remove.  The  process  is  essentially  abbreviated  if  the  first  addition  of  zinc  is  made  as 
large  as  practicable.  The  cost  of  the  zinc  is  not  increased,  as  there  is  effected  an  economy 
in  the  subsequent  additions  of  zinc,  as  well  as  in  time.  The  gold  generally  disappears 
after  the  first  addition  of  the  zinc,  as  it  combines  with  the  zinc  more  readily  than  does 
silver. 

Work-lead  gives  after  desilvering  the  following  products  : 

o-35  per  cent,  cakes  from  melting,  with  an  average  contents  of  0^0004  per  cent,  gold  and  o-io 

per  cent,  silver, 

2*25  per  cent,  rich  scum  for  distillation,  with  an  average  contents  of  0-0153  Per  cent,  gold, 
4-0510  per  cent,  silver,  53-2  per  cent,  lead,  2'68  per  cent,  copper,  and  397  per  cent,  zinc; 
that  is  : 

1-73  per  cent,  of  rich  scum  I.  with  0-0174  per  cent,  gold,  and  4-670  silver, 
0-31  per  cent,  rich  scum  II.  with  O"ooi6  per  cent,  gold,  and  2-53  silver, 
0-21  per  cent,  rich  scum  III.  with  a  trace  of  gold,  and  1-130  per  cent,  of  silver, 
besides  98-95  per  cent,  of  zinkiferous  poor  lead  for  de-zinking  with  an  average  contents  of  0-0007 
per  cent,  of  silver  and  075  per  cent.  zinc. 

There  are  returned  to  the  process  :  1-5  per  cent,  eliquated  lead,  containing  on  the 


1 84  CHEMICAL  TECHNOLOGY.  [SECT-  u- 

average  a  trace  of  gold,  0*032  per  cent,  silver,  and  1*3  per  cent.  zinc.  Poor  scum  is 
not  formed  because  the  zinc-scum  obtained  after  the  third  addition  of  zinc  gives  on 
eliquation  the  above  rich  scum  III.,  containing  a  moderate  amount  of  silver  and 
capable  of  useful  distillation.  The  quantities  of  the  eliquated  rich  scum  increase  with 
the  proportion  of  silver  in  the  work-lead,  and  the  silver  in  the  rich  scum  increases 
proportionally,  whilst  the  lead  in  the  normal  case  of  eliquation  remains  at  a  limit  of 
76-80  per  cent,  and  the  zinc  remains  between  20-24.  The  quantities  of  poor  scum 
remain  approximately  equal  in  all  sorts  of  work-lead,  since  the  silver  reduced  in  them 
by  repeated  additions  of  zinc  shows  the  essential  variations,  if  the  poor  scum  is  drawn 
off.  The  lead  reaches,  as  a  maximum,  90  per  cent,  and  the  zinc  6-9  per  cent.  The 
yield  of  eliquated  lead,  with  uniform  management,  keeps  step  with  the  quantities  of 
rich  scum,  and  must  increase  or  abate  in  a  corresponding  proportion,  according  as 
more  or  less  rich  scum  is  taken  off  in  consequence  of  the  higher  or  lower  proportion  of 
silver  in  the  material.  The  silver  in  eliquated  lead  is  uniformly  moderate,  since  the 
main  quantity  of  the  silver  is  kept  back  by  the  zinc  remaining  in  the  eliquated  rich 
scum,  and  the  small  quantities  of  silver  in  the  eliquated  lead  are  carried  over  only  by  the 
zinc,  which  passes  in.  The  zinc  fluctuates  between  i  and  1-5  per  cent.  The  zinki- 
ferous  poor  lead,  if  the  process  has  been  duly  conducted,  shows  a  constant  proportion 
°f  °'75  Per  cent,  of  silver,  whatever  quantities  of  zinc  were  required  for  desilvering 
the  work-lead.  The  total  gold  and  copper  of  the  work-lead  will  be  found  taken  up  in 
the  rich  scum,  so  that  all  subsequent  products  are  free  from  these  two  metals. 

For  L  ae  subsequent  de-zinking  in  the  refining  furnace,  the  zinkiferous  poor  lead 
which  has  gone  down  in  temperature  by  removal  from  the  desilvering-pan  to  the 
refining  furnace  must  be  heated  to,  and  maintained  at,  redness.  There  is  soon  formed 
by  the  oxidising  influence  of  the  blast  upon  the  surface  of  the  lead-bath  a  film  of  lead 
and  zinc  oxide,  as  a  thin  crust  which  must  be  drawn  off  with  a  crutch  through  the 
working  doors  to  keep  the  surface  of  the  lead  clean.  This  drawing  off  the  films  must 
continue  until  pure  litharge  appears  as  the  product  of  oxidation,  when  the  de-zinking 
process  is  at  an  end.  The  tap-hole  in  the  refining  furnace  is  then  opened  and  the 
lead  is  run  off  into  the  poor  lead  pan,  which  has  been  heated  in  the  meantime.  When 
the  cake  floating  upon  the  surface  has  been  lifted  off,  the  lead  is  finally  run  out 
through  the  escape  pipe  at  the  bottom  of  the  pan,  and  let  off  into  iron  moulds  as  the 
pure  lead  of  commerce.  If  two  desilvering  pans  are  worked  simultaneously,  the 
de-zinking  can  at  once  begin  in  the  refining  furnace  as  soon  as  the  former  lot  has  been 
let  off  into  the  poor-lead  pan. 

The  films  from  the  refining  furnace  and  the  lead-scum  from  the  poor  lead  pan,  as 
soon  as  a  sufficient  quantity  has  been  collected,  are  first  returned  to  the  refining 
furnace,  in  order  to  smelt  out  of  them  a  not  unimportant  quantity  of  lead,  and  then, 
much  reduced  in  weight  and  volume,  they  are  used  as  a  plumbiferous  addition  in  the 
treatment  of  the  ore.  The  refiner's  films,  when  ground,  form  a  good  pigment  for 
varnish -painting,  and  may  thus  be  partially  disposed  of.  The  poor  lead  yields  94-2 
per  cent,  commercial  lead  and  6-17  per  cent,  of  refinery  scum.  The  total  de-zinking 
process  from  running  the  poor  lead  into  the  refining  process  to  letting  off  the  de-zinked 
lead  requires  a  mean  of  nine  hours.  The  original  proportion  of  zinc  (075  per  cent.) 
in  the  zinkiferous  poor  lead  is  reduced  in  three  hours  to  0*16,  in  five  hours  to  o-oi,  in 
seven  hours  to  0-0008,  and  in  nine  hours  to  0*0002  per  cent. 

For  distilling  the  rich  scum  it  is  mixed  (after  being  kept  as  clean  as  possible) 
with  i  per  cent,  of  coarse  charcoal  powder ;  the  bottom  of  the  graphite  crucible  is  then 
covered  with  a  thin  layer  of  pieces  of  charcoal  of  the  size  of  a  walnut,  and  the  crucible 
is  then  filled  up  to  the  rim  with  rich  scum.  The  cover,  h,  coated  at  its  edge  with  a 
moist  lute  (of  i  part  clay,  i  part  ground  tiles,  and  i  part  ground  coke)  is  placed  upon 
the  crucible,  connected  with  the  receiver  k  (Fig.  187),  and  the  furnace  is  filled  with 


SECT,  ii.]  SILVER.  !85 

coke.  When  the  distillation  is  at  an  end  the  receiver,  containing  the  zinc  which  has 
passed  over  in  the  shape  of  a  lump,  is  moved  away,  the  grate  of  the  wind-furnace  is 
freed  from  slag  and  ashes,  the  ring  and  cover  of  the  shaft  are  drawn  away,  and  the 
lid  of  the  crucible  is  taken  off  as  quickly  as  possible,  since  when  cold  it  adheres  fast  to 
the  crucible  and  cannot  be  removed  without  the  risk  of  breakage.  As  soon  as  the 
crucible  has  ceased  giving  off  fumes,  the  residue  of  the  charcoal  and  the  unreduced 
scum  floating  on  the  surface  of  the  separated  rich  lead  are  lifted  off  by  means  of  a 
perforated  ladle,  and  the  rich  lead  itself  is  baled  out  into  cast-iron  pans.  After  this  is 
completed,  a  small  quantity  of  charcoal  is  again  laid  at  the  bottom  of  the  crucible,  and 
a  fresh  lot  is  introduced.  From  the  rich  scum  are  obtained  : — 

57'i7  per  cent,  rich  lead,  containing  O'oi86  per  cent,  gold,  and  7-35  per  cent,  silver. 

5-85  per  cent,  crucible  scrapings,  containing  0-0112  per  cent,  gold,  4*608  per  cent,  silver,  and 

3'5  per  cent,  copper, 
29'54  Per  cent,  metallic  zinc, 
6'35  per  cent,  zinc  in  7-22  per  cent,  zinc-dust  and  scrapings. 

With  careful  working,  50  per  cent,  of  the  zinc  run  over  can  be  recovered,  which 
completely  covers  the  costs  of  distillation. 

From  a  work-lead  containing  0*84  per  cent,  of  auriferous  silver  there  are  obtained 
{without  reference  to  losses  of  metals  on  Pattinsonising)  with  16  pans  : — 

Rich  lead     .........     41*0  per  cent. 

Commercial  lead 49-0        „ 

Lead  in  intermediate  products io'o        „ 

The  first  of  these  items  contains  2*0  per  cent,  of  gold  and  silver,  the  second  crooi 
And  the  third  o'2. 

Of  the  gold  and  silver  there  are  found  ! — 

96'6  per  cent,  in  the  rich  lead, 
o'  i        „         in  the  commercial  lead, 
2-3        „         in  the  intermediate  products. 

On  Pattinsonising  with  nine  pans,  and  treating  the  lead  on  the  Parke  process : — 

Rich  lead 38*9  per  cent,  with  2' 14  per  cent. 

Commercial  lead       .        .        .     52-5  „  o'ooi       „ 

Lead  in  intermediate  products.      8'6  „  o'i8        „ 

Of  the  gold  and  silver  there  occur : — 

99- 1  per  cent,  in  the  rich  lead, 
o'i        „         in  the  commercial  lead, 
o'8        „         in  the  intermediate  product. 

This  latter  procedure  is  therefore  more  remunerative  than  the  former. 

Desilvering  Work-Lead  by  Electricity. — The  electric  refining  of  silver  still  occasions 
difficulties.  It  is  a  hindrance  that  neither  lead  nor  silver  forms  firm,  sheet-like  deposits, 
but  mostly  dendritic  concretions.  Experiments  for  producing  soft  lead  electrolytically 
show  that  the  difference  of  price  between  the  two  qualities  does  not  at  present  open  a 
prospect  for  the  electric  process. 

Fine-burning  Silver. — Silver  as  directly  obtained  from  its  ores,  whether  by  amalga- 
mation, or  by  lead-work,  or  by  precipitation  from  its  solutions  by  means  of  metallic 
copper,  still  contains  several  per  cents,  of  other  metals.  The  process  on  the  refining 
hearth  is  never  continued  long  enough  for  the  complete  oxidation  of  all  other  metals,  and 
the  actual  quantity  left  in  the  sample  on  brightening  is  sometimes  as  much  as  9*5  per  cent. 
The  purification  of  silver  from  all  admixtures  of  other  metals  is  called  fine-burning.  If 
lead  is  present  or  forms  the  chief  ingredient  of  the  contaminating  matters  the  fine- 
burning  is  simply  a  prolonged  refining  conducted  not  on  the  large  hearth  of  the  refin- 


186  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

ing  furnace  but  in  a  smaller  space.  If  lead  does  not  preponderate  among  the  im- 
purities, the  silver  receives  an  addition  of  lead  before  the  oxidation  is  begun.  Small 
quantities  of  litharge  are  always  produced  in  the  process,  but  they  are  not  allowed  to 
run  off  from  the  surface  of  the  silver,  but  are  absorbed  by  the  mass  (bone-ashes,  marl) 
of  which  the  apparatus  used  in  fine-burning  is  composed.  We  distinguish  three  kinds 
of  fine-burning,  i.e.  (i)  in  capsules  or  iron  rings ;  (2)  in  the  muffle ;  (3)  in  the  reverbera- 
tory,  the  last  process  is  the  simplest  and  most  advantageous. 
The  production  of  gold  and  silver  in  the  world  in  1884  was  : 

Gold.  Silver. 

Kilos.  Kilos. 

Germany ."  555  ...  248,115 

United  States 46,343  ...  1,174,205 

Russia 32,829  ...  9,336 

Australia  . 42,960  ...  2,788 

Mexico 1,780  ...  655,868 

Austrian  Empire 1,658  ...  49,424 

Sweden  and  Norway         .        .        .        .  -19  ...  8,203 

Italy 109  ...  432 

Spain —  ...  3,562 

Turkey      .         .        ....        .  10  ...  2,164 

La  Plata, 118  ...  10,109 

Columbia .......  5,802  ...  18,286 

Bolivia 109  ...  384,985 

Chili          .        .        .    ^7^      .         .         .  245  ...  128,106 

Brazil        .        .         .      T-       .         .         .  952  ...  — 

Japan 256  ...  21,121 

Africa       .        .                 .        .        .        .  3,000 

Venezuela 5,022  ...  — 

Canada .  1,435  •••  1)641 

France —  ...  6,356 

Peru 179  ...  45,909 


143,381  ...  2,770,610 

According  to  Soetbeer  the  total  production  of  the  world  between  the  years  1493  and 
1875  was : 

Silver.  Gold.  Value  in 

Kilos.  Kilos.  million  shillings. 

Germany          .         .         .     7,904,910  ...  ...  1,422-9 

Austria    .        .                 .     7,770,135  ...  460,650  ...  2,683-8 

Rest  of  Europe        .         .     7,382,000  ...  ...  1,328-8 

Russia     ....     2,428,940  ...  1,033,655  ...  3,32i'i 

Africa      ....  ...  731,600  ...  2,041*2 

Mexico    ....  76,205,400  ...  265,040  ...  14,456-4 

New  Granada           .         .  ...  1,214,500  ...  3,388-5 

Peru        ....  31,222,000  ...  163,550  ...  6,076-3 

Bolivia    ....  37,717,600  ...  294,000  ...  7,609-4 

Chili        ....     2,609,000  ...  263,000  ...  1,205-1 

Brazil       ....  ...  1,037,050  ...  2,893-4 

United  States          .        .     5,271,500  ...  2,026,100  ...  6,601-7 

Australia         ...  ...  1,812,000  ...  5,055-4 

Otherwise        .         .         .     2,000,000  ...  151,000  ...  783-0 


180,511,485        ...     9,453,345        ...       58,857-0 

Of  this  total  value  silver  amounts  to  32,492  and  gold  to  26,375  million  (shillings). 
Chemically  pure  silver  is  obtained  by  dissolving  cupriferous  silver  in  nitric  acid, 
precipitating  the  silver  from  the  solution  by  means  of  sodium  chloride  or  hydrochloric  acid, 
and  reducing  the  silver  chloride  by  introducing  it  into  melting  potassium  carbonate  or 
igniting  it  with  resin  and  potash.  Silver  chloride  is  reduced  in  the  moist  way  by  bringing 
it  in  contact  with  zinc  and  dilute  hydrochloric  acid : — AgCl,  +  Zn  =  ZnCl2  +  Ag. 


SECT.  ii. J  SILVER.  187 

Gutzkow  prepares  fine  silver  by  placing  silver  sulphate  in  a  hot  solution  of  ferrous 
sulphate,  when  ferric  sulphate  and  metallic  silver  are  formed :  AgS04  +  2FeS04  = 
Fe2(S04)3  4  Ag,  which  is  washed,  dried,  and  smelted. 

Pure  silver  has  a  pure  white  colour  and  a  strong  lustre  which  is  much  heightened 
by  polishing.  It  is  softer  than  copper,  but  harder  than  gold.  It  is  extremely  ductile 
and  malleable,  in  which  respect  it  exceeds  all  other  metals  except  gold.  Yery  small 
admixtures  of  some  metals  decrease  its  ductility  and  malleability ;  the  presence  of 
copper,  however,  is  not  injurious,  and  that  of  gold  is  even  beneficial.  An  admixture  of 
lead,  antimony  and  selenium  is  very  pernicious.  If  melted  with  charcoal,  silver  loses  its 
flexibility,  but  it  may  be  melted  in  a  graphite  crucible  without  any  change  in  its  pro- 
perties. The  sp.  gr.  of  silver  is  10*5  ;  by  hammering  it  may  be  increased  to  ro'62. 
At  very  high  temperatures  silver  is  volatilised.  If  melted  with  access  of  air,  silver 
absorbs  oxygen,  which  as  the  metal  solidifies  escapes  often  with  a  noise  and  with  the 
projection  of  liquid  silver  (spitting,  or  spirting).  If  silver  contains  a  trace  of  lead  or 
i  per  cent,  of  copper  it  solidifies  quietly  with  a  concave  surface,  as  when  cold  it  occupies 
a  smaller  volume  than  when  melted.  It  is  not  attacked  by  weak  acids  but  dissolves  in 
nitric  acid  in  the  cold,  and  in  strong  sulphuric  acid  with  the  aid  of  heat. 

Silver  Alloys. — Silver  forms  alloys  with  lead,  zinc,  aluminium,  bismuth,  tin,  copper, 
gold,  and  other  metals,  of  which  that  with  lead  is  important  in  the  extraction  of  silver. 
The  most  useful  of  its  alloys  are  those  with  copper,  since  pure  silver  is  too  soft  and  is 
scarcely  ever  wrought  except  alloyed  with  copper.  The  alloys  are  harder  than  silver. 

The  German  silver  coins  contain  o'goo  of  fine  silver;  the  ore  of  the  Latin  monetary 
union  0^900  and  0*835,  those  of  Britain  o'c)2$. 

Silver  Assay. — In  order  to  ascertain  the  fineness  of  an  alloy,  presuming  that  it 
contains  nothing  but  silver  and  copper,  we  may  proceed  (i)  by  the  dry  way,  cupellation ; 
or  (2)  by  the  moist  way,  titration ;  or  (3)  by  the  hydrostatic  method. 

The  process  of  cupellation  requires  too  many  niceties  to  be  here  adequately  described. 
The  reader  is,  therefore,  referred  to :  Mitchell's  Manual  of  Practical  Assaying,  6th 
edition,  edited  by  W.  Crookes,  F.R.S.,  pp.  601-634.* 

The  assay  by  the  moist  way,  the  titration  method  of  Gay-Lussac,  is  more  easily 
executed  and  is  accurate  to  -$^Q  —  "5  per  cent.  Since  it  is  known  that  5*4274  grammes 
of  sodium  chloride  precipitate  exactly  i  gramme  of  silver  from  solution,  the  fineness  of  a 
dissolved  alloy  can  be  found  by  the  use  of  the  ordinary  apparatus  for  titration. 

Volhard  uses  for  precipitating  silver  from  an  acid  solution  mixed  with  a  little  ferric 
sulphate,  ammonium  sulphocyanide.  As  soon  as  all  the  silver  is  deposited  as  a  sulpho- 
cyanide,  the  red  colour  of  iron  sulphocyanide  appears.f 

For  cases  in  which  cupellation  and  titration  are  not  admissible  Karmarsch  recommends 
a  hydrostatic  assay  in  which  the  proportions  of  copper  and  silver  are  determined  by 
specific  gravity.  As  copper  and  silver  expand  when  alloyed,  but  alloys  become  the 
denser  the  more  they  are  exposed  to  mechanical  pressure,  there  is  here  an  uncertainty  in 
the  very  basis  of  the  hydrostatic  silver  assay  which  renders  it  inapplicable  for  silver 
which  has  been  cast  and  subsequently  worked,  but  only  for  silver  coins. 

Silvering. — Silver-plating,  or  the  coating  of  other  metals  with  silver,  can  be  effected 
(i)  by  plating  ;  (2)  by  fire  (fire-silvering) ;  (3)  in  the  cold  way  ;  (4)  in  the  wet  way,  and 
(5)  galvanically.  In  order  to  cover  sheet-copper  with  a  layer  of  silver  the  surface  of 
the  copper  is  carefully  cleaned  and  moistened  with  a  solution  of  silver  nitrate,  which 
produces  a  thin  film  of  silver.  Upon  this  film  there  is  laid  a  plate  of  silver ;  both  are 
heated  and  extended  between  rollers.  Copper  wire  may  be  silvered  by  simply  laying 
sheet  silver  upon  it  and  passing  it,  hot,  through  grooved  rollers. 

Silvering  in  the  fire  is  effected  by  means  of  a  silver-amalgam  or  a  mixture  of  i  part 

*  See  also  Select  Methods  in  Chemical  Analysis,  by  W.  Crookes,  F.E.S.,  p.  359. 

t  See  also  Mitchell  s  work  above  quoted,  pp.  634 — 685 ;  and  Select  Methods,  p.  286. 


i88  CHEMICAL  TECHNOLOGY.  [SECT.  11. 

precipitated  silver,  4  parts  sal-ammoniac,  4  parts  sodium  chloride,  and  ^  part  of  mercuric 
chloride,  which  is  rubbed  upon  the  surface  of  the  metal  previously  well  cleaned.  The 
mercury  is  then  expelled  from  the  coating  of  amalgam  by  ignition.  For  silvering  but- 
tons there  is  used  a  paste  of  48  parts  sodium  chloride,  48  parts  zinc  sulphate,  i  part 
mercuric  chloride,  and  2  parts  silver  chloride. 

For  silvering  in  the  cold  the  cleaned  surface  of  the  metal  to  be  silvered  is 
rubbed  by  means  of  a  cork  with  a  mixture  of  equal  parts  silver  chloride  and  sodium 
chloride,  |  parts  chalk,  and  2  parts  potash  moistened  with  water,  until  the  colour  of  silver 
is  produced  as  desired.  According  to  W.  Stein  i  part  silver  nitrate  and  3  parts  potas- 
sium cyanide  are  rubbed  together  with  water  enough  to  form  a  thick  paste,  which  is 
quickly  and  uniformly  rubbed  on  with  woollen  rags.  To  silver  iron  it  must  first  be 
coated  with  a  layer  of  copper. 

In  silvering  in  the  wet  way  the  metal  to  be  coated  is  placed  in  a  boiling  solution  of 
equal  parts  of  tartar  and  common  salt  with  ^  silver  chloride  until  the  silvering  is  sufficient. 

For  galvanic  silvering  (electro-plating),  recently  precipitated  and  well-washed 
silver  chloride  is  introduced  into  a  solution  of  potassium  cyanide  (100  grammes  cyanide 
to  one  litre  water),  as  long  as  it  is  taken  up,  and  to  this  solution  is  added  an  equal 
measure  of  solution  of  potassium  cyanide.*  Galvanic  silvering  is  applicable  upon 
copper,  bell-metal,  brass,  pinchbeck,  cast-  and  bar-iron.  Tin,  zinc,  and  polished  steel 
must  be  previously  coated  with  copper,  if  the  silver  is  to  be  permanent.  Articles  made 
of  German  silver,  and  Britannia  metal,  and  electro-plated,  known  under  the  names 
of  "  Alfenide  "  or  China  silver,  occur  in  commerce,  and  have  been  already  mentioned. 
Upon  one  square  metre  of  metallic  surface  there  are  deposited  from  i  to  22,  and  even 
240,  grammes  silver,  so  that  the  thickness  of  the  stratum  of  silver  varies  from  -5^5-5- 
to  y^,  and  even  -£%,  of  a  millimetre.  Galvano-plated  articles  sometimes  further 
receive  a  slight  coating  of  palladium  to  preserve  them  from  being  blackened  by  the 
action  of  hydrogen  sulphide. 

The  black  colouring  of  silver  articles,  sometimes  in  vogue,  and  called  the  oxidation 
of  silver  is  produced  either  by  sulphur  or  by  chlorine.  The  former  agent  gives  a  blue- 
black  tone,  and  the  latter  a  brownish  black.  To  obtain  the  sulphur  colour  the  articles 
are  immersed  in  a  solution  of  potassium  sulphide.  For  the  chlorine  colour  the  silver 
must  be  immersed  in  a  solution  of  copper  sulphate  and  sal-ammoniac. 

GOLD. 

Occurrence. — Almost  exclusively  metallic,  either  in  situ,  in  quartz  rock,  especially 
along  with  quartz,  pyrites,  and  hydroferrite  ;  also  as  gold-sand,  in  dust  or  grains, 
leaflets,  and  rounded  pieces  (nuggets),  in  the  sands  of  rivers  or  in  alluvial  soils,  consist- 
ing chiefly  of  clay  and  quartz-sand  along  with  mica,  water-worn  fragments  of  syenite, 
chloritic  slate,  grains  of  chrome  iron  and  magnetic  iron,  spinel,  garnet,  &c.  In  the 
metallic  state  it  always  contains  more  or  less  silver,  as  electrum.  According  to  recent 
analyses,  native  gold  contains  : 

Transylvania.    S.  America.  Siberia.         California.  Australia. 

Gold          ....     6477     ...     88-04     ...  86-50  ...     90-60     ...  99-2    and  957 

Silver        ....     35-23     ...     11-96     ...  13-20  ...     10-06    ...  0-43    „       3-8 

Iron  and  other  metals       .        —       ,..       —       ...       0-30  ..        0^34     ...  0-28    „        O'2 

Gold  is  also  often  met  with  in  native  tellurium  and  silver  telluride,  sometimes  in 
argyrythrose  and  proustite,  in  iron  pyrites,  copper  pyrites,  in  stibine,  in  blende,  in 
arsenical  pyrites  (e.g.,  that  of  Keichenstein  in  Silesia)  and  galena.  The  chief  supplies 

*  The  most  useful  form  of  battery  for  depositing  silver  is  a  modification  of  the  Wollaston 
battery.  For  the  details  of  the  process,  and  for  methods  of  producing  dead  or  bright  surfaces  at 
pleasure,  the  reader  may  consult  Electro-deposition  of  Metals,  by  A.  Watt  (Crosby  Lockwood  &  Co.). 


SECT,  ii.]  GOLD.  189 

of  gold  are  obtained  from  the  Ural,  the  United  States  (California,  Nevada,  Arizona, 
Montana,  Utah,  and  Colorado),  from  British  Columbia,  Nova  Scotia,  Mexico,  Peru,  and 
Brazil,  from  Australia  (especially  Victoria,  New  South  Wales,  and  Queensland), 
Tasmania,  New  Zealand,  and  in  Africa  (Natal,  the  Transvaal,  &c.).  The  Ural  Moun- 
tains and  Siberia  also  yield  much  gold. 

The  gold  deposits  of  India  (the  Wynaad  and  elsewhere)  must  in  earlier  ages  have 
yielded  a  large  part  of  the  treasures  of  Eastern  kings,  but  in  modern  times  their  working 
has  not  proved  very  remunerative.  In  the  British  Islands  gold  was  formerly  obtained  in 
considerable  quantity.  The  placer  mines  of  Croghan  Kinshela,  in  county  Wicklow,  were 
worked  about  the  beginning  of  the  present  century.  In  1795,  a  large  nugget,  weigh- 
ing 2\\  oz.,  was  picked  up  at  the  ford  of  Ballinasilloge,  in  a  stream  since  known  as  the 
Gold  Mines  River.  The  Government  placers  yielded  944  oz.  of  gold,  whilst  over 
;£i  0,000  were  paid  for  gold  sold  by  private  individuals.  Geological  authorities  con- 
sider it  probable  that  vast  quantities  of  auriferous  sands  still  exist  untouched  under 
the  deep  river  accumulations  in  the  valley  of  the  Ovoca.*  The  South  of  Scotland  at 
one  time  produced  gold,  e.g.)  the  head  waters  of  the  Clyde,  Tweed,  and  Annan.  The 
specimens  lately  obtained  have  served  merely  as  curiosities.  In  Sutherland  gold- 
seeking  was  commenced  in  the  years  1867  and  1868,  and  a  certain  amount  of  the 
precious  metal  was  found,  but  as  all  the  works  have  been  abandoned,  the  operations 
cannot  have  proved  remunerative.  In  North  Wales,  especially  Merionethshire,  the 
result  is  of  greater  importance.  A  Welsh  mine  owner  is  known  to  have  lent  Charles  I. 
^500,000  in  Welsh  gold  at  the  beginning  of  the  Civil  War.  Latterly  and  at  present 
mining  is  carried  on  in  the  Cefn  Coch  and  Gwynfynydd  mines.  Some  6f  the  lode- 
stuff  raised  gives  87  oz.  per  ton,  but  owing  to  the  sulphuretted  character  of  the  mineral 
no  known  method  of  working  has  proved  fully  successful.t 

In  the  earlier  days  of  all  auriferous  districts,  gold  was  obtained  in  dust, 
grains,  scales,  and  nuggets,  derived  from  the  weathering  of  gold-bearing  rocks  and 
found  in  shallow  diggings  in  alluvial  soils  (placers),  or  procured  by  washing  the  sands 
of  river-beds  or  the  deposits  of  floods.  If  such  matter  is  dexterously  washed  and 
shaken,  the  gold  grains  sink  to  the  bottom  on  account  of  their  superior  gravity. 
The  more  minute  particles  are,  however,  in  such  cases  lost. 

When  water  is  plentiful  the  gold  alluvium  is  washed  by  means  of  strong  currents, 
which  wash  the  mud,  sand,  and  shingle  into  large  sluices,  in  which  the  particles  of 
gold  sink  to  the  bottom.  This  method  involves,  however,  greater  losses  than  washing 
by  hand  or  by  machinery.  In  any  case  when  the  placer  diggings  and  the  washings  in 
a  district  are  exhausted,  the  next  method  is  grinding  up  the  gold-quartz  in  specially 
constructed  mills.  As  it  exists  in  particles  often  finer  than  flour,  it  has  to  be 
extracted  from  the  mass  by  means  of  mercury,  either  incorporated  with  the  ground 
ore,  or  presented  in  the  form  of  amalgamated  copper  plates,  which  are  fixed  obliquely 
in  the  long  troughs  in  which  the  ore  is  ground  up  with  water.  From  time  to  time 
these  plates  are  lifted  out  and  scraped,  and  returned  to  the  troughs  after  being  re- 
amalgamated. 

There  is,  however,  a  distinction  to  be  made  in  the  character  of  gold-bearing  quartz. 
In  some  kinds — the  "  free-milling  "  sorts — the  gold  is  easily,  and,  if  the  mechanical 
arrangements  have  been  properly  constructed,  completely  taken  up  from  the  ground 
mineral.  Such  free-milling  quartz  generally  lies  near  the  surface,  where  the  rocks  are 
permeated  by  atmospheric  air  and  water,  and  where  consequently,  in  the  lapse  of  ages, 
the  base  metals  and  their  compounds  have  been  oxidised,  decomposed,  and  washed 
away,  leaving  the  gold  free.  As  the  miner  penetrates  deeper  he  comes  upon  minerals 

*  See  Kinahan,  Quarterly  Journal  of  /Science,  April  1878,  N.  S.,  vol.  viii.  p.  289. 
t  For  details  the  reader  is  referred  to  a  paper  on  "British Gold, "by  K.  Hunt,  F.R.S.,  Quarterly 
Journal  of  Science,  1865. 


1 90  CHEMICAL   TECHNOLOGY.  [SECT.  n. 

situate  below  the  permanent  water-line.*  Here  the  gold  cannot  be  readily  extracted 
by  the  amalgamation  process,  as  it  exists,  if  not  combined,  at  least  entangled  among 
blende,  arsenical  pyrites,  galena,  and  antimony  ores,  so  that  it  to  a  great  extent 
escapes  the  action  of  the  mercury.  Hence  the  gold  actually  extracted  from  a  mineral 
in  practical  working  falls  sadly  short  of  the  quantity  found  on  assaying.  Yery  small 
quantities  of  lead,  copper,  arsenic,  or  antimony  quickly  spoil  the  mercury,  and  render 
it  unable  to  take  up  the  gold.  Among  the  most  successful  expedients  for  combatting 
this  evil,  ranks  the  use  instead  of  pure  mercury  of  sodium-amalgam  as  invented  by 
W.  Crookes,  F.R.S. 

The  presence  of  sodium  keeps  the  mercury  bright  and  active.  This  compound  is 
prepared  in  three  modifications  A,  B,  and  C.  Amalgam  A  is  a  combination  of 
3  parts  sodium  with  97  of  mercury.  The  mixture  is  prepared  as  follows  : — A  strong 
iron  flask  with  a  narrow  neck  is  bedded  nearly  up  to  the  mouth  in  a  sand-bath  at 
198° ;  the  materials  are  weighed  out,  the  mercury  is  poured  into  the  flask,  and  the 
sodium  is  dropped  in,  taking  pieces  of  the  size  of  a  pea  each  time,  and  using  an  iron 
forceps.  The  action  should  be  allowed  to  cease  each  time  before  a  fresh  portion  is  added, 
When  the  whole  of  the  sodium  has  been  introduced,  the  amalgam  is  poured,  whilst 
still  liquid,  into  a  flat  iron  dish,  and  when  cold  is  broken  up  and  kept  in  a  stoppered 
jar.  Amalgams  B  and  C  contain  an  addition  of  zinc,  and  are  recommended  for  use. 

Both  from  experiments  and  from  practical  working,!  it  appears  that  when  sodium- 
amalgam  is  used  according  to  the  instructions  of  the  inventor,  and  is  not  expected  to 
dispense  with  all  judgment  on  the  part  of  the  operator,  it  greatly  facilitates  the  amalga- 
mation of  gold,  which,  it  must  be  remembered,  is  not  so  easily  taken  up  by  mercury 
as  it  is  commonly  believed. 

Mr.  W.  Skey,  analyst  to  the  Geological  Survey  of  New  Zealand, J  finds  that 
numerous  samples  of  bright,  clear-looking  gold,  of  all  degrees  of  fineness,  refuse  to 
amalgamate  on  any  part  of  their  natural  surfaces  though  taken  direct  from  the 
reef  and  untouched  by  hand ;  that  on  such  surface  sulphur  is  always  present ; 
that  native  gold  or  gold  in  a  pure  state  readily  takes  up  sulphur  from  moist 
sulphuretted  hydrogen  or  ammonium  sulphide  and  absorbs  it  directly  when  ad- 
ministered in  boiling  water ;  that  surfaces  so  treated  refuse  to  amalgamate,  though  no 
apparent  change  can  be  observed  ;  geld  so  affected  is  rendered  amalgamable  by  roasting 
in  an  open  fire,  except  copper  is  present  to  the  extent  of  7  per  cent,  or  perhaps  less,  whilst 
the  same  effect  is  produced  by  contact  with  potassium  cyanide,  chromic  and  nitric  acids, 
and  chloride  of  lime  acidified.  The  author  is  of  opinion  that  this  absorption  is  of  a 
chemical  character.  He  has  observed  that  iron  sulphates  in  presence  of  air  and  water 
decompose  various  metallic  sulphides  common  in  gold  reefs,  liberating  sulphuretted 
hydrogen.  He  has  also  proved  that  the  action  of  sulphuretted  hydrogen  renders  gold 
non-amalgamable,  and  he  suggests  that  much  of  the  loss  in  extracting  gold  from  auriferous 
minerals  of  amalgamation  depends  on  the  presence  of  a  thin  film  of  sulphurised  gold 
which  envelops  the  particles. 

An  immense  quantity  of  gold  is  lost  by  being  carried  away  in  the  form  of  tailings 
too  fine  to  be  deposited  in  any  practicable  time.  It  is  estimated  that  though  the  State 
of  California  since  '1848  has  produced  gold  to  the  value  of  ^250,000,000,  yet 
more  "  has  been  wasted  in  milling  and  hydraulic  mining  by  being  washed  down  the 
rivers  and  even  to  the  ocean."  An  experienced  Californian  expert,  quoted  by  Eissler, 
states  that  in  his  experiments  "  gold  has  been  taken  up  in  distilled  water  so  fine  that  it 
could  not  precipitate  in  less  than  from  five  to  ten  minutes."  Gold  of  this  character 
obviously  cannot  be  saved  in  running  streams. 

*  See  Eissler's  Metallurgy  of  Gold,  Crosby  Lockwood  &  Co. 

t  See  Ure's  Dictionary  of  Arts,  Manufactures,  and  Mines,  Longmans,  vol.  ii.  p.  697. 

£  Chemical  News,  vol.  xxii.  Dec.  9,  1870,  p.  282. 


SECT,  ii.]  GOLD.  191 

Great  care  must  be  observed  in  the  "  milling  "  process.  If  the  ore  is  too  coarse,  a 
proportion  of  the  gold  is  certainly  wasted,  as  many  of  the  particles  remain  incrusted 
•with  silica,  and  never  come  into  actual  contact  with  the  mercury  at  all.  On  the 
other  hand,  if  the  ore  is  crushed  too  fine,  much  of  the  gold  will  float  instead  of  amal- 
gamating, and  is  not  arrested  either  by  the  amalgamated  copper  or  silver  plates,  or  by 
the  "  blankets  "  suspended  in  the  sluices.  The  pulp  is  generally  caused  to  flow  over 
three  sets  of  blankets.  The  first  set  are  washed  every  twenty  minutes,  and  the  second 
every  two  hours. 

A  so-called  hydrogen  amalgamation  process — perhaps  more  correctly  styled  an 
electric  process — has  been  patented  by  Molloy,  and  is  being  worked  in  America  by  the 
Hydrogen- Amalgam  Company.  The  apparatus  used  consists  of  a  shallow  pan,  i  inch 
in  depth  and  41^  inches  in  diameter,  containing  mercury  to  the  depth  of  half-an- 
inch.  In  the  centre  of  this  pan  is  a  porous  jar,  so  fixed  that  the  mercury  cannot  enter 
or  displace  it.  Within  the  jar  is  a  cylinder  of  lead  and  a  solution  of  sodium  sulphate. 
This  lead  cylinder  forms  the  anode,  and  is  coupled  with  the  positive  pole  of  a  small 
dynamo,  whilst  the  mercury  is  connected  with  the  negative  pole  of  the  same  machine. 
As  the  current  passes,  hydrogen  is  evolved  from  the  surface  of  the  mercury,  which 
combines  with  a  portion  of  it,  forming  a  hydrogen-amalgam.  According  to  the 
statements  of  the  Hydrogen-Amalgam  Company,  quoted  by  Eissler,  this  process 
prevents  the  mercury  from  turning  "  sick  "  (losing  its  activity),  and  eflects  an  increased 
yield  of  gold  amounting  to  10  per  cent,  at  the  expense  of  only  threepence  per  ton  for 
electrical  and  mechanical  force  and  labour. 

To  obviate  the  waste  of  gold  and  mercury  and  the  losses  involved  in  the  ordinary 
processes,  Mr.  W.  Pritchard  Morgan,  M.P.,  and  Mr.  J.  Needham  Longden  of 
Sydney,  have  invented  and  patented  a  dry  amalgamation  process,  in  which  water 
is  entirely  dispensed  with.  This  is  in  itself  no  small  advantage  in  many  parts  of 
Australia  and  Africa.  The  ore  is  first  comminuted,  not  by  grinding  or  stamping,  but 
by  the  "  Jordan  "  pulveriser,  which  acts  nearly  in  the  manner  of  a  Carr  disintegrator, 
and  reduces  the  mineral  to  a  powder,  passing  it  through  a  sieve  of  8100  meshes  to 
the  square  inch,  or  forty  times  as  fine  as  is  commonly  done.  This,  in  a  wet  process 
would  be  fatal,  as  it  would  allow  much  of  the  gold  to  float,  but  where  water  is  not 
present  it  is  an  advantage,  as  it  secures  the  contact  of  the  gold  with  the  mercury. 
The  mercury  is  applied  dry  and  hot  by  means  of  a  self-acting  apparatus  which  ensures 
perfect  contact  but  which  cannot  be  described  intelligibly  without  the  aid  of  a  working 
model.  As  the  process  is  completed  the  ground  ore  is  forced  into  the  concentrating 
chamber.  Messrs.  Jordan,  Son  &  Comman,  of  Gracechurch  Street,  erected  plant  for 
the  process  at  Stratford  Market,  and  found  a  considerably  increased  yield  of  gold  with 
a  decrease  of  the  working  cost.  It  is  needless  to  say  that  this  process  can  be  worked 
with  sodium  amalgam,  which,  in  the  presence  of  antimony,  would  be  found  advan- 
tageous.* 

The  following  method  of  treating  refractory  gold  ores,  sulphides,  tellurides,  arsenio- 
sulphides,  &c.,  containing  zinc,  copper,  iron,  bismuth,  and  antimony  has  been  devised 
by  W.  Crookes,  F.E.S.  The  object  sought  is  to  prevent  the  flouring  and  sickening  of 
the  mercury  and  the  tarnishing  of  the  gold  grains,  which  together  involve  a  loss  of 
from  20  to  80  per  cent,  of  the  gold  present  as  found  on  assay.  Various  methods  for 
preventing  these  evils  have  been  suggested,  but  none  of  them  have  proved  satisfactory. 
Mr.  Crookes  submits  the  ores,  tailings,  sulphides,  etc.,  to  the  joint  action  of  a  solution 
of  mercury  cyanide,  or  of  some  other  soluble  salt  of  mercury,  and  of  an  alternating 
electric  current.  The  ore  in  question  is  reduced  to  a  powder  in  the  usual  manner, 
mixed  with  a  solution  of  sulphate,  nitrate,  chloride,  or  cyanide  of  mercury,  and  a 
rapidly  alternating  current  of  electricity  is  then  passed  through  the  mass  either  when 

*  For  further  particulars,  the  reader  is  referred  to  the  Journal  of  Science,  Third  Series,  vol.  vi. 
(1884)  P-  4i6. 


i92  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

at  rest  or  when  kept  in  a  state  of  agitation.  The  bulk  of  the  mass  is  not  a  very  good 
conductor  of  electricity,  whilst  the  fine  particles  of  gold  disseminated  through  the  mass 
are  excellent  conductors.  The  poles  may  be  made  of  iron  or  carbon,  each  being 
alternately  anode  or  kathode.  Each  alternation  of  the  current  causes  mercury  to  be 
precipitated  on  alternate  surfaces  of  the  particles  of  gold  in  the  mass  of  ore,  without  re- 
quiring the  gold  to  be  in  metallic  communication  with  either  pole.  The  sizes  of  the 
particles  are  not  material,  as  the  finest  "  flour  "  and  "  float  "  gold  will  be  amalgamated 
and  thus  weighted  as  well  as  the  largest  pieces. 

An  advantage  incidental  to  the  use  of  an  alternating  current  is  that  the  sudden 
and  the  violent  decompositions  and  recompositions  alternating  with  great  rapidity 
cause  the  mass  to  become  warm,  thus  greatly  facilitating  the  decomposition.  The  efficient 
action  of  the  alternating  current  depends  on  the  right  adjustment  of  several  variable 
factors,  e.g.  (i)  current  density;  (2)  area  of  electrodes;  (3)  rate  of  alternations  per  second  ; 
(4)  electric  conductivity  of  the  wet  mixture  of  crushed  ore  and  liquid.  As  this  last 
factor  varies  with  every  kind  of  ore  the  others  will  have  to  be  ad  justed  in  each  separate 
case  to  get  the  maximum  effect.  Hence  no  general  directions  can  be  given. 

If  it  is  impracticable  to  use  an  electric  current  the  inventor  employs  a  solution 
of  mercury  cyanide  or  sulphate,  either  of  which  will  superficially  amalgamate  the 
particles  of  gold,  though  less  rapidly  than  with  the  aid  of  the  alternating  current.  The 
reaction  may  be  hastened  somewhat  by  heating  the  mass. 

When  carrying  out  the  process  in  this  manner  the  inventor  uses  a  solution  of 
2  or  3lbs.  of  mercury  cyanide  or  sulphate,  dissolved  in  80  to  100  gallons  of  water. 

In  some  cases  he  finds  it  advantageous  to  add  to  the  mercury  used  in  the  subsequent 
amalgamation  process  a  little  sodium  amalgam  as  described  in  his  specification  No.  391  of 
1865  or  some  of  the  modified  amalgams  described  in  his  specification  No.  2229  of  1865. 

The  points  here  claimed  are  the  improvements  in  amalgamating  and  extracting  gold, 
which  consist  in  submitting  the  ore  to  the  joint  action  of  a  solution  of  mercurial  salt 
and  an  alternating  electric  current.  Further,  the  improvement  in  amalgamating  and 
extracting  gold,  which  consists  in  submitting  the  ore  to  the  action  of  a  solution  of 
mercury  cyanide  or  sulphate,  and  lastly  the  improvement  in  the  final  amalgamating 
process  by  using  a  solution  of  cyanide  or  sulphate  of  mercury,  or  an  alternating  electric 
current,  in  conjunction  with  a  solution  of  a  mercurial  salt. 

The  extraction  of  gold  from  gold-sands  may  be  effected  completely  by  fusion.  The 
sand  is  smelted  with  iron  ore  in  blast  furnaces  with  suitable  fluxes,  thus  yielding  auri- 
ferous raw  iron,  from  which  the  gold  is  subsequently  extracted  by  means  of  sulphuric 
acid.  If  gold  is  present  in  copper  or  lead  ores  they  are  roasted  and  washed.  Auri- 
ferous sulphides  are  sometimes  roasted  and  smelted.  The  raw  stone  or  matte  thus 
obtained  is  again  roasted,  melted  afterwards  along  with  litharge,  which  takes  up  the 
gold  present  in  the  matte,  and  is  separated  on  the  refining  hearth.* 

Plattner  devised  a  process  for  extricating  gold  from  its  minerals  by  means  of 
chlorine  ;  it  has  been  improved  by  Deetkin,  Kustel,  Bruckner,  Hears,  and  others. 
The  process  of  chlorination  consists,  generally  speaking,  of  the  following  operations  : — 

(i)  The  comminuted  auriferous  matter  is  perfectly  oxidised,  moistened  with  water, 
and  sifted  into  a  wooden  vat,  coated  with  tar  or  resin  and  having  a  perforated  false 
bottom.  It  is  then  covered  with  a  lid,  which  must  fit  well.  Chlorine  is  liberated 
below  the  false  bottom,  whether  from  a  mixture  of  salt,  pyrolusite,  and  sulphuric  acid, 
or  from  chloride  of  lime  in  contact  with  an  acid,  and  allowed  to  penetrate  the  mass  of 
we  from  below.  When  the  chlorine  has  pervaded  the  entire  mass,  the  vat  is  closed  at 
the  top,  and  allowed  to  stand  for  a  few  hours  covered  up.  The  lid  is  then  removed 
and  water  is  added  so  as  to  fill  it  up  on  a  level  with  the  top  of  the  ore.  It  is  found  that 

*  This  process  has  not  come  into  general  use  in  America  or  Australia. 


SECT.  ii.J  GOLD.  193 

the  gold  has  been  converted  into  a  soluble  terchloride,  which  is  dissolved  out  with 
water.  Lastly,  a  solution  of  ferrous  sulphate  is  added  to  the  clear  liquid,  when  the 
gold  is  thrown  down  as  a  black  or  brown  precipitate,  which  is  collected,  washed,  and 
melted  down. 

As  a  condition  for  success,  sulphuretted  ores  must  be  carefully  roasted  before 
chlorination,  as  must  also  be  all  minerals  containing  lead,  beginning  at  a  very  low 
temperature.  Sulphates,  if  present,  must  be  destroyed  by  roasting.  No  hydrochloric 
acid  gas  must  accompany  the  chlorine  :  hence  in  many  cases  it  is  advisable  to  generate 
chlorine  in  a  separate  vessel,  so  that  it  may  be  washed  in  pure  water  before  it  is  intro- 
duced below  the  false  bottom. 

In  the  modification  of  the  chlorine  process  devised  by  M.  Their  the  chlorinator  is  an 
iron  barrel  lined  with  lead,  with  a  man-hole  at  one  side  for  filling  and  emptying.  A 
ton  of  ore  is  introduced  at  a  time,  the  barrel  is  partially  filled  with  water  ;  about  20  Ibs. 
of  chloride  of  lime  are  introduced,  followed  by  the  roasted  ore,  and  the  proper  quantity 
of  sulphuric  acid — about  25  Ibs.  The  man-hole  is  tightly  closed,  and  the  barrel  is 
caused  to  revolve  until  the  gold  is  dissolved,  which  is  generally  effected  in  six  hours. 
The  contents  of  the  barrel  are  then  rinsed  out  upon  a  filter. 

For  a  full  account  of  the  various  modifications  of  the  chlorination  process,  of  the 
precautions  required,  and  the  utilisation  of  silver  and  other  matter  present,  see  Eissler's 
work  above-mentioned  (chapters  vi.  and  vii.). 

The  gold,  as  obtained  by  whatever  process,  contains  small  admixtures  of  other 
metals,  always  including  silver.  The  gold  may  be  separated — (i)  By  antimony 
sulphide  ;  (2)  by  sulphur  and  litharge  ;  (3)  by  chlorine  ;  (4)  by  the  quartation  process  ; 
and  (5)  by  sulphuric  acid. 

In  the  process  of  parting  by  antimony  sulphide,  the  alloy  of  gold  (containing  at 
least  60  per  cent,  of  gold)  is  melted  in  a  graphite  crucible,  and  pulverised  antimony 
sulphide  is  then  introduced.  The  melted  mass  is  poured  into  an  iron  mould.  When 
cold,  the  mass  is  found  separated  into  two  layers,  the  upper,  or  plagma,  consisting 
of  silver,  copper,  and  antimony  sulphides ;  and  the  lower,  being  the  regulus  (gold  anti- 
monide).  The  latter  is  then  roasted,  and  the  residue  of  gold  is  melted  with  borax, 
saltpetre,  and  powdered  glass. 

The  operation  with  sulphur  is  a  concentration,  preparatory  for  separation  in  the 
wet  way,  especially  for  quartation,  the  object  being  only  to  economise  nitric  acid.  The 
granulated  alloy  of  gold  is  put  in  an  ignited  graphite  crucible,  along  with  one-seventh  part 
of  powdered  sulphur,  and  covered  with  powdered  charcoal.  It  is  kept  first  for  two  to  two 
and  a  half  hours  at  a  low  red-heat,  and  is  then  heated  to  fusion.  If  the  alloy  contained 
considerable  proportions  of  gold,  there  is  separated  out  a  silver  rich  in  gold,  whilst  but 
little  gold  remains  in  the  plagma.  If  the  alloy  was  poor  in  gold,  such  a  separation 
takes  place  very  imperfectly,  or  not  at  all.  To  effect  this,  litharge  is  sprinkled  upon 
the  melted  mass ;  its  oxygen  converts  a  part  of  the  sulphur  into  sulphurous  acid, 
whilst  the  liberated  silver  is  eliminated  along  with  the  greater  part  of  the  gold. 

For  separating  gold  by  means  of  chlorine  the  auriferous  alloy,  in  fine  grains  or  in 
thin  sheets,  is  stratified  in  a  crucible,  with  so-called  cement  powder  (consisting  of 
4  parts  ground  bricks,  i  part  common  salt,  and  i  part  ignited  iron  sulphate),  and 
exposed  for  several  hours  to  a  gradually  increasing  heat.  By  the  action  of  the  ferrous 
sulphate  upon  the  salt,  chlorine  is  liberated,  which  converts  the  silver  into  chloride, 
but  does  not  attack  the  gold.  The  silver  chloride  is  absorbed  by  the  ground  bricks. 
When  cold,  the  mass  is  boiled  in  water  to  recover  the  gold.  In  1869  Miller  founded 
upon  the  property  of  chlorine  not  to  attack  gold  at  elevated  temperatures  a  new 
process  for  purifying  gold,  which  has  been  successfully  introduced  at  the  Mints  of 
London,  Sydney,  and  Philadelphia.  Chlorine  gas  is  introduced  into  the  melted  metal 
through  a  stoneware  pipe,  and  combines  with  the  silver  to  form  silver  chloride,  which 


i94  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

vises  to  the  surface  of  the  melted  gold ;  the  gold  remains  perfectly  desilvered. 
Instead  of  chlorine  gas,  bromine  may  be  used. 

Separation  in  the  wet  way,  or  quartation,  derives  its  name  from  the  traditional 
assumption  that  in  order  to  separate  gold  from  silver  in  this  manner  the  latter  metal 
must  amount  to  three  times  the  quantity  of  the  latter.  Pettenkof  er  has  shown  that  two 
parts  of  silver  are  sufficient  if  the  acid  is  sufficiently  strong,  and  the  boiling  is  duly 
prolonged.  For  this  purpose  the  alloy  is  melted  xip  with  the  needful  quantity  of  silver, 
the  mixed  metal  is  granulated  and  covered  in  a  platinum  pan  with  nitric  acid  of 
sp.  gr.  i '320,  perfectly  free  from  chlorine.  Silver  is  dissolved,  whilst  the  gold  remains, 
and  is  melted  in  a  crucible  with  borax  and  saltpetre.  The  silver  is  thrown  down  from 
the  solution  by  means  of  copper  or  zinc. 

The  separation  of  gold  by  means  of  sulphuric  acid  is  preferable  to  quartation,  on 
account  of  its  simplicity  and  cheapness.  The  separation  is  effected  most  readily  if  the 
alloy  contains  in  16  parts  not  much  above  4  and  not  much  less  than  3  parts  of  gold. 
The  sulphuric  acid  used  in  the  process  must  have  the  sp.  gr.  i-848.  The  alloy  is 
placed  in  a  suitable  pan,  and  covered  with  sulphuric  acid  and  heated.  In  twelve  hours 
the  silver  and  the  copper  are  completely  dissolved  : — 

AuAg2  +  2H2S04  =  Au  +  Ag2S04  +  S02  +  2H20. 

When  all  the  silver  and  copper  are  converted  into  sulphates,  the  solution  is  poured 
into  a  leaden  pan,  and  the  silver  sulphate,  which  congeals  to  a  crystalline  paste,  is 
taken  out  with  an  iron  shovel  and  put  in  lead  pans  filled  with  hot  water.  The 
precipitation  of  the  sulphate  is  effected  with  slips  of  sheet-copper.  The  solution  of 
copper  sulphate  is  neutralised  as  completely  as  possible  with  copper  oxide,  and  worked 
up  as  copper  sulphate.  The  gold  which  remains  undissolved  is  freed  from  accompanying 
ferric  oxide,  copper  sulphide,  and  lea*d  sulphate,  by  boiling  with  sodium  carbonate 
and  treatment  with  nitric  acid,  dried,  and  remelted  with  a  little  saltpetre.  This 
method  of  separation  has  rendered  it  possible  to  refine  to  advantage  old  cupriferous 
silver  containing  •£§  or  -^  per  cent,  of  gold,  as  is  often  the  case  in  old  silver  coins. 

According  to  Gutzkow's  proposal,  there  are  worked  up :  gold  ingots  from  California, 
set  at  2  parts  gold  and  3  parts  silver  and  then  granulated ;  silver  ingots  from  the 
Comstock  mine,  containing  2  to  10  per  cent,  of  gold,  which  are  dissolved  up  at  once 
without  granulating ;  and,  finally,  silver  in  the  form  of  bricks  containing  a  considerable 
proportion  of  copper  from  the  amalgamation  of  the  tailings,  and  from  the  mines  of 
Nevada.  These  bricks  are  smelted  with  so  much  fine  silver  that  the  proportion  of 
copper  is  reduced  to  8  per  cent. 

There  is  used  for  dissolving  the  alloys  a  cast-iron  pan,  66  centimetres  in  width  and  45 
centimetres  in  depth,  made  more  capable  of  resisting  acids  by  containing  2  to  4  per  cent, 
of  phosphorus.  It  takes  a  charge  of  100  to  150  kilos.,  which  is  introduced  through 
an  opening  in  the  dome  capable  of  being  closed  with  a  slide.  The  gases  and  vapours 
given  off  during  dissolving  are  passed  through  a  leaden  pipe  into  a  chamber  lined  with 
lead  plates,  and  from  here  through  a  tower  into  a  lofty  chimney.  The  sulphuric  acid 
put  in  at  1 68°  Tw.,  is  heated  to  a  boil,  and  the  alloy  is  added.  The  hot  solution,  floating 
above  the  undissolved  gold  is  syphoned  off  into  a  deep  iron  receiver,  through  an  iron 
pipe  into  sulphuric  acid  at  the  heat  of  110°,  and  of  the  strength  of  i23°Tw.  Of 
this  i  cubic  metre  is  required  for  every  200  kilos,  of  the  alloy  treated ;  it  is 
obtained  as  a  mother-liquor  on  the  crystallisation  of  silver  sulphates.  As  the  liquid 
cools,  silver  sulphate  crystallises  out,  whilst  copper  sulphate  remains  in  solution. 
Upon  the  silver  sulphate  crystals  a  hot,  saturated  neutral  solution  of  ferrous 
sulphate  is  conducted,  which  first  dissolves  copper  sulphate,  then  reduces  the  silver- 
sulphate,  takes  up  the  free  acid,  and  flows  off,  at  first  as  a  blue  and  then  as  a  brown 
liquid,  until  a  green  colour  indicates  the  end  of  the  reduction.  The  blue  cupriferous 
liquid  is  preserved  separately  from  the  brown  liquid,  in  which  there  are  still  in 


«ECT.    II.] 


GOLD. 


solution  2-5  per  cent.,  of  silver.     The  reduction  is  complete  in   3  to  4  hours.     The 
solution  of  ferric  oxide  is  re-converted  into  a  ferrous   salt  by  the  addition  of  waste 


iron. 


Chemically  pure  gold  is  obtained  by  dissolving  gold  in  aqua  reyia  ;  the  solution  is 
separated  from  silver  chloride,  &c.,  by  filtration;  the  filtrate  is  evaporated  to  dryness, 
the  remaining  gold  chloride  is  taken  up  in  water,  and  the  gold  is  precipitated  by  a 
solution  of  ferrous  sulphate :  2AuCl3  +  6FeS04  =  2Au  +  2Fe2(S04)3  +  Fe2Cl6. 

Properties. — Gold  is  yellow,  but  very  small  traces  of  other  metals  can  modify  its 
colour.  It  takes  a  very  high  polish.  In  hardness  it  is  little  superior  to  lead,  but  it  is 
the  most  malleable  and  extensible  of  all  metals.  It  possesses  an  absolute  solidity 
almost  equal  to  that  of  silver.  Its  elasticity  is  unimportant,  whence  it  is  but  little 
;sonorous.  Its  sp.  gr.  varies  from  19^25  in  the  cast  and  unextended  state,  to  19*55, 
and  even  to  19-6,  when  it  has  been  condensed  by  mechanical  manipulation.  Gold  fuses 
at  1037°  Deville,  1075°  Erhard,  and  after  casting  it  contracts  strongly  in  the  mould. 
Melting  gold  shines  with  a  sea-green  colour.  Its  value  is  much  increased  by  the  fact 
that  it  remains  unaffected  in  the  air,  in  sulphuretted  gases  (see  Skey's  observations, 
p.  190),  in  water,  and  in  contact  with  all  acids,  except  aqua  regia.*  Of  all  metals 
gold  has  the  greatest  tendency  to  combine  with  mercury.  In  thin  leaves  it  is  trans- 
lucent with  a  blue  or  a  green  light  according  to  its  degree  of  tenuity. 

Gold  Alloys. — Fine  gold  is  not  used  in  the  arts  on  account  of  its  softness;  it  is 
employed  only  for  (genuine)  leaf  gold,  and  for  ornamenting  glass  and  porcelain.  Its 
standard  of  fineness  is  expressed  in  this  country  in  carats.  Absolutely  pure  gold  is 
said  to  be  24  carats  fine.  An  i8-carat  gold  is  understood  to  contain  18  parts  of  fine 
gold  and  6  of  copper  or  silver.  The  alloys  containing  copper  have  a  more  reddish  and 
those  containing  silver  a  more  whitish  yellow  colour. 

The  quantity  of  gold  used  in  ornamenting  earthenware  is  far  larger  than  it  might  be 
supposed.  In  the  year  1869  gold  to  the  value  of  ^60,000  was  used  for  this  purpose 
in  England  alone,  chiefly  in  the  Staffordshire  potteries. 

For  melting  gold  and  silver  alloys  the  furnace  of  Booth  is  preferred  (Figs.  188 
and  189),  as  every  loss  of  the  precious  metal  is  avoided.  The  melting  furnace  is  enclosed 
with  iron  plates  and  provided  with  an 
iron  ash-pit,  A.  In  order  to  recover  any 
gold  and  silver  which  may  adhere  to  the 
furnace-bars,  R,  these  are  occasionally 
melted  and  kept  for  a  long  time  in  a 
liquid  condition,  so  that  gold  or  silver 
may  subside  to  the  bottom. 

All  alloys  of  gold,  when  polished,  dis- 
play colours  differing  from  that  of  pure 
.gold ;  they  appear  reddish  or  pale  yellow. 
In  order  to  give  to  such  alloys  the  intense 
yellowness  of  pure  gold  they  are  boiled  in  a  liquid  (gold-colour)  consisting  of  common 
salt,  saltpetre,  and  hydrochloric  acid.  The  action  of  the  "  gold-colour  "  depends  on  its 
property  of  dissolving — by  means* of  the  chlorine  evolved — a  little  gold  from  the 
:  surf  ace  of  the  object,  and  then  re-depositing  it  as  a  thin  film,  so  that  the  surface  may 
be  richer  in  gold  than  the  interior  of  the  metal.  The  same  object  can  be  as  well 
effected  by  the  galvanic  gilding  process. 

Gold  Proof. — In  oi'der  to  ascertain  rapidly  the  fineness  of  a  gold  alloy,  goldsmiths 
make  use  of  the  touch-stone  and  the  "  touch  needles."  These  are  needles  of  gold 
alloyed  with  different  proportions  of  silver  or  copper.  A  mark  is  first  made  upon 

*  It  is  also  soluble,  according  to  Mitscherlich,  in  selenic  acid,  and  according  to  Gay-Lussac,  in 
iodic  acid.  See  also  Notes  on  the  Treatment  of  Gold  Ores,  by  Fl.  O'Driscoll,  Assoc.  M.  Inst.  C.E. 


1'ig.  1 88. 


Fig.  189. 


196  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

the  stone  with  the  article  in  question,  which  is  then  compared  with  marks  made  with 
the  different  needles.  The  mark  is  then  treated  with  dilute  aqua  regia,  and  the 
quality  is  judged  by  the  permanence,  or  the  more  or  less  rapid  disappearance  of  the 
streak.  This  process,  of  course,  can  merely  give  approximate  results,  and  it  must  be 
considered  that  the  surface,  especially  of  articles  of  jewellery,  has  in  many  cases  been 
made  richer  in  gold  by  the  processes  above-mentioned. 

The  best  proof  is  cupellation.  For  this  purpose  the  auriferous  granule  is  melted 
up,  according  to  its  colour,  with  a  triple,  double,  or  equal  weight  of  silver,  and  with 
about  ten  times  the  quantity  of  lead.  It  is  then  assayed  in  the  usual  manner.  The 
argentiferous  bead  is  flattened  out,  digested  in  nitric  acid,  the  residual  gold  is  washed,. 
dried,  and  weighed. 

Gilding. — Gilding  is  effected  either  by  gold-leaf,  by  plating  in  the  wet  way,  by 
tire  gilding,  or  by  the  galvanic  process. 

Articles  of  wood,  stone,  cast-iron,  ike.,  are  gilt  with  leaf -gold.  The  gold  leaf  intended 
for  this  process  is  obtained  by  casting  fine  gold  in  ingots,  forging  it  out  in  plates,  and 
then  rolling  it  into  sheets.  Twenty  ducats  yield  sheet  gold  of  16  metres  in  length  and 
3  centimetres  in  width,  which  are  cut  up  into  quarters  (so-called)  of  3  centimetres  in 
length.  These  sheets  are  first  beaten  out  between  leaves  of  parchment,  and  then 
between  the  exterior  membrane  of  the  caecum  of  the  ox.  The  finished  leaves  are  laid 
in  small  books  of  very  smooth  paper  rubbed  with  a  little  bole  or  ruddle  to  prevent  the 
gold  leaves  from  adhering.  The  residues  serve  for  preparing  (genuine)  gold  bronze. 
The  objects  to  be  gilt  are  first  coated  with  a  mixture  of  white  lead  and  varnish  or  glue 
and  chalk,  and  then  covered  with  gold  leaf.  Articles  of  iron  and  steel,  such  as  the 
blades  of  swords  and  the  barrels  of  guns  are  first  treated  with  nitric  acid,  heated  until 
they  turn  blue,  and  then  covered  with  leaf  gold. 

Talmi  gold  (first  introduced  into  commerce  by  the  Parisian  manufacturer  Tallois), 
is  a  yellow  alloy  of  copper,  coated  with  gold  in  the  state  of  wire  and  sheets,  and  then 
further  wrought  up. 

Gilding  in  the  cold  way  is  effected  by  dissolving  fine  gold  in  aqua  regia,  dipping 
linen  rags  in  the  solution,  drying  and  burning  them  to  tinder.  The  ash  contains  finely 
divided  gold  and  carbon  which  are  rubbed  by  means  of  a  cork  dipped  in  salt  water 
upon  the  surface  of  the  copper,  brass,  or  silver  to  be  gilt,  and  which  must  previously 
have  been  cleansed  and  polished. 

Gilding  in  the  wet  way  is  conducted  by  plunging  the  objects  into  a  dilute  solution 
of  gold  chloride,  or  into  a  boiling  mixture  of  dilute  solution  of  gold  chloride  with  a 
solution  of  sodium  carbonate.  Iron  and  steel  which  are  to  be  gilt  in  this  way  are  first 
coated  with  copper  by  immersion  in  a  solution  of  copper  sulphate.  Articles  of  iron 
which  are  to  be  gilt  in  the  wet  way,  may  first  be  corroded  with  nitric  acid,  brushed 
over  with  a  solution  of  gold  chloride  in  ether,  and  heated.  The  action  is  almost  instan- 
taneous. A  solution  of  gold  chloride  in  sodium  pyrophosphate  has  been  recommended 
as  a  bath  for  gilding  in  the  wet  way. 

Gilding  in  the  fire,  especially  for  articles  of  bronze,  brass,  or  silver,  corresponds 
very  closely  with  silvering  in  the  fire.  The  surface  to  be  gilt  is  coated  with  a  gold 
amalgam,  with  the  intervention  of  a  solution  of  mercury  in  nitric  acid,  and  the  article 
is  then  heated  to  expel  the  mercury,  leaving  the  gold  as  a  thin  film  adhering  to  its 
surface.  The  gold  amalgam  used  consists  of  two  parts  gold  and  one  part  mercury. 
The  gilding  is  either  made  brilliant  by  polishing  or  it  is  kept  dead.  If  the  gilding 
is  to  have  the  reddish  polish  of  gold  alloyed  with  copper,  the  bronzes,  after  the 
expulsion  of  the  mercury,  are  dipped  in  melted  gilders'  wax  (a  mixture  of  wax,  bole, 
verdigris,  and  alum),  and  the  wax  is  allowed  to  burn  off  over  a  charcoal  fire.  The 
copper  oxide  of  the  verdigris  is  reduced  to  copper  which  combines  with  the  gold  to 
form  a  reddish  alloy.  Iron  and  steel  are  previously  coated  with  copper. 


SECT,  ii.]  PLATINUM.  i97 

Galvanic  Gilding. — For  preparing  a  gold  bath  100  grammes  of  potassium  cyanide  are 
dissolved  in  i  litre  of  distilled  water.  For  this  solution  7  grammes  of  fine  gold  are 
dissolved  in  aqua  regia,  cautiously  evaporated  to  dryness,  the  residue  taken  up  in  a 
little  distilled  water,  and  the  liquid  added  to  the  solution  of  the  cyanide. 

PLATINUM. 

Occurrence. — Platinum  is  found  only  native  and  in  small  quantity  in  the  so-called  plati- 
num-ore met  with  in  Columbia  and  Peru,  in  alluvial  deposits,  and  on  the  Ural,  in  the 
form  of  small,  rounded,  steel-grey  grains — rarely  nuggets — of  a  metallic  lustre.  Re- 
cently it  has  been  found  among  gold-sand  in  California,  in  Oregon,  Brazil,  Haiti, 
Australia,  and  Borneo,  and  very  lately  in  the  Norwegian  parish  of  Roeraas,  disseminated 
in  rocks,  as  also  in  the  sands  of  the  Ivalo  River  in  northern  Lapland.* 

It  was  first  discovered  by  the  Spanish  mathematician,  Antonio  d'  Ulloa,  in  the 
gold-bearing  sand  of  the  river  Pinto  in  Choco  (New  Granada) ;  it  was  at  first  taken 
for  silver,  until  in  1752  its  distinct  metallic  character  was  recognised  by  Schaffer,  the 
Master  of  the  Swedish  Mint. 

The  ores  occurring  in  commerce  under  the  names  of  platinum  ore,  native  platinum, 
or  crude  platinum,  are  mixtures  of  platinum  with  palladium,  rhodium,  iridium,  osmium, 
ruthenium,  iron,  copper  and  lead,  and  contain  also  generally  grains  of  osmium -iridium, 
gold,  chrome-iron,  titanif erous  iron,  spinel,  zircon,  and  quartz. 

Platimim  ores  from  Ural  (I.),  Columbia  (II.),  Choco  (III.),  Borneo  (IV.),  and 
California  (V.),  contained : 

I.  II.  III.  IV.  V. 

Platinum       .        .  86-50        ...  84-30  ...  86'i6  ..  71*87  ...  5775 

Rhodium        .         .  1^15         ...  3-46  ...  2'i6  ...  ...  2-45 

Iridium          .        .  ...  1-46  ...  1-09  ...  7-92  ...  3-10 

Palladium      .  no         ...  ro6  ...  0-35  ...  1-28  ...  0-25 

Osmium-iridium     .  1*14         ...  ...  1*91  ...  8-43  ...  27^65 

Osmium         .        .  ...  1*03  ...  0^97  ..  0-48  ...  o- 

Copper          .        .  o'45         ...  074  ...  0^40  ...  0^43  ...  0-20 

Iron       .        .         .  8-32         ...  5-31  ...  8-03  \ 

Lime      ...  ...  0-12  ...  -    [  ...  8-40  ...  770 

Quartz   ...  ...  o'6o 

The  yearly  supply  of  platinum  is  about  450  kilos,  from  the  South  American  localities, 
120  from  Borneo,  and  3600  from  the  Ural. 

For  the  extraction  of  platinum  from  its  ores  they  are  first  heated  to  redness  and 
covered  with  cold  aqua  regia  to  remove  gold  ;  filtered,  and  the  residue  is  again  treated 
with  aqua  regia  in  a  retort.  The  liquid  distilled  off  contains  osmium,  whilst  the  undis- 
solved  residue  consists  of  osmium-iridium,  ruthenium,  chrome-iron  and  titanif  erous  iron, 
whilst  the  solution  contains  palladium,  platinum,  rhodium,  and  a  little  iridium.  The 
solution  is  neutralised  with  sodium  carbonate  and  mixed  with  a  solution  of  potassium 
cyanide,  when  the  palladium  is  eliminated  as  a  cyanide.  The  filtrate  is  concentrated- by 
evaporation,  and  mixed  with  a  saturated  solution  of  ammonium  chloride  whereby 
PtCl42NH4Cl  is  thrown  down  along  with  a  small  quantity  of  iridium.  For  technical  uses 
the  slight  admixture  of  iridium  is  advantageous,  as  it  confers  upon  the  platinum  the  hard- 
ness necessary  for  working.  The  double  ammonium-platinum  chloride  is  dried  and  ignited 
leaving  metallic  platinum  as  a  spongy  mass  (platinum  sponge).  This  mass  is  then  com- 
pressed in  iron  cylinders  with  steel  pistons  at  a  red  heat,  repeating  this  operation  until 
the  metal  has  the  appearance  of  melted  platinum,  and  is  sufficiently  dense  for  working. 

According  to  Descotils,  the  platinum  ores  are  to  be  smelted  with  2  to  4  parts  of 

*  It  is  very  probable  that  platinum  may  have  often  been  overlooked  in  California  and  Australia 
in  the  earlier  and  pre-scientific  days  of  gold-digging. 


I98  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

zinc,  the  homogeneous  brittle  mass  powdered  and  sifted,  the  zinc  and  the  chief  part  of 
the  iron  dissolved  out  with  dilute  sulphuric  acid,  and  the  residue  treated  first  with  nitric 
acid  to  extract  iron,  copper,  and  lead,  and  then  with  aqua  regia,  which  dissolves  the  plati- 
num, &c.,  much  more  easily  on  account  of  its  finely  divided  state.  The  process  is  then, 
completed  in  the  usual  manner. 

In  the  process  of  H.  Sainte  Claire  Deville  and  Debray  lead  is  used  to  dissolve  all 
the  metals  of  the  platinum  ore  except  osmium-iridium  and  iron.  The  ore  is  smelted  in  a 
reverberatory  with  an  equal  weight  of  galena  and  a  little  glass,  yielding  a  regulus,  at 
the  bottom  of  which  is  the  osmium-iridium,  whilst  a  lead-slag  floats  on  the  surface  of  the 
regulus.  This  platiniferous  regulus  is  refined  on  the  hearth,  when  all  the  foreign  metals 
are  volatilised  and  absorbed  into  the  hearth,  whilst  the  platinum  which  remains  is  refined 
in  lime  crucibles.  The  lime  here  acts  upon  all  such  impurities  as  silicon,  iron,  copper, 
<fec.,  and  converts  them  into  fusible  compounds,  which  withdraw  into  the  porous  mass  of 
the  crucible.  To  fuse  i  kilo,  of  platinum  there  are  required  100  litres  oxygen  and  300 
litres  of  coal-gas.  Still  higher  temperatures  may  be  obtained  with  the  electric  smelting 
furnace  of  W.  Siemens  which,  however,  has  not  yet  been  applied  for  this  purpose. 

Properties. — Platinum  is  almost  of  a  silvery-white  but  with  a  slight  steel-grey  cast, 
it  is  shining,  malleable,  and  ductile  and  so  soft  that  it  may  be  cut  with  shears.  It  may 
be  drawn  out  to  wire  which  is  almost  microscopic.  For  this  purpose  a  platinum  wire 
is  coated  with  silver  and  drawn  as  finely  as  possible  in  the  ordinary  manner.  It  is 
then  treated  with  nitric  acid,  which  dissolves  off  the  silver  and  leaves  the  platinum 
untouched.  Its  sp.  gr.  is  21*504.  It  can  be  welded  and  fused  before  the  oxyhydrogen 
blast.  Platinum  sponge  and  platinum  black  have  the  property  of  condensing  gases  in 
their  pores  in  extraordinary  quantities.  If  hydrogen  comes  in  contact  with  these 
substances  it  combines  with  oxygen  so  as  to  form  water  by  intervention  of  the  platinum. 
This  combination  is  effected  with  so  great  a  development  of  heat  that  the  platinum 
is  ignited  and  hydrogen  passed  up  against  it  takes  fire.  (Dobereiner's  hydrogen  lamp.) 

Platinum  black  is  platinum  in  a  state  of  very  fine  division  ;  it  is  produced  either  by 
boiling  platinum  sulphate  with  sodium  carbonate  and  sugar,  when  the  platinum  blr.ck 
is  precipitated  as  a  powder,  or  by  melting  together  platinum  and  zinc,  and  dissolving 
the  alloy  in  dilute  sulphuric  acid.  Platinum  black  possesses  the  property  of  condensing 
gases  in  a  still  higher  degree  than  spongy  platinum,  and  serves  thus  for  converting 
alcohol  into  acetic  acid. 

Platinum  may  be  worked  up  either  by  rolling  or  by  fusion  and  casting.  The 
manufacture  has  been  lately  developed  by  Heraeus,  of  Hanau,  and  especially  by 
Matthey,  of  the  firm  of  Johnson  &  Matthey,  of  London.  It  serves  for  chemical  and 
technical  apparatus,  which  are  not  attacked  by  high  temperatures  or  by  most 
substances.  Still  they  must  be  treated  with  great  care,  and  especially  must  not  be  ex- 
posed to  contact  with  fused  caustic  alkalies,  melting  saltpetre,  free  chlorine,  aqua  regia, 
sulphur  and  sulphides,  phosphorus,  melted  metals  and  easily  reducible  metallic  oxides 
(especially  along  with  carbonaceous  matter).  The  articles  made  of  platinum  are 
sheets,  wires,  crucibles,  spoons,  nozzles  for  blow-pipes,  points  for  lightning  conductors, 
retorts,  forceps,  pans  for  refineries  and  sulphuric  acid  works;  it  serves  also  in  the 
manufacture  of  galvanic  elements,  glow-lamps,  and  for  coating  copper  capsules, 
porcelain,  stone-ware  and  glass.  Platinum  has  been  used  for  producing  the  standard 
measures  (copies  of  the  original  Paris  metre)  resolved  on  by  the  International  Com- 
mission of  Weights  and  Measures.  The  standard  measures,  which  were  prepared  by 
Mr.  Matthey  (Johnson  &  Matthey),  consist  of  an  alloy  of  90  parts  platinum  and  10 
parts  iridium,  and  are  much  harder  than  pure  platinum.  Similar  alloys  are  now 
preferred  as  the  material  for  platinum  crucibles. 

In  Russia,  platinum  was  coined,  from  the  year  1828,  into  3,  6  and  12  rouble  pieces. 
In  1845,  tne  coining  of  these  pieces  (which  had  already  consumed  or  wasted  14,250 
kilos,  of  this  indispensable  metal)  ceased,  and  the  pieces  already  issued  were  called  in. 


SECT.    II. 


199 


In  1877,  S.  Kern  found  in  the  metal  of  platinum  crucibles,  made  in  Paris- 
Platinum  .      _.         .     9870  per  cent.         ...        97 -90  per  cent. 
Iridium      .         .         .       0^56        ,,  ...  1-40        ,, 

Iron  .         .         .       030        , 

Copper      .         .         .       o-22        „  ...  0-67        „ 


TIN. 

Tin  is  one  of  the  rarer  metals.  It  never  occurs  native,  but  oxidised  as  cassiterite 
or  tin-stone,  Sn02  or  as  stannine,  tin  sulphide,  combined  with  other  sulphides  in  tin 
pyrites  (2Cu2S  +  SnS2  +  2FeS,ZnS)SnS2. 

Tin-stone  is  found  in  situ  in  granite,  syenite,  mica-slate,  porphyry,  <fec.,  or  in 
secondary  and  alluvial  deposits  (wash-tin,  tin  sand,  &c.) ;  contains  in  addition  to  tin- 
oxide,  sulphur,  arsenic,  zinc,  iron,  copper,  and  other  metals.  It  also  occurs  in  the 
sand  of  rivers  as  almost  chemically  pure  stannic  acid.  Such  tin,  and  that  obtained 
from  washings,  gives  a  much  purer  metal  than  vein-tin,  as  Nature  has  here  already 
executed  a  mechanical  purification.  The  vein  ores  are  first  separated  by  stamping  and 
elutriation  from  the  gangue  and  freed  from  sulphur,  arsenic,  and  antimony  by  roasting. 

According  to  the  process  in  use  at  Altenberg  in  the  Erzgebirge,  the  ore,  after 
roasting,  is  smelted  in  shaft-furnaces,  3  metres  in  height  (Fig.  190,  I.  and  II.).  The 

I.  Fig.   190. 


walls,  constructed  of  granite,  rest  upon  a  founda- 
tion of  gneiss.  The  bottom  stone,  D,  cojisists  oi; 
one  piece,  hollowed  out  to  form  a  dish.  The  fore- 
hearth,  B,  is  connected  by  a  tap-hole  with  an  iron 
pan ;  the  tuyere  of  the  blast  opens  into  the  shaft 
at  o.  The  ore  mixed  with  coal,  coke  or  charcoal,  is 
placed  in  the  shaft,  A  ;  the  reduced  tin  collects  in  the  fore-hearth,  B,  whence  it  flows 
into  the  pan,  C.  It  contains  iron  and  arsenic;  from  these  impurities  it  is  freed  by 
eliquation  on  a  hearth  covered  with  ignited  fuel.  The  pure  tin  melts  first,  flows 
through  the  fuel  and  collects  on  the  tapping  hearth,  whilst  a  less  fusible  alloy  of  tin 
with  iron,  &c.,  remains  in  grains,  which  the  Saxon  miners  call  "  thorns."  The  slags, 
which  often  contain  15  to  18  per  cent,  of  tin,  are  smelted  from  time  to  time,  yielding 
tin  and  a  residue  which,  like  the  "  thorns,"  consists  of  an  alloy  of  tin  and  iron. 

The  tin  obtained  in  shaft  furnaces  is  very  pure,  containing  scarcely  ^  per  cent,  of 
foreign  metals.  It  is  known  as  grain  tin.  The  less  fusible  alloy  is  re-melted  and  sold 
as  block  tin.  The  presence  of  tungsten  in  fhe  ores  greatly  interferes  with  the  pro- 
duction of  pure  tin. 

Australia  produces  yearly  10  to  15,000  tons,  Britain  10,000,  the  Straits  (Malacca) 
10,000,  Banka  and  Billiton  9000,  Tasmania  3-5000,  Altenberg  150.* 

*  It  is  found  in  New  Granada,  but  the  Western  hemisphere  contributes  practically  nothing  to 
the  commercial  supply.  Tin  ores  have  also  been  worked  in  Central  Asia,  on  the  north  and  north- 
west of  Afghanistan,  but  nothing  definite  is  known  concerning  the  extent  and  the  capabilities  of 
the  deposits. 


200  CHEMICAL   TECHNOLOGY.  [SECT.  n. 

Tin  has   a  silvery  colour,  but  with  a    bluish  cast,  and  a  perfect  metallic  lustre. 
Next  to  lead  it  is  the  softest  of  the  metals,  but  it  possesses  so  much  hardness  that  a 
bar  of  tin,  freely  suspended,  gives  a  sound  if  struck.     If  bent  it  creaks,  the   more 
decidedly  the  higher  its  purity.      Tin  is  very  malleable,  and  can  be  wrought  out  to 
very  thin  leaves.     If  rubbed  it  imparts  a  peculiar  and  very  persistent  smell  to  the 
hands.     The  sp.  gr.  of  pure  tin  is  7'28,  but  by  hammering  and  rolling  it  can  be  raised 
to  7-29.*   If  heated  almost  to  its  melting-point,  it  becomes  brittle,  and  can  be  broken  up 
with  the  hammer.     If  used  for  castings,  its  lustre  and  tenacity  depend  entirely  upon 
its  temperature  at  the  moment  of  casting.     If  heated  so  strongly  as  to  show  in  flowing 
colours  upon  its  surface,  it  appears  striped  after  solidifying,  and  is  called  "  red  shoot." 
If  heated  too  little  it  is  called  "  cold  shoot",  and  has  a  dull  surface.     At  a  strong  white 
heat  tin  begins  to  boil  and  slowly  evaporates.   Melted  tin  becomes  covered  on  its  surface 
with  a  grey  film,  consisting  of  stannous  oxide  and  metallic  tin.     By  continued  fusion  in 
presence  of  air,  tin  is  completely  converted  into  a  yellowish-white  oxide,  tin-ashes.    On 
exposure  to  the  air  tin  gradually  loses  its  lustre. 

Assay  of  Tin  Ores. — For  suitable  methods  we  may  refer  the  reader  to  "  Select 
Methods  in  Chemical  Analysis,"  by  W.  Crookes,  F.R.S.,  p.  403  ;  for  the  determination 
of  lead   in  samples   of  tin,  ibid.  p.  409 ;  for  the   separation   of  tin  from  copper,  ibid. 
p.  410  ;  and  for  the  commercial  analysis  of  tinware,  ibid.  p.  413. 

Uses. — Tin  is  used  in  alloys  (gun-metal,  bronze,  phosphor-bronze,  bell-metal),  and 
formerly  more  than  at  present  for  domestic  and  table  requisites,  for  the  capitals  of 
stills,   for  cooling-apparatus,  and  tubs,  dye-pans,  and  laboratory  appliances.     Tin  is 
used  along  with  lead,  because  these  alloys  are  harder  than  either  of  the  constituents 
alone,  and  resist  wear  better.     By  rolling  and  beating,  tin  is  extended  to  tin-foil,  the 
stronger  sort  of  which  is  used  for  lining  mirrors — so-called  silvering — and  the  thinner 
kind  for  lining  boxes,  wrapping  up  chocolate,  fancy  soaps,  sweetmeats,  &c,f     Stolzel 
found  in  four  qualities  : 

Tin      .        .     97-60  ...  97-81  ..  98-47  ...  96-21 

Copper         .       2-16  ...  1-23  ...  0-38  ...  0-95 

Lead   .         .       0*04  ...  0-76  ...  0*84  ...  2-41 

Iron    .        .      o'li  ...  o'io  ...  0-12  ...  0*09 

Bismuth      .      trace  ...  ...  ..  — 

Nickel         .       —  ..  —  ...  —  ...  0-29 

99'9i  ...  99'90  ...  99'8r  ...  99-95 

False  leaf  silver  is  tin  mixed  with  a  little  zinc,  and  beaten  out  to  thin  leaves.  Tin 
with  small  proportions  of  copper,  antimony  and  bismuth,  is  often  used  for  spoons,  &c. 
A  similar  alloy  is  Britannia-metal,  used  for  spoons,  candlesticks,  coffee-  and  tea-pots,  as 
it  approximates  more  to  silver  in  its  appearance  than  does  tin  ;  it  is  harder,  takes  a 
better  polish,  and  is  more  easily  wrought  and  rolled  out  to  sheets.  It  consists  of  90 
parts  of  tin,  with  10  of  antimony,  and  generally  small  quantities  of  copper  (0*09  to 
0-8  per  cent.) ;  frequently  i  to  3  per  cent,  of  zinc ;  in  one  case,  in  an  English 
sample  1*83  per  cent,  of  arsenic.  Britannia-metal  articles  are  sometimes  silvered. 

As  the  metals  with  which  tin  is  likely  to  be  contaminated — accidentally  or  inten- 
tionally—have all  a  higher  sp.  gr.  than  tin,  a  determination  of  the  sp.  gr.  of  a  sample 
gives  an  indication  of  its  purity.  Alloys  of  tin  and  lead  in  the  ordinary  proportions 
have  the  following  specific  gravities  : — 


Sp.  gr. 

iSn  +  iPb  .  .  .  8-864 
iSn  +  2Pb  .  .  .  9-953 
iSn  +  3Pb  .  .  .  9-9387 


Sp.  gr. 

iSn  +  4?b  .  .  .  10-183 
2Sn  +  iPb  .  .  .  8-226 
3Sn  +  iPb  .  .  .  7-994 


*  Solid  pieces  of  pure  tin  float  upon  a  bath  of  melted  tin,  just  as  does  ice  upon  water. 
t  There  occur  in  commerce,  however,  tin-foils  containing  a  large  percentage  of  lead,  and  con- 
sequently unfit  for  contact  with  articles  of  food. 


:SECT.    II.]  BISMUTH.  201 

Tin-ash,  mentioned  above,  is  used  in  polishing  glass  and  metals,  and  for  giving  a 
white  colour  to  enamels. 

Tinning. — The  objects  to  be  tinned  are  previously  cleaned  by  scouring,  washing, 
or  by  acid  liquids.  The  oxidation  of  the  layer  of  tin  to  be  applied  is  prevented  by 
means  of  resin  and  sal-ammoniac,  which  reduce  immediately  any  oxide  that  has  been 
formed.  Copper  and  wrought-iron  are  easily  tinned,  the  vessel  or  other  article  to  be 
tinned  being  heated  almost  up  to  the  melting-point  of  tin ;  melted  tin  is  then  poured 
upon  it,  and  the  metal  is  spread  over  the  surface  of  the  copper,  &c.,  by  means  of  a 
bunch  of  tow,  upon  which  sal-ammoniac  has  been  scattered.  Articles  of  brass,  e.g., 
pins,  are  boiled  in  tinned  pans  with  granulated  tin,  and  with  a  solution  of  potassium 
bitartrate.  The  tinned  articles  are  then  rubbed  with  bran  or  sawdust.  Sheet-iron, 
which  must  be  of  the  best  quality,  before  tinning  is  very  carefully  cleansed  with  bran- 
water  which  has  turned  sour,  and  with  dilute  sulphuric  acid,  plunged  into  melting 
tallow,  and  then  into  melted  tin.  The  tallow  protects  the  tin  from  oxidation.  After 
the  sheets  are  sufficiently  coated  with  tin,  they  are  taken  out,  cleared  from  any  excess 
of  tin,  and  cleaned  with  bran.* 

The  clippings  of  tin-plate  (tinners'  waste),  which  contain  7  to  8  per  cent,  of  tin,  are 
•collected,  freed  from  tin,  and  used  as  scrap-iron  or  worked  up  to  ferrous  sulphate.  The 
removal  of  the  tin  is  sometimes  effected  by  treatment  with  a  mixture  of  nitric  and 
hydrochloric  acids,  and  from  the  nearly  neutral  solution  (which,  of  course,  contains 
iron  chloride)  the  tin  is  thrown  down  by  means  of  zinc.  Or  the  tin  waste  is  sus- 
pended as  an  oxide  in  dilute  sulphuric  acid,  the  tin  is  deposited  upon  copper  sheets 
connected  with  the  negative  pole  and  may  be  taken  off  in  plates,  f 

If  tin-plates  are  corroded  with  acids,  it  often  results  that  deposits  of  a  nacreous 
lustre  appear  on  the  surface,  due  to  the  crystallisation  of  the  tin  on  rapid  cooling.  On 
treatment  with  a  mixture  of  2  parts  hydrochloric  acid,  i  part  nitric  acid,  and  3  parts 
of  water,  the  crystalline  places  are  made  apparent,  which  appear  duller  or  brighter 
according  to  the  unequal  reflection  of  the  light.  Crystalline  surfaces  may  be  produced 
by  the  prolonged  action  of  melted  palmitic  acid.  Such  tin-plate  is  called  moire  metal- 
lique.  They  are  found  with  large  regular  hexagons,  others  with  squares,  the  small 
crystals  recalling  the  aspect  of  granite  or  gneiss ;  others  like  mosses  and  ferns,  large 
trees  or  seaweeds,  a  strange  regularity  along  with  fantastic  irregularity.  Splendid  effects 
may  be  produced  with  the  aid  of  lacquers,  showing  the  lustre  of  many-coloured  nacre, 
along  with  the  full  colours  of  tortoise-shell,  granite-like  plates,  apparently  covered 
'with  elegant  dendrites,  the  lustre  of  which  is  heightened  by  appropriate  colours. 

BISMUTH. 

Bismuth  ranks  among  the  rarer  metals.  It  is  found  at  Schneeberg  in  the 
Erzgebirge,  in  Peru,  Chile,  and  Australia  ;  mostly  native  in  cobalt  and  silver  veins  in 
granite,  gneiss,  mica-slate,  and  in  transition  formations.  It  is  also  met  with  oxidised  as 
bismuth  ochre,  Bi203,  and  combined  with  sulphur  as  bismuthine,  Bi2S3,  or  as  cupreous 
bismuth  (containing  49*24  per  cent,  of  bismuth). 

The  chief  supply  of  bismuth  is  from  the  Saxon  blue-colour  works  at  Oberschlema 
and  Pfannenstiel,  which  are  in  possession  of  the  great  deposit  of  bismuth  at  Schnee- 
berg. Formerly  bismuth  was  obtained  from  its  ores  by  eliquation,  the  mineral  being 
heated  in  iron  pipes,  laid  in  a  sloping  position,  when  the  bismuth  was  liquefied,  and 

*  Tern-plates  are  sheet-iron  coated,  not  with  pure  tin,  but  with  an  alloy  of  tin  and  lead.  Tern 
Is  employed  for  inferior  wares,  but  should  never  be  used  for  tins  or  cans  for  preserved  milk, 
meat,  fruits,  or  vegetables,  all  of  which  act  more  or  less  upon  the  metals,  and  dissolve  a  quantity 
of  lead,  which  may  in  time  have  serious  effects.  It  has  also  been  found  that  in  soldering  up 
•canned  provisions  zinc  chloride  has  been  used  instead  of  resin  and  with  most  serious  effects. 

f  No  process  as  yet  known  is  perfectly  satisfactory.     Tern-waste  is  quite  useless. 


202  CHEMICAL  TECHNOLOGY.  [SECT.  u. 

ran  off.  In  this  manner,  only  that  part  of  the  bismuth  was  obtained  which  was  present 
in  the  metallic  state,  and  even  this  very  incompletely.  The  rest,  on  the  smelting  of 
the  cobaltiferous  residues,  passed  into  the  smalt- glass,  when  the  bismuth  collected  in 
the  cobalt-speiss,  and  was  again  separated  by  eliquation.  This  imperfect  process  has 
long  ago  been  abandoned. 

At  the  Saxon  blue-colour  works,  all  the  bismuth  and  bismuth-cobaltic  ores  are  first 
roasted,  and  are  then  smelted  in  the  crucibles  of  the  smalt-glass  furnaces,  with  the 
addition  of  carbon,  iron,  and  slag.  The  reduced  metal  beneath  the  slag  forms  two 
very  distinct  layers,  the  upper,  consisting  of  cobalt-speiss  (cobalt-nickel  and  iron- 
arsenides),  the  lower  of  bismuth.  As  the  melting  point  of  bismuth  is  very  low,  it  is 
run  off  in  a  liquid  state  as  soon  as  the  super jacent  layer  of  speiss  has  solidified. 

This  crude  bismuth  is  tolerably  pure,  containing  only  small  quantities  of  iron, 
cobalt,  nickel,  lead,  silver,  sulphur,  and  arsenic.  The  purification  is  effected  by  kindling 
a  wood  fire  on  an  iron  plate,  slightly  sloping,  and  allowing  the  blocks  of  crude  bismuth 
to  be  slowly  melted  down.  The  refined  bismuth,  collected  in  an  iron  dish  previously 
warmed,  is  ladled  out  into  hemispherical  iron  moulds,  which  have  at  the  bottom  the 
arms  of  Saxony.  These  hemispheres  weigh  10  to  12  kilos.,  and  constitute  the  commer- 
cial article. 

At  Freiberg  bismuth  is  also  obtained,  in  the  wet  way,  from  the  litharge  and  ash 
from  silver  refining.  The  ash  is  extracted  with  dilute  hydrochloric  acid.  Basic  bis- 
muth chloride  is  precipitated  from  the  solution  by  the  addition  of  water,  and  is  reduced 
by  melting  in  iron  cmcibles  with  soda,  charcoal,  and  glass. 

The  blue-colour  works  of  Saxony  produce  yearly  18,000  kilos,  of  bismuth  ;  Freiberg, 
2500;  Johanngeorgenstadt,  1500;  Altenberg,  tjoo  ;  and  Britain  (from  exotic  ores), 
2500  kilos. 

Properties. — Bismuth  is  a  reddish -white  metal,  of  a  high  lustre,  a  foliaceous  tex- 
ture, and  so  brittle  that  it  may  be  pulverised.  It  is  slighty  malleable,  if  carefully 
hammered. 

The  respective  composition  of  Saxon  (I.),  Peruvian  (II.),  and  Australian  (III.) 

bismuth  is  as  follows  : — 

I.  ii.  in. 

Bismuth     .        .         .  9977  ...  93'372  ...  94'iO3 

Antimony  ...  —  ...  4'57o  ...  2'62i 

Arsenic      ...  ...  ...  9*290 

•  Copper       .         .         .  O'oS  ...  2x358  ...  i'944 

Silver          .         .         .  0-05 

Sulphur     .  .  o'oi  ...  —  ...  0-430 


99-91  ...  loo-ooo  ...  99'388 

Uses. — Bismuth  is  used  for  alloys,  melted  as  oxide,  with  boric  and  silicic  acids,  for 
optical  glasses,  and  of  late  to  a  considerable  extent  for  porcelain  colours,  and,  as  basic 
bismuth  nitrate,  for  a  cosmetic  (blanc  de  /ard) ;  also  for  medicinal  purposes.  Among 
the  chief  alloys  of  bismuth  are  those  with  lead,  tin,  and  cadmium.  Newton's  fusible 
metal  consists  of  8  parts  bismuth,  3  tin,  and  5  lead,  and  melts  at  64' 5°.  Rose's 
metal  consists  of  2  bismuth,  i  lead,  and  i  tin,  and  melts  at  93*75°.  A  small 
addition  of  cadmium  makes  these  alloys  still  more  fusible.  An  alloy  of  3  parts  lead, 
2  tin,  and  5  bismuth,  melts  at  91 '66°,  and  is  suitable  for  obtaining  cliches  of  woodcuts, 
printing  formes,  stereotypes,  &c.  A  similar  alloy  serves  for  metallic  baths  used  in 
tempering  steel  work,  as  also  for  pencils,  used  instead  of  graphite,  upon  paper  prepared 
with  bone-ash. 

ANTIMONY. 

Occurrence. — Antimony  is  found  chiefly  combined  with  sulphur,  as  stibine  or 
antimony-glance,  Sb2S3,  in  beds  and  veins  in  granite  and  in  crystalline  slate  and  tran- 


SECT.    II.] 


ANTIMONY. 


sition  formations.  It  is  also  met  with  as  antimony  oxide,  Sb203,  in  the  minerals 
valentinite  (rhombic)  and  senarmontite  (tessera!) .  The  latter  occurs  in  great  quantity 
at  Constantine  (Algeria)  and  in  Borneo. 

Extraction. — Antimony  is  chiefly  obtained  by  fusion  followed  by  desulphurising. 
The  smelting  is  effected  in  some  districts,  as  at  Wolsberg  near  Harzgerode,  in  crucibles,. 
b,  (Fig.  191).  The  bottoms  are  perforated  and  fixed  upon  smaller  crucibles,  c,  which 
are  surrounded  with  hot  sand  or  ashes.  At  both  sides  of  the  crucibles  there  are 
draught -holes.  In  order  the  better  to  utilise  the  fuel,  there  is  used  in  other  places  a 
similar  arrangement  with  two  melting  pots  or  crucibles,  which  are  set  on  the  hearth  of 
a  reverberatory  in  such  a  manner  that  only  the  upper,  charged  crucibles  are  touched 
by  the  flame.  The  lower  crucibles  are  set  outside  the  furnace  in  front  of  larger 
crucibles  in  small  vaults,  and  are  connected  with  the  furnaces  by  means  of  stone  ware 
pipes  (Figs.  192  and  193).  The  eliquation  of  antimony  sulphide  can  be  effected  most 
rapidly  when  the  ore — as  is  done  at  Ramee  in  La  Vendee,  is  placed  directly  upon  the 
sloping  hearth  of  a  reverberatory  (Fig.  194)  and  care  is  taken  that  the  antimony 


Fig.  191. 


Fig.  192. 


Fig.  193. 


Fig.  194. 


sulphide,  as  it  melts  out  of  the  ores,  flows  from  the  lowest  point  of  the  hearth  through 
the  channel,  e,  to  a  receiver,  f,  placed  outside  the  furnace. 

After  the  ore  is  in  a  softened  condition  and  a  layer  of  slag  has  been  formed,  the 
tap-hole  is  opened  and  the  heat  is  raised.  The  sulphide  remaining  in  the  ore  collects 
beneath  the  slag  and  is  let  off  after  the  end  of  the  operation. 

For  obtaining  antimony  by  tie  roasting  process,  the  sulphide  is  spread  on  the  sole 
of  a  reverberatory,  and  constantly  turned  over  until  it  is  chiefly  converted  into 
antimony  antimoniate.  The  roasted  product  is  reduced  in  crucibles.  Heating  alone 
would  suffice  for  the  reduction,  as  the  roasted  ore  always  contains  un decomposed  anti- 
mony sulphide:  3Sb.,04  +  2Sb2S3  =  loSb  +  6S02.  But  as  antimony  oxide  would 
volatilise  without  a  cover,  the  roasted  ore  is  mixed  with  crude  argol,  or  charcoal  arid 
soda.  The  regulus  is  allowed  to  cool  slowly  beneath  the  layer  of  slag,  so  as  to  acquire 
that  stellated  crystalline  surface  which  is  preferred  in  trade. 


204  CHEMICAL   TECHNOLOGY.  [SECT.  n. 

It  is  convenient  to  remove  the  sulphur  from  antimony  sulphide  by  a  precipitant 
(iron,  or  spongy  iron).  But  in  the  exclusive  use  of  iron  the  result  of  the  decomposition 
is  unfavourable,  the  separation  of  the  iron  sulphide  from  antimony  being  difficult,  on 
account  of  the  approximate  equality  of  their  specific  gravities.  From  this  reason,  and 
to  render  the  sulphide  at  once  specifically  lighter  and  more  fusible,  an  alkaline  carbonate 
or  sulphate  is  added.  To  100  parts  of  antimony  sulphide,  42  parts  of  iron  waste 
•(wrought),  10  calcined  salt-cake,  and  3-2  parts  of  charcoal  are  found  suitable  proportions. 
To  obtain  a  regulus  free  from  arsenic,  16  parts  of  the  metal  thus  obtained  (to  which, 
if  not  sufficiently  ferriferous,  2  parts  of  iron  sulphide  may  be  added)  are  melted  with 
•i  part  of  antimony  sulphide,  and  2  parts  of  dry  soda,  and  kept  for  an  hour  in  fusion. 
The  regulus  is  melted  a  second  time  with  i^,  and  a  third  time  with  i  part  of  soda, 
until  the  slag  is  of  a  light  yellow.  The  presence  of  iron  sulphide  seems  to  be  a  con- 
dition for  the  elimination  of  arsenic,  as  a  compound  is  formed  similar  to  arsenical 
pyrites:  FeS2  +  FeAs2. 

At  Banya  in  Hungary  antimony  is  smelted  in  the  blast  furnace. 

An  electrolytic  extraction  of  antimony  can  be  effected,  according  to  Borchers,  by 
•decomposing  a  solution  of  3*4  kilos.  Sb2S3  and  7-2  kilos.  Na2S.9H2O  corresponding 
to  the  formula  Sb2S3>3Na2S  with  the  addition  of  2  or  3  per  cent,  sodium  chloride.  The 
resulting  products  were  2-435  kilos,  antimony  and  in  the  solution  1*29  kilos.  NaHS, 
i -2  kilo.  Na2S2  and  1-563  Na2S203<5H2O.  The  process  at  the  kathode  seems  to  have 
been  according  to  the  formula:  Sb2S3-3Na2S  +  3H2  =  Sb2  +  6NaHS,  and  that  at  the 
anode:  6NaHS  +  30  =  3H20  +  3Na2S2. 

Very  poor  antimony  ores  may  be  worked  to  advantage,  as  antimony  tersulphide  is 
•easily  soluble  in  very  dilute  solutions  of  sodium  sulphide.  To  i  mol.  antimony 
tersulphide  there  must  be  present  in  the  liquid  3  mol.  sodium  sulphide.  After  the 
former  is  dissolved,  the  liquid  should  mark  17°  Tw.  (if  hot  12°  to  14°).  About  3  per 
cent,  of  sodium  chloride,  calculated  on  the  entire  quantity  of  the  liquid,  are  added, 
which  helps  to  separate  the  dissolved  iron  sulphide  and  lessens  the  resistance  on 
electrolysis.  If  the  solution  remaining  after  the  precipitation  of  the  antimony  is 
worked  up  for  sodium  thiosulphate,  the  common  salt  separates  out  again  on  the  final 
evaporation.  Iron  vessels  of  any  shape  are  used  as  decomposing  cells  and  serve  at  the 
same  time  as  kathodes.  If  a  vessel  of  quadrangular  section  is  used,  the  kathode 
surface  may  be  increased  by  suspending  in  it  iron  plates.  Between  every  two  iron 
plates  a  lead  plate,  insulated  from  the  iron,  is  suspended  as  an  anode. 

Properties. — The  antimony  of  commerce  contains  arsenic,  iron,  copper,  and  sulphur. 
It  is  purified  by  melting  with  antimony  oxide,  the  oxide  oxidises  the  iron  and  the 
sulphur,  and  is  reduced  in  the  same  proportion.  Antimony  is  nearly  of  a  silver  white, 
with  a  yellowish  cast;  it  has  a  strong  metallic  lustre  and  a  foliaceous  crystalline 
texture.  Like  its  isomorphs  arsenic  and  bismuth,  it  crystallises  in  distinct 
rhombohedrons.  Its  sp.  gr.  is  6-712  and  its  melting  point  430°. 

On  solidifying,  the  melted  metal  does  not  expand.  It  is  not  extensible,  very  brittle, 
and  can  be  easily  pulverised.  It  exceeds  copper  in  hardness.  The  powder  sold  under 
the  name  "  iron  black,"  and  used  for  bronzing  objects  of  plaster  and  papier  mache,  or 
of  cast  zinc  (by  which  they  obtain  the  appearance  of  polished  steel),  is  finely  divided 
antimony,  obtained  by  precipitating  a  solution  with  zinc. 

C.  Himly  found  (1878)  in  three  samples  of  commercial  antimony  : 

Pb 
S 

As 
Cu 

Fe 

Sb 


.     0-34 

0-34 

O*I2 

0-73 

O*T  I 

. 

0-09 

0-36 

1  i 

0-09 

O'OI 

0'02 

O'O2 

. 

.    0-35 

0'34 

0*16 

• 

.    98-98 

98-8I 

98-87 

SECT,  ii.]  ARSENIC.  205 

For  the  assay  of  antimony  ores  and  regulus  the  reader  is  referred  to  Mitchell  & 
Manual  of  Practical  Assaying,  6th  edit.,  edited  by  W.  Crookes,  F.K.S.,  pp.  556,  557,. 
558;  also  to  Select  Methods  in  Chemical  Analysis,  by  W.  Crookes,  F.R.S.,  2nd  edit., 
pp.  396,  400,  and  421. 

Alloys. — An  admixture  of  antimony  in  general  renders  metals  more  lustrous,  hard, 
and  brittle.  "Hard  lead"  contains  antimony  up  to  12  per  cent.  If,  with  Calvert 
and  Johnson,  we  take  the  hardness  of  lead  as  i,  that  of  an  alloy  of  34-86  lead  and  65-14 
antimony  =  11*7,  and  that  of  86-50  lead  and  13*50  antimony  =  4.  Thus,  the  hardness  of 
lead  may  be  increased  almost  twelve-fold  by  the  addition  of  antimony.  Alloys  con- 
taining 17  to  20  per  cent,  of  antimony  form  type-metal.  Of  the  alloys  of  antimony  and 
tin  Britannia  metal  is  the  most  valuable.  It  consists  of  10  parts  antimony  and  90  parts 
tin.  Similar  alloys  are  pewter  (89-3  tin,  7-1  antimony,  r8  copper,  and  i'8  bismuth); 
argentine  (85.5  tin  and  14-5  ant-:noiiy),  sometimes  used  for  spoons  and  forks;  and 
Ashbury  metal  (77*8  tin,  19-4  antimony,  and  2'8  zinc),  used  for  plummer  blocks  for 
locomotives  and  for  the  spindles  of  turners'  lathes.  An  alloy  of  5  antimony,  5  nickel,. 
2  bismuth,  and  87-5  tin  has  been  lately  recommended. 

The  production  of  antimony  is — 

Britain 2000  tons. 

France 580 

Austria-Hungary        ....  800 

Germany 650 

Italy 100 

Spain 8 

ARSENIC. 

Arsenic  occurs  either  native,  or  associated  with  metals,  sulphur,  and  metallic 
sulphides.  The  oxides  of  arsenic  never  occur  in  nature  is  such  quantity  as  to  be  of  any 
technical  importance.  Small  quantities  of  arsenic  are  found  in  all  pyrites,  and  thus 
find  their  way  into  sulphuric  acid. 

Production. — Arsenic  is  obtained  by  subliming  native  arsenic,  or  by  heating 
arsenical  pyrites  (mispickel),  FeSAs,  and  mohsine,  Fe4A6,  or  by  reducing  white 
arsenic  (arsenious  acid)  :  As203  +  3C  =  3CO  +  As2. 

It  is  met  with  in  commerce  in  greyish-black,  crystalline  crusts  of  a  metallic  lustre, 
and  of  sp.  gr.  5-72.  It  evaporates  at  180°,  and  melts  (in  closed  vessels)  at  higher 
temperatures ;  and  sometimes  contains  8  to  10  per  cent,  of  arsenic  sulphide.  Pure 
arsenic  is  used  in  the  manufacture  of  shot,  and  for  producing  a  light  (by  the  combustion 
of  arsenic  in  oxygen)  used  in  trigonometric  and  military  telegraphic  signalling  under 
the  name  of  Bengal  light. 

Arsenious  acid  (arsenious  anhydride,  arsenteroxide,  white  arsenic)  is  obtained  as  a 
by-product  in  working  up  arseniferous  cobalt,  nickel,  silver,  and  tin  ores,  in  the  blue 
colour  works,  in  tin  and  silver  furnaces,  <fcc. ;  the  arsenical  ores  being  roasted  in  rever- 
beratories  and  the  vapours  being  led  into  flues  and  chambers  in  order  to  condense  the 
arsenious  acid.  In  Silesia  arsenical  pyrites  are  roasted  expressly  for  the  production  of 
arsenious  acid.  The  sublimation  is  effected  in  iron  kettles  (a,  Fig.  195),  upon  which  are 
set  iron  rings,  b,  c,  d,  and  upon  these  again  a  dome,  e,  which  is  connected  by  means  of 
pipes  with  the  chamber,  i.  Along  with  this  chamber  there  are  other  chambers.  After 
all  the  joints  and  chinks  have  been  luted  up  the  sublimation  begins.  The  heat  must  be 
increased  so  that  the  arsenious  acid  collecting  in  the  chamber,  i,  begins  to  soften.  When 
cold  it  appears  as  a  perfect  glass  (arsenic  glass)  of  a  conchoidal  fracture,  vitreous  lustre, 
and  transparency,  which  in  time  becomes  white,  porcelain-like,  and  of  an  opaline  or 
waxy  lustre.  Like  the  other  preparations  of  arsenic,  it  is  very  poisonous.  Sometimes 
there  occur  in  arsenious  acid  small  quantities  of  antimony  sulphide  and  oxide. 


206 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


Fig-  i95- 


Arsenious  acid  is  used,  dissolved  in  glycerine,  as  a  mordant  in  calico  printing  ;  it 
serves  also  for  purifying  glass  (especially  crystal  glass)  during  melting,  for  certain 
arsenical  preparations  (alkaline  arsenites,  Schweinf  urt  green,  and  other  copper  colours), 
as  an  antiseptic  in  stuffing  the  skins  of  animals  [which  is  a  dangerous  blunder,  as  its 
antiseptic  power  is  not  great],  for  producing  certain  tar-colours  ;  dissolved  in  hydrochloric 
acid  for  producing  a  grey  colour  on  brass,  and  sometimes  for  hardening  iron.  One 

part  of  crystalline  arsenious  acid  dissolves  in  355  parts 
of  water  at  15°,  whilst  one  part  of  the  amorphous  acid 
takes  only  108  parts  of  water  for  solution. 

Arsenic  Acid,  H3As04,  is  obtained  by  boiling  arse- 
nious acid  in  4  parts  of  nitric  acid  of  sp.  gr.  1-35  and 
evaporating  the  solution  to  dryness,  or  by  passing 
chlorine  into  arsenious  acid  suspended  in  water  or  dis- 
solved in  -hydrochloric  acid.  It  is  sometimes  used 
instead  of  tartaric  acid  in.  calico  printing,  and,  besides, 
for  preparing  tar-colours,  especially  rosaniline  or 
magenta,*  Acid  sodium  arseniate  (sodium  dihydro- 
arseniate,  NalI2As04),  which  is  used  in  print  works 
in  the  "  dunging  process,"  in  place  of  cow-dung,  is 
prepared  by  the  cautious  and  prolonged  heating  of 
36  pai'ts  arsenious  acid  with  30  parts  sodium  ixitrate, 
or  by  heating  a  mixture  of  dry  sodium  nitrate  and 
sodium  arseniate.  By  saturating  the  solution  of  this 
salt  there  is  obtained  the  so-called  "  saturated  arseniate 
of  soda  "  (disodium  hydro-arseniate,  Na,H  AsO4. 1 2H,0), 
which  is  also  vised  in  dyeing  and  tissue  printing. 

Realgar,  As2S2,  is  often  found  in  crystals  in  mineral 
veins,  or  is  produced  artificially  by  melting  sulphur 
with  an  excess  of  arsenic  or  arsenious  acid,  or,  on  the 
large  scale,  by  submitting  arsenical  pyrites  to  dis- 
tillation, or  lastly — as  formerly  done  in  Freiberg — 

by  melting  the  arsenic  sulphide  from  the  sulphuric  acid  works  under  increased 
pressure,  and  purifying  the  crude  glass  by  sublimation.  Realgar  is  a  ruby-red 
mass  of  a  conchoidal  fracture,  which,  if  mixed  with  saltpetre  and  ignited,  burns, 
giving  off  a  brilliant  white  light.  The  mixture  for  white  fire  consists  of  24  parts 
saltpetre,  7  sulphur,  and  2  realgar. 

Orpiment,  As,S3,  is  also  found  naturally,  and  is  obtained  artificially  (as  a  mixture 
of  As,S3  with  arsenious  acid)  by  melting  together  sulphur  with  arsenious  acid  or 
realgar,  or  by  the  distillation  of  a  corresponding  mixture  of  arsenical  and  sulphur 
pyrites.  It  forms  massive,  pale  orange,  transparent  lumps  (so-called  yellow  glass), 
which  always  contain  arsenious  acid  up  to  97  per  cent.,  so  that  the  yellow  arsenic 
.sulphide  obtained  in  the  dry  way  may  perhaps  be  regarded  as  an  arsenic  oxysulphide. 
In  the  wet  way  it  is  obtained  by  precipitating  a  hydrochloric  solution  of  arsenious 
acid  by  sulphuretted  hydrogen,  or  by  decomposing  sodium  sulpharseniate  (AsaS3NaS2, 
obtained  by  fusing  arsenious  acid  with  sulphur  and  sodium  carbonate)  with  dilute 
sulphuric  acid,  or  lastly,  by  boiling  a  solution  of  arsenious  acid  in  hydrochloric  acid 
with  sodium  thiosulphate.  In  the  last  manner  it  is  produced  of  an  especially  fine 
colour.  Orpiment  obtained  in  the  wet  way  is  used  in  oil-painting  as  a  yellow  pigment 
under  the  name  of  King's  yellow.  It  was  used  in  dyeing  for  the  reduction  of  indigo, 
and  it  serves  also,  under  the  name  of  rusma,  for  the  removal  of  superfluous  hair.  For 


*  Medlock  process. 


SECT. 


II.] 


MERCURY. 


207 


this  purpose  a  mixture  of  9  parts  of  lime  and  i  part  of  orpiment  is  made  up  into  a  paste 
with  water.  Calcium  hydrosulphate,  prepared  by  passing  sulphuretted  hydrogen  into 
cream  of  iime  until  it  takes  a  greyish-blue  colour,  is  now  used  in  preference. 

MERCURY. 

Occurrence. — Mercury  is  found  native,  but  chiefly  as  cinnabar,  HgS,  in  beds  and, 
veins  in  crystalline  slate  rocks,  in  transition  and  Flotz  formations,  and  is  sometimes 
found  in  secondary  deposits  in  loose,  rounded  fragments. 

The  chief  localities  are  Almaden,  or  Almadingas,  in  Spain  (Silurian),  where  it  was 
raised  in  antiquity,  and  Idria,  in  Carniola  (carboniferous).  Cinnabar  is  also  found  in 
the  Bavarian  Palatinate  near  Wolfstein  ;  on  the  Stahlberg,  the  Moschelandsberg,  and 
the  Potsberg,  near  Kusel ;  at  Olpe,  in  Westphalia ;  in  some  parts  of  Carinthia,  Eisenerz, 
in  Styria ;  Horzowitz,  in  Bohemia  ;  in  several  places  in  Hungary  and  Transylvania ;  at 
DalF  alta,  in  Yenetia ;  on  the  Ural ;  in  China  and  Japan ;  in  the  district  of  Sarawak, 
in  Borneo ;  in  Mexico ;  at  Huancavelica,  in  Peru ;  and  in  large  quantities  in  California, 
in  transition  formations.* 

An  impure  cinnabar,  mixed  with  earthy  and  bituminous  matter,  or  a  carboniferous 
shale,  rich  in  cinnabar  and  paraffine,  is  known  as  mercury-lime-ore,  and  is  peculiar  to 
Carniola.  A  mercurial  fahl- ore,  containing  from  2  to  15  per  cent,  of  mercury,  may  also 
be  mentioned. 

Production. — At  Idria  the  older  shaft-furnaces  are  connected  on  both  sides  with  a 
series  of   condensation   chambers.     The 
cinnabar  is  converted  by  the  action  of 
atmospheric  oxygen  into  sulphurous  acid 
and  metallic  mercury— 

HgS  4-  2O  =  2S02  +  Hg. 

At  the  works  in  Idria  there  was  used 
in  1884  as  fuel  partly  wood  and  partly 
lignite.  In  the  previous  year  there  were 
worked  up  49,384-1  tons  of  ore,  con- 
taining on  an  average  0*95  per  cent,  of 
mercury,  besides  1044*2  tons  of  furnace 
residues  produced  on  the  spot,  and  con- 
taining on  an  average  10-12  per  cent, 
of  mercury,  and  rubbish  from  the  foun- 
dations of  old  furnaces,  2968-3  tons, 
containing  0^51  per  cent,  of  mercury. 
There  were  produced  metallic  mercury 

4537-52  kilos.,  and  intermediate  products  (stupps)  98-15  tons,  containing  1053-2  kilos, 
of  mercury,  or  a  total  yield  of  5590-72  kilos.  Hence  the  average  proportion  of  mercury 
secured  was  94-22  per  cent. ;  if  we  omit  the  working  up  of  the  stupp  and  the  mercury 
extracted  from  it,  94-06  per  cent. ;  or  a  loss  of  metal,  in  round  numbers,  of  6  per  cent. 

The  arrangement  for  condensing  mercurial  fumes  introduced  at  Idria  in  1882 
consists  of  four  ranks  of  pipes,  which  are  formed  of  three  condenser-elements, 
A  (Fig.  196),  each  made  up  of  two  tubes,  a,  a  twin-tube,  6,  and  a  cut-off  portion,  c,  all 
fixed  vertically  upon  the  plates,  v ;  the  pipes,  a,  are  closed  with  lids,  d,  provided  with 
small  openings  for  cleaning.  The  plate  forms  a  part  of  the  supporting  surface  for  the 
tubes,  a,  formed  by  an  internal  circular  rib  of  b,  and  has  an  aperture  by  which  it  is 
possible  to  get  to  the  bottom  of  g,  the  box  for  receiving  the  stupp.  The  additional 

*  An  extensive  deposit  of  mercury  is  said  to  exist  in  the  Transvaal,  but  no  particulars  are  as 
yet  known. 


203 


CHEMICAL   TECHNOLOGY. 


[SECT.  ii. 


pieces  of  pipe,  h,  effect  the  communication  between  the  pipes  which  bring  and  which 
carry  off  the  furnace-gases.  All  the  cast-iron  pipes,  excepting  c,  and  the  boxes  for 
collecting  the  stupp,  are  lined  with  layers  of  cement-mortar  10  to  15  millimetres  in 
thickness,  which  has  proved  to  be  an  excellent  protection  against  the  action  of  acid 
vapours.  The  gases  enter  the  condenser  at  e,  descend  in  the  pipe,  a,  turn  into  the 
pipe,  a,  and  rise  in  the  second  pipe,  a,  in  order  to  traverse  a  similar  course  twice  in  the 
following  portions  of  the  condenser.  The  products  of  condensation  are  a  mixture  of 
finely  divided  mercury,  particles  of  unburiit  fuel,  undecomposed  hydrocarbons,  ore,  and 
ashes,  as  also  moisture  from  the  ore,  and  the  fuel.  The  condensed  steam-water, 
containing  fluctuating  quantities  of  soluble  mercurial  salts,  is  led  into  the  wooden 
chests,  k,  where  also  solid  matter  which  has  been  swept  over  may  be  deposited,  and 
then  into  large  cemented  sumps,  where  it  is  sprinkled,  in  order  to  precipitate  the  mercury 
from  its  salts,  with  a  lye  of  sodium  sulphide,  and  is  then  allowed  to  run  off.  The 
stupp  collecting  under  the  water  upon  the  sloping  bottom  of  the  chest,  g,  is  raked  upon 
the  plate,  //,  after  the  free  mercury  and  the  water  have  drained  off  into  dishes  or 
chests.  The  mercury  collecting  at  the  deepest  part  of  the  chest  runs  off  into  i.  The 
refrigeration  of  the  condenser  is  effected  by  water  conveyed  from  above,  and  allowed  to 
(low  down  in  a  thin,  uniform  layer  over  the  entire  surface  of  the  pipes,  a  and  b  ;  it 
then  collects  in  the  water-tight  cistern  formed  by  the  plate  nv,  and  escapes  through  a, 
lateral  channel  to  the  drains. 

Fig.  197. 


Fig.  198. 


At  the  Almaden  works  the  mercurial  vapours  are  condensed  in  aludels,  pear-shaped 
vessels  of  earthenware,  open  at  both  ends,  and  fixed  together  so  that,  as  shown  in 
Fig.  197,  the  thinner  end  of  one  fits  into  the  wider  end  of  the  other,  forming  long 
rows  after  the  joints  have  been  luted  together  with  clay  and  ashes.  The  cylindrical 
shaft- furnace,  A  (Fig.  198),  is  divided  into  two  compartments  by  a  perforated  vault. 
The  fire  is  made  in  the  lower  compartment  and  the  ores  are  placed  in  the  upper. 
Large  blocks  of  a  sandstone  containing  cinnabar  are  placed  at  the  bottom  (containing 
so  little  mercury  that  they  do  not  admit  of  mechanical  concentration),  and  upon  these 
are  placed  the  rich  ores.  The  vapours  pass  into  twelve  series  of  aludels.  Each  series 
is  20  to  22  metres  long  and  comprises  44  aludels.  Consequently,  there  are  in  each 
furnace  528  aludels.  The  series  lie  on  an  inclined  plane.  From  the  lowest  aludel  the 
condensed  mercury  flows  through  the  channel,  g,  into  the  stone  cisterns,  h.  The 
vapours  riot  condensed  in  the  aludels  are  received  in  chambers,  where  they  are 
completely  precipitated.  The  mercury  mixed  with  soot  is  purified  by  allowing  it  to 
flow  down  a  slightly  inclined  plane ;  the  mercury  flows  fairly  clean  into  a  sump ;  the 
sooty  dust  is  left  behind  and  is  distilled  again. 

The  furnaces  used  in  America  for  coarse-grained  ores  are  very  similar  to  those 
devised  at  Idria,  in  187 1 ,  by  A.  Exeli ;  they  are  iron-clad  shaft  furnaces.  The  shaft,  Ay 


SECT. 


II.] 


MERCURY. 


209- 


(Figs.  1 99  and  200)  with  twelve  view-holes,  s,  is  1-87  metre  in  diameter;  the  four  upper 
metres  of  the  height  are  cylindrical,  whilst  the  following  2-3  metres  have  the  form  of  a 
truncated  cone.  Beneath  the  three  fire-boxes,  f,  at  the  side,  are  the  exit  apertures,  «. 
The  round  part  of  the  furnace  is  clad  with  iron,  5  millimetres  in  thickness,  enclosing  a 


Fig.  199. 


Fig.  200. 


rough  wall  of  ordinary  bricks  0*12  metre  thick,  an 
inner  wall  0*33  metre  thick,  which,  as  well  as 
the  filling  between  the  two,  is  made  of  fire- 
proof stones.  The  angular  part  of  the  furnace 
is  armed  with  cast-iron  plates,  well  luted  and 
screwed  down ;  the  cast-iron  bottom  plate  slopes 
down  towards  the  middle.  The  arrangement 

;it  the  top  of  the  furnace  has  a  water  joint,  o'6  metre  ;  below  the  top  are  six 
apertures  at  equal  intervals  which  convey  the  gases  and  vapours  by  means  of  the  system 
of  pipes,  r  ;  the  gases  and  vapours  escape  into  a  large  cast-iron  main,  and  from  thence  to 
the  condensers.  In  this  system  of  pipes  almost  half  the  mercury  collected  is  condensed. 
The  furnace  shaft  is  filled  completely,  but  a  space  of  1*2  to  1*5  metre  in  height  is  left 
empty,  where  the  vapours  may  collect.  Every  two  hours  at  New-Almaden  a  fresh 
charge  of  720  kilos,  of  rich  ore  and  1-5  percent,  of  coke  is  introduced,  so  that  10  tons 

Fig.  20 1. 


are  worked  up  daily  with  an  expenditure  of  2*7  cubic  metres  wood  and  the  labour  of 
two  men  for  twelve  hours. 

The  Knox- furnace  (Figs.  201  to  203)  first  constructed  at  Knoxville,  Redington, 
has  been  introduced  at  Sulfurbank,  California,  and  Manhattan  works,  &c.  The  shaft- 
furnace,  A,  1 1 -7  metres  high,  and  lined  with  fire-bricks,  is  constructed  above  and 
telow  of  compact  masonry,  and  is  separated  in  its  upper  half  by  the  five  arches  of 
masonry,  a,  of  which  the  lowest  project  furthest  outwards  past  the  chambers, 
d  and  d,  which  are  closed  except  one  opening  each  (Fig.  203).  The  air-ducts,  e,  serve 

o 


2IO 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


to  cool  the  masonry,  which  is  2-5  metres  in  thickness.  The  sole  of  the  chambers,  d, 
is  protected  against  the  penetration  of  the  mercury  by  a  strong  iron  plate.  The  charge  of 
the  furnace  consists  of  two  to  three  parts  lumps  (from  0-06  to  0-2  in  size),  and  one  part 
smalls ;  if  the  smalls  are  plentiful  and  moist  the  yield  sinks  to  sixteen  and  even  twelve 
tons  daily.  The  shaft,  which  is  closed  at  top  with  a  bail-section,  B,  is  charged  with 
55  tons  of  ore,  and  at  the  sloping  mouth,  c,  one  ton  of  dead  ore  is  drawn  out  every 
hour,  whilst  fresh  ore  is  added  at  B.  Thus  the  charge  remains  in  the  furnace  for  three 

days.  The  grate, 
d,  lies  6 'i  metres 
below  the  top  of 
the  furnace ;  the 
fire  is  stirred  up 
every  half  -  hour. 
The  combustion 
gases  generated  in 
the  fire-box  enter 
the  ore  through  the 
openings  between 
the  arches,  a,  pass 
along  with  the  pro- 
ducts of  distillation 
between  the  oppo- 
site arches  into  the 
space,  d,  and  thence 
through  the  pipe, 
k,  into  the  cast-iron 
condensers,  /. 
These  are  rectan- 
gular chests  with  a 
sloping  bottom  2*4 
metres  long,  074 

Fig.  203.  metre  wide,  and  1-5  to  i-8 

metre  high,  connected 
with  each  other  by  the 
pipes,  k.  The  covering 
plates  are  turned  up  at 
the  edges  and  kept  cool 
with  water,  which  runs 
over  and  trickles  down 
the  sides.  The  condensed 
products  collect  in  the 
lowest  parts  of  the  bottom 
plate.  The  wooden  con- 
densers in  connection  are 

similarly  arranged.  The  condensed  products  collect  in  the  pans,  IT,  from  which  the 
mercury  is  baled  out  into  bottles.  The  acid  water  is  run  out  into  the  recipients,  P,  in 
which  a  little  mercury  deposits.  The  vapours  which  issue  from  the  furnace  are  very  hot, 
so  that  the  mercury  condenses  chiefly  in  the  middle  coolers.  From  the  last  condenser 
the  gases,  when  quite  cold,  are  driven  by  means  of  a  Roots'  blast,  Q  (four  of  which, 
along  with  the  water-pump,  S.  a  saw,  &c.,  are  driven  by  the  engine,  R\  into  the  wooden 
channels,  U,  of  o'6  by  075  metre  section.  After  running  89  metres  each,  two  of  them 
unite  into  a  larger  channe  of  i  '2  by  1*5  metre  section,  which  conveys  the  gases  for 


„  — '.*___* —      — i  PI — *    y 


SECT.    II.] 


MERCURY. 


211 


Fig.  204. 


350  metres  to  a  four-sided  wooden  scrubber  tower,  4-5  metres  high,  filled  with  pebbles, 
over  which  water  trickles.  A  furnace  works  up  daily  96  tons  of  ore,  and  uses  36  cubic 
metres  of  firewood. 

In  1883  California  yielded  46,725  bottles  of  mercury,  28,700  from  New  Almaden. 
Between  the  years  1850-1883  California  produced  1,357,403  bottles,  each  of  34*695 
kilos,  of  mercury,  Idria  only  272,834,  and  Spain  1,044,139  bottles,  each  of  34*507  kilos. 
The  price  of  mercury  in  1874  reached  a  maximum  of  125.  and  fell  in  1883  to  a 
minimum  of  35. ;  in  consequence,  in  March  1884,  22  of  the  27  furnaces  in  California 
were  out  of  work.  In  1886  California  yielded  only  29,981  bottles. 

At  Horzowitz  in  Bohemia  cinnabar  containing  clay  iron  ore  is  mixed  with  x  to  A  its 
weight  of  forge  scales  and  charged  in  a  bell-furnace  (Fig.  204)  upon  iron  plates  or  dishes 
b  &,  which  are  secured  to  an  iron  support  and  covered  with  an  iron  bell,  e,  dipping  into 
water.  The  bell  is  placed  in  a  fur- 
nace shaft  of  masonry  and  ignited  by 
means  of  a  coal  fire.  The  mercury 
descending  collects  in  d.  Each  bell, 
of  which  there  are  six  in  a  furnace, 
contains  25  kilos,  of  ore  and  12  kilos, 
of  anvil  scales ;  from  30  to  36  hours 
are  required  for  the  process. 

The  mines  at  Rosswalde  near 
Stahlberg,  in  the  Palatinate  (opened 
in  1410),  those  at  Landsberg,  Pots- 
berg,  and  Wolfstein  contain  cinnabar 
diffused  through  sandstone.  The  pro- 
portion of  mercury  is  generally  0*005 
-and  sometimes  o-oi  per  cent.  To  be 
worth  extraction,  it  must  form  ^i^ 
part  of  the  ore.  The  decomposition 
of  the  cinnabar  is  conducted  in  iron 
retorts,  of  which  30  to  50  are  placed 
in  a  galley-furnace.  Lime  is  added 
to  the  ore  when  mercurial  fumes  are 
evolved,  and  there  remains  a  mixture 
of  calcium  sulphide,  thiosulphate,  and 
sulphate. 

The  mercury  works  at  Siele,  near  Castellazara,  operate  upon  a  very  rich  ore,  partly 
in  Hahner  shaft-furnaces  and  partly  in  muffle-furnaces.  The  neighbouring  works  at 
•Cornachino  has  two  furnaces,  each  with  three  muffles  of  cast  iron.  Each  is  27  metres 
long,  64  centimetres  wide,  and  32  centimetres  in  height.  They  are  charged  with  140 
kilos,  of  ore  and  84  kilos,  of  lime,  both  broken  up  and  well  mixed.  This  quantity  is 
distilled  off  in  six  hours,  so  that  the  muffles  are  charged  four  times  daily. 

Details  concerning  the  Chinese  mercury  mines  are  wanting.  In  1782  a  consider- 
able quantity  of  mercury  was  exported  from  thence  to  South  America. 

Properties. — Mercury  has  a  strong  metallic  lustre  and  a  white  colour,  with  a  faint 
blueish  cast.  At  common  temperatures  it  is  liquid ;  it  solidifies  and  becomes  malleable 
at  ~  35°-5  an(l  boils  at  360° .  Its  sp.  gr.  is  1 3-5.  It  combines  readily  with  lead,  bismuth, 
zinc,  tin,  silver,  and  gold,  forming  amalgams  ;  less  readily  with  copper,  and  not  at  all, 
under  ordinary  circumstances,  with  iron,  nickel,  cobalt,  and  platinum.  On  these 
properties  depend  its  applications  for  the  separation  of  gold  and  silver  from  ores 
(amalgamation) ;  amalgams  are  used  for  coating  mirrors,  for  fire  gilding,  and  for  the 
friction-cushions  of  electrical  machines. 


212  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

Mercury  is  used  in  various  scientific  and  technical  apparatus,  barometers,  thermo- 
meters, levels,  Sprengel  pumps.  &c.  For  directions  for  the  detection  of  mercury  in 
minerals,  and  for  the  assay  of  mercurial  ores,  see  Select  Methods  in  Chemical  Analysis, 
by  W.  Crookes,  F.R.S.,  pp.  292,  293,  and  294. 

ZINC. 

Occurrence.— Zinc  never  occurs  in  the  metallic  state,  but  combined  with  sulphur  as 
blende  ZnS,  and  sometimes  with  small  quantities  of  indium  and  gallium ;  it  is  found 
oxidised  as  calamine  or  zinc-spar,  ZnC03,  and  as  electro-calamine,  zinc  silicate, 
Zn2Si04,H2O.  It  is  also  found  as  willemite,  an  anhydrous  zinc  silicate,  as  red  zinc  ore, 
or  zinc  oxide,  coloured  reddish  by  oxides  of  iron  and  manganese  (spartalite),  as 
franklinite,  Fe2Zri04,  as  gahnite,  Al2ZnO4  and  in  some  fahl-ores. 

The  distillation  of  zinc  from  calamine  and  roasted  blende  in  muffles  is  practised  in 
Upper  Silesia,  at  Stolberg  near  Aachen,  in  Westphalia,  &c.  The  muffles  are  made  upon 

moulds,  and  consist  of  fire  clay 

Fig.  205.  Fig.  206.  and  fragments  of  old  muffles. 

The  front  side  of  a  muffle  has 
two  openings ;  the  lower  is 
closed  with  a  plate,  a  (Figs.  205 
and  206),  which  is  removed 
when  the  residues  of  the  pro- 
cess have  to  be  drawn  out. 

Above,  a  tube  with  an  elbow  joint  is  introduced,  with  an  aperture  which  is  closed  at  c, 
during  distillation,  and  through  which  the  charge  is  introduced.  The  liquid  zinc  flows 
out  of  d  into  the  space  below.  The  muffles  are  placed  upon  banks  on  the  vaulted  zinc 
furnace  on  both  sides  of  a  long  fire  grate,  so  that  they  are  wrapped  in  the  flame  as  much 
as  possible.  The  zinc  oxide  formed  at  the  beginning  of  the  distillation  contains  nearly  all 
the  cadmium  oxide,  and  serves  for  the  preparation  of  cadmium.  At  the  outset,  the  con- 
densers are  so  cool  that  the  vapours  of  zinc  condense  in  them,  not  to  a  liquid,  but  to  a 
solid,  finely  divided  metal  known  as  zinc  powder.  It  contains  about  98  per  cent,  of  zinc, 
and  is  used  as  a  powerful  reducing  agent,  especially  in  calico  printing.  The  zinc  drops, 
afterwards  formed  in  the  old  furnaces  (drop  zinc),  are  made  to  coalesce  by  remelting. 
In  the  recent  furnaces  the  zinc  is  collected  as  a  liquid  in  clay  receivers  and  is  taken  out 
with  iron  ladles  and  poured  into  moulds. 

Recently,  gas-firing  on  the  principle  of  Siemens  or  of  Boetius  has  almost  every- 
where superseded  grate-fires.  In  the  latter  case  the  furnace  has  two  generators,  a 
(Figs.  207  and  208),  so  that  the  fire-gases  from  each  generator  pass  through  half  the 
furnace  and  then  down  in  the  middle  through  a  common  main  shaft,  or  into  the 
flues,  c,  placed  between  the  muffles,  and  then  through  a  channel  connecting  the  latter 
into  the  main,  d.  The  air  required  for  gasification  streams  through  the  draught  holes,  b, 
into  the  furnace ;  the  air  for  combustion  is  introduced  through  channels  left  in  the 
walls  of  the  furnace.  The  greater  part  of  them  are  led  through  the  furnace-walls  in 
the  reserved  channels,  n,  in  such  a  manner  that  this  air  meets  the  combustion  gases, 
which  have  been  half  burnt  in  the  combustion  shaft,  and  so  burns  it  gradually  and  com- 
pletly,  in  order  to  produce  a  uniform  heat.  In  order  to  convey  away  the  vapours,  which 
greatly  annoy  the  workmen,  the  arch  aoove  the  fore-cupels  is  provided  with  an  exit 
slit,  s,  opening  into  the  channel,  k,  leading  into  a  small  chimney. 

On  the  Belgian  system  the  distillation  of  the  zinc  is  effected  in  stoneware  pipes 
which  lie  in  rows,  over  and  alongside  each  other,  slightly  sloping.  The  pipes  (Fig.  209) 
are  cylindrical,  generally  i  metre  long,  18  centimetres  in  internal  diameter,  and  closed 
at  one  end.  The  front  opening  of  the  pipes  touches  the  front  wall  of  the  furnace  and 
serves  for  introducing  the  charge,  drawing  off  the  zinc  vapours,  and  removing  the 


SECT.    II.] 


ZINC. 


213 


residues.  To  each  of  these  pipes  there  is  attached  a  tube  (Fig.  210),  25  centimetres  in 
length,  and  to  it  again  a  tube  of  sheet  iron  (Fig.  211)  20  centimetres  long,  or  a  larger 
sheet  iron  receiver  (coated  within  with  clay),  in  which  the  zinc  collects.  Fig.  212 
shows  the  section  of  a  Belgian  zinc  furnace.  The  distilling  tubes  lie  in  ranks  above 
each  other,  slightly  inclining.  For  this  purpose  there  are  left  steps  in  the  back  wall,  b  d, 


Explanation  of  Terms. 
Schnitt  I-II.    =    Section  I.  II. 


Fig.  207. 


Fig.  209. 


Fig.  210. 


Fig.  211. 


Fig.  212. 


of  the  furnace,  upon  which  the  closed  ends  of  the  pipes  rest.  Whilst  the  Belgian  fur- 
naces formerly  worked  up  daily  200  kilos,  of  ore  in  30  tubes,  those  of  recent  make,  with 
70  tubes,  use  up  1200  kilos. 

According  to  Liebig,  the  zinc  works  of  the  Markisch-Westphalian  Mining  Union  at 
Letmathe  have  in  action  twenty-six  zinc  furnaces,  with  seventy-six  retorts  each. 
Each  furnace  works  up  daily  1600  kilos,  of  ore  (|  bleude  and  ^  calamine),  containing 


214 


CHEMICAL  TECHNOLOGY. 


[SECT.  n. 


on  an  average  45  per  cent,  of  zinc,  and  produces  580  kilos,  crude  zinc.  The  con- 
sumption of  fuel  is  about  23  hectolitres  heating  coal  and  8  hectolitres  reducing-coal. 
Three  retorts  are  charged  daily  in  each  furnace. 

The  English  method  of  obtaining  zinc  (Wales,  Sheffield,  Birmingham,  Bristol)  is 
the  so-called  downward  distillation  in  crucibles.  The  reducing  furnaces  are  so  con- 
structed that  six  to  eight  crucibles,  c  (Fig.  213),  can  be  placed  upon  the  hearth.  The 
crucibles  are  made  of  fire-clay  and  are  i|  metre  high.  In  the  middle  of  the  bottom 
is  a  hole  through  which  the  zinc  fumes  pass  into  the  condensing  tubes.  The  charge  is 
introduced  into  the  crucibles  through  a  hole  in  the  lid,  which  is  left  open  for  about  two 
hours  after  charging,  until  a  blue  flame  shows  that  reduction  is  beginning.  The 
opening  in  the  cover  is  then  closed  with  a  plate  of  fire-clay,  the  condensing  pipe  is 
joined  to  the  opening  in  the  bottom  of  the  crucible,  and  below  it  is  placed  the  receiver 
for  the  zinc,  often  filled  with  water,  to  prevent  the  zinc  from  spirting  as  it  falls.  The 
distilling  zinc  collects  in  drops  and  in  fine  powder  mixed  with  zinc  oxide,  and  is 
re-melted  in  iron  vessels.  The  oxide  which  separates  on  the  surface  is  skimmed  off 
and  the  zinc  is  run  into  moulds.  This  process,  especially 
at  Swansea,  has  been  latterly  superseded  by  Belgian  fur- 
naces. 

The  production  of  zinc  in  blast  furnaces  has  been  at- 
tempted without  success,  as  the  zinc  is  re-oxidised  to  zinc 
oxide  by  the  carbon  dioxide. 

From  the  receivers  of  the  zinc  distillation  furnaces  there 
escapes,  as  the  author  has  shown,  carbon  monoxide  nearly  in 
a  state  of  purity.  This  can  be  explained  if  the  solid  carbon 
forms  only  carbon  monoxide—- 


-  85,000        +  29,000  =    -  56,000  heat  units, 
or  if  the  carbon  monoxide  originally  formed  is  reduced  again 
(C02  +  C  —  2  CO),  so  that  the  original  process  would  be — 
2ZnO  +  C  =  Zn2  +  CO2 

—   170,000         +  97,000  =    —  73,000  heat  units. 
The  latter  process  takes  up  decidedly  more  heat  than  the 
former,  and  is  therefore  very  improbable. 

The  reduction  of  zinc  is  hence  effected  chiefly  or  exclusively  by  solid  carbon. 
For  the  production  of  65  kilos,  of  zinc  there  are  required  theoretically  only  56,000 
heat  units,  or  860  heat  units  per  kilo.,  corresponding  to  0-12  kilo,  of  coal.     In  practice 
twenty  times  the  quantity  of  coal  is  required,  so  that  the  utilisation  of  heat  is  still  very 
imperfect. 

Production  of  Zinc  by  Electricity. — L.  Letrange  roasts  blende  at  a  low  temperature 
to  convert  it  into  zinc  sulphate.  The  roasted  ores  are  lixiviated  in  walled  tanks,  coated 
with  asphalte,  A  (Figs.  214  and  215),  connected  by  pipes.  The  residues  are  worked  up 
for  lead  and  silver  if  present,  the  solution  of  zinc  sulphate  is  collected  in  the  cistern,  B, 
and  freed,  if  necessary,  from  iron,  &c.,  and  conveyed  by  the  pumps,  P,  and  the  pipes,  d, 
to  the  precipitating  tank,  C.  The  kathodes,  b,  consists  of  thin  sheet  zinc,  but  polished 
copper  or  brass  may  be  used,  from  which  the  deposited  zinc  is  easily  removed.  The 
anodes,  c,  are  of  carbon,  platinum,  or  lead.  The  lye  rendered  acid  by  the  elimination 
of  the  zinc  flows  away  continuously  through  pipes,  o,  in  order  to  be  used  for  dissolving 
fresh  masses  containing  zinc  oxide.  If  very  pure  calamine  or  zinc-ash  is  to  be  worked 
up,  it  is  mixed  with  carbon  and  suspended  in  the  bath  in  a  porous  vessel  as  an  anode. 

Letrange  fitted  up  such  an  installation  for  working  up  zinc-ash  at  his  rolling  milk 
at  St.  Denis ;  a  second  installation  for  blende  containing  lead  and  silver  has  been 
erected  in  the  Department  du  Var.  When  a  stratum  of  metallic  zinc,  4  to  5  millimetres. 


SECT.   II.] 


ZINC. 


215 


in  thickness  has  been  deposited  upon  the  brass  sheets  serving  as  negative  poles,  a  work- 
man takes  out  the  sheets  and  removes  with  a  knife  the  zinc  plate,  which  strips  off  like 
a  piece  of  leather.  The  metal  thus  obtained  is  re-melted.  The  process  devised  by 
Letrange  of  converting  the  ores  into  sulphates  by  treatment  with  sulphurous  acid  and 
precipitating  them  electrolytically  would  render  it  possible  to  utilise  large  quantities  of 
poor  calamines. 

According  to  Kosmann,  there  are  obtained  at  St.  Denis,  in  regular  work  from  roasted 
blende  with  i  horse  power,  8  kilos,  of  zinc  every  12  houra  ;  consequently,  with  1-4  kilo, 
coal  per  hour  and  horse  power,  for  i  kilo,  zinc,  2-i  kilos,  coal;  whilst  in  the  zinc  works 
of  Upper  Silesia,  there  are  consumed  for  i  kilo,  zinc,  2  kilos,  coal  for  reduction,  and 
9-8  kilos,  for  heating.  These  statements  appear  doubtful,  the  assertion  that  0*67  kilo, 
of  zinc  is  obtained  hourly  per  horse  power  can  only  hold  good  in  cases  of  soluble  anodes. 
For  insoluble  anodes  the  separation  of  65  kilos,  of  zinc  from  the  solution  requires 
170,000  heat  units,  consequently  per  kilo.  2615  heat  units.  Or  as  i  horse-power  hourly 
(75  +  60  +  60):  428  =  631  heat-units,  there  are  required  at  least  4  horse-power,  or 
7  horse-power  (equivalent  to  10  kilos,  of  coal)  if  only  50  to  60  per  cent,  of  the  power 
of  the  machine  is  utilised.  It  must  also  be  remembered  that  with  feeble  currents 
hydrogen  is  always  evolved. 

Figs.  214  and  215. 


In  a  solution  of  zinc  sulphate  of  specific  gravity  1*38  this  escape  of  gas  ceases  if 
about  0*5  gramme  zinc  are  deposited  per  second  on  i  square  metre  of  polar  surface 
(corresponding  to  16  amperes).  For  10  per  cent,  solutions  a  density  of  current  of  20-30 
amperes  is  required  per  square  metre. 

Kiliani  treats  calamine,  &c.,  with  a  solution  of  ammonia  holding  ammonium 
carbonate  in  solution.  The  liquid  is  led  into  decomposition  troughs,  the  zinc  is  deposited 
at  the  kathode  and  oxygen  is  evolved  at  the  anode.  The  kathodes  are  of  zinc  or  brass ; 
the  anodes  of  sheet  iron,  The  lye  as  it  flows  off  is  conveyed  back  into  the  closed 
dissolving  tanks. 

If  soluble  anodes  are  used,  much  less  work  is  required  from  the  current.  If  when 
decomposing  a  solution  of  zinc  sulphate  the  anode  consists  of  pure  zinc,  there  are  used 
at  the  negative  poles  for  each  molecule  of  ZnS04  106,090  heat-units  chemical  work  ; 
but  at  the  anode,  exactly  the  same  quantity  is  again  developed,  so  that  the  current  has 
merely  to  undertake  the  mechanical  work  of  conveying  the  ions  from  one  pole  to  the 
other.  This  mechanical  work  is  expressed  in  the  tension,  or  the  development  of  heat. 
Jahn  has  shown  that  notwithstanding  the  differences  of  the  chemical  work  to  be  per- 


2i6  CHEMICAL  TECHNOLOGY.  [SECT.  n. 

formed  by  the  current,  the  total  loss  of  energy  of  the  chain,  e.g.,  by  the  oxide,  zinc 
sulphate,  and  copper  sulphate  is  the  same,  as  in  the  separation  of  i  kilo,  copper  m 
which  1807  heat-units  are  evolved,  and  of  i  kilo,  zinc,  977  heat-units,  corresponding 
to: — 

Free  Chem. 

heat.  work. 

ZnS04        .        .     63,210  +   106,090  =   169,306  heat-units. 

CuSO4        .        .  114,744  +     59,96o  =   170,704        >i 

According  to  the  process  of  Bias  and  Miest  the  bath  for  working  up  blende  consists 
of  zinc  sulphate  ZnS04  +  ZnS  =  Zn  +  S  +  ZnS04.  As  much  zinc  as  is  deposited  on 
the  kathode  is  dissolved  at  the  anode,  whilst  the  corresponding  quantity  of  sulphur 
is  separated  out  and  can  be  freed  from  the  gangue  found  in  the  sediment.  The  blende 
does  not  require  to  be  roasted  and  the  sulphate  is  obtained  free.  Less  work  is 
required  from  the  current  than  in  former  methods.  Since,  then,  only  the  decom- 
position of  the  zinc  sulphide  is  in  question,  as 

Zn  |  S04  -»  Zn  |  S 

-  106,090  +106,090  -  41,326  =   -  41,326  heat-units. 

Hence,  there  is  needed  for  i  kilo,  of  zinc  41,326  :  65-5  =  63-1  heat  units,  whilst  for 
decomposing  zinc  chloride  and  sulphate  more  than  double  the  chemical  work  is  required. 
Pure  blende  is  a  bad  conductor ;  the  ordinary  kind  containing  iron  is  better. 

Luckow  suspends  in  the  bath  a  mixture  of  blende  and  coke,  packed  in  boxes,  but 
hitherto  with  little  success. 

Siemens  and  Halske  recommend  their  process  for  working  up  blende.  There  are 
formed  in  the  electrolytic  decomposition  cells  zinc  and  ferric  sulphide,  according  to  the 
equation :  Zn  SO4  +  2Fe  S04  =  Zn  +  Fe2  (S04)3.  The  ferric  sulphate  thus  formed  has 
the  property  of  dissolving  zinc  from  sulphuretted  zinc  ores  which  have  been  slightly 
roasted,  according  to  the  equation : 

ZnS  +  Fe2(S04)3  =  ZnS04  +  2FeS04  +  S. 

A  comparison  of  this  and  the  former  equation  shows  that  after  lixiviating  slightly 
roasted  zinc  sulphide  ores  with  the  oxidised  electrolytic  liquid,  the  proportion  of  zinc 
and  iron  becomes  as  great  as  it  was  before  electrolysis.  Indeed,  in  this  zinc  pro- 
cess the  necessary  difference  of  potential  between  the  anode  and  the  kathode  of  the 
electrolytic  bath  is  about  twice  as  great  as  in  the  copper  process  previously  de- 
scribed. 

Properties. — Zinc  is  of  a  grey- white,  slightly  bluish  colour,  generally  of  a  foliaceous 
crystalline,  but  sometimes  very  finely  foliated,  texture,  with  a  strong  metallic  lustre 
on  its  surface.  Colour,  texture,  and  lustre  vary  in  different  directions,  according  as 
the  zinc  is  more  or  less  contaminated  with  other  metals.  According  to  Bolley,  zinc,  cast 
near  its  melting  point  and  cooled  rapidly,  has  the  sp.  gr.  7-178  ;  if  slowly  cooled,  7*145  : 
that  cast  at  a  red  heat,  if  cooled  rapidly,  7,109  ;  if  cooled  slowly  7-120.  By  hammering 
and  rolling,  the  sp.  gr.  may  be  raised  to  7-2,  or  even  7-3.  Pure  zinc  is  slightly  extensile, 
even  at  common  temperatures,  and  can  be  rolled  out  to  thin  sheets  without  cracking  at 
the  edges.  This  property  is  lost  if  it  is  even  slightly  contaminated  with  other  metals,  so 
that  ordinary  zinc  breaks  under  the  hammer.  It  distils  in  a  vacuum  at  184°.  At  about 
500°  it  ignites  in  the  air,  and  burns  with  a  pale  green  luminous  flame  to  zinc  oxide  (zinc 
white).  When  heated,  zinc  expands  considerably,  more  than  any  other  technical  metal 
(from  o°  to  100°)  by  ^-^  in  length ;  if  hammered,  ^^.  When  melted,  zinc  on  solidifying 
contracts.  In  casting  zinc,  the  iron  moulds  must  be  strongly  heated,  and  the  tempera- 
ture of  the  melted  zinc  must  not  be  raised  too  high,  that  the  solidification  may  take  place 
gradually  and  at  the  smallest  possible  difference  of  temperature.  The  expansibility  of 
zinc  reaches  its  maximum  between  100°  and  150°,  and  even  if  contaminated  with  other 
metals  it  can  be  extended  at  this  temperature.  Hence  it  is  worked  out  to  sheets  with 


SECT,  ii.]  CADMIUM.  217 

hot  rollers.  Above  150°  the  flexibility  of  zinc  decreases,  and  at  200°  it  is  so  brittle 
that  it  may  beaten  to  powder.  Zinc  is  oxidised  by  superheated  steam  : 

H2O    +   Zn   =   ZnO   +    Ha 

a  property  which  is  used  in  separating  lead  from  zinc.  In  moist  air  zinc  becomes 
coated  with  a  film  of  oxide,  which  protects  the  subjacent  parts  from  further  oxidation. 
On  account  of  its  ready  oxidation  by  water  and  acids,  it  is  unsuitable  for  milk-pails  and 
culinary  utensils.  An  addition  of  0*5  per  cent  of  lead  makes  zinc  more  flexible,  and 
such  small  proportions  are  therefore  commonly  added  to  zinc  intended  for  rolling.  But 
for  zinc  which  is  to  be  used  for  brass,  even  0-25  per  cent,  of  lead  is  very  injurious,  as  it 
seriously  lessens  the  strength  of  the  brass.  A  large  proportion  of  iron  renders  zinc 
brittle.  For  eliminating  arsenic,  L'Hote  melts  zinc  with  i  to  i|  per  cent,  of  anhy- 
drous magnesium  chloride.  Commercial  zinc  can  be  freed  from  the  greater  part 
of  foreign  metals  by  repeated  fractional  distillation,  keeping  apart  the  portion  which 
passes  over  first,  and  leaving  the  residue  unvolatised.  Traces  of  gallium  and  indium 
are  sometimes  found  in  the  zinc  of  commerce. 

Zinc  from  the  Georg  Works  of  the  Silesian  Association  (I.),  the  brand  CH  of  the 
same  company  (II.),  from  Giesche's  successors  (III.),  and  of  the  Furnace  Sagan  (IV.),  in 
1885,  contained,  according  to  Schneider  and  Peterson,  in  100  parts  : 

I.  II.  III.  IV. 

Pb  .  .  1-4483  ...  17772           ...  1-1921  ...  0-633 

Fe  .  .  0-0280  ...  0-0280            ...  0-0238  ...  0-032 

Cd  .  .  0-0245  ...                                 ...  ...  0-054 

Cu  .  .  O'ooo2  ...                                   ...  O'ooo2  ...  trace 

Ag  .  .  0-0017  ...  trace             ...  0*0007  •••  trace 

As  .  .  trace 

Sb  —  ...  trace              ...  trace 

Bi  .  .  —  ...                                   ...  trace 

S  .  .  trace  ...  0*0020            ...  trace  ...  trace 

A  method  for  determining  the  value  of  zinc  powder,  which  is  often  contaminated 
with  zinc  oxide,  is  to  be  found  in  Select  Methods  in  Chemical  Analysis,  by  W.  Crookes, 
F.E.S.,  2nd  edition,  p.  121. 

Uses. — Zinc  is  applied  in  sheets  for  roofing,  for  gutters  and  spouts,  for  plates 
and  cylinders  in  galvanic  batteries ;  in  alloys  (brass,  bronze,  false  gold-leaf) ;  for  de- 
silvering  work-lead,  for  generating  hydrogen  gas  along  with  sulphuric  or  hydro- 
chloric acid,  for  preparing  zinc  sulphide,  zinc  white,  &c.  Zinc  precipitates  copper, 
silver,  lead,  &c.,  from  their  solutions.  If  zinc  and  iron  are  placed  in  contact,  the  latter 
metal  is  protected  from  oxidation.  Zinc  is  much  used  for  castings,  in  place  of  bronze, 
cast-iron,  and  even  of  wrought  stone  and  wood. 

From  1860  to  1884  the  total  production  of  zinc  in  Europe  has  increased  from 
97,896  to  257,767  tons.  In  1884  America  furnished  23,240  tons  of  zinc. 

CADMIUM. 

Cadmium  almost  constantly  accompanies  zinc  in  its  ores,  especially  in  the  Silesian 
calamine,  and  to  a  less  extent  in  blende. 

In  some  of  its  properties  cadmium  is  intermediate  between  tin  and  zinc ;  it  is  tin- 
white,  very  brilliant,  malleable  and  ductile,  and  gradually  loses  its  lustre  on  exposure  to 
the  air.  It  has  the  sp.  gr.  8-6  ;  it  melts  at  360°,  boils  at  860°  (Deville  and  Troost), 
or  according  to  Becquerel  at  746-2°,  and  can  be  easily  distilled.  It  is  met  with  in  trade 
in  rods  weighing  from  60-90  grammes.  Silesian  calamine  contains  as  much  as  5  per 
cent. ;  calamine  from  Wiesloch  more  than  2  per  cent.;  blende  from  the  Harz  0-35  to  079; 
that  from  Przibram  1.78  per  cent.,  that  from  Eaton  in  North  America  3.2  per  cent.  The 
cadmium  of  these  ores  is  concentrated  in  the  brownish  smoke  which  appears  at  the 


2l8 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


beginning  of  the  distillation  of  zinc.  This  fume,  consisting  of  metallic  zinc,  zinc  car- 
bonate and  cadmium,  serves  as  the  crude  material  for  the  preparation  of  cadmium.  It 
is  reduced  by  means  of  wood  charcoal  in  small  cylindrical  retorts  of  cast-iron  provided 
with  conical  receivers  of  sheet-iron.  The  metal  found  in  these  receivers  is  sold  in  the 
shape  of  rods  of  the  thickness  of  a  finger.  Cadmium  may  also  be  obtained  from  cad- 
miferous  zinc  in  the  wet  way  by  treatment  with  dilute  hydrochloric  acid.  The  zinc  dis- 
solves in  the  acid,  and  the  cadmium  is  precipitated  so  long  as  zinc  is  present  in  excess. 
The  residue  (which  also  contains  any  lead  present)  is  concentrated  as  far  as  possible 
and  the  cadmium  is  finally  separated  by  distillation. 

Silesia  produces  yearly  about  2000  kilos,  of  cadmium. 

If  alloyed  with  lead,  tin  and  bismuth  it  forms  Wood's  metal.  An  alloy  of  10  parts 
cadmium,  13*5  tin,  49^8  bismuth,  and  26*7  lead  melts  at  70°.  The  only  preparation  of 
cadmium  in  use  is  the  sulphide,  CdS,  a  splendid  and  permanent  yellow  pigment  (Jaune 
brilliant)  used  by  artists.  It  serves  also  for  giving  a  bright  yellow  colour  to  toilet 
soaps  and  for  producing  a  blue  colour  in  fireworks.  It  is  best  obtained  by  precipi- 
tating a  solution  of  cadmium  sulphate  with  sodium  sulphide,  washing,  pressing  and 
drying  the  precipitate. 

For  the  detection  of  cadmium  in  ores  and  alloys  and  for  its  determination,  the 
reader  is  referred  to  Select  Methods  in  Chemical  Analysis,  by  W.  Crookes,  F.R.S.,  2nd 
edition,  pp.  331-333. 

POTASSIUM   AND   SODIUM. 

The  production  of  the  alkali  metals  differs  from  that  of  zinc  only  by  the  greater 
care  required  to  preserve  the  metal  from  contact  with  the  oxygen  of  the  atmosphere. 
For  the  manufacture  of  sodium,  sodium  carbonate  is  ignited  with  carbon  : 


—  273>o°°  +  87,000  =  —  186,000  heat-units. 

The  separation  of  one  kilo,  of  sodium  requires,  therefore,  4050  heat-units,  decidedly 

more  than  in  the  corresponding  reduction 

Fig.  216.  of  metallic  zinc  from  its  oxide.      With 

potassium  the  case  is  similar  : 


—  281,000  +87,000  = 

-  144,000  heat  units. 
For  manufacturing  sodium  30  kilos,  of 
dry  sodium  carbonate,  13  kilos,  charcoal 
and  5  kilos,  chalk  are  intimately  mixed 
and  placed  in  iron  tubes,  A  (Fig  216),  1-2 
metre  long  and  0*15  metre  in  diameter. 
The  front  cover  supports  an  iron  escape- 
tube  leading  to  the  flat  iron  receiver,  v. 

For  protection  against  the  destructive  action  of  the  fire  the  tube  A  is  usually  encased 
in  a  wider  fire-clay  pipe.  On  heating  to  whiteness  there  escapes  first  carbonic  oxide, 
then  sodium,  which  becomes  liquefied  in  the  receiver  and  falls  into  an  iron  vessel  filled 
with  mineral  oil  (free  from  oxygen). 

In  this  process  there  is  obtained  only  about  40  per  cent,  of  the  theoretical  yield, 
since  a  part  of  the  sodium  is  burnt  and  a  large  part  escapes  reduction  on  account  of 
the  imperfect  mixture. 

Mactear  gives  the  following  estimate  of  cost  for  i  kilo,  sodium,  1887  :  — 


SECT.   II.] 


POTASSIUM   AND   SODIUM. 

Wear  and  tear  of  furnace,  &c 5-3  shillings 

Loss  of  materials 27 

Labour       .         .         .         .         .         .         .         .2-2 

Fuel  i -I 


219 


11-3 


The  recent  proposal  of  Thompson,  therefore,  demands  attention ;  4  parts  of  dry 
sodium  carbonate  and  3  parts  of  tar  are  to  be  slowly  heated  to  dull  redness,  the 
pulverised  melt  is  placed  in  a  box  of  sheet-iron  b  (Figs.  217  and  218),  10  centimetres  in 

Fig.  217. 


depth,  and  provided  with  a  spout. 
This  is  then  placed  in  a  fire-clay  gas 
retort  (previously  heated  to  full  red- 
ness) in  such  a  manner  that  its  spout 
is  close  to  the  lid  of  the  retort  c, 
which  is  then  secured  air-tight.  Be- 
hind the  lid  the  retort  is  freely  con- 
nected by  the  aperture  e  with  the 
chamber  g,  which  can  be  closed  air- 
tight by  means  of  the  door  f.  In 

the  chamber  a  receiver  g  is  placed,  below  the  spout  of  the  box  6.  From  the  chamber 
g  a  tube  h  passes  outwards,  and  gives  free  escape  to  the  carbon  monoxide  which  is 
formed.  The  extinction  of  the  flame  of  this  gas  shows  the  end  of  the  process.  The 
metal  flows  into  the  receiver.  It  is  taken  out  as  soon  as  the  flame  of  carbonic  oxide  is 
extinct,  and  a  fresh  vessel  is  introduced.  The  box  b  is  then  removed  and  a  freshly 
charged  box  is  put  in  its  place. 

Whilst  the  reduction  is  thus  conducted  the  melt  is  prepared  for  further  operations, 
the  mixture  of  carbonate  and  tar  being  put  in  the  iron  pots  A,  through  the  apertures 
B,  which  can  be  closed  with  fireproof  plates.  These  pots  stand  in  the  escape-flue  for 
the  combustion  gases — which  is  enlarged  at  this  point  for  the  purpose — and  thus  the 
heat  is  utilised  for  preparing  the  melt. 

Castner  reduces  sodium  hydrate  with  so-called  iron  carbide,  FeC2,  obtained  by 
heating  ferric  oxide  with  tar.  On  heating  10  kilos,  caustic  soda  and  2  kilos,  carbide  the 
decomposition  is  said  to  be  effected  as  follows  : 

4NaOH  +  FeC2  -  Na2CO3  +  Fe  +  2H2  4-  CO  +  Na,. 

The  thermic  relations  would  be : 


For  sodium  hydrate  4  x  102,000= 
,,  ,,  carbonate  .  . 
„  carbon  monoxide  .  . 


Heat-units. 
-  408,000 
+  273,000 
+  29,000 


—  106,000  heat-units. 
This  would  be  decidedly  more  favourable  than  the  old  process ;  it  must  be  con- 


220  CHEMICAL  TECHNOLOGY.  [SECT.  u. 

sidered  that  the  heat  liberated  in  the  decomposition  of  FeC,  comes  in  addition ;  its 
amount  is  not  yet  known. 

According  to  Mactear,  the  mixture  of  sodium  iiydrate  and  iron  carbide  is  placed  in 
cast-steel  crucibles  in  a  furnace  which  is  first  gently  heated  for  30  minutes.  The  mass 
melts,  and  much  hydrogen  escapes  in  bubbles,  whilst  the  carbide  remains  suspended  in 
the  melted  soda.  The  crucible  with  its  contents — now  in  tranquil  flux — is  lifted  up  and 
introduced  into  the  heating-chamber  of  the  main  distillatory  furnace.  The  cover  of 
the  crucible,  which  always  remains  in  the  furnace,  has  a  convex  border  which  fits  into  a 
groove  in  the  edge  of  the  crucible.  From  the  lid  a  bent  tube  passes  to  the  condensing 
apparatus,  which  has  at  its  hinder  end  a  small  escape  for  the  hydrogen  evolved.  It  is 
also  provided  with  a  rod  for  preventing  any  obstruction  from  being  formed  in  the  tube 
during  the  distillation. 

The  gas  given  off  at  the  beginning  of  the  process  is  pure  hydrogen.  A  sample 
drawn  shortly  before  the  end  of  the  process  contained  95  hydrogen  and  5  carbon 
monoxide  (which  does  not  agree  well  with  the  above  formula).  A  small  excess  of 
carbide  induces  the  formation  of  a  little  sodium  peroxide  in  the  residue.  The  quantity 
of  carbon  monoxide  formed  is  so  little  that  it  does  not  combine  with  the  vapours  of 
sodium.  Hence,  the  formation  of  the  black  compound  is  prevented,  which  is  otherwise 
apt  to  choke  the  exit-tube.  The  sodium  obtained  in  this  manner  is  pure. 

After  the  completion  of  the  process  the  contents  of  the  crucible  are  poured  out  to 
make  room  for  a  new  charge.  The  average  composition  of  the  residue  is : 

Sodium  carbonate          .        .        .        -77  per  cent. 
Sodium  peroxide  .         .         .  2      „ 

Carbon 2      „ 

Iron 19       „ 

In  preparing  potassium  less  carbide  is  used  to  prevent  the  formation  of  carbon 
monoxide,  and  the  distillation  proceeds,  it  is  said,  smoothly. 

The  average  weight  of  the  residue  of  a  mixture  of  5'6  kilos,  sodium  carbonate 
and  i '97  kilos,  carbide  amounts  to  about  6  kilos.  From  this  there  are  recovered 
4-85  kilos,  anhydrous  sodium  carbonate,  corresponding  to  3^  kilos,  sodium  hydrate  at 
76  per  cent. 

If  the  manufacture  is  carried  on  as  above  laid  down,  the  yield  (according  to 
Mactear)  of  5'6  kilos,  soda  is  0*933  kilos,  sodium. 

On  each  charge  the  distillation  lasts  i^  hour.  Thus,  as  the  furnace  receives  three 
crucibles  it  is  possible  to  work  up  3  x  5*6  kilos.  =  16*8  kilos,  sodium  hydrate,  and  to 
obtain  2"jg  kilos,  sodium  and  14-5  kilos,  sodium  carbonate.  The  furnace  yields  daily 
from  2687  kilos,  sodium  carbonate,  44-7  kilos,  sodium,  and  232*8  kilos,  anhydrous 
soda. 

The  estimated  daily  working-cost  for  a  furnace  using  the  quantities  of  sodium 
hydrate  and  "  carbide,"  is — 

2687  kilos,  caustic  soda 71  shillings 

55-9  kilos,  carbide 6        „ 

Labour .  20        „ 

Fuel 17 

Cost  of  converting  232-8  kilos,  of  sodium  carbonate 

into  hydrate 20        „ 

134        >i 

Caustic  soda  recovered  from  177-2  kilos.        .        .46        „ 

447  kilos,  sodium  cost  nett  .         "        .        .     88        „ 

I  kilo,  sodium  costs  .  2        „ 


SECT,  ii.]  ALUMINIUM.  221 

As  far  as  experience  goes  the  wear  and  tear  of  the  crucibles  and  the  furnace  is  said 
to  be  unimportant,  as  200  operations  can  be  effected  with  the  same  apparatus,  the  loss 
for  these  items  would  be  about  0-45  of  a  shilling  on  i  kilo,  sodium,  or  one-twelfth  the 
amount  in  the  old  process.     The  statement  of  Mactear 
that  a  temperature  of  830°  is  sufficient  for  the  dis-  Fig.  219. 

tillation  can  scarcely  be  accurate.* 

Sodium  is  an  important  reducing  agent  in  the  pre- 
paration of  aluminium,  magnesium  and  silicon,  as  also 
as  of  various  organic  compounds. 

The  electrolytic  production  of  sodium  has  not  yet 
come  into  practical  use.  The  oxygen  compounds,  as 
well  as  the  chloride,  the>  decomposition-heat  of  which 
=  98^000  heat-units  (calories),  are  not  suitable  mate- 
rials. Concerning  sodium  fluoride,  a  by-product  in 
the  production  of  aluminium,  further  experiments  are 
wanting. 

The  production  of  potassium  is  hitherto  effected  according  to  the  old  process  for 
sodium,  but  the  oxygen  must  be  still  more  carefully  excluded.  The  potassium  collects 
in  the  receiver  (Fig.  219),  consisting  of  the  two  parts,  d  and  s.  When  this  is  almost 
full  it  is  taken  off,  and  plunged  into  mineral  oil  and  purified  by  distillation. 

The  price  of  potassium  is  considerably  higher  than  that  of  sodium,  as  there  is 
formed  during  its  preparation  a  black  explosive  compound  of  potassium  and  carbon, 
KGCg06,  which  diminishes  the  quantity  of  the  yield  and  may  occasion  serious  mischief. 
This  is  said  to  be  obviated  by  Castner's  process. 

ALUMINIUM. 

Aluminium,  in  the  form  of  alumina  (aluminium  oxide),  is  one  of  the  most  abun- 
dant substances  on  the  surface  of  the  earth.  It  was  first  isolated  by  Woehler,  by  means 
of  the  action  of  potassium  upon  aluminium  chloride 

It  was  for  some  time  obtained  only  by  the   decomposition  of  aluminium-sodium 
chloride  by  means  of  sodium.     The  double  chloride  is  prepared  by  treating  a  mixture 
of  alumina  with  sodium  chloride  and  tar  with  chlorine  gas,  in  a  retort  at  a  red  heat : 
A1,O3  +  sCl,  +  30  =  A12C16  +  3CO. 

The  aluminium  chloride  is  volatilised  as  the  double  aluminium-sodium  chloride, 
and  is  condensed  in  a  walled  chamber,  lined  internally  with  earthenware.  The  double 
chloride  is  decomposed  by  bringing  it  in  contact  with  sodium  on  the  sole  of  a  rever- 
beratory,  when  there  ai*e  formed  free  aluminium  and  a  saline  mass,  consisting  of  the 
double  chloride  and  the  excess  of  sodium  chloride,  which  incloses  the  metallic 
aluminium,  f 

*  Weldon  calculated  the  cost  of  sodium  at  7«.  to  8s.  per  kilo.,  but  the  greater  portion  of  this  sum 
is  for  the  destruction  of  the  retorts  in  which  the  process  was  then  effected.  Castner  hopes  to  be 
able  to  produce  sodium  at  25  cents  per  Ib.  He  effects  the  reduction  by  carbon  diffused  in  alkali, 
melting  at  moderate  temperatures,  or  by  means  of  a  metallic  carbide.  Mierzinski  and  Jablochkoff 
propose  to  obtain  sodium  by  the  electrolysis  of  sodium  chloride.  (See  Aluminium,  by  Jos.  W. 
Richards,  pp.  130-143.) 

•f  A  modification  of  this  has  been  worked  at  Salindres,  by  A.  R.  Pechiney  &  Co.,  successors  to 
Henri  Merle  &  Co. 

The  raw  material  is  bauxite.  This  is  first  converted  into  sodium  aluminate  to  get  rid  of  the 
accompanying  iron  (ferric  oxide).  From  the  solution  of  the  aluminate  hydrated  alumina  is  thrown 
down  by  a  current  of  carbon  dioxide  and  washed.  The  precipitate  thus  obtained  is  mixed  with 
carbon  and  sodium  chloride,  and  this  mixture  is  treated  with  chlorine  gas  to  obtain  the  double 
aluminium-sodium  chloride  which  is  finally  decomposed  by  treatment  with  sodium.  In  this  last 
operation  cryolite  (the  aluminium-sodium  fluoride)  is  added.  The  production  of  aluminium  at 


222  CHEMICAL   TECHNOLOGY.  [SECT.  n. 

The  process  of  Cowles  Brothers,  which  calls  in  the  aid  of  electricity,  and  which  is 
rather  adapted  for  the  production  of  certain  valuable  alloys  than  of  pure  aluminium, 
is  thus  described  : — 

The  inventors  use  a  furnace,  L  (Fig.  220),  the  iron  cover  of  which,  N,  contains 
openings,  n,  for  the  escape  of  the  carbon  monoxide  evolved.  At  the  bottom  is  a 
stratum  of  powdered  coal,  saturated  with  milk  of  lime,  about  a  hand's-breadth  in 
depth.  Over  this  is  spread  the  mixture  to  be  reduced,  P,  consisting  of  broken 
corundum,  mixed  with  fragments  of  charcoal  and  the  requisite  quantity  of  copper  (i.e., 
for  the  formation  of  bronze)  in  small  grains.  By  means  of  a  rectangular  frame  of 
sheet-metal,  it  is  arranged  that  the  coarser  materials  lie  only  in  the  middle.  The 
electrodes,  MM',  which  enter  the  hearth,  serve  for  the  production  of  a  powerful 
electric  arc.  They  are  blocks  of  carbon,  7-5  centimetres,  in  square  sections  of  75  centi- 
metres in  length.  The  furnace  itself  is  i^  metre  long  and  0-3  metre  broad  and 
deep.  After  the  charge  of  ore,  more  charcoal  is  spread,  in  the  first  place,  between  the 
wall  of  the  hearth  and  the  sheet-metal  frame,  and,  after  its  removal  as  a  layer,  O',  to 


cover  the  whole.  The  furnace  is  then  closed  with  its  cover,  and  the  current  is  passed 
through. 

According  to  Mehner,  the  machine  used  yields,  at  907  i-otations,  1575  amperes  and 
47  volts.  To  prevent  short-circuiting,  strong  resistances  must  be  inserted  at  first. 
In  about  one  hour  the  reduction  is  complete.  The  aluminium  bronze  at  the  bottom  of 
the  furnace  contains  15  to  35  per  cent,  aluminium.  In  the  layer  of  carbon  above 
there  is  said  to  exist  an  aluminium  carbide.  A  dynamo  of  100  electric  horse-power 
is  said  to  produce  in  20  hours  150  kilos,  of  a  10  per  cent,  aluminium  bronze.  A  com- 
pany at  Lockport  has  bought  a  water-power  of  1000  horse-power  hours,  and  expects 
to  produce  the  aluminium  alloys  so  cheaply  that  the  aluminium  contained  in  them  will 
cost  only  35.  6d. — a  hope  which  is  very  sanguine.  It  is  improbable  that  pure  aluminium 
will  be  produced  in  this  manner  at  4  to  5  shillings  per  kilo. 

According  to  Maberry,  the  volatilisation  of  aluminium  in  this  process  may  be  pre- 

Salindres  has  been  from  2000  to  3000  kilos,  yearly.  The  cost  per  kilo,  is  estimated  at  69^  francs. 
For  the  details  of  the  processes,  the  reader  is  referred  to  Fremy's  Encyloptdie  Chimique. 

A  novelty  was  the  introduction,  as  a  raw  material,  of  cryolite,  A^Na^F,,.  Its  use  is  not  free 
from  disadvantages,  as  the  yield  is  relatively  small ;  the  crucibles  are  attacked,  and  the  aluminium 
obtained  is  deficient  in  purity. 

Webster's  process,  used  at  the  Aluminium  Crown  Metal  Works,  at  Hollywood,  turns  upon  the 
use  of  an  exceptionally  pure  alumina.  The  inventor  incorporates  three  parts  pure  alum  with  one 
part  of  coal  pitch,  and  heats  to  200°  or  260°.  After  treatment,  the  particulars  of  which  are  found 
in  the  author's  patent,  a  product  is  obtained  containing  8-41  per  cent,  of  actual  A12O3,  the  cost  of 
which  is  said  to  fall  below  ^100  per  ton. 

From  the  by-products  it  was  said  that  a  blue  dye  was  obtained  which  .served  as  a  substitute 
for  indigo  (!),  and  was  worth  6s.  per  Ib.  This  colouring  matter  is  a  Prussian  blue,  which  is  of 
course  not  without  value.  Beyond  taking  this  pure  alumina  as  a  raw  material,  Webster's  pro- 
cedures do  not  seem  to  involve  any  novelty.  The  sodium  produced  is  of  excellent  quality,  but  it  is 
too  costly  for  extended  uses. 

For  a  number  of  proposed  methods,  none  of  which  seem  to  have  achieved  any  decided  success, 
the  reader  may  consult  Aluminium,  by  Jos.  W.  Eichards  (pp.  178-189). 


SECT,  ii.]  ALUMINIUM.  223 

vented  by  the  presence  of  copper,  tin,  or  iron.     No  electrolytic  aluminium  has  yet 
appeared  in  the  market. 

The  process  of  Prof.  Netto  is  carried  out  by  the  Alliance  Aluminium  Company  at 
Wallsend-on-Tyne. 

These  works  at  present  comprise  four  reverberatories,  arranged  in  two  blocks,  each 
23  ft.  by  8|  ft.  by  9  ft.  high.  Each  furnace  is  charged  from  the  top  with  a  mixture  of 
cryolite  and  salt,  which  when  melted  is  drawn  off  into  a  movable  iron  converter  in 
which  the  decomposition  is  effected.  Sodium  is  thrown  into  the  molten  mass,  which  is 
worked  about  with  an  iron  dipper,  until  all  action  ceases.  The  slags  are  then  run  off 
into  an  iron  pot,  and  the  aluminium  is  found  in  the  shape  of  a  "  button"  at  the  bottom 
of  the  converter.  The  yield  of  metal  is  about  8  per  cent,  on  the  weight  of  cryolite, 
and  three  parts  of  sodium  are  used  to  furnish  one  part  of  aluminium.  The  resulting 
slag,  sodium  fluoride,  on  treatment  with  an  oxygen  salt  of  aluminium,  forms  an  artifi- 
cial cryolite,  which  serves  for  the  production  of  aluminium  as  well  as  the  natural 
mineral.  For  producing  i  ton  of  aluminium  there  are  required  12  tons  cryolite,  12 
tons  common  salt,  12  tons  coke  for  heating,  and  3  tons  sodium.  The  by-products  are 
20  tons  slag,  containing  40  per  cent,  sodium  fluoride,  15  per  cent,  of  undecomposed 
cryolite,  and  a  trace  of  clay,  the  remainder  being  common  salt. 

Properties. — Aluminium  is  greatly  modified  even  by  small  quantities  of  other 
metals.  The  common  commercial  metal  has  a  slight  bluish-white  cast,  intermediate 
between  the  colours  of  tin  and  zinc.  But  the  pure  metal  is  almost  absolutely  white. 
It  is  very  malleable  and  ductile  ;  it  can  be  beaten  into  leaf  as  thin  as  gold-leaf.  When 
cast  it  is  as  soft  as  silver,  but  by  hammering  and  rolling  it  is  rendered  nearly  as  hard 
as  iron.  Its  specific  gravity  at  4°  is,  when  cast,  2-56.  According  to  Deville,  it  con- 
ducts electricity  eight  times  better  than  iron.  The  melting-point  of  the  absolutely 
pure  metal  is  about  650°,  but  ordinary  commercial  samples  are  about  815°.  It  is 
probably  the  most  sonorous  of  all  metals. 

As  regards  its  chemical  properties,  it  is  not  oxidised  by  the  action  of  air  or  water. 
Unlike  silver,  it  is  not  blackened  by  sulphuretted  hydrogen.  Nitric  and  sulphuric 
acids  scarcely  affect  it,  but  in  hydrochloric  acid  or  in  solutions  of  the  caustic  alkalies  it 
dissolves  readily. 

Applications. — From  its  combined  lightness  and  strength  aluminium  is  admirably 
adapted  for  use  in  watch-making,  for  the  frames  of  microscopes,  spectroscopes,  and 
other  delicate  optical  and  physical  instruments,  and  for  many  surgical  appliances.  It 
will  probably  supersede  all  other  metals  for  the  production  of  bells,  wind  instruments, 
and  pianoforte  wires.  Its  high  conductive  power  for  electricity,  joined  to  its  great 
lightness,  render  it  preferable  to  iron  and  copper  for  telegraph  wires.  This  is  especially 
the  case  as  regards  field  telegraphs.  An  aluminium  wire  extending  three  miles  will 
not  weigh  as  much  as  copper  wire  of  one  mile. 

Alloys. — The  alloys  of  aluminium  are  exceedingly  important.  An  alloy  of  aluminium 
and  iron  (Mitis  metal)  is  said  to  be  from  30  to  50  per  cent,  stronger  than  the  iron  from 
which  it  is  made,  and  is  certainly  free  from  porosity  and  from  enclosed  air-bubbles.  Even 
such  small  proportions  of  aluminium  as  o'2  per  cent,  greatly  improve  the  quality  of  iron 
and  steel.  "  "Wasters  "  are  almost  unknown  to  ironfounders  who  use  aluminium,  and 
very  thin  parts  and  sharp  edges  are  thus  cast  with  oase. 

The  aluminium  bronzes,  containing  2^,  5,-?i>  an^  i°  per  cent,  aluminium,  accord- 
ing to  the  purpose  intended,  are  both  useful  and  ornamental.  For  artillery,  the 
10  per  cent,  aluminium  bronze  is  the  metal  par  excellence,  by  reason  of  its  hardness  and 
homogeneity,  its  high  breaking-strain,  its  elasticity,  and  resistance  to  corrosion.  This 
10  per  cent,  bronze  is  not  changed  in  its  properties  how  often  so  ever  it  is  re-cast.  It 
will  not  only  take  the  place  of  phosphor-bronze,  silicon-bronze,  &c.,  but  even  of  steel 
.for  ships'  propellers,  pistons,  cylinders,  cogged  wheels,  engine-fittings  of  most  kinds, 


224 


CHEMICAL  TECHNOLOGY. 


[SECT.  ii. 


bearings,  &c.  Mierzinski  is  of  opinion  that  in  any  part  of  a  machine  which  is  com- 
monly made  of  steel,  this  bronze  can  be  substituted.  Its  strength  when  hammered  is 
equal  to  the  best  steel.  Soldering  aluminium  and  its  alloys  was  for  some  time  a  diffi- 
culty, but  the  Alliance  Aluminium  Co.  now  supply  a  solder  which  works  perfectly  if 
the  instructions  are  followed.  Aluminium  can  be  welded  electrically,  and  it  has  the 
advantage  of  not  clogging  files. 

MAGNESIUM. 

Magnesium,  which  occurs  in  exhaustless  quantities  in  sea-water  as  magnesium 
chloride  and  bromide,  and  in  carnallite,  as  sulphate  in  kieserite,  schcenite,  and  kainite, 
and  as  carbonate  in  magnesite  and  the  dolomites,  has  only  been  included  among  the  tech- 
nical metals  within  the  last  twenty  years.  It  is  silvery  white ;  its  recent  fracture 
appears  either  slightly  crystalline,  finely  granular,  or  even  fibrous.  It  is  as  hard  as 
calcareous  spar,  and  becomes  dull  on  exposure  to  the  air.  Slightly  above  its  melting 
point  it  takes  fire,  and  burns  to  magnesia  with  a  dazzling  white  light.  Its  sp.  gr. 
is  =1743. 

It  has  hitherto  been  produced  exactly  like  aluminium,  magnesium  chloride,  or 
carnallite,  being  decomposed  by  heating  in  contact  with  sodium. 

Until  recently,  it  was  prepared  by  the  Magnesium  Metal  Company,  at  Patricroft, 
near  Manchester  (conducted  by  Mellor) ;  by  the  American  Magnesium  Company,  at 
Boston,  U.S.A.  (producing  each  2500  kilos.)  ;  and  in  Paris  (about  100  kilos.). 

The  magnesium  of  commerce  is  never  pure,  as  is  seen  from  the  following  analysis 
(1872  and  1876).  I.  is  English  magnesium,  and  II.  and  III.  are  French  samples  : — 


Magnesium 

Aluminium 

Zinc 

Iron 

Carbon 

Silicon 


(I.) 

96 '38 1  per  cent. 
0-342 


0-673 

O'I20 
2-309 


(II.) 
92-357  per  cent. 


5-686 
0-091 
1-860 


(in.) 

93-620  per  cent. 
0-216 
3-063 

O'lOI 
O'20I 
2-421 


Kg.   221. 


In  1852  Bunsen  prepared  magnesium  elect rolytically  from  magnesium  chloride  by 
means  of  his  zinc-carbon  elements.     As  decomposing  cell  he  used  a  porcelain  crucible, 
9  centimetres  in  height  and   5  centimetres  in  width,  divided  into  two  halves  by  a 
partition  reaching  down  to  half-depth.    Through  the  cone  were  passed  the  two  carbon 
poles  of  the  battery.     The  saw-like  projections  of  the  negative  pole 
served  to  hold  the  separated  metal  below  the  melting  salt,  as  it 
otherwise  rises  to  the  surface  and  ignites.     The  author  was  the 
first  to  show  that  fused  potassium-magnesium  chloride  (KMgCl3 
carnallite)  is  very  suitable  for  the  electrolytic  separation  of  mag- 
nesium, and  that  its  combustion  may  be  prevented  by  the  intro- 
duction of  reducing-gases. 

In  order  to  heat  the  porcelain  crucible  to  a  red  heat  as  uniformly 
as  possible,  there  were  used  two  sheet  iron  rings,  a  and  b  (Fig.  221) 
lined  with  asbestos  pasteboard  connected  below  by  three  strong  wires 
and  resting  on  three  feet,  z.  The  cover,  which  is  also  lined  below 
with  asbestos  pasteboard,  has  an  opening  in  which  the  crucible  fits 
when  it  rests  upon  a  thick  iron  wire  enclosed  in  the  pipe-clay  tube, 
x.  If  a  triple  burner  is  placed  below,  the  hot  gases  play  uniformly 
round  the  crucible,  as  they  are  compelled  by  the  outer  ring,  b,  to  re-descend  in  the 
direction  of  the  arrows.  When  the  double  salt  is  melted,  a  round  asbestos  plate,  v,  is 
put  on  and  pressed  firmly  upon  the  edge  of  the  crucible  by  the  heavy  cast  iron  ring,  b. 
The  asbestos  plate  contains  an  earthen  tube,  o,  in  which  have  been  bored  several  lateral 


SECT,  ii.]  MAGNESIUM.  225. 

holes.  In  this  earthen  tube  there  is  secured,  by  means  of  asbestos  plates,  the  carbon 
which  serves  as  positive  electrode,  and  the  tube  r,  with  a  lateral  appendage  for 
carrying  off  the  chlorine.  This  form  of  tube  was  selected  to  obviate  possible  obstruc- 
tions and,  after  lifting  off  the  plug,  to  ascertain  the  development  of  chlorine  by  means 
of  a  slip  of  litmus-paper.  As  negative  pole  is  used  an  iron  wire,  e,  5  millimetres  in 
thickness,  the  lower  end  of  which  forms  a  ring  round  the  carbon.  Gas  is  very  slowly 
introduced  through  the  tube  g  ;  it  has  been  dried  over  calcium  chloride,  and  escapes 
with  the  chlorine  through  the  tube  r.  The  magnesium  melts  in  balls  of  the  size  of  a 
nut.  Graetzel  has  modified  this  process  by  using  the  iron  crucible  as  a  negative 
electrode,  as  Davy  proposed  for  potassium. 

Considerable  quantities  of  magnesium  are  now  so  cheaply  prepared  by  the  elec- 
trolysis of  carnallite  that  the  sodium  process  can  no  longer  compete. 

The  technical  uses  of  magnesium  are  not  important.  As  an  illuminating  agent  it 
can  be  thought  of  only  in  special  cases,  for  military  purposes,  &c.  A  Berlin  firm 
recommends  for  a  white  fire,  shellac  i  part,  6  parts  barium  nitrate,  and  2\  per  cent, 
magnesium  powder.  The  shellac  and  the  barium  salt  are  melted  together  and  ground. 
For  a  red  fire  the  mixture  is  similar,  only  for  the  6  parts  barium  nitrate  are  substituted 
5  parts  strontium  nitrate. 


SECTION    III. 
CHEMICAL   MANUFACTURING   INDUSTRY. 


WATER  AND  ICE. 

WATER  occurs  as  rain-,  spring-,  river-,  and  sea-water.  When,  after  sunset,  objects 
upon  the  earth's  surface  are  cooled  down  below  the  dew-point,  a  part  of  the  water 
existing  in  a  gaseous  state  in  the  air  is  precipitated  upon  such  objects  as  dew,  in  the 
form  of  small  drops,  or  as  hoar-frost  if  the  temperature  be  below  o°.  If  a  considerable 
volume  of  air  is  cooled  below  its  dew-point,  the  corresponding  quantity  of  water  is  also 
separated  in  minute  drops,  forming  mists  or  clouds.  These  drops  sink  down  slowly, 
and  if  the  lower  strata  of  air  are  warmer  and  not  yet  saturated  with  water,  they  resume 
the  form  of  vapour.  But  they  fall  down  upon  the  earth  as  rain — or  frozen  as  snow 
and  hail — if  the  moisture  in  the  lower  strata  of  the  atmosphere  approaches  the  dew- 
point. 

The  quantity  of  the  atmospheric  waters  thus  deposited  is  generally  greatest  within 
the  tropics  and  near  the  sea,  and  smallest  towards  the  poles.  Thus  the  mean  height  of 
the  rainfall  is  at — 

Madrid 
Vienna 
Petersburg    . 
Stockholm    . 
Berlin 
Paris     . 
Hanover 

The  distribution  of  the  rainfall  in  the  seasons  is  very  different.  Autumnal  rains 
predominate  in  Britain,  the  west  of  France,  the  Netherlands,  and  Norway ;  summer 
rains  in  Germany,  Denmark,  and  Sweden  ;  summer  rains  are  absent  in  those  parts  of 
Europe  which  He  nearest  Africa,  i.e.,  southern  France,  Italy,  Portugal,  &c. 

The  quantity  of  rain  in  single  years  deviates  very  considerably  from  the  general 
average.  Thus,  at  Frankfort  the  mean  rainfall  for  thirty  years  is  60  centimetres,  but 
in  1864  it  was  only  36  centimetres,  and  in  1867,  144  centimetres. 

About  half  this  atmospheric  water  is  directly  returned  to  the  air  by  evaporation ; 
the  remainder  chiefly  penetrates  into  the  soil  as  far  as  the  first  impervious  stratum 
along  which  it  flows  in  accordance  with  the  law  of  gravitation,  and  is  finally  either 
raised  artificially  in  wells  or  comes  to  light  in  natural  springs,  and,  in  conjunction  with 
the  surface  drainage,  is  conveyed  to[the  sea  in  brooks  and  rivers.  Generally  a  permeable 
soil  and  shattered  rocks  are  rich  in  springs,  whilst  a  compact  clay  soil  and  a  solid  rock 
formation  yield  only  feeble  springs. 

Composition. — Rain  and  snow  contain  the  constituents  of  atmospheric  air,  nitrogen, 
oxygen,  carbon  dioxide,  and  also  the  impurities  of  the  atmosphere  in  proportion  to 
their  respective  solubilities.  Rain-water  collected  upon  clean  surfaces  can  hence,  in 
many  cases,  be  used  in  the  chemical  arts  in  place  of  distilled  water.  Water  obtained 
from  roofs  is  at  the  commencement  of  wet  weather  often  contaminated  by  dust,  the 


25  centimetres 

London 

.     63  centimetres 

45 

Rome     . 

.     78 

46 

Genoa    . 

.  118 

5i 

Bombay 

.  198 

57 

Havanna 

.  231 

57 

St.  Domingo 

•  273 

58 

SECT.  HI.]  WATER  AND   ICE.  227 

droppings  of  birds,  &c.     Water  which  has   been  preserved  in  cisterns,  and    which 
in  low,  swampy,  coast  districts  is  used  for  all  domestic  purposes,  is  often  very  impure. 
Among  the  impurities  of  the  atmosphere  sulphurous  acid,  chlorine,  ammonia,  and 
nitric  acid  are  the  most  important. 

Sulphurous  acid  or  sulphuric  acid  is  especially  due  to  coal  fires.  According  to 
Sendtner  freshly  fallen  snow  at  Munich  contained  per  kilo.  7  milligrammes  total  sulphuric 
acid,  the  next  day,  17 '6  milligrammes,  in  ten  days  6 2' 2,  and  in  sixteen  days  91*8  milli- 
grammes. Thus  snow  very  quickly  absorbs  the  sulphurous  acid  existing  in  the  air  of 
towns,  which  soon  passes  into  sulphuric  acid.  Such  snow  or  rain  is  very  injurious  to 
statues  or  monuments  of  marble  placed  in  the  open  air.  Angus  Smith  found  at  Liver- 
pool 35  milligrammes  sulphuric  acid  per  litre  of  rain-water,  at  Manchester  50  milli- 
grammes, at  Newcastle-on-Tyne  (among  sulphuric  acid  works)  430  milligrammes,  and 
this  chiefly  in  a  free  state. 

The  proportion  of  chlorine  (or  of  chlorides)  is  of  importance  only  on  coasts. 
The  ammonia  in  rain-water  is  chiefly  derived  from  processes  of  putrefaction,  but  also 
from  chimney  gases,  if  the  combustion  is  imperfect.     Rain-water  generally  contains 
from  0-5  to  5  milligrammes,  but  sometimes  as  much  as  30  milligrammes  per  litre. 
Snow  after  remaining  a  long  time  on  the  ground  contains  much  ammonia. 

Rain-water  contains  also  from  i  to  10,  but  sometimes  even  50  milligrammes 
nitric  acid,  due  either  to  the  decomposition  of  organic  matter,  or  formed  by  electric 
discharges. 

Spring-  and  Well- Water. — The  rain-water  charged  with  these  matters  penetrates 
chiefly  into  the  soil  when  it  does  not  immediately  evaporate,  and  comes  up  to  daylight 
in  springs,  or  is  artificially  raised  in  wells  after  taking  up  more  or  less  of  the 
constituents  of  the  strata  which  it  has  traversed. 

In  water  it  is  common  to  distinguish  the  carbonic  acid  into  that  which  forms,  with  the 
•existing  metals,  simple  carbonates ;  that  which  is  half -combined,  forming,  with  the  car- 
bonates, bicarbonates,  and  being  capable  of  expulsion  by  boiling ;  and  that  which  again 
is  free,  and  merely  dissolved  in  the  water.  In  some  springs,  especiaDy  in  volcanic 
•districts  (as  the  Eifel,  the  Laach  lake,  &c.),  the  water  holds  in  solution  carbonic  acid, 
in  volumes  several  times  exceeding  its  own.  The  ordinary  well-  and  spring-waters  owe 
their  carbonic  acid  in  part  to  the  atmosphere,  but  chiefly  to  the  processes  of  putrefaction 
-and  decay  taking  place  in  the  soil.  Carbonic  acid  assists  in  the  decomposition  of 
minerals,  and  forms  calcium  and  magnesium  bicarbonates,  less  frequently  similar 
compounds  of  iron,  sodium,  &c.,so  that  ordinary  spring- waters  contain  only  a  relatively 
small  quantity  of  carbonic  acid  in  a  free  state.  Well-waters  contain,  as  a  rule,  no  free 
•carbonic  acid,  but  often,  in  a  greatly  polluted  soil,  considerable  quantities  of 
•calcium  and  magnesium  carbonate,  and  have,  in  consequence,  a  great  transitory 
hardness. 

The  quantities  of  lime,  magnesia,  alkalies,  sulphuric  acid,  &c.,  vary  very  greatly 
according  to  the  nature  of  the  soil.  The  less  variable  are  the  quantities  of  the  products 
of  the  decomposition  of  animal  excretions,  which  in  populous  places  penetrate  into  the 
•earth  to  a  great  depth.  Such  matters  at  ordinary  temperatures  and  under  the 
influence  of  certain  microscopic  organisms,  are  quickly  resolved  into  decomposition 
products  as  yet  but  imperfectly  known.  In  presence  of  atmospheric  oxygen  they 
form  carbonic  acid,  ammonia,  and  then  nitrous  and  nitric  acids.  The  phosphates,  the 
nitrogenous  organic  matters,  and  the  ammonia  are  in  part  retained  in  the  soil,  and 
•conveyed  to  the  roots  of  plants  ;  the  chlorides,  nitrates,  and  sulphates  are  carried  away 
by  the  water  to  the  wells  and  springs.  These  changes  take  place  especially  in  soils 
•covered  with  vegetation.  Polluted  waters  after  filtering  through  the  soil  contain  much 
more  nitric  nitrogen  (nitrogen  in  the  state  of  nitrous  and  nitric  acid)  than  they  did 
previously.  If  nitrogenous  organic  substances  are  conveyed  into  a  soil  not  covered  with 


228  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

plants,  then  if  the  access  of  air  is  sufficient,  the  nitrogen  of  such  organic  matter  and 
the  ammonia  which  has  been  formed  are  quickly  converted,  firstly  into  nitrous,  and 
then  into  nitric  acid,  which  are  taken  up  by  the  water  in  the  soil,  and  conveyed  into 
the  springs  and  wells.  If  sufficient  oxidation  cannot  be  effected,  from  scanty  access  of 
air,  when  the  absorptive  power  of  the  soil  is  exhausted,  the  ammonia  and  the  putrescent 
organic  substances  are  taken  up  by  the  water.  Water  which  springs  out  of  the  earth 
remote  from  human  habitation  may  be  perfectly  free  from  decomposing  animal 
products  or  may  contain  mere  traces.* 

The  water  of  wells  which  reach  down  into  the  ground-waters  of  cities  and  are 
partly  fed  by  soakage  from  the  street-sewers,  the  cess-pits,  &c.,  contains  impurities  to  a 
serious  degree.  The  proportion  of  sulphuric  acid  may  reach  i  gramme  per  litre ;  that 
of  ammonia  100  milligrammes,  organic  matter  i  gramme,  and  chlorine  90  centigrammes. 
As  the  latter  (except  in  marine  or  saliferous  districts)  is  chiefly  derived  from  the 
sodium  chloride  of  human  excretions,  its  presence  gives  a  valuable  indication  for 
determining  the  character  of  a  well-water. 

The  composition  of  river- waters  is  naturally  very  different  according  to  the  character 
of  the  formations  which  they  and  their  affluents  traverse.  Sea-water  contains  espe- 
cially sodium  and  magnesium  chlorides,  calcium  and  magnesium  sulphates ;  potassium 
compounds  are  found  only  in  small  quantities.  Calcium  carbonate  is  likewise  scantily 
present,  often  in  mere  traces ;  near  the  coasts  it  is  more  abundant.  Magnesium 
carbonate  is  still  more  sparingly  present. 

It  is  impossible  to  pronounce  a  water  fit  or  unfit  for  domestic  uses  unless  we  know 
its  origin  and  the  surroundings  of  its  source.  It  is  by  no  means  indifferent  whether 
the  organic  matter  detected  in  a  sample  of  water  is  derived  from  a  peaty  soil  or  from 
a  cess-pit.  Here  the  presence  of  chlorine,  ammonia,  and  nitrites  gives  valuable  indica- 
tions. So-called  "  standards  "  and  limits  are  only  of  very  local  value. 

Drinking-water  should  not  be  too  hard,  and  its  temperature  should  fluctuate  little. 
Examination  of  Waters. — The  reader  will  do  well  here  to  consult  the  following 
works: — Water  Analysis,  by  J.  A.  Wanklyn  and  E.  Th.  Chapman;  Volumetric 
Analysis,  by  F.  Sutton  (latest  edition,  the  section  relating  to  the  examination  of 
water) ;  Select  Methods  in  Chemical  Analysis,  by  W.  Crookes,  F.R.S.,  p.  657,  for  esti- 
mation of  free  oxygen  in  water,  and  p.  659,  for  an  expeditious  method  of  estimating 
the  temporary  hardness. 

It  is  a  very  prevalent  error  to  say  that  the  colour  of  water  gives  little  help 
towards  ascertaining  its  quality.  Water  free  from  organic  pollution  has,  if  seen  in 
a  sufficient  volume,  a  peculiar  blue  colour.  If  contaminated  with  organic  matter  in 
solution,  it  has  a  brownish  or  yellowish  colour.  The  process  in  question,  devised  by 
W.  Crookes,  W.  Odling,  and  C.  Meymott  Tidy,  is,  in  substance,  as  follows  :— Two 
hollow  glass  wedges  are  filled,  the  one  with  a  brown  and  the  other  with  a  blue  solu- 
tion. The  blue  solution  is  made  by  dissolving  5  grammes  pure  crystalline  copper  sul- 
phate in  i  litre  distilled  water.  For  the  brown  solution  dissolve  ferric  chloride  and 
cobalt  chloride  in  distilled  water  in  such  proportions  that  i  litre  of  the  solution  may 
contain  07  gramme  of  metallic  iron  and  0-3  gramme  of  metallic  cobalt.  A  very  slight 
excess  of  free  hydrochloric  acid  must  also  be  present.  These  two  wedges  are  made  to 
slide  across  each  other  in  front  of  a  circular  aperture  in  a  sheet  of  metal.  In  this 
manner  any  desired  combination  of  brown  and  blue  can  be  produced.  Each  prism  is 
graduated  along  its  length  from  i  to  40,  the  figures  representing  millimetres  in  thick- 
ness of  the  solution  at  that  particular  part  of  the  prism.  On  a  level  just  below  the 

*  Some  savage  tribes  in  Africa  and  South  America  have  the  dreadful  custom  of  burying  the 
bodies  of  chiefs,  &c.,  underneath  a  spring,  or  in  the  bed  of  a  stream.  Water  containing  no  animal 
pollution  may  be  very  dangerous  in  consequence  of  decomposing  vegetable  matter— e.g.,  the- 
drainage  of  rice-fields  and  the  waters  of  mangrove  thickets. — EDITOB. 


SECT,  in.]  WATER  AND   ICE.  229 

prisms  is  a  2-foot  tube  containing  the  water  to  be  examined,  and  having  in  front  of  it 
a,  circular  aperture  of  the  same  size  as  the  one  in  front  of  the  prisms.  The  stand 
supporting  the  prisms  and  tube  is  placed  horizontally  in  front  of  a  uniformly  lighted 
window.  The  observer,  standing  a  little  distance  off,  sees  two  discs,  the  lower  one 
illuminated  by  light  which  has  passed  through  2  feet  of  the  water,  and  the  upper 
one  illuminated  by  light  which  has  passed  through  the  respective  thicknesses  of  the 
brown  and  blue  solutions.  By  sliding  the  prisms  sideways  one  way  or  the  other,  it  is 
easy  to  imitate  with  considerable  accuracy  the  depth  and  tone  of  the  colour  of  the 
lower  disc.  A  metal  pointer  fixed  over  the  centre  of  the  upper  disc  shows  on  the 
prism  scales  the  number  of  millimetres  in  thickness  through  which  the  light  has 
passed  to  produce  a  colour  which  corresponds  to  that  of  the  water,  and  the  results  are 
recorded  thus  :  "  February  2ist  (New  River),  20 :  21,"  meaning  that  on  that  date  the 
colour  of  New  River  water  seen  through  a  2 -foot  tube  was  represented  by  20  milli- 
metres of  the  brown  and  21  millimetres  of  the  blue  solution. 

Purification  of  Water. — Water  requires  to  be  purified  in  various  ways,  according  to 
its  original  condition  and  the  purposes  to  which  it  is  to  be  ultimately  applied.  Sewage 
and  industrial  waste  waters,  which  generally  occur  together,  may  be  treated  by  irriga- 
tion, filtration,  or  precipitation.  For  the  conditions  under  which  these  processes  are 
available,  their  drawbacks,  and  the  manner  of  their  execution,  the  reader  may  consult 
Slater's  Sewage  Treatment  and  Purification  (Whittaker).  The  compound  processes  of 
precipitation  may  be  considered  as  "  inverse  irrigation,"  as,  instead  of  passing  the 
impure  water  through  the  soil,  fresh  portions  of  clay,  peat,  &c.,  are  continually  passed 
through  the  sewage,  and  are  then  caused  to  subside  (carrying  with  them  the  impuri- 
ties they  have  absorbed)  by  the  addition  of  a  suitable  salt  of  aluminium  or  iron. 

Water  for  human  consumption,  for  cookery,  &c.,  should  be  as  free  as  possible  from 
organic  matter,  and  especially  from  micro-organisms.  It  is  very  doubtful  in  how  far 
this  can  be  effected  by  any  practicable  filtration.  The  celebrated  Chamberland  filter, 
used  by  Pasteur  in  his  researches,  effects  the  end  desired,  as  far  as  microbia  are  con- 
cerned, but  very  slowly.  Precipitation  with  lime  (see  p.  237,  Clarke  process)  removes 
the  germs  (pathogenic  and  other)  for  a  time,  but  they  are  apt  to  reappear  if  the  clear 
water  is  allowed  to  remain  standing  over  the  precipitate.  From  time  immemorial  the 
Chinese  have  been  in  the  habit  of  adding  to  the  impure  water  which  they  use  for 
drinking  small  quantities  of  alum,  letting  the  precipitate  subside,  and  drawing  off  the 
clear.  Since  this  simple  method  has  been  introduced  among  the  French  troops  in 
Tonkin,  the  soldiers  have  suffered  much  less  from  dysentery — a  fact  proving  that  alum 
not  merely  removes  the  suspended  earthy  matters,  but  is  also  capable  of  eliminating 
dissolved  organic  matter — as  any  one  practically  acquainted  with  the  art  of  dyeing 
would  expect— and  even  organisms.  Brautlecht  (Slater's  Sewage  Treatment,  p.  99) 
even  proposes  the  use  of  alum  for  detecting  or  removing  the  microbia  in  water.  He 
adds  a  few  drops  of  a  solution  of  a  salt  of  aluminium  to  some  of  the  suspected  water, 
allows  the  precipitate  to  settle,  decants  off  the  clear,  redissolves  the  sediment  in  a  few 
drops  of  acetic  acid,  and  searches  for  the  organisms  in  the  solution  thus  obtained. 

Water  for  Steam-Boilers. — In  deciding  on  a  water  for  steam  purposes  it  must  be 
considered  in  how  far  it  may  corrode  the  boiler-plates  or  form  solid  deposits  (crock). 
Whilst  the  destruction  of  the  boiler-plates  from  without  depends  on  the  action  of 
sulphurous  acid,  and  of  an  excess  of  oxygen  in  the  flue  gases  in  presence  of  moisture ; 
injuries  to  the  boiler  from  within  are  to  be  sought  for  in  the  composition  of  the  feed- 
water.  Magnesium  chloride  is  especially  destructive  to  the  plates,  and  in  sugar-works 
it  is  found  that  treacle  has  an  injurious  action  on  the  boilers.  Feed-water  containing 
oily  and  fatty  matter  is  unfit  for  use. 

The  chief  compounds  concerned  in  the  formation  of  crock  are  calcium  sulphate  and 
•calcium  and  magnesium  carbonates. 


230  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

The  calcium  sulphate  separates  according  to  the  temperature  and  the  proportion  of 
saline  matter  in  the  water,  either  as  anhydrite  or  with  water  of  crystallisation ; 
magnesia  is  deposited  as  hydrate.  Calcium  hydrate  also  forms  sol:d  incrustations  if, 
e.g.,  too  much  milk  of  lime  has  been  used  in  purifying  the  water.  The  prevention  of 
crock,  which  interferes  with  the  heating  of  the  water,  is  best  done  in  a  cistern  before 
it  is  pumped  into  the  boiler,  and  may  be  effected  by  means  of  soda.  The  numerous 
patented  or  secret  anti-incrustation  compositions  should  be  regarded  with  suspicion, 
as  most  of  them  are  of  little  or  no  value. 

Water  for  Breweries. — If  perhaps  too  great  an  influence  upon  the  quality  of  beer 
has  been  ascribed  to  the  character  of  the  water,  yet  recent  experiments  have  proved 
that  certain  constituents  of  water  may  act  unfavourably  upon  softening  the  barley  in 
the  mashing  and  the  fermentation. 

The  use  of  water  containing  organic  matter  in  course  of  decomposition  is  especially 
objectionable.  The  organic  matters  attach  themselves  to  the  malt,  carry  on  their 
process  of  decomposition,  induce  putrefaction  and  mouldiness,  and  under  certain  circum- 
stances may  injure  the  fermentation  of  the  wort  obtained  from  such  malt.  Tannic,. 
crenic,  and  apocrenic  acids  are  hurtful.  Water  from  woodlands  and  from  rivers  receiv- 
ing the  waste  waters  of  tanneries  should  be  used  with  caution.*  Beer  made  with 
water  containing  animal  impurities  will  not  keep.  The  drainage  of  the  brewery  itself 
exerts  an  injurious  effect  upon  the  process  of  fermentation. 

As  regards  the  first  products  of  decomposition,  Lintner  points  out  that  as  we  justly 
characterise  their  presence  in  drinking-water  as  suspicious,  they  should  be  used  in 
brewing  and  malting  only  in  extreme  cases  and  with  caution.  A  malthouse  which, 
according  to  Lintner,  worked  with  polluted  water,  had  to  contend  with  the  mouldiness 
of  the  malt,  which  disappeared  as  soon  as  a  different  and  better  supply  of  water  was 
obtained. 

A  considerable  proportion  of  magnesia  is  objectionable.  Concerning  the  presence 
of  lime,  opinions  are  divided,  but  it  has  been  ascertained  that  soft  water  effects  the 
swelling  of  the  barley  more  quickly  than  such  as  is  hard.  But  as  soft  water  dissolves 
out  of  the  barley  on  steeping  more  extractive  matter  and  salts  than  a  calcareous  water, 
greater  care  is  needed  with  the  former.  According  to  Griessmayer,  soft  water  removes 
from  the  grain  of  barley  more  phosphoric  acid  and  potassium  phosphate  than  does  hard 
water,  forming  within  the  grain  insoluble  phosphoric  compounds  which  are  subse- 
quently re-dissolved  by  the  lactic  acid  of  the  mash.  On  the  other  hand,  hard  water 
during  steeping  causes  the  formation  of  insoluble  proteine-lime  compounds,  and  thus 
diminishes  the  yield  of  soluble  albuminoid  matter.  A  water  containing  a  moderate 
proportion  of  lime  is  decidedly  preferable  for  malting.t 

In  the  subsequent  operations,  a  soft  water  is  preferable,  although  a  gypsiferous 
water  promotes  the  clearing  of  the  wort. 

"Water  for  distilleries  should  be  as  pure  as  possible,  and  should  be  at  a  low  tempera- 
ture in  summer. 

Water  for  starch-works  should  be  especially  free  from  suspended  matter,  organic 
excretions,  vegetable  residues,  salts  of  iron,  and  algae. 

All  these  substances  may  pass  through  the  sieves  along  with  the  staruh,  remaining 
in  it  partially  in  the  centrifugal  process,  and  appear  in  it  when  dry.  The  water  must 
be  free  from  ferments  and  schizomycetes.  The  former  prevent  the  starch  from  de- 
positing, and  throw  it  into  the  so-called  flowing  state.  The  others  form  organic  acids, 
such  as  the  lactic  and  butyric,  which  cannot  be  entirely  removed,  even  by  the  most 
prolonged  washing,  and  also  give  the  starch  a  putrid  odour.  The  warmer  the 

*  Or  rather,  as  far  as  tan-liquors  are  concerned,  be  totally  rejected. 

t  The  largest  malthouses  in  England,  e.g.,  those  of  Hertford  and  Stowmarket,  have  sprung  up- 
in  districts  supplied  with  hard  water. 


SECT,  m.]  WATER  AND   ICE.  23! 

weather  the  more  dangerous  is  the  presence  of  the  organisms  of  putrefaction.  Organic 
matter  and  ammonia  render  the  water  suspicious,  and  salts  of  iron  are  a  total  bar  to 
its  use. 

The  water  can  generally  be  much  improved  by  the  addition  of  a  little  milk  of  lime 
and  warming  or  filtering. 

For  sugar-works,  chlorides  are  less  liable  to  promote  treacle  than  are  the  sulphates 
and  alkaline  carbonates ;  especially  hurtful  are  the  nitrates,  which  render  six  times 
their  own  weight  of  sugar  unable  to  crystallise.  The  behaviour  of  the  water  in 
steam  boilers  is  also  very  important  at  sugar- works,  on  account  of  the  great  demand 
for  steam. 

In  paper-mills,  the  presence  of  iron  is  very  injurious,  on  account  of  the  formation 
of  rust-spots ;  lime  and  magnesia  weaken  the  solution  of  the  resin-soap  by  partial 
decomposition. 

Water  for  tanneries  should  contain  no  putrescent  organic  matter,  as  this  causes 
the  leather  to  decay.  Eitner's  experiments  prove  that  free  carbonic  acid  and  water 
containing  bicarbonates  swell  the  hides  ;  chlorides  do  not  unite  with  the  hides,  and  even 
counteract  the  swelling  effect  of  acids.  Hence  sea-water  is  unfit  for  tanning.  Calcium 
and  magnesium  sulphates  are  especially  good  for  swelling  the  hides.  This  explains 
the  advantageous  action  of  a  careful  addition  of  sulphuric  acid  to  a  water  containing 
an  abundance  of  bicarbonates. 

The  finished  leathers  resulting  from  these  experiments  were  quite  in  accordance 
with  their  appearance  after  swelling.  The  specimen  which  had  been  treated  with 
magnesium  sulphate  had  the  finest  cut,  and  next  came  that  with  sulphuric  acid.  Samples 
with  distilled  water,  or  with  bicarbonates,  differed  respectively  little,  that  with  cal- 
cium carbonate  being  the  worst.  All  these  leathers  were  very  firm,  full,  with  a  com- 
pact grain,  and  the  cut  surface  was  smooth  and  shining.  Samples  from  salt  and 
magnesium  chloride  were  thinner  than  the  above,  and  comparatively  soft ;  the  fibrous 
texture  was  finer. 

In  the  manufacture  of  glue,  it  is  found  that  the  extraction  of  the  raw  materials 
(parings  of  hides,  &c.)  is  far  more  complete  with  soft  than  with  hard  water.  A  glue 
boiled  with  hard  water  does  not  re-dissolve  clear  after  being  once  dried  up. 

For  bleach-  and  dye-works,  water  should  be  perfectly  clear  and  colourless,  containing 
especially  no  iron. 

If  a  water  contains  so  much  organic  matter  as  to  be  distinctly  coloured,  if  used  for 
bleaching  wool  it  occasions  stains  in  the  goods.  If  iron  is  present,  then  on  treating 
the  wool  with  soda,  ammonia,  or  lant,  the  iron  is  fixed  on  the  fibre  in  the  state  of 
oxide,  or  if  soap  is  used  as  an  iron-soap.  Iron-water  in  the  flot  has  a  very  injurious 
effect  upon  the  tones  of  the  colours,  so  that  it  cannot  be  advantageously  used  even  for 
dark  shades.  Iron- waters  are  not  less  injurious  in  other  dyeing  and  printing  opera- 
tions and  in  bleaching. 

Hard  waters  do  not  bleed  the  dye-wares  freely,  and  often  modify  the  tone  of  the 
colours  produced.  For  all  bright  and  light  shades  they  are  injurious,  though  in  sad 
shades  or  in  blacks  they  economise  the  dye-ware.  But  it  is  easier  to  render  a  soft 
water  hard  for  any  particular  purpose  than  to  soften  a  hard  water.  Hard  waters,  as  a 
matter  of  course,  decompose  soap.* 

Madder  and  its  preparations  form  an  exception  to  most  colouring  matters  in  their 
behaviour  with  hard  waters.  As  far  back  as  1791  J.  M.  Haussmann  observed  that  in 
turkey-red  dyeing  fiery  tones  can  be  produced  only  with  calcareous  water.  According 
to  Kielmeyer,  grain-reds  and  mock-crimsons  (peach  wood,  &c.),  whether  in  cotton  or 
wool,  take  a  bluish  tone  in  hard  water,  which  g'reatly  interferes  with  their  brightness. 

*  Compare  Slater,  Manual  of  Colours  and  Dye  Wares,  p.  221.     Crosby  Lockwood  &  Co. 


232  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

The  genuine  old  madder  red  and  rose  as  well  as  the  modern  alizarine  red  and  rose  do 
not  escape  the  action  of  calcareous  water  (?),  On  the  contrary,  coralline  red, 
generally  so  fugitive  upon  wool  or  cotton,  is  not  affected  by  calcareous  water,  just  as 
coralline  reds  upon  wool  resist  a  frequent  soaping  much  better  than  do  grain  (cochineal) 
reds.  The  influence  of  calcium  and  magnesium  carbonate  in  the  water  is  especially 
shown  when  the  wet  goods  are  dried  in  the  stove  or  on  the  hot-flue.  The  carbonates 
remaining  along  with  the  water  in  the  wet  tissue  act  upon  the  red  like  a  feeble  alkali, 
giving  it  a  bluish  cast  and  thereby  darkening  it.  Hence  it  is  prudent  to  dry  such 
ware  spread  out  as  much  as  possible  in  a  cold  room.  But  the  carbonates  remain  in 
the  air-dried  goods  and  have  still  the  opportunity  to  act  upon  the  colours  on  hot  press- 
ing or  calandering  or  passage  over  the  drum.  If  the  dyed  woollen  goods  after  washing 
but  before  drying  are  taken  a  few  turns  through  a  water  slightly  soured  with  acetic 
acid,  or  if  (in  case  of  cotton  goods)  a  small  quantity  of  acetic  acid  or  of  alum  water 
is  added  to  the  dressing,  the  action  of  the  alkaline  earths  upon  reds  will  be 
counteracted.  According  to  the  investigations  of  Rosenstiehl  a  certain  proportion  of 
lime  is  absolutely  necessary  for  madder,  garancine,  and  alizarine  dyeing.  The  aliza- 
rine and  the  purpuririe  must  encounter  in  the  water  of  the  dye-beck  so  much  neutral 
calcium  carbonate  or  acetate  that  there  may  be  formed  under  all  circumstances  mono- 
•calcium  alizarate  or  the  corresponding  purpurine-lime  lake ;  the  latter  is  not  absolutely 
necessary,  but  it  contributes  to  the  fastness  and  brightness  of  the  colour  produced.  In 
order  to  render  the  excess  of  calcium  carbonate  in  a  spring-water  harmless  in  dyeing 
oxalic  acid  seems  to  be  the  most  serviceable  agent ;  it  is  used  in  some  works  for  correct- 
ing the  water,  whilst  in  others  acetic  or  sulphuric  acid  is  employed,  though,  according 
to  Kielmeyer's  observations,  with  very  unsatisfactory  results.  The  oxalic  acid  added  to 
the  flot,  even  though  accurately  calculated,  strips  a  part  of  the  mordant  from  the  cotton 
prior  to  the  formation  of  the  calcium  oxalate,  thus  producing  uneven  colours  and  soiled 
whites.  For  soap-baths  oxalic  acid  is  the  best  corrective.  Here  it  can  be  added  along 
with  potash  to  the  hot  water ;  the  insoluble  calcium  oxalate  is  formed  at  once  before  the 
soap  is  added,  and  the  latter  finds  no  more  lime  in  the  water  which  could  permit  of  the 
formation  of  a  lime-soap.  If  a  soap-bath  has  to  be  often  renewed  and  used  only  for  a 
short  time,  this  method  of  purifying  the  water  is  the  most  suitable.  The  purifying  of 
soap-becks  with  potash  alone  without  the  additional  oxalic  acid  cannot  be  recommended, 
as  it  is  dangerous  for  the  colours.  For  large  soap-becks,  for  raising-pans  which  have  to 
be  set  afresh  only  once  or  twice  daily,  the  water  is  boiled  up  first  with  a  small  portion  of 
the  soap  ;  the  lime-soap  first  formed  is  carefully  skimmed  off,  and  the  soap  is  then  added 
to  the  water  thus  purified. 

In  cleansing  wool  and  woollen  goods  lime  and  magnesia  are  injurious,  not  merely  by 
rendering  a  part  of  the  soap  ineffective,  but  because  the  lime-soap  formed  cannot  be 
easily  removed  from  the  fibre,  and  on  subsequent  treatment  with  the  mordant  and  the 
colouring  matter  it  occasions  a  number  of  irregularities.  In  washing  wool  with  soda, 
ammonia,  or  lant,  lime  and  magnesia  are  less  injurious,  as  any  carbonates  deposited  upon 
the  fibre  are  more  easily  removed  than  lime  and  magnesia  soaps. 

The  constituents  of  water  have  a  remarkable  influence  in  the  treatment  of  raw  silk. 
It  is  universally  recognised  that  the  silk  thread,  as  spun  by  the  caterpillar,  is  coated 
with  a  varnish  or  "  gum,"  which  dissolves  in  boiling  soap-lye.  During  this  treatment, 
according  to  L.  Gabba  and  O.  Textor,  the  colouring  matters  of  the  silk  are  extracted 
also.  Cocoon  silk,  on  repeated  boiling  with  soap,  loses  22*26  per  cent,  and  raw  silk 
20*14  per  cent.,  so  that  on  unwinding  the  cocoon  threads  in  hot  water  2*12  per  cent,  of 
organic  matter  is  lost.  But  these  portions  give  the  raw  silk  its  appearance,  its  colour, 
and  its  strength,  and  hence  they  should  be  retained  in  the  raw  silk.  In  order  to 
render  the  reeling  of  the  cocoons  possible,  the  natural  gum  should  be  softened,  though 
not  dissolved,  as  it  must  cement  the  single  cocoon  threads  together  so  as  to  give 


SECT,  in.]  WATER   AND    ICE.  233 

strength  to  the  raw  silk  after  hardening.  The  strength  of  the  silk  decreases  exactly 
in  proportion  to  the  loss  of  soluble  matter,  whilst  the  elasticity  is  affected  only  in  a 
secondary  degree.  As  the  cocoons  are  softened  in  hot  water  to  facilitate  reeling,  and 
are  kept  floating  during  this  operation  for  convenience,  it  appears  likely  that  the  com- 
position of  the  water  must  not  be  without  influence  upon  the  character  of  the  silk 
obtained. 

In  fact,  comprehensive  experiments  have  shown  that  silks  spun  in  soft  waters  were 
less  fine  in  colour  or  less  strong  than  those  which  had  been  obtained  in  hard  waters. 
The  reason  is  that  the  soluble  matters  which  ought  to  be  retained  are  more  readily 
dissolved  by  soft  than  by  hard  waters,  and  are  thus  removed  from  the  silk. 

Investigation  has  further  decided  that  silks  spun  out  of  waters  rich  in  lime  and 
alkali  give  the  best-looking  products;  therefore  the  producer  of  raw  silk  gives  a  preference 
to  the  use  of  hard  water.  But  for  the  silk-manufacturer,  and  especially  for  the  silk-dyer, 
the  silks  spun  out  of  hard  water  are  not  the  most  advantageous,  as  they  always  contain 
lime  mechanically  enclosed.  The  lime  can  be  shown  by  an  analysis  of  the  ash — the 
harder  the  water  in  which  the  silk  was  spun  the  greater  are  the  quantities  of  lime  found. 
This  inclosed  lime  cannot  be  removed  on  boiling  the  raw  silk  preparatory  to  dyeing. 
Wherever  particles  of  lime  adhere  to  the  fibre  the  colouring  matter  of  the  not  will  be 
taken  up  less  perfectly,  and  the  silks  will  appear  stripy — a  very  important  defect  in 
unloaded,  i.e.,  honest,  silks.  For  bright  shades  the  dyer  will  therefore  give  the 
preference  to  silks  spun  in  soft  waters. 

Water  for  Municipal  and  Domestic  Supplies. — In  the  use  of  soap,  whether  in  the 
household  or  in  manufactures,  the  proportion  of  lime  and  magnesia  in  the  water  is  of 
capital  importance. 

It  is  well  known  that  soap  does  not  give  a  clear  solution  in  cold  water,  but  is 
separated  into  a  soluble,  more  basic  portion  and  a  more  acid  part  insoluble  even  in 
alcohol.  According  to  Fricke,  these  parts  had  the  following  respective  composition  in 
an  experiment  made  with  a  good  curd  soap  : — 

Soap.  Insoluble.  Soluble. 

Fatty  acids     .        .        .    89-55  ...  91-36  ...  86-51 

Soda       ....     10-45  —  8'64  •••  X3'49 


The  insoluble  part  contained  chiefly  palmitic  acid,  and  the  soluble  part  oleic  acid. 
The  insoluble  part  seems  to  be  perfectly  inert,  at  least  in  cold  water ;  the  soluble  part 
on  agitation  in  pure  water  forms  a  foam  whose  numberless  vesicles  during  washing  take 
up  the  dirt  and  remove  it  from  the  articles  to  be  cleansed.  This  result  can  occur  only  when 
the  soap-lye  froths,  and  is  possible  only  when  the  existing  lime  and  magnesia  salts  have 
been  eliminated  as  insoluble,  smeary  compounds  of  fatty  acids.  In  the  decomposition 
31  parts  of  soda  and  47  parts  of  potassa  are  replaced  by  28  parts  of  lime  or  20  parts 
of  magnesia,  so  that  i°  of  hardness  destroys  about  120  milligrammes  of  good  curd 
soap,  or  i  litre  of  a  water  at  25°  hardness  3  grammes  of  soap ;  i  cubic  metre  of  the  same 
water  consequently  destroys  3  kilos,  of  soap. 

But  it  is  not  merely  the  direct  waste  of  soap  which  here  comes  into  play ;  the  lime 
and  magnesia  soaps  formed  obstruct  the  pores  of  the  skin  in  washing,  and  deposit  them- 
selves in  the  fibres  of  washed  goods,  especially  woollens,  which  consequently  lose  their 
softness  and  acquire  an  offensive  smell.  A  calcareous  or  magnesian  water,  therefore, 
before  being  used  for  fulling  cloths,  wool-scouring,  &c.,  as  well  as  in  the  laundry,  should 
be  heated  with  the  proportionate  quantity  of  soda  to  80°  or  100°  and  should  then 
be  decanted  away  irojn  the  sediment.  The  same  treatment  removes  the  compounds  of 
iron  and  manganese,  which  not  merely  destroy  soaps,  but  occasion  most  unpleasant 
stains. 


234  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

That  vegetables  cannot  be  boiled  tender  in  water  containing  much  lime  or  magnesia, 
but  remain  hard,  is  a  fact  which  has  been  known  for  above  a  century  and  which  first 
gave  such  waters  the  name  of  "  hard."  According  to  the  experiments  of  Bitthausen, 
there  is  formed  in  peas  boiled  in  hard  water  a  compound  of  legumin  with  lime  or 
magnesia  which  hardens,  on  boiling,  to  a  horny  consistence.  Similar  unpleasant  effects 
are  noticed  on  boiling  other  vegetables  and  meat  in  hard  waters.  It  is  also  well  known 
that  much  better  tea  and  coffee  can  be  prepared  with  soft  than  with  hard  water.* 

Water  used  for  baking  should  contain  no  putrescent  matters  which  interfere  with 
the  fermentation.  The  water  of  a  brook  near  Hanover  which  had  been  used  for  many 
years  in  baking  yielded  a  perfectly  useless  paste  as  soon  as  it  was  polluted  by  the  waste 
waters  of  a  sugar-works. 

Pettenkofer  and  Harz  suggest  the  possible  contamination  of  our  dwellings  by  the 
use  of  bad  water  in  washing  the  floors,  &c.  The  same  caution  must  be  kept  in  mind 
when  the  streets  are  sprinkled  with  polluted  waters. 

In  the  construction  of  houses  the  quality  of  the  water  used  for  slacking  lime, 
mixing  mortar,  and  steeping  bricks  is  important.  Bricks  often  display  whitish,  yellow, 
green,  and  even  black  eruptions.  The  white  efflorescences  consist  of  calcium,  magnesiiim, 
or  sodium  sulphates,  sodium  chloride  or  bicarbonate,  which  have  been  originally 
present  in  the  clay  and  have  been  introduced  by  the  water  used  in  building.  The 
green  eruptions  on  light-coloured  stones  are  mostly  algae ;  black  spots  such  as  may  be 
observed  on  the  Berlin  Synagogue  are  fungi  which  attach  themselves  only  where  efflores- 
cences of  calcium  carbonate  and  sulphate  appear  on  the  stones.  In.  rainy  weather 
such  of  the  above  salts  as  are  soluble  deliquesce,  rendering  the  walls  damp  and  spotty ; 
in  dry  weather  they  effloresce,  loosen  the  plaster  by  expansion  and  crystallisation  and 
cause  it  to  peel  off.  Still  more  objectionable  are  calcium  and  magnesium  chlorides, 
which  if  once  introduced  can  scarcely  ever  be  removed.  The  ceilings  sooner  become 
grey,  as  the  dust  clings  more  readily,  and  the  wall-papers  become  spotty. 

The  custom  of  filtering  impure  turbid  water,  in  the  erroneous  opinion  that  clear 
water  is  always  pure,  was  known  to  Pliny.  The  media  used  for  filtering  are  wool, 
sponge,  cellulose  (Piefke),  spongy  iron  (Bischof),  unglazed  porcelain  (Chamber-land), 
asbestos,  plastic  carbon,  silicated  carbon,  and  innumerable  others. 

As  a  specimen  of  a  small  domestic  instrument  of  this  kind  the  high-pressure  filter 
recently  introduced  by  Glover  may  be  mentioned.  The  water  enters  by  the  cocks 
A  and  G  (Fig.  222),  passes  into  the  ring-shaped  space,  G,  through  the  filtering 
material,  F,  and  flows  out  at  D.  In  order  to  remove  the  deposit  of  mud  the  water  may 
be  caused  to  flow  for  a  short  time  in  the  opposite  direction  by  closing  the  cocks  A  and 
G  and  opening  B,  so  that  the  dirt  is  carried  off  by  lateral  openings.  In  judging  filters 
it  must  be  considered  that  the  organic  impurities  contained  in  the  water  filtered  can  be 
diminished  only  by  absorption  and  oxidation.  The  absorptive  power  of  filtering 
materials,  with  the  exception  of  animal  charcoal,  is  inconsiderable. 

Even  this  last  material  does  not  retain  its  absorbent  powers  for  ever,  and  a  time 
comes  when  it  may  pollute  instead  of  purifying  water  passed  through  it.  Oxidation, 
as  it  takes  place  naturally  in  the  earth,  is  possible  only  with  an  abundant  access  of 
atmospheric  oxygen.  But  if  the  filter-bed  is  constantly  covered  with  water,  or  if  it  is 
closed  up,  only  the  oxygen  dissolved  in  the  water  itself  can  be  transferred  to  the 
organic  matter — of  course  a  limited  quantity. 

Hence  follows  a  necessity  for  the  frequent  airing  and  purification  of  all  household 
filters.  If  this  is  neglected  the  water  is  not  improved  by  filtration,  but  deteriorated. 
Filters  containing  organic  matter,  cotton,  felt,  wool,  sponge,  &c.,  cannot  be  recom- 

*  As  regards  tea,  this  dictum  may  be  questioned;  soft  water  extracts  more  readily  and 
abundantly  the  tannin  of  the  tea,  thus  rendering  the  infusion  less  pleasant  and  less  wholesome. — 
EDITOR. 


SECT.    III.] 


WATER   AND   ICE. 


235 


Fig.  222. 


mended,  as  they  promote  putrefaction.  The  recent  demand  that  organic  germs  should 
be  removed  from  the  water  is  fulfilled  by  some  ;  but  their  performance  is  very  slight. 

For  filtering  the  water-supply  of  entire  cities  large  sand-filters  are  used.  Fig.  223 
shows  the  section  of  the  filters  erected  in  Dublin  in  1869.  The  bottom  of  the  filters 
consists  of  a  bed  of  puddled  clay  f  metre  in  thickness,  a,  built  in  with  stones 
J  metre  in  thickness.  The  'filter-materials  laid  directly  upon  the  clay-bed  consist 
of  f  metre  of  coarse,  angular 
stones,  b,  15  centimetres  of  smaller 
stones,  c,  the  same  depth  of  coarse 
gravel,  d,  the  same  depth  of  fine 
sand,  e,  and  f  metre  (75  centi- 
metres) of  sand,  f.  To  collect  the 
water  there  are  two  channels,  B, 
situate  half  in  the  bed  of  clay  and 
half  in  the  stratum  of  large  stones. 
Each  channel  is  75  centimetres  in 
width  and  60  centimetres  in  depth. 
The  surface  of  sand  in  each  metre 
is  6 1  by  31  metres;  the  depth  of 
the  water  is  60  centimetres. 

The  speed  of  filtration  varies  in 
the  existing  sand-filters  from  i'4  to 
15  metres  per  twenty-four  hours. 

Each  water  requires,  if  it  is  to  be  well  filtered  by  a  given  kind  of  sand,  a  determined  speed 
of  filtration.  Thus,  under  otherwise  similar  conditions,  3*5  cubic  metres  of  Thames 
water  may  be  filtered  in  twenty-four  hours  per  square  metre  of  filtering  surface,  but  only 
1-7  cubic  metre  of  Elbe  water,  as  the  latter  contains  much  more  finely  divided  dirt.  In 

Fig.  223. 


a  well-managed  filtration  the  turbid  water  passes  so  slowly  through  the  sand  that 
each  of  the  fine  particles  of  dirt,  though  far  smaller  than  the  intervals  between 
the  grains  of  sand,  has  opportunity  to  attach  itself  to  one  of  the  grains.  Therefore, 
the  finer  and  more  numerous  the  particles  of  dirt  are,  the  finer  must  be  the  sand 
and  the  slower  must  be  the  rate  of  filtration.  If  this  rate  is  too  great,  the  sus- 


236 


CHEMICAL  TECHNOLOGY. 


[SECT.  iii. 


pended  particles  flow  simply  through  between  the  grains  of  sand.  But  if  the  sand  is 
too  fine,  the  filter-bed  may  easily  become  water-tight,  whilst  if  the  sand  is  too  coarse 
slower  filtration  is  to  some  extent  a  remedy.  The  best  size  of  the  sand  grains  is 
from  |  to  i  millimetre,  and  the  sand  is  the  better  the  more  uniform  the  grains  are. 
A  sand  containing  much  finer  grains  cannot  be  used,  as  it  is  easily  rendered  too 
compact  by  the  pressure  of  the  water. 

For  the  better  preservation  of  the  filter  it  is  requisite  that  the  suspended  dirt  should 
remain  in  the  upper  stratum  and  not  penetrate  into  the  loAver  layers.  This  easily 
happens  at  first  after  cleaning,  as  the  surface  of  the  sand  is  then  very  loose.  In  a  newly 
cleaned  filter  the  head  of  water  should  therefore  be  very  small.  When  once  a  film  has 
been  formed  over  the  surface  the  pressure  may  be  raised  to  i  metre ;  higher  pressures 
easily  break  up  the  bed. 

If  its  performance  has  become  too  slow,  the  filter  is  allowed  to  dry,  and  the  upper 
layer,  of  about  i  centimetre  in  thickness,  is  taken  off  and  washed.  There  is  often, 
especially  in  summer,  formed  upon  the  filter  a  layer  scarcely  i  millimetre  in  thickness, 
consisting  almost  entirely  of  Diatoniaceae  (Pleurosigma,  Synedra,  &c.),  and  rendering 
the  cleansing  of  the  filter  necessary  on  account  of  their  impermeability. 

The  effects  of  this  sand  filtration  are  confined  to  a  partial  oxidation  of  the  dissolved 
organic  matter,  and  the  separation  of  the  suspended  matter.  The  organic  germs  are 
especially  said  to  be  kept  back.  According  to  Koch,  filtered  water  should  not  contain 
more  than  300  germs  per  c.c. : — 


Day  of 
Examination. 
1885     June       2 

9 
16 

23 

J 

30 

ly     7 

14 

21 

28 

Stralau  AVer 

ks. 

Tcgel  Work 

i. 

Spree  Water. 

Lake  Water 

Unfiltered. 

Filtered. 

Unfiltered.             Filtered. 

5,475 

42 

IlS 

16 

7,980 

22 

117 

39 

6,100 

33 

115 

76 

6,100 

4i 

1,325 

194 

4,400 

53 

880 

44 

3,500 

28 

sample  lost     ... 

42 

7,200 

200 

1,896 

1  20 

110,740 

,656 

13:320 

49 

2,640 

54 

1,500 

48 

In  filtration  through  perfectly  clean  sand  the  swarms  of  bacteria  are  only  at  first 
a  little  checked  in  their  forward  movement,  but  they  afterwards  become  more 
numerous,  so  that  the  filtered  water  sometimes  contains  more  germs  than  the  un- 
filtered.  The  imperfection  of  the  action  slowly  disappears.  Sands  not  sterilised  act 
better  at  the  very  outset,  and  among  such  those  are  preferable  which  have  for  some 
time  taken  part  in  the  filtration  in  a  large  tank.  Externally  such  sand  was  perceived 
to  be  no  longer  sharp,  but  smeary  to  the  touch.  If  examined  under  the  microscope,  it 
was  found  that  the  single  grains  were  more  or  less  completely  coated  with  a  dirty  layer 
which  was  readily  destroyed  by  heat,  and  contained  a  little  ferric  oxide  along  with 
organic  matter.  That  this  coating  consisted  chiefly  of  bacteria  and  their  germs  was 
plainly  shown  on  bacteriological  examination.  If  a  sample  of  sand  was  taken  from 
any  of  the  filters,  well  rinsed  with  sterilised  water,  and  the  rinsings  subsequently 
examined,  bacteria  were  found  in  enormous  numbers.  The  entire  stratum  of  sand 
was  infected  with  them,  though  their  distribution  was  very  unequal,  decreasing  from 
the  surface  rapidly  at  first,  and  afterwards  more  and  more  slowly.  As  an  example, 
we  may  refer  to  a  large  sand  filter,  which  had  been  in  use  for  a  year  and  a  half. 
The  thickness  of  the  residual  bed  of  sand  was  30  centimetres.  On  cleansing  the  filter, 
there  were  found,  per  kilo,  of  sand : — 


SECT.    III.] 


WATER   AND   ICE. 


237 


1.  From  a  dirt  heap 5028  million  germs 

2.  From  surface  of  clean  filter 734 

3.  From  10  centimetres  depth  below  surface        .        .        .       190 

4.  From  20  centimetres  depth  below  surface        .         ,        .150 

5.  From  30  centimetres  depth  below  surface        ...        92 

6.  From  fine  gravel  below  sand 68 

The  residue  left  on  the  surface  of  the  sand  after  the  filtration  of  Spree  water  is,  by 
reason  of  its  peculiar  composition,  almost  exclusively  of  organic  matter,  to  be  regarded 
as  a  culture  medium  in  which  the  introduction  of  germs  keeps  up  a  process  of  putre- 
faction, regulated  according  to  the  temperature.  The  first  result  is  a  great  increase  in 
the  micro-organisms.  Many  of  them  are  endowed  with  the  power  of  motion ;  others 
with  the  property  of  liquefying  any  gelatinous  nutrient  matter.  They  are,  there- 
fore, able  to  break  off  their  connection  with  their  covering  of  dirt,  and  to  leave  it 
in  great  numbers.  Nothing  further  stands  in  the  way  of  their  forward  movement. 
The  sterilised  sand  cannot  arrest  them ;  nothing  clings  to  its  smooth  grains,  and  thus 
we  understand  the  phenomenon,  at  first  so  puzzling,  that  in  filtering  Spree  water  for  a 
long  time  through  sterilised  sand,  we  do  not  find  a  decrease  of  micro-organisms.  Upon  a 
filter  perfectly  sterilised  by  strong  heat,  and  filled  up  with  sterile  water,  Spree  water 
was  poured,  and  its  filtration  was  commenced  after  standing  for  one  day.  There  were 
found  germs  capable  of  development : — 


Before  After 

Filtration.  Filtration. 

2nd  day        .     13,500  ...        97,9oo 

6th    ,,          .     13,860  ...      205,000 

loth     „          .      3,120  ...         17,825 


Before  Af 

Filtration.  Filtration. 

i2th  day      .     1,320  ...        29,900 

i6th    „          .     1,803  ...          4,928 

22nd  „         .     1,120  ...          2,356 


Results  of  this  kind  cannot  happen  after  the  sand  has  become  slimy.  For  as  soon 
as  the  micro-organisms  have  left  their  focus,  the  covering  of  dirt,  they  enter  regions 
which  are  for  them  almost  impassable,  since  they  present  everywhere  points  of  attach- 
ment. With  few  exceptions,  they  cannot  penetrate  deeply  into  the  sand,  and  collect 
in  the  upper  layers  in  vast  multitudes.  Hence  the  question  as  regards  the  admissible 
speed  of  filtration  acquires  a  new  significance ;  we  must  not  let  the  stream  become  strong 
enough  to  wash  away  any  great  number  of  germs  from  the  layers  of  sand.  The  question 
now  is,  how  far  we  are  to  take  the  demands  of  public  health  into  consideration.  If 
we  insist  upon  the  greatest  possible  freedom  from  germs  the  rate  of  filtration  must  not 
exceed  30  millimetres  hourly.  If  we  are  content  with  results  like  those  effected  at 
Stralau  works,  we  may  admit  60  to  80  millimetres.  But  to  go  beyond  100  millimetres 
would  be  admissible  only  under  conditions  which  would  be  presented  by  new  works 
constructed  with  great  care. 

However  important  is  the  elimination  of  germs,  it  must  not  be  forgotten  that  we 
are  unfortunately  not  always  in  a  position  to  distinguish  the  germs  of  specific  diseases 
from  others  which  are  harmless.  When,  therefore,  no  water  from  unimpeachable 
springs  or  deep  wells  is  at  hand,  it  is  advisable  always  to  boil  water  before  use,  even  if 
it  has  been  filtered. 

Softening  Water. — The  Clarke  Process. — For  softening  waters  intended  for  tech- 
nical purposes  the  following  methods  may  be  adopted. 

On  heating  water,  the  calcium  and  magnesium  bicarbonates  are  decomposed,  the 
so-called  half-combined  carbonic  acid  escapes,  whilst  calcium  and  magnesium  carbonates 
are  precipitated,  only  about  35  milligrammes  calcium  and  100  milligrammes  magne- 
sium carbonate  remaining  in  solution.  The  so-called  temporary  hardness  of  the  water 
is  thus  much  reduced.  Movement  promotes  th^  separation.  If  the  water  contains 
iron  as  ferrous  bicarbonate,  it  is  separated  out  as  ferric  hydroxide. 

If  steam  is  available,  as  is  generally  the  case  in  manufactories,  it  may  be  advan- 


238 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


tageously  brought  into  direct  contact  with  the  water  as  in  Fig.  224.  The  steam  enters 
through  the  pipe  e,  and  the  part  not  condensed  escapes  by  the  pipe  f .  The  water 
entering  at  the  pipe  c  flows  if  the  cock,  b,  is  properly  turned  over  the  plates,  d,  and 
escapes,  when  purified,  at  g. 

The  same  result  is  obtained  by  the  addition  of  milk  of  lime  : 

H2Ca(C03)2   +    Ca(OH)2    ..    2CaCO3    +    2H2O. 

At  the  same  time  the  magnesium  bicarbonate  is  decomposed  with  the  separation  of 
magnesium  hydroxide. 

A  well-water,  which  had  to  be  used  for  feeding  a  steam-boiler,  and  for  brewing, 
was  heated  to  40°  to  50°  by  the  waste  steam  of  a  steam- 
Iig.  224.  engine.     It  was  then  mixed  in  an  open  cistern,  holding 

6  cubic  metres,  with  a  quantity  of  slacked  lime  (ascer- 
tained by  previous  experiments),  made  up  to  a  stiff  paste, 
the  whole  thoroughly  stirred  up  and  used  after  the  pre- 
cipitate had  settled.  The  analysis  of  this  water  before 
(I.)  and  after  (II.)  the  treatment  with  lime,  showed  the 
following  composition  per  litre  : — 


I. 

11. 

Chlorine   . 

.     152 

153  milligrammes 

Sulphuric  acid  . 

.     216 

208 

Nitric  acid 

;      71 

70 

, 

Nitrous  acid 

.     trace   '  ... 

trace 

, 

Ammonia 

slight  trace  .  .  . 

o 

,    • 

Organic  matter 

.       51 

28            .., 

, 

Lime 

.     322 

172 

, 

Magnesia  . 

.       45 

7 

, 

Precipitable  on  boiling — 
Lime         .        .        .176 


trace 


Care  must  be  taken  that  an  excess  of  lime  is  not 
introduced,  as  water  so  treated  forms  a  bad  crock. 

The  method  of  purifying  waters  with  magnesia,  as 
proposed  by  Bohlig,  is  expensive,  questionable  for  steam 
boilers,  and  for  other  purposes  worthless. 

The  action  of  caustic  soda  is  similar,  but  the  sodium 
carbonate  formed  decomposes  simultaneously  a  corre- 
sponding quantity  of  the  other  calcium  salts.  In  most 
cases  the  use  of  sodium  carbonate  is  the  more  advantageous.  Calcium  sulphate  is  decom- 
posed with  sodium  carbonate  as  follows  : — 

CaS04  +  Na2CO3  =  CaCO3  +  Na2SO4. 

The  reaction  with  the  other  calcium  and  magnesium  compounds  is  similar;  these 
metals  are  precipitated  as  carbonates  with  the  simultaneous  formation  of  easily  soluble 
sodium  salts.  If  the  water  contains  a  large  quantity  of  bicarbonates  and  of  magnesium 
compounds,  the  cistern,  A  (Fig.  225),  made  of  boiler  plate,  and  holding  from  2  to  8  cubic 
centimetres,  is  run  half  full  of  water,  which,  if  practicable,  is  previously  heated  from 
thirty  to  forty  minutes  by  the  waste  steam  of  the  engine.  The  quantity  of  slacked  lime 
necessary  for  the  entire  precipitation  is  then  added  (preferably  in  the  form  of  a  stiff 
paste),  and  the  weighed  quantity  of  sodium  carbonate ;  the  valve,  b,  of  the  Korting 
blast,  B,  is  then  opened,  so  that  the  air  drawn  in  at  a,  ancl  escaping  from  the  perforated 
tube,  i,  may  mix  the  liquid  thoroughly.  The  rest  of  the  water  is  run  in,  and  after  about 
five  minutes  the  blast  is  cut  off.  In  from  ten  to  twenty  minutes  the  water  becomes 
perfectly  clear.  The  clearing  is  expedited  if  a  portion  of  the  precipitate  from  former 
operations  is  left  in  the  cistern. 

The  softened  water  should  turn  good  red  litmus-paper  blue  in  about  twenty  seconds, 


SECT.   III.] 


WATER   AND   ICE. 


239 


and  should  give  only  a  very  slight  turbidity  with  oxalic  acid.     It  is  then  not  merely  fit 

for  steam  purposes,  but  for  washing,  cooking,  brewing,  and  other  technical  uses an 

advantage  not  shared  by  other  methods. 

According  to  the  process  of  E.  de  Haen,  water  is  mixed  with  the  proportions  of 
barium  chloride  needed  for  precipitating  the  sulphuric  acid  : 

CaSO4  +  Ba012  =  CaCl2  +  BaSO4. 

Milk  of  lime  is  then  added  to  dispose  of  the  bicarbonates.  The  proposal  has  given 
satisfaction  for  the  feed-water  of 

steam-boilers,  as  the  formation    of  Fig.  225. 

crock  is  thus  prevented;  for  other 
purposes  it  is  not  applicable. 

In  comparing  the  cost  of  these 
precipitants  it  must  be  remembered 
that  80  parts  sulphuric  acid  (SO3), 
or  136  parts  calcium  sulphate  re- 
quire 208  parts  barium  chloride  or 
1 06  sodium  carbonate  for  decom- 
position. At  equal  market  prices  for 
both  precipitants,  barium  chloride 
is  therefore  twice  as  expensive  as 
soda. 

Distillation.  —  The  removal  of  ; 
the  mineral  and  other  non-volatile  \ 
impurities  of  water  by  distillation 

is  especially  important  for  chemical  processes  and  for  the  water-supply  of  ships.  On 
the  small  scale,  this  is  generally  effected  by  means  of  a  copper  still,  the  vapours, 
as  they  ascend,  being  condensed  in  a  worm  kept  cool  by  means  of  water.  A  violent 
ebullition  of  the  water  is  to  be  avoided,  lest  particles  of  water  are  carried  over 
mechanically  and  find  their  way  into  the  receiver.  Further,  the  water  which  passes 
over  first  contains  any  ammonia  which  may  be  present.  The  distillation  must  also 
not  be  carried  to  the  end,  as  otherwise  the  organic  matter  present  and  certain  salts 
will  be  decomposed.  In  order  to  obtain  water  as  near  as  possible  of  an  absolute  purity, 
it  is  first  mixed  in  a  still  with  potassium  permanganate  and  a  little  caustic  potassa  and 
heated  to  boiling  in  a  still.  As  soon  as  the  water  boils  the  fire  is  reduced,  to  prevent  the 
liquid — which  froths  much  at  first — from  boiling  over,  and  the  boiling  is  then  continued 
hi  the  ordinary  manner.  After  about  ^  of  the  water  has  been  evaporated,  the  condensed 
water  obtained  is  free  from  all  foreign  matter,  organic  or  inorganic,  if  the  worm  is 
fitted  with  an  arrangement  to  keep  back  water  from  being  carried  over  mechanically. 

To  purify  sea-water  by  distillation,  it  must  be  remembered  that  very  little  fuel 
should  be  used,  that  the  apparatus  must  take  up  only  a  small  space,  and  that  the 
water  obtained  must  be  rendered  in  some  measure  palatable  by  the  removal  of  the  so- 
called  "  still-taste."  The  ships  of  the  German  Navy  are  provided  with  stills  which 
can  furnish  daily  from  1*25  to  5  cubic  metres  of  distilled  water.  As  shown  in  the 
two  sections  (Figs.  226  and  227),  supposed  to  be  at  right  angles  to  each  other,  the 
apparatus  consists  of  two  cylinders,  A  and  B,  0-4  metre  in  width.  The  steam  for 
heating,  which  is  produced  in  a  special  boiler,  passes  through  the  pipe  d,  into  the  net 
of  tubes  of  the  cylinder  A,  surrounded  by  the  water  which  is  to  be  distilled.  The 
condensed  water  collects  in  the  recipient,  e,  and  flows  from  here,  the  steam  being  kept 
back,  into  g,  from  which  it  is  let  off  by  a  cock,  if  it  is  to  be  used  hot,  whilst  the  rest 
flows  through  the  tube  v,  to  the  refrigerator,  o. 

The  level  of  the  water  to  be  distilled  is  observed  by  a  gauge.  It  is  previously 
heated  in  the  cooling  vessel,  B,  and  flows  through  the  tube  1,  in  such  a  manner  that 


240 


CHEMICAL  TECHNOLOGY. 


[SECT,  in, 


the  steam  formed  must  first  pass  over  the  copper  sieve-plate,  a,  and  then  impinge  on 
the  plate,  c,  in  order  to  get  rid  of  any  sea- water  which  might  be  carried  over,  before  it 
arrives,  through  the  tubem,  at  the  tube-refrigerator,  n.  The  water  may  be  either  let 
off  directly,  or  may  pass  through  a  filter  filled  with  animal  charcoal. 

The  requisite  condensing  water  enters  by  the  tube  i,  and  flows  off  through  k,  after 
the  portion  required  for  distillation  has  been  conveyed  away.  The  air  which  escapes 
on  heating  from  the  condensation  water  is  conveyed,  through  the  pipe  t,  into  the  steam- 
chamber  of  the  distilling  apparatus,  so  that  it  may  dissolve  in  the  water  condensed 
here  from  the  steam,  and  render  it  palatable.  Through  g  the  steam  of  the  steam- 
pump  is  caused  to  enter. 

Vis.  226. 


Water  Mains. — Good  water  mains  must  be  chemically  and  physically  as  inactive 
as  possible.  They  must  not  impart  to  the  water  on  its  transit  any  hurtful  (poisonous) 
metals  or  unpleasant  properties  (decayed  wood),  and  they  should  not  be  attacked  and 
destroyed  either  by  the  water,  by  the  moisture  of  the  soil,  or  by  any  other  external 
agencies.  A  low  power  of  conducting  heat  is  also  desirable,  so  that  they  may  resist 
both  the  heat  in  summer  and  the  cold  in  winter.  Water  pipes  must  be  perfectly 
tight,  and  must  be  able  to  withstand  both  internal  and  external  pressure. 


SECT,  m.]  ARTIFICIAL  MINERAL  WATERS.  241 

Wooden  pipes  are  apt  to  give  the  water  aii  unpleasant  taste,  and  they  are  not 
durable. 

Mains  of  paper,  saturated  with  coal-tar  or  asphalt,  are  said  to  be  durable,  but 
they  have  not  come  into  extensive  use. 

Earthenware  pipes  may  be  recommended  where  there  is  no  danger  of  shocks  or  of 
excessive  pressure.* 

Cast-iron  mains  must  be  tarred  whilst  hot,  as  they  may  be  otherwise  much 
obstructed  by  rust,  or  may  be  corroded.  Iron  pipes  coated  with  zinc  answer  well  with 
some  waters,  but  in  presence  of  chlorides  they  are  corroded.  Iron  mains  have  also  been 
lined  with  certain  enamels. 

For  conveying  the  water  into  and  within  houses  tin  pipes  are  very  good,  but  too 
costly. 

Lead  piping  is  more  generally  used  in  houses.  It  was  employed  by  the  ancient 
Romans,  who,  however,  observed  that  lead  is  sometimes  attacked  by  water. 

Lead  pipes  should  be  protected  from  contact  with  lime  and  cement,  by  which  they 
are  rapidly  destroyed.  Water  dissolves  lead  if  it  contains  free  carbonic  acid  or  ammonia  ; 
chlorides,  nitrates,  and  organic  acids  promote  the  corrosion  of  lead,  but  calcium  carbonate 
or  dissolved  silica  prevents  the  attack.  Lead  pipes  are  sometimes  attacked  by  water  when 
first  laid  down,  but  there  is  soon  formed  an  insoluble  inner  layer  which  protects  the 
metal  from  further  attack.  As  a  rule  the  use  of  lead  piping  seems  free  from  objections ; 
the  decision  when  and  where  they  may  be  used  with  safety  must  depend  on  an  analysis 
of  the  water,  f 

ARTIFICIAL  MINERAL  WATERS. 

Among  the  substances  used  in  the  production  of  such  liquids,  the  water  itself  is  of 
the  greatest  importance.  Those  intended  for  medical  use  should  be  prepared  from 
distilled  water  only.  Those  which  serve  merely  as  beverages  may  be  made  from  an  irre- 
proachable drinking  water.  J  Certain  ignorant  or  reckless  manufacturers  use  impure  well- 
or  river-waters  if  near  at  hand.  It  has  been  proved  that  the  schizomycetes  of  Selters- 
waters  (commonly  called  Seltzer)  remain  capable  of  development  even  after  the  lapse 
of  seven  months.§  The  carbonic  acid  must  be  pure.  According  to  the  equation : 
MgC03  +  H2S04  =  MgS04  +  H20  +  C02,  84  grammes  magnesite  and  98  grammes  sulphuric 
acid  yield  120  grammes  magnesium  sulphate,  or  246  grammes  Epsom  salts,  and  44 
grammes  or  22-3  litres  carbonic  acid.  The  same  quantity  of  carbonic  acid  is  obtained 
from  100  grammes  pure  marble  or  pure  chalk,  whilst  of  dolomite  there  are  needed  90  to 
95  grammes.  In  the  choice  of  carbonates  it  must  be  considered  that  magnesite  yields 
far  the  best  carbonic  acid  ;  marble  sometimes,  dolomite  often,  and  chalk  always  contain 
organic  matter  which  gives  the  carbonic  acid  an  unpleasant  smell,  and  which  can  only 
with  difficulty,  if  at  all,  be  removed  by  the  use  of  potassium  permanganate  and  carbon. 
The  development  of  carbonic  acid  from  magnesite  and  sulphuric  acid  is  the  most  regular. 
Chalk  and  marble  must  be  finely  pulverised  and  well  stirred  up  if  the  decomposition  by 
sulphuric  acid  is  to  be  at  all  complete.  Magnesite  only  requires  a  free  room  of  50  per 
cent,  of  the  entire  capacity  of  the  generator  to  prevent  overflowing,  whilst  chalk  needs 
fully  75  per  cent. 

The  sulphuric  acid  used  must  be  free  from  arsenic,  and  must  contain  neither 
sulphurous  acid  nor  the  nitrogen  oxides. 

The    manufacture    is    generally    effected    by  saturating  water   (mixed    with   th& 

*  Glass  mains  have  been  tried  experimentally,  and  may  possibly  prove  successful. 

t  Gutta-percha  pipes  are  free  from  objection  from  a  sanitary  point  of  view,  and  are  less  likely 
to  freeze  in  winter  than  those  of  lead  or  tin.  But  when  alternately  wet  and  dry  they  gradually 
lose  their  cohesion,  and,  like  those  cf  lead,  they  are  sometimes  attacked  by  rats. 

+  Such,  e.g.,  as  that  of  Loch  Katrine,  or  the  Clarkised  Chiltern  Hill  water. 

§  Very  bad  mineral  waters  have  been  exported  to  India. 

Q 


242  CHEMICAL   TECHNOLOGY.  [SECT.  HI. 

necessary  ingredients)  with  carbonic  acid.  This  is  done  under  pressure  in  appro- 
priate apparatus,  and  the  mineral  water,  when  ready,  is  at  once  filled  into  bottles 
which  are  closed  air-tight.  The  carbonic  acid  gas  is  either  forced  into  the  water 
by  pumps,  or  it  is  generated  in  closed  apparatus  and  driven  in  by  its  own  pressure. 
Latterly  liquefied  carbonic  acid  has  been  used  with  advantage. 

It  must  be  remembered  that  all  the  beverages  containing  carbonic  acid  should  be 
kept  from  contact  with  lead  or  copper  vessels,  unless  well  tinned,  as  they  will  otherwise 
dissolve  considerable  quantities  of  the  poisonous  metals. 

Ice. — Ice,  or  some  form  of  artificial  cold,  is  indispensable  for  breweries,  parafBne 
works,  for  the  production  of  Glauber  salts  from  the  mother  liquors  of  littoral  salines 
and  Stassfurt  salts,  and  for  many  other  installations.  Natural  ice  is  often  plentifully 
stored  with  bacteria,  and  artificial  ice  should  therefore  be  substituted  if  possible. 

There  are  two  processes — change  of  the  condition  of  aggregation,  and  expansion  of 
volume — by  which  heat  is  taken  up.  Hence  we  may  produce  cold  in  the  three  follow- 
ing manners : — 

1.  By  liquefaction  of  a  solid  by  means  of  a  liquid  (solution  of  salts)  or  of  another 
solid  (salt  and  snow) — that  is,  by  means  of  so-called  freezing  mixtures. 

2.  By  converting  a  liquid  body  (ether  or  ammonia)  into  a  gaseous  condition. 

3.  By  the  expansion  of  compressed  air. 

The  two  latter  procedures  only  can  come  into  question  on  a  large  scale,  though 
mixtures  of  snow  with  dilute  acids  may  be  made  to  produce  intense  cold  on  a  small 
scale.  In  this  manner  Faudel  obtained  a  temperature  of  -  60°  with  sulphuric  acid 
of  65  per  cent,  which  he  had  caused  to  ascend  through  a  cooling-tube  within  a 
column  of  snow  and  to  flow  out  at  the  top. 

Evaporation  Ice  Machines. — The-boiling  point  of  liquids  depends  on  the  pressure 
of  the  atmosphere  or  gas  which  rests  upon  them.  If  this  is  reduced  the  temperature  at 
which  the  liquid  evaporates  is  reduced  also.  If  no  heat  is  conveyed  from  without, 
that  needed  for, gasification  must  be  taken  from  the  liquid  itself,  and  its  temperature 
must  fall  the  lower  the  less  the  pressure  and  the  lower  its  boiling-point.  The  following 
table  shows  the  relations  of  the  bodies  which  here  come  into  question. 


Pressure  in  Atmospheres. 


Temperature. 
-80°       . 
-20 
-  10 
O 

+  JO 
+  20 
+  30  • 


Carbonic 
Acid. 

I'D 

Sulphurous 
Acid. 

Ammonia. 

Methyl- 
chloride. 

Methyl- 
ether. 

Ethyl- 
ether. 

I9-9 

0-6 

1-8 

T2 

1-2 

0-09 

26-8 

I'D 

2-8 

17 

17 

0-15 

35'4 

i'5 

4'2 

2-5 

2'5 

0*24 

46'  I 

2-3 

6-0 

3'5 

3'4 

0-38 

58-8 

3'2 

8-4        ... 

4-8        ... 

47 

0-57 

73-8 

4-5 

ii'S 

6'3         .- 

0-80 

Hence,  the  greatest  cold  is  to  be  produced  with  liquid  carbonic  acid ;  then  follow 
ammonia,  methyl-chloride,  and  methyl-ether  ;  next  sulphurous  acid,  whilst  ethyl-ether 
produces  cold  only  under  a  reduced  pressure. 

Still  less  favourable  is  water,  which  at  o°  has  a  tension  corresponding  to  4-6  milli- 
metres of  mercury,  and  can  consequently  be  cooled  down  to  o&  only  in  an  almost 
complete  vacuum.  Still,  of  late,  large  ice  machines-  h\ve  been  constructed  in  which 
water  is  frozen  by  rapid  evaporation.  To  effect  this  tjie  air  is  drawn  off  as  far  as 
possible  from  the  containing  vessels,  and  the  watery  vapours  formed  are  absorbed  by 
concentrated  sxilphuric  acid. 

The  machines  with  liquid  ammonia,  sulphurous  acid,  and  carbonic  acid  are  the 
most  important.  They  consist,  as  it  is  diagrammatically  shown  in  Fig.  228,  mainly  of 
the  evaporator,  A,  in  which  the  liquid  concerned  vaporises  and  withdraws  the 


SECT.    III.] 


ARTIFICIAL   MINERAL  WATERS. 


243 


requisite  heat  from  the  solution  of  magnesium  chloride  circulating  in  the  pipes.  The 
pump,  B,  draws  the  gas,  forces  it  into  the  cooler,  C,  in  which  it  is  again  liquefied,  and 
conveys  the  heat  liberated  to  the  refrigerating  water.  The  cock,  D,  regulates  the 
reflux  to  the  evaporator,  A. 

As  an  instance  may  be  taken  Pictet's  machine  (Fig.  229),  which  uses  a  mixture  of 
sulphurous  acid  and  carbonic  acid,  as  is  alleged,  in  the  molecular  combination,  CSO4. 
Fig.  228. 


The  cylinder,  a,  of  the  steam- 
•engine,  drives  directly  the  forcing- 
pump.  On  each  of  its  covers  there 
.are  two  suction-valves  and  two  pres- 
sure-valves, d.  The  valves  on  both 
sides  are  connected  with  each  other 
by  a  pipe.  Above  each  of  these  two 
connecting-tubes  there  is  a  valve, 
VjVjj,  which  can  be  shut  perfectly 
air-tight.  The  water  for  the  cooling- 
jacket  of  the  pressure-cylinder  and 
the  perforated  piston-rod  arrives  and 
is  carried  off  by  flexible  tubes,  g. 
The  refrigerator,  C,  consists  of  two 
iron  holders,  and  the  worms.  The 
former  are  set  in  each  other  so  that 
they  have  one  side  on  the  bottom 
in  common.  The  seamless  worms 
of  iron,  or  copper,  all  run  above 
and  below  each  into  a  large  hori- 
zontal main,  hl  and  h2,  which  are 
again  connected  by  two  vertical  tubes, 
•  h3  and  ht.  The  liquid  coming  from 
the  condenser  is  led  below  into  the 
refrigerator  by  the  tube,  r,  fills  the 
lower  horizontal  tube,  a  part  of  the 
vertical,  and  of  the  worm,  and  is 
again  drawn  off  in  a  gaseous  form 
through  the  tube,  r,  by  means  of  the  forcing-pump.  The  valve  V3  and  the  entrance 
cock,  V4,  allow  of  the  whole  system  being  closed  air-tight. 

The  salt  water  flowing  round  the  latter  is  kept  in  motion  by  the  screw,  e.  This 
salt  water,  which  is  cooled  down  by  the  development  of  cold  which  proceeds  in  the 
worms,  is  conveyed  by  special  conductors  into  the  fermenting  and  storage  cellars 
\(i.e..  supposing  the  machine  is  in  use  in  a  brewery),  and  returns  to  the  refrigerator, 


244  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

heated  several  degrees.  Iron  cells,,/,  can  be  suspended  between  the  worms,  in  which 
water  is  allowed  to  freeze.  In  the  space  between  the  two  holders  there  is  pure  water,  F, 
which  covers  the  outer  surface  of  the  internal  holder  partly  in  the  form  of  ice,  G-.  This 
cold  pure  water  serves  to  circulate  in  the  beer  coolers  and  fermenting  vats. 

The  condenser,  D,  likewise  consists  of  an  iron  receiver  and  a  system  of  worms.  The 
parallel  worms  discharge  above  and  below  into  upright  collecting  tubes,  h5  and  h6.  The 
compressed  gases  enter  the  condenser  through  the  pipe,  r2,  and  are  liquefied.  The  liquid 
collects  at  the  bottom  of  the  tube,  hv  and  rises  up  through  a  narrower  tube,  r,  which 
extends  to  the  bottom  of  this  large  pipe.  This  pipe  conveys  the  liquid  through  the 
regulator,  E,  to  the  cooler.  The  condensing  worms  are  closed  perfectly  air-tight  by 
the  valve  V5  and  the  cock  V6.  The  cooling-water  enters  the  condenser  below  through 
a  pipe,  i,  traverses  all  the  rows  of  worms,  and  flows  off  at  the  top  through  a  perforated 
collecting-tube,  K. 

The  regulator  is  introduced  into  the  tube,  which  leads  the  volatile  liquid  from  the 
condenser  to  the  cooler  after  it  has  been  liquefied.  The  bye-cocks,  V7  and  V8, 
attached  to  the  main  cock,  allow  the  liquid  to  be  introduced  into  the  apparatus  and  to- 
draw  it  out  of  the  machine. 

The  latent  boiling-heat  of  the  liquids  concerned  is  per  kilo. :  ammonia,  315  ;  methyl- 
ether,  130  ;  sulphurous  acid,  94  ;  ethyl-ether,  90  ;  carbonic  acid,  84  heat-units  (calories). 
On  account  of  the  different  specific  heats  and  densities,  the  proportionate  sizes  of  the 
machines  are  as  follows  :  That  of  the  ammonia-machine  (according  to  Linde)  =  i  ; 
ethyl-ether,  i2'2;  sulphurous  acid,  2^5 ;  methyl-ether  1*5  ;  carbonic  acid,  0-17. 
Theoretically,  therefore,  carbonic  acid  is  the  most  advantageous.  Trustworthy  com- 
parative experiments  are  still  wanting. 

Cold-air  machines  are  to  be  preferred  only  where  rooms  have  to  be  cooled  and  ven- 
tilated at  the  same  time. 

SULPHUR. 

Sulphur  occurs  native  in  gypsum  and  in  the  connected  beds  of  clay  and  marl,  in< 
the  flb'tz  and  the  tertiary  formation,  more  rarely  in  veins  in  the  crystalline  slate  and 
transition  formations,  occasionally  in  lignite  and  coal.  It  is  also  found  as  a  sublimation 
product  from  volcanoes,  as  in  the  Solfatarae  of  Naples.  It  is  most  common  in  veins 
and  deposits  in  Sicily,  which  supplies  nearly  all  Europe  with  sulphur ;  in  the  Caucasus  ; 
in  Egypt,  on  the  coasts  of  the  Red  Sea,  and  especially  of  the  Gulf  of  Suez  ;  in  the  Ionian 
Islands  (especially  Corfu),  in  the  Clear  or  Borax  Lake  in  Nevada ;  in  Popocatepetl  in 
the  Mexican  province  of  Puebla,  where  above  100  tons  of  sulphur  are  collected  yearly, 
and  at  Krisuvik  in  Iceland.  Sulphur  is  plentifully  found  at  Swoscowice  near  Cracow, 
deposited  in  the  marl.  It  occurs  also  on  a  large  scale  in  New  South  Wales.  Sulphur  is 
deposited  from  mineral  springs,  and  occurs  in  combination  with  metals,  as  iron,  and 
copper  pyrites,  galena,  blende,  &c.,  also  oxidised  to  sulphuric  acid  in  anhydrite,  gypsum, 
kieserite,  heavy-spar,  &c. 

Extraction. — Volcanic  sulphur  is  obtained,  according  to  the  nature  and  the  richness  of 
the  minerals — either  by  fusion  or  distillation.  If  the  raw  materials  are  rich  the  sulphur  is 
extracted  by  melting  in  an  iron  pan,  A  (Fig.  230),  which  is  gently  heated  by  a  fire  on 
the  grate,  B.  After  the  sulphur  is  melted  the  stony  matter  is  skimmed  out  with  the 
ladle,  (7,  and  the  sulphur  is  poured  into  a  dish  moistened  with  water  or  into  a  sheet 
iron  pan,  D.  When  cold  the  mass  of  sulphur  is  broken  up  and  packed  in  casks  for  the 
market.  The  stony  matter,  as  well  as  the  poorer  sulphur  minerals,  are  melted  in 
heaps  or  shaft  furnaces  (Fig.  231),  apart  of  the  sulphur  serving  as  fuel.  A  small 
quantity  of  impure  sulphur  is  burnt  in  the  support  of  this  furnace,  and  the  shaft,  E,  is 
gradually  filled  with  coarse  pieces  of  the  earthy  sulphur,  which  soon  take  fire  on  the  top 
and  allow  the  melting  sulphur  to  escape.  The  openings,  /,  let  in  the  air  necessary 


SECT.   III.] 


SULPHUR. 


245 


231. 


Fig.  230. 


for  the  combustion  of  a  part  of  the  sulphur.     The  melted  sulphur  which  collects  at  the 
lower  part  of  the  shaft  is  let  off  through  the  channel,  </,  into  wooden  or  iron  vessels. 
Sulphur  can  be  melted  in  clamps  better  than  in  shaft  furnaces.     There  are  no  fewer 
than  630  sulphur  mines  at 
present  in  work  in  Italy. 
In  many  the  operation  is 
effected  in  the  most  primi- 
tive manner  by  melting  out 
a  part  of  the  sulphur  by 
means  of  burning  sulphur. 
This  is   effected   in   Sicily 
with  an  average  loss  of  50 
per  cent,  of  the  total  sul- 
phur, and  in  the  Romagna 


with  a  loss  of  43  per  cent. 
Other  methods  of  extrac- 
tion have  only  met  with  a 
very  limited  adoption. 

Far  better  is  the  distillation  process,  in  which  a  real  distillatory  apparatus  is  now  used 
{Fig.  232).  A  cast  iron-pan,  A,  is  filled  with  the  raw  material  and  closed  with  an  iron 
•cover.  The  manner  of  heating  and  the  way  which  the  products  of  combustion  take 

round  the  pan  and  the  preliminary 
heater,  D,  can  be  perceived  from 
the  figure.  The  vapours  of  sulphur 
escape  through  the  iron  pipe,  ra, 
into  the  condenser,  £,  from  which 
the  liquid  sulphur  runs  into  the 
vessel,  k.  .  The  material,  which  has 
been  previously  warmed  in  D,  is  let 
fall  into  the  pan  of  the  still  (which 
has  been  emptied  in  the  meantime) 
by  withdrawing  a  slide  at  p. 

For  extracting  the  sulphur  from 
Italian  ores,    Balard   recommended 


Fig.  232. 


in  1867  a  solution  of  salt.    Dubreuil 
used  a  solution  of  calcium  chloride, 

a  procedure  which  had  been  carried  out  practically  by  Ch.  Deperais  in  1868.    For  some 
years  sulphur  has  been  eliquated  from  its  ores  by  means  of  steam,  at  130°.     According 
to   Gerlach's  proposal,  which  has  not  been  successful,   the  sulphur  ores  are  heated 
with  the  simultaneous  introduction  of   superheated   steam.     The   extraction   of  the 
mineral  with  carbon  disulphide  has  also  found  a  restricted  application. 

The  Sicilian  raw  sulphur,  as  obtained  by  the  fusion-process,  had  the  following  com- 
position : 

i.  ii.  in.  iv.  v. 

Sulphur,  soluble  in  C82  .    90'!        ...        96-2        ...        91*3        ...        9O'o        ...        887 
Carbonaceous  matter     .       ro         ...  o-5         ...          07         ...  ri         ..  ro 

Sulphur  insoluble  in  CS.,      2-o        ...  ...          i-5        •••          2-i        ...          17 

Sand       ....      2-3        ...          1-5        ...          3-3        ...          2-8  5-5 

Limestone      .        .        •      4'i         ...          i'8        ...          2-5        ...          3-o        ...          2-8 
Loss    .        .        .  o-5        ...  ...          07        ...          ro        ...          0-3 

Refining. — The  bottoms  of  the  loaves  of  raw  sulphur  contain  as  much  as  25  per 
cent,  of  foreign  matter.  In  order  to  free  it  from  the  earthy  parts  the  crude  sulphur 
is  refined  and  comes  into  the  market  either  as  roll  sulphur  or  as  flowers  of  sulphur. 


246 


CHEMICAL   TECHNOLOGY. 


[SECT.  iii. 


The  apparatus  for  refining  sulphur,  constructed  by  Michel,  of  Marseilles,  and  im- 
proved by  Lamy,  consists  of  one  or  of  two  cast-iron  cylinders,  B  (Fig.  233),  which 
serve  instead  of  a  retort,  and  a  large  chamber,  G,  which  acts  as  a  receiver.  The  first 
cylinder,  S,  is  heated  by  the  fire  below.  The  flame  plays  round  the  cylinder  and  escapes, 
along  with  the  gases  of  combustion,  through  the  chimney,  E,  after  having  first  given  off 
a  part  of  their  heat  to  the  pan,  2),  through  the  flues,  C.  Here  the  sulphur  undergoes  a 
preliminary  purification  and  flows  through  the  pipe,  F,  into  the  cylinder,  E,  which 
opens  into  the  large  vaulted  chamber  of  brick.  At  one  end  of  this  chamber 
(not  shown  in  the  figure)  there  is  a  doorway  closed  inwardly  by  an  iron  door  coated 
with  lead  and  secured  without  by  bricks.  At  the  lower  part  of  the  chamber  there  is, 
in  an  iron  plate,  a  round  hole  which  can  be  opened  or  closed  by  the  rod,  H.  The 

Fig.  233. 


sulphur  flows  from  here  into  the  pan,  L,  near  which  is  a  rotating  vat,  M,  divided  into 
compartments,  into  which  the  sulphur  passes  in  the  form  of  rolls,  and  is  then  stored 
in^. 

If  roll  sulphur  is  to  be  produced,  each  cylinder  is  charged  with  raw  sulphur,  the 
covers  are  luted  and  one  cylinder  is  heated  ;  as  soon  as  the  distillation  is  half  effected 
the  second  cylinder  is  heated.  The  combustion  gases  from  both  hearths  raise  the 
temperature  of  the  pan,  Z>,  so  far  that  the  sulphur  melte  and  is  thus  purified,  by  the 
subsidence  of  the  heavy  impurities,  by  the  escape  of  the  moisture  present,  and  by  the 
separation  of  light  matters  on  the  top.  As  soon  as  the  distillation  of  the  first  cylinder 
is  at  an  end  it  is  charged  afresh  from  the  pan,  Z),  by  means  of  the  pipe,  F.  Each  dis- 
tillation lasts  four  hours,  and  1800  kilos,  of  sulphur  are  obtained  in  twenty-four  hours 
from  the  two  cylinders  in  six  operations.  As  the  temperature  in  the  chamber  is  always 


SECT.    III.] 


SULPHUR. 


above  112°,  the  sulphur  remains  liquid.     As  soon  as  the  stratum  of  melted  sulphur  is 
deep  enough  it  is  drawn  off  into  the  small  pan,  L,  and  ladled  into  wooden  moulds. 

If  flowers  of  sulphur  are  to  be  produced,  the  temperature  in  the  chamber  must  not 
exceed  110°,  as  the  sulphur  would  otherwise  melt ;  to  keep  down  the  heat,  only  two  dis- 
tillations of  150  kilos,  are  undertaken  in  twenty-four  hours.  As  soon  as  the  layer  of 
flowers  of  sulphur  at  the  bottom  of  the  chamber  has  reached  a  certain  height  the  door 
above  mentioned  is  opened  and  the  flowers  of  sulphur  are  shovelled  out. 

In  Dujardin's  refining  apparatus  the  distillation  is  effected  in  a  lenticular  retort,  a 
(Figs.  234,  235,  236),  with  an  annex,  b,  capable  of  being  closed  by  the  trap,  c,  in  order 
that  no  air  may  enter  while  the  retort  is  emptied.  On  the  hearth  is  an  oval  pan,  d,  heated  by 
the  escaping  fire  and  connected  with  the  retort  by  the  tube,  e,  which  can  be  closed  by  the 
plug,  f.  This  pan  holds  600  kilos,  of  sulphur,  which,  as  soon  as  melted,  is  let  run  with  all 
its  impurities  into  the  retort. 

When  it  is  volatilised  (in  about  Fi£-  234- 

four  hours)  the  trap  is  closed  and  [C 

the  residue  is  emptied  into  g. 
In  general,  six  distillations  are 
completediri  twenty-four  hours, 
using  500  kilos,  of  fuel.  In  about 
five  or  six  days  the  sulphur  is 
cast  into  rolls.  Only  400  kilos,  of 
raw  sulphur  are  daily  distilled 
i'or  the  production  of  flowers 
of  sulphur.  The  experience 
of  the  Wyndt-Aerts  works  at 
Merxem,  near  Antwerp,  where 
such  a  furnace  is  in  action, 
shows  that  the  total  loss  does 
not  exceed  2-23  per  cent,  and 
that  the  residues  are  quite  free 
from  sulphur.  This  is  effected 
with  crude  sulphur  which  con- 
tains on  the  average  1*5  per  cent,  of  impurities,  so  that  the  true  loss  is  reduced  to 
°'73  Per  cent.  In  the  works  in  which  this  apparatus  is  in  action  1500  tons  of  sulphur 
are  distilled  yearly. 

Still  simpler  than  the  above  Belgian  apparatus  is  one  used  in  German  refineries, 
consisting  of  two  cast-iron  pans  of  i  metre  diameter  and  height,  at  the  distance  of 
2  metres  from  each  other  and  connected  with  each  other  by  a  knee-piece.  The  one 
pan  is  fixed  over  a  grate  fire  and  is  charged  by  means  of  a  funnel  going  down  through 
the  knee-piece  and  descending  almost  into  the  melted  sulphur,  whilst  the  refuse  is 
removed  by  a  side-tube.  The  vapours  of  sulphur  as  they  are  driven  over  condense  in 
the  second  pan  which  is  bricked  round  so  that  the  melted  sulphur  may  remain  liquid 
and  may  be  let  off  by  a  cock. 

Commercial  flower  of  sulphur  always  contains  sulphurous  and  sulphuric  acids,  which 
may  be  chiefly  removed  by  washing  with  water. 

Sulphur  from  Iron  Pyrites  (Sulphur  Ores),  FeS2.— Iron  pyrites  may  give  off  26*65 
parts  of  sulphur  without  being  rendered  unfit  for  the  manufacture  of  copperas  (ferrous 
sulphate).  But  if  half  the  sulphur  present  in  the  pyrites  were  to  be  expelled  by  heat 
it  would  be  necessary  to  apply  a  temperature  at  which  the  residual  iron  monosulphide 
would  fuse,  and  would  be  absorbed  into  the  fire-clay  cylinders  and  destroy  them.  It  is 
therefore  thought  preferable  to  expel  only  13-14  per  cent,  sulphur  by  heat  when  the 
residue  remains  pulverulent  and  does  not  attack  the  distillatory  vessels.  Iron  pyrites 


248 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


always  contains  arsenic.     According  to  the  analyses  of  E.  Hjelt  (1877)  Spanish  pyrites 
contain  0-91  per  cent. ;  Westphalian  0-3  ;  Norwegian  only  traces. 

The  pyrites  are  heated  in  conical  tubes  of  fire-clay,  .1,  which,  as  shown  in  Fig.  237, 
are  laid  over  a  fire  in  an  inclined  position.  The  lower  opening  is  closed  with  a  sieve- 
plate  of  burnt  clay,  A,  which  prevents  the  pyrites  from  falling  out,  but  allows  the 
melted  sulphur  to  escape  either  as  a  liquid  or  as  a  vapour.  At  this  end  there  is  an 
earthen  tube,  b,  through  which  the  sulphur  arrives  in  receiver,  C,  containing  water. 
The  tubes  are  filled  with  coarsely  pulverised  pyrites,  closed  with  fire-clay  lids  luted  on  and 

then  heated.   The  raw  sulphur 

Fig.  235.  found  in  the  receiver  is  of  a 

greenish-grey   colour    and    is 
purified  by  re-melting.     Such 
sulphur  is  met  with  in  com- 
merce in  lumps  as  melted  sul- 
phur.    In  order  to  purify  it 
from  the  accompanying  arsenic 
sulphide  it  is  redistilled.     The 
residue  from  this  is   the  so- 
called    horse-sulphur   used  in 
veterinary  practice.  The  orange 
colour  of  the  sulphur  obtained 
from   pyrites    is  owing   more 
frequently   to   an    admixture 
of   thallium   than   to  arsenic. 
Crookes  found  in  Spanish  py- 
rites-sulphur as  much  as  0*29 
per  cent,  of  thallium. 
Sulphur  from  Roasting  Copper  Ores,  as 
a  bye-product  of  the  extraction  of  copper. — 
In  the  Lower  Harz  so-called  virgin  sulphur 
was  formerly  obtained  in  stalactitic  pieces 
from  copper  pyrites,  the  sulphur  being  let 
drop  out  at  an  opening  in  the  side  of  the 
roasting-heap. 

Gas-Sulphur,  as  a  bye-product  at  gas- 
works.— In  purifying  gas  withs  Landing's 
mass  the  sulphur  collects  in  quantities  up 
to  40  per  cent,  according  to  the  equation  : 
Fe203  +  H2S  =  2FeO  +  H20  +  S.  The  sul- 
phur is  extracted  with  carbon  disulphide, 
or  the  mass  is  roasted  in  kilns  for  the 
manufacture  of  sulphuric  acid. 

Sulphur  from  Vat  Waste. — See  Alkali 
Manufacture. 

Sulphur  from  Sulphurous  Acid  and  Sulphuretted  Hydrogen. — Dumas  in  1830 
observed  that  if  ^  sulphuretted  hydrogen  is  burnt  and  the  sulphur  dioxide  produced 
is  passed  into  a  moist  chamber  along  with  f  sulphuretted  hydrogen,  almost  all  the  sulphur 
might  be  recovered  :  S02+  2H,S  —  2H20  +  38.  This  reaction,  in  which  nearly  half  the 
sulphur  is  lost  by  the  formation  of  pentathionic  acid,  has  been  often  tried  in  order  to 
recover  the  sulphur  from  gypsum,  crelestiiie,  heavy  spar,  and  the  residues  of  the  Leblanc 
alkali  process  (according  to  the  method  of  Schaffner  and  Helbig).  The  process  is  essen- 
tially as  follows : — Heavy  spar,  e.g.,  is  reduced  by  ignition  with  carbon  to  barium  sulphide, 


Section  across  A  B. 


SULPHUR. 


249 


Fig.  237. 


SECT.   III.] 

which  is  then  heated  with  hydrochloric  acid  or  magnesium  chloride  in  order  to  obtain  on 
the  one  hand  barium  chloride  and  on  the  other  sulphuretted  hydrogen,  which  is  either 
partially  burnt  and  then  converted  into  sulphur  by  means  of  the  unburnt  sulphuretted 
hydrogen  according  to  the  above  reaction,  or  the  sulphuretted  hydrogen  gas  is  at  once 
passed  into  water  or  a  solution  of  magnesium  chloride  into  which  there  is  passed  at  the 
same  time  sulphur  dioxide  produced  by  roasting  pyrites.  By  a  similar  reaction  sulphur 
is  also  obtained  as  an  important  bye-product  in  the  extraction  of  potassium  salts  and 
iodine  from  kelp.  At  Paterson's  iodine-works  in  Glasgow  the  annual  yield  of  sulphur 
from  kelp  is  about  100  tons.  According  to  C.  Kopp  sulphur  may  be  also  obtained  by 
the  imperfect  combustion  of  sulphuretted  hydrogen  (H2S  +  O  =  H2O  +  S). 

Sulphur  from  Sulphurous  Acid  and  Carbon. — If  sulphurous  acid  is  passed  over  ignited 
coals  the  latter  burn  to  carbon  dioxide,  and  sulphur  is  eliminated.  In  this  manner 
sulphur  is  obtained  at  Borbeck  on  roasting  zinc  blende. 

Sulphur  from  Sulphuretted  Hydrogen. — Sulphuretted  hydrogen  if  passed  through 
tubes  at  a  red-heat  is  resolved  into  its  con- 
stituents. It  is  passed  through  ferric  hy- 
droxide suspended  in  water,  when  the  gas  is 
entirely  absorbed.  The  iron  sulphide  is  con- 
verted into  free  sulphur  and  ferric  hydroxide 
if  air  is  forced  in. 

Properties.  —  In  its  ordinary  condition 
sulphur  has  a  peculiar  yellowish  colour,  which 
becomes  darker  at  100°  and  almost  disappears 
at  50° ;  it  is  easy  to  pulverise ;  its  spec.  gr.  is 
1-98-2-06  ;  it  melts  at  i^-iiS'S"  to  a  thin 
yellow  liquid,  which  becomes  thicker  and  of 
an  orange-colour  at  160° ;  at  220°  it  becomes 
tough  and  reddish ;  between  240°  and  260°, 
very  tough  and  reddish-brown ;  at  340°  it 
grows  more  liquid  again ;  and  at  448-4°  (Reg- 
nault),  without  losing  its  dark  colour,  it  begins 
to  boil  and  is  converted  into  dark  reddish- 
brown  vapours.  If  sulphur  is  heated  to  230° 
and  is  suddenly  cooled  by  plunging  into  water, 
it  becomes  soft  and  plastic,  and  in  this  state 
it  can  be  used  for  taking  impressions  of 
medals  and  other  engraved  work.  After 

some  days  it  recovers  its  original  hardness,  so  that  the  impressions  can  be  used  as 
moulds  for  reproducing  very  sharp  copies.  If  sulphur  is  heated  in  contact  with  air 
it  burns  to  sulphurous  acid.  It  is  insoluble  in  water,  very  slightly  soluble  in  absolute 
alcohol  and  ether,  more  readily  in  carbon  disulphide,  100  parts  of  which  at  48-5°  dissolve 
146-21  parts  of  sulphur.  It  is  also  soluble  in  heated  oils,  fatty  and  volatile,  and  dissolves 
on  boiling  in  soda  and  potassa-lye.  It  is  used  in  the  manufactures  of  gunpowder  and 
matches,  for  sulphuring  hops  and  wines,  for  applying  to  trees  as  a  remedy  for  the  parasitic 
diseases,  for  the  preparation  of  sulphurous  acid,  sulphites  and  thiosulphites,  carbon  di- 
sulphide, vermilion,  mosaic  gold,  and  other  metallic  sulphides,  in  the  manufacture  of 
certain  cements,  and  for  vulcanising  caoutchouc  and  gutta-percha. 

Besides  Italy,  with  about  400,000  tons,  Spain  yields  yearly  6000  tons,  Austria  and 
Oermany  each  900  tons  (not  including  regenerated  sulphur),  and  the  rest  of  Europe 
900  tons  of  sulphur. 

Carbon  Disulphide,  CS2. — This  compound  (which  was  discovered  by  Lampadius  in 
1796)  is  obtained  by  bringing  sulphur  in  contact  with  ignited  carbon,  or  distilling 


250 


CHEMICAL   TECHNOLOGY. 


[SECT,  in 


metallic  sulphides  (pyrites,  blende,  &c.)  with  carbon.  The  yield,  according  to  W. 
Stein,  is  best  when  the  vapour  of  sulphur  is  allowed  to  act  upon  carbon  at  a  medium 
grade  of  redness. 

In  the  manufacture  of  carbon  disulphide  the  apparatus  of  Peroncell  is  often  used 
(Fig.  238).  A  clay  gas-retort,  A,  stands  on  a  stone  support,  fi,  and  is  built  into  a 
furnace.  On  the  cover  of  the  cylinder  there  are  two  necks,  E,  into  one  of  which  is 
cemented  a  porcelain  tube  which  extends  almost  to  the  bottom  of  the  cylinder  and  rests 
upon  a  layer  of  pieces  of  charcoal  with  which  the  bottom  is  covered  and  with  which 
it  is  otherwise  filled  up.  The  sulphur  is  added  through  this  opening,  U,  fitted  with 
the  porcelain  tube,  and  through  the  other  opening  charcoal  is  added  from  time  to  time. 
The  fumes  of  carbon  disulphide  formed  escape  through  the  lateral  tube,  H,  into  the 
stoneware  receiver,  «/,  in  which  a  part  of  the  carbon  disulphide  is  condensed  and  flows 
through  K  into  the  Florentine  flask,  L,  and  thence  through  the  bent  tube,  M,  into 
the  jar,  0,  from  which  it  can  be  let  off  by  means  of  the  cock,  N.  The  vapours  not 
liquefied  in  J  pass  through  the  pipe,  P,  into  the  cooling-apparatus,  T,  from  which  it 
escapes  at  R  into  the  receiver ,  S. 

Notwithstanding  the  most  careful  refrigeration,  the  quantity  of  disulphide  is  never 

obtained  which  the  weight  of 

Fig.  238.  sulphur  employed  should  theo- 

retically yield,  not  only  in  con- 
sequence of  the  unavoidable 
loss  of  a  part  of  the  carbon  di- 
sulphide, but  probably  from  the 
simultaneous  formation  of  car- 
bon monosulphide  (CS,  corre- 
sponding to  carbon  monoxide), 
which  is  formed  to  some  extent 
along  with  the  disulphide.  The 
product  obtained  contains  10  to 
12  per  cent,  sulphur  in  solu- 
tion, in  addition  to  sulphu- 
retted hydrogen  and,  doubt- 
less, some  other  compounds  of 
carbon,  sulphur,  and  oxygen, 

which  give  it  an  exceedingly  unpleasant  smell.  It  is  purified  by  rectification,  solution  of 
chloride  of  lime  being  introduced  into  the  apparatus,  which  destroys  the  sulphuretted 
hydrogen,  and  the  rectification  is  then  begun  by  passing  steam  at  one  atmosphere  under- 
neath the  still.  According  to  Braun,  pure  carbon  disulphide  may  be  obtained  by 
repeated  distillation  over  a  pure  fatty  oil.  In  order  to  protect  carbon  disulphide  in 
the  refrigerators,  &c.,  from  evaporation,  it  is  kept  covered  with  a  layer  of  water  of 
20  to  30  centimetres  in  depth. 

Properties. — When  pure,  carbon  disulphide  is  a  limpid,  colourless,  motile  liquid  which 
refracts  light  strongly  and  has  an  odour  somewhat  like  that  of  chloroform,  and  an 
aromatic  flavour.  Its  spec.  gr.  =  1-2684.  It  boils  at  46-5°  and  evaporates  quickly 
at  common  temperatures.  Its  ignition  point  is  170°.  It  does  not  combine  with  water, 
but  mixes  with  it  in  the  proportion  of  i  per  cent.  It  is  miscible  in  all  proportions  with 
alcohol,  ether,  and  similar  liquids.  It  dissolves  resin,  f  atty  and  ethereal  oils,  caoutchouc, 
gutta-percha,  wax,  camphor,  sulphur,  phosphorus,  and  iodine,  in  large  quantity.  It 
is  very  readily  inflammable,  and  burns  with  a  faint  blue  flame  to  form  sulphurous  and 
carbonic  acids  (whence  its  utility  in  extinguishing  burning  chimneys  and  fires  in 
close  spaces,  such  as  cellars  and  magazines).  A  mixture  of  its  vapour  with  oxygen  or 
atmospheric  air  gives  a  violently  explosive  gas.  A  mixture  of  nitric  oxide  and  vapours 


SECT,  in.]  SULPHUR.  251 

of  carbon  disulphide  give,  when  ignited,  a  very  intense  light,  which  has  been  used  in 
photography. 

Up  to  1850  the  only  use  of  carbon  disulphide  on  the  large  scale  was  in  vulcanising  and 
dissolving  caoutchouc.  Latterly  it  has  been  employed  for  extracting  fat  out  of  bones 
which  are  to  be  used  for  the  preparation  of  animal  charcoal ;  for  extracting  oils  from  oil- 
seeds (palm  kernels,  olives,  rape-seed,  linseed,  poppy-seed,  &c.),  for  extracting  sulphur 
out  of  minerals,  asphalt  from  bituminous  rock,  and  recovering  oil  and  fat  from  matter 
in  which  it  was  formerly  lost  (such  as  the  "  glycerine  tar,"  the  glycerine  goudroneuse  of 
the  French  stearine  works,  where  it  is  found  as  a  bye-product  of  the  saponification  with 
sulphuric  acid),  from  the  brown  residues  of  wheel-grease,  from  saw-dust  which  has 
served  for  filtering  oils  which  have  been  refined  with  sulphuric  acid ;  from  the  dregs 
of  tallow-melting,  the  so-called  greaves ;  for  extracting  fat  from  wool  and  waste  used 
in  cleansing  machinery — the  fat  thus  recovered  may  be  used  in  soap-boiling ;  in  the 
production  of  potassium  ferrocyanide  on  the  Tcherniak  and  Giintzburg  process  and 
of  ammonium  sulphocyanide ;  for  purifying  raw  paraffine  by  Alcan's  process ;  in 
electro-plating — a  small  quantity  of  carbon  disulphide  is  added  to  the  silver  bath  to 
give  at  once  a  brilliant  surface ;  for  killing  rats  and  other  vermin ;  a  solution  of  wax 
in  carbon  disulphide  is  used  in  preparing  wax  paper  and  in  coating  plaster  figures. 
Konig  burns  carbon  disulphide  in  an  especial  lamp  for  disinfecting,  and  Dahlen  uses 
it  for  sulphuring  casks.  Recently,  compounds  of  the  alkali-metals  with  sulphocarbonic 
acid,  CH2S3  =  CS(SH2)3,  have  been  successfully  used  in  a  watery  solution  as  a  remedy 
for  the  phylloxera.  The  salts  of  xanthogenic  acid  (ethyl  disulphocarbonic  acid),  a  deri- 
vative of  carbon  disulphide,  have  been  used  by  Zoller  for  preserving  articles  of  food,  and 
by  H.  Schwarz  for  producing  explosive  mixtures.  The  vapour  of  carbon  disulphide  is 
recommended  against  the  grape-disease. 

Sulphur  Chloride  (Cl2Sj)  is  a  compound  used  for  vulcanising  caoutchouc.  It  is  an 
oily  liquid  of  sp.  gr.  1*60 ;  is  of  a  brownish  colour  and  has  a  suffocating  smell ;  it  fumes 
in  the  air  and  boils  at  144°.  In  contact  with  water  it  is  quickly  decomposed  into 
sulphurous  and  hydrochloric  acids,  sulphuric  acid,  and  sulphur.  Sulphur  chloride  is  a 
good  solvent  for  sulphur ;  it  converts  rape  oil  into  a  mass  resembling  caoutchouc,  and 
linseed  oil  into  a  varnish.  It  is  obtained  by  passing  chlorine  gas,  washed  and  dried, 
through  melted  sulphur  heated  to  125°  to  130°.  Sulphur  chloride  is  at  once  formed, 
and  distills  over  into  a  cooled  receiver,  carrying  with  it  vapours  of  sulphur.  It  is 
redistilled  to  purify  it  from  free  sulphur. 

Sulphurous  and  Sulphuric  Acids. — Sulphurous  acid,  S02  (more  correctly  named 
sulphur  dioxide),  is  obtained  by  the  combustion  of  sulphur,  by  roasting  metallic  sul- 
phides, or  by  the  reduction  of  sulphuric  acid. 

The  furnaces,  kilns,  or  burners  are  built  of  bricks  (Fig.  239) ;  at  a  height  of  80  centi- 
metres above  the  floor  there  is  placed  a  stout  iron  plate,  sloping  slightly  forwards.  Upon 
this  plate  rest  the  side-walls,  whilst  the  back  and  the  top  of  the  furnace  are  also  formed  of 
iron  plates.  The  same  applies  to  the  front  side  of  the  furnace,  in  which  there  are  several 
(three  to  six)large  openings,/*,  which  are  closed  with  iron  plates  fitted  with  wooden  handles. 
Within,  upon  the  iron  plate  which  forms  the  sole  of  the  furnace,  there  are  three  iron 
rails,  placed  lengthwise,  each  10  centimetres  in  height,  which  divide  the  bottom  into  three 
or  six  compartments,  corresponding  to  the  number  of  the  doors.  At  H,  there  are  air- 
holes. From  the  iron  plate  which  forms  the  top  of  the  furnace  there  goes  off  a  wide 
pipe,  T,  which  carries  off  the  gases  and  vapours  formed  in  the  furnace.  In  starting 
this  furnace  the  workman  places  about  50  kilos,  of  lump  sulphur  in  each  compartment, 
and  kindles  the  surface;  the  draught  through  the  air-holes,  H,  is  regulated  so  that 
the  required  quantity  of  sulphur  burns  to  sulphuric  acid,  but  that  no  sulphur  sub- 
limes. If  the  furnace  is  at  the  same  time  to  furnish  the  nitrous  vapours  necessary 
for  the  formation  of  sulphuric  acid,  there  is  introduced  into  each  compartment  a 


252 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


Fig.  239. 


movable  furnace  on  feet,  in  which  is  a  mixture  of  soda-saltpetre  and  sulphuric  acid 
at  1 16°  Tw.  ( =  i  -56  spec.  gr.).     The  combustion  heat  of  the  sulphur  causes  hyponitrous 

acid  to  be  evolved  f  rom  this  mixture,  which  es- 
capes along  with  the  sulphurous  acid  through 
the  pipe,  T. 

However  much  these  furnaces  have  been 
improved,  they  labour  under  the  defect  that 
in  them  the  sulphurous  acid  is  not   evolved 
continuously,  but  in  fits,  by  which  the  regu- 
larity of  the  process  is  endangered.     It  is 
better  to  use  sulphur  furnaces  with  an  un- 
interrupted working,  in  which  an  equal  cur- 
rent of  melted  sulphur  flows  down  upon  the 
burner-plate,  and  forms  in  every  part  of  time 
the  same  quantity  of  sulphurous  acid. 
To  every  square  metre  of  the  floor  of  the  furnace  60  to  70  kilos,  of  sulphur  are  allowed 
in  twenty-four  hours,  and  to  every  too  cubic  metres  of  the  lead  chambers  46  to  50 
kilos,  of  sulphur  in  small  works,  in  larger  ones  66  to  100.     The  sulphur  ovens  are  being 
gradually  superseded  by  those  for  pyrites  or  blende. 

The  furnaces  for  roasting  pyrites  consisted  at  first  of  a  shaft  without  a  grate. 
In  the  vault  there  were  two  openings,  the  one  connected  with  the  chimney  and  the 
other  with  the  lead  chambers.  In  the  front  and  the  back  there  were  a  number  of 
holes  which  served  to  admit  air  and  to  watch  the  process.  The  upper  aperture  was 
for  the  introduction  of  pyrites,  broken  to  the  size  of  a  nut ;  the  lower  was  for  the 
removal  of  burnt  ore. 

In  the  Oker  works,  in  the  Harz,  similar  kilns  are  in  use,  according  to  W.  Knocke. 
For  every  four  kilns  there  are  two  nitre-channels,  which  lie  so  between  the  furnace- 
shafts  that  the  temperature  is  reached  which  is  needed  for  decomposition.     Figs.  240, 
Fig.  240.  Fig.  241. 


241,  242,  243,  give  a  front  and  side  elevation  and  the  corresponding  sections.  Two 
rows  of  two  or  four  kilns  each  are  in  contact  with  the  back  wall,  a  and  b  are  openings 
for  drawing  out  the  burnt  ore  ;  /,  openings  for  introducing  the  charge  (a  mixture  of  80 
per  cent,  iron  pyrites  and  20  per  cent,  copper  pyrites)  'containing  about  50  per  cent, 
sulphur ;  c,  d,  e,  i,  are  openings  for  stirring  up  the  ore  and  keeping  up  the  current  of 
air ;  g,  are  the  nitre-channels.  In  the  space,  h,  cast-iron  nitre  boxes  are  kept  ready 
filled.  In  twenty-four  hours  2700  kilos,  of  ore  are  roasted,  and  50  kilos,  nitre  are 
consumed. 

When  the  kilns  are  new  they  are  heated  for  some  days  by  a  wood  fire  placed  on 


SECT.    III.] 


SULPHUK. 


the  sole  of  the  furnace  and  gradually  strengthened ;  roasted  ore  is  then  introduced  up 
to  10  centimetres  below  the  door,  and  upon  this  ore  there  is  kept  up  a  strong  flame  fire 
until  the  sides  of  the  kiln,  and  especially  the  vault,  are  red  hot.  Raw  ore,  in  pieces 
from  the  size  of  a  walnut  to  that  of  a  fist,  is  placed  upon  the  roasted  ore  to  the  depth 
of  9  to  12  centimetres.  The  raw  ore  is  ignited  by  the  heat  of  the  kiln  and  the  wood 
fire,  and  is  roasted.  The  vapours  are  passed  into  the  open  air  as  long  as  the  wood  fire 
is  in  existence.  When  it  is  consumed  and  the  ore  is  in  full  glow,  the  vapours  are 
conveyed  into  the  chambers.  The  workmen  continue  in  this  manner  drawing  out  as 
much  burnt  ore  below  as  they  put  in  raw  ore  above.  The  kilns  are  worked  so  that  each  is 
emptied  and  refilled  three  times  in  twenty-four  hours,  and  attended  to  three  times.  Every 
two  hours  two  kilns  are  charged  afresh  and  two  others  are  attended  to.  The  attention 


Fig.  242. 


takes  place  four  hours  after  charging,  and  consists  in  breaking  up  the  ore  with  iron  bars, 
that  the  air  may  have  proper  access.  The  air  required  for  the  oxidation  of  the  sulphur 
enters  chiefly  from  below,  through  the  roasted  ore.  If  there  is  any  deficiency  it  is 
made  up  by  admitting  air  at  the  slides  in  the  side  doors.  The  soda-saltpetre  is  placed 
in  cast-iron  boxes,  with  sulphuric  acid,  at  30°  Tw.,  and  placed  in  the  channels.  In 
the  course  of  four  hours  they  are  replaced  by  fresh  nitre  boxes,  so  that  each  channel  is 
freshly  supplied  six  times  in  twenty-four  hours.  In  roasting,  care  must  be  taken  that  the 
fire  does  not  work  downwards  and  so  smelt  the  mass  together.  The  ore  must  not  be 
placed  too  closely  together,  or  be  broken  up  too  finely. 

Fig.  244.  Fig.  245. 


In  the  sulphuric  acid  works  at  Marseilles  pyrite  kilns  with  grates  are  used,  arranged 
as  shown  in  Figs.  244  and  245.  They  consist  of  two  hearths,  A,  with  grates.  Between 
them  is  a  pan  of  sandstone  or  cast-iron  for  the  mixture  of  nitre  and  sulphuric  acid. 
The  gas  of  the  one  hearth,  separated  by  a  tongue  from  the  other,  that  the  nitre  pan 
may  not  be  over-heated,  meets  with  the  other  gases  shortly  before  the  exit  from  the 
kiln.  Slits  in  the  doors  admit  the  air.  Each  hearth  is  charged  with  150  kilos,  of 
pyrites  broken  so  as  to  pass  a  2 -inch  sieve.  A  furnace  with  two  hearths  roasts  2000 
kilos,  pyrites  in  twenty-four  hours. 


^54 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


in  the  Gerstenhb'fer  roasting  kilns  (terrace  kilns)  the  comminuted  ore  falls  through 
hoppers  fitted  with  grooved  rollers  xipon  earthen  bearers,  and  slips  down  from  one  stage 
to  another,  being  kindled  by  the  ignited  sides  of  the  furnace  which  have  been  previously 
heated  by  fire  upon  a  removable  grate,  and  roasted  by  the  action  of  the  air  admitted 
at  the  sides.  The  burnt  ore  which  falls  upon  the  sole  of  the  furnace  (which  narrows 
below)  is  drawn  out  at  a  side  door.  In  the  roasting  space,  A  (Figs.  246  and  247),  there 
are,  besides  the  three  upper  distributors  of  the  ore,  m,  fifteen  rows  of  ore-bearers,  n,  each 
alternately  of  six  and  seven  pieces  of  Meissen  clay  (together  looin  number)  ;  the  bearers 
with  corresponding  sections  come  in  contact  with  projections  of  the  stones  in  the 
front  and  back  walls.  The  roasting-gases  from  A  arrive  through  the  space,  e  (Fig. 
248),  into  the  flue-dust  chambers,  C  and  E,  and  thence  into  the  lead-chambers.  In 

a  vaulted  passage,  Z>,  through 

Fig-  246-  FiS-  247.  the  flue-dust  chambers,  E,  are 

the  valves  in  the  air-chest,  by 
means  of  which  is  regulated 
the  access  of  air  into  the  fur- 
nace through  the  channel,  I, 
and  the  opening,  a  (Figs.  246 
and  247).  The  flue-dust 
settling  in  B  can  be  removed 
through  openings,  g,  in  the 
vault.  For  introducing  the 
ores  through  the  slits,  d,  the 
three  distributors  there  serve 
the  shoot-arrangement  above. 
On  the  platform  of  the  furnace 
stands  a  cast-iron  chest  on  feet, 
9  centimetres  broad;  its  right 
and  left  sides  are  straight,  but 
its  front  and  back  are  beut  in. 
After  it  has  been  set  in  its 
place,  the  masonry  of  fire-bricks 
is  carried  up  within  the  sides 
as  far  as  9  centimetres  belou- 
its  upper  angle,  keeping  the 
space  for  the  slits  open,  and 
the  angle  formed  on  the  right 
of  each  slit  is  kept  so  broken  off  that  a  curved  cast-iron  plate,  which  conveys  the  ore  to 
the  rollers,  is  supported  both  by  the  wall  and  on  the  projections  of  the  chest.  To  pro- 
tect the  roller-bed  from  direct  contact  with  the  fine  mass  of  the  charge,  two  cast-iron 
plates  are  laid  over  each,  resting  partly  in  a  niche  left  in  the  masonry  and  partly  upon 
A  three-sided  prism-shaped  piece  laid  upon  the  plate.  The  covers  of  the  slits  have  two 
handles  ;  they  prevent  the  direct  fall  of  the  charge  into  the  slits,  and  cause  it  to  enter 
the  roasting  shaft  only  between  the  rollers  and  the  guiding  plate,  thus  rendering  it 
possible  for  it  to  be  introduced  always  in  equal  quantity  and  not  beyond  a  certain 
limit.  The  two  pieces  screwed  to  the  front  wall  of  the  chest  support  bearings  for  a 
shaft  on  which  are  fixed  three  endless  screws  which  fit  into  the  teeth  of  the  wheels. 

For  starting  the  furnace,  fifteen  or  sixteen  grate-bars,  r,  are  inserted  through  the 
middle  opening,  »",  which  is  then  filled  up  with  bricks  and  clay ;  the  intervals  between 
the  grate-bars  are  filled  up  outwardly ;  coals  are  placed  upon  the  grate  through  h,  and 
kindled  by  a  wood  fire  from  below ;  the  upper  openings,  h,  are  closed  tightly  with  iron 
plates,  but  the  exit  hole,  k,  is  left  open.  To  prevent  the  ore-bearers  from  cracking,  the 
furnace  is  heated  to  whiteness  very  gradually,  the  gaseous  products,  after  the  channel, 


SECT.    III. 


SULPHUK. 


255 


Fig.  248. 


g,  is  closed,  being  passed,  not  into  the  lead-chambers,  but  through  a  side-flue  into  a 
chimney.  The  bearers  are  kept  for  two  days  at  a  white  heat,  and  the  rollers  are  then 
started,  one  turn  in  five  minutes.  The  hoppers  have  been  filled  at  the  beginning  of 
the  heating,  to  prevent  the  combustion  gases  from  escaping  through  the  slits,  d.  By 
the  movement  of  the  rollers,  the  ore-bearers  are  gradually  filled  with  the  charge  up  to 
their  natural  slope,  and  the  firing  is  continued,  until  it  is  observed  through  c,  6,  that 
about  the  fourth  row  of  bearers  from  below  is  beginning  to  fill.  One  grate-bar  after 
another  is  then  drawn  out,  and  the  space  is  closed  with  bricks  and  mortar  until  the 
opening,  it  is  entirely  blocked.  The  ash-pit  is  cleared  out,  and  the  valve,  m,  is  opened 
to  admit  air  through  a.  The  filling  with  the  charge  at  the  above  speed  of  the  rollers 
takes  about  6|  hours.  After  the  admission  of  air,  the  volatile  products  of  roasting  are 
still  allowed  for  a  while  to  escape  by  the  chimney ;  afterwards  the  flue,  g,  is  opened, 
and  the  one  leading  to  the  chimney  is  closed.  As  will  be  seen  from  the  above  description, 
the  ore  falls  through  the  slits,  d,  at  first  upon  the  upper  bearers,  collects  there  as  long 
as  the  slope  allows,  and  then  all  further  supplies  of  material  slide  down  upon  the  next 
row  of  bearers.  As  to  the  uniformity  of  roasting,  the  Gerstenhofer  furnace  is 
much  superior  to  other  shaft-fur- 
naces, and  especially  to  muffle-fur- 
naces, as  it  contains  an  equal 
amount  of  the  charge  in  all  the 
horizontal  sections  at  the  same  time. 
The  ore  must  be  supplied  in  a  suffi- 
ciently fine  form,  that  the  roasting 
may  be  expeditious,  and  that  the 
heat  needed  for  keeping  up  the  pro- 
cess may  be  supplied  by  the  oxida- 
tion of  the  sulphur.  If  too  much 
cold  air  is  admitted,  the  heat  moves 
upwards ;  if  too  little,  it  goes  down- 
wards. In  the  former  case  the  fur- 
nace is  too  cold,  and  in  the  latter 
too  hot.  With  normal  working, 
almost  a  white  heat  is  reached  in 
the  hottest  part ;  if  any  irregularity 
appears,  the  air  must  be  partly  cut 
off  or  the  rollers  turned  more  quickly. 
The  Gerstenhofer  kiln  allows  poor 
ores  to  be  burnt  without  fuel,  at 
the  same  time  producing  rich  gas  of 
uniform  composition. 

The  Hasenclever  and  Helbig  kiln 
renders  it  possible  to  burn   smalls 

without  an  admixture  of  lump-ore.  The  ore  is  introduced  through  the  hopper  a 
(Fig.  249),  and  when  roasted  it  is  removed  in  proportion  as  fresh  smalls  slide  down 
from  the  hoppers.  The  air  entering  the  furnace  passes  upwards  over  the  layers  of  ore 
on  the  lowest  four  or  five  plates,  becomes  heated  and  mixed  with  a  little  sulphurous 
acid,  and  leaves  the  furnace,  rising  upwards  in  a  flue,  becoming  heated  in  contact  with 
the  gas-channels,  enters  the  furnace  above,  and  draws  downwards  when  the  hot  gases 
leave  the  furnace  in  two  shafts  and  enter  the  lead-chambers. 

The  plate-furnace  of  Maletra  has  come  into  extensive  use  on  account  of  the  simpli- 
city of  its  construction,  joined  to  the  circumstance  that  it  requires  no  fuel,  and  burns 
the  ore  very  completely.  This  furnace  is  shown  in  longitudinal  section  in  Fig.  250. 
Smalls  are  made  to  work  down  from  plate  to  plate  to  meet  the  ascending  current  of 


256 


CHEMICAL   TECHNOLOGY. 


[SECT.  in. 


gases,  and  do  not  slide  down  spontaneously  as  in  the  kilns  of  Gerstenhofer  and 
Hasencle  ver-  Helbig. 

It  is  set  in  action  by  the  grate,  a,  and  the  kiln-door,  b,  which  are  bricked  up  as  soon 
as  the  furnace  is  in  full  heat.  The  plates,  a,  b,  c,  d,  e,  aiiciy,  are  charged  with  smalls 
through  the  working  doors,  h,  i,  and  k,  when  the  ore  at  once  takes  fire.  The  furnace 
gases  sweep,  as  the  figure  shows,  over  all  the  plates,  pass  through  m  into  the  flue-dust 
chamber,  and  through  o  to  the  lead-chambers.  The  ore  is  removed  every  two  hours 
from  one  plate  to  the  next.  This  furnace  is  especially  adapted  for  smalls. 

For  roasting  blende  the  furnace  of  Eichhorn  and  Liebig  is  suitable.  It  con- 
sists of  a  number  of  roasting  chambers,  r  (Figs.  251  and  252),  with  six  or  more  soles, 
perfectly  separate  from  each  other.  They  are  heated  from  without  by  fire-gases 
drawn  from  a  generator,  G,  and  passing  through  the  flues  n.  For  the  due  distribution 
of  the  heat  in  the  long  flues  the  air  of  combustion,  heated  in  the  flues  I,  is  conveyed  to 
the  generator-gases  at  three  different  places. 

The  blende  has  been  previously  heated  on  the  top  of  the  furnace  by  the  radiant  heat 
from  the  masonry,  and  arrives  through  the  hopper  t,  on  the  highest  sole  of  each  separate 
roasting  furnace,  where  it  is  uniformly  spread  out.  After  about  six  to  eight  hours 
it  is  brought  down  to  the  second  sole,  and  after  the  same  length  of  time  to  the  third.  This 


is  effected  through  the  breaks,  a,  in  the  bottom,  which  are  alternately  at  the  front  and 
the  back.  Meantime,  the  upper  sole  is  constantly  charged  with  fresh  ore  through  the 
hopper.  The  ore,  according  to  its  nature,  remains  from  thirty-six  to  forty-eight  hours 
in  the  furnace  before  it  is  completely  roasted,  and  leaves  the  furnace  through  the  vent, 
k,  falling  into  the  cooling  space,  o. 

In  order  to  obtain  complete  roasting  on  the  sixth  sole,  the  air  which  is  admitted 
must  be  previously  well  warmed.  For  this  purpose  the  openings  into  the  furnace  are 
closed  as  nearly  air-tight  as  possible,  so  that  the  roasting  air  is  compelled  to  take  its 
way  through  a  tube,  e,  placed  under  every  roasting  ohamber ;  pas'sing  through  small 
ducts  left  in  the  sole  of  the  lowest  flue  (7),  it  is  strongly  heated.  The  access  of  the  air 
for  each  chamber  can  be  accurately  regulated  by  a  slide  at  the  mouth  of  the  tube,  e.  The 
heated  air  takes  its  way  through  the  outfall  channel,  k,  over  the  layers  of  ore — moving 
in  the  opposite  direction — continually  meeting  charges  richer  and  richer  in  sulphur, 
by  the  oxidation  of  which  it  becomes  saturated  with  sulphurous  acid,  and  finally  arrives 


SECT,  in.] 


SULPHUR. 


257 


through  the  channel,  s,  at  the  flue-dust  chamber,  F,  which  is  common  to  all  the  roasting  - 
chambers,  from  which  the  roasting  gases  pass  to  their  destination. 

In  such  a  furnace  about  3  tons  of  blende  are  roasted  in  twenty-four  hours  ;  or  about 
333  kilos,  per  compartment.  A  charge  is  drawn  every  six  hours  from  each  com- 
partment, and  the  blende  remains  thirty-six  hours  in  the  furnace.  In  the  successive 
compartments  the  blende  contains  the  following  proportions  of  sulphur  : — 


Haw  ore 
Upper  sole  . 
Second  sole 
Third  sole  . 
Fourth  sole 
Fifth  sole  . 
Bottom  sole 


31-2 

28-0 

24-3 

16-1 

8-8 

7-8 

0-96 


31-2 

23-8 

227 

16-5 

12-5 

7-8 

0-9 


31-2 

24-3 

197 

12-3 

9'9 

5'4 

1*29 


31-2 
24-2 
21-5 

I7-3 

? 

5-6 


At  the  Rhenania,  near  Aachen,  the  difficulty  has  been  observed,  according  to  Hasen- 
clever,  that  the  plates  of  these  furnaces  have  to  be  often  renewed.     The  mechanical 


Fig,  251. 


Explanation  of  Terms. 
Schnitt  1II-IV—  Section  III-IV. 


Fig.  252. 


roasting-furnace  of  the  Vieille  Mon- 
tagne  Company  is  in  action  at  the 
Rhenania  and  at  Oberhausen. 

This  blende-furnace  (Figs.  253  and 
254)  consists  of  several  roasting-soles, 

A,  one  above  another,  to  which  there 
joins  up  a  four-sided  roasting-hearth, 

B.  The   broken   ore   shot    into    the 
hopper,  a,  is  gradually  moved  down- 
wards by   means  of  two  rollers,   and 
the  channels,  K,  to  the  upper  roasting- 
sole,  in  order  to  be  despatched  to  the 
lower  roasting-plates  by  the  revolving 
stirring-hooks.     The  fire-gases  from  F 
pass  over  the  hearth,  £,  then  through 
the     roasting    sides,    A,    and    escape 
through  the  dust-chamber,  (7,  into  the 

exit  channel  S.  The  arrangement  for  stirring  consists  of  an  axle,  b,  passing  ver- 
tically through  the  furnace  with  cross-rods,  e,  which  carry  the  stirring-irons,  The 
joint  where  this  axle  enters  the  furnace  is  packed  with  asbestos.  The  axle,  b,  is 
in  an  iron  casing,  g,  to  which  it  is  secured  in  several  places.  In  the  interval  between 


Explanation  of  Terms. 
Schnitt  /-//—Section  I-II. 


258 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


g  and  b  cold  air  ascends  from  below,  thus  preventing  the  too  rapid  destruction  of  the 
casing,  g.  The  toothed  stirring-irons,  m,  are  fixed  radially  to  the  arms,  e,  and  serve 
merely  to  stir  up  the  ore.  The  smooth  stirrers,  /,  on  the  other  hand,  are  fixed  obliquely 
to  the  radial  direction  of  the  arm,  e,  and  according  to  the  angle  at  which  they  are  set, 
they  move  the  ore  either  from  the  middle  to  the  outside,  or  in  the  opposite  direction. 
By  means  of  an  opening  in  the  roasting-sole,  which  is  introduced  either  in  the  middle 
or  at  the  circumference,  according  to  the  position  of  the  hooks,  f,  the  ore,  after  being 
thus  stirred  up,  passes  down  to  the  next  lower  floor,  where  it  is  again  stirred  up  by  the 
toothed  irons,  m,  and  removed  by  the  smooth  hooks,  f,  to  the  opening  for  the  next  lower 
sole.  Lastly,  the  roasting  is  completed  on  the  hearth,  B. 

The  furnaces  which  have  been  recently  introduced  by  the  Khenania  at  Stolberg 
consist  of  a  series  of  muffles  placed  above  each  other  and  traversed  by  the  fire-gases. 
The  indirect  heat  suffices  for  the  complete  roasting  of  zinc  blende.  The  ores  are 
finely  ground,  placed  upon  the  top  of  the  furnace,  filled  upon  the  high  sole  by  means 
of  hoppers,  and  are  thence  removed  by  the  workmen  from  muffle  to  muffle,  and  at  the 
end  of  the  lowest  sole  they  are  completely  desulphurised.  It  requires  frequent 
stirring.  The  air  enters  at  the  working- doors,  and  is  converted  into  sulphurous  acid 


Fig-  253. 


Fig.  254. 
Schnitt.  l-il. 


Explanation  of  Terms. 
Schnitt  /-//—Section  I-II. 

in  contact  with  the  ig- 
nited ore.     It  is  carried 
up  in  flues  opposite  to 
the   working-doors  and 
arrives  in  the  lead-cham- 
bers.    By  means  of  these  channels  the  escape  of  gas  is  not  hindered,  and  it  is  possible 
to  convey  the  products  of  a  number  of  burners  into  the  same  lead-chamber,  which  is 
more  difficult  to  effect  when  hot  gases  have  to  be  conveyed  horizontally. 

In  twenty-four  hours  the  furnace,  at  which  two  men  work  in  each  twelve  hours'  shift, 
yields  3000  to  5000  kilos,  of  roasted  blende.  The  consumption  of  fuel  is  at  present  980 
kilos,  of  Ford  coals.  The  furnaces  are  worked  partly  with  gas  fires  and  partly  with 
grates.  The  sulphur  in  the  raw  ore  was : — 


After  ist  muffle 
„     2nd     „ 
.»     3rd     „ 

Finished 


19*2  per  cent. 
.     17-6 

.       I2"O 

•         3'4 

0-6 


26'8  per  cent. 

19-1 

II'2 
I'O2 
0'35 


26's  per  cent. 

I5-4 
9-9 

075 
075 


The  temperature  varies  according  to  the  proportion  of  sulphur  in  the  ores,  and  was 
in  the  first  muffle  580°  to  690°  ;  in  the  second  and  third  750°  to  900°.  In  rich  ores  the 
middle  muffle  is  hottest ;  in  poor  ores  the  highest  temperature  prevails  below. 

Pyrites  contain  almost  universally  small  quantities  of  foreign  matter,  which  interferes 


SECT.    III.] 


SULPHUR. 


259 


with  the  purity  of  the  acid  produced.  Hence,  in  commerce,  especially  in  England,  a 
distinction  is  made  between  pyrites  acid  and  brimstone  acid,  the  latter  being  the  dearer. 
It  is  known  that  the  discovery  of  selenium  is  closely  connected  with  the  use  of  pyrites 
in  sulphuric  acid  works  ;  it  was  discovered  by  Berzelius  in  1817  in  the  mud  of  the 
chambers  of  the  works  at  Gripsholm,  in  Sweden,  where  pyrites  from  Fahlun  were  burnt 
for  the  production  of  sulphurous  acid.  In  1862  thallium  was  discovered  by  Crookes  as 
accompanying  selenium  in  the  flue-dust  of  pyrites.  When  blende  is  burnt,  the  flue-dust 
may  contain  gallium.  Tellurium  is  also  found  mingled  with  the  roasted  gases  of  certain 
pyrites.  The  arsenic  of  pyrites  escapes  on  roasting  as  arsenious  acid,  which  accompanies 
the  sulphurous  acid  into  the  lead-chambers,  and  there  contaminates  the  sulphuric  acid. 
If  such  acid  is  used  in  the  production  of  soda,  the  arsenic  passes  partly  into  the  hydro- 
chloric acid  and  the  soda. 

Composition  of  the  Roasting  Gases. — 480  kilos,  of  iron  sulphide  require  (n  x  32)  = 
352  kilos,  or  (n  x  22-3)-  245*3  cubic  metres  oxygen,  and  give  (8  x  64)  =  512  kilos,  or 
(8  x  22-3)  =  178-4  cubic  metres  of  sulphurous  acid.  We,  therefore,  do  not  obtain — as 
on  burning  sulphur — the  same  volume  of  sulphurous  acid,  but  from  100  litres  oxygen 
only  72'7  litres  sulphurous  acid.  With  blende  : 

2ZnS  +  302  -  2ZnO  +   2 SO,, 
100  litres  oxygen  yield  only  667  litres  of  sulphurous  acid. 


Fig.  255. 


On  burning  sulphur  in  atmospheric  air,  the  mixture  of  gas  obtained  may  theoreti- 
cally contain  21  volumes  per  cent,  of  sulphurous  acid,  whilst  the  roasting  gases  from 
pyrites  can  contain  at  most  15-2  and  from  blende  14  per  cent,  sulphurous  acid. 

In  point  of  fact,  this  percentage  is  not  reached,  since  a  part  of  the  sulphurous  acid 
forms  always  S03  (or,  owing  to  atmospheric  moisture,  H2S04).  In  burning  sulphur  this 
production  of  sulphuric  acid  is  generally  trifling,  bxit  with  pyrites  it  may  amount  to 
20  per  cent,  of  the  existing  sulphurous  acid.  If  the  sulphurous  acid  is  to  be  used  as 
such,  this  circumstance  involves  a  considerable  loss. 

Liquid  Sulphurous  Acid. — For  the  production  of  liquid  sulphurous  acid  the  process 
of  Hanisch  and  Schroder  holds  good.  The  roasting  gases,  &c.,  pass  through  the  pipe  a. 
(Fig.  255),  into  the  scrubber,  b,  charged  with  pieces  of  coke,  over  which  a  rain  of  cold 
water  trickles  down  and  dissolves  the  sulphurous  acid.  The  non-dissolved  gases,  N  and 
O,  escape  at  c.  The  watery  solution  of  sulphurous  acid  flows  continuously  through  the 
pipe  d  into  a  series  of  closed  lead  pans,  e,  in  which  it  is  heated  to  a  boil.  The  escaping 
vapours  of  sulphurous  acid  arise  through  the  tube  /,  at  the  cooling  worm,  g,  which  is 
surrounded  by  cold  water,  and  from  here  through  the  pipe  h  into  the  pan  i,  into  which 
sulphuric  acid  is  injected  to  free  the  sulphurous  acid  perfectly  from  moisture.  From 
the  pan  i,  the  gases  pass  through  the  tube  k  to  the  pump,  I.  The  liquid  in  the  lead 


26o  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

pans,  e,  which  still  holds  small  quantities  of  sulphurous  acid  in  solution,  passes  for  further 
treatment,  through  the  pipe  m,  into  the  recipient,  n,  in  which  are  placed  nets  of  lead  wire, 
and  flows  in  the  form  of  rain  to  meet  a  current  of  steam,  which  is  introduced  by  the 
tube  o.  The  fumes  of  sulphurous  acid  thus  set  free  are  carried  off  by  the  pipe  p,  opening 
into  /,  traverse  the  refrigerating  worm  g  and  the  pan  *,  and  unite  with  the  remaining 
vapours  of  sulphurous  acid  in  the  pump,  I.  The  water  liquefied  in  the  worm,  g,  flows  back 
through  p  into  the  recipient,  n,  and  is  let  off  as  required  through  the  pipe  q.  In  order 
to  regulate  the  pressure  in  the  installation,  the  taffeta  bag,  r,  is  introduced  into  the  pipe 
k,  the  movement  of  the  pump  being  regulated  by  the  size  of  the  bag.  The  gases  com- 
pressed in  the  pump,  I,  pass  through  the  pipe  s  into  the  refrigerating  worm  t,  and  are 
there  liquefied.  From  the  worm  t  the  acid  flows  into  the  pan  u,  from  which  it  is  run 
off  into  strong  bottles,  v,  fit  for  transport.  In  order  to  carry  off  the  accompanying  gases 
(0  and  N),  there  is  connected  with  the  pan  u  a  pipe,  w,  provided  with  a  valve,  by  which 
these  gases  are  let  into  the  scrubber,  b. 

This  process  is  in  operation,  e.g.,  at  the  zinc-works  of  Hamborn  near  Oberhausen. 
The  sulphurous  acid  is  despatched  hence  in  pan-cans  holding  100  hectokilos.,  or  in  so- 
called  bombs,  containing  5  hectokilos.,  and  is  used  in  manufactories  of  ice,  in  sugar- 
works,  and  in  paper-mills  for  the  production  of  so-called  sulphite  stuff. 

The  process  is  worthy  of  notice,  with  reference  to  the  utilisation  of  the  sulphurous 
acid  which  escapes  in  melting  glass  from  sulphate  : 

Na2S04  +  0  +  Si02  =  JSa2Si03  +  CO  +  S02; 
in  the  manufacture  of  ultramarine,  &c. 

Much  inferior  are  the  processes  of  Pictet,  who  boils  sulphur  with  sulphuric  acid, 
and  of  Hart,  who  boils  iron  pyrites  with  sulphuric  acid. 

Properties. — Sulphurous  acid  is  a  colourless  gas  of  a  pungent  odour  which  can  be 
liquefied  by  pressure  or  by  strong  refrigeration.  One  litre  water  at  o°  dissolves  79-8  litres 
(=229  grammes),  at  +  10°  56*6,  and  at  20°  39'4  litres  sulphurous  acid.  One  cubic  metre 
of  sulphurous  acid  at  o°  and  760  millimetres  pressure  weighs  2 '86  kilos. 

Sulphurous  acid  is  a  powerful  blood  poison.  Air  containing  0*04  per  cent,  by 
volume  of  S02  occasions  difficulty  of  breathing. 

In  the  presence  of  water  all  the  higher  oxides  of  nitrogen  give  off  oxygen  to 
sulphurous  acid  and  convert  it  into  sulphuric  acid,  being  at  the  same  time  reduced  to 
nitric  oxide.  Chlorine  converts  moist  sulphurous  acid  into  sulphuric  acid.  If  mixed 
with  sulphuretted  hydrogen  in  presence  of  water,  sulphurous  acid  deposits  sulphur.  In 
contact  with  zinc  there  is  no  escape  of  hydrogen,  but  sulphurous  acid  is  converted  to 
hydrosulphurous  acid  or  hyposulphurous  acid  (H2S02) — not  to  be  confounded  with  the 
acid  formerly  called  hyposulphurous  acid,  but  now  known  as  the  thiosulphuric. 

Applications. — Sulphurous  acid  is  used  in  the  production  of  sulphuric  acid,  of 
paper,  of  the  madder  preparations  of  E.  Kopp  (now  almost  obsolete) ;  for  preparing 
sodium  thiosulphate,  and  for  obtaining  sulphate  from  sodium  chloride ;  for  opening  up 
alum  shales  in  the  manufacture  of  alum  ;  for  extracting  copper  from  certain  ores  ;  for 
dissolving  auriferous  and  argentiferous  iron  ores;  for  extracting  calcium  phosphate 
from  bones  'and  minerals  ;  for  preserving  fruits,  beer,  wines,  hops,  meat,  syrups  of 
dextrine,  saccharine  juices,  &c. ;  as  a  disinfectant ;  for  preparing  ice ;  for  bleaching  silk, 
wool,  sponge,  feathers,  glue,  gut  strings,  isinglass  (which  are  turned  yellow  by  chlorine), 
baskets,  straw-tissues,  gum  arabic,  &c.  The  bleaching  action  of  sulphurous  acid  may 
be  reduced  to  two  different  causes  ;  in  most  cases  the  colour  is  merely  masked,  but  in 
others  it  is  destroyed.  The  colouring-matters  of  most  red  and  blue  flowers,  fruits,  &c., 
form  with  sulphurous  acid  colourless  combinations,  but  the  colour  still  exists.  A  rose 
bleached  by  sulphurous  acid  recovers  its  original  red  tone  if  moistened  with  dilute 
sulphuric  acid.  The  colouring  matters  of  yellow  flowers  are  indifferent  to  sulphurous 
acid,  and  are  not  bleached.  Many  colours,  such  as  indigo  blue,  carmine,  and  the 


SECT.  HI.]  SULPHUB.  261 

natural  yellow  of  silk,  are  not  at  first  bleached  by  sulphurous  acid,  but  a  subsequent 
bleaching  is  effected  when  the  oxygen  present  is  ozonised  under  the  influence  of  Light, 
and  effects  a  destruction  of  the  colours.  The  deoxidising  power  of  sulphurous  acid  has 
been  used  of  late  for  extinguishing  fires. 

Sulphurous  acid,  as  furnace  smoke — and  indeed  coal-smoke — has  a  destructive  action 
on  vegetation.  Its  continuous  escape  blights  the  fields  and  destroys  entire  forests ;  coni- 
ferous trees  are  especially  sensitive  to  sulphurous  acid.* 

Calcium  Sulphite,  CaS03,  and  calcium  bisulphite  are  obtained  by  passing  the 
sulphurous  acid  obtained  by  burning  sulphur  or  roasting  pyrites  into  towers  filled 
with  limestone  whilst  water  trickles  down  from  above,  or,  better  still,  by  passing 
sulphurous  acid  into  milk  of  lime.  The  acid  solution  is  extensively  used  for  the  pro- 
duction of  "  sulphite  stuff,"  i.e.,  vegetable  fibre  treated  with  a  bisulphite,  for  the  paper 
manufacturer. 

The  uses  of  sodium  bisulphite  (leukogene)  are  much  the  same  as  those  of  the  free 
gaseous  sulphurous  acid.  It  bleaches  fine  woollen  and  worsted  goods  in  a  better  manner. 

Sodium  Thiosulphate. — This  compound,  Na2S203,5~E20  (formerly  known  as  sodium 
hyposulphite),  may  be  prepared  in  several  ways.  Kopp  first  produced  calcium  thio- 
sulphate  by  passing  sulphurous  acid  over  the  vat-waste  of  alkali  works,  and  decomposed 
the  lime  salt  thus  obtained  by  a  solution  of  sodium  sulphate,  when  gypsum  is  precipi- 
tated and  sodium  thiosulphate  remains  in  solution. 

It  has  the  important  property  of  forming,  with  silver  oxide,  a  readily  soluble  double 
salt  (silver  sodium  thiosulphate,  NaAgS203),  thus  readily  dissolving  insoluble  silver  com- 
pounds, such  as  silver  iodide  and  chloride,  whence  its  application  in  photography  and 
in  the  metallurgy  of  silver.  Sodium  thiosulphate  dissolves  iodine  in  large  quantity, 
whence  its  application  in  chlorometry  and  generally  in  the  iodometric  methods.  A 
solution  of  sodium  sulphite  mixed  with  thiosulphate  dissolves  malachite  and  azurite  in 
the  state  of  cuprous  sodium  thiosulphate — a  property  utilised  by  Stromeyer  for  the 
extraction  of  copper.  In  sulphuric  acid  works  it  is  sometimes  used  to  remove  arsenic 
from  the  chamber  acid,  being  transformed  along  with  arsenious  acid  into  arsenic  sulphide 
and  sodium  sulphate.  It  is  also  used  for  preparing  mercurial  and  antimonial  vermilion, 
for  obtaining  aldehyde-green  (emeraldine),  for  dyeing  wool  with  eosine,  as  well  as 
(Lauth,  1875)  for  a  mordant  in  dyeing  wool  a  methyl-green.  Lead  and  also  copper 
thiosulphates  are  successfully  used  for  non-phosphoric  matches. 

The  determination  of  free  sulphurous  acid  in  presence  of  sulphides  is  effected 
according  to  the  equations  : — 

1.  S03  +  2H2O  +  2!  =  H2S04  +  2lH. 

2.  Na2S03  +  H20  +  2!  =  Na2S04  +  2lH. 

3.  CaS03  +  SO,  +  3H20  +  4I  =  CaS04  +  H,S04  +  4lH. 
There  is  formed  hydriodic  acid  in  quantity  equivalent  to  the  iodine  used ;  the  sul- 
phurous acid  becomes  sulphuric  acid.  If  the  sulphurous  acid  was  free  there  is  produced 
a  corresponding  quantity  of  free  sulphuric  acid.  If  at  the  end  of  the  titration  with 
iodine  the  total  quantity  of  the  free  acids  is  determined  alkalimetrically  and  that  of  the 
hydriodic  acid  is  deducted,  we  obtain  the  quantity  of  the  free  sulphuric  acid  formed,  and, 
consequently,  that  of  the  free  sulphurous  acid.  This  process  is  suitable  for  the  determi- 
nation of  the  sulphuric  acid  of  the  pyrites  furnace  gases,  if  the  decolorised  solution  of 
iodine  resulting  from  the  determination  of  the  sulphurous  acid  of  the  gases  is  titrated  with 
decinormal  soda.  What  more  is  used  than  corresponds  to  the  acids  formed  from  SO, 
and  iodine,  shows  the  sulphuric  acid  present  in  the  furnace  gases. 

*  The  only  remedy  is  to  utilise  the  heat  of  fuel  better,  thus  reducing  the  quantity  of  coal  con- 
sumed. "  Smoke  consumption  "  is  not  of  the  slightest  use  in  this  respect.  In  manufacturing 
processes,  the  sulphurous  acid  given  off  may  in  many  cases  be  absorbed  by  passing  it  through  lime. 


262 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


SULPHURIC  ACID. 

Three  kinds  of  sulphuric  acid  are  distinguished  in  manufactures  and  in  com- 
merce : 

a.  The  fuming  or  Nordhausen  sulphuric  acid,  distilled  (formerly)  from  ferric  sul- 
phate, or  obtained  by  dissolving  sulphuric  anhydride  in  ordinary  sulphuric  acid. 

b.  Solid  oil  of  vitriol  and  sulphuric  anhydride. 

c.  Ordinary  sulphuric  acid.* 

Fuming  Sulphuric  Acid. — At  a  red  heat  all  the  sulphates,  except  those  of  the  alkalies 
and  alkaline  earths,  are  decomposed,  giving  off  vapours  of  sulphuric  acid  (or  of  sul- 
phurous acid  and  oxygen).  Ferrous  sulphate  was  formerly  preferred  on  account  of  its 
cheapness.  At  a  red  heat  it  is  decomposed  into  ferric  oxide,  sulphuric  anhydride,  and 
sulphurous  acid  :  2FeS04  =  Fe2O3  +  S08  +  SO2. 

Sulphuric  anhydride  could  be  obtained  in  this  manner,  if  it  were  possible  to  keep  it 
free  from  water,  on  the  large  scale.  Water,  however,  always  remains  behind,  and  there 
is  consequently  obtained  the  so-called  fuming  acid,  a  variable  mixture  of  sulphuric  anhy- 
dride (teroxide,  S03)  with  sulphuric  acid  (H2S04),  or  a  mixture  of  sulphuric  acid  with 

pyrosulphuric  acid  (H2S2O.)  in  vary- 

Kig.  256.  ing   proportions.     In  the  Bohemian 

vitriol  works  there  is  used  the  very 
impure  copperas  (ferrous  sulphate) 
obtained  by  boiling  down  the  mother 
liquors,  which  contain  a  considerable 
quantity  of  ferric  sulphate.  The 
decomposition  of  the  anhydrous  salt 
proceeds  as  follows  : 


The  preparation  of  fuming  sul- 
phuric acid  from  sulphur  shales 
(vitriolic  slate)  is  effected  in  Bohemia 
as  follows  : — The  shales  are  allowed  to 
weather  by  prolonged  exposure  to  the 
air  and  are  then  lixiviated.  The 
pyrites  present  in  the  shales  is  oxid- 
ised first  to  ferrous  sulphate,  and 
then  to  ferric  sulphate.  The  lye  ob- 
tained is  evaporated  to  dryness  and 
dehydrated,  as  far  as  possible,  in 
pans.  The  dry,  fused  saline  mass 
(vitriol  stone)  is  a  hard,  greenish- 
yellow  mass,  which  is  further  heated  in  a  reverberatory  in  order  to  convert  the 
remaining  ferrous  sulphate  to  ferric  sulphate,  and  is  then  ignited  in  the  burning 
stoves  (Fig.  2.56).  This  is  a  galley  furnace,  in  which  there  are  two  ranks  of  fire- 
clay flasks,  the  necks  of  which  are  built  in  such  a  manner  that  the  mouths  of  the 
receivers  can  be  applied  and  luted  on.  When  the  flasks,  each  of  which  contains  i  £  kilo, 
of  the  mass,  have  been  charged,  heat  is  applied.  The  watery  sulphuric  acid,  con- 
taining sulphurous  acid,  is  not  generally  collected.  But  as  soon  as  white  vapours  of 
anhydrous  sulphuric  acid  appear,  th#  receivers  are  fixed  and  luted  on  and  the  distilla- 
tion begins.  The  process  takes  from  twenty-four  to  thirty-six  hours.  The  flasks  are  then 

*  This  last  kind,  known  on  the  Continent  as  English  sulphuric  acid,  is  technically  spoken  of  in 
this  country,  when  undiluted,  as  oil  of  vitriol,  or  double  oil  of  vitriol,  D.O.V. 


SECT,  in.]  SULPHURIC   ACID.  263 

charged  afresh,  and  the  same  receivers  are  applied  with  the  acid  which  has  already 
passed  over.  After  four  repetitions  the  acid  has  the  proper  concentration.  The 
residue  is  red  ferric  oxide  (colcothar,  Paris  red).  The  yield  of  fuming  acid  is  about  45 
to  50  per  cent,  of  the  weight  of  the  dehydrated  vitriol  stone.  Instead  of  distilling  the 
vitriol  stone,  a  ferrous  sulphate  is  sometimes  used,  prepared  from  colcothar  or  burnt  ore, 
and  sulphuric  acid,  the  iron  oxide  remaining  in  the  flasks  being  used  again. 

The  sodium  bisulphate  (NaHS04)  remaining  as  a  residue  on  preparing  nitric  acid 
from  soda-saltpetre  is  also  used  for  the  manufacture  of  fuming  sulphuric  acid.  When 
heated  to  fusion,  this  compound  gives  off  water  and  sodium  ;  pyrosulphate  remains,  and 
on  further  heating  to  about  600°  the  latter  is  split  up  into  sulphuric  anhydride  and 
neutral  sulphate  :  Na2S207  =  SO3  +  Na2S04.  The  anhydride  is  passed  into  sulphuric 
acid.  Wolters  recommends  for  the  preparation  of  the  anhydride  a  mixture  of 
magnesium  sulphate  and  sodium  pyrosulphate.  Far  below  a  red  heat,  sulphur  teroxide 
is  set  free,  and  there  remains  a  double  salt,  MgS04  +  Na2S04,  which  is  separated  into 
its  constituents  in  the  known  manner,  and  returns  to  the  circuit  of  the  manufacture. 

Properties.  —  Fuming  sulphuric  acid  is  a  light-brown,  thick,  oily  liquid,  of  spec.  gr. 
i*86  to  1*89,  and  consists  of  a  solution  of  the  anhydride  in  sulphuric  acid,  from  which 
the  anhydride  evaporates  even  at  common  temperatures,  forming  white  clouds  in  moist 
air.  In  the  cold,  pyrosulphuric  acid  separates  from  it  as  a  crystalline  mass,  fusible 
at  35°,  which,  if  gently  heated,  is  resolved  into  sulphuric  anhydride  and  sulphuric  acid  : 

H2S207  =  S03  +  H2S04. 

Formerly  it  was  used  only  for  dissolving  indigo  (  i  part  indigo  is  soluble  in  4  parts 
of  the  fuming  acid).  Recently  it  has  been  used  to  a  larger  extent  in  the  treatment  of 
ozokerite  and  in  the  production  of  various  tar-colours,  e.g.,  for  preparing  benzol 
disulphonic  acid,  by  heating  benzol  with  fuming  sulphuric  acid  in  the  manufacture  of 
eosine. 

Solid  Oil  of  Vitriol.  —  For  some  years  pyrosulphuric  acid,  H2S2Or,  has  been  met  with 
in  commerce.  It  is  obtained  by  dissolving  i  mol.  anhydride  in  i  mol.  sulphuric  acid, 


Sulphuric  anhydride  is  obtained  either  by  heating  ferric  sulphate,  perfectly  dehy- 
drated, or  Wolter's  mixture,  or  by  warming  strong  fuming  sulphuric  acid;  or, 
according  to  Winkler,  synthetically  (S02  +  O  =  S03),  by  resolving  sulphuric  acid  at  a 
red  heat  into  sulphurous  acid,  oxygen,  and  water,  the  latter  being  kept  back  by  means 
of  concentrated  sulphuric  acid,  the  mixture  of  sulphurous  acid  and  oxygen  being 
passed  over  ignited  platinised  asbestos,  where  it  is  again  converted  into  sulphur 
teroxide.  Messel  and  Squire,  of  London,  use  platinised  pumice.  The  real  anhydride, 
S03,  is  at  common  temperatures  a  colourless  liquid,  which  below  +  16°  solidifies  to  felted 
asbestos-like  needles,  and  boils  at  46°  to  47°.  The  so-called  anhydride  of  commerce, 
which  is  sold  in  sheet-iron  boxes  containing  60  kilos.,  consists  of  98  per  cent,  anhydride 
and  2  per  cent.  H2SO4. 

Ordinary  Sulphuric  Acid.  —  By  far  the  largest  quantity  of  sulphuric  acid  is  prepared 
by  the  oxidation  of  sulphurous  acid  obtained  on  the  combustion  of  sulphur,  or  on 
roasting  pyrites  and  blende;  the  oxidation  is  effected  by  means  of  nitric  acid. 
According  to  the  equation,  S,  +  302  +  2H2O  =  2H2S04,  64  kilos,  of  sulphur  require  67 
cubic  metres  of  oxygen,  or  320  cubic  metres  of  atmospheric  air,  along  with  36  kilos. 
of  watery  vapour,  in  order  to  yield  196  kilos,  sulphuric  acid.  For  the  production  of 
sulphuric  acid  the  roasting  gases  must  contain  to  100  vols.  sulphurous  acid  at  least  50 
vols.  oxygen.  In  fact,  an  excess  of  oxygen  must  be  present  if  the  reactions  are  not  to 
be  too  slow.  With  regard  to  the  sulphuric  acid  already  formed,  the  gases  from 
sulphur  when  passed  into  the  lead-chambers  contain  12  per  cent,  by  volume  of 
sulphurous  acid  ;  if  from  pyrites,  7  per  cent.  ;  if  from  blende,  6  to  7  per  cent. 

Lead-Chambers.  —  As  long  as  we  are  compelled,  in  the  manufacture  of  sulphuric 


264  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

acid,  to  use  the  requisite  substances  as  gases,  and  especially  to  use  oxygen  in  the  state 
of  atmospheric  air,  large  chambers  are  necessary,  which  must  be  cheap  to  construct, 
air-tight,  and  must  consist  of  a  material  not  attacked  by  the  nitrous  gases  and  vapours 
or  by  sulphuric  acid. 

Among  the  many  materials  which  have  been  proposed,  one  only,  lead,  fulfils  most 
of  these  demands.  In  the  Fouche-Lepellitier  works  at  Javel,  near  Paris,  a  gutta- 
percha  chamber  was  in  use  in  the  years  1860-1870. 

As  to  the  sort  of  lead  which  is  most  suitable  for  the  construction  of  chambers,  it 
is  generally  assumed  that  metals  are  the  less  easily  attacked  by  an  acid  the  purer  they 
are.  Careful  researches,  however,  proved  that  lead  is  attacked  by  sulphuric  acid  the 
more  readily  the  purer  it  is.  On  the  other  hand,  according  to  a  communication  from 
J.  Glover,  in  order  to  test  the  suitableness  of  lead  for  the  construction  of  chambers, 
sheets  of  different  alloys  were  placed  for  no  days  in  a  lead-chamber.  Pure  lead  was 
found  to  lose  7*5  per  cent.  Lead  alloyed  with  copper  and  antimony  experienced  the 
following  losses : — 

Copper.  Loss.  Antimony.  Loss. 

O'l  percent.  7'i  percent.  ...  0*1  percent.  8'i  percent. 

0-2        „  7'i        »>  •••  °'2        ».  9'2        „ 

0-3        „  7'5        »  •••  °'3        »  10-9        „ 

0-4        „  9'1        »  •••  °'4        >»  "'6        ii 

0-5        „  8-5        „  ...  0-5        „  11-9        „ 

N.  Cookson  heated  lead  with  sulphuric  acid  of  different  strengths.  He  found  that 
strong  acids  at  high  temperatures  attacked  antimoniferous  lead  more  than  pure  lead, 
but  weaker  acid  at  lower  temperatures  attacked  antimoniferous  lead  less  than  pure 
lead. 

It  has  been  repeatedly  observed  that  some  coleopterous  insects  perforate  the  plates 
of  the  chambers.  At  the  Mulden  works,  wood  wasps  have  made  holes  in  the  lead. 

The  lead  is  rolled  out  in  plates  o'6  metre  in  breadth,  and  of  a  thickness  of  3  to  8 
millimetres.  The  chamber  consists  of  two  parts :  the  bottom,  which  has  a  plate-like 
form,  and  is  bent  up  on  all  sides  to  the  height  of  36  to  54  centimetres ;  and  the  side  walls, 
consisting  of  one  piece,  which  stand  upon  the  bottom  like  a  bell.  Both  these  parts  are 
made  of  a  great  number  of  sheets  soldered  together.  The  chambers  are  secured  in  a 
frame  of  woodwork,  consisting  of  uprights,  horizontal  beams,  &c.  The  sides  are  first 
covered  with  lead  sheets,  which  are  soldered  together  at  the  edges  by  the  autogenous 
process.  After  the  sides  are  completed,  the  bottom  and  the  top  are  covered  with  lead 
plates.  On  the  outside  of  the  chamber  several  strips  of  lead,  from  18  to  20  centimetres 
in  breadth  and  36  centimetres  in  length,  are  soldered  fast  and  secured  to  the  woodwork 
with  iron  nails.  The  covering  plate  is  secured,  in  the  same  manner,  to  beams  which 
run  across  the  chamber. 

The  bottom  of  the  chamber  is  always  covered  with  acid ;  the  lower  corners  of 
the  side  walls  dip  freely  into  the  liquid,  forming  a  hydraulic  joint.  Hence,  acid  can  be 
drawn  off  at  any  time,  and  in  any  place.  In  and  on  the  chambers  there  are  arranged 
man-holes  in  the  sides  (for  executing  repairs),  pipes  for  conveying  the  gases  from  the 
furnaces  and  steam  from  the  boiler,  pipes  for  carrying  off  the  chamber  gases,  glass 
discs  for  observing  the  state  of  the  chambers  and  the  progress  of  the  formation  of  the 
acid,  generally  placed  in  two  opposite  walls  in  the  direction  of  the  incident  light; 
hydrometers  and  thermometers,  the  latter  of  which  are  attached  to  the  sides  for  the 
estimation  of  the  temperature  at  different  parts  of  the  chamber.  In  order  to  take, 
from  time  to  time,  specimens  of  the  acid  which  is  being  formed,  there  are  in  some 
works  so-called  dropping-tables,  which,  at  the  height  of  i  metre  from  the  bottom, 
support  a  bent  plate  with  a  turned-up  edge,  o-6  metre  in  length  and  0*5  metre  in 
breadth.  The  acid  which  collects  upon  this  plate  is  conveyed  through  a  lead  tube  to  a 


SECT.    III.] 


SULPHURIC  ACID. 


265 


beaker  placed  outside  the  chamber,  for  the  determination  of  its  strength.  The 
chambers  are  covered  in  with  a  roof,  which  is  necessary  in  Germany,  Belgium,  and 
France,  whilst  in  Britain,  as  the  temperature  varies  much  less  at  different  seasons  of 
the  year,  the  chambers  commonly  stand  in  the  open  air.  In  recent  works  the  chambers 
are  often  supported  on  pillars  of  masonry,  so  that  the  space  below  is  available  for  the 
erection  of  pyrites  kilns,  &c. 

Arrangements  for  collecting  the  Nitrous  Vapours. — In  order  to  reduce  the  loss  of 
nitre  as  far  as  possible,  the  nitrous  constituents  (nitrous  and  hyponitric  acid)  are 
withdrawn  from  the  gases  and  vapours  escaping  from  the  chambers  before  they  can 
pass  out  into  the  air,  and  are  thus  made  again  available  for  the  process  of  acid  forming. 
This  object  is  effected  almost  everywhere  by  means  of  sulphuric  acid  in  the  absorbent 
coke-tower  proposed  by  Gay-Lussac.  This  consists  of  a  cylinder  of  lead  about  10  metres 
high,  closed  gas-tight  above,  and  standing  below,  like  the  chambers,  in  a  lead  vessel, 
filled  with  acid,  so  as  to  form  a  hydraulic  joint  (Kg.  257).  The  inner  walls  of  such 


cylinders  are  often  lined  with  thin  fire- 
proof stones.  The  tower  is  filled  with 
coarse  pieces  of  coke,  but  sometimes  glass 
balls,  pieces  of  broken  drain-pipes,  &c.,  are 
used.  The  distribution  of  the  sulphuric 
acid  over  the  pieces  of  coke  is  effected  by 
means  of  the  cistern  A,  from  which  a 
stream  of  acid  flows  uninterruptedly  into 
an  oscillating  trough  fixed  over  a  lead- 
plate  with  about  twenty  tubes.  From 
these  tubes  the  acid  flows  into  the  tower. 
For  securing  a  constant  outflow  of  acid 
the  Mariotte  bottle  is  often  used,  or  the 
apparatus  shown  in  Fig.  258.  At  the 
side  of  the  acid  cistern,  A,  is  a  small  lead 

cylinder,  a  ;  the  tube  b  is  conical  at  its  mouth  and  secured  acid-tight  by  means  of  a 
leaden  plug,  m,  of  suitable  shape.  This  plug  is  fixed  on  an  iron  rod,  the  part  of  which 
below  the  plug  is  to  guide  it  in  its  upward  and  downward  movements  and  to  make  it 
always  fall  exactly  into  the  opening.  In  the  lead  cylinder  there  hangs  a  lead  jug,  fixed 
to  a  lever  by  means  of  a  chain,  which  at  its  other  end  is  connected  by  a  short  chain 
with  the  rod  of  the  lead  plug.  When  the  apparatus  is  to  act,  the  cistern  A  is  filled 
with  acid,  and  the  plug  is  fixed  in  the  aperture.  If  the  sulphuric  acid  is  to  flow  into 
the  tower  at  a  uniform  pressure  the  lead  jug  is  drawn  up  in  the  cylinder  and  its  chain 
is  secured  to  the  beam,  P,  which  is  set  horizontally.  The  plug-rod  is  now  also  secured 
to  the  beam.  If  the  jug  is  left  to  itself  the  plug  is  raised,  the  sulphuric  acid  flows 
through  the  tube  b  into  the  lead  cylinder,  and  the  jug  rises  swimming  on  the  acid 
in  proportion  as  the  level  of  the  acid  rises.  As  soon  as  the  jug  has  been  raised  18  to 


266  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

20  centimetres  the  plug  sinks  and  closes  the  tube  b.  If  the  cock,  c,  in  the  cylinder  is 
opened  the  sulphuric  acid  sinks,  and  with  it  the  jug ;  thereby  the  plug  is  lifted,  and  the 
level  in  the  lead  cylinder  is  restored  by  an  inflow  of  sulphuric  acid.  If  the  outflow 
cock,  c,  is  suitably  placed,  the  sulphuric  acid  flows  at  a  uniform  pressure  into  the 
coke-tower,  supposing  that  the  level  of  the  acid  in  the  cistern  A  never  falls  below 
1 8  centimetres. 

The  sulphuric  acid  is  forced  up  from  the  monte-jus,  D,  through  the  pipe  6,  into  the 
cistern  A.  The  gases  coming  from  the  lead  chambers  stream  into  the  coke- tower  at 
H,  and  pass  out  again  at  G,  after  having  lost  their  nitrous  constituents.  The  sul- 
phuric acid,  charged  with  these  ingredients  (nitrose),  runs  from  the  dish  of  the 
absorption-tower  through  the  pipe  k,  into  the  cistern  J3,  and  thence  into  a  monte-jus, 
which  convey  it  into  the  denitrifying  apparatus. 

In  the  works  of  Fikentscher,  at  Zwickau,  the  absorption  apparatus  consists  of 
eight  stoneware  pipes,  set  above  each  other,  of  o-8  metre  in  height  and  in  width; 
each  open  above,  and  provided  with  a  perforated  bottom.  On  each  pipe  there  are 
three  inclined  planes  of  stoneware,  on  which  sulphuric  acid  of  130°  Tw.  trickles 
down  as  it  enters  in  drops. 

In  order  to  test  the  remarkable  phenomenon  that  this  so-called  nitrose  of  the  Gay- 
Lussac  tower  contains  only  nitrous  acid,  even  when  the  entering  gases  show  consider- 
able quantities  of  hyponitric  acid,  G.  Lunge  examined  the  action  of  coke  upon  nitric 
acid.  Experiment  showed  that,  in  contact  with  coke,  the  nitric  acid,  dissolved  in  the 
sulphuric  acid,  was  almost  completely  reduced  to  nitrous  acid,  slowly  at  common 
temperatures,  but  very  rapidly  al  such  a  temperature  as  generally  prevails  in  the 
Gay-Lussac  tower.  Whether  this  is  immediately  effected  by  the  carbon  or  by  its 
action  upon  sulphuric  acid  (with  the  production  of  sulphurous  acid),  or  by  the  joint 
action  of  iron  sulphide  present  in  the  coke,  remains  undecided. 

The  absorptive  power  of  sulphuric  acid  for  nitrous  acid  differs  greatly  according  to 
its  concentration.  Acid  of  154°  Tw.  is  able  to  dissolve  more  than  three  times  as 
much  nitrous  acid  as  that  at  130°  Tw.  So  that,  in  using  the  stronger  acid,  there  is 
the  advantage  that  only  one-third  of  the  usual  quantity  of  acid  is  necessary.  Besides, 
the  greater  affinity  of  concentrated  acid  for  the  nitrous  vapours  is  a  greater  guarantee 
for  their  complete  absorption. 

Denitration  of  the  Nitrose. — The  acid  flowing  out  of  the  absorption-tower,  the 
nitrose,  is  a  solution  of  nitrosulphonic  acid,  S02.OH.N02,  in  sulphuric  acid.  The 
problem  is  to  decompose  this  nitrose  into  the  nitrous  compounds  and  into  pure  sul- 
phuric acid,  using  the  former  again  in  the  chamber  process. 

The  earlier  denitrating  appliances  all  depended  on  diluting  the  nitrose  with  hot 
water  or  steam,  or  with  both  together.  The  nitrosulphonic  acid  of  the  nitrose  is  re- 
solved into  sulphurous  acid  and  nitric  acid. 

This  decomposition  can  be  effected  in  the  stage-apparatus,  in  Gay-Lussac's  denitri- 
ficator,  in  the  boiling-drum,  or  in  the  cascade. 

The  stage-apparatus  is  a  small  lead  chamber,  of  a  few  cubic  metres  capacity,  in 
which  five  successive  lead  floors  are  soldered  at  different  heights.  They  leave  alter- 
nately, at  opposite  sides  of  the  chamber,  a  passage  free  for  the  sulphuric  gases,  which 
enter  beneath  the  lowest  floor,  traverse  the  apparatus  in  zig-zag,  and  above  the  highest 
stage  pass  into  the  lead-chamber  through  a  pipe.  The  nitrose  enters  through  the 
cover  of  the  apparatus  by  a  cock,  falls  upon  the  highest  floor,  then  upon  the  second 
and  third,  coming  in  contact  with  the  sulphurous  acid  all  the  way,  and  is  denitrated  at 
the  foot  of  the  apparatus,  so  that  it  may  be  either  drawn  off  directly  or  conveyed  into 
the  first  lead-chamber. 

Gay-Lussac's  denitrificator  consists  of  a  tower  of  sheet-lead,  into  which  the  furnace 
gases  enter  by  the  pipe,  M(  Fig.  259),  and  diffuse  themselves  under  the  grating,  G, 


SECT.   III.] 


SULPHURIC   ACID. 


267 


Fig.  259. 


Fig.  260. 


Fig.  262. 


upon  which  rests  a  bed  of  coke.  The  nitrose  crosses  from  the  cistern,  F,  and  is  distri- 
buted over  the  coke,  trickling  downwards  to  meet  the  ascending  gases,  and  passing  out 
denitrised  at  the  bottom  of  the  tower  through  the  tube,  t.  Both  in  the  stage  apparatus 
and  in  this  tower  apparatus  steam  is  introduced,  which  dis- 
tinguishes both  from  the  Glover  tower. 

The  denitrising  apparatus  devised  by  J.  Glover,  of  Wallsend, 
is  now  almost  universally  used  under  the  name  of  the  Glover 
tower. 

In  the  first  place,  this  tower  serves  as  a  concentrating  and 
cooling  apparatus,  as  hot  sulphurous  acid  is  conveyed  into  the 
tower  whilst  chamber  acid  meets  the  hot  gases.  Thus  the 
sulphurous  acid  is  cooled  and  the  chamber  acid  concentrated. 
The  watery  vapours  evolved  pass  into  the  lead  chambers, 
effecting  a  considerable  saving  in  steam  for  the  working  of 
the  chamber.  Besides,  the  Glover  tower  denitrises  the  nitrose 
which  is  decomposed  by  the  joint  action  of  ttie  steam  and  the 
sulphurous  acid,  so  that  the  concentrated  sulphuric  acid  run- 
ning off'  below  is  denitrised,  and  the  nitric  oxide,  set 
free,  enters  the  chamber  again,  where  it  again  mediates  the  formation  of  sulphuric 
acid. 

In  the  Glover  tower  the  chief  part  of  the  sulphuric  acid  present  in  the  roasting 
gases  is  separated  out,  so  that  by  this  arrangement  the  performance  of  the  lead-chambers 
is  decidedly  augmented. 

Recently  the  Glover  tower  has  been  also  used  for  bringing  the  nitric  acid  required 

in  the  sulphuric   acid   process   into  contact 
without  any  special  apparatus. 

The  Glover  tower  is  built  of  strong  lead 
plates,  surrounded  with  a  frame  of  wood. 
To  protect  the  lead  walls  there  is  a  lining  of 
fire-tiles  which  is  stronger  in  the  lower  part 
of  the  tower  than  in  the  upper  half.  The 
tower  is  filled  with  bricks  set  like  a  grating, 
or  with  fragments  of  quartz.  At  the  top 
of  the  tower  are  two  cisterns  of  wood  lined 
with  lead,  the  one  containing  nitrose  and  the 
ether  the  chamber  acid  to  be  concentrated. 
For  the  even  distribution  of  each  acid  there 
is  a  small  Segner's  wheel  provided,  made  of 
glass,  which  is  caused  to  rotate  by  the  outflow 
of  the  acid  which  it  distributes.  It  is 
arranged  that  both  acids  meet  within  the 
tower  and  flow  out  together.  The  roasting- 
gases  traverse  the  tower  from  below  upwards 
and  then  enter  the  lead-chamber. 

According  to  Herreshof ,  there  are  erected 
in  the  tower  (here  drawn  as  greatly  short- 
ened) cross  wells,  E  (Figs.  260,  261,  262),  over  which  large  pieces  of  quartz,  G,  are 
laid  across  and  form  a  vault.  Upon  these  are  laid  quartz  stones,  (7,  to  a  certain  depth 
so  that  they  leave  a  space  of  300-400  millim.,  next  to  the  lead  wall  of  the  tower,  It, 
All  large  gaps  on  the  side  of  the  heaped-up  material  are  filled  with  smaller  pieces 
of  quartz,  and  around  them  is  laid  a  thin  layer  of  quartz-sand,  which  during  the  building 
is  kept  in  its  place  by  means  of  iron  plates.  The  remaining  space  between  the  filling 


Fig.  261. 


Explanation  of  Terms. 
Schnitt  /—  Section  I. 
Schnitt  //—Section  II. 


268 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


and  the  lead  wall  is  filled  with  rather  fine  quartz-sand,  which  completely  prevents  the 
acid  from  touching  the  lead.  Iron  plates,  a,  are  secured  on  the  corner  pillars,  b,  so  that 
the  lead  casing  may  bear  the  weight. 

The  Glover  tower  is  the  simplest  and  cheapest  apparatus  for  concentrating  and 
denitrification,  as  in  it  sulphuric  acid  can  be  brought  to  a  strength  of  137°  or  even 

145°  Tw. 

The  general  arrangement  of  a  sulphuric  acid  works  is  shown  (diagrammatically)  in 
Fig.  263.  The  sulphurous  acid  evolved  in  the  furnace,  S,  from  sulphur,  pyrites,  or 
blende  is  let  pass  through  the  pipe,  r,  into  the  bottom  of  the  denitrising  apparatus,  G,  over 

Fig.  263. 


the  contents  of  which  the  nitrose  and — in  case  nitric  acid  is  not  evolved  in  the  furnaces, 
S,  from  nitre  and  sulphuric  acid — the  requisite  quantity  of  nitrie  acid  trickles  down. 
The  concentrated  acid  flows  off  below,  and  is  conveyed  away  if  it  is  not  forced  up  by  the 
monte-jus  to  the  cistern  of  the  Gay-Lussac  tower,  L. 

The  gases  pass  now,  along  with  the  steam  entering  by  the  tube  v,  into  the  first  lead- 
chamber,  A.  What  is  not  condensed  here  passes  from  the  bottom  through  the  tube  b, 
into  the  upper  part  of  the  second  lead-chamber,  £,  and  then  in  like  manner  into  the 
third,  C,  escaping  from  here  into  the  Gay-Lussac  tower,  L,  and  finally  go  off  at  n.  The 
three  chambers  may  be  built  either  separate  or  together,  as  the  figure  shows.  The 
sulphuric  acid  formed  (chamber  acid)  is  led  off  for  further  treatment.  The  nitrose 
formed  in  the  closed  Gay-Lussac  tower,  Z,  flows  through  o  into  the  monte-jus,  D,  and 
thence  by  means  of  compressed  air  (less  suitably  by  means  of  steam)  it  is  forced 
through  the  pipe  e  into  the  cistern,  /,  whence  it  arrives  into  the  Glover  tower,  G. 

We  must  notice  Laurent's  apparatus  for  raising  sulphuric  acid.  It  consists  of  a  tube 
of  lead,  vulcanite,  or  glass,  which  branches  off  directly  from  the  recipient  to  be  emptied, 
descends  more  or  less  deeply,  according  to  the  height  to  which  the  liquid  is  to  be 
lifted,  and  then  ascends  to  the  cistern  to  be  fed  above.  The  compressed  air  is  intro- 
duced at  the  bottom  of  the  longest  part  by  a  very  small  pipe  which  ascends  high  enough 
to  prevent  the  entrance  of  the  liquid  into  the  apparatus  for  compressing  the  air.  This 
arrangement  is  especially  convenient  for  raising  up  the  acid  to  the  Glover  towers. 

Mactear  recommends  the  form  shown  in  Fig.  264.     So  much  air  is  forced  in  through 


SECT.   III.] 


SULPHURIC   ACID. 


269 


the  pipe,  a,  thart  the  mixture  of  acid  with  air  in  the  ascending  pipe,  S,  is  raised  by  the 
column  of  the  affluent  acid.  The  air  escapes  at  v,  and  the  acid  flows  off  at  e.  If  no 
compressed  air  is  accessible,  a  Korting  suction  blast  is  attached  to  the  tube  v,  and  sucks 
up  the  necessary  quantity  of  air  through  the  tube  a.  If  the  acid  is  to  be  lifted  higher, 
a  monte-jus  is  used  and  a  part  of  the  compressed  air  is  allowed  to  enter  into  the  tube  /S, 
in  order  to  drive  the  acid  two  or  three  times  the  height  corresponding  to  the  pressure 
of  the  compressed  air. 

If  the  liquid  has  to  be  taken  from  a  flat  cistern,  n  (Fig.  265),  it  is  let  flow  into  a 
wide  tube,  c,  closed  below,  whilst  air  is  driven  in  through  a  narrow  tube,  a ;  the  mixture 
of  acid  and  air  rises  up  in  the  tube  e,  which  is  open  below. 

The  working  of  a  newly  installed  sulphuric  acid  plant  begins  by  pouring  upon  the 
bottom  of  the  chambers  sulphuric  acid  of  spec, 
gr.   1-45   (90°   Tw.)   to  such  a  depth  that  the  Fig.  264. 

walls  of  the  chamber  may  dip  into  the  acid  for 
about  3  centimetres.  If  the  bottom  has  been 
soldered  to  the  sides,  the  depth  of  the  acid  must 
be  12  to  1 8  centimetres. 

After  the   floor   of   the   chamber    is    thus 
covered  with  acid,  the  air  is  expelled  from  the 


system  of  chambers  by  admitting  sulphurous  f 
acid  from  the  pyrites  furnaces,  which  will  by 
this  time  have  come  into  action.  Then,  ac- 
cording to  the  kind  of  working,  either  liquid 
nitric  acid  is  allowed  to  enter  or  nitric  acid 
vapour  is  developed  from  the  nitre  pots  in  the 

sulphur  furnaces.  At  the  outset  nitre  is  used  in  excess  (10  to  15  per  cent,  of  the 
weight  of  the  sulphur),  afterwards  in  the  normal  proportion  of  4  to  6  per  cent,  as  soon 
as  the  temperature  of  the  walls  is  observed  to  rise,  which  is  generally  in  about  twenty- 
four  hours.  When  the  formation  of  sulphuric  acid  has  set  in,  which  may  be  known  by 
the  dew  of  condensed  acid  on  the  walls  (within)  of  the  lead-chamber  and  the  plugs  of 
the  trial-holes,  the  time  has  arrived  for  the  admission  of  steam. 

The  chambers  are  now  observed  three  to  four  times  daily,  noting  the  height  of  the 
thermometers  and  testing  the  acid  formed  and  the  gases  passing  in  and  out. 

In  general,  the  proportion  of  SO2  in  the  gases  which  enter  is  determined  by  means 
of  iodine  solution,  according  to  Reich.  In  the  summer  of  1876  the  author  repeatedly 
examined  the  gases  evolved  on  roasting  smalls  in  a  plate  furnace.  In  order  to  deter- 
mine the  proportion  of  sulphuric  acid  vapour  and  of  sulphurous  acid,  he  used  in  his 
apparatus  for  examining  smoke  gases,  petroleum  instead  of  water,  the  sample  of  gas 
being  drawn  up  through  a  porcelain  tube  as  quickly  as  possible  after  measurement  into  the 
potassa  tube,  and  after  dissolving  the  acids  into  pyrogallate  to  determine  the  oxygen. 
In  another  portion  drawn  simultaneously  S02  was  determined  by  the  process  of  Reich. 

A  series  of  experiments,  conducted  at  the  works  of  Meyer  and  Riemann,  near 
Hanover,  July  19,  1876,  gave: 


Place  of  Sample. 

S02  by  I. 

Total  Acids. 

0. 

Plate  2  from  below          .... 

0-96 

i  '4 

18-4 

,,     4                               .... 

1-52 

2'2 

16-6 

,,     6                               .... 

3'8i 

4'6 

12-5 

Collecting  pipe         

7'53 

8-6 

7'5 

The  gases  escaping  from  the  Gay-Lussac  contained  0*4  per  cent,  acid  gases  and 
4'4  per  cent,  oxygen. 

This  volumetric  process  makes  no  pretensions  to  great  accuracy ;  indeed,  the  real 


2 7o  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

proportion  of  sulphuric  acid  will  be  rather  greater.  It  has,  however,  the  advantage 
that  it  shows  in  four  or  five  minutes  the  total  quantity  of  acids  approximately,  and  the 
oxygen  accurately,  to  about  0-2  per  cent.  The  apparatus  for  the  determination  of 
S02  seems  more  suitable  for  checking  the  work  than  the  method  of  Reich,  as  the  pro- 
portion of  sulphuric  acid  often  exceeds  2  per  cent,  by  volume.  The  determination  of 
oxygen  in  the  exit  gases  deserves  attention,  as  irregularities  may  thus  be  quickly  and 
accurately  detected.  The  supply  of  air  to  the  pyrites  furnaces  must  be  so  regulated 
that  the  gases  issuing  from  the  Gay-Lussac  contain  3  to  6  per  cent,  oxygen. 

In  the  lead-chamber  in  which  the  production  of  sulphuric  acid  is  chiefly  effected, 
a  thermometer,  hanging  at  about  i^  metre  from  the  ground,  should  indicate  a  tempera- 
ture of  40°  to  50°.  If  the  chambers  grow  too  hot,  less  nitre  (or  nitric  acid)  is  taken ; 
if  they  are  too  cold,  more  must  be  added.  If  an  excess  of  steam  is  used,  there  is  formed 
a  dilute  acid,  which  takes  up  nitric  and  nitrous  acids  and  corrodes  the  lead  ;  sulphurous 
acid  also  may  be  taken  up.  If  there  is  a  deficiency  of  steam,  nitrous  acid  is  formed, 
and  leads  to  the  formation  of  so-called  chamber  crystals.  The  strength  of  the  acid 
formed  in  the  lead-chamber  shows  whether  the  influx  of  steam  is  normal  or  abnormal. 
If  the  acid  taken  in  the  first  third  of  the  chamber  has  a  sp.  gr.  of  1*60  =  120°  to  121° 
Tw.,  the  right  quantity  of  steam  is  being  admitted. 

The  mud  (so-called  white  lead)  collecting  in  the  chambers,  which  must  be  removed 
from  time  to  time,  varies  greatly  in  composition,  and  is  formed  by  the  action  of  the 
acids  upon  the  lead  and  its  impurities,  as  well  as  matter  introduced  from  the  furnaces 
in  the  shape  of  flue-dust.  It  often  contains  selenium,  sometimes  thallium  and  indium. 

Lead-Chamber  Process. — According  to  F.  Hurter,  the  following  main  equations 
regulate  the  process : — 

S02  +  H20  +  0  +  N02  =  H2S04  +  NO,  and, 
S02  +  H30  +  0  +  N203  =  H2S04  +  N203. 

He  shows  that  the  work  done  in  a  system  of  chambers  depends  essentially  on  the 
quantity  of  nitrogen  compounds  contained  in  the  gases  and  on  the  strength  of  the  acid 
produced.  The  work  of  the  succeeding  chambers  diminishes  almost  in  a  geometrical 
series.  The  same  must  be  said  of  the  excess  of  temperature  of  the  chambers  over  that 
of  their  surroundings.  The  temperature  of  the  first  chamber  of  a  system  depends  on 
what  fraction  of  the  entire  system  is  taken  up  by  its  space. 

According  to  the  experiments  of  Lunge  and  Naef ,  in  a  normal  state  of  the  chambers 
the  proportion  of  sulphurous  acid  diminishes  very  rapidly  from  the  entrance  to  the 
middle  of  the  first  chamber,  i.e.,  from  7  to  ry  or  1-9  per  cent. ;  hence  here  70  per  cent, 
of  the  sulphurous  acid  has  already  been  converted  into  sulphuric  acid;  this  agrees 
well  with  the  results  of  earlier  observers,  and  with  Hurter's  theory.  From  the  middle 
to  the  end  of  the  first  chamber,  the  S02  decreases  very  little,  corresponding  to  a  con- 
version of  about  4  per  cent,  of  its  initial  quantity  into  sulphuric  acid.  With  the 
entrance  into  the  second  chamber,  the  reaction  is  suddenly  intensified,  and  at  its  middle 
there  is  only  from  0*2  to  0-4  per  cent,  sulphurous  acid  present,  so  that  in  this  way  20 
per  cent,  has  been  converted  into  sulphuric  acid.  From  here  to  the  end  of  the  system, 
on  account  of  the  great  dilution  of  the  gases,  and  to  reach  a  practical  maximum  (it  is 
never  absolutely  complete),  considerable  chamber  space  is  still  needed.  If  the  supply  of 
nitre-gases  is  insufficient,  the  proportion  of  sulphurous  acid  decreases  less  rapidly,  and 
the  process  goes  on  more  in  the  second  and  third  chamber. 

Hence  it  appears  that  the  formation  of  sulphuric  acid  goes  on  in  the  outset  with 
great  energy,  that  it  grows  very  sluggish  at  the  back  of  the  chamber,  and  that  in  the 
second  chamber  the  reaction  is  intensified.  The  only  explanation  to  be  found  is  that 
in  the  last  part  of  the  first  chamber,  owing  to  the  dilution  of  the  gases  with  90  per 
cent,  nitrogen,  the  molecules  of  sulphurous  acid  do  not  find  sufficient  N203  and  0, 
which  are  again  accumulated  in  other  parts,  but  that,  on  passing  through  the  pipe 


SECT,  in.]  SULPHURIC  ACID.  271 

leading  into  the  second  chamber,  an  intimate  mixture  of  the  gases  is  effected,  so  that 
the  molecules  of  the  three  active  gases  are  again  brought  sufficiently  close  to  react 
upon  each  other.  Hence  the  best  system  should  be  a  larger  number  of  smaller 
chambers.  Certainly,  doubtless  with  a  regard  to  the  economy  of  lead  and  of 
room,  this  system  has  of  late  been  abandoned,  and  in  some  works  the  entire  system 
has  been  made  to  consist  of  a  single  large  chamber.  But  such  attempts  cannot  have 
proved  successful,  as  they  are  very  uncommon,  and  some  who  had  adopted  the  one- 
chamber  system  have  gone  back  to  the  use  of  several  chambers.  It  seems  that  a 
frequent  passage  through  connection-pipes,  and  the  intermixture  of  gases  thus  effected, 
are  advantageous.  In  the  atmosphere  of  the  last  chamber,  only  N203  was  found  in 
normal  working. 

Formation  of  Sulphuric  Acid  in  the  Lead-Chambers. — According  to  Gr.  Lunge,  this 
process  depends  chiefly  on  the  intermediate  formation  of  nitrosylsulphuric  acid.  This 
is  formed  from  sulphur  dioxide,  oxygen,  and  nitrous  acid : 

2S02  +  N203  +  0,  +  HS0  =  2(S08,OH,ONO), 

and  is  immediately,  in  contact  with  an  excess  of  water,  resolved  into  sulphuric  acid  and 
nitrogen  trioxide : 

a(SO,,OH,ONO)  +  H20  =  2S02(OH)2  +  N,08, 

which  with  water  forms  nitrous  acid  and  water,  so  that  the  process  is  repeated.  For 
the  front  part  of  the  system  of  chambers  we  must  also  consider  that  here  a  part  of 
the  nitrosylsulphuric  acid  is  denitrised  by  sulphurous  acid  : 

2(S02,OH,ONO)  +  S02  =  2H20  =  3SO4H2  +  2NO, 

and  that  the  nitrogen  oxide  formed  in  this  manner  with  oxygen,  sulphurous  acid,  and 
water  forms  directly  nitrosylsulphuric  acid : 

2S02  +  2NO  +  30  +  H,0  =  2(S02,OH,ONO). 

As  a  secondary  reaction  the  latter  can  also  be  formed  by  the  action  of  nitric  acid 
(whether  originally  introduced  or  formed  afresh)  upon  sulphur  dioxide : 

S02  +  N02,OH  =  S02,OH,ONO. 

The  direct  formation  of  sulphuric  acid  from  sulphurous  acid  by  the  reduction  of 
N02  and  N208 :  SO,  +  N02  +  H20  =  S04H2  +  NO  ;  S02  +  N203  +  H20  =  S04H2  +  2NO, 
certainly  takes  place  to  a  trifling  extent,  though  latterly  this  process  is  taken  for  the 
main  reaction.  Hyponitric  acid  does  not  occur  in  the  normal  chamber  process,  and 
nitric  oxide  appears  only  at  the  beginning,  in  virtue  of  a  secondary  reaction  entering 
then  in  the  direct  reaction,  of  condensation  :  S02  +  N02.OH  =  S02,OH,ONO. 

Lunge  does  not  view  the  chamber-process  as  an  alternating  reduction  and  oxidation 
of  the  nitrogen  oxides,  but  as  a  condensation  of  nitrous  acid  or  nitric  oxide  with  sul- 
phurous acid  and  oxygen  to  nitrosulphuric  acid,  and  a  splitting  off  again  of  the  nitrous 
acid  from  the  latter  by  the  action  of  water. 

Under  certain  circumstances  nitrous  oxide  is  known  to  be  formed  as  a  product  of 
the  reaction  of  sulphurous  acid  and  nitrous  acid.  To  this  result  the  "  chemical "  loss 
of  nitre  in  the  manufacture  of  sulphuric  acid — in  contradistinction  to  the  mechanical 
losses  by  imperfect  absorption  in  the  Gay-Lussac  tower — and  the  nitrogen  in  the 
chamber  acid  are  generally  ascribed. 

It  cannot  be  theoretically  denied  that  under  very  unfavourable  circumstances  the 
reduction  of  nitric  oxide  may  go  as  far  as  to  free  nitrogen,  but  it  has  not  been  demon- 
strated in  practice.  It  has  been  shown,  firstly  by  R.  Weber,  then  by  Lunge,  that  the 
reduction  of  nitric  oxide  by  sulphurous  acid  to  N20  occurs  only  in  presence  of  water, 
or  of  sulphuric  acid  more  dilute  than  that  found  in  the  chambers.  Hence  a  formation 
of  N20  can  occur  only  if  an  excess  of  water  is  present,  which  is  very  rarely  the  case,  and 
with  good  work  the  "  chemical "  loss  of  nitre  is  very  small,  probably  not  o-5  per  cent. 

Another  abnormal  reaction  leads  in  practice  to  far  more  losses  of  nitre,  namely, 
the  formation  of  hyponitric  acid  in  the  last  part  of  the  system  of  chambers.  This 


27 2  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

causes  the  appearance  of  nitric  acid  in  the  bottom  acid  of  the  last  chambers,  but 
not,  or  very  rarely,  the  nitrose  of  the  Gay-Lussac  tower,  as  it  is  here  reduced  by 
coke,  perhaps  with  the  co-operation  of  the  last  traces  of  sulphurous  acid.  It  is  said 
to  have  been  observed  in  practice  that  under  such  circumstances  red  vapours 
escape  unabsorbed  from  the  Gay-Lussac  tower.  Lunge  has  shown  that  the  formation 
of  NO,  is  quite  independent  of  the  quantity  of  oxygen  present,  and  that  it  occurs 
with  abnormally  low,  with  normal,  and  with  abnormally  high  proportions  of  nitre. 
The  process  of  the  formation  of  sulphuric  acid  is  then  at  an  end  before  the  gases 
have  left  the  chambers.  In  the  latter  part  of  the  system  there  is  no  mist  of 
sulphuric  acid,  nor  does  there  exist  any  appreciable  quantity  of  sulphurous  acid.  The 
conditions  for  the  normal  process,  as  developed  above,  are,  therefore,  here  wanting. 
The  nitrous  acid,  which  now  meets  with  no  bodies  with  which  it  can  form  permanent 
combinations,  is  by  degrees  dissociated  in  the  large  excess  of  air,  and  is  partially 
oxidised  to  N02.  The  NO2  comes  in  reaction  with  the  bottom  acid,  and  yields  with  it 
equal  molecules  of  nitrosylsulphuric  acid  and  nitric  acid.  Another  portion  of  the 
N02  passes  with  the  exit  gases  into  the  Gay-Lussac  tower,  and  it  was  formerly  said 
not  to  be  here  absorbed.  This  has  been  shown  to  be  utterly  erroneous,  but  it  might 
easily  happen  that  a  coke-tower  sufficient  for  ordinary  circumstances  is  insufficient 
under  such  circumstances,  and  that,  therefore,  some  nitric  gas  escaped  into  the  air.  It 
would  be  an  abnormal  condition  of  the  chambers,  with  an  excess  of  nitre-gases. 

Much  worse  is  the  course  of  the  chamber-process,  if  the  nitre  is  insufficient,  whether 
too  little  has  been  used  at  first,  or  that,  in  consequence  of  the  inadequate  size  of  the 
Gay-Lussac  tower,  the  recovery  of  the  nitrous  acid  is  imperfectly  effected.  The  forma- 
tion of  sulphuric  acid  is  stopped  at  the  back  of  the  system,  not,  as  in  the  last  case, 
because  the  sulphurous  acid  is  exhausted,  but  because  there  is  too  much.  Now,  there- 
fore, a  denitrifi cation  of  the  nitrosylsulphuric  acid  has  to  occur  at  this  wrong  place  : 

2(S02,OH,ONO)  +  S02  +  2H20  =  sS04H2  +  2NO, 

and  much  nitric  oxide  is  formed,  the  atmosphere  of  the  chambers  losing  its  yellow  colour, 
either  partly,  or  in  very  bad  cases  altogether.  In  all  cases  the  temperature  falls  below 
the  normal  height,  i.e.,  that  favourable  for  the  formation  of  sulphuric  acid,  and,  in  spite 
of  the  presence  of  much  oxygen,  the  combination  of  nitric  oxide  and  sulphurous  acid  goes 
on  very  sluggishly.  Water  is  often  present  in  excess  in  the  air  of  the  chambers,  and 
there  is  often  nothing  to  prevent  the  nitric  oxide  from  forming,  with  the  oxygen  and  the 
water,  nitric  acid,  which,  as  the  temperature  is  here  much  lower,  and  there  is  much  less 
sulphurous  acid  present  than  in  the  front  part  of  the  chambers,  passes  unreduced  into 
the  bottom  acid,  and  makes  the  atmosphere  of  the  chambers  still  poorer.  Yet  the 
bottom  acid  is  not  "  nitrous  "  in  the  sense  used  by  manufacturers,  since  it  gives  off  no 
red  fumes  if  mixed  with  hot  water,  because  the  nitrosylsulphuric  acid  is  wanting. 
Also  as  sulphurous  acid  predominates,  and  there  is  almost  no  sulphuric  acid  in  the  air 
of  the  chambers,  but  only  water,  the  formation  of  nitrous  oxide  (NaO)  goes  on  freely. 
This  signifies  a  total  loss  of  nitre  ;  and  equally  lost  is  the  nitric  acid  contained  in  the 
bottom  acid  if  the  acid  is  consumed  directly,  and  the  nitric  oxide  arriving  unchanged  in 
the  Gay-Lussac  tower  is  lost  also.  This  still  encounters  oxygen,  but  not  only  is  its 
quantity  insufficient,  but  the  excess  of  sulphurous  acid  acts  here  at  the  wrong  place  as  a 
denitrifier,  and  can  even  destroy  nitrosylsulphuric  acid,  if  any  is  present.  The  nitric 
oxide  escaping  from  the  tower  forms  red  fumes  in  contact  with  the  air, whilst  the  "  lantern  " 
of  the  tower  is  white,  as  may  often  be  observed.  All  these  facts  together  lead,  not  only 
to  great  loss  of  sulphurous  acid,  and  consequently  to  a  poor  yield  of  sulphuric  acid,  but 
also  to  a  great  loss  of  nitre,  and  involves  a  progressive  impoverishment  of  the  chambers 
in  their  stock  of  oxygen  transferrers.  Hence  the  well-known  phenomenon  which  has 
been  recently  confirmed  by  Eschellmann,  that  if  we  have  been  too  economical  of  nitre, 
and  the  above  disease  has  attacked  the  chambers,  it  is  necessary  to  add  many  times  the 


SECT,  m.]  SULPHURIC  ACID.  273. 

quantity  of  nitric  acid  which  has  been  economised,  in  order  to  get  them  back  into  a. 
normal  condition. 

It  is  important  that  these  results  take  place  at  the  end  of  the  set  of  chambers. 
This  is  the  reason  why  nitric  oxide  does  not  enter  into  the  reaction,  although,  even 
when  the  chambers  are  working  badly,  there  is  almost  always  oxygen  enough  to  con- 
vert the  sulphurous  acid  into  H2S04.  But  in  the  first  place  the  temperature  is  too  low, 
probably  far  below  the  most  favourable  point,  as  the  main  reaction  takes  place  at  the 
hottest  point  of  the  system ;  secondly,  there  is  no  longer  time  for  the  molecules  of  oxygen 
distributed  in  a  large  volume  of  nitrogen  to  meet  with  the  remaining  substances  in, 
sufficient  quantity  ;  long  before  the  oxygen  is  quite  exhausted  the  gaseous  mixture- 
has  arrived  at  the  end  of  the  system,  and  nitric  oxide,  sulphur  dioxide,  and  oxygen 
escape  together  into  the  outer  air,  all  diffused  in  a  large  excess  of  nitrogen. 

Nothing  in  the  practice  of  the  sulphuric  acid  manufacture  is  more  distinctly  proved 
than  that  the  process  works  satisfactorily  only  in  presence  of  a  large  excess  of  oxygen 
and  of  nitrous  acid,  the  latter  of  which  is  mainly  recovered  in  the  Gay-Lussac  tower ;. 
if  there  is  only  a  slight  excess,  sulphurous  acid  always  escapes  into  the  air.  Even  with 
a  large  excess  of  oxygen,  a  perfect  oxidation  of  the  sulphurous  acid  is  impracticable. 
We  seem  to  have  reached  the  practically  best  limit  when  the  exit  gases  contain  only 
0*5  per  cent,  of  the  sulphurous  acid  originally  present.  We  have  here  to  do  with  one 
of  those  reversible  reactions  whose  progress  can  be  tumed  in  the  desired  direction  by 
certain  external  conditions,  such  as  the  action  of  the  mass  of  one  of  the  ingredients,  but 
can  seldom  be  made  absolutely  complete.  With  an  excess  of  oxygen  and  nitrous  acid 
the  reactions  of  condensation  predominate — 

2S02  -i-  N2O3  +  20  +  H2O  =  2SO2.OH.ONO  and 

2S02  +  2NO  +  30  +  H2O  =  2S02.OH.ONO ; 

therefore  the  conjunction  of  S02,  N203,  and  O,  characterised  as  the  main  reaction  of  the 
entire  process,  and  H2O  to  S02.OH.ONO  ;  but  if  there  is  a  relative  excess  of  sulphurous 
acid  the  reactions  of  denitration  predominate — 

2S02.OH.ONO  +  S02  +  2H20  =  3H2S04  +  2NO, 

by  which  the  chamber  crystals  of  sulphuric  acid  are  again  split  up  into  H2SO4 
and  NO.  The  nitric  oxide  cannot  further  enter  into  reaction  at  the  end  of  the 
system,  and  escapes  unutilised,  as  the  Gay-Lussac  tower  cannot  retain  it.  This  in- 
vertedre  action  corresponds  to  that  which  occurs  with  an  excess  of  sulphuric  acid : 
SO4H2.  +  NOOH  =  SO2.OH.ONO  +  H20.  If  water  is  in  excess  we  have  the  reaction  : 
S02  +  OHONO  +  H20  =  S02(OH),  +  NOOH. 

In  the  lead  chamber  process  consequently  a  relatively  large  excess  of  oxygen  and 
nitrous  acid  is  necessary. 

It  is  now  intelligible  how  to  a  certain  extent,  according  to  practical  experience, 
increased  chamber  room  and  an  increased  supply  of  nitre  compensate  each  other.  If 
under  the  other  suppositions  of  the  last  described  progress  of  a  chamber,  with  an  in- 
sufficient supply  of  nitre,  the  chamber  room  in  one  case  is  larger  than  in  another,  in  the 
former  case  more  molecules  of  sulphurous  acid  will  meet  with  the  necessary  quantities 
of  oxygen  and  the  oxides  of  nitrogen  than  in  the  latter,  because  more  time  is  given 
for  intermixture ;  hence  the  excess  of  the  two  latter  constituents  need  not  be  so  large. 
As  is  well  known  in  practice,  the  supply  of  oxygen  must  be  carefully  regulated  by 
establishing  the  correct  draught,  and  modifying  it  in  accordance  with  any  change  of  the 
atmospheric  conditions. 

In  the  sulphuric  acid  manufacture  there  is  little  left  to  be  learned  from 
theory.  In  the  utilisation  of  the  sulphur  we  have  arrived  nearly,  or  quite,  at  the 
utmost  limit  fixed  by  the  inversion  of  the  reaction,  and  the  consumption  of  nitre  can 
scarcely  be  brought  below  the  small  proportion  with  which  the  best  arranged  and  best 
managed  establishments  are  now  working.  We  might  perhaps  desire  to  produce  con 

s 


274  CHEMICAL  TECHNOLOGY.  [SECT.  -in. 

centrated  acid  at  once  in  the  chamber.  But  this  attempt  is  opposed  by  theory  as  well  as 
practice,  and  the  wish  is  forestalled,  since  it  is  found  possible  by  means  of  the  Glover 
tower,  or  by  utilising  heat  which  would  otherwise  be  lost,  to  obtain  an  acid  containing 
80  per  cent,  of  monohydrate.  In  one  direction  only  does  progress  seem  possible.  The 
chamber  process,  as  now  conducted,  requires  for  the  production  of  sulphuric  acid  a  long 
time  and,  as  a  necessary  consequence,  extensive  space.*  It  does  not  seem  as  if  a 
diminution  of  time  and  space  for  the  formation  of  sulphuric  acid  could  be  effected  by 
any  modifications  of  the  temperature.  The  process  might  probably  be  abridged  if  a  really 
effective  system  for  the  thorough  and  continuous  intermixture  of  the  gases  were  produced, 
so  that  the  alternating  play  of  the  reactions  might  be  effected  at  shorter  intervals.  Still 
more  would  this  process  be  abridged  if  the  dilution  with  nitrogen  could  be  dispensed  with 
by  using  pure  oxygen  in  place  of  atmospheric  air.  Then  a  higher  pressure  would  be 
practicable,  which  would  render  the  reactions  quicker  and  more  intense.  An  easier  con- 
dition would  be  to  occasion  a  frequent  collision  of  the  gases  with  solid  surfaces,  whereby 
the  particles  which  float  as  mist  in  the  atmosphere  of  the  chamber  would  soon  condense 
to  a  fluid  and  settle  to  the  bottom  ;  a  more  rapid  removal  of  the  product  and  the  re- 
action might  favour  the  combination  of  the  other  ingredients,  and  might  even  promote 
the  intermixture  of  the  gases,  f 

Purification  of  Chamber  Acid.  —  The  sulphuric  acid  let  off  from  the  great  chamber 
has  an  average  sp.  gr.  of  1-52  =  104°  Tw.  or  50°  B.  This  acid  may  be  either  used  at 
once  for  opening  up  mineral  phosphates  in  manure  works,  in  the  manufacture  of 
ammonium  sulphate,  the  manufacture  of  copperas,  &c.,  or  if  it  has  to  be  carried  away 
it  can  be  evaporated  down  to  the  highest  grade  of  concentration,  1-84  sp.  gr.  =  168° 
Tw.  or  66°  B. 

Before  chamber  acid  is  thus  concentrated,  certain  impurities  have  to  be  withdrawn. 
These  accidental  impurities  are,  in  addition  to  traces  of  lead,  copper,  iron,  lime, 
alumina,  and  sometimes  selenium  and  thallium,  oxides  of  nitrogen  and  arsenic.  Nitrous 
acid  may  be  removed  from  sulphurous  acid  by  means  of  oxalic  acid,  which  is  decom- 
posed into  carbon  dioxide  and  monoxide  :  N203  +  3CO  =  3C02  +  2N. 

The  proportion  of  arsenic  in  sulphuric  acid  prepared  from  Sicilian  sulphur  is  generally 
slight,  but  in  that  from  pyrites  and  blende  it  is  more  considerable.  For  its  removal 
there  is  used  in  many  works  sulphuretted  hydrogen  gas,  which  is  prepared  either  from 
iron  sulphide  and  dilute  sulphuric  acid  (the  residual  lye  being  converted  into  copperas), 
or  according  to  Binding's  proposal,  by  the  action  of  generator  gases  upon  pyrites  at  an 
elevated  temperature.  According  to  Hunt's  process,  sulphuretted  hydrogen  gas  is  caused 
to  pass  into  vessels  containing  quartz  stones,  over  which  the  arsenical  acid  is  allowedto  flow. 
The  arsenic  is  thus  thrown  down  as  arsenic  sulphide,  and  is  separated  from  the  sulphuric 
acid  by  means  of  a  sand  filter.  At  Oker,  the  acid  to  be  purified  is  let  flow  into  small 
precipitating  pans  and  diluted  down  to  88°  Tw.  (sp.  gr.  1-45).  The  pan  is  covered 
with  a  lead  lid  with  a  hydraulic  joint,  and  the  acid  is  heated  to  75°,  when  sulphuretted 
hydrogen  is  introduced  until  the  acid  appears  milky  from  the  liberated  sulphur  The 
.acid  is  then  clarified  by  standing  for  six  hours,  and  is  then  passed  through  a  small  filter 
consisting  of  four  double-bottomed  sieves,  between  which  are  layers  of  asbestos  It  is 
received  in  a  cistern  and  kept  for  concentration.  In  the  works  at  Chessy,  near  Lyons 
barium  sulphide  is  used  for  removing  arsenic  from  chamber  acid,  to  which  it  is  added 
ie  proportion  of  o-2  to  0-3  per  cent.  Although  a  small  quantity  of  acid  is  thus  lost 
by  combining  with  the  barium  to  form  sulphate,  this  process  may  be  much  recommended, 
ulphuretted  hydrogen  thus  evolved  from  the  barium  sulphide  is  extremely  effective. 

*  °hamber  r°°m  Provided  cannot  well  be  less  than  20  cubic  feet  per  Ib.  of 


t  It  is  scarcely  necessary  to  say  that  of  the  many  proposals  for  dispensing  with  the  lead- 
chambers  none  have  proved  successful. 


SULPHURIC  ACID. 


275 


Sodium  and  barium  thiosulphates  have  also  been  proposed  for  removing  arsenious  acid 
from  the  chamber  acid.  The  precipitated  arsenic  sulphide  is  worked  up  as  yellow 
arsenical  glass. 

As  arsenic  is  almost  exclusively  present  in  sulphuric  acid  in  the  state  of  arsenious 
acid,  it  may  be  removed  by  the  introduction  of  hydrochloric  acid.  There  is  formed 
arsenious  chloride  (AsCl3),  which  boils  at  a  temperature  of  134°,  and  can  thus  be  easily 
removed  from  sulphuric  acid,  as  the  latter  does  not  boil  below  325°-33o°.  If  thf 
arsenic  occurs  as  arsenic  acid,  it  must  be  previously  reduced  to  the  arsenious  state. 
This  is  effected,  according  to  Kupf  erschliiger  by  means  of  a  current  of  sulphurous  acid  ; 
or  according  to  Buchner  by  heating  the  chamber  acid  with  a  little  charcoal,  when 
sulphurous  acid  is  also  formed.  The  arsenious  acid  when  formed  is  then  removed,  either 
by  means  of  sulphuretted  hydrogen,  or  of  hydrochloric  acid.  The  lead,  indium,  and 
thallium  compounds  present  are  removed  by  means  of  sulphuretted  hydrogen  as 
insoluble  sulphides.  Iron  is  found  in  the  form  of  ferric  sulphate  in  acid  prepared  from 
pyrites,  especially  in  such  as  has  been  concentrated  in  the  Glover  tower. 

Concentration  of  Sulphuric  Acid. — When  chamber  acid  is  heated  it  begins  to  boil 
.at  I30°-i35°,  but  the  boiling-point  continually  rises  until  it  reaches  338°.  This  last 
.acid  is  the  quality  which  is  always  obtained  on  the  concentration  of  chamber  acid.  It 
contains  98  per  cent.  H,S04,  and  on  evaporation  at  the  ordinary  atmospheric  pressure  it- 
.gives  off  no  more  water. 

Chamber  acid  is  concentrated  by  heating  in  open  lead  pans  up  to  140°- 146°  Tw.  (  = 
170  sp.  gr.),  then  in  vessels 
of  platinum  or  glass  up  to  168° 
'Tw.  (  =  66°  B.  or  1*84  sp.  gr.). 

Concentration  in  Leaden 
Pans. — Chamber  acid  does  not 
begin  to  attack  lead  vessels 
until  the  concentration  exceeds 
148°  Tw.,  so  tha-t  it  may  safely 
be  pushed  up  to  140°- 146°  Tw. 
in  leaden  pans.  According  to 
the  experiments  of  Mallard, 
sulphuric  acid  at  140°  to  160° 
Tw.,  if  boiling,  attacks  lead,  with  the  formation  of  sulphurous  acid,  lead  sulphate, 
.and  sulphur  (S02  +  2Pb  =  S  +  2PbO).  The  lead  pans  are  generally,  though  not  univer- 
sally, heated  from  below.  A  pan  of  this  kind  is  shown  in  Fig.  266.  As  a  rule  several 
pans  are  arranged  on  steps,  each  successive  pan,  40  to  50  centimetres  in  depth,  being  fixed 
from  3  to  7  centimetres  lower  than  the  previous  one.  Above  the  wall  which  separates 
every  two  pans,  small  syphons  are  suspended,  the  limbs  of  which  stand  in  small 
cylindrical  vessels.  The  syphons  are  always  kept  full.  If  they  are  immersed  in  the 
liquid  over  the  partition  wall,  the  acid  runs  from  the  one  pan  into  the  next  lower  one. 
The  strength  gradually  increases  in  the  pan. 

The  plates  of  lead,  which  are  i|  centimetre  in  thickness,  rest  upon  iron  plates. 
From  the  last  lead  pan  the  sulphuric  acid  passes  at  once  into  the  concentrating 
vessels  of  platinum  or  glass,  in  order  there  to  be  brought  to  168°  Tw. 

In  the  pans  of  the  second  kind,  the  products  of  combustion  sweep  over  the  acid, 
which  is  contained  in  a  lead  pan  in  the  side  of  the  hearth  of  a  reverberatory.  The 
blackening  of  the  acid  thus  occasioned  is  not  objectionable  if  the  acid  is  to  be  used  in 
the  alkali  manufacture.  At  the  Rhenania  works,  near  Aachen,  there  was  formerly 
used  for  concentrating  the  chamber  acid  a  reverberatory,  with  a  lead  pan,  1-85  metre 
long,  1*25  metre  wide,  and  o-26  metre  deep,  and  overhung  for  15  centimetres  by  the 
fire  bridge  of  masonry.  The  chamber  acid  flows  laterally  into  the  pan  at  the  height 


2?6  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

which  is  to  be  its  level.  At  the  bottom  is  a  leaden  syphon  to  draw  off  the  concentrated 
acid.  The  acid,  rendered  stronger  by  the  loss  of  water  from  its  surface,  sinks  to  the 
bottom  and  flows  off  through  the  syphon.  The  impurities  introduced  by  the  fire-gases 
float  upon  the  surface. 

In  order  to  concentrate  sulphuric  acid  with  indirect  steam,  the  evaporation  is  effected 
at  Duisburg  in  wooden  cisterns  lined  with  lead,  and  of  the  length  and  breadth  of 
4  metres.  On  the  bottom  of  each  cistern  lie  two  leaden  worms,  each  45  metres  long, 
0-03  metre  inside  diameter,  and  the  sides  of  0-007  metre  in  thickness,  through  which 
the  steam  flows  whilst  the  cistern  is  filled  with  acid.  In  order  that  the  condensed 
water  may  run  off  easily  from  the  worms  the  bottom  has  the  form  of  a  truncated 
pyramid,  and  the  cistern  is  in  the  middle,  o'6  metre,  and  at  the  sides  0-3  metre  deep. 
Both  ends  of  each  worm  are  connected  with  the  steam  boiler  and  can  be  shut  off  with 
cocks.  The  steam  boiler  lies  rather  lower  than  the  concentrating  cisterns,  which  receive 
their  steam  from  a  pipe  running  off  from  the  dome  of  the  boiler.  The  pipes  which 
convey  away  the  steam  from  the  concentration  cistern  incline  towards  the  steam-space 
of  the  boiler,  so  as  to  permit  a  reflux  of  the  condensed  steam  to  the  boiler.  The  cistern  is 
filled  with  chamber  acid  of  sp.  gr.  1*5,  and  heated  until  it  has  risen  to  17.  The  entire 
contents  of  the  cistern  are  then  transferred  to  a  wooden  tank  lined  with  lead.  In  it 
lies  a  worm  which  the  chamber  acid  must  traverse  on  its  way  to  the  concentration 
cisterns,  which  are  thus  always  fed  with  hot  concentrated  liquid.  The  pressure  of 
steam  in  the  boiler  is  three  atmospheres,  and,  in  an  apparatus  of  the  size  given,  5000 
kilos,  of  acid  of  sp.  gr.  17  are  obtained  in  twenty-four  hours.  The  consumption  of 
coal  is  9  kilos,  per  100  kilos,  of  concentrated  acid.  The  consumption  of  lead  is  2  kilos, 
per  ton  of  sulphuric  acid.  It  is  advisable  to  place  a  screen  of  boards  above  the 
concentration  cistern,  to  protect  the  workmen  in  case  of  the  bursting  of  the  pipes. 
Delplace  makes  the  remark  that  at  Stolberg  the  leaden  steam-pipes  are  attacked  at 
the  point  where  they  plunge  into  the  liquid.*  The  dust  which  in  time  attaches  itself 
to  the  pipes  sucks  up  the  acid  by  capillarity  a  few  centimetres  higher  than  its  level  in 
the  pan ;  this  acid  is  quickly  concentrated  by  the  heat  and  occasions  an  increased 
corrosion  of  the  lead.  The  mischief  is  prevented  by  fixing,  at  the  point  where  the  pipe 
enters  the  end,  a  leaden  bell  of  large  diameter,  opening  upwards.  Concentration  by 
steam  has  been  of  late  more  common ;  no  sulphuric  acid  is  volatilised  on  account  of  the 
low  temperature,  and  the  process  has  the  advantages  of  cleanliness,  small  consumption 
of  fuel,  and  a  decrease  of  labour. 

The  hot  gases  of  the  pyrites  furnaces  are  often  used  for  concentrating  the  chamber 
icid.  To  this  end  leaden  pans  are  fixed  upon  or  behind  the  furnaces,  and  the  sul- 
phurous acid  is  led  from  the  furnaces  into  a  leaden  tower  filled  with  hard  burned  bricks. 
This  arrangement  has  the  defect  that,  when  the  pans  become  leaky,  the  acid  escaping 
ruins  the  furnaces.  Such  accidents,  in  fact,  have  frequently  happened. 

The  concentration  of  the  chamber  acid  by  the  hot  sulphurous  acid  of  the  Glover 
tower  has  been  already  mentioned. 

Completion  of  Concentration. — The  acid  obtained  in  the  lead  pans  of  a  strength  of 
146°  Tw.  suflices  for  most  purposes.  If  a  more  concentrated  acid  is  required 
(168°  Tw.=  1-847  SP-  g1"-)'  ft  *s  transferred  to  vessels  of  glass  or  platinum.  It  may  be 
here  remarked  that  the  Baume  hydrometers  used  in  many  works  are  carelessly  con- 
structed. The  point  to  which  the  instrument  sinks  in  ordinary  (?)  sulphuric  acid  is 
marked  as  66°,  and  the  interval  between  that  point  and  the  point  for  water  (o°)  is 
divided  into  66  parts.  Samples  of  sulphuric  acid  which  marked  67°  on  this  instrument 
had  a  sp.  gr.  of  only  r8o  and  i-Si.f 

*  This  is  a  very  general  phenomenon. 

t  It  must  be  added  that  the  tables  for  Baum^'s  hydrometer,  as  given  in  standard  works,  differ 
seriously.  In  Gmelin's  Handbook  of  Chemistry  (Cav.  Soc.  edition)  46°  B.  is  given  as  equal 


SECT,  in.]  SULPHURIC  ACID.  277 

Concentration  in  glass  vessels  is  very  general.  In  Britain  more  than  70  per  cent, 
of  all  the  sulphuric  acid  is  concentrated  in  glass  vessels,  the  purchase  and  maintenance  of 
which  scarcely  amount  to  half  the  interest  on  the  cost  of  a  platinum  apparatus. 
Formerly  there  were  used  glass  retorts  of  the  ordinary  shape,  fixed  to  the  number 
of  ten  in  sand-baths  in  a  galley  furnace  (Fig.  267).  The  necks  have  elongations 
which  open  into  stoneware  flasks  to  condense  the  escaping  vapours.  In  the  works  of 
€hance  &  Co.,  of  Oldbury,  the  glass  vesr3l,  B  (Fig.  268),  85  centimetres  high  and 

Fig.  267. 

Fig.  268. 


45  centimetres  wide,  holds  136  litres,  and  yields  each  time  87  litres  (=  160  kilos.;  of 
•concentrated  acid.  A  is  the  fire-box,  and  C  the  iron  sand-bath,  which  has  sand  only 
at  its  bottom.  The  gases  escape,  through  /),  into  the  chimney.  A  glass  elbow-tube,  E, 
is  in  connection  with  the  lead  vessel,  F,  in  which  the  distilled  water  is  condensed.  At 
the  end  of  the  process  the  pipes,  E,  are  removed,  and  the  acid  is  drawn  off  with  a  syphon 
without  disturbing  the  vessels.  During  the  work  the  upper  part  of  the  glass  vessels 
is  protected  against  chills  and  currents  of  air  by  covers  of  stoneware  or  of  sheet-iron. 

The  glass  vessels  used  in  the  chemical  works  at  Muehlheim  on  the  Rhine  consist  of  the 
retort  itself  in  the  form  of  an  ovoid  body  of  70-80  centimetres  height  and  40-50  centi- 
metres diameter,  and  a  capital  which  is  like  a  laboratory  retort  without  bottom.  They 
.are  made  of  white,  very  thin  glass,  hold  about  300  kilos,  of  acid,  and  cost  about  38*.  Of 
these  retorts  thirty -two  stand  in  a  row.  Each  is  in  an  iron  vessel  filled  with  sand,  into 
which  the  retort  is  embedded  to  about  10  centimetres  from  its  neck.  Each  retort  has  a 
separate,  dii'ect  fire,  and  is  separated  from  the  others  by  an  iron  screen  15  centimetres 
in  height.  The  escaping  gases  from  each  pass  in  a  common  flue  to  the  chimney.  In 
front  of  the  retorts  there  lies  a  thin  leaden  pipe  for  filling  them,  and  before  each  single 
retort  there  branches  off  from  this  leaden  pipe  a  smaller  tube,  which  can  be  raised  and 
lowered.  When  the  retort  is  to  be  filled  the  lead  tube  is  lowered  into  the  neck  and 
the  acid  flows  in  from  a  leaden  pan  at  a  higher  level,  in  which  the  chamber  acid  has 
been  previously  concentrated.  In  this  manner  thirty-two  retorts  can  be  filled  in  half- 
an-hour.  The  emptying  is  effected  whilst  hot  by  means  of  glass  syphons,  which  are 
"  set "  by  suction  from  an  air-pump.  The  arm  is  left  loose  in  the  neck  of  the  retort. 
To  prevent  glass  from  coming  in  contact  with  glass,  there  are  placed  in  the  neck  three 
or  four  small  lead  discs,  upon  which  the  arm  rests.  The  arm  of  each  retort  enters  a 
common  lead  tube  about  20  centimetres  in  width,  which  lies  along  the  retorts  and  is 

either  to  1-468  or  to  i'456  sp.gr.;  in  Crookes's  Select  Methods  46°  B.  represents  I  '434.  Other 
varying  values  are  to  be  found  in  other  works.  A  further  defect  in  Baume's  scale  is  that  its 
indications  cannot  be  simply  recalculated  into  specific  gravities.  Hence,  it  would  be  well  if 
Continental  and  American  manufacturers  would  abandon  this  instrument. 


278 


CHEMICAL  TECHNOLOGY. 


[SECT.  in.. 


Fig.  269. 


connected  with  the  chimney.  It  carries  off  the  vapours  from  the  evaporation.  As  some 
sulphuric  acid  escapes  along  with  the  water,  the  gases  pass  first  through  some  coolers, 
consisting  of  large  lead  cylinders  tilled  with  coke  and  cooled  by  water.  Here  the  so- 
called  dropping  acid  is  collected.  All  the  retorts  are  in  a  building  protected  from 
draughts,  whilst  the  fires  are  in  an  annex  on  the  outside.  In  front  of  each  retort 
there  is  a  small  glass  window  for  observing  the  process  and  regulating  the  fire  accord- 
ingly. Boiling  begins  in  one  to  two  hours ;  the  entire  process  lasts  eight  to  ten  hours. 

The  evaporation  is  continued  until  the  acid 
becomes  colourless — a  certain  sign  that  it  has 
reached  its  full  strength. 

The  platinum  stills  have  a  capital  either  of 
platinum  or  lead.  The  acid  which  distils  over 
of  sp.  gr.  i -125  to  1-162  is  either  returned  to 
the  lead  pans,  or  concentrated  separately  for 
the  production  of  a  purer  acid,  or  used  as  it 
is.  The  cooling  of  the  acid  concentrated  in 
the  platinum  still  may  be  effected  in  several 
ways,  e.g.,  by  the  use  of  the  Breant  syphon 
(Fig.  269)  of  platinum.  Its  limb,  situate 

outside  the  still,  is  5  metres  long,  and  is  fitted  with  a  copper  tube  15  centimetres 
in  width  and  4  metres  in  length;  it  is  filled  with  cold  water  at  a,  whilst  the  heated 
water  flows  off  at  b.  To  increase  the  surface  of  the  syphon,  its  main  pipe  is  divided 
into  four  narrow  tubes.  The  syphon  is  set  by  closing  the  cock  at  c,  and  then  pouring 
in  sulphuric  acid  at  the  ball  valves  at  d  and  e  to  form  a  tight  hydraulic  joint ;  the' 


Fig.  270. 


Fig.  271. 


Fig.  272. 


\m\sm^ 

cock,  c,  is  opened  and  the  acid  flows  out.  If  it  were  necessary  to  delay  drawing 
off  the  acid  until  cold,  time  would  be  lost  and  the  still  could  not  effect  a  quantity 
of  work  commensurate  with  its  high  price. 

The  arrangement  of  a  platinum  still  with  a  platinum  capital  is  shown  in  Figs.  270, 
271,  272,  and  273.  The  platinum  tube,  d,  connects  the  capital,  S,  with  a  cooling  worm  of 
lead  lying  in  water.  The  S-tube  of  platinum,  i,  with  its  funnel,  has  sometimes  the 
shape  as  in  Fig.  270.  A  cylindrical  leaden  vessel,  g,  is  provided  with  an  exit  tube,  ht_ 


SECT.    III.] 


SULPHURIC   ACID. 


and  the  similar  leaden  vessel,  m,  has  at  its  side  a  slit,  so  that  the  tube,  h,  can  move  in  it  up 
and  down  when  the  cylinder,  g,  is  lifted  up  or  let  down.  A  filled  leaden  syphon  connects 
a-  with  g.  If  the  cylinder,  g,  is  drawn  up  as  high  as  it  is  shown  by  the  dotted  lines  in 
Fig.  271,  the  syphon  ceases  flowing,  but  if  it  is  let  down  the  acid  of  the  pan  flows 
through  the  funnel,  i,  into  the  pan,  A.  Still  more  simple  is  the  arrangement  shown  in 
Fig.  272.  A  syphon,  m,  dips  in  the  pan,  P,  and  on  the  other  side  into  the  beaked  vessel, 
n.  In  proportion  as  the  small  cylinder,  d,  suspended  to  the  chain  is  raised  or  lowered, 
the  outflow  of  the  acid  is  regulated  or  stopped  entirely.  Fig.  273  shows  the  apparatus 

Fig.  273- 


n 


in  section  at  right  angles  to  Fig.  271.  In  the  platinum  pan,  A,  there  is  a  perforated 
tube,  o,  of  platinum,  in  which  is  a  float  of  glass  showing  the  level  of  the  acid  in  the  pan. 
The  long  limb  of  the  platinum  syphon,  d,  lies  in  a  wide  iron  tube  supplied  with  cold 
water.  The  syphon,  generally  of  Breant's  design,  ends  in  a  platinum  cock,  i.  The  pan 
stands  on  a  disc  of  fire-clay  with  perforators,  into  which  the  flame  penetrates  and  plays 
round  the  retort.  The  specific  gravity  of  the  acid  which  drops  off  through  the  pipe  of 
the  capital,  d  (Fig.  271),  shows  the  progress  of  the  work.  In  the  Oker  Works  on  the 
Harz,  a  strength  of  20°  B.  here  is  understood  to  indicate  that  the  acid  in  the  platinum 
pan  has  become  66°  B.  =  168°  Tw.,  and  is  fit  to  be  drawn  off.  It  then  flows  for  refrigera- 
tion through  the  cooling  apparatus,  d  and  h,  into  the  leaden  vessel,  k,  which  is 
surrounded  with  cold  water,  from  n.  The  acid  when  sufficiently  cooled  is  run  into  the 
well-known  carboys,  holding  each  about  100  kilos.,  which  are  placed  in  wicker  baskets 
packed  with  straw,  and  closed  by  a  clay  stopper. 

Latterly,  platinum  apparatus  with  a  leaden  capital  are  coming  into  use.  The 
apparatus  of  Johnson,  Matthey  &  Co.  (Fig.  274)  consists  of  a  platinum  body, 
0*75  metre  wide  and  0^50  metre  in  height ;  its  upper  margin,  b,  is  bent  over  for 
5  centimetres.  This  margin  bending  outwards  forms,  with  channel  of  platinum  resting 
on  the  wall  built  round  the  platinum  body,  a  hydraulic  joint,  which  is  placed  for  the 
protection  of  the  platinum  in  a  channel  of  iron  or  lead.  In  this  channel,  whieh  is  about 
15  centimetres  wide,  there  rests  the  conical  capital  of  strong  lead,  d,  which  covers  the 
platinum  vessel  as  with  a  lid,  and  on  the  upper  part  of  which  is  soldered  a  low  cap,  e, 
with  a  strongly  sloping  tube,  both  of  lead.  The  syphon  for  drawing  off  the  concen- 
trated acid  is  attached  to  the  side  of  the  body  at/,  the  level  of  the  acid  provided  for, 
so  that  when  the  acid  reaches  this  height  it  runs  off  spontaneously.  To  the  leaden  cap 
are  soldered  the  inflow  pipe,  g,  for  the  acid  to  be  concentrated,  and  the  arrangement, 
h,  for  the  gauging  glass.  The  pipe  sloping  down  from  the  cap  is  connected  with 
the  cooling  worm,  i,  in  order  to  carry  back  to  the  cooler  any  vapours  which  might 


280 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


escape.  The  syphon  for  drawing  off  the  concentrated  acid  projects  out  of  k,  and  is  con- 
nected with  the  cooling  tube,  m,  i^  metre  in  length,  by  means  of  the  ball- joint,  I, 
Hence  the  acid  finally  flows  through  a  very  efficient  pot-cooler,  n,  which  makes  it 
possible  to  run  the  acid  at  once  into  carboys.  To  keep  the  leaden  cap  cool  and  prevent 
it  from  sinking  in  on  account  of  the  great  heat  of  the  boiling  acid,  it  is  surrounded  with 
a  cylindrical  screen,  by  which  the  cap  itself  becomes  a  kind  of  evaporating  pan,  which, 

Fig.  274. 


Fig.  275. 


when  kept  constantly  full  of  chamber  acid,  effects  the  double  purpose  of  cooling  and 
concentration. 

The  platinum-lead  concentrator  of  Faure  and  Kessler  aims  at  high  efficiency  in  the 
concentration  of  the  acid,  combined  with  a  great  economy  of  platinum.  It  consists  of 
a  very  large,  but  shallow,  platinum  pan,  or  of  several  flat  pans  connected  together,  and 
heated  from  below  by  a  direct  fire.  The  depth  of  the  acid  is  small.  Over  the  platinum 
pan  is  a  covering  of  lead,  the  outside  of  which  is  kept  cool  by  a  stream  of  water.  On 
the  inside  the  acid-vapours  ascending  from  the  platinum  pans  are  liquefied,  and  led 

outwards  by  a  channel.  The  sulphuric  acid 
flows  in  a  continuous  stream  from  the  back 
to  the  front,  and  is  drawn  off  in  the  ordinary 
manner  by  a  platinum  syphon  as  acid  of 
1 68°  Tw. 

As  far  back  as  1844,  Kuhlmann  recom- 
mended the  use  of   a   reduced   atmospheric 
pressure.     Latterly  this  procedure  has  been 
repeatedly  applied.    In  the  arrangement  pro- 
posed   by   the    International    Vacuum    Ice- 
Machine   Company   of   Berlin,    the   pan,    S 
(Fig.  275),  made  of  hard  lead,  is  surrounded 
with  a  bad  conductor  of  heat,  and  fitted  with 
a  gauge-glass,  C.     Into  the   steam- vessel,  E, 
made  of  iron  or  copper  plates,  there  are  in- 
troduced the  leaden  worms,  M,  Mv  traversed  by  the  acid,  and  resting  on  the  inner 
supports,  N,  JV,.     The  steam  for  heating  enters  at  a,  whilst  the  steam- water  flows  off  at 
d.     The  acid  to  be  concentrated  passes  through  the  exchange  apparatus,  F,  through  the 
worm,  T  (surrounded  by  steam),  of  the  heater,  V,  and  enters  the  pan  at  c.     The  acid, 
which  has  become  colder  and   heavier  by  the  removal  of  the  watery  vapours,  goes  in 
the  direction  of  the  arrows,  b,  to  the  heater,  E,  placed  lower  than  the  pan.     Here  it  is 


SECT,  m.j  SULPHURIC  ACID.  281 

heated  anew,  and  makes  a  continual  circuit,  as  in  a  common  water-heating  appara- 
tus. The  watery  vapour  is  drawn  off  at  D,  and  the  concentrated  acid  is  let  off 
at  J. 

The  ordinary  sulphur  acid  of  commerce  contains  93  to  96  per  cent,  of  the  so-called 
monohydrate,  H2SO4.  Exceptionally,  a  stronger  acid  of  97  or,  at  the  utmost,  98  per 
cent,  is  obtained  by  further  evaporation  in  glass  or  platinum  vessels ;  stronger  acid 
cannot  be  obtained  in  this  manner,  as  the  monohydrate  is  dissociated  even  at  a  mode- 
rate temperature,  leaving  acid  of  98  to  98*5  per  cent.  G.  Lunge  has  observed  that,  by 
refrigerating  98  per  cent,  acid  at  a  little  below  o°,  monohydrate  can  be  made  to  crys- 
tallise out  on  an  industrial  scale,  but  that  the  same  result  can  be  obtained  with  acids 
of  97  or  even  96  per  cent,  by  cooling  down  to  -  10°,  if  the  occurrence  of  superfusion  is 
obviated  by  dropping  in  a  few  crystals  of  the  monohydrate.  A  small  quantity  of 
crystals  of  monohydrate  are  first  prepared  by  freezing  at  — 10°  a  98  per  cent,  acid 
(obtained  by  firing  ordinary  or  fuming  acid).  A  sulphuric  acid  at  96  to  97  per  cent, 
is  next  cooled  down  to  at  least  o°,  then  a  few  crystals  of  the  monohydrate  are  thrown 
in,  and  the  whole  is  further  cooled  with  stirring  until  the  formation  of  crystals  is  com- 
pleted. The  mother  liquor  is  then  removed  by  draining,  pressing,  &c.,  not  letting  the 
temperature  rise  above  o°. 

Of  the  many  modern  proposals  for  manufacturing  sulphuric  acid  in  novel  manners 
the  following  may  be  mentioned. 

Hahner  oxidises  sulphurous  acid  by  chlorine  in  presence  of  watery  vapour  : 
S02  +  2H2O  +  C12  =  H2S04  +  2HC1. 

The  chlorine  is  obtained  from  the  hydrochloric  acid  produced  in  the  alkali  manu- 
facture (Deacon's  process).  If  the  sulphuric  acid  is  to  serve  for  the  decomposition  of 
common  salt  it  does  not  need  to  be  purified  from  hydrochloric  acid.  Gypsum, 
CaS04.2H2O.  has  been  repeatedly  considered  as  a  source  of  sulphuric  acid,  and  various 
methods  have  been  proposed  to  obtain  sulphuric  acid  from  gypsum  and  similar  sul- 
phates, without  any  such  proposal  having  been  carried  into  successful  execution. 
Tilghman  places  pieces  of  gypsum  in  an  upright  earthen  cylinder  lined  with  magnesite. 
The  charge  is  then  heated  to  full  redness,  and  the  gaseous  products  of  decomposition, 
O,  S02,  and  H2S04,  are  conveyed  through  the  bottom  and  the  top  to  the  lead  chambers. 
Quicklime  is  said  to  be  left  in  the  cylinder.  Epsomite  may  be  treated  in  the  same 
manner. 

Seckendorff  introduced  powdered  gypsum  and  lead  chloride  into  stone  tanks  along 
with  a  large  quantity  of  water  heated  to  5o°-6o°.  The  mixture  must  be  well  stirred. 
Both  salts  are  rapidly  decomposed  : 

CaS04  +  PbCl,  =  CaCl,  +  PbS04. 

The  calcium  chloride  remains  in  solution  whilst  the  lead  sulphate  forms  a  precipitate, 
•which  is  filtered  off  and  treated  with  hydrochloric  acid  in  excess  : 
PbS04  +  zHCl  =  PbCl,  +  H2S04. 

The  mixture  is  stirred  and  heated  to  60°,  when  lead  chloride  collects  at  the  bottom, 
and  the  sulphuric  acid  remains  in  solution,  and  is  concentrated  in  the  usual  manner. 
The  lead  chloride  serves  for  the  decomposition  of  fresh  quantities  of  calcium  sulphate. 
If  hydrochloric  acid  is  passed  over  calcium  sulphate  at  a  red  heat,  sulphuric  acid  escapes 
and  calcium  chloride  remains  : 

CaS04  +  2HC1  =  H2SO4  +  CaCl2. 

According  to  Scheurer  Kestner,  if  2  parts  calcium  sulphate  are  heated  to  bright  red- 
ness with  i  part  ferric  oxide,  all  the  sulphuric  acid  is  expelled.  Sulphuric  anhydride 
escapes  first  and  afterwards  sulphurous  acid  and  oxygen.  The  behaviour  of  magnesium 
sulphate  is  similar. 


282 


CHEMICAL  TECHNOLOGY. 


[SECT,  iii. 


PROPERTIES   OP   SULPHURIC  ACID. 

The  most  highly  concentrated  sulphuric  acid,  of  the  formula  H2S04,  has  the  sp.  gr. 
1-857  (J.  Kolb),  1-854  (Marignac),  1-8384  (Lunge  and  Naef).  When  pure  it  is  a 
perfectly  colourless  liquid,  which,  however,  is  commonly  coloured  yellowish  or  brownish, 
owing  to  the  accidental  presence  of  particles  of  organic  dust.  It  is  thick  and  oily, 
destroys  many  organic  bodies  with  liberation  of  carbon,  does  not  fume  in  the  air,  and  is 
so  hygroscopic  that  it  gradually  absorbs  15  times  its  own  volume  of  water.  If  mixed 
with  water,  great  quantities  of  heat  are  liberated.  Of  all  the  volatile  acids  it  has  the 
greatest  affinity  for  bases,  and,  on  heating,  it  expels  all  other  volatile  acids  from  their 
salts.  But  at  a  red  heat  sulphuric  acid  is  expelled  from  its  salts  (partly  decomposed 
into  sulphur  dioxide,  oxygen,  and  water)  by  silicic,  boric,  or  phosphoric  acid.  The 
boiling-point  of  the  most  concentrated  acid  is  338°. 


Per  cent.  H2S04. 

Specific  Gravity. 

Specific  Gravity. 

Baum6. 

90 

1-8185 

I  '8202 

65-1° 

91 

1-8241 

1-8254 

65'4 

92 

I  '8294 

I  '8306 

65-6 

93 

I  ^339 

1-8346 

65-8 

94 

I-8372 

I-8374 

65-9 

95 

I  '8390 

I  -8397 

66-0 

96 

I  '8406 

97 

1-8410 

9775 

— 

1-8468 

66-2 

98 

1-8412 

99 

I  '8403 

lOO'OO 

1-8384 

Specific  Gravities  of  Sulphuric  Acid,  at  15°  (KoW). 


Specific 
Gravity. 

Degrees 

Baume. 

Degrees 
Twaddell. 

too  Parts  by  Weight  correspond 
to  per  Cents. 

i  Litre  contains  Kilos,  of 
Pure  Acid. 

S03. 

H2S04. 

S03. 

H2SO4. 

•OOO 

O 



07 

0'9 

0-007 

0-009 

'014 

2 

2'8 

2'3 

2'8 

0-023 

0-028 

•029 

4 

5'8 

3  '9 

4'8 

0-040 

0-049 

•045 

6 

9-0 

5-6 

6-8 

0-059 

0-071 

•060 

8 

I2'0 

7-2 

8-8 

0-076 

0-093 

•075 

10 

15-0 

8-8 

10-8 

0-095 

0-116 

•091 

12 

18-2 

io'6 

13-0 

0-116 

0-142 

•108 

14 

21  '6 

12-4 

15-2 

0-137 

0-168 

•125 

16 

25  -o 

14-1 

I7-3 

0-159 

0-195 

•142 

18 

28-4 

16-0 

19-6 

0-183 

0-224 

•162 

20 

32-4 

18-0 

22  '2 

0-209 

0-258 

•180 

22 

36-0 

2O  '0 

24-5 

0*236 

0-289 

•200 

24 

40-0 

22'I 

27-1 

0-265 

0-325 

•220 

26 

44  -o 

24-2 

29  '6 

0-295 

0-361 

•241 

28 

48-2 

26-3 

32-2 

0-326 

0-400 

•263 

3° 

52-6 

28-3 

347 

o-357 

0-438 

•285 

32 

57'0 

30-5 

37'4 

0-392 

0-481 

•308 

34 

61-6 

32-8 

40-2 

0-429 

0-526 

•332 

36 

66-4 

35'I 

43  '0 

0-468 

0-573 

'357 

38 

7i-4 

37'2 

45'5 

0-505 

0-617 

•383 

40 

76-6 

39'5 

48-3 

0-546 

0-668 

•410 

42 

82-0 

41-8 

51-2 

0-589 

0-722 

•438 
1-468 

44 
46 

87-6 
93  '6 

44'I 
46-4 

54-o 
56-9 

0-634 
0-681 

0777 
0-835 

Kohlrausch  has  shown  that  sulphuric  acid  has  its  maximum  density  below  its 
highest  concentration. 

Applications. — The  applications  of  sulphuric  acid  are  extremely  extensive  and  mani- 
fold ;  e.g.,  in  the  preparation  of  many  acids  (nitric,  hydrochloric,  sulphurous,  carbonic, 


SECT,  in.]  POTASSIUM   SALTS.  283 

tartaric,  citric,  stearic,  palmitic,  and  oleic),  for  producing  acid  calcium  phosphate  as  a 
manure  for  the  production  of  chlorine,  of  stearine  candles  (decomposition  of  lime  soaps), 
of  phosphorus  (by  decomposing  bone-earth),  for  making  salt-cake  in  the  alkali-manu- 
facture, the  production  of  potassium  sulphate  (from  the  potassium  chloride  or 
carnallite),  of  ammonium  sulphate,  alum,  iron  and  copper  vitriols,  baryta  white, 
hydrogen  gas,  nitro-glycerine,  gun-cotton,  picric  acid,  in  separating  gold  from  silver, 
de-silvering  black -coppers,  for  refining  rape  oil,  petroleum,  and  paraffine,  obtain- 
ing garancine  or  other  madder  products,  for  producing  the  sulphonic  acids  of  the 
tar-colours,  for  manufacturing  glucose,  parchment  paper,  shoe-blacking,  as  a 
disinfectant,  for  desiccating  confined  air  (e.g.,  for  glue),  for  drying  the  chlorine  obtained 
in  the  Deacon  process,  for  cleaning  sheet-iron  to  be  tinned,  &c. 

POTASSIUM  SALTS. 

Potassium  is  found  widely  diffused  both  in  the  mineral  kingdom  and  in  organic 
nature.  The  sources  of  potash  available  for  technical  purposes  are  at  present  the 
following  : — 

/  i.  Natural  salts,  carnallite,  sylvine,  kainite,  and  schoenite. 
A.  Inorganic    I    2.  Felspar,  and  similar  rocks. 

sources.       j   3.  Sea-water,  and  the  mother  liquor  of  salt-works. 
\  4.  Native  saltpetre. 
,  5.  Ash  of  plants. 

B.  Organic       6.  Residue  from  beetroot  treacle, 
sources.      "|   7.  Seaweeds ;  a  bye-product  of  the  iodine  manufacture. 
\  8.  The  suint  from  raw  wool. 

Of  these  sources  the  most  important  at  present  are  the  deposits  of  alkaline  salts. 
They  are  supposed  to  have  been  formed  by  the  gradual  drying  up  of  salt  lakes  or  arms 
of  the  sea.  Similar  phenomena  are  at  present  gradually  taking  place  in  Central  Asia. 
The  more  soluble  salts,  those  of  potassium  and  magnesium,  would  remain  in  solution 
longer  than  sodium  chloride,  and  would  thus  be  in  danger  of  being  swept  away  by 
intermediate  geological  changes,  inundations,  &c.  Hence  of  the  many  and  vast  saline 
beds  in  the  earth,  many  are  totally  free  from  potassium  salts,  which  in  North  Germany 
have  been  accidentally  preserved.  At  Kalucz  in  Hungary,  and  on  the  southern  slopes 
of  the  Himalaya,  similar  deposits  occur. 

Potassa  Salts  from  the  Stassfurt  Salt  Minerals. — I.  The  very  abundant  salt-rocks 
near  Stassfurt  in  Prussia,  [and  Kalucz  in  Hungary,  chiefly  yield  carnallite,  sylvine 
(C1K),  and  kainite,  a  compound  of  sulphate  of  potassa  and  magnesia  with  chloride  of 
magnesium.  Carnallite,  so  named  in  honour  of  Carnall,  a  Prussian  mining  engineer, 
consists,  in  100  parts,  leaving  the  bromide  out  of  the  question,  of — 

Potassium  chloride  .  .  .  .27 
Magnesium  chloride  .  .  .  •  34 
Water 39 

too 

fCl 
Formula— K012,Mgj  T> "  +  6H20.     This  salt  is  applied  in  the  manufacture  of — 

a.  Potassium  chloride. 

|3.  „        sulphate. 

y.          „        carbonate. 

a.  Preparation  of  Potassium  Chloride. —  According  to  the  process  originally 
patented  (1861)  by  Mr.  A.  Frank,  the  abraum  salts  are  ignited  in  a  reverberatory 
furnace,  with  or  without  the  aid  of  a  current  of  steam,  and  next  lixiviated  with  water, 
the  resulting  liquor  yielding  chloride  of  potassium.  The  rationale  of  this  process  is : — 
I.  That  the  carnallite  of  the  abrauin  salts  is  separated  by  the  action  of  the  water  into 


284  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

chloride  of  potassium  and  chloride  of  magnesium.  2.  The  latter  salt  on  being  ignited 
in  a  current  of  steam  is  decomposed  into  hydrochloric  acid,  which  escapes,  and  magnesia, 
which  is  practically  insoluble  in  water,  and  which  consequently  remains.  This 
process  is  not  found  to  answer  well  on  the  large  scale,  because  the  abraum  salts  contain 
other  chlorides,  the  chloride  of  sodium  and  tachydrite,  by  the  presence  of  which  the 
decomposition  of  the  carnallite  is  hindered.  Dr.  Griineberg,  therefore,  suggested  that 
the  abraum  salts  should  be  first  mechanically  purified,  that  is  to  say,  the  different  com- 
ponents of  the  abraum  salts  should  be  separated  from  each  other  according  to  their 
varying  specific  gravity,  which  for — 

Carnallite  is  —  1*618 

Chloride  of  sodium  is  =  2-200 
Kieserite  is  =  2*517 

The  abraum  salt  having  been  ground  to  a  coarse  powder  is  passed  through  sieves, 
And  treated  as  minerals  are  in  metallurgical  processes,  with  the  difference  that,  instead 
of  water,  which  of  course  would  dissolve  the  salts,  a  thoroughly  concentrated  solution  of 
chloride  of  magnesium  is  applied,  this  solution  not  acting  upon  the  salts,  and  being, 
moreover,  obtained  as  a  bye-product  in  enormously  large  quantities.  The  above- 
mentioned  salts  settle  in  layers  according  to  their  densities,  the  carnallite  forming  the 
upper,  and  the  kieserite  the  lowest  layer.  The  carnallite  is  at  once  applied  to  the  pre- 
paration of  chloride  of  potassium  ;  the  middle  layer  of  common  salt  is  so  free  from  other 
foreign  salts  as  to  be  fit  for  domestic  use  ;  the  kieserite,  after  having  been  washed  with 
cold  water  to  remove  any  adhering  chloride  of  sodium,  is  applied  to  the  manufacture  of 
sulphate  of  potassa,  to  be  presently  described.  However,  the  greater  number  of  manu- 
facturers at  Stassfurt  prefer  another  plan,  applying  the  five  following  operations  to 
the  abraum  salts  as  delivered  from  the  salt  quarries  : — i.  Lixiviation  of  the  carnallite 
with  a  limited  quantity  of  hot  water,  sufficient  to  dissolve  the  chlorides  of  potassium 
and  magnesium,  leaving  the  bulk  of  the  common  salt  and  magnesium  sulphate. 
2.  Crystallising  the  chloride  of  potassium  by  artificially  freezing.  3.  Evaporating  and 
cooling  the  mother  liquor  to  produce  a  second  yield  of  crystallised  chloride  of  potassium. 
4.  Again  evaporating  and  cooling  the  mother  liquor,  which  yields  the  double  salt  of 
the  chlorides  of  potassium  and  magnesium,  or  artificial  carnallite,  which  is  next  treated 
in  the  same  manner  as  the  native  salt.  5.  Washing,  drying,  and  packing  the  chloride 
of  potassium. 

According  to  Dupre,  ejection  apparatus  (Fig.  276)  are  used,  so  arranged  that  their 

suction  openings,  a,  are  in  connection  with  the 

Fig.  276.  space  beneath  the  sieve  flooring,  s,  whilst  the 

ejection  openings  are  connected  with  the  space 
above  this  flooring.  At  the  same  time,  the 
direction  of  the  apparatus  is  such  as  to  produce 
an  intense  circiilation  of  the  liquid  and  the  saline 
particles. 

The  hot  solution  obtained,  of  sp.  gr.  1-32,  is 
allowed  to  stand  in  separate  vessels  to  deposit 
the  suspended  particles  (of  kieserite  and  clay), 
and  then  it  is  let  flow  into  iron  crystallising 

tanks,  in  which,  after  cooling  for  two  to  three  days,  a  mixture  of  potassium  and  sodium 
chlorides  crystallises  out.  In  some  works  the  crude  saline  solution  is  diluted  with 
water,  whereby  the  separation  of  sodium  chloride  is  diminished  and  a  crystallisation 
of  almost  pure  potassium  chloride  is  effected.  In  order  to  obtain  the  potassium  chloride 
still  remaining  in  the  mother  liquor,  the  latter  is  evaporated  down  to  such  a  concentra- 
tion that  the  potassium  chloride  separates  almost  entirely  out  in  the  form  of  carnallite, 
and  only  i  per  cent,  is  left  in  solution.  The  artificial  carnallite  is  dissolved  in  hot 


SECT,  m.]  POTASSIUM   SALTS.  285 

water,  and,  as  it  cools,  a  second  crystallisation  of  potassium  chloride  is  obtained,  The 
potassium  chloride  obtained  from  both  crystallisations  is  washed  with  water  at  common 
temperatures  to  remove  magnesium  chloride,  and  in  part  sodium  chloride ;  it  is  dried  in 
a  calcining  furnace  or  on  kilns  heated  by  steam.  The  mother  liquor  from  the  second 
crystallisation,  and  the  washings  containing  potassium,  sodium,  and  magnesium  chlorides, 
are  used  for  dissolving  the  crude  salt. 

The  pans  for  evaporating  the  mother  liquor  in  the  manufacture  of  potassium 
chloride  have  three  flame  tubes,  the  middle  one,  a  (Fig.  277),  having  double  the  section 
of  the  two  side  tubes,  b.  The  flame  strikes  first  backwards 
through  the  middle  tube  and  then  forwards  through  the  side 
tubes.  Hitherto  the  flame  tubes  were  rivetted  to  both  cheeks 
of  the  pan,  which  easily  occasioned  a  strain  and  a  loosening  of 
the  joints.  For  the  ready  removal  of  the  sodium  chloride, 
which  separates  out  on  the  evaporation  of  the  mother  liquor, 
the  bottom  of  the  pan  slopes  towards  the  middle,  d,  and  the 
lowest  point  is  provided  with  a  helix,  s.  By  its  rotation  the 
salt  is  removed  which  has  been  deposited  in  the  lowest  part  of 
the  pan. 

Of  the  potassium  chloride  present  in  the  crude  salt,  75  to 

85  per  cent,  is  obtained ;  the  rest  is  lost  in  the  various  residues.  The  proportion  of 
potassium  chloride  in  the  muddy  settlings  is  sometimes  considerable,  so  that  the  salt 
calcined  in  some  works  and  sold  for  manure  may  contain  18  to  24  per  cent,  potassium 
chloride.  Supposing  the  loss  in  the  manufacture  to  be  20  per  cent.,  then  625  kilos, 
crude  salt  at  16  percent,  are  needed  for  the  production  of  100  kilos,  potassium  chloride 
at  80  per  cent.  For  the  daily  manipulation  of  50  tons  raw  gait  a  space  of  350  cubic- 
metres  is  needed  for  crystallising,  or  for  a  daily  turn-over  of  3500  tons  a  total  of 
24,500  cubic  metres. 

Of  the  potassium  chloride  80  per  cent,  is  used  in  the  manufacture  of  potash  saltpetre, 
whilst  for  the  preparation  of  potash  a  pure  product,  as  free  as  possible  from  sodium 
chloride,  is  needed. 

As  bye-products,  kieserite  and  sodium  sulphate  are  obtained  from  the  residues. 
The  former  is  produced  in  the  simplest  manner,  by  dissolving  the  sodium  chloride 
found,  when  the  sparingly  soluble  kieserite  is  split  up  and  deposits  as  a  fine  mud ; 
this  takes  up  water  and  hardens  in  a  few  hours,  and  is  sold  in  blocks  weighing 
25  kilos.  From  a  part  of  the  kieserite  pure  magnesium  sulphate  is  obtained  by 
solution  and  crystallisation. 

The  manufacture  of  Glauber's  salt  (sodium  sulphate)  is  carried  on  only  in  winter. 
It  depends  on  mutual  decomposition  of  sodium  chloride  and  magnesium  sulphate  in 
aqueous  solutions  at  temperatures  below  o°.  To  this  end,  the  total  residue  is  dissolved 
in  water ;  the  concentrated  lye  obtained  after  it  has  become  clear  is  exposed  in  flat 
exposed  wooden  troughs  to  the  cold  of  winter.  The  crystallisation  is  often  effected  in 
a  single  night.  In  this  manner  about  10,000  tons  sulphate  are  produced  yearly. 
After  the  introduction  of  freezing  machines  the  output  will  be  decidedly  greater. 

The  conversion  of  potassium  chloride  into  potassium  sulphate  by  Glauber's  salt, 
which  has  been  repeatedly  tried,  has  not  been  found  practicable  on  the  large  scale,  as 
the  two  sulphates  have  a  great  tendency  to  form  a  double  salt.  At  present  large 
quantities  of  potassium  sulphate  are  prepared  by  means  of  sulphuric  acid  in  a  manner 
quite  analogous  to  the  Leblanc  soda  process  and  with  the  same  apparatus  and  furnaces. 
Griineberg  and  Schmidtborn  allowed  a  hot  solution  of  potassium  chloride  and 
schcenite  to  crystallise.  The  result  was  potassium  chloride  and  carnallite,  which  are 
separated  by  crystallisation. 

Miiller  fuses  equivalent  quantities  of  potassium  chloride,  magnesium  sulphate,  and 
iron  oxide.  The  potassium  sulphate  is  separated  by  lixiviation, 


286  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Kainite. — In  the  interval  between  1878-1880,  sixteen  processes  were  patented  for  the 
production  of  potassium  magnesium  sulphate,  of  which  only  three  have  been  worked  on 
the  large  scale.  The  United  Chemical  Works  of  Leopoldshall  work  on  the  Borsche  and 
Briinjes  process,  the  Stassfurt  Chemical  Works  on  that  of  Dupr6  and  Hake,  and 
the  new  Stassfurt  Works  under  the  patent  of  H.  Precht.  Borsche  and  Briinjes  treat  the 
kainite  with  a  cold  saturated  solution  of  kainite  at  80° ;  on  cooling,  potassium-mag- 
nesium sulphate  crystallises.  Dupr6  and  Hake  use  in  a  similar  manner  a  con- 
centrated solution  of  magnesium  sulphate,  whilst  Precht  heats  the  kainite  with  water  or 
brine  to  120°  to  150°  under  pressure.  In  this  manner  3  tons  of  coarsely  powdered 
kainite  are  decomposed  in  about  thirty  minutes,  the  potassium-magnesium  sulphate  being 
converted  into  an  exceedingly  fine  crystalline  powder,  K2S04.2MgSO4.H2O.  For  dis- 
solving there  is  used  a  saline  solution  saturated  for  sodium  chloride,  which  may  contain 
other  of  the  salts  occurring  in  kainite.  The  proportions  are  chosen  so  that  sodium 
chloride  and  the  new  double  salt  remain  undissolved,  whilst  potassium  and  magnesium 
chlorides  remain  in  solution.  According  to  the  nature  of  the  saline  solution,  the 
decomposition  takes  place  according  to  one  of  the  two  following  equations  : — 
3(K2S04,MgS04,MgCl2,6H20)  =  2(K2SO4,2MgS04,H0O)  +  2KC1  +  aMgCl,  +  xH20,  or 
2(K2S04,MgS04,MgCl2,6H20)  =  K1S04,2MgS04,H,0  +  2MgCla  +  K2S04. 

The  transformation  ensues  according  to  the  former  equation  if  the  saline  solution 
contains,  along  with  sodium-chloride  potassium,  magnesium  sulphate  and  magnesium 
chloride,  but  chiefly  according  to  the  second,  when  it  consists  of  a  saturated  solution  of 
magnesium  chloride.  Experience  in  manufacturing  has  shown  that  the  new  salt  is 
precipitated  so  completely  from  the  decomposition-lye,  that  this  on  cooling  only  allows 
potassium  chloride  to  separate  and  does  not  contain  more  than  2^4  percent,  magnesium 
sulphate.  In  contact  with  cold  water  it  is  resolved  into  schcenite  and  epsoms.  From 
the  hot  aqueous  solution  schcenite  crystallises  out  on  cooling,  whilst  the  excess  of  mag- 
nesium sulphate  remains  in  solution.  If  a  solution  of  potassium  chloride  is  taken  as  a 
solvent,  we  find  conversion  into  schoenite  and  magnesium  chloride. 

The  potassium-magnesium  sulphate,  with  50  per  cent,  potassium  sulphate  and  3  per 
cent,  chloride,  is  in  great  demand  both  in  agriculture  and  manufactures,  and  perhaps 
from  this  cause  its  further  treatment  for  pure  potassium  sulphate  is  not  yet  carried 
out. 

The  utilisation  of  the  abundant  lyes  of  potassium  chloride  is  still  an  unsolved 
problem.  A  small  portion  is  evaporated  down,  and  the  melted  magnesium  chloride  is 
sold ;  from  a  larger  portion  the  0*2  per  cent,  of  bromine  present  is  separated  before  it 
is  let  run  into  the  streams.  At  present  about  one-third  of  the  final  lye  is  thus  treated 
with  an  annual  yield  of  300  tons. 

Production  of  Potassium  Carbonate. — Numerous  proposals  have  been  made  for  the 
most  advantageous  conversion  of  potassium  chloride  and  sulphate  into  potash.  The 
only  process  which  has  been  practically  carried  out  is  an  imitation  of  the  Leblanc  soda 
process,  first  applied  to  the  production  of  potash  by  Griineberg  (1861).  Large  quanti- 
ties of  excellent  potash  have  been  made  by  Forster  and  Gruneberg,  at  Kalk,  near 
Cologne,  at  the  Buckau  Works,  near  Magdeburg,  and  at  Stassfurt,  on  the  Leblanc 
process.  Everything  is  carried  on  as  for  soda,  save  that  in  the  black-ash  process  high 
temperatures  must  be  more  carefully  avoided.  If  the  coal  used  for  reduction  is  rich 
in  nitrogen,  potassium  ferrocyanide  is  produced.  On  evaporating  the  carbonated  lye 
to  98°  Tw.,  the  ferrocyanide  separates  out  with  the  undecomposed  sulphate  still 
contained  in  the  lyes,  and  can  be  extracted  from  the  salt  by  lixiviation  with  hot 
-water ;  a  second  re-crystallisation  converts  the  product  into  a  fine  commercial  sample. 

The  products  prepared  at  Buckau  contained  (1879) — 


SECT,  in.]  POTASSIUM   SALTS.  287 

K2COS         .        .        .         .         .  97  -30  per  cent. 

Na,CO8 0-29        „ 

K2S04 0-49        „ 

KC1 1-23        „ 

Moisture 0^69        „ 

According  to  another  process,  potassium  sulphate  containing  schcenite  is  ignited 
with  chalk  and  small  coal,  and  the  mass  lixiviated  with  water.  Potash  dissolves, 
and  calcium  sulphide  remains,  from  which  the  sulphur  is  recovered  according  to  the 
processes  of  Schaffner  and  Mond.  The  presence  of  a  certain  quantity  of  schrenite  and 
magnesium  sulphate  in  potassium  sulphate  which  is  intended  for  the  manufacture 
of  potash  is  advantageous,  since  the  crude  potash  is  thus  rendered  lighter  and  more 
porous,  and  it  is  consequently  easier  to  lixiviate  than  crude  potash  made  from  a 
pure  potassium  sulphate. 

R.  Engel  mixes  a  solution  of  potassium  chloride  with  magnesium  carbonate  and 
saturates  with  carbon  dioxide,  when  the  double  potassium-magnesium  bicarbonate 
separates  out.  When  separated  from  the  lye  of  magnesium  chloride,  this  precipitate 
is  heated  either  alone  or  along  with  water,  when  it  is  resolved  into  magnesium 
carbonate  and  potassium  carbonate — 

2MgKH(C03)J  =  2MgC03  +  K2C03  +  H2O  +  C03 

The  potassium  carbonate  is  extracted  in  the  water.     Magnesium  carbonate  and  carbon 
dioxide  go  back.     The  process  has  recently  been  given  up. 

Experiments  to  obtain  potassium  carbonates  by  the  ammonia  process  have  hitherto 
had  little  success. 

For  the  preparation  of  potassium  carbonate,  G.  Borsche  and  P.  Briinjes  introduce 
carbonic  acid  and  ammonia,  or  ammonium  carbonate,  into  the  solution  of  a  magnesium 
salt  which  holds  in  suspension  magnesia  or  magnesium  carbonate,  on  which  the 
double  ammonium-magnesium  carbonate  (containing  all  the  magnesia  in  solution)  is 
separated  out  after  some  time.  This  double  carbonate  is  mixed  with  about  an  equiva- 
lent quantity  of  potassium  chloride  or  sulphate,  an  excess  being  of  advantage,  and  with 
water,  in  order  to  bring  the  above  salts  into  solution.  Into  this  mixture  is  passed 
carbonic  acid,  or  carbonic  acid  and  ammonia,  when  the  transformation  into  potassium 
magnesium  is  promoted,  though  it  certainly  takes  place  without  the  introduction  of  car- 
bonic acid  and  ammonia.  This  preparation  of  ammonium-magnesium  carbonate,  and  its 
transformation  into  potassium-magnesium  carbonate  can  be  combined  by  introducing, 
firstly,  ammonium  carbonate  and  carbonic  acid — e.g.,  into  a  solution  of  carnallite, 
or  into  a  solution  of  potassium  magnesium  sulphate,  or  into  suspended  magnesia  or 
magnesium  carbonate,  adding  after  some  time  potassium  chloride,  and  then  again 
carbonic  acid.  They  thus  obtain  crystals  of  the  triclinic  system,  containing  potassium- 
magnesium  carbonate.  The  potassium-magnesium  carbonate  is  decomposed  into 
potassium  carbonate  and  magnesium  carbonate  by  digestion  with  water.  The  mag- 
nesium carbonate  returns  to  the  process.  This  method  is  about  to  be  introduced  on 
.a  large  scale. 

The  production  of  potassium  salts  from  felspar  is  at  present  of  no  importance. . 

In  order  to  obtain  salts  of  potassium  from  sea-water,  especially  from  the  Medi- 
terranean, the  last  mother  liquors  are  concentrated  by  evaporation,  and  mixed  with 
magnesium  chloride,  so  that  carnallite  crystallises  out.* 

Salts  of  Potassium  from  the  Ashes  of  Plants. — The  residue  left  from  the  ignition  of 
the  organic  matter,  or  wood,  as  it  is  usually  termed,  of  plants  contains  those  mineral 
substances  which  the  plant  has  taken  from  the  soil,  chiefly  potassa,  soda,  lime,  magnesia, 
small  quantities  of  the  protoxides  of  iron  and  manganese,  combined  with  phosphoric, 
sulphuric,  silicic,  and  carbonic  acids,  and  also  with  the  haloids.  These  combinations  are 

*  It  has  been  proposed  to  apply  this  process  to  the  water  of  the  Dead  Sea. 


288  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

not,  however,  the  same  as  those  existing  in  the  living  plant,  because  the  high  temper- 
ature of  the  ignition  has  the  effect  of  changing  the  affinities.  Plants  growing  near  the 
sea  generally  contain  large  quantities  of  soda,  while  those  inland  contain  generally 
more  potassa.  The  quantity  of  ash  varies  not  only  for  different  kinds  of  plants,  but  for 
various  parts  of  the  same  plant :  very  succulent  plants  and  the  most  succulent  parts  of 
others  generally  yield  the  largest  quantity  of  ash  ;  herbs  yield  more  ash  than  shrubs, 
shrubs  more  than  trees,  and  the  leaves  and  bark  of  the  latter  more  than  the  wood.  It  is 
evident  that  the  inorganic  matter,  chiefly  alkaline  salts,  being  contained  in  the  juice 
of  plants  in  a  soluble  state,  the  quantity  must  of  necessity  be  greatest  in  the  juicy  and 
succulent  parts. 

Dr.  Bottger  found  the  ash  of  beech  wood  to  contain — 

21-27  per  cent,  of  soluble  salts, 
7^73        ii        of  insoluble  salts. 

The  soluble  salts  were  found  to  be — 

Potassium  carbonate          .        .        .  15*40  per  cent. 

„          sulphate    ....  2*27        „ 
Sodium  carbonate      ....       3-40        „ 

chloride  .        .  0*20 


2 1 '27 


The  value  of  an  ash  for  the  manufacture  of  potash  is  chiefly  dependent,  in  the  first 
place,  upon  the  quantity  of  potassic  carbonate  it  will  yield,  upon  the  abundance  of  the 
wood  or  other  vegetable  product,  and  the  cost  of  labour.  The  under-mentioned  woods 
yield  on  the  average,  for  1000  parts,  the  following  quantities  of  potash  : — 


Pine 0*45 

Poplar 0-75 

Beech 1-45 

Oak 1-53 

Box  wood 2*26 

Willow 2*85 


Elm 
Wheat  straw 


3  "90 
3-90 


Bark  from  oak-knots  .  .  .4-20 
Cotton-grass  (Eriophorum  vayinatuni)  5-00 
Rushes 5-08 


Vine  wood 


5-50 


Beech  bark        .        .        .        .        .6-00 

Dried  ferns 6-26 

Stems  of  maize  (Indian  corn)    .         .   17-50 

Bean  straw 20 -co 

Sunflower  stems         .        .        .        .  20-00 

Nettles 25-03 

Vetch  straw 27-50 

Thistles 35-37 

Dried     wheat     plant     previous     to 

blooming 47-00 

Wormwood 73  "oo 

Fumitory 79-00 


Barley  straw 5-80 

According  to  M.  Hoess,  1000  parts  of  the  following  kinds  of  wood  yield— 

Ash-  Potash.  Ash,  Potash. 


Pine  .  .  .     3-40  ...  0-45 

Beech  .  .  .5-80  ...  1-27 

Ash  .  .  .   12 -20  ...  074 

Oak  .  .  .   13-50  ...  1.50 

Elm  .  .  .  25-50  ...  3-90 


Willow        .        .        .28-0  ...  2-85 

Vine  ....     34-0  ...  5-50 

Dried  ferns         .        .36-4  ...  4-25 

Wormwood         .         .97-4  ...  73-00 

Fumitory  .         .         .  219-0  ...  79-90 


The  preparation  of  potash  from  vegetable  matter  is  effected  in  three  operations, 
viz. : — 

(a)  The  lixiviation  of  the  ash. 

(b)  The  boiling  down  of  the  crude  liquor. 

(c)  The  calcination  of  the  crude  potash. 

The  combustion  of  the  vegetable  matter  should  be  so  conducted  as  to  prevent  its 
becoming  too  violent  and  giving  rise  to  the  volatilisation  of  some  of  the  reduced  potassa 
Mlt;  nor  should  too  strong  a  current  of  air  be  admitted,  for  fear  of  the  ash  being 
mechamcally  carried  off.  A  distinction  is  made  abroad— no  potash  from  wood  or  other 


SECT,  in.]  POTASSIUM  SALTS.  289 

vegetable  matter  being  produced  in  the  United  Kingdom,  nor  wood  used  as  fuel  in 
sufficient  quantities  to  yield  ash.  for  the  preparation  of  potash — between  the  ash  obtained 
by  the  combustion  of  the  refuse  wood  of  forests  and  the  ash  from  wood  used  as  fuel, 
the  former  being  termed  forest-  and  the  latter  fuel-ash.  As  ash  from  other  fuel  than 
wood  may  be  mixed  with  fuel-ash,  a  sample  may  be  roughly  tested  by  lixiviation,  and 
the  density  of  the  liquor  taken  by  the  areometer,  the  higher  the  specific  gravity  the 
larger  the  quantity  of  soluble  salts.  Formerly  the  forest-ash  was  purposely  prepared 
and  sold  to  potash-boilers.  There  is  still  known  in  Eastern  Prussia  and  Sweden  a 
material  termed  okros  or  ochras,  holding  a  position  intermediate  between  crude  ash  and 
potash. 

(a)  The  lixiviation  of  the  ash  effects  the  separation  of  the  soluble  from  the  insoluble 
saline  matter,  the  former  amounting  to  about  25  to  30  per  cent,  of  the  entire  weight  of 
the  ash.  The  operation  is  carried  on  in  wooden  vessels  shaped  like  an  inverted  trun- 
cated cone,  and  provided  with  a  perforated  false  bottom,  which  is  covered  with  straw  ; 
in  the  real  bottom  a  tap  is  fixed  for  removing  the  liquor.  If  the  lixiviation  is  system- 
atically carried  on,  several  of  these  vessels  are  placed  together,  forming  what  is  termed 
a  battery,  and  under  each  a  tank  to  receive  the  liquor.  The  ash  to  be  lixiviated  is  first 
sifted  from  the  coarse  particles  of  charcoal,  next  put  into  a  small  square  water-tight 
wooden  box,  and  thoroughly  saturated  with  water  for  at  least  twenty-four  hours.  By 
this  proceeding  the  lixiviation  is  greatly  assisted,  and  the  potassium  silicate  to  some 
extent  decomposed  by  the  action  of  the  carbonic  acid  of  the  atmosphere.  The  next  step 
is  to  transfer  the  wet  ash  to  the  lixiviation  vessel,  care  being  taken  to  press  it  tightly 
down  on  to  the  false  bottom  ;  cold  water  is  then  poured  in,  until  the  liquor  begins  to 
run  off  at  the  taps  left  open  for  that  purpose.  The  liquor  which  runs  off,  after  the 
water  has  remained  some  little  time  in  contact  with  the  ash,  is  found  to  contain  about 
30  per  cent,  of  soluble  salts,  afterwards  decreasing  to  about  10  per  cent.,  when  hot  water 
is  employed  to  compete  the  lixiviation.  The  insoluble  residue  left  in  the  lixiviation-tub 
is  of  value  as  a  manure,  on  account  of  the  phosphate  of  lime  it  contains,  and  is  also  used 
in  making  green  bottle-glass,  and  for  building  up  saltpetre-beds. 

(6)  Boiling  down  the  liquor.  The  liquor  obtained  by  lixiviation  is  of  a  brown  colour, 
owing  to  organic  matter,  humine  or  ulmine,  which  the  potassium  carbonate  has  dis- 
solved from  the  small  chips  of  imperfectly  burnt  charcoal.  The  evaporation  is  carried  on 
in  large  shallow  iron  pans,  fresh  liquor  being  from  time  to  time  added,  and  the  operation 
continued  until  a  sample  of  the  hot  concentrated  liquor  exhibits  on  cooling  a  crystalline 
solid  mass.  When  this  point  is  reached  the  fire  is  gradually  extinguished,  and  as  soon 
as  the  contents  of  the  pan  are  sufficiently  cold  to  handle,  the  solid  salt  mass  is  broken 
up ;  its  colour  is  a  deep  brown.  This  crude  product,  containing  about  6  per  cent,  water, 
is  known  in  the  trade  as  crude,  or  lump-potash.  It  is  evident  that  this  method  of 
boiling  down  may  cause  considerable  damage  to  the  iron  pans ;  therefore  in  many 
instances  the  operation  is  conducted  in  a  somewhat  different  manner.  The  liquid  is  kept 
stirred  with  iron  rakes,  and  the  salt,  instead  of  forming  a  hard  solid  mass,  is  obtained 
as  a  granular  powder,  containing  upwards  of  1 2  per  cent,  water.  Some  manufacturers 
first  separate  the  potassium  sulphate,  which,  being  less  soluble,  crystallises  before  the 
carbonate,  a  deliquescent  salt,  is  separated  from  the  liquor ;  in  most  cases,  however, 
this  operation  is  only  carried  on  where  the  potassium  sulphate  is  required  for  alum- 
making.  The  pearl-ash  or  potash  of  commerce  almost  invariably  contains  a  large 
quantity  of  potassium  sulphate. 

(c)  In  order  to  expel  all  the  water  and  to  destroy  the  organic  matter,  the  saline  mass 
is  calcined,  and  as  this  operation  was  formerly  performed  in  cast-iron  pots,  the  salt  has 
obtained  the  name  of  potash.  A  calcining  furnace,  Fig.  278,  is  now  used,  distinguished 
from  ordinary  reverberatory  furnaces  by  being  provided  with  a  double  fire-place.  These 
hearths,  one  of  which  is  exhibited  in  section  at  A,  Fig.  278,  are  placed  at  right  angles 


290 


CHEMICAL   TECHNOLOGY. 


[SECT.  m. 


to  each  other,  and  the  flame  and  smoke  meeting  in  the  centre  of  the  furnace,  pass  off 
at  0,  the  work-hole,  into  the  chimney.  Wood  is  used  as  fuel,  and  as  the  heating  of 
the  furnaces  requires  a  very  large  quantity,  they  are  only  in  use  when  a  sufficient 
supply  of  crude  potash  is  ready  for  operating  on.  The  furnace  is  thoroughly 
heated  in  about  five  to  six  hours,  care  being  taken  to  fire  gradually,  and  to  bring  the 
interior  of  the  furnace  to  nearly  red  heat,  so  that  the  vapour  due  to  the  combustion  of 
the  wood  may  not  condense  inside  the  furnace,  but  be  carried  off  by  the  flue.  The 
crude  potash,  broken  up  to  egg-sized  lumps,  is  next  added  in  such  quantities  at  a  time 
as  may  suit  the  size  of  the  calcining  hearth  ;  for  instance,  if  the  hearth  is  fitted  to 
contain  3  cwts.,  that  quantity  is  divided  into  three  portions  and  put  in  at  intervals  of  a 
few  minutes.  The  first  effect  of  the  heat  is  to  expel  the  water  from  the  potash,  the 
escape  of  the  steam  being  promoted  by  stirring  the  mass  with  iron  rakes.  In  about  an 
hour  all  the  water  is  driven  off,  and  the  mass  takes  fire  in  consequence  of  the  burning 
of  the  organic  matter,  the  salt  at  first  being  blackened,  but  gradually  becoming 
white  as  the  carbon  burns  off.  As  soon- as  this  stage  is  reached,  the  potash  is  removed 
to  the  cooling-hearth,  and,  when  cold,  packed  in  well-made  wooden  casks,  which,  as  this 
salt  is  very  hygroscopic,  are  rendered  as  air-tight  as  possible.  The  heat  of  the  furnace 

has  to  be  well  regulated 

Fig.  278.  to    prevent    the    potash 

becoming  semi-fused,  in 
which  case  it  would  at- 
tack the  siliceous  matter 
of  the  fire-bricks ;  the 
workmen  from  time  to 
time  take  a  small  sample 
to  test  how  far  the 
calcination  is  complete. 

We,  in  Europe,  ob- 
tain a  considerable 
quantity  of  potash  from 
the  United  States  and 

Canada,  known  as  American  potash,  of  which  there  are  three  kinds,  viz.  : — 
i.  Potash  prepared  as  described.  2.  Pearl-ash,  or  potash,  purified  by  lixiviation, 
decantation  from  sediment,  boiling  down,  and  the  calcination  of  the  salt  thus  obtained. 
3.  Stone-ash,  a  mixture  of  uncalcined  potash  (potassium  carbonate)  and  caustic  potash, 
obtained  by  treating  the  crude  potash  liquor  with  caustic  lime,  and  boiling  down  the 
mass  to  dryness;  this  article  has  the  appearance  of  the  crude  caustic  soda  of  this 
country,  but  is  usually  coloured  red  by  oxide  of  iron ;  the  lumps,  stone-hard,  are  from 
6  to  10  centimetres  in  thickness,  and  contain  upwards  of  50  per  cent,  caustic  potash.  The 
under-mentioned  analyses  exhibit  the  varying  composition  of  the  potash  of  commerce  : — 
Sample  i  is  from  Kasan  (Russia) ;  analyst,  M.  Herman.  2.  Tuscany.  3  and  4 — the 
latter  of  a  reddish  colour — from  North  America.  5.  Russia.  6.  Yosges  (France); 
analyst  of  2,  3,  4,  5,  and  6,  M.  Pesier.  7.  Helmstedt,  in  Brunswick;  analyst, 
M.  Limpritsch.  8.  Russia;  analyst,  M.  Bastelaer. 

Potassium  carbonate 
Sodium  „ 

Potassium  sulphate 

„  chloride 

Water      . 
Insoluble  residue     . 

The  calcined  potash  varies  in  colour,  being  either  white,  pearl-grey,  or  tinged  with 


I. 

2. 

3- 

4. 

5- 

6. 

7. 

8. 

78-0  .. 

•  74'i  •< 

.  71-4  ... 

68-0  . 

•  69-9 

...    38-6   , 

..  49-0  .. 

.    50-84 

—     .. 

•     3'°  .. 

2-3  ... 

5-8  . 

•     3'1 

...      4'2   . 

,.    —    .. 

.    12-14 

17-0  .. 

•  13'S  - 

.  I4'4  ••• 

IS'3  • 

.  14*1 

...   38-8    ., 

.  40-5  .. 

•    I7'44 

3'0  ., 

.     0-9  , 

,.     3-6  ... 

8-1  . 

,.     2-1 

...      9'I    . 

..    I0'0    .. 

.      5-80 

— 

..     7-2  . 

..     4'5  ... 

—     . 

..     8-8 

-      5'3   • 

..    —     .. 

.    IO-I8 

0'2    .. 

.       O'l     .. 

.     27  ... 

2-3  -. 

•     2-3 

....    3'8  .. 

.    —     .. 

•     3'6° 

SECT,  in.]  POTASSIUM  SALTS.  291 

yellow,  red,  or  blue.  The  red  colour  is  due  to  oxide  of  iron,  the  blue  to  the  manganates 
of  potash.  It  is  a  hard,  light,  porous,  non-crystalline  mass,  never  entirely  soluble  in  water. 
Formerly,  a  large  quantity  of  potash  was  obtained  from  the  residues  of  wine-making 
and  called  vinasse,  the  semi-liquid  left  after  the  alcohol  has  been  distilled  from  the 
wine,  and  containing,  among  other  substances,  argol,  or  crude  potassium  bitartrate  ;  it 
was  boiled  down,  and  next  calcined,  yielding  a  kilo,  of  very  good  potash  for  every 
hectolitre  of  vinasse.  The  large  quantity  of  potash  thus  formerly  produced  may  be 
judged  from  the  fact  that  nineteen  of  the  wine-producing  departments  of  France,  those 
only  where  large  quantities  of  wine  are  converted  into  alcohol,  technically  termed  trois-six 
and  cinq-huit,  yield  annually  about  9  to  10  million  hectolitres  of  vinasse,  at  the  present 
time  employed  for  the  preparation  on  a  large  scale  of  cream  of  tartar,  glycerine,  and 
tartaric  acid. 

5.  Salts  of  Potassium  from  the  Treacle  or  Molasses  of  Beet-root  Sugar. — Of  late  years, 
the  manufacture  of  potash  salts  from  the  vinasse  left  after  the  distillation  of  fermented 
beet-root  molasses  has  been  added  as  a  new  branch  of  industry  by  M.  Dubrunfaut,  and 
introduced  into  Germany  by  M.  Varnhagen,  in  the  year  1840,  at  Mucrena,  Prussian 
Saxony. 

Beet-root,  on  being  subjected  to  ignition,  yields  an  ash  containing  a  large  percentage 
of  potash,  a  fact  first  observed  in  the  early  part  of  this  century  by  M.  Mathieu  de 
Dombasle,  a  celebrated  French  agriculturist,  who  discovered  that  100  kilos,  of  dried 
beet-root  leaves  yield  10-5  kilos,  of  ash,  containing  5*1  kilos,  of  potash  ;  but  this  author's 
idea  that  the  leaves  might  be  cut  off  and  gathered  for  the  purpose  of  potash  manu- 
facture proved  erroneous,  in  so  far  that  the  growth  of  the  roots  was  greatly  impeded. 
After  the  publication  of  M.  Dubrunfaut's  researches  on  this  subject,  in  1838,  the 
vinasse  of  the  beet-root  molasses  distillation  was  evaporated  to  dryness,  next  calcined, 
and  the  calcined  mass  refined  for  the  production  of  potash  and  other  salts  of  that  base, 
an  industry  which  has  obtained  a  great  development,  as  may  be  judged  from  the  fact 
that  the  quantity  of  these  materials  produced  on  the  European  continent  in  1865 
amounted  to  240,000  cwts. 

The  reader  who  desires  details  on  this  subject  is  referred  to  the  work,  On  the 
Manufacture  of  Beet-Root  Sugar  in  England  and  Ireland,  by  Wm.  Crookes,  F.R.S., 
<kc.,  p.  250  et  seq. 

The  molasses  from  beet-root  sugar  consists,  previous  to  fermentation  and  dis- 
tillation, of  the  under-mentioned  substances,  as  recorded  by  the  several  analysts  whose 
names  are  subjoined  : — 

Brunner.  Pricke.  Lunge.  Heidenpriern. 

Water 15-2        ...         iS'o        ...         18-5        ...        19-0    197 

Sugar 49-0        ...        48^0        ...         507         ...        46*9    49-8 

Salts  and  organic  substances      .     35-8         ...         34^0        ...         30*8         ...         34'!     30*5 

The  following  analyses  by  M.  Heidenpriern  exhibit  the  average  composition  of  the 
ashes  of  molasses  : — 

I.  2.  3. 

Potassa       .        .        .  5172  ...  47-67  ...  50-38 

Soda    ....  8'do  ...  1 1 '43  ...  8-29 

Lime  ....  5-04  ...  3-60  ...  3-12 

Magnesia    .        .        .  o-i8  ...  O'lo  ...  O'i8 

Carbonic  acid      .         .  28-90  ...  27-94  ...  28-70 

The  remainder  of  the  100  parts  consists  of  phosphoric  and  silicic  acids,  chlorine, 
oxide  of  iron,  &c.  The  quantity  of  such  substances  amounts  to  10  or  12  per  cent. 
According  to  Dubrunfaut,  the  alkalimetrical  degree  of  the  ash  of  beet-root  sugar 
molasses  is  a  constant,  as  the  ash  obtained  from  100  grammes  of  molasses  neutralises  on 
an  average  7  grammes  of  sulphuric  acid  (HjS04). 


292  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

The  molasses  is  generally  treated  in  the  following  manner  : — It  is  first  diluted  with 
either  water  or  vinasse  to  8°  or  11°  B.  =  1*056  or  1-078  sp.  gr.,  and  mixed  with  0-5  to 
i '5  per  cent,  of  a  pure  mineral  acid,  the  object  of  this  addition  being  not  simply  the 
neutralisation  of  the  alkali,  but  also  the  conversion  of  dextrine  and  such  unfermentable 
sugar  into  fermentable  sugar.  Formerly,  sulphuric  acid  was  used,  but  upon  the  re- 
commendation of  M.  Wurtz,  hydrochloric  acid  is  now  generally  employed,  the 
advantage  being  the  formation  of  readily  soluble  chlorides,  instead  of  comparatively 
insoluble  alkaline  sulphides,  by  the  action  of  the  organic  matter  present  in  the  molasses. 

The  diluted  molasses  is  next  mixed  with  yeast,  left  to  ferment,  and  the  alcohol  dis- 
tilled off;  the  residue  is  a  liquid  of  about  4°  B.  density  [=1-027  sp.  gr.]  containing 
undecomposed  yeast,  ammoniacal  salts,  various  organic  substances,  and  all  the  inorganic 
salts  of  the  beet-root  juice.  The  potassa  is  present  in  this  liquid  as  nitrate  chiefly, 
although  by  the  addition  of  hydrochloric  acid  a  portion  of  this  salt  is  decomposed,  red 
nitrous  fumes  sometimes  being  seen  in  the  fermentation  room.  Evrard  suggested  that 
the  saltpetre  should  be  separated  from  the  beet-root  molasses  by  evaporation,  and 
further  purified  by  the  aid  of  the  centrifugal  machine.  The  acidity  of  the  vinasse  is 
neutralised  by  chalk,  and  afterwards  it  is  evaporated  to  dryness  in  an  iron  vessel,  the 
total  length  of  which  is  20-3  metres,  by  an  average  width  of  1-6  metre,  extended  at  the 
top  to  2  metres,  the  depth  being  0-34  metre.  The  vessel  is  made  of  stout  boiler  plate, 
strengthened  by  stays  and  angle  irons,  and  is  divided  into  two  divisions,  the  larger  of 
which  has  a  length  of  14-2  metres,  and  is  the  real  evaporating  pan,  while  the  other  is 
used  as  a  calcining  furnace,  and  covered  with  an  arch  of  fire-bricks  o'6  metre  high. 
The  fire-place  is  1-3  metre  wide,  and  the  fire-box  has  a  surface  of  3-3  square  metres. 
The  evaporation  is  effected  by  surface  heating,  that  is  to  say,  the  flame  and  hot  gases 
from  the  burning  fuel  after  passing  across  the  fire-bridge  are  conducted  over  the 
surface  of  the  vinasse,  the  calcining  pan  being  nearest  to  the  fire,  while  the  evaporating 
pan  is  at  its  other  extremity  in  contact  with  the  flue  or  chimney.  The  vinasse,  having 
been  run  off  from  the  still,  is  kept  in  cisterns,  from  which  it  is  forced  by  means  of  a 
pump  into  a  reservoir  so  placed  as  to  admit  of  the  liquid  running  in  a  constant  stream 
into  the  evaporating  pan.  At  a  first  operation  both  the  evaporating  and  the 
calcining  pan  are  filled  with  vinasse,  but  afterwards  the  latter  is  filled  regularly  with 
concentrated  thick  liquor,  which  is  simply  carbonised,  only  the  organic  matter  being 
destroyed. 

The  daily  average  of  carbonised  vinasse  is  about  5  to  5^  cwts.  The  composition  of 
that  substance  may  be  gleaned  from  the  following  approximative  analysis : — 

Insoluble  matter =23-00  per  cent. 

Potassium  sulphate  .  .  .  .  =11-07  » 

„  chloride  .  .  .  .  =  ir6i  „ 

„  carbonate  .  .  .  .  =31-40  „ 

Sodium  „  .        .        .        .  =  23-26        „ 

Silica  and  potassium  thiosulphate  .        .  =  traces      „ 


100-34       „ 

In  Germany  the  calcined  vinasse  is  generally  sold  to  saltpetre  manufacturers,  but 
in  Belgium  and  France  this  material  is  calcined,  lixiviated,  and  the  salts  it  contains 
separately  obtained.  For  this  purpose  the  vinasse  is  first  evaporated  to  38°  or  40°  B. 
(1-33  to  1-35  sp.  gr.),  and  next  carbonised  and  calcined  in  a  furnace  constructed  as 
exhibited  in  Fig.  279.  V  is  a  reservoir  containing  the  concentrated  vinasse,  which  by 
means  of  a  tube  is  gradually  run  into  a  furnace,  of  which  G  is  the  fire-place,  M  the 
calcination  space,  destined  to  contain  the  concentrated  or  carbonised  vinasse,  which  is 
evaporated  to  dryness  and  calcined  in  M1 ;  a  door  is  fitted  to  each  compartment,  and  at 
P,  the  end  of  the  furnace  opposite  to  the  fire-place.  The  air  required  for  the  caloina- 


SECT.    III.] 


POTASSIUM   SALTS. 


293 


tion  is  admitted  partly  through  the  ash-pit,  partly  through  the  openings,  B,  in  the 
brickwork.  The  thickish  liquid  vinasse  admitted  into  M1  is  constantly  stirred,  and,  as 
soon  as  it  is  quite  dry,  it  is  shovelled  across  the  brickwork  bridge,  A',  into  the  calcining 
space,  M,  care  being  taken  to  again  fill  M'  with  concentrated  vinasse.  The  organic 
matter  of  the  saline  mass  soon  takes  fire,  emitting  noxious  fumes.  The  calcination  is 
greatly  aided  by  the  access  of  air  at  B,  and  also  to  some  extent  by  the  potassium 
nitrate  present.  The  temperature  has  to  be  regulated  to  prevent  the  salts  becoming 
fused  and  forming  a  hard  compact  mass,  in  which  case  the  potassium  sulphate  would 
be  reduced  to  potassium  sul- 
phide, a  salt  which  could  not  £•  279- 
be  removed.  The  calcined 
vinasse,  technically  termed 
satin,  contains,  when  removed 
from  the  surface,  10  to  25  per 
cent,  of  insoluble  substances, 
viz.,  calcium  carbonate  and 
phosphate,  more  or  less  char- 
coal, and,  in  addition,  3  to  4 
per  cent,  moisture ;  the  re- 
mainder consists  of  potassium 
and  sodium  carbonates,  potas- 
sium sulphate  and  chloride, 
and  sometimes  cyanide  in  con- 
siderable quantity.  The  relative  quantities  of  potassa  and  soda  are,  of  course,  not  at 
all  constant,  but  vary  according  to  the  soil  on  which  the  beets  have  grown  ;  it  has 
been  observed  in  France  that  the  molasses  obtained  from  beets  grown  in  the  Depart- 
ment Nord  are  less  rich  in  potassa  than  those  grown  in  the  Departments  Oise  and 
Somme.  The  average  composition  of  the  saline  is — 

7  to  12  per  cent,  of  potassium  sulphate. 
1 8  to  20        „         of  sodium  carbonate. 
17  to  22        „         of  potassium  chloride. 
30  to  35        „         of          „          carbonate. 

The  complete  composition  of  the  saline  may  be  gathered  from  the  following  tabulated 
results : — 

a.  6.  c.  d. 

.       22-20  ...  19-82  ...  17-47  ...  13-36 

.   12-95      -       9-88      ...       2-55      ...       3-22 

.     15-80  ...  20-59  ...  18-45  •••  16-62 

0-13  ...  0-15  ...  0-18  ...  0-21 

.    25-52  ...  19-66  ...  19-22  ...  16-54 

.     23-40  ...  29.90  ...  42'i3  —  5°'°S 


Water  and  insoluble  matter 
Potassium  sulphate 
„        chloride 
Rubidium        ,, 
Sodium  carbonate 
Potassium      „ 


lOO'OO 


lOO'OO 


lOO'OO 


The  method  of  separating  the  soluble  salts  from  each  other  invented  by  M.  Kuhl- 
mann  is  generally  executed  as  follows  : — The  saline  mass  is  first  broken  up  and  granu- 
lated by  the  aid  of  grooved  iron  rollers,  after  which  it  is  placed  in  lixiviation-tanks, 
each  containing  26-4  cwts.,  and  arranged  precisely  in  the  same  manner  as  those  in  use 
in  soda  works.  The  liquor  tapped  from  the  tanks  has  asp.  gr.  of  1-229  (  =  27°  B.); 
the  insoluble  residue  is  used  as  manure.  The  liquor  having  been  collected  in  a  large 
reservoir,  capable  of  containing  some  210  hectolitres,  is  concentrated  by  waste  heat 
(abgangige  warme)  to  a  density  of  1*26  (  =  30°  B.) ;  on  cooling,  the  greater  part  of  the 
potassium  sulphate  crystallises,  and  is  removed,  care  being  taken  to  wash  off  the 
adhering  mother-liquor.  The  sulphate  thus  obtained  contains  80  per  cent,  pure 


294  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

potassium  sulphate,  the  rest  being  carbonate  of  potassa  and  organic  matter  ;  this  material 
is  converted  into  potash  by  Leblanc's  process.  The  liquor  at  30°  B.  is  next  poured  into 
evaporating- pans,  each  capable  of  containing  90  hectolitres,  and  concentrated  by  means 
of  heat  and  a  steam  pressure  of  3  atmospheres  ( =  45  Ibs.  to  the  square  inch)  to  a 
density  of  42°  B.  (=  1*408).  By  this  operation  a  mixture  of  sodium  carbonate  and 
potassium  sulphate  is  separated,  which  frequently  exhibits  30  alkalimetrical  degrees  * 
the  liquor  is  transferred  from  the  evaporating-pans  to  crystallising  vessels,  in  which  it 
is  cooled  down  to  not  less  than  30°.  If,  by  carelessness,  the  temperature  should  fall 
below  30°,  the  potassium  chloride  crystals  become  mixed  with  a  layer  of  sodium  car- 
bonate. The  liquor  at  a  temperature  of  30°,  and  having  a  density  of  42°  B.,  is  again 
transferred  to  evaporating-pans  each  capable  of  containing  20  hectolitres,  and  evaporated 
in  winter  to  a  sp.  gr.  of  1*494  ( =  48°  B.),  and  in  summer  to  a  sp.  gr.  of  1*51  (  =  49°  B.). 
By  this  operation  sodium  carbonate  separates,  the  first  and  purer  proportions  of  which 
are  of  82  alkalimetrical  degrees,  and  the  last  of  50°  only. '  After  the  separation  of  the 
salt,  the  remaining  liquor  is  poured  into  small  crystallising  vessels,  each  capable  of 
holding  2^  hectolitres,  and,  having  been  left  standing  for  some  time,  yields  in  each 
vessel  about  130  kilos,  of  a  crystalline  salt,  mainly  composed  according  to  the  formula 
K2C03  +  Na8CO3  +  i2H80.  The  remaining  mother-liquor,  when  evaporated  to  dry- 
ness  and  calcined,  yields  a  semi-refined  potash,  tinged  with  red  by  oxide  of  iron.  This 
product  is  again  lixiviated  with  water,  and  the  liquor,  having  been  concentrated  to  1*51 
to  1*525  sp.  gr.  ( =  49°  to  50°  B.),  deposits  a  large  quantity  of  potassium  sulphate  and 
sodium  carbonate.  The  mother-liquor,  having  been  again  evaporated  and  calcined, 
yields  a  potash  consisting  of  100  parts  of — 

Potassium  carbonate        .        .        .        ,         .         91  -5 
Sodium  „  .'....          5*5 

Potassium  chloride  and  sulphate     .        .        ;.-    '•      3-0 


The  sodium  carbonate  possessing  a  strength  of  80  to  85  alkalimetrical  degrees  is 
refined  by  being  washed  with  a  very  concentrated  aqueous  solution  of  sodium  carbonate, 
and  thus  brought  to  a  strength  of  fully  90  alkalimetrical  degrees. 

The  sulphate  of  potassa,  chloride  of  potassium,  and  the  double  salt  of  the  two 
carbonates  are  purified  and  re-crystallised.  The  following  analyses  exhibit  the  com- 
position of  refined  potash  obtained  from  beet-root  sugar  molasses : — 

a.  b.  e. 

Potassium  carbonate .        .        .  8873  ...  94*39  ...  89*3 

Sodium             „  6-44  •••  tracer  ...  5-6 

Potassium  sulphate  .        .        .  2*27  ...  0-28  ...  2*2 

„        chloride    .        .        .  ,      *roo  ...  2-40  ...  1*5 

„        iodide        .        .        .  o'O2  ...  0*11  ...  — 

Water 1*39  ...  176  ...  — 

Insoluble  substances          ..       .  0*12  ...  ...  — 

a  and  b  are  from  Waghausel  in  Baden ;  c  is  doubly  refined  French  potash.     The 

crude  potash  from  beet-root  sugar-works,  a  product  not  to  be  confused  with  salin,  is 
composed  as  follows  : — 

o.                     b.                    c.                    d.  e. 

Potassium  carbonate         .        53*9        ...        79-0  ...        y6'oo      ...        43-0  ..  32-9 

Sodium            „         .        .        23*1        ...        14-3  ...        16-30      ...        17-0  ...  18-5 

Potassium  sulphate  .        .          2^9        ...          3*9  ...          1-19      ...          4-7  ...  14-0 

„          chloride    .       .        19-6        ...          5-8  ...          4-16      ...        i8'o  ...  16*0 

a  is  a  French  product ;  b,  from  Valenciennes ;  c,  from  Paris ;  d,  Belgian ;  e,  from 
Magdeburg,  Prussia. 


SECT,  in.]  POTASSIUM   SALTS.  295 

With  recent  improvements  in  the  manufacture  of  beet-sugar  the  production  of  the 
treacle,  which  is  not  fit  for  human  consumption,  has  been  much  reduced.  Con- 
sequently, less  potash  is  obtained  from  this  source. 

6.  Salts  of  Potassium  from  Sea-weeds. — Potassa  salts  are  obtained  in  large  quantities 
from  various  sea-weeds,  as  a  bye-product  of  the  manufacture  of  bromine  and  iodine. 
The  three  following  methods  are  employed  for  this  purpose  : — 

(a)  The  old  calcination  method,  consisting  in  a  complete  reduction   of  the  weeds  to 
ash,  and  the  methodical  lixiviation  of  that  product,  so  as  to  obtain  various  salts  by 
crystallisation. 

(b)  The  carbonisation  on  Stanford's  method,  consisting  in  the  dry  distillation  of  the 
weeds  to  convert  them  into  a  carbonaceous  mass,  afterwards  lixiviated,  while  products 
are  simultaneously  obtained  the  sale  of  which  considerably  lessens  the  cost  of  the  pre- 
paration of  the  potassa  salts. 

(c)  A  third  mode  of  treatment,  that  of  Kemp  and  Wallace,  consisting  in  boiling 
the   weeds   with   water,   evaporating   the   solution,   and    carefully  incinerating    the 
residue. 

The  oldest  method  is  still  the  most  generally  employed  in  France,  on  the  coasts  of 
Brittany  and  Lower  Normandy,  especially  in  the  neighbourhood  of  Brest  and  Cher- 
bourg, and  in  Scotland  and  Ireland. 

The  process  is  mainly  conducted  as  follows : — After  drying  in  the  air,  the  plants 
are  incinerated,  the  result  of  which  is  the  formation  of  a  black  semi-fused  mass,  which 
in  France  is  termed  Varech  or  Vraic,  and  in  England  and  Scotland  is  known  as  kelp.  A 
distinction  is  made  between  the  kelp  obtained  by  the  incineration  of  the  weeds,  Fucus 
s&rratus  and  Fucus  nodosu&,  found  on  rocks  near  the  sea-coast,  and  the  kelp  obtained 
from  the  plant  botanically  known  as  Laminaria  digitata,  thrown  up  on  the  coast  during 
the  storms.  The  latter  is  richer  in  potassa  salts,  but  contains  much  less  iodine ;  it  is 
found  plentifully  on  the  western  coasts  of  Scotland  and  Ireland,  while  on  the  eastern 
coast  of  the  British  Isles  the  other  weed  is  the  chief  source  of  kelp,  having  an  average 
composition  of — 

Insoluble  matters 57'OOO 

Sodium  sulphate io-2O3 

Potassium  chloride          ....         I3'4?6 

Sodium  i6'Oi8 

Iodine o-6oo 

Other  salts       ......          2703 


The  best  kelp  met  with  in  commerce  is  that  from  the  island  of  Rathlin,  the  value 
at  Glasgow  amounting  to  ^£7  los.  to  ;£io  105.  per  ton  of  22^  cwts. ;  while  Galway  kelp 
is  valued  at  only  £2  or  ^3  per  ton,  owing  to  the  large  quantity  of  salt  it  contains. 
Twenty-two  tons  of  moist  sea-weed  yield — 

Medium  kelp i  ton 

Potassium  chloride 5  to  6  cwts. 

„          sulphate          .        .        .        .        3  cwts. 

The  Scotch  mode  of  treating  kelp  is  briefly  the  following : — The  material  is  first 
broken  into  small  lumps,  and  put  in  large  iron  cauldrons,  hot  water  being  added  to 
exhaust  all  the  soluble  matter.  This  operation  follows  the  method  of  the  manufacture 
of  soda  from  common  salt,  to  be  presently  considered.  The  water  is  first  made  to  act 
upon  nearly  exhausted  kelp,  and  at  last  with  quite  fresh  kelp,  until  a  liquid  is  pro- 
duced marking  36°  to  40°  Tw.  =  n 8  to  1-20  sp.  gr.  The  insoluble  residue  contains 
chiefly  silica,  sand,  calcium  and  magnesium  carbonates,  their  sulphates  and  phosphates, 


:»96  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

and  particles  of  charcoal,  and  is  used  for  bottle-glass  manufacture.  The  liquor  from 
the  kelp  is  evaporated  in  large  cast-iron  semi-globular  cauldrons  by  the  direct  action 
of  a  coal  fire,  and  contains  chiefly  potassium  chloride,  a  comparatively  small  quantity  of 
sodium  chloride,  potassium  sulphate  and  chloride,  some  sodium  carbonate,  potassium 
iodide  and  sulphide,  and  potassium  and  sodium  dithionites.  The  mode  of  separating  these 
salts  from  each  other  is  based  upon  their  varying  solubility  in  water,  and  is  therefore 
conducted  by  alternate  evaporation  and  cooling.  As  the  potassium  sulphate  is  the 
least  soluble,  it  falls  to  the  bottom  of  the  cauldron  during  the  first  evaporation,  and  is 
collected  by  the  workmen  by  means  of  perforated  ladles,  and  brought  into  the  trade  as 
plate  sulphate.  After  this  salt  has  been  collected  the  liquid  is  run  into  coolers,  in 
which  the  greater  bulk  of  the  potassium  chloride  crystallises ;  the  mother-liquor  from 
these  crystals  is  again  transferred  to  the  evaporator,  and  by  the  continued  appli- 
cation of  heat,  and  consequent  concentration,  the  common  salt  is  separated.  It 
should  be  borne  in  mind  that  common  salt  is  scarcely  more  soluble  in  hot  than 
in  cold  water,  while  the  solubility  .of  most  other  salts  is  greatly  increased 
by  a  higher  temperature ;  it  is  therefore  possible  to  push  the  evaporation  and 
concentration  to  the  point  of  incipient  precipitation  of  the  potassium  chloride,  the 
common  salt  being  then  ladled  out  of  the  cauldron,  and  the  liquid  again  run  into 
the  coolers  in  order  to  obtain  another  deposit  of  potassium  chloride,  always  more  or 
less  contaminated  with  common  salt.  This  operation  is  repeated  four  times ;  the  first 
crop  of  potassium  chloride  contains  from  86  to  90  per  cent,  of  this  salt,  the  re- 
mainder is  chiefly  potassium  sulphate  ;  the  second  and  third  crop  yield  a  very  pure  salt, 
96  to  98  per  cent,  of  potassium  chloride ;  the  fourth  crop  contains  some  sodium 
sulphate  mixed  with  the  potassium  chloride.  The  liquor  left  after  the  fourth  crystal- 
lisation having  a  sp.  gr.  =  i'33  to  1-38  =  66°  to  76°  Tw.,  and  containing  among  other 
compounds  sodium  sulphate,  alkaline  sulphides,  thiosulphates  and  carbonates,  and 
iodide  of  potassium,  is  not  submitted  to  further  evaporation,  but,  having  been 
poured  into  shallow  vessels  placed  in  the  open  air,  is  mixed  with  dilute  sulphuric 
acid,  sulphuretted  hydrogen  and  carbonic  acid  gases  being  largely  evolved,  while,  in 
consequence  of  the  decomposition  of  the  polysulphides  and  thiosulphates,  a  thick  foam 
of  pure  sulphur  appears  on  the  surface  of  the  liquid.  The  sulphur  is  ladled  off,  and 
after  having  been  washed  on  filters  and  dried,  is  sold.  Almost  as  soon  as  the  evolution 
of  gas  ceases,  there  is  added  to  the  liquid  more  sulphuric  acid  and  some  manganese, 
and  the  mixture  treated  for  the  preparation  of  iodine  (quod  vide). 

In  order  to  guard  against  loss  of  valuable  substances  by  volatilisation  during  the 
crude  and  imperfect  mode  of  incineration,  it  has  been  tried  to  simply  carbonise  the 
weeds  (Stanford's  method).  The  weeds  are  first  dried  and  strongly  pressed  into  the 
shape  of  peat  blocks ;  these  are  submitted  to  dry  distillation  in  retorts  arranged  similarly 
to  those  in  gas-works.  The  products  of  the  dry  distillation  collected  in  the  usual 
manner  contain  in  100  parts  of  fresh  weed — 

68'5  to  72-5  parts  of  ammoniacal  liquor 

4'o      „        tar 

7*0  to    7 '5       „         carbonised  weed  or  coke-weed 
2'o  to    2'5       „         illuminating  gas 

The  coke  contains  33  per  cent,  carbon,  the  remainder  consisting  of  alkaline  and 
earthy  salts ;  the  volatile  products  of  the  distillation  are  treated  for  parafime,  photogen, 
acetic  acid,  and  ammoniacal  salts,  the  gas  being  used  for  lighting  purposes.  Although 
Mr.  Stanford's  mode  of  treatment  is  undoubtedly  rational,  there  are  difficulties  in  its 
practical  execution  which  have  prevented  its  adoption  in  Scotland  as  well  as  in  France. 
The  quantity  of  potash  salts  obtained  from  sea-weeds  in  the  year  1865  amounted, 


SECT.    III.] 


POTASSIUM   SALTS. 


297 


according  to  M.  Joulain,  to  a  total  of  2,700,000  kilos.,  of  which  the  United  Kingdom 
produced  1,200,000  kilos.,  the  remainder  being  furnished  by  France. 

Since  the  production  of  potassium  chloride  at  Stassf  urt  and  Kalucz  has  become  so 
extensive,  that  of  potassa  salts  from  sea-weeds  is  of  little  consequence. 

7.  Salts  of  Potassium  from  the  Suint  of  Wool. — Raw  wool  contains  about  20  per 
cent,  of  suint  soluble  in  cold  water.  It  consists  of  the  potassium  compounds  of  oleic, 
stearic,  and  acetic  acids  with  a  little  valerianic  acid  and  many  other  organic  matters,  as 
well  as  potassium  chloride  and  sulphate,  ammonium  compounds,  and  generally 
potassium  carbonate  or  some  sodium  compounds.  The  portion  of  raw  wool  soluble  in 
carbon  disulphide  consists  essentially  of  cholestearine,  and  a  smaller  proportion  of  iso- 
cholestearine,  partly  free,  but  chiefly  combined  with  fatty  acids  and  a  little  benzoic  acid. 
The  recent  researches  of  Chludinsky  show  how  these  substances  differ  in  their  pro- 
portions. He  has  determined  both  the  moisture,  and  the  quantity  of  matter  soluble 
in  water  and  in  carbon  disulphide  in  average  samples  of  the  fleecas  of  different  herds  of 
sheep. 


Race  and  Characters  of  Sample. 

Moisture. 

Loss  in 
Water. 

Loss  in 
Carbon  Di- 
sulphide. 

Pure  Wool. 

fNegretti  ram,  from  Konska-Wola  . 

1  5  '42 

47-28 

21  '6l 

15-69 

H            ii        i>               »               • 

1172 

5473 

I3-33 

2O  '22 

Merino  -\  Negretti  sheep   „               „               . 

11-81 

44-54 

26-IO 

I7-55 

1  Australian  ram       ..... 

i3'23 

33'57 

I3-24 

39-96 

iRambouillet  ram,  from  Karlow 

ii  '45 

46-95 

I4-83 

26-77 

Southdown,  from  Poland       

8-18 

62-41 

4-61 

24-30 

Do.  from  England          ...... 

11-90 

39-21 

973 

39T6 

Oxfordshire  sheep,  from  Poland    .... 

10-86 

41-27 

4-83 

43  '04 

8  '04 

•JI-O2 

8-25 

•?2'6q 

i?'8i 

J*    w** 

2TI4 

"       j 

o'Q$ 

O            -7 

58-08 

J       J 

11-87 

2  *t 
16*10 

s  j 

4'QI 

j 
67*12 

Black  wool,  from  Podolia      

1  1  <_»/ 

1  2  '2  J 

5-66 

*T    J7* 

1-82 

80-29 

„          ,,        „      Kijew  Government    . 

"•59 

3-6r 

0-88 

83-92 

,,          „        „     Wolhynia  Government 

10  -6o 

6-35 

2'45 

80-60 

White  wool,  from  Radom  Government 

10-70 

7-40 

0-65 

81-21 

Maumene  and  Rogelet  took  out  an  English  patent  for  obtaining  potash  from  wool, 
and  showed  the  first  specimens  of  this  new  product  at  the  London  Exhibition  of  1862. 
The  raw  wool  compressed  in  casks  was  extracted  with  cold  water,  the  liquid  obtained, 
of  the  sp.  gr.  i'oi,  was  concentrated,  the  brown  residue,  "potassium  suintate,"  was 
ignited  in  retorts  to  yield  lighting-gas,  and  the  residual  carbonaceous  matter  yielded  a 
pure  potash  on  lixiviation.  The  treatment  of  suint  was  introduced  into  Germany  by 


Fig.  280. 


F.  Hartmann,  and  there  are  now  works  for  this  purpose  at  Doehren,  Bremen,  &c. 
In  France  there  are  many  such  establishments — at  Roubaix,  Rheims,  EHxeuf ,  &c. ;  and 
at  Liege,  Yerviers,  and  Antwerp  in  Belgium.  The  evaporation  of  the  lyes  is  conducted 
in  Germany  and  Belgium  in  reverberatories.  At  Doehren,  the  liquors  from  the 
ext  tion  of  the  wool  are  pumped  into  an  iron  tank  A  (Fig.  280),  where  they  undergo 


SQ8  CHEMICAL   TECHNOLOGY.  [SECT.  111. 

a  preliminary  heating  from  the  combustion  of  the  escaping  gases,  and  are  then 
pumped  into  the  evaporator,  E.  The  condensed  residues  are  next  removed  into 
the  calcining  space,  C.  As  soon  as  they  have  been  thoroughly  dried  by  the  flames 
coming  from  the  fire-box,  x,  the  fatty  matter,  dirt,  &c.,  burn,  giving  off  con- 
siderable heat,  so  that,  by  regulating  the  access  of  air,  it  is  possible  to  evaporate  12 
kilos,  of  liquid,  with  i  kilo,  of  coal.  The  fire-box,  the  calcining  space,  and  the  evaporator 
are  built  of  fire-proof  tiles  or  stones,  and  the  chimney,  n,  is  constructed  of  fire-bricks. 
The  crude  potash  contained — 

Soluble  salts         .       ' .        .";"•'  '"•    92 '05  per  cent. 

Insoluble  salts 4'92        » 

Organic  matter 3'°3        » 

The  soluble  salts  had  the  following  composition — 

Potassium  carbonate 85 -34  per  cent. 

„          chloride 6*15        „ 

„         sulphate 2 '98        „ 

Sodium  carbonate      .        .         .         .         .  5'°2        » 

A  part  of  the  impurities  is  derived  from  the  river  water  used  for  lixiviation. 
W.  Graff,  of  Lesum,  in  1878,  worked  up  the  crude  potash  from  six  wool  washeries  to 
pure  potassium  carbonate,  bicarbonate,  chloride,  and  sulphate. 

We"rotte,  of  Yerviers,  found,  in  1873,  in  two  samples  of  potash  from  suint — 

Potassium  carbonate       .         .     68-50  per  cent.        ...        64-30  per  cent. 
„          sulphate         .        .2-10  ...          2-49 


silicate  .  .  .  8*50 
„  chloride  .  .  12-50 
Sodium  carbonate  .  .  .3-20 
Water  .  .  '  '-.  .  .  2-77 
Insoluble  .  .  .  .1-48 
Loss  .....  0-95 


8-00 

16-88 

3-10 

2-80 

i '55 
0-88 


Altogether  about  1000  tons  of  potash  are  obtained  from  suint  every  year. 

Pure  potassium  carbonate  as  it  is  met  with  in  laboratories  was  formerly  obtained 
by  igniting  tartar,  or  a  mixture  of  tartar  and  saltpetre,  or  by  calcining  potassium 
acetate.  At  present  it  is  produced  by  the  cautious  ignition  of  a  mixture  of  potash 
saltpetre  with  an  excess  of  charcoal,  by  igniting  potassium  bicarbonate,  or  by  precipi- 
tating a  solution  of  potassium  chloride  with  ammonium  dicarbonate  in  presence  of 
alcohol.  In  England  potassium  carbonate  is  made  industrially  for  the  manufacture  of 
flint-glass,  which  owes  its  freedom  from  colour  not  merely  to  the  use  of  lead-glass,  but 
also  to  the  employment  of  quite  pure  materials.  The  pure  crystalline  potassium 
carbonate,  containing  16  to  18  per  cent,  of  moisture  (corresponding  approximately  to 
the  formula,  4K2C03.7H20),  is  met  with  in  the  form  of  small  cubes.  The  raw  material 
is  the  American  pearl-ash,  which  is  melted  in  a  furnace  of  the  construction  of  a 
common  side-furnace,  with  the  addition  of  sawdust  in  order  to  convert  the  potassium 
hydroxide  and  sulphide  into  carbonate.  The  melted  ash  is  dissolved,  the  solution  let 
settle,  drawn  off  clear  from  the  sediment,  and  evaporated  down  in  a  reverberatory, 
when  the  mass  appears  as  a  blackish-grey  powder.  It  is  again  dissolved,  the  solution 
clarified  by  standing,  and  evaporated  to  dryness  in  a  third  reverberatory,  when  the 
product  is  white.  It  is  now  dissolved  for  the  third  time,  evaporated  until  all  the 
potassium  sulphate  has  crystallised  out,  and  the  mother-liquor  is  again  evaporated 
until  on  cooling  it, forms  a  crystalline  mass  with  the  above-named  proportion  of 
water. 


SUCT.  III.] 


POTASSIUM   SALTS. 


299 


Table  of  the  Proportion  of  Potash  in  Lyes  according  to  Specific  Gravity  at  15' 


Specific 
Gravity. 

Baurne. 

Twaddell. 

Per  cent. 
K3C03. 

i  cubic  metre 
contains 
kilos,  of 
K2C03. 

Specific 
Gravity. 

Ban  me. 

Twaddell. 

Per  cent. 
K2CO3. 

i  cubic  metre 
contains 
kilos,  of 
K2C03. 

I  -014 

2° 

2-8° 

n 

15 

1-241 

28° 

48-2° 

24-5 

3°4 

I  '029 

4 

5-8 

3-1 

32 

1-263 

30 

52-6 

26-6 

336 

'045 

6 

9-0 

4-9 

51 

1-285 

32 

57'0 

28-5 

366 

•060 

8 

12  -O 

6-5 

69 

I-308 

34 

6l'6 

3°7 

402 

•075 

10 

IS'O 

8-1 

87 

1-332 

36 

66-4 

327 

436 

•091 

12 

I9'2 

9-8 

107 

1-357 

38 

71-4 

34-8 

472 

•108 

14 

21  '6 

ii  -6 

129 

I-383 

40 

76-6 

37  -o 

SI2 

•125 

16 

25-0 

I3-3 

ISO 

1-410 

42 

82-0 

39-3 

554 

•142 

18 

28-4 

15-0 

171 

•438 

44 

87-6 

41-7 

600 

•162 

20 

32-4 

17-0 

198 

•468 

46 

93'6 

44  -o 

646 

•180 

22 

36-0 

18-8 

222 

•498 

48 

99-6 

46-5 

697 

•200 

24 

40  -o 

207 

248 

•530 

50 

io6-o 

48-9 

748 

•220 

26 

44  -o 

22-5 

275 

•563 

52 

II2-O 

SI'S 

802 

Caustic  potash  (potassium  hydrate,  KOH)  is  at  present  obtained  on  the  large  scale. 
The  chief  method  consists  in  lixiviating  potassium  carbonate  (as  obtained  from  potassium 
chloride  by  the  Leblanc  process)  in  the  state  of  crude  potash  (i.e.,  mixed  with  calcium 
sulphate  and  hydrate  as  it  comes  from  the  calcining  furnace)  with  water  and  causticising 
by  treatment  with  lime.  It  is  more  advantageous — i.e.,  an  economy  of  time  and 
materials — if  the  coal  added  to  the  mixture  of  potassium  sulphate  and  limestone  is  used 
in  a  larger  proportion,  if  the  smelting  is  protracted,  and  if  the  crude  potash  obtained  is 
at  once  lixiviated  with  water  at  50°.  Thereby  the  subsequent  causticising  with  lime  is 
avoided.  The  lye  is  evaporated  to  dryness  in  pans,  scooping  out  the  foreign  salts  as 
they  separate. 

Table  of  the  Specific  Gravity  of  Potash  Lye  at  15°. 


Specific 
Grevity. 

Baume. 

Twaddell. 

ioo  parts 
contain 
KOH. 

i  cubic  metre 
contains 
kilos.  KOH. 

Specific 
Gravity. 

Baumd. 

Twaddell. 

ioo  parts 
contain 
KOH. 

i  cubic  metre 
contains 
kilos.  KOH 

•014 

2* 

2-8° 

17 

17 

I  '220 

26° 

44-0° 

24-2 

295 

•029 

4 

5-8 

3'5 

36 

1-241 

28 

48-2 

26'! 

324 

•045 

6 

9-0 

5'6 

58 

1-263 

30 

52-6 

28-0 

353 

•060 

8 

12  -O 

7-4 

78 

1-285 

32 

57'° 

29-8 

385 

•075 

10 

IS-0 

9-2 

99 

1-308 

34 

61-6 

31-8 

416 

•091 

12 

18-2 

10-9 

119 

I-332 

36 

66-4 

337 

449 

•108 

H 

21-6 

12-9 

143 

1-357 

38 

71-4 

35'9 

487 

•125 

16 

25-0 

14-8 

167 

I-383 

40 

76-6 

37-8 

522 

•142 

18 

28-4 

16-5 

1  88 

I'4IO 

42 

82-0 

39*9 

563 

•162 

20 

32-4 

28-6 

216 

I-438 

44 

87-6 

42-1 

605 

•180 

22 

36-0 

20-5 

242 

1.468 

46 

93'6 

44-6 

655 

.200 

24 

40-0 

22-4 

269 

1-498 

48 

99-6 

47  'i 

706 

Statistics. —  The  yearly  production  of  potash  according  to  H.  Griineberg  is — 

Wood-ashes. — Russia,  Canada,   U.S.   of  North   America,  Hungary,  and 

Galicia   ............  20,000  tons 

Beet-sugar  ash. — France,  Belgium,  Germany 12,000    „ 

Mineral  potash. — Germany,  France,  England 15,000    „ 

Suint. — Germany,  France,  Belgium,  Austria 1,000    „ 


48,000    „ 

These  conditions  differ  strikingly  from  those  which  existed  thirty  years  ago,  when 
wood-ash  was  in  exclusive  use  and  Russian  potash  ruled  the  market.  The  potash  ex- 
tracted from  wood-ashes  scarcely  amounts  to  one-half  of  the  total  production  ;  it 
decreases  year  by  year,  and  the  time  when  it  will  disappear  from  the  market  seems 
within  measurable  distance.  It  is  being  superseded  by  beet  potash,  which  is  a  bye- 
product  of  the  beet-sugar  manufacture,  and  hence  can  be  offered  at  lower  prices.  Of 


3oo  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

greater  importance  is  the  manufacture  of  potash  from  potassium  sulphate,  based  on  the 
resources  of  the  Stassfurt  salt-beds.  The  centre  of  production  of  beet  potash  is  in  the 
north  of  France,  that  of  mineral  potash  in  Northern  Germany,  which  is  now  the 
greatest  potash-producing  country  in  the  world.* 

Alkalimetry. — Commercial  potash  is  commonly  a  mixture  of  caustic  potash  with 
potassium  carbonate  and  other  potassium  and  sodium  salts  (as  soda  itself  is  a  mixture 
of  sodium  carbonate  with  foreign  salts,  especially  sulphate  and  chloride).  In  order 
easily  and  quickly  to  ascertain  the  proportion  of  pure  potassium  carbonate  in  a  sample 
of  potash  with  an  accuracy  sufficient  for  technical  purposes  there  are  two  methods, 
namely — 

(a)  To  determine  the  quantity  of  acid  required  to  neutralise  the  potassium 
carbonate ; 

(6)  To  find  the  quantity  of  carbonic  acid  which  can  be  expelled  from  potash  by  the 
addition  of  a  stronger  acid. 

Both  methods,  of  course,  are  applicable  only  if  besides  the  alkaline  carbonate  no 
other  carbonates  are  present  in  the  potash.  All  procedures  for  determining  the 
potassium  carbonate  in  a  sample  of  potash  are  called  potassimetric  methods.  The 
methods  of  testing  potash  and  soda  (sodametric)  are  included  under  the  common  name 
alkalimetric. 

As  a  normal  solution  Mohr  uses  crystalline  oxalic  acid  (CjH204.2H2O=  126) ;  63 
grammes  oxalic  acid  (  =  \  mol.)  are  dissolved  in  water  and  made  up  exactly  to  \  litre. 
To  this  acid  solution  there  corresponds  a  second,  a  solution  of  caustic  potassa  (KOH). 
It  is  so  adjusted  that  on  mixture  with  an  equal  volume  of  the  oxalic  acid  solution  the 
last  drop  of  the  potassium  solution  turns  the  colour  of  the  litmus  solution  added  from 
red  to  blue  which  can  always  be  effected  by  a  single  drop  if  the  solution  is  free  from 
carbonic  acid.  For  testing  alkali  -fa  mol.  in  grammes  of  the  anhydrous  ignited  sample  is 
weighed  off,  containing,  therefore,  6-911  grammes  potash  or  5-32  soda.  As  the  standard 
acid  contains  in  1000  c.c.  \  mol.  oxalic  acid,  100  c.c.  of  this  liquid  will  saturate 
exactly  ^  mol.  of  the  alkali.  The  potash  along  with  a  solution  of  litmus  is  placed 
in  a  small  boiling  flask  and  a  little  of  the  acid  is  run  in,  which  decomposes  the  potash 
with  effervescence.  The  colour  passes  from  blue  to  violet  and  the  effervescence 
becomes  slighter.  The  liquid  is  raised  to  a  boil  and  more  acid  is  dropped  in  until  the 
colour  becomes  a  full  onion-red.  Test  acid  is  then  run  in  excess.  The  alkali  is  now 
super-saturated,  and  the  carbonic  acid  is  expelled  by  boiling.  The  point  of  saturation 
of  the  alkali  is  now  overstepped  5  or  6  c.c.  A  pipette  graduated  in  ^  c.c.  is  filled 
up  to  o  with  the  standard  caustic  potash,  and  it  is  allowed  to  fall  drop  by  drop  into  the 
liquid  solution  of  the  sample  under  examination,  keeping  it  agitated.  The  colour  passes 
from  red  to  violet  and  then  suddenly  into  a  clear  blue.  The  number  of  c.c.  of  the 
alkaline  solution  consumed  is  read  off,  and  deducted  from  the  c.c.  of  test  acid  consumed ; 
the  remainder  shows  pure  potassium  carbonate  3-45  grammes  =  ^  mo),  potash  used, 
e.g.,  36  c.c.  of  test  acid  and  3  c.c.  of  test  alkali  =  33  c.c.  of  test  acid  =  66  per  cent,  of 
potassium  carbonate  (as  instead  of  ^  mol.  only  -^  mol.  was  used,  whence  the  c.c.  of 
the  acid  must  be  doubled  to  obtain  per  cents.).  Latterly,  instead  of  litmus,  cyanine, 
fluoresceine,  phenolphthaleine,  tropaeoleine  ooo,  and  phenacetaline  have  been  proposed 
for  alkalimetric  and  acidimetric  indicators. 

Fresenius  and  Will  decompose  potash  with  sulphuric  acid  and  determine  the 
amount  of  carbonic  acid  by  the  loss  of  weight. 

Commercial  Value. — As  potash  is  very  hygroscopic,  in  order  to  determine  its 
commercial  value  it  is  by  no  means  sufficient  to  state  how  much  potassium  carbonate  is 

*  It  must  not  be  forgotten  that  beet  potash  can  be  continually  obtained  only  by  either  gradually 
exhausting  the  soil  of  a  necessary  constituent  of  plant-food,  or  by  continually  using  potash  manure. 
Hence  the  beet-potash  industry  could  not  exist  alone. 


SECT,  m.]  POTASSIUM  SALTS.  301 

present ;  this  statement  must  be  referred  to  anhydrous  potash,  and  we  must  know  how 
much  water  is  present.  In  order  to  ascertain  the  quantity  of  water,  a  weighed 
quantity  of  the  sample,  e.g.,  10  grammes,  is  heated  until  all  water  is  expelled,  for 
which  five  minutes  are  generally  sufficient.  The  loss  of  weight  expressed  in  decigrammes 
shows  the  amount  of  water  per  cent.  Of  the  potash  thus  dried,  6*23  grammes  are 
weighed  out  and  treated  as  above.  As  6^29  grammes  potash  and  4*84  grammes  soda,  if 
they  were  pure  carbonates,  would  exactly  contain  2  grammes  carbonic  acid,  every  2  centi- 
grammes of  loss  signify  i  per  cent,  of  carbonate.  If  the  loss  of  weight  of  the  apparatus 
on  testing  a  potash  was  1*64  (=  164  centigrammes)  the  potash  would  contain  i|±  = 
82  per  cent,  of  potassium  carbonate. 

According  to  H.  Will  and  R.  Fresenius,  the  statement  of  the  percentage  of  potash 
should  refer  to  the  anhydrous  condition.  This  percentage  is  expressed  by  the  constant 
numerator  of  a  fraction,  whilst  the  varying  proportion  of  water  is  shown  by  a  varying 
denominator.  If,  e.g.,  we  wish  to  express  that  a  potash  in  its  anhydrous  condition 
contains  60  per  cent,  potassium  carbonate,  we  should  write  -j-6^ ;  if  the  sample  absorbed 
so  much  moisture  that  100  kilos,  increased  in  weight  to  105  or  109,  we  should  write 
T£S  or  TtrV-  According  to  this  system,  the  price  of  the  product  would  be  fixed  by  the 
manufacturer  in  its  anhydrous  state,  and  the  contents  of  the  article  would  be  designated 
by  a  fraction  in  such  a  manner  that  the  numerator  shows  the  proportion  of  potassium 
carbonate,  whilst  the  denominator  100  shows  the  absence  of  water.  For  instance, 
potash  at  T^  is  worth,  say,  305.  The  denominator  augmented  by  the  increase  of 
water  informs  the  buyer  then  how  much  of  the  hydrated  article  should  be  supplied 
for  the  same  price.  Thus  106  or  109  kilos,  of  the  damp  potash  ought  to  be  supplied 
at  305. 

The  proportion  of  soda  is  generally  expressed  in  "  degrees."  The  French  degrees 
are  per  cents,  of  sodium  carbonate,  whilst  the  English  degrees  are  sodium  oxide  (caustic 
soda,  Na20).  As  sodium  carbonate  consists  of  58-6  parts  soda  and  41-4  parts  carbonic 
acid  in  100  parts, 

80°  French  =  46-9  English 

86°        „      =  50-5 

96°        „       =  52-8        „ 

G.  Lunge  (Dingler's  Journal)  points  out  that  the  degrees  used  in  the  English  soda 
trade  only  exceptionally  show  the  percentage  "real  soda,"  Na20,  as  the  molecular 
weight  of  sodium  carbonate  is  taken  at  54  instead  of  53.  Chemically  pure  sodium 
carbonate  is  consequently  made  to  show  59^26  Na20  instead  of  58*49  per  cent,  (i.e., 
077  per  cent,  too  much).  In  Lancashire  they  go  still  further,  and  put  for  53  Na20, 
54  "real  soda,"  e.g.,  51 '6  per  cent,  instead  of  50  per  cent.  Even  with  this  the  trade 
was  not  satisfied,  for  on  checking  the  results  of  certain  Liverpool  commercial  chemists 
the  returns,  especially  for  caustic  soda,  were  often  found  2°  to  3°  too  high.  A  soda  of 
58°,  "  Liverpool  test,"  corresponds,  therefore,  not,  as  it  ought,  to  99-16  per  cent.  Na,C03, 
but  to  scarcely  more  than  96  per  cent. 

The  processes  for  the  determination  of  alkali  given  above  have  grave  defecj.o,  as 
they  overlook  soda  contained  in  samples  of  potash  and  treat  summarily  the  quantities  of 
potassium  salts.  For  the  technicist  they  differ  considerably  in  value ;  the  carbonate  is 
worth  more  than  the  chloride  and  the  latter  less  than  the  sulphate.  A  complete 
analysis  is  necessary  for  ascertaining  the  value  of  potassium  salts. 


302  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

COMMON  SALT  AND  SALT  WORKS. 
Occurrence. — Common  salt,  or  chloride  of  sodium,  consists  of — 

Chlorine,  Cl    .        .        .        .         35*5         ...         60*41 
Sodium,  Na     .        .         .         .         23-0         ...         39-59 


58*5        ...       loo'oo 

and  is  found  on  our  globe  in  the  solid  state  as  rock-salt,  as  well  as  dissolved  in  sea- water 
in  enormously  large  quantities.  It  occurs  as  rock-salt  in  extensive  layers,  alternating  with 
strata  of  clay  and  gypsum,  at  an  average  depth  of  100  metres.  The  following  are  a  few 
of  the  localities  where  rock-salt  is  met  with  in  the  tertiary  formation : — Wieliczka, 
Poland ;  the  northern  slopes  of  the  Carpathian  mountains,  and  in  several  districts  of 
Hungary ;  in  the  chalk  formation  of  Cardona,  Spain ;  in  the  Eastern  Alps,  Bavaria, 
Salzburg,  Styria,  and  the  Tyrol.  Among  the  trias  formation  are  the  salt  deposits  of 
the  Teutoburg-wood,  Germany,  and  a  great  many  others,  among  them  the  celebrated 
Stassfurt  deposits.  In  England,  rock-salt  is  found  in  Cheshire,  this  county  being  also 
plentifully  supplied  with  saline  springs,  the  water  of  which  yields  on  evaporation  an 
abundance  of  salt.  Petroleum  wells  are  found  with  salt  in  many  parts  of  Asiatic 
Russia,  in  Syria,  Persia,  and  the  slopes  of  the  Himalayas.  Salt  occurs  plentifully  in 
several  districts  of  Africa,  America,  and  other  parts  of  the  world,  and  mixed  with  clay 
and  marl,  forming  salt-clay.  Salt  occurs  secondarily  by  having  been  dissolved,  at  a 
depth  varying  in  Germany  from  91  to  555  metres,  by  water,  which  carries  it  again  to 
the  surface,  there  forming  salt  springs  and  salt  lakes,  from  which  the  salt  is  obtained 
by  evaporation.  Among  the  salt  lakes  may  be  noticed  the  lake  near  Eisleben, 
Germany ;  the  Elton  Lake  near  the  Wolga,  Russia ;  the  Dead  Sea ;  and  the  Salt  Lake  of 
Utah,  United  States. 

There  can  be  no  doubt  that  the  common  salt  met  with  in  salt  springs  owes  its  origin 
to  the  solvent  action  of  water  upon  rock-salt ;  and  as  rock-salt  is  largely  met  with  in 
sedimentary  geological  formations,  the  prevalence  of  this  formation  in  Germany  has 
there  given  rise  to  a  large  number  of  salt  springs.  Common  salt  is  also  found  in  sea- 
water,  and  if  obtained  by  its  evaporation  is  often  termed  sea-salt ;  or  if  deposited,  as  is 
the  case  in  the  Polar  regions,  by  intense  cold  on  the  surface  of  ice-fields,  it  is  known  as 
rassol.  Common  salt  is  largely  obtained  as  a  bye-product  of  some  chemical  operations, 
as  in  the  conversion  of  sodium-nitrate  into  potassium-nitrate  by  the  aid  of  potassium 
chloride. 

Method  of  Preparing  Common  Salt  from  Sea  Water.— The  constituent  salts  of 
sea- water  do  not  differ  in  any  part  of  the  world  ;  even  the  difference  in  quantity  is  very 
small,  and  is  generally  due  to  local  causes,  as  the  dilution  of  the  sea-water  by  river- 
water,  melting  icebergs,  &c.  The  specific  gravity  of  sea- water,  at  17°,  varies  from 
1-0269  to  1-0289,  the  specific  gravity  of  the  water  of  the  Red  Sea  being  as  high  as 
1-0306.  One  hundred  parts  of  sea- water  contain — 

Pacific  Atlantic  German  Wo A  Con 

Ocean.  Ocean.  Ocean.  sea< 

Sodium  chloride  .         .         .         2.5877  ...  27558  ...  2-5513  ...  3-030 

„        bromide           .        .         0-0401  ...  0-0326  ...  0-0373  ...  0-064 

Potassium  sulphate      .        .        0-1359  ...  0-1715  ...  0-1529  ...  0-295 

Calcium  sulphate          .        .        0-1622  ...  0-2046  ...  0-1622  ...  0-179 

Magnesium  sulphate    .        .        0-1104  —  0-0614  ...  0-0706  ...  0-274 

„           chloride     .        .        0-4345  ...  0.3260  ...  0-4641  ...  0-404 

Potassium                                         _  _  _  o.288 


3-4708        ...        3-5519        ...        3-4384        ...        4-534 

The  composition  of  the  salt  contained  in  the  water  of  the  several  seas  is  shown  by 
the  following  table  : — 


SECT.    III.] 


COMMON   SALT   AND   SALT   WORKS. 


3°3 


Caspian 
Sea. 

Black  Sea. 

Baltic.* 

English 
Channel. 
Average 
of  7  locali- 
ties. 

Mediterra- 
nean. 
Average 
of  3  locali- 
ties. 

Atlantic 
Ocean. 
Average  of 
3  locali- 
ties. 

Dead  Sea. 
Average  of 
5  locali- 
ties. 

Average     quantity      of      salt 

and  water  — 

Solid  salt 

0-63 

177 

177 

3'3i 

3*37 

3^3 

22-30 

Water        .... 

99-37 

98-23 

98-23 

96-69 

96-63 

96-37 

7770 

The    dissolved     solid     matter 

consists  in  100  parts  of  — 

Sodium  chloride 

58-25 

79-39 

84-70 

78-04 

77-07 

77-03 

36-S5 

Potassium      „            .        . 

I'27 

1-07 

— 

2-09 

2-48 

3^9 

4-57 

Calcium         „            . 

— 

— 

0'20 

— 

II-38 

Magnesium    „ 

lO'OO 

7^58 

973 

8-81 

876 

7-86 

45-20 

Sodium  and  magne-  { 
sium  bromides     .  | 

— 

0-03 

— 

0-28 

0-49 

1-30 

0-85 

Calcium  sulphate 

778 

0-60 

0-13 

3-82 

276 

4^3 

0'45 

Magnesium   ,, 

19-68 

8-32 

4-96 

6-58 

8-34 

5-29 

Calcium  and  magne-  ) 
sium  carbonates     j 

3  '02 

3-21 

0-48 

0-18 

O'lO 

— 

Nitrogenous  and  bi-  ) 

I»f\f\ 

tuminous  matter  J 

MU 

One  cubic  metre  (35*3165  cubic  feet)  of  sea-water  contains  consequently  about  28 
to  31  kilos,  of  sodium  chloride  and  5  to  6  kilos,  of  potassium  chloride.  Sodium  chloride 
(common  salt)  is  obtained  from  sea-water  : — 

a.  By  the  evaporation  of  the  water  by  the  aid  of  the  sun's  heat. 

b.  In  winter,  by  freezing. 

c.  By  artifical  evaporation. 

Method  of  Obtaining  Common  Salt  in  Salines. — This  method  of  obtaining 
common  salt  from  sea-water  is  limited  to  certain  of  the  coast-lines  of  Southern  Europe, 
and  is  never  effected  beyond  48°  N.  latitude.  The  countries  best  situated  for  this  in- 
dustry are  France,  Portugal,  Spain,  and  the  coasts  of  the  Mediterranean.  The 
arrangement  of  the  salines,  or  salt-gardens,  is  the  following  : — On  a  level  sea-shore  is 
constructed  a  large  reservoir,  which,  by  a  short  canal,  communicates  with  the  sea,  care 
being  taken  to  afford  protection  against  the  inroads  of  high  tides.  The  depth  of  water 
in  these  reservoirs  varies  from  0*3  metre  to  2  metres.  The  sea-water  is  kept  in  the 
reservoir  until  the  suspended  matter  has  been  deposited,  and  is  then  conveyed  by  a 
wooden  channel  into  smaller  reservoirs,  from  which  it  is  conducted  by  underground 
pipes  to  ditches  surrounding  the  salines,  where  the  salt  is  separated  from  the  water. 
The  salt  is  collected,  placed  in  heaps  on  the  narrow  strips  of  land  which  separate  the 
ditches  from  each  other,  and  sheltered  from  rain  by  a  covering  of  straw.  As  these 
heaps  are  left  for  some  time,  the  deliquescent  magnesium  and  calcium  chlorides  are 
absorbed  in  the  soil ;  consequently,  the  salt  is  comparatively  pure.  The  mother-liquor 
is  used  in  the  production  of  potassium  chloride,  sodium  sulphate,  and  magnesium  salts, 
the  process  employed  being  that  originally  suggested  by  Professor  Balard,  and  after- 
wards improved  by  Merle. 

By  Freezing. — This  process  is  based  upon  the  fact  that  when  a  solution  of  common 
salt  is  cooled  to  several  degrees  below  the  freezing-point,  it  is  split  up  into  pure  water, 
which  freezes,  and  a  strong  brine.  The  solution  becomes  more  concentrated  by 
repeated  freezing  and  removal  of  the  ice,  until  at  last  a  solution  is  obtained  which 
by  a  slight  evaporation  yields  a  crop  of  salt.  In  order  to  render  the  product  purer, 
some  lime  is  added  to  the  solution  before  evaporation  to  decompose  the  magnesia 
salts. 

*  According  to  the  experiments  of  Baron  Sass,  the  water  of  the  Baltic  from  the  Great  Sound 
between  the  Islands  of  Oesel  and  Moon  only  contains  0*666  per  cent,  of  solid  matter,  and  is  of  a 
sp.  gr.  =  1-00474. 


3o4  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

By  Artificial  Evaporation. — Common  salt  evaporated  from  sea-water  by  the  aid  of 
fuel,  or  sel  ignifere,  is  chiefly  prepared  in  Normandy,  in  the  following  manner : — The 
sand  impregnated  with  salt  is  employed  to  saturate  the  sea-water,  which  is  next 
evaporated.  Very  frequently  an  embankment  of  sand  is  thrown  up  on  the  shore,  so  as 
to  be  covered  at  high  tides  only ;  in  the  interval  between  two  tides  a  portion  of  the  salt 
dries  with  the  sand,  which  in  hot  summer  weather  is  collected  twice  or  three  times 
daily.  The  sand  is  lixiviated  in  wooden  boxes,  the  bottoms  of  which  are  constructed 
of  loose  planks  covered  with  layers  of  straw  ;  the  sand  having  been  put  in  the  boxes, 
sea-water  is  allowed  to  percolate  through  them  till  the  specific  gravity  of  the  water  in- 
creases to  i  •  1 4  or  to  i  •  1 7 ,  the  density  being  observed  by  means  of  three  wax  balls  weighted 
with  lead.  The  salt  boilers  at  Avranchin  consider  that  a  solution  of  brine  of  ri6  sp. 
gr.  is  the  most  suitable  for  evaporation.  The  evaporation  is  carried  on  in  leaden  pans, 
and  during  the  process  the  scum  is  removed  and  fresh  brine  added  until  the  salt  begins 
to  crystallise  out,  when  again  a  small  quantity  of  brine  is  added  to  produce  more  scum, 
which  is  at  once  removed,  and  the  evaporation  continued  to  dryness.  The  salt  thus 
obtained,  a  finely  divided  but  very  impure  material,  is  put  into  a  conical  basket  sus- 
pended over  the  evaporating  pan,  the  object  being  to  remove  by  the  action  of  the  steam 
the  deliquescent  calcium  and  magnesium  chlorides.  The  salt  is  next  transferred  to  a 
warehouse,  the  floor  of  which  is  constructed  of  dry,  well-rammed,  exhausted  sand,  and 
here  it  is  gradually  purified  by  the  loss  of  deliquescent  salts,  the  consequent  decrease 
in  weight  amounting  to  20  to  28  per  cent.  700  to  800  litres  of  brine  yield,  according 
to  the  quantity  of  salt  contained  in  the  sand,  150  to  250  kilos,  of  salt.  A  very  similar 
method  is  in  use  at  Ulverstone,  Lancashire. 

At  Lymington  and  in  the  Isle  of  Wight,  sea-water  is  concentrated  by  spontaneous 
evaporation  to  one-sixth  of  its  original  bulk,  the  brine  being  then  evaporated  by  the 
aid  of  artificial  heat.  In  the  neighbourhood  of  Liverpool,  salt  is  obtained  by  employing 
sea-water  in  refining  crude  rock-salt ;  in  this  way  at  least  2-3  per  cent,  of  common  salt 
results  as  a  bye-product.  During  a  continuation  of  hot  summer  weather  salt  is  de- 
posited from  the  water  of  many  of  the  salt  lakes  in  immense  quantities,  amounting, 
for  instance,  at  the  Elton  Lake,  Russia,  to  twenty  millions  of  kilos. 

Rock-salt. — This  mineral  is  frequently  accompanied  by  anhydrite,  clay,  and  marl, 
and  is  sometimes  found  in  what  are  termed  pockets  of  irregular  shape,  interspersed 
with  clay.  Again,  in  some  cases  saline  deposits  are  separated  by  layers  of  marl. 
With  rock-salt  other  minerals  sometimes  occur,  as,  for  instance,  brongniartine 
(Na,S04  +  CaS04),  near  Villarubia,  in  Spain,  and  the  remarkable  minerals  of  the  salt 
deposit  near  Stassfurt.  Above  the  latter  deposit  is  a  layer,  65  metres  thick,  of  bitter, 
many-coloured,  deliquescent  salts,  consisting  of  55  per  cent,  of  carnallite,  sylvin,  and 
kainite;  25  per  cent,  of  common  salt;  16  per  cent,  of  kieserite ;  and  4  per  cent,  of 
magnesium  chloride.  As  this  saline  layer  contains  12  per  cent,  of  potassa,  it  is  an 
important  deposit  in  an  industrial  sense. 

The  composition  of  rock-salt  is  as  follows': — 

I.  White  rock-salt  from  Wieliczka ;  II.  White,  and  III.  Yellow  rock-salt  from 
Berchtesgaden ;  IV.  From  Hall  in  the  Tyrol ;  V.  Detonating  salt  from  Hallstadt ;  VI. 
From  Schw'abischhall. 

I.  II.  in.  iv.  v.  vi. 

Sodium  chloride  .  .  loo'oo  ...  99-85  ...  99-93  ...  99-43  ...  98-14  ...  99-63 
Potassium  „  .  '..  .  —  ...  —  ...  —  ...  —  ...  traces  ...  0-09 
Calcium  „  .  .  —  ...  traces  ...  —  ...  0-25  ...  —  ...  0*28 

Magnesium  „       .        .        traces     ...      0*15     ...      0-07     ...      o'i2     ,          ...       — 

Calcium  sulphate        .  —        ...       —       ...      —  0-20  1-86  


lOO'OO      lOO'OO      lOO'OO      ICO'OO      lOO'OO      ICO'OO 

The  so-called  detonating  salt,  found  at  Wieliczka  in  crystalline-granular  masses,  has 


SECT.  Ill,] 


COMMON   SALT  AND   SALT   WORKS. 


305 


the  property  when  being  dissolved  in  water  of  giving  rise  to  slight  detonations,  accom- 
panied by  an  evolution  of  hydrocarbon  gas  from  microscopically  small  cells,  the  walls  of 
which,  becoming  thin  when  the  salt  is  dissolved  in  water,  give  way,  and  cause  the 
report.  If  the  solution  of  the  salt  takes  place  naturally  in  the  mine,  the  gas  partlv 
escapes,  and  partly  becomes  condensed,  forming  petroleum,  often  met  with  in  beds  of 
rock-salt.  The  minerals  of  the  salt  deposit  of  Stassfurt  are,  according  to  MM.  Bischof, 
Reichardt,  Zincke,  and  others,  the  following : — 


Chemical  Formula. 

In  ioo  parts  are  contained  : 

Sp.  gr.  of 
the  com- 
pound. 

ioo  parts  of 
water  dissolve 
at  18°  C. 

Synonyms  and 
Observations. 

Anhydrite     . 

CaS04  . 

loo  of  Sulphate  of  lime 

2-968 

O'2O 

Karstenite 

f 

26  82  Magnesia              ] 

Boracite 

B,B030C]2Mg, 

65^57  Boric  acid 
io~6i  Magnesium  chlo-  F 

2'9 

f  Almost    ) 
\  insoluble  j 

Stassfurtite 

( 

ride                    J 

( 

2676  Chloride  of  potas-K 

Carnallite 

1    KMgCl3 
+  6H,0 

sium 
34-50  Magnesium  chlo-  1 
ride 

1-618 

64*5 

f  Contains 
1  Bromine 

( 

3874  Water 

Red  oxide  of 
iron 

Fe20s    .        . 

ioo  of  Oxide  of  iron 

3'35 

Insoluble 

— 

Kieserite 

JMgS04  + 
1     H  O* 

87*10  Sulphate  of  mag-  ] 
nesia 

2-517 

40-9 

Martinsite  ? 

^         tlyU* 

1  2  -90  Water                   j 

( 

45'i8  Sulphate  of  lime  \ 

2CaS04 

19-93  Sulphate  of  mag- 

(  Is  decom-   \ 

Polyhalite     . 

!    MgS04 
1    K2S04 

nesia 
28*90  Sulphate  of  po-    f 

2-720 

j  posed  while 
j    being  dis- 

— 

j    2H20 

tassa 

(      solved       ) 

5  -99  Water                   J 

Rock-salt 

NaCl      . 

ioo  Chloride  of  sodium 

2  '2OO 

36-2 

— 

Sylvin   . 

|   KC1. 

ioo  Chloride  of  potas- 
sium                  J 

2-O25 

34'5 

— 

2  1  '50  Chloride  of  cal- 

CaCl2 

cium 

Tachhydrite  . 

-    2MgCL, 

36-98  Chloride  of  mag-  • 

I-67I 

160-3 

— 

I2H20 

nesium 

41  '52  Water 

36-34  Sulphate  of  po-    •> 

Kainite          . 

K,S04 
MgS04 
MgC)2 
6H2O 

tassa                    1 
25-24  Sulphate  of  mag- 
nesia 
1  8  -95  Magnesium  chlo- 
ride 

— 

— 

f  Contains 
{  Bromine 

19-47  Water 

43-18  Sulphate  of  po-  \ 

Schonite  or 
Pikromerite 

K2S04 

-    MgSO4 
6H20 

tassa 
29-85  Sulphate  of  mag-  - 
nesia                   I 

— 

— 

— 

26-97  Water 

Sylvin  is  also  found  in  large  quantities  in  the  salt  deposit  near  Kalucz,  Galicia. 

Mode  of  Working  Bock-salt. — Rock-salt,  like  other  minerals  and  according  to  its 
mode  of  occurence,  is  either  quarried  or  mined.  If  it  happens,  however,  that  the  rock- 
salt  is  mixed  with  other  minerals,  clay,  gypsum,  dolomite,  &c.,  a  solution  in  water  is 
effected,  which  is  pumped  up  from  the  mine  as  a  concentrated  brine.  In  many 
instances  rock-salt  is  wrought  in  extensive  and  deep  mines,  as  in  the  celebrated  rock- 
salt  mines  of  Wieliczka. 

*  According  to  Rammelsberg  it  is  probable  that  kieserite  is  originally  an  anhydrous  mineral,. 
a  conclusion  which  seems  justified  by  the  variable  quantity  of  water  found  in  different  analyses. 

U 


3o6  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

Mode  of  Working  Salt-springs. — Natural  salt-springs  sometimes  occur,  and  these 
have  been  imitated  artificially  by  boring  to  a  great  depth  into  layers  of  earth  containing 
saline  deposits.  In  this  manner  a  brine  may  be  obtained  sufficiently  concentrated  to 
be  at  once  boiled  down.  The  method  of  working  the  natural  salt-springs  is  to  form  a 
convenient  reservoir  from  which  the  saline  solution  is  immediately  pumped  up  for  the 
purpose  of  being  gradated  (see  p.  168).  The  solution  previous  to  being  boiled  down  is 
left  to  allow  the  suspended  matter  to  settle.  The  salt-springs  obtained  by  boring  either 
yield  a  native  brine,  or  the  borings  are  carried  into  solid  rock-salt  and  water  caused  to 
descend  into  the  salt  deposit.  This  artificial  brine  is  then  pumped  up,  unless  there  is 
naturally  an  artesian  formation.  The  brine  previous  to  further  operations  is  left  for 
some  time  in  reservoirs  to  deposit  suspended  insoluble  matter. 

These  saline  solutions  are  not  always  free  from  impurities ;  in  considering  their 
admixture  brines  may  be  divided  into  two  classes;  the  first  containing  sulphate  of 
magnesium  or  sodium,  with  chloride  of  magnesium  ;  the  other  class  embraces  brine  con- 
taining the  chlorides  of  calcium  and  magnesium.  If  the  brine  happens  to  pass  through 
peaty  soil  or  layers  of  lignite,  there  often  accrues  organic  matter,  humic,  crenic,  and 
apocrenic  acids. 

Preparation  of  Common  Salt  from  Brine. — This  operation  is  duplex  and  con- 
sists in — 

a.  Concentrating  the  brine. 

a.  By  increasing  the  quantity  of  salt. 
/3.  By  decreasing  the  quantity  of  water. 

b.  The  boiling  down  of  the  concentrated  brine. 

Concentrating  the  Brine. — Native  brines  or  salt  springs  seldom  contain  enough 
common  salt  to  make  it  profitable  to  boil  them  down  at  once ;  it  is  consequently 
necessary  to  enrich  the  brine,  and  this  may  be  done  either  (a)  by  dissolving  in  it  rock- 
salt  or  crude  sea  salt,  neither  being  suited  for  culinary  and  many  other  purposes  unless 
refined,  or  (0)  by  decreasing  the  quantity  of  water  without  the  use  of  fuel. 

Enriching  by  Gradation. — The  enriching  or  concentration  of  a  brine  by  decreasing 
the  quantity  of  water  it  contains  is  called  a  gradation  process,  and  may  be  proceeded 
with  by  freezing  off  the  water  in  winter  time,  or  more  generally  by  evaporating  the 
water  by  a  true  gradation  process ;  either — (a)  Gradation  by  the  effect  of  the  sun's  rays ; 
(6)  Table  gradation ;  (c)  Roof  gradation  ;  (d)  Drop  gradation. 

Gradation  by  means  of  the  sun's  rays  is  obviously  the  same  method  of  procedure  as 
that  described  under  the  treatment  of  sea-salt.  Table  gradation  has  been  only  experi- 
mentally tried  at  Reichenhall,  and  consists  simply  in  causing  the  brine  to  flow  slowly 
from  a  reservoir  down  a  series  of  steps,  constructed  so  as  to  give  as  much  surface  as 
possible,  and  thus  hasten  the  evaporation.  Roof  gradation  is  effected  by  utilising  the 
roofs  of  the  large  tanks  containing  the  brine  as  evaporation  surfaces,  by  causing  the 
contents  of  the  tanks  to  flow  in  a  thin  but  constant  stream  over  the  roofs,  which,  of 
course,  are  exposed  to  the  open  air. 

Faggot  Gradation. — This  operation,  also  known  as  drop  gradation,  is  carried  on  by 
means  of  the  following  apparatus,  termed  a  gradation  house,  and  consisting  of  a  frame- 
work of  timber,  fitted  with  faggots  of  the  wood  of  Prunus  spinosa,  which  being  thorny, 
presents  a  large  surface.  The  entire  construction  is  built  over  a  water-tight  wooden 
tank,  which  receives  the  concentrated  brine,  and  frequently  the  top  of  the  gradation 
house  is  provided  with  a  roof.  Under  the  roof  and  above  the  faggots  a  water-tight 
tank  is  placed  containing  the  brine  to  be  gradated;  this  tank  is  provided  with  a 
number  of  taps,  from  which  the  brine  trickles  into  channels  provided  with  holes  to 
admit  of  the  brine  falling  on  the  faggots.  These  taps  are  placed  on  both  sides  of  the 
gradation  house,  and  are  generally  connected  with  levers  to  admit  of  being  readily 
turned  on  and  off  from  below.  The  gradation  process  is  continued  until  the  brine  is 


SECT,  in.]  COMMON   SALT   AND   SALT   WORKS.  307 

sufficiently  concentrated  to  admit  of  being  further  evaporated  by  the  aid  of  fuel  ; 
the  brine  may  be  gradated  to  contain  26  per  cent,  of  salt,  but  the  operation  is  rarely 
carried  so  far. 

The  gradation  process  not  only  serves  the  purpose  of  concentration,  but  also  that  of 
purifying  the  brine,  as  some  of  the  foreign  salts  are  deposited  on  the  faggots  ;  this  de- 
posit of  course  varies  in  composition  according  to  the  constituents  of  the  brine,  but 
chiefly  consisting  of  calcium  carbonate,  with  the  potassium,  sodium,  and  magnesium 
sulphates.  The  deposit  has  in  some  instances  been  used  as  manure.  In  the  tanks  where 
the  gradated  brine  is  collected  another  slimy  deposit  is  gradually  formed,  consisting  of 
gypsum  and  hydrated  oxide  of  iron.  As  in  the  present  day  the  brine  obtained  from 
bored  wells  is  generally  sufficiently  concentrated  to  be  at  once  boiled  down,  gradation 
is  less  frequent,  being  a  very  slow  process  and  involving  a  loss  of  the  salt  carried  off  by 
the  wind. 

Boiling  down  the  Brine. — The  object  is  to  obtain  with  the  least  possible  expendi- 
ture of  fuel  the  largest  quantity  of  pure  dry  salt.  Formerly  the  evaporation  was 
carried  on  in  large  cauldrons,  but  at  the  present  time  evaporating  vessels  are  constructed 
of  well  rivetted  boiler-plate,  the  shape  being  rectangular,  the  length  10  metres,  depth 
o'6  metre,  and  width  from  4  to  6  metres.  These  pans  are  supported  by  masonry, 
which  also  serves  to  separate  the  flues.  Over  the  pans  a  hood  is  fixed  and  connected 
with  a  tube  carried  to  the  outside  of  the  building  to  afford  egress  to  the  steam.  The 
brine,  concentrated  to  contain  from  18  to  26  per  cent,  of  salt,  is  poured  into  the 
pans  to  a  depth  of  0*3  metre. 

The  boiling  down  process  is  in  many  salt  works  conducted  in  two  different 
operations  : — 

a.  The  evaporation  of  water  to  produce  a  brine  saturated  at  the  boiling  point. 

b.  The  boiling  down  of  the  saturated  brine  until  the  salt  crystallises  out. 

The  boiling  down  is  generally  carried  on  for  several  weeks,  the  scum  being  removed, 
together  with  the  gypsum  and  sodium  sulphate  deposited  at  the  bottom  of  the  pan,  with 
perforated  ladles.  As  soon  as  a  crust  of  salt  is  formed  on  the  surface  of  the  liquid,  a 
temperature  of  50°  is  maintained.  At  this  stage  the  salt  is  gradually  deposited  at  the 
bottom  of  the  pan  in  small  crystals,  and  being  removed,  is  put  into  conical  willow 
baskets,  which  are  hung  on  a  wooden  support  over  the  pan  to  admit  of  the  mother- 
liquor  being  returned  to  it.  Finally,  the  salt  is  dried  and  packed  in  casks. 

The  quantity  of  mother-liquor  collected  after  boiling  for  some  two  or  three  weeks 
is,  compared  with  the  quantity  of  brine  evaporated,  very  small ;  it  was  formerly  thrown 
away  or  used  for  baths,  but  is  now  employed  for  the  preparation  of  potassium 
chloride,  the  sodium  and  magnesium  sulphates,  artificial  bitter  water,  and  in  some  in- 
stances for  preparing  bromine.  It  is  evident  that  by  the  boiling  down  all  the  salt 
•contained  in  the  brine  is  not  obtained  as  dry  refined  salt,  a  portion  being  retained 
among  the  early  deposit  formed  at  the  bottom  of  the  pan,  another  portion  remaining 
in  the  mother-liquor,  and  finally  some  loss  accrues  from  the  nature  of  the  operations, 
amounting  generally  from  4  to  9-25  per  cent. 

Properties  of  Common  Salt. — Sodium  chloride  crystallises  in  cubes,  the  size  of 
the  crystals  determining  the  varieties  known  in  the  trade  as  coarse,  medium,  and 
fine  grained  salt,  and  depending  upon  the  rate  of  evaporation  of  the  brine,  a  slow 
evaporation  producing  very  coarse  salt.  Perfectly  pure  common  salt  is  not  hygroscopic, 
but  the  ordinary  salt  of  commerce  contains  small  quantities  of  magnesium  chloride  and 
calcium.  Usually,  salt  contains  from  2*5  to  5-5  per  cent,  of  water,  not  as  a  constituent, 
but  as  an  intermixture  ;  hence  the  phenomenon  called  decrepitation,  due  to  the  breaking 
up  of  the  crystals  by  the  action  of  the  steam  when  salt  is  heated.  Ignited  to  a  strong 
red  heat  sodium  chloride  fuses,  forming  an  oily  liquid,  and  at  a  strong  white  heat 
is  volatilised  without  decomposition.  Common  salt  is  readily  soluble  in  water,  and  is 


3o8 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


one  of  the  few  salts  almost  equally  soluble  in  cold  and  in  hot  water ;  100  parts  of  water 
at  12°  dissolve  35*91  parts  of  common  salt. 

In  order  to  express  the  quantity  of  salt  contained  in  a  brine,  it  is  usual  to  say  the 
brine  is  of  a  particular  fineness,  strength,  or  percentage ;  for  instance,  a  brine  at  1 5 
per  cent,  contains  in  100  parts  by  weight  15  parts  of  salt  and  85  parts  of  water.  The 
Grddigkeit  or  degree  of  a  brine  means  the  quantity  of  water  which  holds  in  solution 

Fig.  281. 


i  part  by  weight  of  salt;  a  brine  of  15-6  GrddigJceit  contains,  therefore,  i  part  by 
weight  of  common  salt  in  15-6  parts  of  water.  The  poundage  (Pfiindiykeit)  of  a  brine 
indicates  in  pounds  the  quantity  of  salt  contained  in  a  cubic  foot  of  brine.  The 
following  table  shows  the  percentage  of  salt  contained  in  brines  of  the  several  specific 
gravities : — 


Salt  per  cent. 

I 


3 

3'5 

4 

4-5 

5 

5-5 

6 

*S 

7 


Sp.  gr. 

Salt  per  cent. 

Sp.  gr. 

Salt  per  cent. 

1-0075 

7'5 

I  -0565 

16 

I  0113 

8 

I  -0603 

17 

1*0151 

8-5        ... 

1-0641 

18 

•0188 

9 

I  -0679 

19 

"O226 

9'5 

1-0716 

I9-5 

'0264 

10 

I  -0754 

20 

•0302 

10-5 

I  -0792 

21 

•0339 

ii 

I  -0829 

22 

•0377 

ii'S 

I  -0867 

23 

-0415 

12 

1-0905 

24 

I  -0452 

13 

I  -0980 

25 

I  "0490 

14 

I-I055 

26-39 

I  -0526 

15 

1-1131 

Sp.  gr. 
I'I2O6 
I-I282 


IT433 
I-I5IO 


1-1675 
I-I758 
I  -1840 
I-I922 
1-2009 
I  -2043 


SECT,  in.]  SODA.  309 

Uses  of  Common  Salt. — It  is  not  necessary  to  enter  into  particulars  on  this  subject. 
Salt  is  used  as  a  necessary  condiment  to  food  ;  a  man  weighing  75  kilos,  contains  in  his 
body  0-5  kilo,  of  common  salt,  and  requires  annually  7-75  kilos,  to  maintain  this  supply. 
Common  salt  is  used  in  agriculture,  and  is  as  necessary  for  cattle  and  horses  as  for  man. 
It  serves  industriaDy  in  the  preparation  of  soda,  chlorine,  sal-ammoniac,  in  tanning,  in 
many  metallurgical  processes,  the  manufacture  of  aluminium  and  sodium.  Further,  it  is 
employed  in  the  glazing  of  the  coarser  kinds  of  pottery  and  earthenware,  from  the  fact 
that  when  common  salt  is  fused  with  a  clay  containing  iron,  the  sodium  is  oxidised  and 
forms  soda,  which,  combining  with  the  alumina  and  silica,  supplies  a  glaze,  while  the 
iron  combining  with  the  chlorine  is  volatilised.  The  uses  of  common  salt  for  the  pre- 
servation of  wood,  for  curing  meat,  preserving  butter,  cheese,  &c.,  are  too  well  known 
to  require  explanation.  Among  the  salt-producing  countries  of  Europe,  England  takes 
the  lead,  producing  annually  32,400,000  cwts.,  while  Germany  only  produces  10,  and 
Russia  20  million  cwts. 

Fig.  281  shows  an  apparatus  used  for  concentrating  brine  from  salt  springs,  &c., 
without  the  use  of  artificial  heat.  It  consists  of  a  stout  frame  work  of  beams,  C, 
supporting  a  system,  B,  of  faggots  of  thorns,  &c.  At  the  bottom  is  a  water-tight  tank 
for  receiving  the  brine. 

In  countries  where  a  tax  upon  salt  still  exists  the  following  substances  are  officially 
added  to  salt  used  for  technical  purposes,  so  as  to  render  it  unfit  for  domestic  uses  :  in 
alkali  works  4  to  1 5  per  cent,  of  soda-ash,  1 2  per  cent,  of  soda  crystals,  sulphuric  acid 
(about  2  percent,  with  3  to  4  parts  of  water),  10  percent,  sodium  bicarbonate,  ammonia, 
5  to  i6|  per  cent.  Glauber  salts.  In  other  chemical  and  in  colour  works :  anilin  colours 
and  decoctions  of  dyes ;  iodine  lye,  mother-liquors  from  extract  of  indigo,  5  per  cent, 
copper  chloride,  f  per  cent,  red  lead,  &c.,  and  a  variety  of  other  products. 

SODA. 

Soda  is  either  (A)  natural  soda,  or  (B)  that  from  plants  and  sea  weeds,  or  (C)  that 
obtained  by  chemical  processes  from  the  sodium  compounds  occurring  in  nature  (such 
as  common  salt,  Glauber  salt,  soda-saltpetre,  cryolite)  with  the  simultaneous  production 
of  hydrochloric  acid,  chloride  of  lime,  sulphur,  sal-ammoniac,  potassium  nitrate,  alum, 
aluminium  sulphate,  sodium  aluminate  and  thio-sulphate. 

(A)  Natural  Soda. 

Soda  occurs  naturally  as  an  ingredient  in  many  mineral  springs,  it  weathers  out 
volcanic  rocks,  e.g.,  trass  and  gneiss,  as  at  Bilinboth,  as  sodium  sesquicarbonate 
NasCO3+ 2NaHC03+ 2H2O,  or  as  sodium  pyrocarbonate,  and  often  exists  in  solution 
in  the  so-called  soda-lakes.  Such  waters  exist  in  Egypt  in  the  western  part  of 
the  Delta,  in  Central  Africa,  in  the  plains  along  the  Caspian,  in  California, 
Mexico,  and  in  some  South  American  States.  In  the  great  Hungarian  plain  crude 
soda  weathers  out  during  the  hot  season  as  a  saline  crust,  which  is  collected  for 
sale.  The  Egyptian  soda  is  known  as  Tro-Na,  whence  the  name  Natron,  still  used  for 
soda  in  Germany.  It  is  exported  yearly  from  Alexandria  to  the  extent  of  5°°°  tons. 
In  Columbia  soda,  called  there  Urao,  is  deposited  in  the  hot  season  at  the  bottom  of  a 
lake  in  the  valley. 

La  Lagunitta. — In  La  Plata  (province  Catamanca)  soda  is  found  in  great  quantities, 
and  is  known  as  Ccollpa.  Quite  recently  an  alleged  inexhaustible  bed  of  natural  soda 
has  been  found  in  Virginia. 

The  sodium  carbonate  of  the  alkaline  lakes  is  probably  formed  on  the  decomposition 
of  common  salt  by  means  of  calcium  or  magnesium  bicarbonate ;  or  it  may  be  produced 
from  sodium  sulphate  which  is  reduced  to  sodium  sulphide  by  the  action  of  organic 


310  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

matter.     The  sulphide  is  then  converted  into  sodium  sesquicarbonate  by  means  of  car- 
bonic acid  dissolved  in  the  water. 

k 

(B)  Soda  from  Plants. 

As  inland  plants  take  up  from  the  alkalies  of  the  soil  principally  potash,  which  is 
found  in  the  ashes  of  such  plants  in  the  state  of  carbonate,  so  plants  growing  on  the 
coast,  in  the  sea  itself,  or  in  salt-steppes,  contain  more  or  less  sodium,  combined  with 
sulphuric  acid  or  with  organic  acids.  Such  plants,  on  incineration  and  lixiviating,  yield 
sodium  carbonate.  Besides  the  species  of  fucus  growing  in  the  sea  itself,  the  genera 
Statice,  Chenopodium,  Mesembryanthemum,  Salsola,  Atriplex,  Salicornia,  &c.,  serve  for 
the  production  of  soda  and  in  some  districts  are  even  cultivated.  The  plants  are 
mown,  the  kinds  of  fucus  are  collected  at  ebb-tide  and  dried  on  the  shore.  The  plants 
are  then  burnt  to  ashes  in  pits.  The  heat  is  so  strong  that  the  ash  melts,  and  on 
cooling  forms  a  hard,  brownish-grey  slag-like  mass  kn'own  as  crude  soda  or  soda-ash. 
It  contains  from  3  to  30  per  cent,  of  sodium  carbonate.  It  is  worked  up  by  lixiviating 
and  concentrating  the  lye.  The  following  kinds  are  distinguished  according  to  their 
origin  and  the  manner  of  their  production  : 

a.  Barilla  soda,  from  Alicante,  Malaga,  Cartagena,  the  Canaries,  &c.     It  is  obtained 
from  the  Barilla  (Salsola  soda)  which  is  cultivated  on  the  coasts  of  Spain.     It  contains 
from  25  to  30  per  cent,  of  sodium  carbonate. 

b.  Salicor  soda,  from  Narbonne,  obtained  by  burning  Salicornia  annua,  a  plant 
which  is  sown  and  reaped  after  the  seed  is  ripe ;  it  yields  about  14  per  cent,  of  sodium 
carbonate. 

c.  Blanquette  soda,  from  Aigues-Mortes,  from  plants  grown  between  Aigues-Mortes 
and  Frontignan,  Salicornia  Europcea,  Salsola  kali,  Statice  limonium,  Artiplex  portu- 
lacoides,  &c.     It  contains  only  from  3  to  8  per  cent,  of  sodium  carbonate. 

d.  Equal  in  value  to  Blanquette  soda  is  Araxes  soda,  much  used  in  South  Russia, 
and  obtained  in  Armenia  in  the  Schurus  direct  on  the  table-lands  of  the  Araxes. 

e.  Still  poorer  is  the  Varec  soda,  Tang  soda,  obtained  in  Normandy  and  Brittany 
from  various  sea-weeds,  especially  the  goemon,  Fucus  vesiculosus. 

f.  About  equal  in  value  to  Varec  soda  is  kelp,  obtained  on  the  western  coasts  of  the 
British  Islands  (Scotland,  Ireland,  Orkneys),  from  various  kinds  of  salsola,  and  sea- 
weeds (Fucus  serratus  and  F.  nodosus,  also  Laminaria  digitata) ;  here  and  there  it  ia 
obtained  from  sea-grass  (Zoster a  maritima). 

g.  Lastly  is  to  be  mentioned  the  soda  derived  from  the  beet,  which  always  contains 
a  few  per  cents,  of  potassium  carbonate. 

(0)  Soda  obtained  by  Chemical  Means. 

The  numerous  attempts  made  at  first  by  French  chemists  to  obtain  from  common  salt 
a  soda  equal  to  barilla  in  cheapness  and  quality  led  to  no  results,  and  the  large- 
rewards  offered  by  the  Academy  of  Sciences  for  the  solution  of  the  problem  were  not 
claimed.  When,  in  consequence  of  the  revolutionary  war  the  importation  of  soda  and 
potash  was  broken  off,  and  when  all  the  potash  which  France  produced  was  required 
for  the  manufacture  of  saltpetre  and  gunpowder,  the  Committee  of  Public  Welfare 
demanded  the  most  accurate  returns  concerning  all  soda  manufactories,  Leblanc  was  one 
of  the  first  manufacturers  to  obey  this  call,  and  he  handed  over  for  the  public  use  the 
principles  on  which  he  was  on  the  point  of  erecting  a  soda-works.  His  process  was 
declared  the  most  suitable,  and  until  the  recent  introduction  of  the  ammonia  process  it 
has  been  in  almost  exclusive  use. 

i.  The  Leblanc  Process. — This  process  consists  essentially  in  the  production  of 
sodium  sulphate,  its  fusion  with  lime  and  coal,  and  the  purification  of  the  crude  soda  ;. 
after  this  follows  the  treatment  of  the  residues. 


SECT.  III.] 


SODA. 


311 


a.  The  production  of  sulphate  (salt-cake)  from  common  salt  is  generally  effected  by 
means  of  chamber  acid,  according  to  the  equation  : 

2NaCl  +  H2S04  =  Na2SO4  +   2HC1. 

The  decomposition  was  at  first  effected  in  open  reverberatories,  so  that  the  hydro- 
chloric acid  escaped  mixed  with  the  gases  of  combustion. 

In  1836  Gossage  obtained  a  patent  for  a  closed  reverberatory,  which  during  the  first 
part  of  the  decomposition  acted  as  a  distilling  apparatus,  and  subsequently,  being 
heated  by  direct  firing,  it  acted  as  an  open  furnace  in  order  to  complete  the  conversion 
of  the  salt  into  salt-cake.  By  combining  this  furnace  with  coke  towers  as  coolers, 
he  succeeded  in  obtaining  in  the  first  section  a  strong  acid  fit  for  the  production  of 
chloride  of  lime,  and  then  a  weaker  acid.  This  furnace  was  decidedly  improved  by 
Gamble  in  1839  ;  at  least  he  seems  to  have  been  the  first  who  caused  the  two  portions 
of  the  decomposition  to  take 

place  in  two  distinct  com-  Fig-  282. 

partments  of  the  furnace 
G  and  E  (Fig.  28;:)-  The 
principle  of  this  furnace 
was  universally  adopted, 
and  for  some  time  the  alkali 
manufacturers  made  use  of 
a  reverberatory  which  by 
opening  or  shutting  an 
aperture  could  be  connected 
with  a  kind  of  muffle,  the 
bottom  of  which  consisted 
of  a  strong  iron  plate.  The 
flame,  after  heating  the  re- 
verberatory, played  round 
the  muffle  and  then  up  the 
chimney.  The  muffle  itself 

was  connected  by  M  with  a  condensing  apparatus  which  yielded  concentrated  hydro- 
chloric acid.  On  this  principle  the  salt  was  let  fall  upon  the  cast-iron  sole  of  the  plate, 
G,  and  the  acid,  previously  heated,  is  allowed  to  flow  in.  A  brisk  reaction  was  set 
up,  and  half,  or  nearly  f  of  the  acid  escaped  and  could  be  easily  condensed,  as  it  was 
not  mixed  with  the  gases  of  the  fire.  The  product  obtained  was  a  mixture  of  sodium 
bisulphate  with  common  salt — 

2NaCl  +  H2S04  =  NaHS04  +  NaCl  +  HC1, 

and  was  drawn  into  the  reverberatory,  E,  whilst  G  received  a  new  charge  of  s^lt  and 
sulphuric  acid.  In  the  reverberatory,  which  was  much  hotter  than  the  muffle,  the 
mixture  of  salt  and  bisulphate  was  converted  into  hydrochloric  acid  and  neutral 
sulphate :  NaHSO4  +  NaCl  =  Na2S04  +  HC1. 

The  hydrochloric  acid  evolved  was  difficult  to  concentrate,  as  it  was  mixed  with 
nitrogen,  carbon  dioxide,  and  carbon  monoxide.  In  spite  of  the  scrubber,  a  part  of  the 
hydrochloric  acid  escaped  into  the  air  and  there  were  required  very  large  apparatus 
and  especial  precautions  in  order  to  effect  a  satisfactory  condensation. 

These  difficulties  are  nearly  overcome  since  the  salt-cake  furnaces  have  been  improved 
as  follows.  The  new  furnace  consists  of  two  muffles,  one  of  iron  and  one  of  brick.  A 
part  of  the  sole  forms  a  shallow  cast-iron  basin  2^74  metre  in  diameter  and  0*52  metre  in 
depth  ;  it  stands  on  a  foundation  of  bricks  and  is  provided  with  a  cast-iron  cover,  which 
is  likewise  a  segment  of  a  sphere  of  0*30  metres  in  depth.  In  this  cover  there  are  two 
apertures  closed  by  doors,  the  one  for  introducing  the  salt,  whilst  the  mixture  is  conveyed 
into  the  brick  muffle  through  the  other.  The  fire  is  at  the  side  of  the  cast-iron  muffle, 


3I2 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


and  its  flame  acts  first  upon  the  cover  and  then  upon  the  basin.  The  brick  muffle  is 
next  to  the  iron  muffle,  and  is  a  chamber  of  9' 14  metres  in  length,  and  274  metres  in 
width.  Beneath  its  brick  sole  there  is  a  series  of  flues ;  its  upper  part  consists  of  a  thin 
vault  of  brick  supporting  a  second  vault,  and  the  flame  circulates  in  the  space  between 
both.  At  one  of  the  sides  of  the  brick  muffle  is  a  fire,  the  flame  of  which  passes  first 
between  the  two  vaults  and  then  through  the  flues  beneath  the  sole.  In  this  manner 
the  heat  passes  through  the  masonry  of  the  vault  and  the  floor  to  the  mixture  of  bisul- 
phate  and  salt  in  the  muffles. 

In  working  with  this  apparatus  500  kilos,  of  salt  are  placed  in  the  iron  muffle,  pre- 
viously heated,  and  the  requisite  quantity  of  acid  at  sp.  gr.  1*7.  The  mass  is 
stirred  up  from  time  to  time.  It  gradually  thickens,  and  in  about  i^  hour  (after  f  of 
the  hydrochloric  acid  have  escaped)  it  is  so  solid  that  it  can  be  removed  into  the  brick 
muffle,  which  is  kept  at  a  bright  red  heat,  so  that  the  hydrochloric  acid  may  entirely 
escape.  There  is  an  arrangement  for  cutting  off  the  connection  between  the  two  muffles, 
so  that  the  gases  escaping  from  either  may  be  received  separately. 

Fig.  283. 


The  salt-cake  furnaces  of  Jones  and  Walsh  are  used  for  sodium  sulphate  at  Aussig, 
as  well  as  in  Britain,  and  by  Yorster  and  Griineberg  at  Cologne  for  potassium  sulphate. 
Opinions  on  them  differ. 

In  the  sulphate  furnaces  of  Mactear  the  salt  and  sulphuric  acid  flow  uninterruptedly 
into  a  pan  formed  by  a  ring-shaped  prominence  in  the  sole  of  the  furnace.  The  mass, 
whilst  still  thin,  flows  over  into  the  part  of  the  hearth  S  (Fig.  283)  situate  nearest  the 
middle,  where  the  decomposition  is  carried  on  about  as  far  as  the  formation  of  bisulphate. 
By  the  position  of  the  agitator  the  mass  is  gradually  brought  towards  the  outside  and 
further  decomposed,  so  that  the  outer  part  of  the  hearth  plays  the  part  of  a  calcining 
furnace.  At  first  Mactear  arranged  the  hearth  of  the  furnace  in  concentric  rings,  but 
he  has  given  up  this  idea.  The  removal  of  the  gases  of  combustion,  which  are  of  course 
mixed  with  the  vapours  of  sulphuric  acid,  is  effected  by  a  cast-iron  pipe  on  each  side 
of  the  agitating  apparatus.  The  vault  is  made  to  descend,  and  the  entire  arrangement 
is  such— as  may  be  seen  from  the  illustration  (Fig.  283)— that  the  agitating  apparatus 
can  suffer  little  from  the  heat.  The  sole  of  the  furnace  is  lined  with  fire-clay  tiles 
which  have  been  boiled  in  tar :  for  mortar  there  is  used  a  cement  which  becomes 
continually  harder  by  the  action  of  the  heat  and  the  sulphate,  so  that  the  entire  sole 
bakes  together  to  a  solid  mass,  which  effectively  resists  the  action  of  the  charge.  The 
heating  is  effected  as  may  be  convenient,  but  of  course  in  such  a  manner  that  no  such 
flame  arises  as  would  choke  the  condensers.  Recently  Mactear  has  made  use  of  four 


SECT,  in.]  SODA.  313 

Wilson  gas-generators,  between  which  and  the  furnace  is  interposed  an  iron  super- 
heating apparatus,  H. 

The  process  of   producing  salt-cake  and  hydrochloric  acid  devised  by  Hargreaves 
and  Robinson  has  been  known  since  1872,  and  is  in  action  on  the  large  scale  in  a  number 
of  English  works.      It  consists  in  the  direct  action  of  sulphurous  acid  (the  gases  from 
roasting  pyrites),  oxygen  (atmospheric),  and  watery  vapour  upon  sodium  chloride — 
S02  +  O  +  H2O  +  2NaCl  =  Na2S04  +  2HC1. 

The  sodium  chloride  gives  the  best  results  when  it  is  very  finely  divided  before  being 
formed  into  lumps.  It  is  moistened  and  dried,  when  it  takes  the  condition  of  hard, 
flat  cakes,  which  are  broken  into  fragments  of  about  38  millimetres  in  diameter.  By 
adding  a  little  sulphate  to  the  water  the  pieces  are  rendered  harder  and  more  suitable. 
The  pieces  of  salt  come  upon  an  iron  grating  placed  near  the  floor  in  cylindrical 
chambers  of  a  fire-proof  material.  They  are  there  treated  at  a  red  heat  with  a  mixture 
of  two  vols.  of  sulphurous  acid,  two  vols.  of  watery  vapour,  and  so  much  air  that  its 
oxygen  may  represent  one  vol.  The  gaseous  mixture  enters  below  the  iron  grating ; 
the  temperature  rises  by  the  heat  of  the  reaction,  so  that  the  gaseous  hydrochloric  acid 
escapes  very  hot ;  it  is  drawn  into  coke  towers  and  there  absorbed  by  water.  The  process 
is  uninterrupted,  and  as  a  rule  eight  cylinders  are  used  simultaneously.  In  place  of  the 
chambers,  a  tower  is  used  built  of  fire-proof  stone  and  provided  at  bottom  with  a 
grating,  through  which  the  gases  enter.  The  pieces  of  salt  are  introduced  from  above 
and  the  salt-cake  as  it  is  formed  is  withdrawn  below.  The  advantages  of  the  Hargreaves 
process  lie  in  the  dispensing  with  sodium  nitrate,  the  production  of  a  sulphate  of  very 
high  grade  (free  from  undecomposed  salt),  decrease  of  the  escape  of  gases,  continuous 
development  and  ready  condensation  of  the  hydrochloric  acid,  reduced  loss  of  sulphur, 
and  consequently  greater  yield.  Its  defects  are,  increased  cost  of  installation,  greater 
consumption  of  fuel,  and  increased  outlay  for  labour. 

Hydrochloric  Acid. — The  liquefaction  of  hydrochloric  acid  by  water  is  effected  the 
more  easily  and  completely  the  less  the  HC1  is  mixed  with  combustion  gases,  &c.,  and 
the  lower  the  temperature  of  the  water ;  one  gramme  of  water  at  the  pressure  of  760 
millimetres  disssolves — 


Temperature.  HGJ. 

o°  ...  0-825  grm. 

4  ...  0-804 

8  ...  0783 

12  ...  0762 

16  ...  0742 

20  ...  0721 


Temperature.  HC1. 

24°  ...  0-700  grm. 

28  ...  0-682 

32  ...  0-665 

36  ...  0-649 

40  ...  0-633 

44  ...  0-618 


The  vapours  of  hydrochloric  acid  are  passed  through  a  number  of  earthenware 
vessels  in  the  opposite  direction  to  the  water,  so  that  the  solution  when  nearly  saturated 
comes  in  contact  with  the  strongest  gases ;  or  the  vapours  are  led  through  towers 
built  of  bricks  soaked  in  tar,  or  stone  plates,  the  filling  of  which  (coke  or  stones)  is  kept 
constantly  moistened  with  water. 

Properties. — Hydrochloric  acid  forms  a  colourless  liquid,  frequently  coloured  yellow 
by  ferric  chloride  or  organic  matter,  and  having  a  pungent  odour.  At  20°  water 
absorbs  475  times  its  own  volume  of  hydrochloric  acid  gas;  the  saturated  solution 
contains  42-85  per  cent,  of  HC1  and  its  sp.  gr.=  i'2i.  According  to  J.  Thomson 
(1874),  hydrochloric  acid  probably  contains  a  hydrate  of  the  composition  HCl.HaO, 
which  must  be  regarded  as  the  true  molecule  of  the  acid.  The  following  table  shows 
th  sp.  gr.  of  hydrochloric  acid  of  different  strengths  and  its  percentage  of  actual 
acid  (at  7°): — 


3*4 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


Specific 
Gravity. 

Degrees 
Iiaum£. 

Degrees 
Twaddell. 

Percentage 
of  Acid. 

Specific 
Gravity. 

Degrees 
Baumd. 

Degrees 
Twaddell. 

Percentage 
of  Acid. 

•21 

26 

42 

42-85 

I  -10 

I4-5 

2O 

2O  '2O 

•2O 

25 

40 

40  '80 

•09 

12 

18 

18-18 

•19 

24 

38 

38-88 

•08 

II 

16 

16-16 

•18 

23 

36 

36-36 

•07 

IO 

H 

14-14 

•17 

22 

34 

34  '34 

•06 

9 

12 

I2T2 

•16 

21 

32 

32-32 

'OS 

8 

10 

lO'IO 

•15 

20 

3° 

30-30 

•04 

6 

8 

8'08 

•14 

!9 

28 

28-28 

•03 

5 

6 

6'06 

•13 

18 

26 

26-26 

•O2 

3 

4 

4-04 

•12 

17 

24 

24-24 

•oi 

2 

2 

2'O2 

•II 

15-5 

22 

21'22 

Fig.  284. 


The  author  remarks  in  a  note  that  Twaddell's  hydrometer  scale,  used  in  England, 
possesses  the  noteworthy  feature  that  the  degrees  coincide  with  tolerable  exactness 
with  the  percentages  of  acid. 

Applications. — The  production  of  a  non-arsenical  hydrochloric  acid  is  easily  effected 
by  distillation  with  ferrous  chloride,  when  the  arsenic— the  more  readily  the  greater  its 
strength — passes  over  in  the  first  portions  of  the  distillate.  An  acid  of  30  to  40  per 
cent,  is  mixed  with  a  little  ferrous  chloride,  the  first  30  per  cent,  which  pass  over  are  set 
aside  as  arseniferous,  and  the  60  per  cent,  which  follow  next,  and  are  pure,  are  collected 
separately.  In  this  manner  an  acid  of  20  to  30  per  cent,  is  obtained.  The  process  s 
adapted  for  the  industrial  production  of  a  non-arsenical  acid,  in  as  far  as  the  crude  acid 
generally  containing  ferric  chloride  needs  merely  to  be  mixed  with  a  few  iron  turnings 
and  submitted  to  fractional  distillation. 

Hydrochloric  acid  is  used  on  a  vast  scale  for  the  production  of  chloride  of  lime, 

potassium  chlorate,  and  other  chlorine  pre- 
parations (e.g.,  chloral  hydrate,  chloroform, 
chlorbenzyl,  benzotrichloride,  methyl  chlo- 
ride) ;  it  serves  also  in  .the  manufacture  of 
sal-ammoniac,  antimony  chloride,  glue,  and 
phosphorus ;  in  the  production  of  carbon  di- 
oxide (for  the  mineral  water  trade) ;  in  the 
manufacture  of  alizarine,  resorcine,  and*  sali- 
cylic acid ;  in  the  preparation  of  sodium 
bicarbonate ;  in  purifying  bone  black  for 

sugar  works ;  in  bleaching  as  a  substitute  for  sulphuric  acid  ;  in  converting  saccharose 
into  a  fermentible  invert-sugar ;  in  working  up  beet  treacle  into  alcohol ;  in  the  produc- 
tion, of  ammonia  and  methyl  chloride  from  the.  dregs  of  beet  treacle :  in  the  metallurgy 
of  copper,  nickel,  cadmium,  zinc,  and  bismuth  ;  for  dissolving  metals  (tin),  either  alone 
or  when  mixed  with  nitric  acid  as  aqua  regia  ;  for  purifying  ferruginous  sands  for  the 
glass  mamifacture ;  for  carbonising  wool.  An  important  use  of  hydrochloric  acid 
occurs  in  the  cotton  manufacture — i.e.,  for  decomposing  the  lime-soap  which  is  formed 
when  cotton  tissues  impregnated  with  fatty  matters  are  bowked  with  lime.  Hydro- 
chloric acid  was  formerly  sold  in  glass  carboys  or  stoneware  jars  (often  of  more  value 
than  their  contents).  Sometimes  it  is  sent  out  in  casks,  lined  with  a  layer  of  gutta 
percha  i  centimetre  in  thickness. 

For  raising  hydrochloric  acid  Kestner  uses  a  stoneware  cylinder,  #,  with  cast-iron 
covers,  T  (Fig.  284),  screwed  together  with  iron  rods.  The  cover,  U,  is  formed  of  vul- 
canite, and  the  valve,  V,  of  caoutchouc.  The  acid  flows  in  by  the  tube,  g,  and  is  forced 
out-wards  through  h ;  the  compressed  air  enters  at  i  and  escapes  during  filling  by  the 
pipe,.?.  An  apparatus  of  this  kind,  holding  50  litres,  lifts  hourly  2500  litres  of  acid  to 
the  height  of  15  metres. 

Sodium  Sulphate,  often  called  simply  sulphate.  (Na2S04.ioH2O),  is  chiefly  formed 


SECT.   III.] 


SODA. 


Fig.  286. 


as  an  intermediate  product  by  the  decomposition  of  common  salt  by  sulphuric  acid  in  the 
Leblanc  process.  It  occurs  naturally  in  the  minerals  thenardite,  Na2SO4,  brogniartin 
or  glauberite,  Na2S04.CaS04,  and  astrakanite,  Na3S04.MgSO4.4H20,  in  many  mineral 
waters,  in  sea-water,  and  in  most  lime  springs.  The  sulphate,  as  it  is  produced  in  the 
alkali  works  as  salt-cake,  contains  on  an  average  93  to  97  percent,  dry  sodium  sulphate, 
and  2  to  3  per  cent,  sodium  chloride. 

Applications. — Sulphate  is  chiefly  used  in  the  manufacture  of  Leblanc  soda,  ultra- 
marine, and  glass.  In  the  last  case  only  the  soda  comes  in  question.  It  is  fused  with 
coal  and  quartz  sand  ;  by  the  action  of  the  fuel  the  sulphuric  acid  of  the  sulphate  is  re- 
duced to  sulphurous  acid  (Na2SO4  +  C  =  CO  +  N2SO3),  which  is  driven  out  by  the  silica, 
and  sodium  silicate  remains.  For  use  in  glass  works  salt-cake  is  previously  purified 
from  iron  by  dissolving 

the    salt,    precipitating  Fig. 

the  iron  oxide  by  means 
of  lime,  evaporating 
down  the  clear  solution, 
and  drying  the  product. 
In  the  same  manner 
water-glass  may  be 
formed  from  the  sul- 
phate by  melting  it  with 
sand  and  carbon,  and  on 
the  same  principle  so- 
dium aluminate  is  ob- 
tained from  the  sulphate 
along  with  bauxite  or 
aluminous  earth.  Con- 
siderable quantities  of 
sulphate  are  also  used 
in  separating  antimony 
from  quartzy  ores — e.g., 
at  Bouc  and  Septemes, 
near  Marseilles.  Lat- 
terly, sulphate  (freed 
from  any  excess  of  acid) 
has  been  used  as  an 
adjunct  in  dyeing,  espe- 
cially for  wool. 

b.  Conversion  ofSul- 
phate  into  Crude  Soda. 
— The  salt-cake  is 
mixed  with  limestone 

(sometimes  hydrated  lime)  and  coal,  and  the  mixture  is  melted  upon  the  hearth  of  a 
reverberatory.  The  proportions  given  by  Leblanc  are :  100  parts  salt-cake,  100  carbonate 
of  lime,  and  50  coal.  In  ten  different  establishments  the  proportion  of  limestone  used 
to  100  parts  of  salt-cake  ranges  from  90  to  121  parts  and  the  coal  from  40  to  75.  The 
lime  of  the  lixiviated  and  desulphurised  vat-waste  is  sometimes  used  as  a  substitute 
for  natural  calcium  carbonate.  In  Britain  reverberatories  with  two  stages  are  often 
used  (Fig.  285).  The  furnace  was  formerly  charged  with  the  materials  ground  and 
mixed.  Now  it  is  preferred  to  use  them  in  fragments,  in  order  that  the  soda  "  balls  " 
may  be  sufficiently  porous  to  admit  of  easy  fracture  and  lixiviation.  In  Germany  the 
furnaces  have  sometimes  only  one  hearth  (Fig.  286).  In  others,  and  in  the  English 


Fig.  287. 


316 


CHEMICAL  TECHNOLOGY. 


[SECT.  HI. 


works,  the  mixture  which  was  prepared  by  the  waste-heat  in  the  upper  stage  remains 
only  for  half  an  hour  on  the  lower  hearth,  which  is  the  working-furnace.  In  German 
alkali  works,  the  mixture,  M,  placed  in  the  hot  reverberatory,  is  heated  until  the  mass  is 
in  a  state  of  pasty  flux,  during  which  it  is  continually  stirred  with  long  iron  rabbles,  K. 
Bubbles  of  carbon  monoxide  burst  out  of  the  mass  and  burn  with  a  blue  flame. 
When  the  flames  disappear  the  mass  is  drawn  out  of  the  furnace  through  the  work- 
ing doors,  P,  into  flat  sheet-iron  chests  on  wheels,  C,  in  which  it  cools. 

As  the  combustion  gases  which  escape  from  the  hearth  of  the  furnace  have  a  very 
high  temperature,  a  second  hearth  is  placed  behind  the  ordinary  one,  which  serves  for  a 
preliminary  heating  of  the  next  charge  whilst  the  first  charge  is  being  completed. 
Fig.  287  shows  such  a  furnace,  with  the  two  hearths,  A  and  J5,  and  there  is  here  a 
third  compartment,  C,  of  the  form  of  a  pan,  in  order  at  the  same  time  to  effect  the  con- 
centration of  the  soda-lye  by  the  hot  gases  as  they  pass  to  the  chimney,  0.  Above  this 
compartment  is  the  pan,  D,  in  which  the  lye  is  concentrated  before  it  is  led  into  C. 

The  author  has  examined  the  temperature  of  the  melted  soda  and  the  composition 
of  the  gases  which  are  evolved.  He  found  :  10  minutes  after  charging,  a  temperatxire 

of  713° ;  20  minutes  after,  15-7  per  cent,  carbon  dioxide,  5-3  oxygen,  temperature 

40  minutes  after,  i8'i  carbon  dioxide,  3*3  oxygen,  temperature  779° ;  55  minutes  after 
a  temperature  of  874° ;  70  minutes  after,  and  shortly  before  drawing  the  melt,  carbon 
dioxide  15-8  per  cent.,  oxygen  6.1,  and  the  temperature  532°.  150  kilos,  salt-cake,  160 

Fig.  288. 


kilos,  limestone,  and  60  kilos,  coal  for  reduction  gave  240  kilos,  crude  black-ash  with 
a  consumption  of  96  kilos,  of  coal.  With  another  quality  of  coal  only  42  kilos,  were 
used  for  heating,  and  the  carbon  dioxide  in  the  gases  rose  to  28  per  cent. 

In  the  furnace  with  a  rotatory  hearth  this  hearth  consists  of  a  cylinder  which  can 
be  turned  on  its  axle.  The  mixture  of  salt-cake,  limestone,  and  coal  is  placed  in  the 
iron  cylinder,  A  (Fig.  288),  lined  within  with  fire-stone.  Two  ribs,  B,  have  been  cast 
upon  it,  by  means  of  which  the  cylinder  rests  upon  two  pairs  of  wheels,  C.  The  one 
pair  is  provided  with  an  axle,  which  communicates  rotation  to  the  wheels  and  from 
them  to  the  cylinder.  The  fire-gases  of  the  furnace,  D,  pass  through  the  opening,  E,  into 
the  cylinder,  then  through  F  into  the  vault,  G  (for  the  pans),  and  through  the  flue,  K,  to 
the  chimney.  After  the  interior  of  the  cylinder  has  been  heated  to  redness  the 
mixture  is  brought  upon  a  truck,  J,  and  introduced  into-  the  cylinder  by  a  hopper,  7/, 
which  is  not  permanently  connected.  After  the  heat  has  acted  for  about  10  minutes 
upon  the  contents  of  the  cylinder,  the  wheels  are  set  in  motion,  and  the  cylinder  is 
allowed  to  make  a  half-rotation.  It  is  then  let  stand  still  for  5  minutes  and  another 
half-turn  is  taken.  The  operation  is  continued  until  the  mass  is  melted,  which  takes 
place  in  about  an  hour.  It  is  then  set  in  rotation  so  as  to  turn  once  every  three  minutes. 


SECT.   III.] 


SODA. 


The  progress  of  the  operation  is  watched  from  time  to  time  by  opening  a  door  placed  in 
the  cylinder.  When  the  process  is  complete  the  melt  is  allowed  to  flow  into  iron  vessels 
placed  below.  The  openings,  B,  B,  serve  for  filling  and  emptying. 

The  rotating  soda-furnace,  or  revolver,  is  an  instance  of  the  widely  felt  need  to  sub- 
stitute mechanical  appliance  for  costly  manual  labour.  The  idea  of  producing  crude  soda 
in  a  rotatory  apparatus  is  due  to  Elliot  and  Russell.  They  experimented  with  several 
furnaces  constructed  at  the  machinery  works  of  Robinson,  Cookes,  and  Co.,  of  St. 
Helens.  The  real  difficulties  were  first  overcome  by  J.  C.  Stephenson,  at  the  works  of 
the  Jarrow  Chemical  Co.,  of  South  Shields.  The  first  revolver  was  supplied  to  the 
company  by  Cookes,  of  St.  Helens,  in  1854,  but  it  was  not  until  1868  that  the  first 
larger  apparatus  was  introduced  by  Gaskell,  Deacon,  and  Co.,  of  Widnes,  and  by  A.  G. 

Fig.  289. 


Kurtz,  of  St.  Helens.  From  that  time  these  apparatus  have  been  introduced  into 
almost  all  British  alkali  works.  The  largest  revolver  hitherto  built  has  been  recently 
erected  by  the  above-named  machinery  works  of  St.  Helens  for  the  Widnes  Alkali  Co., 
of  Widnes.  It  does  the  work  of  18  hand-furnaces,  but  only  takes  up  the  room  of  three 
such.  Its  daily  yield  is  80  to  90  tons  of  black-ash.  The  fire,  F  (Fig.  312),  covers  a  space 
of  5-1  by  3-1  metres,  and  uses  hourly  1-27  tons  of  coal.  The  revolver,  D,  consists  of  a 
wrought-iron  cylinder,  lined  with  fire-stone,  and  provided  with  two  bearing  rings  of 
steel,  which  rest  upon  four  small  wheels.  It  is  set  in  motion  by  two  small  steam  engines 
mutually  connected,  the  movement  being  transferred  by  means  of  toothed  wheels. 
Above  it  are  the  hoppers  t,  and  behind  it  evaporating  pans  for  utilising  the  waste 
heat. 


31g  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

Whilst  the  earlier  revolving  furnaces  of  about  5!  metres  long  work  up  each  time 
4  tons  of  salt-cake  and  require  650  kilos,  of  coal  per  ton,  this  furnace  requires  only 
500  kilos.,  and  yet  the  escaping  gases  suffice  to  concentrate  so  much  lye  of  20  up  to 
50°  Tw.  that  it  can  supply  three  special  caustic  soda  pans,  representing  an  economy  of 
fuel  of  80  tons  weekly.  The  revolving  furnace  is  9  metres  long,  with  an  inside  diameter 
of  3*4  metres,  and  has  three  doors  for  filling  and  emptying.  It  is  lined  with  16,000 
ordinary  fire-stones  and  1 20  weighing  each  63  kilos.  In  seven  days  400  tons  of  salt- 
cake  are  worked  up  to  240  tons  of  a  60  per  cent,  caustic  soda,  with  the  consumption  of 
200  tons  of  coal. 

Crude  soda  (black-ash)  has  approximately  the  following  composition  : — 

Sodium  carbonate 45 

Calcium  sulphide 3° 

Caustic  lime 10 

Calcium  carbonate 5 

Foreign  matter 10 

There  are  sometimes  formed   in   the   black-ash   crystals  of    a  complex   calcium 
sulphide-alumina-lime  silicate,  2CaS.6Ca3Si05.Al3Si05,  as  also  of  the  silicate,  Ca3SiaO7« 
About  5  per  cent,  of  the  sodium  forms  insoluble  compounds. 

Considerable  quantities  of  crude  soda,  especially  in  England,  are  used  without  fur- 
ther treatment  in  soap-making,  in  bleaching,  and  in  the  manufacture  of  bottle-glass. 

c.  Conversion  of  Crude  Soda  into  Purified  Soda,  by  Lixiviation  and  Evaporation. — 
Crude  soda  is  resolved  by  extraction  with  water  into  a  solution  of  sodium  carbonate  and 
an  insoluble  residue  (tank-waste,  vat-waste,  soda-waste,  and  sometimes,  erroneously, 
black-ash  !) 

The  blocks  of  English  crude  soda  are  in  general  of  a  darker  colour  and  richer  in  coal 
than  those  from  Continental  works.  Before  lixiviating  they  are  generally  exposed  to 
the  air  for  one  or  two  days,  in  some  places  ten  to  twelve  days,  not  merely  to  let  them  cool 
but  that  they  may  partially  weather,  thus  rendering  the  subsequent  treatment  more 
easy.  As  J.  Kolb  has  observed,  crude  soda  during  weathering  undergoes  the  following 
changes  : — The  exposure  of  crude  soda  to  a  perfectly  dry  air  does  not,  as  long  as  it 
lasts,  notably  alter  its  composition  ;  if  it  contains,  on  being  burnt,  sodium  sulphide,  it 
may  be  improved  to  a  certain  extent,  as  the  sulphate  passes  into  thiosulphate.  At 
100°  dry  air  seems  also  without  action  upon  crude  soda,  but  as  the  temperature  rises, 
and  especially  if  it  reaches  redness,  the  calcium  sulphide  is  converted  into  calcium 
sulphate,  which  lessens  the  standard  of  the  soda,  since  during  lixiviation  it  enters 
into  double  decomposition  with  sodium  carbonate,  forming  sodium  sulphate.  According 
to  Pelouze,  a  reduction  of  the  strength  is  to  be  seen  even  between  200°  and  300°. 
Hence  it  is  very  important  to  promote  cooling  of  the  soda  after  its  removal  from  the 
furnace,  and  to  effect  this  with  the  exclusion  of  air  in  well-fitting  trucks. 

If  crude  soda  is  exposed  to  moist  air  ammonia  is  evolved  in  consequence  of  the  de- 
composition of  the  sodium  cyanide  which  is  always  present;  the  lime  passes  into 
hydrate,  which  expands  in  volume,  and  produces  clefts  in  the  blocks  of  soda,  which  then 
fall  to  pieces.  The  calcium  hydrate  passes  slowly  into  carbonate,  which  reduces  the 
proportion  of  caustic  soda  in  the  lye.  At  the  same  time  the  sodium  siilphide  (the 
presence  of  which  is  always  indicated  by  red  spots)  is  oxidised  and  becomes  sodium 
thiosulphate.  If  there  were  no  other  reactions  the  exposure  would  be  advantageous, 
but  any  favourable  action  is  neutralised  by  the  oxidation  of  the  calcium  sulphide. 
Moist  air,  like  dry  air,  can,  therefore,  act  favourably  only  in  case  of  soda  which  is 
not  burnt.  If  the  causticity  of  a  well-made  crude  soda  is  diminished  by  exposure, 
this  is  effected  to  the  disadvantage  of  the  proportion  of  alkali,  which  decreases  in  the 
same  degree.  Hence,  the  action  of  air  should,  generally  speaking,  continue  only  long 
enough  for  the  lime  to  be  partially  hydrated,  thus  greatly  facilitating  the  breaking 


SECT.    III.] 


SODA. 


319 


up  of  the  raw  soda.  The  time,  according  to  the  moisture  of  the  air  and  the  pro- 
portion of  free  lime  in  the  soda,  may  vary  from  three  to  six  days.  A  longer  exposure 
is  rarely  without  injury,  and  the  custom  of  leaving  the  balls  in  the  air  for  sometimes 
twelve  days  is  to  be  condemned. 

The  oldest  method  of  lixiviation  consisted  in  grinding  the  crude  soda,  and  stirring 
up  the  sifted  powder  with  4  parts  of  water.  After  the  undissolved  portion  had  settled 
the  solution  was  poured  off  and  brought  into  contact  with  fresh  portions  of  crude  soda, 
repeating  this  process  three  or  four  times.  At  the  same  time  fresh  water  was  poured 
upon  the  undissolved  matter  remaining  in  the  first  vat,  and  was  gradually  transferred 
from  vat  to  vat.  In  this  manner  all  the  soluble  constituents  were  removed  from  the 
crude  soda.  This  method  of  lixiviation  was  open  to  several  objections ;  the  water 
exerted  its  solvent  power  only  on  stirring,  and  hence  the  quantities  dissolved  were  never 
considerable.  It  further  required  much  labour,  and  is,  in  consequence,  no  longer  in  use. 

The  method  of  lixiviation  by  simple  filtration  is  also  not  to  be  recommended,  on  account 
of  the  great  labour  it  requires.  It  consists  in  placing  the  crude  soda  in  sheet-iron  tanks 
provided  with  perforated  false  bottoms,  and  covering  it  with  water.  A  series  of  tanks, 

A,  £,  C,  D  (Fig.  290),  1 1  metre  high,  r8  metre  broad,  and  2  metres  long,  are  set  close 
together  on  a  platform  of  masonry.     At  £  metre  from  the  bottom  is  a  perforated  false 
bottom  of  wood  or  sheet  iron.     A  wooden  main,  K,  placed  above  the  tanks,  and  held 
by  the  irons,  F  and  F',  leads  the  liquid 

into  the  tanks  though  the  plugs,  t,  t',  and  Fig  290. 

t".    In  the  latter  there  are  fixed  below  the 

false  bottom,  the  cocks,  r,  r',  r",  &c.,  which 

serve  to   run   off  the   solution    from  the 

tanks  into  the  channel,  K'.     The  blocks 

of  crude  soda  broken  up  into  fragments 

of  about  the  size  of  a  head,  are  laid  in  the 

false  bottom,  where  they  are  submitted  to 

a  repeated  process  of  lixiviation.     Suppose 

a  system  of  three  tanks,  J,    B,    G,   the 

tank  A  charged  with  fresh  crude  soda,  B 

with  such  as  has  been  once  lixiviated,  and 

C  with  some  that  has  been  twice  lixiviated.     We   let   flow  into  each  through  the 

channel,  K,  the  last  washings  of  a  previous  lixiviation.      These   washings   have   to 

stand  eight  hours  in  each.     After  the  lapse  of  this  time,  the  lye  (which  will  mark 

about  50°  Tw.)  is  let  off  through  the  cock,  r,  into  the  channel,  K,  as  also  the  much 

weaker  lyes  from  B  and  C,  which  are  mixed  in  large  tanks  with  the  lye  from  A,  and 

reduce  its  strength  to  about  40°  Tw.     Washing-waters  are  again  run  in  upon  A  and 

B,  and  into  a  fourth  tank,  Z>,  charged  with  fresh  crude  soda ;  after  eight  hours  the 
lyes  are  run  into  the  cistern,  which  has  already  received  the  lyes  from  the  former 
working,  &c.     It  is  thus  possible  to  obtain  without  interruption  a  lye  of  40°  Tw.     After 
the  contents  of  each  tank  have  thus  been  lixiviated  three  times,  the  residues  are  finally 
washed  with  water  at  50°.     The  liquid  thus  obtained  serves  to  lixiviate  the  soda  in 
the  tanks,  A,  B,  and  C. 

The  lixiviation  apparatus  introduced  by  Clement  Desormes  (Fig.  291)  consists  of  a 
number  of  sheet-iron  tanks  arranged  like  steps.  The  number  of  the  tanks  is  from 
twelve  to  fourteen  (the  figure  gives  only  five,  A,  B,  C,  D,  E).  The  upper  tank,  A,  is  of 
cast  iron,  and  is  twice  the  size  of  the  rest.  By  means  of  bent  iron  pipes,  which  are  fixed 
about  15  centimetres  from  the  bottom,  the  liquid  of  each  tank  can  be  let  off  into  the 
next  lower  one,  from  A  into  B,  from  B  into  <?,  and  so  further.  The  lowest  tank,  E, 
delivers  the  liquid  into  the  settling  cisterns,  F  F',  of  which  there  are  six,  and  which  are 
connected  with  each  other  by  pipes  fixed  about  10  centimetres  below  the  upper  margin. 


320 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


The  crude  soda  to  be  lixiviated,  finely  ground,  is  placed  in  sheet  iron  vessels,  e,  d, 
<fcc.,  perforated  like  sieves.  When  the  lixiviation  is  to  begin  the  tanks  are  filled  with 
hot  water,  two  of  the  sheet-iron  vessels,  each  charged  with  50  kilos,  of  crude  soda,  are 
suspended  in  the  lowest  tank,  E,  by  means  of  a  rod  thrust  through  its  handles ;  after 
from  25  to  30  minutes  they  are  taken  out  and  transferred  to  I),  whilst  two  fresh  ones 
are  placed  in  E,  &c.,  so  that  in  eight  hours,  if  we  have  a  set  of  14  lixiviation  tanks, 
there  are  not  only  in  A  such  soda  vessels  which  have  been  in  all  the  others,  but  two,/", 
have  been  already  taken  out  of  A,  and  are  placed  to  drain  upon  h.  After  thirty 
minutes  the  residue  from  all  these  vessels  is  emptied  into  a  truck  for  removal  from  the 
works,  whilst  e  is  put  to  drain  in  the  place  of/,  d  in  the  place  of  e,  &c.,  and  in  E  there 
are  placed  two  newly  filled  vessels.  Whenever  two  new  vessels  are  thus  placed  in  the 


Fig.  292. 


lowest  tank  there  is  run  into  A  about  twice  as  much  water  as  the  volume  of  the  soda. 
The  water  pushes  out  the  heavier  lye  at  the  bottom,  which  flows  through  the  connect- 
ing-tube into  tank  B,  and  causes  the  heavier  lye  to  flow  over  into  C,  &c.,  so  that 
at  last  an  almost  saturated  solution  flows  from  E  into  the  cistern  F,  where  all  turbid- 
ities settle.  The  temperature  in  the  lixiviating  tanks  must  be  kept  at  from  40°  to 
50°,  not  higher,  as  the  calcium  sulphide  might  undergo  a  decomposition.  The  heat  is 
kept  up  by  means  of  steam  pipes,  which  open  into  the  tanks  at  about  a  third  of  their 
height.  In  the  settling  cistern  also  the  lye  is  heated  by  steam  to  prevent  it  from 

crystallising.  The  suspension  of  the 
soda  in  perforated  vessels  in  the 
lixiviation  tanks  is  the  well-known 
method  by  which  substances  to  be 
dissolved  or  lixiviated  are  placed  at 
the  surface  of  the  solvent,  so  that 
the  more  concentrated  solution  may 
not  accumulate  about  the  bodies  to 
be  dissolved  and  prevent  the  action 
of  the  solvent,  but  may  flow  to  the 
bottom  and  continually  make  room 
for  the  solvent.  If  the  vessels  when 

filled  with  crude  soda  are  of  such  a  magnitude  that  they  cannot  be  raised  by  the  work- 
men, this  is  effected  by  means  of  a  set  of  pulleys. 

Fig.  292  shows  two  lixiviation  tanks  of  a  modified  design.  Each  tank  is  divided 
into  two  compartments  by  a  double  vertical  partition,  which  communicate  with  each 
other  by  the  openings,  a  and  b.  Into  the  space  between  the  two  partitions,  the  steam- 
pipes,  h,  open ;  g  are  the  overflows ;  the  strainers,  12,  of  sheet  iron,  are  provided  at 
their  narrow  ends  with  perforated  strips  that  the  rods  for  lifting  them  may  be  thrust 
through. 


SECT,  in.]  SODA.  321 

According  to  Diirre,  four  tanks  of  wrought  or  cast  iron,  of  about  r6  metre  long, 
i -6  broad,  and  1*65  in  depth,  are  placed  like  terraces.  In  each  of  these  are  put  500 
kilos,  of  crude  soda,  broken  into  four-inch  lumps,  with  the  needful  quantity  of 
water.  The  lixiviation  is  effected  in  twelve  hours,  during  which  the  soda  is  changed 
four  times,  being  placed  after  every  three  hours  in  the  next  higher  lixiviating  tank,  so 
that  in  twelve  hours  the  residuum  is  thrown  out  from  the  top  tank  as  exhausted.  In 
the  two  highest  tanks  the  lixiviation  is  effected  cold,  in  the  third  at  44°,  and  in  the  fourth 
at  56°.  From  the  top  tank  the  lye  passes  straight  into  the  following  one,  and  from  that 
into  a  cistern,  where  it  is  heated  by  steam.  Whilst  in  the  three  upper  tanks  water  is 
added  every  three  hours,  from  the  lowest  tank  the  lye  flows  off  into  a  larger  cistern  at  the 
suitable  concentration,  38°  Tw.  Four  such  series  of  tanks  with  their  accessory  heating 
vessels  form  a  system. 

The  so-called  Shanks — more  correctly  Buff-Dunlop — lixiviation  apparatus  utilises 
the  fact  that  a  solution  becomes  the  heavier  the  more  salts  it  holds  in  solution,  and 
that  a  column  of  a  weak  lye  may  be  counterpoised  by  a  shorter  column  of  stronger 
lye.  On  this  principle  the  tanks,  four  to  eight  in  number  (Fig.  293),  stand  side  by  side 
horizontally.  Water  runs  through  them,  and  as  it  passes  it  lixiviates  the  soda  and 
becomes  denser  from  tank  to 

tank,  from  the  first,  which  con-  Fig.  293. 

tains  clear  water,  to  the  last, 
from  which  saturated  soda  lye 
runs  off.  Although  the  vats 
stand  in  a  horizontal  plane, 
the  level  of  the  liquids  forms 
steps.  Each  is  provided  with 
a  false  bottom,  F,  of  perforated 
sheet  metal .  From  the  bottom 
of  each  there  passes  a  tube,  T, 
open  at  both  ends,  its  lower 
aperture  being  cut  diagonally 
up  to  the  surface,  and  supports 

laterally  a  short  tube,  t,  which,  as  will  be  seen  from  the  figure,  connects  one  tube  with 
the  next.  The  main,  r,  fitted  with  cocks,  supplies  each  tank  with  water.  Four 
washings  suffice  as  a  rule.  One  tank  contains  crude  soda  which  has  undergone  three 
lixiviations,  and  therefore  only  a  small  quantity  of  soluble  salts.  This  vat  (I.) 
contains  therefore  washing  water,  which  after  it  has  taken  up  everything  soluble 
from  the  soda  enters  tank  (II.),  which  has  only  been  lixiviated  twice ;  the  lye  then 
passes  into  tank  (III.),  the  contents  of  which  have  only  been  washed  once ;  and,  lastly, 
into  tank  (IV.)  charged  with  fresh  soda. 

From  here  the  lye  travels  to  the  collecting  cistern.  Tank  (I.)  is  charged  with 
crude  soda,  and  the  track  of  the  lye  is  modified  as  required  by  means  of  the  plugs 
placed  in  the  apertures  of  the  pipes.  This  arrangement  allows  the  workman  to  seek 
out  two  contiguous  vats,  and  to  take  the  one  as  the  entrance-  and  the  other  as  the 
exit-vat.  As  the  vats  are  alternately  filled  and  emptied,  the  one  which  has  been 
last  charged  contains  the  richest  mass  and  the  most  saturated  lye,  which  is  densest, 
and  stands  lowest ;  consequently  this  vat  is  the  exit-vat  for  the  new  series,  from 
which  the  saturated  lye  is  drawn.  On  the  other  hand,  the  tank  in  which  the 
mass  is  most  exhausted  contains  the  weakest  lye,  which  has  the  highest  level.  This 
tank  serves  as  the  entrance  vessel  for  pure  water.  As  soon  the  charge  in  this  tank 
is  completely  exhausted  it  is  removed  and  replaced  by  a  new  charge ;  by  opening  a 
series  of  cocks,  this  tank  is  made  the  exit-tank.  At  the  same  time  the  current  of 

x 


?22  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

oold  water  is  led  into  the  adjacent  vat,  &c.  The  more  tanks  a  series  contains  the 
more  readily  a  given  quantity  of  crude  soda  can  be  exhausted  in  a  given  time.  Still 
there  are  practical  limits  which  cannot  be  exceeded,  both  for  the  number  of  the  lixivia- 
tion  tanks  and  for  the  rapidity  of  the  stream  of  water.  It  is  sufficient  if  the  lye  run- 
ning off  has  a  sp.  gr.  of  1-27-1-286,  which  answers  to  a  proportion  of  soda  of  about 
13-5  per  cent,  of  the  weight  of  the  liquid. 

The  advantages  of  this  procedure  are  :  (i)  The  transfer  of  the  crude  soda  from  vat 
to  vat  is  done  away  with,  as  the  charge  remains  in  the  same  vessel  until  it  is  exhausted, 
which  represents  a  considerable  economy  in  labour.  (2)  The  crude  soda  is  always  covered 
by  the  liquid,  so  that  it  never  cakes  together,  as  happened  in  the  old  process,  to  the 
great  hindrance  of  the  lixiviation.  (3)  The  ascending  current  of  the  liquid  carries  off 
the  densest  part  of  the  solution,  so  that  the  lixiviation  is  effected  with  less  water,  in  less 
time,  and  also  more  completely  than  by  a  descending  filtration.  (4)  The  rapidity  and  the 
continuity  of  the  operation  remove  the  alkali  quickly  from  the  action  of  the  insoluble 
calcium  sulphide,  and  abridge  the  duration  of  the  reactions  by  which  soluble  sulphides 
are  formed  to  the  disadvantage  of  the  product.  (5)  The  high  concentration  of  the  lye 
abridges  the  time  of  evaporation  and  thus  effects  an  economy  of  fuel. 

The  nature  of  the  lye  obtained  by  the  lixiviation  of  the  crude  soda  and  its  clarification 
on  standing  depends  on  the  quality  of  the  soda,  the  time  of  the  action  of  air  and  water, 
and  the  temperature  employed.  Dry  crude  soda  contains  no  caustic  soda,  the  presence 
of  which  in  the  lye  depends  on  the  action  of  lime  on  the  sodium  carbonate  in  presence  of 
water.  Sodium  sulphide  occurs  only  in  traces  in  a  normal  crude  soda,  but  its  quantity 
in  the  lye  is  still  more  variable  than  that  of  caustic  soda,  and  depends  on  the  manner 
of  its  lixiviation.  It  is  chiefly  monosulphide  which  is  contained  in  the  lye  :  if  a  poly- 
sulphide  is  present,  it  is  converted  into  monosulphide  by  the  action  of  the  caustic  soda. 
The  quantity  of  water  used  in  lixiviation  has  no  influence  upon  the  causticity  of  the  lye, 
whilst  the  quantity  of  sodium  sulphide  increases  with  the  quantity  of  water,  the  duration 
of  the  digestion,  and  the  increasing  temperature  and  concentration.  This  is  a  consequence 
of  the  increased  solubility  of  calcium  sulphide,  which  in  contact  with  water  is  resolved 
into  calcium  hydrosulphate  and  calcium  hydroxide ;  the  former  compound  yields,  with 
caustic  soda,  sodium  sulphide,  and  this  the  more  readily  the  higher  the  concentration. 
Sodium  carbonate  is  also  decomposed  with  calcium  sulphide,  and  this  the  more  readily 
the  more  dilute  the  solution,  the  higher  the  temperature,  and  the  more  prolonged  the 
action.  The  practical  conclusion  is  that  crude  soda  should  be  lixiviated  rapidly  with 
the  smallest  quantity  of  water  and  at  the  lowest  possible  temperature.  It  would  be  a 
great  improvement  if  an  apparatus  were  invented  which  would  lixiviate  the  soda  in 
a  few  hours  and  with  so  little  water  as  to  yield  at  once  a  concentrated  lye.  Such  lye 
would  be  free  from  sodium  sulphide. 

The  lyes  may  contain  iron  as  sulphide,  as  carbonate,  and  as  sodium  ferro- 
cyanide.  Iron  sulphide  occurs  in  solutions  of  sodium  carbonate  only  if  they  contain 
sodium  sulphide.  The  iron  sulphide  deposits  completely  from  such  solutions  on  prolonged 
standing.  The  deposition  is  not  promoted  by  the  addition  of  sodium  bicarbonate,  as 
is  erroneously  assumed,  but  by  that  of  dense  iron  sulphide,  which  carries  down  that 
in  solution,  or  more  probably  in  fine  suspension.  Iron  occurs  as  carbonate  in  solutions 
which  have  been  freed  from  sodium  sulphide  by  means  of  a  metallic  oxide,  e.g.,  zinc 
oxide,  and  have  been  afterwards  treated  with  carbon  dioxide.  A  solution  of  sodium 
carbonate  containing  bicarbonate  dissolves  iron  oxide  in  considerable  quantity.  The 
solution  is  quite  colourless,  and  does  not  deposit  iron  even  on  long  standing.  An 
addition  of  caustic  soda  quickly  and  completely  removes  iron  from  such  solutions. 

Iron  sometimes  occurs  as  ferric  acid  in  melted  caustic  soda,  but  only  as  a  result  of 
bad  workmanship.  Iron  sulphide  and  sodium  ferrocyanide  are  found  in  crude  soda 
lyes. 


SIXT.  in.]  SODA.  323 

As  an  example  of  the  composition  of  a  crude  lye,  the  analysis  of  a  lye  is  quoted 
obtained  from  the  works  of  Matthes  &  Weber  at  Duisburg.  Sp.  gr.  =  1-25.  i  litre  lye 
•contained  3i3'9  grammes  solid  salts,  consisting  of — 

Sodium  carbonate 71*250  per  cent. 

hydrate       ......  24*500 

chloride 1*850 

sulphide 0*102 

thiosulphate        .....  0*369 

sulphide 0*235 

cyanide 0*087 

Alumina  ...        k        ....  1*510 

Silica        .        .        .        .                 .        .        .  0*186 

Iron  .  . traces 

Purification  and  Concentration  of  the  Lye. — The  lye,  when  freed  by  settling  from  all 
suspended  matter,  contains  chiefly  sodium  carbonate  and  caustic  soda,  besides  common  salt 
and  small  quantities  of  other  sodium  salts.  The  presence  of  iron-sodium  sulphide  in 
the  lye  is  to  be  noticed,  as  it  is  the  cause  of  the  colour  of  soda-ash.  To  eliminate  these 
disturbing  iron-compounds  it  is  necessary  to  let  the  lyes  remain  for  some  time  in  the 
settlers,  when  the  iron  sulphide  is  deposited.  For  decomposing  the  ferrocyanide 
Hurter  and  Carey  heat  the  lye  in  a  worm  to  180°.  If  a  solution  of  sodium  thiosul- 
phate is  heated  with  potassium  ferrocyanide  in  a  closed  tube  there  occurs  a  peculiar 
decomposition.  A  greenish-grey  precipitate  subsides,  having  the  composition  KFeCy3. 
The  rest,  exactly  half  the  cyanogen,  occurs  in  solution  as  potassium  sulphocyanide. 
The  decomposition  takes  place  according  to  the  following  equation  : — 

K4FeCy6  +  3Na2S203  =  KFeCy8  +  3KCyS  +  3Na2S03. 

But  if  the  solution  contains  sodium  carbonate  the  ferrocyanogen  is  completely  decom- 
posed, the  iron  separating  out  as  ferrous  oxide  according  to  the  equation : 

Na4FeCy6  +  6Na2S203  +  2Na2CO3  +  H2O  =  6NaCyS  +  6Na2S03  +  2NaHC03  +  FeO. 
Further,  a  part  of  the  cyanogen  is  split  up  into  ammonia  and  formic  acid,  or  sodium 
formiate,  so  that  the  equation  which  most  accurately  represents  the  reaction  taking 
place  in  the  lyes  is  the  following  : — 

Na4FeCy6  +  sNa2S203  +  2NaC03  +  3H20  = 
SNaCyS  +  5Na2S03  +  NaCHO2  +  NH3  +  2NaHC03  +  FeO. 

The  sulphide  can  also  be  removed  by  oxidation,  as  it  is  done  in  Gossage's  process  by 
means  of  atmospheric  air.  Pauli  promotes  the  oxidation  of  the  sulphur  compounds  in 
the  crude  soda  lye  by  the  addition  of  a  little  manganese  oxide.  Parnell  desulphurises 
by  means  of  zinc  or  zinc  oxide. 

The  lye  is  evaporated  to  a  certain  degree  of  concentration,  when  from  the  super- 
saturated and  boiling  liquid  sodium  carbonate  is  separated  as  a  crystalline  powder  with 
i  mol.  water :  Na2C03  +  H20. 

It  is  fished  out  in  proportion  as  it  separates  *  during  these  operations  fresh  quantities 
of  lye  flow  in  from  the  more  elevated  pans,  and  this  is  continued  for  weeks  or  months 
as  long  as  a  sufficiently  pure  salt  is  obtained.  At  first  the  quantity  of  carbonate  in  the 
lye  greatly  preponderates  over  the  quantity  of  the  other  constituents  above  named, 
but  in  time  the  proportion  becomes  less  favourable.  Hence  the  carbonate  as  it  separates 
out  becomes  more  and  more  impure,  and  is  accompanied  by  common  salt,  and  the 
mother  liquor  which  adheres  to  the  salt  contaminates  it  more  and  more.  The  mother 
liquor  ultimately  remaining  contains  chiefly  caustic  soda  and  sodium  sulphide,  an  excess 
of  these  reduces  the  solvent  power  of  the  lye  for  salts  almost  to  nil.  The  soda-salt, 
fished  out  and  freed  as  far  as  possible  from  the  mother  liquor  by  drainage  or  in  a  centri- 
fugal machine,  is  dried  on  the  hearth  of  a  reverberatory  fed  with  coke,  with  constant 
stirring,  and  calcined,  in  order  to  oxidise  the  sodium  sulphide  of  the  adhering  mother- 
liquor  and  obtain  a  perfectly  white  product.  This  product  is  soda-ash  (calcined  soda) 


3 24  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

The  character  of  this  soda-ash  and  its  percentage  of  carbonate  vary  greatly.  The 
different  sorts  known  in  commerce  are  obtained  by  separating  the  salt  into  classes 
according  to  the  length  of  the  evaporation  of  the  lye.  That  first  obtained  is  the  best 
quality ;  as  the  evaporation  is  prolonged  it  becomes  worse,  and  it  is  at  the  option  of  the 
manufacturer  how  many  sorts  he  will  produce.  A  soda  containing  90  per  cent,  of 
alkaline  matter  is  said  to  be  one  of  90  degrees.  The  rest  is  sulphate  and  common  salt 
with  a  small  quantity  of  sulphite  produced  during  calcining. 

According  to  K.  W.  Jurisch,  at  the  works  of  J.  Muspratt,  of  Widnes,  a  series  of 
samples  of  crude  soda  have  been  examined — i.e.,  from  a  revolver  furnace  in  July  1874 
(I),  from  a  hand-furnace  in  November  1874  (II),  from  a  revolver  furnace  in  April 
1876  (III),  in  the  same  works,  and  in  February  1876  from  a  similar  furnace  in  the 
works  of  Ch.  Tennant  at  St.  Eollox  (IV). 

I.  II.  III.  IV. 

Na2CO3  .  .  .  41*592  ...  41760  ...  46-154  ...  45'28o 

NaCl  .  .  .  1-205  •••'  1'386  •••  0-673  •••  X74° 

Na2S04  .  .  .  1-213  —  2'264  •••  0-353  —  i'5°5 

Na2SO:i  .  .  .  0-145  -  0-534 

Na2S203  .  .  .  ...  0-315  ...  0-593  ...  1-135 

Si02  ....  2-375  ...  4-090  ...  2-680  ...  3-120 

A1203  .  .  .  1*080  ...  1-503  ...  0-785  ...  1-021 

Fe./)3  .  .  .  0-877  •••  1*107  •••  1*015  ..  0-724 

CaC03  .  .  .  11-616  ...  6-636  ...  9-686  ...  5-114 

CaO  .  .  .  5-689  ...  5'8i6  ...  1-695  ...  1-328 

CaS  .  .  .  29-783  ...  31*938  —  33'6i5  •••  30-985 

MgO  ...  —  ...  0-303  ...  0-404  ...  0-295 

Coal  .  .  .  4-425  ...  3-260  ...  3-500  ...  7-370 

The  proportions  of  the  ingredients  used  were  the  following : 

i.  n.  in.  rv. 

Salt  cake       .        .        .     100  ...  100  ...  100  ...  100 

Limestone     .        .         .     106  ...  109  ...           78  ...  73 

Coal      ....       55  ...  56  ...          47-5  ...  41 

Mactear's  lime       .               —  ...  —  ...           7-3  ..  7 

During  the  months  of  December  1879,  January,  February,  and  March,  1880,  daily 
samples  were  taken  of  the  revolver  crude  soda-lyes,  and  the  mixture  was  analysed 
every  week.  One  litre  contained  in  grammes : 

Mean.  Highest.  Lowest. 

Total  Na.,0           .  .  187-980  ...  198-380  ...  168-950 

Na2O  as  Na2CO3  .  147-930  ...  i6ri8o  ...  131-750 

Na2O  as  NaOH   .  .  40-050  ...  4774O  ...  37-200 

Na2COg        .         .  .  252-910  ...  275-560  ...  225-250 

NaOH         .        .  .  51-680  ...  6r6oo  ...  48-000 

NaCl          .        .  .  10-682  ...  15*503  ...  6-274 

NaiSO4        .        .  .  2-793  .»  3755  -  i'944 

Na2SO,        .        .  .  0-291  ...  0-543  ...  0-150 

NagSjO,       .        .  .  1-327  ...  2-080  ...  0-980 

Na2S   ....  4-149  ...  5-043  ....  2-925 

Na4FeCy6    .         .  .  0-768  ...  1-050  ...  0-510 

Si02,Al3Os,Fe203  .  4-656  5-630  ...  3-850 

In  February  there  were  further  taken  daily  samples  of  the  red  liquor  (II),  of  the 
oxidised  red  liquor  (III),  and  of  the  causticised  red  liquor  (IV),  and  analysed  at  the  end 
of  the  month.  In  comparison  with  the  mean  of  the  February  analyses  of  the  revolver 
crude  soda  lyes  (I),  i  litre  contained  in  grammes : 


SECT.    III.] 


I. 

Total  Na2O 

.     191-270 

Na.,0  as  Na2CO, 

.      149-270 

Na50  as  NaOH  . 

42-010 

Na,C03       . 

.     255-200 

NaOH 

54-200 

NaCl 

9-719 

NaJ304       . 

2953 

Na^O,       . 

0-306 

Na,S,03      . 

1-437 

Najs"   "      . 

4-188 

Na4FeCy6  . 

0-710 

Si02,  Al20j,  Fe,03 

5-118 

SODA. 

u. 

189-630 

106-300 

83-330 

181790 

107-520 

26-413 

11-809 

5-603 

6-085 

8-424 

2-280 

6-700 


325 


in. 

158-800 
81-430 
77-380 

139-220 
99-840 
19-481 

9-143 
1-1-26 
9-693 
1-262 
1-500 
4-610 


IV. 

116-850 

14-440 

102-410 

24-690 

132-140 

12-650 

7-204 

2-396 

2-948 

2-507 

0-280 

0-960 


Specific  Gravity     .         1-279        ...  1-290         ...  i'235         ...  1-170 

The  red  liquor  dropping  from  the  revolver  salts  (II.)  is  slightly  diluted  by  condensed 
steam,  with  which  the  salts  are  treated  for  their  better  purification.  The  oxidation 
of  the  red  liquor  was  effected  by  forcing  in  air  with  a  Korting  blast,  with  the  joint  use 
of  Weldon  mud ;  the  causticising  took  place,  according  to  Parnell,  at  a  pressure  of  3 
atmospheres.  The  analyses  confirm  the  opinion  that  almost  all  the  impurities  of  the 
crude  soda-lye  pass  into  the  red  liquor,  so  that  on  oxidation  its  sodium  sulphide  is  con- 
verted into  sodium  dithionate,  and  on  causticising  according  to  Parnell's  process  the 
latter  is  partially  reconverted  into  sodium  sulphide  and  sulphite.  The  lime  also  precipi- 
tates silica,  alumina,  and  iron  oxide,  apparently  also  some  cyanogen. 

Jurisch  further  gives  the  mean  (II.),  the  highest  (III.),  and  the  lowest  (IV.)  values 
from  twenty  daily  analyses,  September  1879,  of  revolver  soda  (made  by  Pechiney's  process) 
by  the  Runcorn  Soap  and  Alkali  Company,  referred  to  100  parts  total  soda  present  as 
Na2C03  and  NaOH,  and  for  comparison  the  analysis  of  a  sixteen  days'  average  sample 
of  crude  soda-lyes  from  hand  furnaces  (Muspratt's  works),  March  1880  (V.),  as  also 
the  mean  of  the  January  analyses  of  the  revolver.  Crude  soda-lyes  all  are  given  in 
column  (I.) : 


Na2O  as  NaOH 
NaCl      . 

I. 
21-290 
c-qiO 

II. 
13-320 

III. 
15-160 

IV. 

.     8-500     .. 

V. 

•      33'57o 

7"27Q 

Na,S04  . 
Na~SO3  . 

1-720 
O"l64. 

4-142 

5-400     . 

2-800 

6-042 
0-383 

Na2S203 
Na.,S      . 
Na'.FeCy,       . 
SiO,,  A1203,  Fe203 

.       0-666       ... 
.       2-053       ••• 
•       0-358       ... 
•       2-373       ••• 

1-486 
1-433 

O'2l6 

1-630 
1-820 
0-348     . 

I-20O 
.         0-930         .. 
..         0-174          .. 

1-081 

1-359 
O-I50 
2-730 

If  the  crude  soda-lye  is  at  once  evaporated  to  dryness,  so  that  no  mother  liquor 
remains,  the  reverberatory  (Fig.  294)  is  used.  A  thick  layer  of  the  soda-salt  is  first 
rammed  down  upon  the  sole 

of  the  furnace  to  prevent  the  Fig.  294. 

lye  from  coming  in  contact 
with  the  bricks.  As  soon  as 
the  furnace  has  been  raised 
to  dull  redness  by  the  coke 
fire  burning  in  A,  the  lye, 
which  has  been  concentrated 
to  55°  Tw.,  is  let  flow  down 
from  the  heating  pans,  D  and 
E,  into  the  furnace.  As  soon 
as  it  touches  the  hot  soda- 
salt  a  violent  boiling  begins ;  the  mass  rises  and  falls  and  is  easily  brought  to  dryness. 
The  salt  is  kept  in  powder  by  stirring  with  iron  rabbles.  As  soon  as  a  sufficient 


326 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


quantity  of  salt  has  been  obtained  the  further  flow  of  the  lye  is  stopped,  and  the  dry 
salt  is  drawn  out  of  the  furnace.  The  gases  of  combustion  can  be  led  either  into  the 
chimney  or  underneath  the  lye-pans,  D  and  E,  through  the  traps,  F  and  G,  and  the 
flues,  C,  C'. 

J.  Brown,  on  analysing  the  soda  ash,  obtained  by  concentrating  the  crude  lye: 


Sodium  carbonate 
hydroxide 
sulphite 
thiosulphate 
sulphide 
chloride 
aluminate 
silicate    . 

Insoluble  matter 


I. 
68-907 

I4-433 
7-018 
2-231 


i-oi6 
1-030 
0-814 


II. 

65-5I3 
16-072 
7-812 
2-134 
i '542 
3-862 
1-232 
o-8oo 
Q'974 


If  a  reverberatory  fire  is  used,  a  part  of  the  sulphur  dioxide  contained  in  the  smoke 
gases  is  absorbed   by  the  soda-lye,  so  that   the  soda  is  reduced  in  value.      At   the 

Fig.  295. 


Fig.  296. 


Liingenschnilt — Longitudinal  Section. 

Rhenania  works  and  at  Saarau,  according  to  the  sugges- 
tion of  Thelen,  the  evaporation  of  the  soda-lyes  is  con- 
ducted in  a  hemispherical  pan  of  i  metre  radius  and 
7  metres  in  depth.  In  the  shaft,  W,  moved  by  the  helix, 
E  (Figs.  295  and  296),  rods,  F,  are  fixed,  carrying  shovels, 
G,  fixed  obliquely.  On  passing  through  the  lye,  they 
touch  the  bottom  of  the  pan,  push  the  salt  on  towards 
the  end,  where  it  is  removed  by  a  shovel  to  be  dried 
in  similar  drying  apparatus. 

For  producing  soda  crystals,*  Na2C03+  ioH20  (with 
63  per  cent,  of  water),  the  soda-ash  is  dissolved  in  hot 
water,  clarified  by  standing,  and  the  liquid  is  let  cool  in 
large  iron  vessels,  when  it  deposits  large  crystals.  The  soda-salt  is  often  dissolved  in 
pans  of  sheet-iron  (Fig.  297),  into  which  a  current  of  steam  is  passed  through  the  pipe,  C. 
The  soda  to  be  dissolved  is  placed  on  the  sieve-like  perforated  sheet-iron  vessel,  D, 

*  Sal-soda  of  American  writers. 


SECT.    III.] 


SODA 


327 


which  can  be  raised  or  lowered.  The  pan  is  filled  through  the  pipe,  C,  to  three-quarters 
its  depth  with  water,  and  the  vessel.  />,  containing  the  soda,  is  next  introduced,  whilst 
steam  is  blown  in  through  C.  As  soon  as  the  lye  shows  a  sp.  gr.  of  50°  to  53°  Tw.  it 
is  run  into  the  sheet-iron  crystallisers,  which  are  about  5  metres  long,  2  broad,  and 
0-45  metre  deep,  and  which  should  be  placed  in  a  cool,  airy  place  At  a  medium 
temperature,  the  formation  of  the  crystals  is  complete  in  about  five  to  six  days  Alter 
the  mother  liquor  has  been  let  off  through  an  aperture  at  the  bottom  of  the  crystal- 
lising vessels  it  is  then  worked  up  to  a  low-grade  soda :  *  the  crystals  are  removed  from 
the  sides  and  submitted  to  re-crystallisation. 

For  this  purpose,  the  soda-crystals  are  dissolved  in  a  conical  sheet-iron  pan,  A 
(Fig.  298),  which  is  directly  heated  by  the  flame  of  the  fire,  C.  By  means  of  the  flues, 
D,  the  flame  plays  quite  round  the  pan.  The  pan  is  filled  with  crystals,  a  little  water 
is  introduced  through  B,  and  heat  is  applied.  The  crystalline  water  is  sufficient  to 
melt  the  salt.  The  fire  is  then  withdrawn,  the  pan  is  covered  with  a  wooden  lid,  and 
the  liquid  is  let  settle.  When  it  has  become  clear,  the  lye  is  conveyed  by  syphons  into 
a  cistern,  and  thence  into  quadrangular  cisterns  of  sheet-iron  of  40  to  50  centimetres  in 
diameter.  Here  the  crystallisation  begins,  and  is  completed  in  about  eight  days. 
After  the  mother  liquor  has  been  removed  from  the  crystals,  the  iron  vessels  are  set 


Fig.  297. 


Fig.  298. 


for  a  short  time  in  a  pan  of  boiling  water,  when  the  crystals  are  detached  from  the 
wall  in  consequence  of  beginning  to  melt,  so  that  on  merely  inverting  the  vessels  the 
crystalline  mass  falls  out  in  a  body.  After  draining,  the  mass  is  broken  up,  dried 
in  a  desiccating  chamber  at  15°  to  18°,  or  at  once  packed  in  casks  to  prevent  and 
efflorescence. 

The  crystalline  state  affords  a  guarantee  for  purity  (supposing  that  the  crystals 
were  not  produced  from  a  mixture  of  sodium  carbonate  and  sulphate,  in  which  case 
they  may  contain  large  proportions  of  sulphate — sometimes  up  to  50  per  cent.).  The 
more  general  employment  of  soda-crystals  is  prevented  by  their  high  proportion  of  water, 
which  increases  the  freight. 

Melting  pans  for  soda  must  be  constructed  of  a  different  kind  of  iron  pan  from  salt- 
cake  pans.  Resistance  to  acids  demands  a  large  proportion  of  carbon  in  chemical 
combination ;  whilst  resistance  to  alkalies  requires,  on  the  other  hand,  a  high  per- 
centage of  graphite  and  a  low  percentage  of  combined  carbon.  In  the  former  case, 


*  So-called  "weak  ash.1' 


328  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

the  iron  must  contain  much  manganese  and  little  silicon,  but  in  the  second  case  much 
silicon  and  as  little  manganese  as  possible.  From  one  and  the  same  mixture  of  irons  we 
may  obtain  either  only  good  salt-cake  pans  and  bad  soda-pans,  or  bad  salt-cake  pans 
and  good  soda-pans ;  or,  what  most  frequently  happens,  medium  salt-cake  pans  and 
medium  soda-pans.  Melting  alkalies  dissolve  the  combined  carbon  with  a  deep-brown 
<X)lour,  manganese  as  a  manganate,  and  phosphorus  as  a  phosphate,  so  that  iron  is 
mostly  attacked  when  these  substances  are  present  in  quantity.  Graphite,  silicon, 
and  ferrosilicon  are  very  slowly  attacked  by  alkalies.  In  order  to  determine 
the  resistence  to  alkalies  of  a  sample  of  cast  iron,  5*6  grammes  of  it  are  heated  to 
quiet  fusion  with  6*2  grammes  caustic  soda ;  the  melt  is  dissolved  in  water,  and  the 
loss  in  weight  of  the  iron  is  determined.  For  determining  the  resistance  to  acids,  the 
sample  should  be  laid  in  melting  acid  potassium  sulphate  ;  5-6  grammes  of  a  salt-cake 
pan  on  fusion  with  27*2  potassium  bisulphate  should  lose  at  most  25  per  cent. 

Theory  of  the  Formation  of  Soda. — It  was  formerly  assumed,  according  to  the  ex- 
planation of  Dumas,  that,  on  calcining  a  mixture  of  sulphate,  limestone,  and  coal,  the 
coal,  producing  carbon  monoxide,  reduced  the  sulphate  to  sodium  sulphide,  which  was 
then  decomposed,  with  the  formation  of  sodium  carbonate  and  calcium  oxysulphide 
and  the  escape  of  a  part  of  the  carbon  dioxide.*  According  to  the  view  of  Unger, 
which  essentially  agrees  with  that  of  E.  Kopp  (1865),  after  the  sodium  sulphide  has 
been  formed,  the  calcium  carbonate  loses  carbonic  acid,  and  there  remains  behind 
a  mixture  of  caustic  lime,  sodium  sulphate,  and  carbon,  which  is  transformed  into 
caustic  soda  and  calcium  oxysulphide :  the  soda  takes  up  carbon  dioxide,  and  is  con- 
verted into  sodium  carbonate. 

The  latter  view  probably  approaches  nearest  the  truth ;  but  it  is  not  necessary  to 
assume  the  existence  of  a  calcium  oxysulphide  in  order  to  explain  the  inaction  of  cal- 
cium sulphide  with  sodium  carbonate,  since  calcium  sulphide  is  almost  insoluble  in 
water  (i  part  calcium  sulphide  requires  12,500  parts  water  at  I2'6°  for  solution).  The 
excess  of  lime  employed  in  practice,  doubtless  favourable  for  the  purity  of  the  product, 
is  sufficiently  explained  by  the  circumstance  that  the  lime,  as  an  infusible  solid,  does 
not  come  into  full  action  in  the  soda-melt,  which,  though  a  soft  paste,  is  by  no  means 
a  liquid.  The  excess  of  lime  is  to  be  regarded  merely  as  representing  the  coarser 
particles  which  remain  inactive. 

During  the  formation  of  soda  in  the  furnace  the  existing  carbon  becomes  carbon 
dioxide — 

5Na2S04  -I-  loC  =  sNa2S  +   ioC02;  and 
SNa,S  +  7CaCO3  =  5Na2C03  +  sCaS  +  2CaO  +  2COr 

However,  as  during  the  operation  of  the  formation  of  soda,  and  especially  towards 
the  end,  carbon  monoxide  is  evolved  out  of  the  melting  mixture  and  burns  with  a 
blue  flame,  a  gaseous  development  which  persists  after  the  melt  has  been  drawn  out  of 
the  furnace ;  this  carbon  monoxide,  though  it  is  a  secondary  product,  must  be  con- 
sidered in  the  equation.  The  formation  of  carbon  monoxide  is  of  great  importance, 
because  its  appearance  shows  when  the  heat  is  sufficiently  high  and  the  mean  reaction 
is  at  an  end.  The  researches  of  Unger  place  it  beyond  doubt  that  in  the  reduction  of 
sulphate  by  coal  there  is  a  formation  of  carbon  dioxide  but  not  of  carbon  monoxide. 
This  latter  gas,  therefore,  is  not  formed  during  the  reduction  of  the  sulphate,  but 
is  a  result  of  the  action  of  coal  upon  the  excess  of  chalk  or  limestone.  The  reduc- 
tion of  calcium  carbonate  by  coal  does  not  occur  until  a  far  higher  temperature  is 
reached  than  that  which  effects  the  reduction  of  the  sulphate ;  it  follows  upon  the 
latter,  i.e.,  the  conclusion  of  the  main  reaction.  In  this  stage  the  sodium  carbonate 
is  already  formed. 

*  (a)  Na,S04  +  4C  =  Na.S  +  4CO  ;  (0)  aNa^S  +  3CaC08  -  zNa^CO,  +  CaO,2CaS  +  CO,. 


SECT,  in.]  SODA.  329 

We  have  therefore  to  distinguish  three  stages  in  the  production  of  soda :  at  first 
there  is  reduction  of  the  sulphate  with  evolution  of  carbon  dioxide — 

Na2S04  +  20  =  Na2S  +  2  CO,. 

Then  follows  the  double  decomposition  between  the  sodium  sulphide  just  produced  and 
the  calcium  carbonate  :  Na2S  +  CaCO3  =  Na2C03  +  CaS *  then  occurs  a  partial  reduction 
of  the  excess  of  calcium  carbonate  employed  bythe  carbon(2CaC03  +  20  =  2CaO  +  4.CO). 

On  lixiviation  the  caustic  lime  occasions  the  formation  of  caustic  soda. 

Theory  consequently  requires  only  20  parts  of  coal  to  100  parts  sulphate.  The 
customary  addition  of  carbon  in  excess  (40  to  75  per  cent.)  is  advantageous  from  a  two- 
fold point  of  view  :  first,  as  a  substitute  for  that  which  has  reduced  a  part  of  the  carbon 
dioxide  to  carbon  monoxide *  secondly,  the  addition  renders  it  possible  to  seize  the 
exact  moment  when  the  reaction  is  completed  and  the  melt  must  be  withdrawn  from 
the  heat  of  the  furnace,  i.e.,  after  the  liberation  of  carbon  monoxide  has  begun  and 
before  it  has  ceased. 

Utilisation  of  the  Leblanc  Soda- Residues. — As  already  pointed  out,  the  Leblanc 
process  has  furnished  (until  quite  recently)  the  chief  quantity  of  the  soda,  caustic 
soda,  and  bicarbonate  which  are  consumed.  This  superiority  over  all  other  processes  is 
due  in  great  part  to  the  production  of  the  soda-residues,  in  as  far  as  they  have  the  property 
of  being  easily  and  completely  separated  by  lixiviation  from  the  alkali  contained  in  the 
crude  soda.  At  the  same  time,  these  residues  form  the  darkest  side  of  this  impor- 
tant branch  of  chemical  industry.  The  great  quantity  of  sulphur  which  enters  into 
this  process  is  lost  in  the  residues  in  such  a  manner  that  at  the  alkali- works  of  Dieuze, 
in  Lorraine,  the  sulphur  stored  up  in  the  solid  residues,  down  to  the  year  1869, 
was  estimated  at  the  value  of  43  million  marks,  or  in  round  numbers  ^£2, 300,000. 
Each  ton  of  alkali  yields  i|  ton  of  dry  residues,  and  the  masses  produced  in  this  manner 
are  generally  piled  up  in  heaps  near  the  works,  forming  hills  of  considerable  elevation. 
These  residues,  especially  in  warm  weather,  evolve  sulphuretted  hydrogen  in  serious 
quantity,  which  annoys  and  injures  the  inhabitants  of  the  district.  Moreover,  the  rain 
and  the  surface  waters  which  come  in  contact  with  these  heaps  extract  from  them  a 
more  or  less  intensely  coloured  liquid  containing  calcium  sulphide  and  polysulphide, 
which  poisons  the  wells  and  water-courses  into  which  it  penetrates.  All  attempts  to 
recover  this  sulphur  in  a  simple  and  cheap  manner,  and  thus  to  do  away  with  the 
nuisance  and  the  danger  to  the  public,  have  until  recently  proved  fruitless. 

The  soda-residues  (tank-waste  or  vat-waste)  from  the  "  Silesia "  works  at  Saarau 
have,  when  dry,  according  to  E.  Bichters  (1869),  the  following  composition  : 

Calcium  sulphide  .         .  37-62  ...  38-04  ...  39*10  (  =  16  to  i8%S) 

Iron  sulphide         .         .  i'88  ...  175  ...  2'oi 

Calcium  thiosulphate    .  2-69  ...  3-02  ...  2-35 

„        carbonate         .  23-18  ...  22*24  ...  24*02 

„        sulphate  .         .  1*68  ...  1*01  ...  1*38 

„        sulphite  .        .  074  ...  0*31  ...  0*63 

Lime  (CaO)   .        .        .  6-49  ...  7'oo  ...  7^5 

Alumina         .        .  2'ii  ...  2-02  ...  2'oo 

Soda      ....  2*52  ...  2*10  ...  1-86 

Silica  (combined)  .        .  4*24  ...  4*03  ...  4*62 

Water   ....  2-32  ...  3*29  ...  1-51 

Sand     ....  774  ...  6-82  ...  7'2i 

Carbon                    .        .  5-41  ...  6-oo  ...  6*39 

jnesia       .        .        .  0*64  ...  0*51  ...  0-70 

99-26  ...  98-17  ...          101-06 


33o  CHEMICAL  TECHNOLOGY. 

Chance  gives  the  following  analysis,  executed  in  June  1882  : — 


[SECT.  in. 


I 

. 

o 

o 
O 

i 

0 

o  . 

°i 

1 

E*    S 

4 

8 

-a 

"a    • 

OQ 

"STS 

-3  $ 

cc    . 

»      2 

a 

0 

•~  <u 

<*3    • 

°'o3 

J8.S 

<*3  c« 

5  t^-So 

8  g 

"s  ° 

11 

|| 

<&  0 

§3 

3~ 

°%£ 

Works 

,§•§ 

<!3 

«•§ 

&g 

A 

1* 
§•2 

|S 

"SsJ 

~$ 
1 

*C 

r 

0)    3 

aSS 
1 

% 

II 

• 

H| 

C5g 
O 

i°i 

o 

N 

£ 

| 

5 

& 

J* 

Re- 
volver. 

Re- 
volver. 

Re- 
volver. 

Re- 
volver. 

Hand. 

Re- 
volver. 

Re- 
volver. 

Hand. 

Hand. 

Soda  mixture  — 

Salt  cake     .        .        . 

lOO'OO 

lOO'OO 

lOO'OO 

lOO'OO 

— 

100*00 

— 

100-00 

lOO'OO 

lOO'OO 

Limestone   . 

86-00 

86-00 

95-0 

105-00 

— 

loo-oo 

— 

105-00 

105-00 

105-00 

Coal     .... 

40t042 

40-00 

53-0 

33*33 

— 

57-00 

— 

57-50 

65*00 

65-00 

Sulphur  — 

Total  in  waste 

26-33 

24-29 

23-52 

22.66 

2073 

17-94 

18-84 

19-47 

17-22 

18-04 

Recoverable         . 

25-28 

23-87 

23-10 

21-30 

19-87 

17-83 

I7-59 

17-17 

I5-59 

16-83 

Per  cent. 

96-02 

98-27 

98-21 

94-00 

95-85 

99-39 

93-36 

88-19 

90-53 

93-29 

Soda  residues  — 

Sodium  carbonate        . 

3'i6 

2-57 

— 

o*45 

— 

— 

— 

3-69 

1*63 

1-97 

Sodium  oxide       .        . 

— 

— 

1-47 

— 

— 

— 

I-I7 

Sodium  hydrate  . 

— 

— 

— 

— 

— 

1-88 

Calcium  carbonate 

zi'ig 

28-10 

20*07 

38-14 

35  '26 

27-92 

28-41 

23-64 

38-8I 

36-92 

Calcium  hydrate  . 

trace 

— 

5-92 

7-62 

— 

8-60 

4-90 

8-89 

9-53 

8-85 

Calcium  sulphide 

56-89 

5377 

52-03 

47-97 

44-75 

40-16 

39-62 

38-67 

35-12 

37-90 

Calcium  thiosulphate  . 

1-07 

— 

— 

— 

— 

— 

I-I9 

2-85 

1-49 

0-68 

Calcium  sulphite 

trace 

Calcium  sulphate 

trace 

— 

trace 

— 

376 

— 

2-13 

0*91 

— 

O'2O 

Calcium  silicate  . 

3-53 

1-47 

— 

— 

— 

2-96 

— 

4-19 

Carbon 

7  "20 

9-62 

13-69 

0-30 

572 

12-33 

8-03 

5-86 

6-27 

7-04 

Magnesium  carbonate  . 

— 

— 

— 

— 

— 

I'35 

0-98 

Magnesium  oxide 

— 

— 

0-16 

— 

0-42 

2-13 

— 

— 

— 

trace 

Alumina 

I  -02 

074 

1-98 

— 

2-45 

2'Ij 

8-62 

I  -01 

0-13 

0*34 

Ferric  sulphide    . 

1-65 

1-16 

1-16 

374 

O"29 

O'7O 

2-16 

276 

2-44 

Ferric  oxide 

— 

— 

— 

— 

1-64 

Silica  .... 

— 

— 

1-50 

— 

— 

— 

— 

— 

I  -21 

i-34 

Sand    .... 

2-82 

0-89 

2-09 

2-51 

6'oo 

0-66 

3-98 

7-41 

2'6l 

179 

Total      . 

98-53 

98-32 

100-51 

10073 

lOO'OO 

99-06 

lOO'IO 

100-56 

99-56 

99-47 

Moisture  in  fresh  water  . 

29-20 

29-41 

27-50 

— 

— 

— 

— 

30-40 

29-96 

It  was  not  until  1863  that  soda  was  regularly  obtained  from  vat-waste,  i.e.,  by  the 
process  of  Guckelberger  (improved  by  L.  Mond),  of  Schaffner  (of  Aussig),  of  P.  W. 
Hofmann  (of  Dieuze),  and  of  Schaffner  and  Helbig  (1878).  The  earlier  processes 
depend  on  the  conversion  of  the  insoluble  calcium  sulphides  in  the  waste  into  soluble 
compounds  by  means  of  oxidation  effected  by  atmospheric  oxygen,  lixiviation  of  the 
oxidised  mass,  and  precipitation  of  the  sulphur  present  in  the  lyes  (in  the  form  of  poly- 
sulphides  and  of  thiosulphate)  by  the  addition  of  an  acid,  hydrochloric  acid  being  always 
used  as  a  matter  of  course  in  actual  practice. 

The  earliest  process  of  Schaffner  consists  of  the  following  operations :  the 
production  of  the  sulphur-lye,  its  decomposition,  and  the  precipitation  of  the  sulphur. 

For  obtaining  the  sulphur-lye,  the  vat-waste  is  subjected  to  an  oxidation  process  in 
the  air  by  being  thrown  up  in  heaps.  The  heaps  heat  in  time,  and  the  formation  of 
polysulphides,  and  on  further  oxidation  that  of  thiosulphates,  begins.  Practice  soon 
teaches  how  long  a  heap  should  lie.  After  some  weeks  the  heap  has  a  yellowish-green  colour 
within,  and  is  ready  for  lixiviation.  It  is  broken  up  and  remains  for  twenty-four  hours 
exposed  to  the  air,  when  the  oxidation  is  complete.  The  lixiviation  is  effected  with  cold 
water,  as  in  the  case  of  crude  soda ;  so  that  at  the  conclusion  only  concentrated  lyes  come 
into  play.  After  this  lixiviation  process  the  waste  is  once  more  oxidised  by  placing  it 
in  pits  i  metre  in  depth  and  width,  made  near  the  lixiviation  tanks.  This  oxidation 


SECT,  in.]  SODA.  331 

in  pits  is  more  rapid  than  the  former  oxidation.  The  former  lixiviation  pro'cess  has 
made  the  mass  more  porous,  so  that  the  air  has  better  access,  and  there  are  formed  more 
thiosulphates  along  with  the  polysulphides.  Or,  instead  of  putting  the  residues  in 
these  pits,  they  can  be  let  remain  in  the  lixiviation  tanks,  and  the  second  oxidation  can 
be  accelerated  by  forcing  the  gases  from  a  chimney  under  the  double  bottom  of  the 
lixiviation-tanks.  Labour  is  thus  economised,  as  the  filling  and  emptying  the  pits  is  dis- 
pensed with.  This  kind  of  oxidation  is  very  energetic,  and  in  eight  to  ten  hours  the  mass  is 
again  ripe  for  lixiviation.  This  oxidation  may  be  repeated  from  three  to  ten  times,  accord- 
ing to  the  character  of  the  waste.  The  furnace  gases  decompose  the  calcium  sulphide 
in  such  a  manner  that  polysulphide  and  thiosulphate  are  formed.  The  gases  must  not 
be  employed  too  hot.  The  lyes  from  the  first  oxidation  consist  chiefly  of  polysulphides 
and  thiosulphates  :  in  those  of  the  second  lixiviation  the  thiosulphate  predominates, 
and  in  the  third  this  is  still  more  the  case.  All  the  lyes  are  mixed  in  a  common  tank. 
The  product  of  this  operation  is  therefore  a  lye  of  calcium  polysulphides  with  a  certain 
proportion  of  thiosulphates. 

The  decomposition  of  the  lye  with  hydrochloric  acid  is  effected  in  closed  apparatus 
of  cast-iron  or  stone.  In  the  decomposition  of  calcium  thiosulphate  by  hydrochloric 
acid,  sulphurous  acid  is  evolved  and  sulphur  separates  out: 

CaS8O3  +   2HC1  =  Ca012  +  SO2  +  S  +  H2O. 

The  sulphurous  acid  further  decomposes  the  polysulphide  into  calcium  thiosulphate 
with  elimination  of  sulphur  : 

2CaSx  +  3SO2  =  2CaS,O3  +  Sx. 

By  titration  the  sulphur-lye  may  be  tested  for  its  proportion  of  polysulphide  and 
thiosulphate,  and  the  waste  may  be  oxidised  accordingly.  Fig.  299  shows  the  cast- 
iron  precipitating  apparatus  as  generally  introduced.  A  and  B  contain  the  lye  to  be 


decomposed.  By  means  of  a  flexible  tube  attached  to  I,  the  lye  is  directed  either 
through  q  into  A,  or  through  q'  into  B.  Earthen  pipes,  T,  serve  for  introducing  the 
hydrochloric  acid.  The  tubes,  c  and  d,  likewise  correspond  with  the  gas  apparatus ;  c  is 
placed  on  the  cover  of  A,  whilst  its  long  limb  opens  into  the  liquid  in  B ;  at  d  we  have 
the  reverse  case — the  short  limb  is  on  the  cover  of  B,  whilst  its  long  limb  plunges  into 
the  liquid  in  A.  The  cock  «  is  closed  when  the  gases  have  to  pass  through  c  into  the 
liquid  in  B  ;  the  cock  b  is  closed  if  the  gases  have  to  pass  through  d  into  the  liquid  in  A. 
Any  superfluous  gas  escapes  through  R.  After  the  decomposition  steam  is  blown  in 
through  the  valves,  V  and  V,  in  order  to  expel  any  residue  of  sulphurous  acid  absorbed 
by  the  liquid.  When  the  process  is  at  an  end,  the  sulphur  flows  out,  with  the  chloride 
of  calcium  lye,  through  the  aperture,  0.  At  first  the  wooden  plug  is  opened,  and  the 


332 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


chief  part  of  the  calcium  chloride  lye  is  allowed  to  flow  out.  In  order  to  find  whether 
all  the  sulphurous  acid  is  expelled,  the  cock  h  is  opened,  and  the  escape  of  sulphurous 
acid,  if  occurring,  is  detected  by  the  smell.  The  cocks//',  serve  to  show  whether  the 
apparatus  is  properly  filled  with  lye,  and  to  judge  of  the  progress  of  the  decomposition. 
The  sulphur  obtained  is  finely  granular  arid  contains  a  little  gypsum  ;  it  flows  with  the 
calcium  chloride  liquor  in  a  channel,  g,  and  from  here  into  a  cistern  with  a  double  bottom ; 
the  lye  flows  off  and  the  sulphur  is  left  behind ;  it  is  washed  with  water,  and  then  under- 
goes the  melting  or  purifying  process. 

The  sulphur  from  the  precipitating  apparatus  is  placed  in  a  closed  cast-iron  pan  with 
so  much  water  that  the  mass  has  a  pasty  composition,  and  steam  is  let  enter  at  the 
pressure  of  if  atmosphere.  In  this  manner  the  sulphur  melts  under  water,  the 
calcium  chloride  lye  adhering  to  it  is  taken  up  by  the  water,  and  the  gypsum  becomes 
distributed  as  a  fine  crystalline  powder.  The  fused  sulphur  collects  at  the  lowest  part 
of  the  pan,  and  can  be  run  off  and  cast  in  moulds.  When  all  the  sulphur  is  removed 
the  gypserous  water  is  let  flow  off,  and  sulphur  and  water  are  sharply  separated  from 
each  other  by  their  specific  gravities.  Along  with  the  sulphur  a  small  quantity 
of  lime  is  put  in  the  pan  to  take  up  any  free  acid.  The  excess  of  lime  forms,  on 
melting,  calcium  sulphide,  and  if  the  sulphur  is  arseniferous  the  arsenic 
sulphide  dissolves  in  the  calcium  sulphide  and  passes  into  the  supernatant  water.  On 
melting  under  water  it  is  not  necessary  to  carefully  wash  and  dry  the  sulphur :  distilla- 
tion is  dispensed  with,  and  the  sulphur  is  freed  from  arsenic  by  one  and  the  same 
process.  The  method  of  smelting  with  steam  pressure  has  the  advantage  that  the 
sulphur  is  only  heated  enough  to  become  a  thin  liquid  and  cannot  be  overheated, 
which  is  important  as  regards  the  subsequent  casting. 

Fig.  300  shows  the  melting-pan.  A  cast-iron  cylinder,  B,  lies  in  a  wrought- 
iron  cylinder,  A,  the  ends  of  both  being  screwed  together.  The  apparatus  slopes  to 

one  end,  so  that  the  melted  sulphur  may 
collect  at  the  lowest  part.  Into  the  inner 
cylinder  are  put  the  sulphur,  and  the  need- 
ful quantity  of  water,  and  there  is  in  this 
cylinder  a  shaft  with  ."i/ms  turned  by  means 
of  the  toothed  wheel,  7\  The  sulphur  is  in- 
troduced at  m.  The  steam  enters  at  a  into  the 
wrought-iron  cylinder,  surrounding  the  cast- 
iron  cylinder  B,  into  which  it  enters  at  o, 
and  after  the  fusion  is  complete  it  is  let 
escape  from  the  dome,  d,  provided  with  a 
safety-valve,  /&*.  The  melted  sulphur  is  let  off 
at  z.  In  this  manner  from  50  to  60  per 
cent,  of  the  sulphur  present  in  the  waste  is 
obtained  in  the  state  of  pure  sulphur.  To 
i  part  sulphur  there  are  used  2  to  2^  per 
cent,  hydrochloric  acid. 

Mond's  Recovery  Process. — Guckelberger  observed  that,  by  oxidising  and  lixiviating 
the  vat-wastes,  solutions  are  obtained  which  contain  not  merely  thiosiilphate,  but  poly- 
sulphides  in  quantity,  and  which,  with  acids,  give  a  precipitate  of  sulphur.  Like 
Schaffner,  Guckelberger  also  found  that  the  waste  after  being  once  lixiviated  yielded 
further  quantities  of  lye  on  repeated  oxidation  and  lixiviation.  The  experiments  were 
carried  on  for  Guckelberger  by  L.  Mond,  who  afterwards  continued  them  on  his  own 
account,  and  arrived  at  the  following  process : — 

The  waste  remains  in  the  lixiviating  vats,  the  number  of  which  is  increased  three- 
fold. The  space  between  the  two  bottoms  is  connected  by  a  tube  to  a  blast,  the  work 


Fig.  300. 


?ECT.    III.] 


SODA. 


333 


Fig.  301. 


of  which  can  be  regulated  by  a  slide  in  the  tube.  As  soon  as  the  last  lye  has  been 
drawn  off. air  is  blown  in.  The  waste  is  heated  by  reason  of  the  accelerated  oxidation 
up  to  94° ;  watery  vapours  escape,  and  on  the  surface  of  the  mass  there  appear  white 
shining  spots.  From  the  quantity  of  the  vapours,  the  number  of  the  spots,  and  the 
temperature,  it  is  seen  whether  the  suitable  degree  of  oxidation  has  been  reached. 
The  waste  is  then  covered  with  water  and  submitted  to  a  methodical  lixiviation.  The 
liquids  obtained  in  the  successive  lixiviations  are  collected  and  conveyed  to  the  precipi- 
tating apparatus.  The  precipitation  of  the  sulphur  is  effected  by  means  of  hydrochloric 
acid  in  a  wooden  vessel  closed  with  a  cover,  in  which  is  a  stirring  apparatus,  an 
escape-pipe  for  gases,  and  an  inlet  pipe  for  steam.  Hydrochloric  acid  and  sulphur- 
lye  are  admitted  alternately.  The  decomposition  ensues  without  any  escape  of 
sulphuretted  hydrogen  or  sulphurous  acid,  if  certain  proportions  are  observed  which 
have  been  ascertained  by  practice.  According  to  Mond,  this  is  the  case  when  the 
equivalents  of  the  thiosulphates  in  the  sulphur-lye  are  to  those  of  the  polysulphides 
as  i :  2.  He  assumes  that  the  decomposition  of  these  compounds  of  hydrochloric  acid 
is  effected  almost  exclusively  according  to  the  following  equation — 

CaS2O3  +  zCaSx  +  6HC1  =  sCaCl,  +  3H2O  +  xS. 

The  temperature  of  the  liquid  in  the  precipitating  apparatus  should  not  fall 
below  40°  nor  exceed  60°.  In  the  former  case  the  precipitated  sulphur  does  not 
deposit  completely,  and  in  the  latter  there  are  formed  large  quantities  of  gypsum,  which 
mix  with  the  sulphur.  The  decomposed  neutralised  lyes  are 
drawn  off  into  settling  cisterns.  The  sulphur  collecting  at 
the  bottom  was  formerly  washed,  dried,  and  at  once  melted. 

Schappi  gives  here  the  following  working  directions : — - 
The  longer  the  lye  and  the  oxidised  residue  are  left  in 
contact  the  more  sulphide  is  dissolved,  and  the  more  strongly 
the  mass  may  be  oxidised  without  danger  of  having  it  over- 
blown. It  is  best  to  oxidise  as  strongly  as  possible,  and  to 
lixiviate  as  long  as  possible  (two  to  three  hours).  The 
weaker  the  lye,  the  richer  it  is  in  sulphides ;  the  stronger, 
the  richer  it  becomes  in  hyposulphite.  The  more  we 
oxidise,  therefore,  the  weaker  the  solution  must  be  kept. 

Schappi  generally  works  with  a  solution  of  16°  Tw.  (hot).  When  he  began  to  work 
with  a  solution  of  12°  Tw.  (hot)  he  could  oxidise  with  a  double  quantity  of  air  without 
obtaining  an  over-blown  lye,  thus  obtaining  a  better  yield  of  sulphur.  With  hot  water, 
not  only  far  more  sulphide  is  dissolved  in  a  short  time,  but,  what  is  more  important, 
the  residue  is  not  cooled.  Hence  the  residue  after  the  lye  is  drawn  off  oxidises  at  once 
well,  whilst,  otherwise,  four  to  six  hours  are  required  before  it  becomes  again  sufficiently 
hot  for  energetic  oxidation.  If  it  is  decomposed  on  the  large  scale,  so  that  lye  and  acid 
mix,  with  exclusion  of  air,  before  entering  the  decomposer,  there  is  a  twofold  gain :  the 
loss  of  sulphuretted  hydrogen  by  imperfect  decomposition  is  unimportant  and  the 
decomposer  works  better.  One  precaution  must  be  observed  :  the  lye  must  be  kept  at 
between  80°  and  90°  by  means  of  waste  steam,  as  the  sulphur  otherwise  does  not 
admit  of  filtration. 

From  the  decomposer  the  solution  flows  through  the  pipe,  /  (Fig.  301),  upon  the 
filters  directly  at  g,  and  at  i  circuitously.  Within  the  decomposer  a  perforated  beam, 
&,  is  placed  laterally,  and  is  connected  by  the  aperture,  c,  with  the  ascending  stoneware 
pipe,  e.  The  lye  and  the  acid  flow  together  (with  a  hydraulic  joint)  through  the  two 
bent  stone-ware  pipes,  a,  mix  on  the  way  to  e,  and  discharge  into  the  upper  layer  of 
the  decomposer,  and  flow  off  to  the  filters,  after  being  completely  worked  through  by 
the  mechanical  agitator  below  in  the  decomposer.  The  stone-ware  pipe,  d,  bent  at 
right  angles,  opens  into  a  channel  in  the  wall  of  the  decomposer.  In  general  it  is  closed 


334  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

with  a  plug,  or  with  a  flexible  tube,  or  a  pinch-cock.  On  setting  the  decomposer  to 
work,  half  the  contents  are  run  out,  d  is  then  opened  in  order  to  empty  the 
pipes  b  and  c,  so  that  they  may  not  be  stopped  by  the  deposit  of  sulphur. 

For  every  residue  there  is  a  certain  specific  gravity  to  which  the  sulphur  lyes  must  be 
brought,  and  which  depends  on  the  time  of  oxidation,  the  time  of  lixiviation,  and  the 
volume  of  air  used  for  oxidation.  The  longer  we  oxidise,  and  the  more  air  we  use,  the 
weaker  the  lye  must  be  kept ;  the  longer  and  hotter  we  lixiviate,  the  stronger  the  lye 
must  be,  in  order  to  obtain  the  most  advantageous  composition.  The  attempt  must  be 
made  with  very  strong  oxidation  to  keep  the  specific  gravity  of  the  lye  so  low  that  it  is 
a,  little  over-blown. 

At  St.  Salindres,  air  is  blown  into  the  yellow  lye  of  the  vat-waste  by  means  of  a 
Korting  blast  up  to  the  point  where  on  treatment  with  acid  neither  H2S  nor  SO2  is 
given  off,  and  the  decomposition  with  hydrochloric  acid  then  follows.  Much  may  be 
here  economised,  because  during  the  operation  of  oxidation  about  one-fourth  of  the 
lime,  in  passing  from  CaS  to  CaO,  is  deposited  in  a  very  dense  condition,  and  can  be 
easily  filtered  off,  whilst  sulphides  are  formed  richer  in  sulphur. 

Recovery  of  Sulphur  by  P.  W.  Hofmann. — At  the  works  at  Dieuze  a  process  was 
developed  between  1864  and  1866  which,  in  addition  to  the  recovery  of  the  sulphur  from 
vat-waste,  aimed  at  reviving  the  manganese  from  the  waste  of  the  chlorine  stills.  The  vat- 
waste  had  been  piled  up  for  more  than  thirty  years.  Close  to  the  works  flows  a  streamlet, 
which  afterwards  touches  the  town  of  Dieuze.  This  stream  takes  up  all  the  sulphur 
compounds  flowing  from  the  waste  in  rainy  weather,  as  well  as  the  acid  manganese 
liquors.  The  water,  for  a  distance  of  6  to  8  kilometres,  was  coloured  black  by  the 
precipitate  of  iron  sulphide,  and  contaminated  the  air  with  hydrogen  sulphide  to  such 
an  extent  that  the  authorities  threatened  to  close  the  works  unless  the  nuisance  was 
promptly  removed. 

The  experiments  made  by  P.  W.  Hofmann  led  finally  to  the  following  results : — 
As  in  the  other  procedures  for  the  recovery  of  sulphur,  soluble  sulphur  compounds  are 
first  produced  by  the  oxidation  of  the  waste.  This  oxidation  is  effected  in  heaps,  which 
are  previously  mixed  with  iron  sulphide  precipitated  from  the  neutralised  manganese 
liquors.  Experiments  proved  that  the  addition  of  iron  sulphide  promoted  the  oxidation. 
The  waste,  after  six  or  seven  days'  exposure  to  the  action  of  the  air,  was  lixiviated, 
yielding  a  liquid  which  was  known  as  eaux  jaunes  sulfurees.  The  residues  were 
oxidised  twice  more  and  treated  with  water,  the  second  and  third  oxidation  not  requiring 
more  than  three  days  each.  The  solution  thus  obtained  contains  principally  calcium 
thiosulphate,  and  was  called  eaux  jaunes  oxydees.  The  united  liquids  from  the 
lixiviations  were  let  flow  into  a  tank  made  of  stone  flags,  made  water-tight  at  the 
junctions  with  asphalt,  and  let  mix  with  the  acid  manganese,  which  had  been  previously 
clarified  by  twenty-four  hours'  rest  in  a  similar  tank.  The  decomposition  of  the  sulphur- 
lye  is  effected  at  the  expense  of  the  free  acid  existing  in  the  manganese  chloride,  as 
well  as  of  the  free  chlorine  and  the  ferric  chloride.  The  separation  of  sulphur  begins 
.at  once,  without  the  escape  of  hydrogen  sulphide,  if  the  respective  proportions  of  the 
two  "  yellow  waters  "  were  correct.  In  order  to  prevent  any  such  escape  the  sulphur- 
lye  is  led,  not  at  once  into  the  cistern,  but  into  a  conical  apparatus  of  sheet-iron.  It  is 
provided  at  half  height  with  two  openings,  through  which  pass  two  tubes,  extending 
down  to  within  a  few  centimetres  of  the  bottom  of  the  cone.  A  little  higher  there  are 
two  other  openings,  through  which  the  liquid  can  flow  off  into  the  cistern.  The 
manganese  liquor  and  the  sulphur-lye  are  let  flow  in  simultaneously  through  the  two 
tubes,  and  in  such  quantity  that  the  efflux  openings  are  kept  constantly  closed  by  the 
inflowing  solutions.  The  first  reaction  takes  place  within  the  cone ;  any  H2S  formed 
collects  in  its  upper  part,  and  is  led  off  through  a  pipe  issuing  from  the  apex  of  the  cone, 
At  the  end  of  which  it  is  burnt.  The  sulphurous  acid  formed  is  carried  off  by  a  tube 


SECT,  in.]  SODA.  335 

into  a  vat  filled  to  two-thirds  of  its  height  with  eaux  jaunes  sulfurees  and  kept  in  con- 
stant motion  by  a  mechanical  agitator.  The  S02  converts  the  calcium  polysulphides  of 
the  eaux  jaunes  sulphurees  into  calcium  thiosulphate,  whilst  sulphur  is  separated. 
The  thiosulphate  is  decomposed  with  sodium  sulphate  and  used  for  preparing  sodium 
thiosulphate. 

The  sulphur  collecting  on  the  false  bottom  of  the  sulphur  vessel  is  washed  and  dried. 
The  neutral  manganese  liquors  are  pumped  into  underground  tanks  with  puddled  clay 
bottoms,  and  with  sides  of  bank  waste  piled  up  on  woodwork.  As  soon  as  the  liquid 
is  clear,  it  is  drawn  into  other  recipients,  in  which  the  last  traces  of  suspended  matter 
quickly  settle.  The  residual  mass  of  iron  sulphide  is  intimately  mixed  with  the  vat- 
waste  produced  daily,  and  exposed  in  heaps  to  the  oxidising  action  of  the  air,  as  already 
described.  The  neutral  manganese  liquors,  freed  from  iron  and  clarified,  are  mixed  in 
a  special  receiver  with  the  yellow  sulphur-lye,  producing  a  deposit  which  contains  all 
the  manganese  along  with  a  quantity  of  free  sulphur.  This  precipitate  is  let  settle, 
the  supernatant  liquor  (calcium  chloride)  run  off  upon  linen  filters,  washed  with  water, 
and  the  residual  mass  dried  upon  stone  flags. 

The  dried  manganese  consists  of  a  mixture  of  manganic  oxide  and  free  sulphur.  In 
order  to  utilise  the  latter,  the  mixture  is  roasted  and  the  S02  is  passed  into  the 
chambers.  The  residue  consists  of  mangano-manganic  oxide,  with  40  to  45  per  cent,  of 
manganese  sulphate.  The  latter  is  dissolved  out  with  water,  yielding  a  mass  which 
consists  of  pure  mangano-manganic  oxide,  free  from  iron,  and  hence  fit  for  use  in  the 
glass  manufacture,  where  iron  gives  a  green  colour.  From  the  aqueous  solution 
manganese  sulphate  may  easily  be  obtained  by  evaporation.  It  is  then  mixed  with 
sodium  nitrate,  and  the  mixture  is  heated  in  the  sulphur  furnaces  with  formation  of 
sodium  sulphate  and  manganese  nitrate,  the  latter  of  which  is  at  once  resolved  into 
higher  oxides  of  manganese  and  hyponitric  acid.  The  hyponitric  acid  passes  into  the 
chambers  along  with  the  sulphurous  acid,  and  aids  in  the  conversion  of  the  latter  into 
sulphuric  acid.  If  the  ignited  mass  is  lixiviated  with  water,  sodium  sulphate  dissolves 
and  manganese  oxides  remain,  containing  about  55  per  cent,  of  manganese  peroxide, 
and  capable  of  being  used  in  the  production  of  chloride  of  lime.  From  the  solution  of 
sodium  sulphate,  Glauber's  salts  may  be  obtained  by  crystallisation,  and  it  is  used  for 
the  decomposition  of  the  neutral  solution  of  calcium  chloride.  There  is  obtained, 
especially  on  stirring,  a  gypsum  of  fine  texture,  which  may  be  used  in  place  of  china 
clay  in  the  paper  manufacture. 

The  more  or  less  profitable  application  of  one  or  the  other  process  for  recovery 
depends  much  on  the  nature  of  the  vat-waste,  on  the  cost  of  labour,  and  on  the  price  of 
sulphur  or  pyrites.  Muddy  waste  cannot  be  advantageously  oxidised  in  Mond's  process, 
and  oxidation  in  heaps  is  here  to  be  preferred.  Hofmann's  process  is  somewhat 
complicated,  but  the  results  are  said  to  be  satisfactory.* 

The  precipitation  of  sulphur  by  the  processes  of  Mond  and  Guckelberger  is  effected 
most  completely  when  free  sulphurous  acid  is  present  in  the  lye,  mixed  with  hydrochloric 
acid  exactly  in  such  a  proportion  that  in  the  fresh  lye  all  the  sulpho  and  hydrosulpho 
compounds  are  converted  into  thiosulphates.  The  thiosulphates,  if  the  process  works 
normally,  are  exactly  converted  by  a  fresh  quantity  of  hydrochloric  acid  into  sul- 
phurous acid  and  free  sulphur,  the  former  of  which  serves  exclusively  for  converting 
the  sulphides  into  thiosulphate.  As  the  liquid  which  runs  off  must  be  neutral,  a  small 
quantity  of  sulphur  is  always  lost  in  it  in  the  form  of  dissolved  thiosulphate. 

According  to  Divers,  when  moist  vat- waste  is  exposed  to  the  air  there  takes  place, 
first,  hydration  of  the  calcium  sulphide.     The  most  important  of  the  hydrogenised  com- 
pounds are :  calcium  hydrosulphide,  a  colourless  crystalline  salt,  which  in  the  air  is 
quickly   decomposed    to  form  calcium  hydrate  and   calcium    hydroxy hydrosulphide. 
*  Probably  labour  is  cheap  there.    It  does  not  appear  to  have  been  widely  adopted. 


336  CHEMICAL  TECHNOLOGY.  [SECT,  in 

This  latter  compound,  CaSH.OH.3Aq.,  is  deposited  from  a  solution  of  calcium  hydro- 
sulphide  which  has  been  mixed  with  lime  and  sugar.  The  compound  is  likewise  pro- 
duced if  solid  calcium  hydrate  is  placed  in  a  solution  of  calcium  hydrosulphate,  and  if 
calcium  hydrate  is  treated  with  sulphuretted  hydrogen.  In  solution  the  compound  is 
quickly  decomposed  with  separation  of  calcium  hydrate.  In  a  concentrated  solution 
of  calcium  hydrosulphate  the  compound  is  insoluble  and  is  then  not  decomposed  by 
water.  The  calcium  sulphide  in  vat-waste  passes  first  into  calcium  hydroxyhydro- 
sulphide,  and  this  is  the  source  of  calcium  hydrosulphate.  As  the  former  compound  is 
insoluble  with  solution  of  calcium  hydrosulphate,  only  weak  solutions  are  obtained  in 
lixiviating  vat-waste.  Concentrated  lyes  of  hydrosulphate  easily  give  off  hydrogen 
sulphide  and  form  calcium  hydroxyhydrosulphide.  The  two  latter  facts  have  hitherto 
frustrated  all  attempts  to  dissolve  out  the  bulk  of  the  sulphur  in  vat- waste  in  an 
inexpensive  manner. 

Divers  believes  that  the  best  process  for  extracting  the  sulphur  from  vat-waste  in 
the  form  of  hydrogen  sulphide  is  to  treat  it  successively  with  steam  in  about  four 
vessels.  By  gradually  oxidising  and  lixiviating  the  vat-waste,  we  obtain  a  mixture  of 
calcium  polysulphide  and  thiosulphate.  A  formation  of  bisulphide  was  formerly 
assumed,  but  now  it  is  found  that  the  products  are  tetra-  and  penta-sulphide.  Hydra- 
tion  of  calcium  sulphide  precedes  all  other  changes  : 

CaS  +  H2O  =  Ca.SH.OH.     Ca.SH.OH  +  H2O  =  CaO2H2  +  H2S. 

Ca.SH.OH  +  H,S  =  CaS2H2  +  H2O. 

Wet  vat-waste  laid  in  covered  heaps  contains,  in  addition  to  unaltered  calcium  sul- 
phide, calcium  hydroxyhydrosulphide,  calcium  hydrate,  and  free  sulphuretted  hydrogen. 
Oxygen  during  the  oxidation  of  vat-waste  acts  upon  the  free  sulphuretted  hydrogen 
which  is  constantly  being  formed.  As  has  long  been  known,  H2S  is  readily,  though 
slowly,  oxidised.  The  experiments  of  Divers  show  that  the  direct  oxidation  of  calcium 
hydrosulphate  by  air  is  extremely  tedious.  He  therefore  concludes  that  only  the  free 
hydrogen  sulphide,  and  not  its  calcium  compounds  in  vat-waste,  is  oxidised  by  the 
air.  Sulphur,  if  boiled  with  lime,  yields  calcium  pentasulphide  and  thiosulphate : 

3CaO2H2  +  128  =  CaS2O3  +  2Ca2S5  +  3H20. 

It  must  be  assumed  that  when  the  reaction  takes  place  at  a  boil  with  ready-formed 
sulphur  it  will  also  take  place  in  the  cold  with  nascent  sulphur  from  the  oxidation  of 
vat-waste.  The  chemistry  of  the  oxidation  of  vat-waste  is  thus  much  simplified.  The 
fixed  products  of  the  hydrolysis  of  calcium  sulphide  are  calcium  hydrate  and  hydrogen 
sulphide ;  the  latter  is  oxidised  by  the  air  to  free  sulphur,  whilst  pentasulphide  and 
thiosulphate  are  formed  with  the  hydrate  of  lime. 

Whilst  in  the  process  depending  on  the  oxidation  of  calcium  sulphide  only  half  the 
sulphur  is  recovered,  the  lime  and  the  remaining  half  of  the  sulphur  forming  a  vat- 
waste  of  the  second  order,  Schaffner  and  Helbig  recover  all  the  lime  and  all  the  sulphur 
in  a  useful  form.  Their  process  for  producing  sulphur  from  vat-waste  and  sulphurous 
acid  with  the  simultaneous  recovery  of  the  earths  combined  with  sulphur  as  carbonates 
depends  on  the  use  of  magnesium  chloride  for  decomposing  the  calcium  sulphide  accord- 
ing to  the  formula : 

CaS  +  MgCl2  =  MgS  +  CaCl2,  and  MgS  +  2H2O  =  Mg(OH)2  +  H2S. 
The  calcium  carbonate  is  not  decomposed  by  the  magnesium  chloride.  The  magnesium 
chloride  employed  is  recovered  as  vat-waste  residue ;  it  consists  of  the  magnesia,  the 
calcium  chloride,  and  the  other  ingredients  which  did  not  enter  into  reaction  after  the 
expulsion  of  the  hydrogen  sulphide.  This  is  exposed  to  the  action  of  C02,  when  calcium 
carbonate  and  magnesium  chloride  are  formed  according  to  the  formula  : 

MgO  +  CaCl,  +  C02  =  MgCl2  +  CaCO3. 

Instead  of  using  magnesium  chloride  alone,  a  portion  of  it  may  be  taken,  hydro- 
chloric acid  being  alternately  or  simultaneously  introduced,  when  the  liberated 


SECT,  m.]  SODA.  337 

magnesia  is  dissolved  and  exerts  its  action  again.     Sulphuretted  hydrogen  is  converted 
by  sulphur  dioxide  into  sulphur,  according  to  the  formula :  2H2S  +  S02  =  38  +  2H2O. 

There  are  here  formed,  however,  not  merely  sulphur  and  water,  but  tetrathionic 
and  pentathionic  acid,  &c.  This  injurious  bye-reaction  is  greatly  lessened  (though 
not  prevented,  as  the  inventors  assume)  by  the  use  of  solutions  of  calcium  and  magne- 
sium chlorides.  If  there  is  an  excess  of  one  or  other  of  the  gases,  this  has  no  effect 
upon  the  reaction.  It  is  not  yet  decided  what  is  the  part  taken  by  these  chlorides  in 
the  reaction,  but  it  is  certain  that  one  equivalent  of  calcium  or  magnesium  chloride  is 
required  for  the  total  sulphur  present.  The  decomposition  of  the  vat-waste  with 
magnesium  chloride  is  effected  in  heat  in  large  closed  iron  vessels,  fitted  with  agita- 
tors. Either  the  vat- waste  is  gradually  introduced  into  the  total  quantity  of  magnesium 
chloride  required  to  fill  the  generator,  or  the  magnesium  chloride  is  let  flow  into  the 
entire  quantity  of  vat-waste,  or  both  substances  are  simultaneously  introduced  into 
the  vessel  in  equivalent  proportions.  The  escape  of  sulphuretted  hydrogen  is  thus  pre- 
vented so  that  no  pressure  can  arise  in  the  generators  and  decomposers ;  further  in  the 
sulphuretted  hydrogen  decomposers  a  larger  quantity  of  S02  is  always  kept  in  store 
than  corresponds  to  the  H^S  flowing  in  from  the  generators.  The  silica  and  alumina 
in  the  vat-waste,  which,  if  they  remained  in  the  recovered  lime,  would  soon  accumulate, 
so  as  to  render  it  useless,  are  removed  by  elutriation  or  by  passing  the  residues  of 
decomposition  through  a  fine  sieve.  The  recovery  of  the  magnesium  chloride  and  the 
lime  from  the  residues  thus  freed  from  slags  (silica  and  alumina)  is  effected  by  passing 
into  them  air  containing  carbon  dioxide  (combustion  gases).  According  to  Chance,  the 
hydrogen  sulphide  burns  to  sulphur  dioxide. 

According  to  a  recent  proposal  of  Schaffner,  the  magnesia  may  be  used  for  decom- 
posing the  sal-ammoniac  lyes  of  the  ammonia  soda  works. 

According  to  C.  Opl,  the  sulphur  is  to  be  dissolved  as  calcium  hydrosulphate  by 
treating  vat-waste  with  sulphuretted  hydrogen.  The  process  is  being  introduced  in 
the  B-henania  works,  as  recently,  in  consequence  of  a  rise  in  the  price  of  hydrochloric 
acid,  the  recovery  of  sulphur  on  Mond's  process  has  become  unprofitable. 

Of  particular  importance  is  the  new  process  of  Chance,  which  carries  out  the 
reaction  :  H2S  +  0  =  H2O  +  S.  The  hydrogen  sulphide  and  other  gases,  chiefly 
nitrogen,  are  allowed  to  mix  with  an  accurately  regulated  quantity  of  air  in  the  pro- 
portion of  H2S  +  0.  The  gases  are  burnt  beneath  the  grate  of  a  circular  shaft  tired 
with  fire-stones.  Upon  the  grate  there  lies  first  a  layer  of  brick,  and  then  one 
of  ferric  oxide.  The  latter  is  heated  to  dull  redness  by  the  reaction  itself,  and 
in  this  state  it  effects  the  almost  completely  smooth  combustion  of  hydrogen 
sulphide  to  watery  vapour  and  sulphur  vapour.  The  vapours  produced  pass  first 
into  a  small  brick  chamber  and  thence  into  a  large  chamber.  The  former  soon 
becomes  so  hot  that  the  subliming  sulphur  melts  and  can  be  drawn  off  in  this  state. 
But  very  much  sulphur  passes  in  the  form  of  vapour  into  the  large  brick  chamber, 
flowers  of  sulphur  condensing  at  the  front  and  water  at  the  back.  As  the  escaping 
gases  still  contain  a  small  quantity  of  unchanged  hydrogen  sulphide  and  also  of 
sulphur  dioxide,  they  are  passed  through  suitable  purifiers  before  escaping  into  the  air. 
As  the  success  of  this  process  depends  in  the  first  place  on  the  exact  equivalence  of 
the  quantity  of  oxygen  to  that  of  the  hydrogen  sulphide — but  the  percentage  of  the 
latter  fluctuates  greatly  in  consequence  of  the  use  of  impure  carbonic  acid — it  is 
important  to  obtain  the  latter  of  rich  and  uniform  composition.  This  is  effected  by 
utilising  the  experience  obtained  in  the  ammonia-soda  process,  according  to  which 
lime-kiln  gases  are  obtained  containing  30  per  cent,  of  carbonic  acid.  But  even  with 
this,  in  all  earlier  experiments  for  decomposing  vat-waste,  gaseous  mixtures  were 
obtained  containing  very  variable  quantities  of  hydrogen  sulphide,  and,  of  course,  with  a 
very  large  admixture  of  foreign  gases.  Chance  has  succeeded  in  greatly  reducing  these 

T 


338 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


mixtures  and  in  producing  a  fairly  constant  yield,  so  that  he  can  now  obtain  with 
certainty  at  pleasure  either  sulphurous  acid  or  sulphur.  He  makes  use  of  the  long- 
known  reaction,  that  carbonic  acid  acts  upon  calcium  sulphide  in  the  presence  of 
water,  so  that  there  is  at  first  a  production  of  calcium  hydrosulphate — 

2CaS    +    GO,    +    H20    =    CaCO,    +    Ca(SH),. 

An  excess  of  carbonic  acid  decomposes  the  hydrosulphate  and  expels  all  the  sul- 
phuretted hydrogen  :  Ca(SH)2  +  C02  +  H20  =  CaC03  +  2H2S. 

In  the  practical  execution  of  the  process  the  vat- waste  is  made  up  with  water  to  a 
thin  paste,  which  is  passed  through  a  sieve  to  remove  all  coarse  parts,  and  in  this  state 
is  conveyed  into  tall  cylinders,  into  which  the  gases  of  the  lime-kiln  are  pumped.  A 
battery  of  seven  cylinders,  4^  metres  high  and  i'8  metre  in  diameter,  is  sufficient  to 
treat  the  residue  from  the  weekly  working  of  300  tons  salt-cake.  In  the  first  vessel 
the  C02  saturates  the  free  lime  and  then  drives  out  the  H2S,  according  to  the  above 
equations.  The  latter,  being  driven  into  other  vessels,  encounters  fresh  vat-waste  and  is 
there  absorbed  with  the  formation  of  calcium  hydrosulphate :  CaS  +  H2S  =  Ca(SH)2,  so 
that  for  a  time  the  escaping  gases  contain  mere  traces  of  C02  and  HSS  and  consequently 
may  escape  into  the  air,  though  for  safety's  sake  they  are  passed  through  lime  or  iron- 
oxide  purifiers.  In  this  manner  considerable  quantities  of  useless  gases  are  got  rid  of. 
In  time  the  sulphuretted  hydrogen  appears  in  more  than  traces.  This  is  detected 
when  in  one  of  the  intermediate  vessels  the  gas  which  escapes  on  opening  a  cock  can  be 
ignited.  The  course  of  the  gases  is  then  changed ;  the  passage  from  the  last  receiver 
into  the  air  is  closed  and  a  pipe  leading  to  a  gas-holder  is  opened.  Into  this  the  gases 
are  passed  as  long  as  they  are  sufficiently  rich  in  H2S.  When  this  ceases  the  pipe  is 
shut  off,  and  as  in  the  meantime  the  vat- waste  in  the  first  cylinders  is  fully  desulphur- 
ised, it  is  taken  out  and  replaced  by  a  fresh  charge,  so  that  the  process  begins  again ; 
the  cylinders  which  were  first  coming  in  turn  last.  The  introduction  of  carbon  dioxide 
is  continued  until  the  clear  nitrate  from  the  cylinders  no  longer  gives  a  reaction  with  a 
salt  of  lead.  The  residue  now  consists  chiefly  of  calcium  carbonate  in  the  form  of 
mud,  but  containing  2-5  to  3  per  cent,  of  soda  in  the  form  of  bicarbonate,  which  is 
utilised  when  this  mass  is  used  in  the  decomposition  furnace.  Another  useful  appli- 
cation is  that  for  cement,  and  in  both  respects  this  residue  is  better  than  that  of  the 
Schaffner-Helbig,  process  as  the  following  analyses  show  : — 


Lime  Eesidue.  —  Schafiher- 

Lime  Eesidue.  — 

Helbig. 

Chance. 

Calcium  carbonate     . 

75-62 

7932 

76-48 

71-14 

84-79 

87-16 

86-32 

„        sulphate 
„         chloride 

4-60 
0.36 

O-25 

4-62 
0-30 

4-52 
1-51 

0-36 

0-49 

0-36 

„        silicate 

— 





I  '91 

2-30 

2  "35 

Magnesium  carbonate 
Magnesia  . 

0'6o 
2-50 

177 
1-67 

0-70 

2-85 

3  "20 

1-03 

I  '07 

Magnesium  chloride 

0-88 

078 

1-70 

2-58 

Sodium  carbonate      . 

— 

— 

— 

0'45 

o-S5 

0-63 

„       sulphate        . 

— 



— 

— 

0-07 

O'2I 

o'O7 

„       silicate          . 

— 







I'47 

I-42 

I  -00 

0-96 

0-80 

0-76 

0-94 

I-I9 

I'47 

FeS   

Fe,O. 

2  "JO 

1-05 

0-71 

0-99 

Coke           

372 

34 
3-00 

I  07 

3-80 

4-06 

2  'O6 

2-98 

n-Xr 

Sand          

0.-o 

O'3O 

I  "12 

o  97 

}    4-65 

4-30 

6'oo 

45 
6-00  j 

o'4S 
0-58 
1-31 

0'54 
0-39 
I'll 

0-40 
1-29 

Moisture  (to  100°)      .        . 
Water  and  loss  .... 

Combined  silica         ... 

— 

— 

— 

— 

171 

1-89 

172 

SO,    
S,  as  sulphide    .... 



— 

z 

0-25 
0-38 

0-41 
O-26 

0-25 
0-36 

S,  free        

}«.« 

0-85 

0-70 

175  { 

o-45 
0-26 

075 

0'5S 
0-32 
0-72 

O-40 
0-37 
0-51 

Soda,  soluble     .... 
Soda,  insoluble  .         .         ... 

SECT,  in.]  SODA.  339 

The  water  running  off  from  this  process  is  clean  enough  to  flow  into  any  stream ; 
it  is  best  utilised  for  making  up  fresh  waste  into  a  paste.  It  contains  grammes  per 
litre: 

Alkalinity,  as  NaHC03,  calculated  as  Na20            •        .         .     6 '63         to        8'6l 
Alkaline  earths  calculated  as  CaCOs 1-50  2-16 


Total  sulphur o-22 

Sulphur  as  sulphates traces 

„        as  thiosulphates 0*05 

„        as  sulphides — 


I'll 

O'OI 

0-23 

O'OO 

0-08 


Silica „ O'oo 

Alumina,  ferric  oxide    ........  traces 

The  sulphuretted  hydrogen  is  collected  in  a  gasometer  of  15  metres  diameter  and 
4'2  metres  effective  height,  containing  850  cubic  metres.  The  water-joint  is  completely 
shut  off  from  the  air  by  a  layer  of  coal-tar  oil  boiling  at  a  very  high  temperature.  The 
composition  of  the  gases  varied,  in  eight  analyses  made  in  four  days,  only  from  32*3  to 
34-0  H2S  and  i'io  to  2'o  CO,  (using  lime-kiln  gases  of  27*0  to  29*1  per  cent.  CO2). 

The  gas  burns  at  once  if  lighted.  The  heat  is  sufficient  to  work  the  Glover  tower, 
and  to  concentrate  acid  set  in  lead  pans  on  or  around  the  furnace.  The  chamber 
room  is  the  same  as  the  pyrites  furnaces,  and  the  consumption  of  nitre  ranges  from 
i 'i 5  to  i '44  per  cent,  on  the  acid  produced,  calculated  as  S03. 

In  working  for  several  months  a  complete  set  of  chambers  in  this  manner,  90  per 
cent,  of  the  sulphur  found  analytically  in  the  vat- waste  had  been  recovered ;  8  percent, 
were  lost  as  iron  sulphide,  as  S02  and  H2S  in  the  main  separation,  in  consequence  of 
accidental  leakages,  &c. ;  5  per  cent,  remained  in  the  coarser  parts  sifted  out,  which 
will  be  utilised  by  improved  arrangements. 

Of  the  H2S  taken  from  the  gasometer,  98  to  99  per  cent,  were  recovered  as  sul- 
phuric acid.  The  acid  is  perfectly  free  from  arsenic,  contains  a  mere  trace  of  iron,  and 
is  nearly  colourless.  From  November  1877  *°  March  3,  1888,  more  than  3000  tons 
of  vat-waste  were  worked  up,  and  about  40  tons  S03  were  produced  weekly. 

The  expense  of  the  process  is  very  small.  The  outlay  for  the  installation  is  only  one- 
half  of  that  for  the  Schaffner-Helbig  process.  The  cost  of  labour  for  the  entire  process 
is  smaller  than  that  for  breaking  up  pyrites,  serving  the  pyrites  furnaces,  and  carrying  off 
the  burnt  ores.  No  fuel  is  required,  except  that  for  raising  the  steam  used  in  pumping 
the  lime-kiln  gases.  An  alkali  manufacturer  who  makes  either  caustic  alkali  or 
chloride  of  lime  requires  for  each  of  these  operations  more  quicklime  than  that  corre- 
sponding to  the  quantity  of  kiln-gases  required  for  treating  the  vat-waste.  Brock  (of 
the  firm  of  Sullivan  &  Co.)  estimates  the  total  cost  of  the  sulphur  at  id.  per  unit — i.e., 
about  8s.  6d.  per  21  cwt.  or  1067  kilos. 

The  economy  of  Chance's  process  can  best  be  appreciated  if  we  realise  that  at 
present  300,000  tons  of  pyrites  are  used  annually  in  England  in  the  Leblanc  process, 
and  that  their  sulphur  has  till  lately  passed  into  the  unendurable  mounds  of  vat- waste. 
If,  in  future,  as  Chance  hopes,  the  pyrites  sulphur  may  be  obtained  gratis  from  the 
mining  companies,  and  if  the  vat-waste  were  worked  upon  the  Chance  process,  there 
would  be  obtained  in  England  yearly  300,000  tons  of  sulphur,  of  which  30,000  to 
40,000  would  be  used  in  this  country,  and  the  rest  would  be  available  for  exportation. 
It  is  to  be  remarked  that,  in  1887,  312,446  tons  were  exported  from  Sicily,  of  which 
88,593  tons  went  to  America. 

The  Ammonia-soda  Process. — If  ammonium  bicarbonate  in  a  concentrated  solu- 
tion is  brought  in  contact  with  saturated  brine,  or  preferably  if  the  brine  is  mixed 
with  finely  powdered  ammonium  bicarbonate,  the  less  soluble  sodium  bicarbonate 
separates  as  a  crystalline  powder,  and  the  supernatant  liquid  is  a  watery  solution  of 
ammonium  chloride  :  2NaCl  4-  2NH4.H.C03  =  2NaHC03  -t-  2NH4C1. 

As  sodium  bicarbonate  passes  into  sodium  carbonate  at  dull  redness : 
2NaHCO,  =  Na,CO,  +  H,O  +  CO,, 


340  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

we  have  here  the  foundation  of  a  process  for  the  manufacture  of  soda,  where,  of  course, 
the  ammonia  required  for  precipitating  fresh  quantities  of  common  salt  must  be  re- 
covered by  means  of  lime  or  magnesia : 

2NH4C1  +  Ca(OH)8  =  2NH3  +  CaCl2  +  2H20. 

Dyar  and  Hemming  carried  out  the  industrial  production  of  soda  from  common 
salt  and  ammonium  bicarbonate  in  England  as  early  as  1838.  The  next  process,  of 
Schloesing  and  Holland,  for  which  they  took  out  a  British  patent  in  1855,  contained 
certain  improvements,  but  it  was  essentially  similar  to  the  process  above  described. 
Schloesing  used  for  the  manufacture  strong  brine,  which  was  saturated  with  ammonia 
and  carbon  dioxide.  Ammonia  and  carbonic  acid  were  let  act  upon  the  brine;  the 
separation  of  the  precipitated  bicarbonate  from  the  liquid  was  effected  by  means  of  a 
centrifugal  machine.  If  the  soda  is  to  be  perfectly  pure,  the  salt  is  washed  in  the 
centrifugal  machine  with  a  solution  of  bicarbonate.  The  calcination  of  the  bicarbonate 
and  the  consequent  conversion  into  soda  are  effected  in  a  cylinder  of  sheet-iron. 
The  carbon  dioxide  is  collected  as  it  escapes.  The  manufactory  of  Schloesing  and 
Holland,  at  Puteaux,  near  Paris,  ran  from  1855  to  1857,  and  yielded  25  tons  of 
ammonia  soda  monthly. 

After  the  ammonia-soda  process  had  been  attempted  with  more  or  less  success  by 
Gerstenhoefer  of  Freiberg,  Honigmann  of  Aachen,  and  many  others,  E.  Solvay  of 
Brussels  introduced  it  in  his  works  at  Couillet  in  Belgium,  and  subsequently  at 
Varangeville-Dombasle,  near  Nancy. 

The  conversion  of  sodium  chloride  into  bicarbonate  is  effected  in  three  connected 
pieces  of  apparatus,  the  first  serving  to  prepare  the  concentrated  brine,  the  second  for 
saturating  the  solution  with  ammonia,  and  the  third  for  decomposing  the  ammoniacal 
liquid  by  means  of  carbon  dioxide.  The  apparatus  in  which  the  brine  is  saturated  with 
ammonia  is  a  cistern  of  tin-plate,  or  of  wood  lined  with  lead,  taller  than  it  is  wide.  It 
has  a  perforated  false  bottom,  beneath  which  the  ammoniacal  gas  enters,  which  is  divided 
by  the  holes  into  many  separate  bubbles,  and  is  easily  absorbed  by  the  brine.  The 
liquid  increases  considerably  in  volume,  whilst  its  density  falls  from  37-6°  Tw.  to  18° 
to  21°  Tw.  As  considerable  heat  is  liberated  on  the  absorption  of  the  ammonia,  the 
saturated  solution  is  first  passed  into  a  vessel,  where  it  is  cooled  by  a  stream  of  cold 
water  flowing  in  a  worm,  and  then  into  the  absorber,  in  which  it  is  decomposed  by 
carbonic  acid.  This  gas  may  be  produced  in  any  convenient  manner. 

As  an  absorber  there  is  used  a  cylinder  as  shown  in  section  in  Fig.  302.  In  this 
cylinder,  a,  lie  a  number  of  finely  perforated  plates,  b,  of  the  shape  of  the  segment  of  a 
globe.  Fig.  303  is  such  a  plate  seen  from  above.  In  a  there  are  also  a  number  of 
plates,  c,  with  one  hole  or  a  few  holes,  which  give  passage  to  the  gas  and  the  saturated 
solution,  without  allowing  the  freshly  entering  liquid  to  mix  with  that  at  the  bottom, 
which  is  nearly  saturated.  In  the  margin  of  the  perforated  plates  there  are  teeth,  z, 
cut  out  so  that  the  liquid  and  the  gas  may  pass  through  when  the  apertures  are  partly 
choked.  The  absorber  is  always  kept  nearly  full  of  liquid  whilst  carbon  dioxide  is 
forced  in  from  below  through  the  pipe  d.  By  this  means  the  gas  is  not  only  kept  in 
very  intimate  contact  with  a  liquid  moving  in  the  opposite  direction,  but  it  also  exerts, 
in  consequence  of  its  expansion,  a  considerable  mechanical  power,  and  consumes  thereby 
such  a  quantity  of  heat  that  the  heating  of  the  liquid  is  prevented  (as  would  otherwise 
be  the  case  on  the  absorption  of  carbonic  acid  by  the  ammonia),  and  which  could  not  be 
otherwise  easily  avoided.  The  liquid  enters  through  a  pipe,  e,  at  about  half  the  height 
of  the  cylinder,  into  which  it  flows  out  of  a  trough,  so  that  its  level  is  kept  uniform, 
about  3  metres  from  the  upper  end  of  the  cylinder.  The  trough  is  closed,  and  is  con- 
nected with  the  upper  end  of  the  cylinder  by  a  tube,  which  maintains  an  equal  pressure 
in  both.  One  trough  can  supply  several  absorbers.  In  this  manner  the  liquid  is 
reserved  only  in  the  upper  half ;  it  sinks  down  very  slowly,  and  is  soon  saturated 


SECT.   III.] 


SODA. 


Fig.  304. 


with  carbonic  acid  suited  for  taking  up  all  the  ammoniacal  gas  which  the  gas  may  bring 
with  it  from  the  lower  part  of  the  absorber.  The  absorbers  must  be  so  high  that  at 
least  half  the  carbonic  acid  entering  from  below  is  absorbed,  and,  at  the  same  time,  all 
the  ammonia  contained  in  the  liquid  may  be  converted  into  bicarbonate.  A  height  of 
ii  to  1 6  metres,  when  the  gas  must  be  forced  in  at  a  pressure  of  i|  to  2  atmospheres, 
gives  the  best  results.  It  is  well  not  to  let  the  gas  enter  in  an  uninterrupted  current, 
as  an  irregular  motion 
prevents  the  bicarbonate 
separated  out  from  at- 
taching itself  to  any  one 
place.  The  liquid  satu- 
rated with  carbonic  acid 
is  best  allowed  to  run 
out  in  portions  every 
three  minutes ;  the  sus- 
pended bicarbonate  is 
collected  in  a  vacuum 
filter  and  washed  in  a 
very  small  quantity  of 
water.  In  a  cylinder, 
g  (Figs.  304  and  305), 
there  are  at  suitable 
distances  from  each 
other  a  number  of  round 
plates,  A,  with  openings 
at  the  centre  and  at  the 
circumference.  A  shaft, 
i,  passes  through  the 
cover  in  the  bottom  of 
the  cylinder  and  carries 
arms,  k,  with  scraping 
knives,  I,  which  push 
the  mass  lying  on  the 
plates  alternately  to- 
wards the  circumference 
of  one  plate  and  towards 
the  middle  of  the  fol- 
lowing, so  that  it  gra- 
dually passes  from  the 
top  plate  to  the  bottom 
of  the  cylinder.  The 
plates  are  hollow,  and 
can  be  heated  by  the  in- 
troduction of  steam  or 
hot  gases  of  any  origin 

from  the  pipe  ra.     The  Fig.  302.  Fig.  303-  Fig.  305. 

bicarbonate  is  intro- 
duced by  means  of  an  apparatus,  n,  which  resembles  the  body  of  a  grinding-mill,  with 
arms,  o,  which  move  slowly.  It  is  always  kept  full,  so  that  the  carbonic  acid  may  not 
escape  here.  The  dried  mass  arrives  at  the  bottom  of  the  cylinder  in  a  finely  ground 
state,  fit  for  packing.  The  gases  expelled  on  drying  escape  by  a  tube,  r,  in  the  cover. 
If  hollow  plates  are  not  used  the  hot  gas  may  be  passed  directly  through  the  cylinder. 


| 

Fig.  302. 


342 


CHEMICAL   TECHNOLOGY. 


[SECT.    III. 


Fig.  307. 


Another  drying  apparatus  suitable  for  the  production  of  soda  consists  of  an  iron  pan,  s 
(Fig.  306),  closed  with  a  cover,  through  which  passes  a  vertical  shaft  in  a  stuffing-box. 
The  shaft  carries  arms  with  scrapers,  which  stir  up  the  bicarbonate  introduced,  whilst 
the  pan  is  raised  to  a  suitable  temperature  by  the  fire  placed  below. 

The  gas  expelled  in  both  these  apparatus  is  carried  by  an  air-pump  into  a  washing 
apparatus,  in  which  all  the  ammonia  is  retained.  If  soda  has  been  made,  the  carbonic 
acid  expelled  is  returned  to  the  absorbers.  From  the  ammonium  chloride  ammonia  is 
regenerated  by  lime. 

According  to  H.  Schreib,  in  the  present  way  of  working  not  more  than  60  per  cent,  of 
the  sodium  chloride  used  is  converted  into  bicarbonate.  The  ammonia  present  in  excess 
in  the  ammoniacal  lime  on  saturation  with  carbonic  acid  does  not,  after  its  conversion  into 
ammonium  bicarbonate,  enter  into  the  desired  reaction  with  the  sodium  chloride,  but 
subsides  as  ammonium  bicarbonate.  To  effect  a  better  utilisation  both  of  the  salt  and 
of  the  apparatus,  sodium  chloride  in  a  solid  form  is  introduced  into  the  ammoniacal 
brine  used  in  the  ammonia-soda  process,,  during  its  saturation  with  carbonic  acid  in  the 
carbonisation  apparatus.  In  proportion  as  sodium  bicarbonate  is  deposited,  sodium 
chloride  is  dissolved,  and  this  is  converted  into  sodium  bicarbonate  by  the  ammonium 
bicarbonate  formed  in  the  solution,  richer  in  salts  by  the  continuous  passage  of  the 

carbonic  acid.  In  this  manner  it  is  said  that  about  80 
per  cent,  of  the  salt  is  converted  into  sodium  bicarbonate. 
For  introducing  the  salt  the  pan,  A,  containing  the 
ammoniacal  brine  (Fig.  307)  is  connected  with  the  brine 
pan,  B,  by  the  pipes  d  and  b.  If  solid  salt  is  to  be  intro- 
duced the  cock  c  is  closed  and  air  is  forced  in  through 
the  pipe  a,  so  that  all  liquid  is  forced  out  of  the  pan,  B. 
If  the  cock  e  is  also  closed  we  may,  after  the  com- 
pressed air  has  been  let  out  through  the  pipe  b,  introduce 
solid  salt  into  B  through  the  man-hole,  o.  The  man- 
hole is  then  closed,  and  the  connection  of  A  and  B  is  re- 
established by  opening  the  cocks.  The  passage  of  the 
air  containing  carbonic  acid  promotes  the  circulation 
both  in  A  and  B,  The  sodium  bicarbonate  thus  obtained 
is  separated  from  the  liquid  in  the  ordinary  manner  and 
converted  into  soda,  whilst  the  filtrate,  which  chiefly 
contains  ammonium  and  sodium  chloride  (if  solid  salt  is  present),  is  saturated  with 
ammonium  carbonate  up  to  20  to  25  per  cent.  Sodium  chloride  passes  into  solution  and 
ammonium  chloride  separates  out.  The  reaction  is  assisted  by  agitation  and  strong 
cooling.  After  the  end  of  the  action  the  solid  sal-ammoniac  is  filtered  out.  The  filtrate, 
which  contains  20  to  25  per  cent,  ammonium  carbonate,  24  per  cent,  sodium  chloride, 
and  9  per  cent,  ammonium  chloride,  is  treated  with  carbon  dioxide  in  the  apparatus, 
A,  and  returns  to  the  circuit  of  the  manufacture.  There  is  then  again  formation 
of  sodium  bicarbonate  and  the  above-mentioned  lye  of  sodium  chloride  and  ammonium 
chloride,  which  is  anew  treated  with  common  salt  and  ammonium  carbonate.  From  the 
sal-ammonium  obtained,  ammonium  carbonate  is  prepared  by  treatment  with  ground 
calcium  carbonate,  and  as  such  it  is  introduced  into  the  apparatus,  A. 

Weldon  attempts  to  combine  the  ammonia-soda  and  the  Leblanc  process  by 
saturating  a  saturated  solution  of  salt-cake  with  ammonia  and  then  with  carbonic  acid, 
whilst  solid  salt-cake  is  further  added. 

According  to  G.  Carey  and  F.  Hurter,  for  the  same  purpose  a  saturated  solution  of 
salt-cake  at  50°  to  60°  is  freed  from  iron,  lime,  and  free  sulphuric  acid  by  a  certain 
quantity  of  soda.  The  filtered  solution  is  let  cool  down  to  38°  and  treated  with  am- 
monia, 24  to  25  parts  qf  which  come  to  100  parts  of  salt-cake.  The  temperature  of 


SECT,  in.]  SODAi  343 

the  solution  must  never  fall  below  32°,  as  otherwise  sodium  sulphate  crystallises  out; 
and  never  rise  above  38°,  as  otherwise  the  pressure  required  for  completing  the  reaction 
would  be  inconveniently  high.  So  much  carbonic  acid  is  then  introduced  that  am- 
monium carbonate  is  formed.  It  is  convenient  to  pass  in  carbonic  acid  as  soon  as  the 
liquid  is  ammoniacal,  as  sodium  sulphate  is  more  soluble  in  solutions  of  ammonium 
carbonate  than  in  ammonia.  As  soon  as  ammonium  monocarbonate  is  formed,  it  is 
necessary,  in  order  to  complete  the  reaction,  to  introduce  carbonic  acid  under  pressure. 
When  sodium  bicarbonate  separates  out  the  solution  is  let  cool.  The  bicarbonate 
is  washed  and  freed  from  the  mother  liquor  by  pressure.  From  the  residual  solution, 
which  contains  ammonium  sulphate  and  carbonate  and  sodium  sulphate,  the  ammonia  is 
recovered  by  suitable  means. 

Whether  the  proposal  of  the  Croix  Company  to  use  trimethylamine  instead  of  am- 
monia in  the  production  of  alkaline  carbonates  can  be  used  to  advantage  appears 
doubtful. 

Hasenclever  (1880)  gives  a  comparative  table  of  the  cost  of  the  two  processes, 
which  shows  a  balance  in  favour  of  the  ammonia  method  to  which  must  be  added  on 
both  sides  repairs,  lighting,  salaries,  general  expenses,  &c.  If  we  disregard  the  bye- 
products,  ammonia  soda  is  cheaper  than  Leblanc  soda,  and  the  first  cost  of  the  installa- 
tion and  the  outlay  for  repairs  are  lower.  On  the  other  hand,  the  Leblanc  process  gives 
a  greater  scope  in  sales,  if  sulphuric  acid  and  salt-cake  happen  to  be  in  better  demand 
than  soda,  or  if  chloride  of  lime  and  sulphur  are  more  marketable  than  hydrochloric 
acid ;  whilst  the  ammonia-soda  process  does  not  furnish  any  intermediate  products. 
Most  German  establishments  work  with  rock-salt ;  if  cheap  brine  is  accessible,  the 
ammonia  soda  is  in  a  better  position,  except  the  price  of  fuel  at  the  spot  in  question  if 
too  high. 

Cryolite  Soda. — Soda  is  obtained  from  cryolite,  which  is  opened  up  by  heating 
with  lime — - 

Na6Al2F12  +  6CaO  =  6CaF2  +  Na6Al206. 

The  latter  compound  is  soluble  in  water  when  alumina  is  deposited,  and  is  utilised 
in  the  state  of  alum;  whilst  soda  remains  in  solution.  In  1867  five  German  alkali 
works  consumed  7500  tons  cryolite,  and  produced  from  it  5500  tons  of  soda-ash.  The 
Pennsylvania  Salt-manufacturing  Company  consumes  yearly  in  its  works  at  Natrona, 
near  Pittsburg  (1876),  1800  tons  of  cryolite.  More  and  more  accessible  sources  of 
cryolite  are  greatly  to  be  desired. 

Soda  from  Sodium  Sulphide. — If  moist  carbonic  acid  is  passed  over  sodium  sul- 
phide (obtained  by  igniting  salt-cake  with  ground  coke),  sodium  carbonate  is  formed 
with  the  liberation  of  H2S — 

Na2S  +  C02  +  H20  =  H2S  +  Na2COy 
The  process  is  not  likely  to  survive. 

Caustic  Soda. — Since  the  year  1851  caustic  soda  has  become  an  article  of  com- 
merce, either  as  a  very  strong  lye  or  more  frequently  as  fused  hydrate  (caustic  soda),  and 
it  is  manufactured  on  a  large  scale.  It  is  often  still  prepared  by  treating  dilute  solutions 
of  crude  soda  (black-ash)  with  caustic  lime:  Na2C03  +  Ca(OH)2  =  CaCO3+  2NaOH. 
The  calcium  carbonate  formed  in  quantity  in  this  process  is  mixed  with  gypsum,  and 
serves  for  the  production  of  writing-  or  marking-chalk.  In  order  to  economise  the  fuel 
for  evaporating  such  dilute  solutions  the  process  of  Dale  is  sometimes  imitated,  who 
used  the  dilute  lye  to  feed  his  steam-boilers  and  thus  brought  it  up  to  sp.  gr.  1-24 
to  1-25.  The  lye  is  then  further  concentrated  in  cast-iron  pans  up  to  sp.  gr.  1-9,  at 
which  strength  it  solidifies  on  cooling. 

G.  Lunge  sought  to  determine  the  limits  of  the  conversion  of  sodium  carbonate 
into  sodium  hydroxide  by  treatment  with  lime.  At  the  common  atmospheric  pressure 
the  experiments  gave  the  following  numbers  : — 


344  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

After  causticising  in  the  state  of 

Before  causticising.  NaOH  per  100  parts  Soda. 

Per  cent.  Na2COj.                  Specific  Gravity.  I.  II. 

2            ...             I -022  at  15°  ...  99-4  parts         ...            99-3  parts 

5            ...         •    1-052    „  ...  99 'o      »            —            99 '2 

10           ...            i '107    „  ...  97 '2      »            ».            97  '4 

12            ...            1-127    „  ...  96-8      „            ...            96-2 

14            ...            1-150    „  ...  94 '5      »            •••            95 '4 

16            ...             1-169  at  30°  ...  937      n            —            94'O 

20            ...            1-215    „  907      »  •••            9i  'o     „ 

Corresponding  experiments,  conducted  under  pressure  at  148°  to  153°,  gave — 

Before  causticising.  After  causticising  there  are  out  of 

ioo  parts  Soda  as  NaOH. 
Per  cent.  NajjCO,.  Specific  Gravity.  I.  II. 

10            ...            1-107  at  15°  ...  97-06  parts       ...            97-5  parts 

12             .„             I-I27     „  ...  96-35      96-8      „ 

14            ...            I'i5°    .1  •••  95'6       „           ...            96-6      „ 

16            ...            1-169  at  30°  ...  95'4       i,           .-            94'8      „ 

20            ...            1-215    „  "...  91 '66     „           ...            91-61    „ 

Hence  the  application  of  high  pressures  in  causticising  offers  no  perceptible 
advantage.  A  more  thorough  agitation  than  now  commonly  takes  place  is  to  be 
recommended. 

The  use  of  lime  for  converting  soda  into  caustic  has  been  abandoned  in  many  estab- 
lishments, and  caustic  soda  is  at  once  produced  in  the  process  of  manufacture.  This  is 
effected  by  somewhat  increasing  the  quantity  of  coal  added  to  the  mixture  of  salt-cake 
and  limestone,  and  lixiviating  the  ball-soda  at  once  with  water  at  50°.  After  the  lye  has 
been  let  settle  it  is  quickly  concentrated  to  sp.  gr.  1-5,  when  sodium  carbonate,  sulphate, 
and  chloride  sink  to  the  bottom,  and  the  liquid  takes  a  brick-red  colour  (red  liquor), 
derived  from  a  peculiar  compound  of  sodium  and  iron  sulphides.  The  lye  is  then  heated 
in  large  cast-iron  pans,  and  from  3  to  4  kilos,  of  soda-saltpetre  are  added  for  every 
ioo  kilos,  of  caustic  soda  to  be  produced.  As  the  water  escapes,  the  soda-saltpetre 
reacts  upon  the  sodium  sulphide  and  the  sodium  cyanide,  which  is  always  present,  and 
there  is  a  plentiful  evolution  of  ammonia  and  nitrogen.  A  part  of  this  ammonia  is  due 
to  the  decomposition  of  the  cyanides,  whilst  another  and  larger  portion  is  a  consequence 
of  the  oxidation  of  the  sulphides,  when  water  is  decomposed,  and  the  hydrogen  reduces 
the  nitric  acid  to  ammonia.  When  the  evaporated  mass  reaches  dull  redness,  finely 
divided  graphite  is  seen  on  its  surface. 

For  the  oxidation  of  sulphides  in  the  production  of  caustic  soda  G-.  Lunge  gives  the 
following  advice,  based  upon  comprehensive  experiments.  All  sodium  sulphide  is  first 
oxidised  to  thiosulphate  by  atmospheric  oxygen.  Even  if  this  process  were  not  less 
costly  than  nitre,  it  would  be  preferable,  as  the  iron  of  the  vessels  would  be  less 
attacked.  Thiosulphate  is  oxydised  by  the  air  only  at  high  temperatures,  and  slowly, 
since  it  is  first  split  up  into  sodium  sulphide  and  sodium  sulphite.  The  oxidation  is 
therefore  hastened  by  adding  nitre.  It  is  useless  to  do  this  at  temperatures  at  which 
the  thiosulphate  has  not  been  decomposed ;  the  practical  rule  would  be  to  begin  the 
addition  of  nitre  as  soon  as,  on  further  raising  the  temperature,  a  reaction  for  Na,S 
appears,  and  then  to  add  gradually  small  quantities,  thus  preventing  the  nitre  from 
coming  in  direct  contact  with  the  iron,  and  preventing  waste  of  the  former  and  injury 
to  the  latter.  This  method  seems  to  present  other  advantages.  The  addition  of  nitre 
must  cease  as  soon  as  neither  sodium  sulphide  nor  thiosulphite  is  present,  which  occurs 
at  about  300°  to  360°.  In  this  manner  we  reach  the  most  favourable  result — the  forma- 
tion of  ammonia  as  the  main  reaction.  Theoretically  it  would  be  the  more  advantageous, 
as  the  ammonia  might  be  recovered — a  result  which  should  not  be  pronounced  cb  priori 
impossible;  but  there  is  little  immediate  prospect  of  an  economical  solution  of  the 
problem.  "We  have,  then,  all  the  sulphur  as  sulphite,  or  a  little  of  it  as  sulphate ; 


SECT.    III.] 


SODA. 


345 


by  fishing  out  the  salts,  a  part  of  the  sulphite  can  be  removed  along  with  the 
sulphate ;  the  main  bulk,  however,  must  be  oxidised  during  fusion,  preferably  not  by 
nitre,  which  would  chiefly  be  decomposed  into  nitrogen,  but  by  forcing  in  a  current 
of  air. 

The  following  analyses  are  obtained  from  some  works  in  which  ball-soda  lye,  previously 
desulphurised  by  means  of  air,  is  agitated  during  causticising  by  means  of  a  current  of 
air.  I.  is  desulphurised  crude  lye;  crystallises  at  20*5°;  becomes  clear  at  24°;  sp.  gr. 
at  24°,  1-302  ;  boils  at  120°.  II.  Lye  I.  diluted  and  causticised;  liquid  clear,  except  a 
small  residue  of  iron  oxide;  sp.  gr.  at  20°,  1*1338  ;  boiling-point,  110°.  III.  Lye  II., 
concentrated  to  45°,  before  the  addition  of  nitre;  clear,  except  an  unimportant  grey 
residue;  sp.  gr.  at  20°,  1*301  ;  boiling-point,  120°.  IV.  Lye  III.,  evaporated  after  the 
addition  of  nitre,  and  clarified,  ready  for  the  melting-pan;  sp.  gr.  at  18*5°,  1-5417; 
boiling-point,  150°.  V.  Salt  fished  out  during  evaporation  of  III.;  greyish- white, 
uniform,  soluble  in  water ;  all  but  o*  i  per  cent,  of  residue  (chiefly  ferric  oxide)  soluble. 
VI.  Salt  deposited  on  standing  from  IV.  in  settling  cistern.  About  a  quarter  of  the 
whole  was  removed  as  a  liquid ;  there  remained  a  dirty  mass,  which  was  mixed  up. 




Causticised  with  a  Current,  of  Air. 

I. 

Crude  Lye. 

II. 

Caustic  Lye. 

III. 

Evaporated 
before  adding 
Nitre. 

IV. 
Melting  Lye. 

V. 

Fishing 
Salts. 

VI. 

Clarifying 
Salts. 

Grammes  per  Litre. 

Grammes  per  Kilo. 

NaOH                         ^ 
Na2CO, 

Na^S   . 

52-0 

295  "4 

0 

57 

4'5 
3*i 

trace 
94i*3 

IO2'5 
33-9 
O 
2-9 

2*5 
1*4 

trace 
991-6 

267-1 
77-2 
O 

7*i 

6-7 
3*6 

trace 
939  '3 

75*-6 
34*1 

0 

io-6 
5-6 

2*5 

io'6 
47 

722-0 

26IT 

365-6 
0 

5-6 
4*1 
38-9 
5*2 
0 
I'O 

o 

318-5 

283-9 
241'! 
O 

6-0 
71-1 
92-1 
4*4 

0 
6-2 

0 

295-2 

Na2S2Os 
Na28O8 
Na2S04 

NaUl  . 

NaN02 
Insoluble 
Na4FeCy, 
Water 

Total  . 

1302-0 

II33-8 

1301-0 

IS4I7 

lOOO'O 

lOOO'O 

Deacon  and  Hurter  for  decomposing  sodium  sulphide  pass  a  weak  electric  current 
through  the  lye.  The  sulphur  is  deposited  at  the  anode,  which  is  kept  clean  by 
brushing ;  at  the  kathode  there  is  formed  a  corresponding  quantity  of  sodium  hydrate. 
Stronger  currents  (30  to  50  amp.  per  square  metre  of  electro)  convert  the  sulphide 
at  once  into  sulphate.  To  avoid  polarisation  they  use  alternating  currents  or  movable 
electrodes. 

Caustic  soda  produced  in  England  (1875)  contained— 

70  per  cent. 
89-600 
2-481 
3-9I9 
3*4I9 
0*025 
0-304 
trace 


So-called  60  per  cent. 

Sodium  hydrate     . 

.     75-246 

carbonate 

•      2-536 

chloride    . 

.     17-400 

sulphate    . 

•      4-398 

sulphite    . 

0-027 

silicate      . 

.      0-297 

„       aluminate 

.      trace 

99-904 


99748 


Caustic  soda  has  its  chief  uses  in  the  soap  manufacture,  in  obtaining  and  purifying 
the  products  of  the  dry  distillation  of  lignite,  peat,  &c.,  for  the  purpose  of  obtaining 
paraffine,  solar  oil,  and  phenol ;  for  purifying  petroleum,  for  preparing  soluble  sodium 


346 


CHEMICAL  TECHNOLOGY. 


[SECT.  iii. 


silicate  (soluble  glass) ;  and  of  late  in  considerable  quantities  in  the  production  of  wood- 
cellulose  of  alizarine,  resorcine,  &c. 

The  subjoined  table  shows  the  actual  caustic  soda  contained  in  lyes  of  different 
specific  gravities  at  15° : — 


Specific  Gravity. 

Banine". 

Twaddell. 

Per  cent. 
NaOg. 

Per  cent. 
NaOH. 

i  cubic  metre  contains  kilos. 

Na20. 

NaOH. 

•007 

I 

1*4 

0-47 

0-61 

4 

6 

•029 

4 

5-8 

2'IO 

2-71 

22 

28 

•045 

6 

9-0 

3-IO 

4-00 

32 

42 

•060 

8 

I2'O 

4'10 

5  '29 

43 

56 

•075 

10 

IS'O 

5-08 

6-55 

55 

70 

•091 

12 

18-2 

6  -20 

8-00 

68 

87 

•108 

14 

21*6 

7-30 

9-42 

81 

104 

•125 

16 

25-0 

8-50 

10-97 

96 

123 

•142 

18 

28-4 

9-80 

12-64 

112 

144 

I-l62 

20 

32-4 

11-14 

H'37 

129 

167 

1-180 

22 

36-0 

-   12-33 

IS'PI 

146 

188 

I"20O 

24 

40  'o 

1370 

17-67 

164 

212 

I'22O 

26 

44  -o 

iS'iS 

I9-58 

185 

239 

1-241 

28 

48-2 

1676 

2  1  '42 

208 

266 

I-263 

30 

52-6 

18-35 

23-67 

232 

299 

I-285 

32 

57-o 

20  -oo 

25-80 

257 

332 

I-308 

34 

61-6 

21-55 

27-80 

282 

364 

I-332 

36 

66-4 

23-20 

29-93 

309 

399 

i  '357 

38 

7I-4 

25-17 

32H7 

342 

441 

1-383 

40 

76-6 

27-10 

34-96 

375 

483 

1-410 

42 

82-0 

29-05 

37-47 

410 

528 

1-438 

44 

87-6 

31-00 

39-99 

446 

575 

1-468 

46 

93  '6 

33-20 

42-83 

487 

629 

1-498 

48 

99-6 

3570 

46-15 

535 

691 

i  -530       ' 

50 

106-0 

38-00 

49-02 

58i 

750 

Sodium  Bicarbonate.* — NaHC03  is  obtained  by  passing  washed  carbon  dioxide 
through  a  solution  of  sodium  carbonate.  If  the  solution  is  concentrated,  the  bicarbonate 
separates  out  as  a  crystalline  powder ;  if  it  is  dilute,  large  crystals  are  obtained.  As 
carbonic  acid  is  absorbed  slowly  by  the  solution,  it  is  more  advantageous  to  let  it  act  upon 
crystallised  or  partly  effloresced  sodium  carbonate.  An  intimate  mixture  is  made  of  i 
part  crystallised  sodium  carbonate  and  4  parts  of  the  effloresced  salt  or  a  mixtui*e  of 
equal  weights  of  both,  and  it  is  saturated  either  with  the  carbonic  acid  of  fermentation 
or  with  that  obtained  on  burning  lime.  Where  carbonic  acid  issues  from  the  earth  the 
process  is  greatly  simplified.  The  bicarbonate  of  the  ammonia-soda  process  generally 
contains  ammonia. 

In  the  production  of  sodium  bicarbonate  from  ordinary  soda  crystals  (dekahydrated) 
the  product  retains  all  the  impurities  of  this  material ;  hence  Carey  took  the  mono- 
hydrate  as  a  starting-point.  H.  Gaskell  and  F.  Hurter,  of  Widnes,  went  further,  and 
converted  the  anhydrous  neutral  sodium  carbonate  into  bicarbonate  by  simultaneous 
treatment  with  watery  vapour  and  carbonic  acid. 

Sodium  bicarbonate  crystallises  in  monoklinic  tables  ;  it  has  a  faintly  alkaline  reac- 
tion, and  on  exposure  to  70°  or  in  solution  on  boiling  it  loses  half  its  carbonic  acid 
and  returns  to  monocarbonate.  In  dry  air  it  is  gradually  converted  into  sesqui- 
carbonate;  100  parts  water  dissolve  at  o°  6*0  parts,  and  at  15°  8-85  parts  of  sodium 
bicarbonate.  It  is  used  for  developing  carbonic  acid  in  the  manufacture  of  effervescing 
drinks,  in  the  preparation  of  unfermented  bread  (with  hydrochloric  acid,  or  acid  calcium 
phosphate),  for  precipitating  alumina  from  the  solution  of  sodium  aluminate  (in  the 
cryolite  and  bauxite  industries),  and  in  the  preparation  of  baths  for  gilding  and 
platinising.  It  has  of  late  been  proposed  for  ungumming  silk  and  scouring  wool,  as  it 
attacks  the  fibres  less  than  soap  or  ammonia. 

*  Hydrocarbonate,  carbonate  of  soda  of  pharmacy  and  cookery. 


SECT,  in.]      CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES. 


347 


CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES. 

For  obtaining  chlorine,  pyrolusite  (manganese  peroxide)  is  heated  along  with  hydro- 
chloric acid  :  MnO2  +  4.HC1  =  MnCl3  +  2H20  4-  C12.  As  developers  there  are  used  large 
stone-ware  vessels,  A  (Fig.  308),  fitted  with  a  wide  opening,  a,  for  filling  and  emptying 
and  with  narrower  tubulures,  b,  in  which  the  delivery  pipes  are  inserted.  Heat  is 
applied  by  means  of  steam.  To  this  end,  several  such  vessels  are  set  in  a  chest,  B,  of 
wood  or  masonry,  with  a  wooden  lid,  so  that  only  the  necks  and  the  delivery-pipes  pro- 
ject outside.  The  joints  of  the  chest  are  carefully  closed  with  clay  or  felt  at  r,  in  order 
to  prevent  the  loss  of  the  steam  which  is  led  into  the  chest  from  the  boiler.  The  lye 
of  manganese  chloride  is  let  out  at  c.  On  the  large  scale  a  trough  is  used,  made  up  of 
plates  of  sandstone  cemented  together  or  hollowed  out  of  a  block  of  sandstone  and 
saturated  with  hot  tar. 

If  a  mixture  of  manganese  peroxide,  salt,  and  sulphuric  acid  is  used — 

2NaCl  +  Mn02  +  2H2SO4  =  Na2SO4  +  MnS04  +  2H20  +  C12, 
a  strong  heat  is  needed.     A  pan  is  used,  the  lower  part  of  which,  b  (Fig.  309),  is  made 
of  cast  iron  and  the  upper  part,  d,  of  lead ;  both  parts  are  secured  together  at  a. 

At  the  Josephsthal  paper  works  there  is  used  a  stout  cast-iron  pan,  A  (Fig.  310), 
its  outflow  pipe,  D,  being  closed  with  a  wooden  plug  luted  in  with  clay.  The  lead 


Fig.  309, 


Fig.  308. 


cylinder,  B,  which  is  screwed  on,  and  the  lid  of  which,  C,  carries  the  delivery-pipe,  gives 
room  for  the  materials  to  swell  up.  The  production  of  chlorine  takes  place  in  A  ;  the 
iron  is  but  little  attacked  as  long  as  an  excess  of  manganese  is  present.  When  the 
pan  is  eaten  through,  a  new  one  is  quickly  and  inexpensively  substituted.  The  lead 
cylinder  is  made  very  stout  at  the  lower  part,  where  it  is  most  likely  to  be  attacked. 
The  upper  part,  which  does  not  come  in  contact  with  the  liquor,  soon  becomes  coated 
with  a  dense  layer  of  lead  chloride,  and  is  then  no  longer  attacked.  The  spent  liquor 
is  run  off  at  D,  and  the  vessel  is  then  well  rinsed  out  with  water. 

For  work  on  the  large  scale  the  recovery  of  the  manganese  is  important. 

Dunlop's  process,  which  came  into  use  at  the  St.  Rollox  works  at  Glasgow,  is  based 
upon  the  fact,  first  observed  by  Forchhammer,  that  carbonate  of  manganese,  when  heated 
to  260°,  is  converted  into  peroxide  of  manganese  ;  that  is,  the  carbonic  acid  is  driven 
off,  and  the  compound,  2MnO3  +  MnO,  obtained.  The  process  consists  in  the  following 
operations  : — 

i.  Conversion  of  the  manganese  chloride  into  manganese  carbonate. 


348  CHEMICAL  TECHNOLOGY.  [SECT.  HI. 

2.  Conversion  of  the  carbonate  into  peroxide  of  manganese. 

To  the  chlorine  preparation  residues,  when  they  have  become  clear,  either  chalk  or 
milk  of  lime  is  added  to  neutralise  the  excess  of  acid  and  precipitate  the  oxide  of  iron. 
This  precipitate  having  settled,  the  clear  liquid,  a  rather  pure  solution  of  manganous 
chloride,  is  poured  into  shallow  troughs  and  intimately  mixed  with  finely  powdered 
chalk.  The  magma  thus  formed  is  transferred  for  further  decomposition  to  a  large 
cast-iron  trough,  27  metres  long  by  3  metres  wide.  Parallel  to  the  length  of  this 
vessel,  a  stout  wrought-iron  axle  is  carried,  to  which  are  fitted  cast-iron  branches 
serving  as  stirrers.  The  axle  passing  through  stuffing  boxes  at  each  end  of  the  trough 
gears  with  a  motive  power,  whereby  the  stirrers  are  caused  to  keep  the  chalk  constantly 
suspended  in  the  manganese  solution.  High-pressure  steam  is  conveyed  into  the  trough 
and  aids  decomposition.  The  manganese  carbonate  obtained  is  freed  from  calcium 
chloride  by  washing,  and,  having  been  well  drained,  is  calcined  in  a  peculiarly  con- 
structed furnace,  in  which  the  carbonate  is  first  dried  on  a  higher  stage,  and  then 
transferred  to  a  lower  and  hotter  stage,  where  oxidation  is  commenced.  The  oxidation 
is  completed  at  the  lowest  stage  of  the  furnace,  to  which  plenty  of  air  is  admitted. 
The  fire-place  is  constructed  to  admit  of  the  regulation  of  the  heat  with  great  nicety, 
because  too  high  a  temperature  would  cause  the  formation  of  protosesquioxide,  and  too 
low  a  temperature  would  leave  the  carbonate  undecomposed. 

Gatty 's  Process. — In  this  process  the  residues  are  converted  into  manganese  nitrate, 
which  is  next  decomposed  by  heat.  The  residues  are  evaporated  to  the  consistency  of 
a  syrup,  and  mixed  with  sodium  nitrate  : — 

To  76  kilos,   of  manganese  chloride  ) 

and  to  95  kilos,  of  manganese  sulphate  \ Io6  kllos'  of  sodlum  mtrate  are  taken' 
The  mixture  is  dried,  and  then  heated  to  a  dull  red  heat  in  an  iron  retort,  the  fumes  of 
nitric  acid  given  off  being  used  in  the  manufacture  of  sulphuric  acid.  The  residue  in 
the  retort  consists,  according  to  the  salt  of  manganese  employed,  of  manganese 
peroxide,  and  sodium  chloride  or  sodium  sulphate ;  it  may  be  lixiviated  with  water  to 
obtain  the  manganese  peroxide  in  a  pure  state  if  sodium  sulphate  is  present. 

The  process  of  P.  W.  Hofmann  has  been  described  under  the  methods  for  the 
recovery  of  vat- waste. 

Fr.  Kuhlmann  proposes  to  transfer  the  oxygen  of  the  air  at  once  to  the  manganous 
oxide.  By  heating  manganese  nitrate  to  200°  there  are  formed  manganese  peroxide 
and  hyponitric  acid.  The  escaping  gases,  mixed  with  air,  are  conveyed  into  recently 
precipitated  manganous  hydroxide,  when  a  fresh  quantity  of  manganese  nitrate  is 
formed — 

Mn(OH)2  +  2N02  +  O  =  Mn(N03),  +  H2O, 
which,  when  heated,  furnishes  anew  manganese  peroxide  and  hyponitric  acid. 

Weldon's  Process. — Mr.  Walter  Weldon's  process  is  performed  by  means  of  an 
apparatus  comprising  five  vessels  arranged  at  successive  elevations,  so  that,  after  having 
been  pumped  up  to  the  highest  of  them,  the  liquor  operated  upon  can  afterwards 
descend  to  all  the  others  by  its  own  gravity.  The  lowest  of  these  vessels  is  a  well, 
which  is  furnished  with  a  mechanical  agitator.  The  slightly  acid  chloride  of  man- 
ganese liquor  with  which  the  process  commences  runs  from  the  stills  in  which  it  is 
produced  into  this  well,  and  is  there  treated  with  finely  divided  calcium  carbonate,  the 
action  of  which  is  facilitated  by  energetic  agitation.  When  the  neutralisation  of 
the  free  acid  which  is  at  first  contained  in  this  liquor  and  the  decomposition  of 
the  iron  and  aluminium  sesquichloride,  which  are  also  at  first  contained  in  it, 
are  completed,  the  liquor  is  pumped  up  into  settling  tanks,  placed  nearly  at  the 
top  of  the  apparatus,  and  known  as  the  "  chloride  of  manganese  settlers."  It 
now  consists  of  a  quite  neutral  mixed  solution  of  manganese  chloride  and  calcium 
chloride,  containing  in  suspension  considerable  quantities  of  calcium  sulphate,  and  small 


SECT,  in.]        CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.        349 

quantities  of  ferric  oxide  and  alumina.  These  solid  matters  rapidly  deposit  in  the 
chloride  of  manganese  settlers,  leaving  the  bulk  of  the  liquor  perfectly  bright  and 
clear,  and  of  a  faint  rose  colour.  The  next  step  is  to  run  off  the  clear  portion  of  the  con- 
tents of  the  settlers  into  a  vessel  immediately  below,  called  the  oxidiser.  This  is  usually 
a  cylindrical  iron  vessel  about  12  feet  in  diameter,  and  about  22  feet  deep.  Two  pipes 
go  down  nearly  to  the  bottom  of  the  oxidiser — a  large  one  for  conveying  a  blast  of  air 
from  a  blowing  engine,  and  a  smaller  one  for  the  injection  of  steam.  The  latter  is  for 
the  purpose  of  raising  the  temperature  of  the  contents  of  the  oxidiser  when  necessary ; 
for  sometimes  the  chloride  of  manganese  liquor  reaches  the  oxidiser  sufficiently  hot — 
between  130°  and  160°  or  170°  F.  Immediately  above  the  oxidiser  is  a  reservoir 
containing  milk  of  lime.  The  oxidiser  having  received  a  charge  of  clear  liquor  from 
the  settlers,  and  this  liquor  having  been  heated  up  to  the  proper  point  if  it  was  not 
already  hot  enough,  blowing  is  begun,  and  milk  of  lime  is  then  run  into  the  oxidiser 
as  rapidly  as  possible,  until  the  nitrate  from  a  sample  taken  at  a  tap  placed  nearly  at 
the  bottom  of  the  oxidiser  ceases  to  give  a  manganese  reaction  with  solution  of  bleach- 
ing-powder.  A  certain  quantity  of  milk  of  lime  is  then  added,  and  the  blowing 
continued  until  peroxidation  ceases  to  advance.  That  point  is  usually  attained  when 
from  about  80  to  85  per  cent,  of  the  manganese  present  has  become  converted  into 
peroxide.  The  contents  of  the  oxidiser  are  now  a  thin  black  mud,  consisting  of 
solution  of  calcium  chloride  containing  in  suspension  about  2  Ibs.  of  manganese 
peroxide  per  cubic  foot,  these  2  Ibs.  of  manganese  peroxide  being  combined  with 
varying  quantities  of  manganous  oxide  and  lime.  This  thin  mud  is  now  run  off 
from  the  oxidiser  into  one  or  other  of  a  range  of  settling  tanks  or  "  mud  settlers," 
placed  below  it,  and  is  there  left  at  rest  until  it  has  settled  as  far  as  it  will,  usually 
until  about  one-half  of  its  volume  has  become  clear.  The  clear  part  is  then  decanted, 
and  the  remainder,  containing  about  4  Ibs.  of  manganese  peroxide  per  cubic  foot,  is 
then  ready  to  be  used  in  the  stills.  There  it  reacts  upon  hydrochloric  acid,  liberating 
chlorine,  with  reproduction  of  exactly  such  a  residual  solution  as  was  commenced  with. 
With  that  solution  the  round  of  operations  is  begun  again ;  and  so  on,  time  after  time, 
indefinitely. 

The  extraordinary  simplicity  of  the  Weldon  process  ensures  it  the  preference  as 
against  other  methods  aiming  at  the  same  object,  and  it  is  almost  universally  em- 
ployed. According  to  Jetzler,  the  manganous  hydroxide,  after  being  washed  in  the  air, 
is  partly  oxidised  and  then  exposed  to  a  current  of  hot  air  whilst  suspended  in  the  lime- 
lye.  In  this  manner  a  more  rapid  and  complete  oxidation  is  effected  and  a  dry 
manganese  peroxide  is  obtained. 

According  to  the  more  recent  proposals  of  Weldon,  the  lyes  of  manganese  chloride 
are  evaporated  and  treated  either  separately  or  along  with  solid  calcium,  or  magnesium 
chloride,  or  with  magnesium  or  manganese  manganite  obtained  in  a  former  operation 
in  a  cylindrical  retort,  heated  from  without,  and  so  arranged  that  at  one  end  the 
powder  is  regularly  and  continuously  introduced,  whilst  the  solid  product  of  the 
reaction  is  taken  out  at  the  other.  The  retort,  E  (Figs.  311  and  312),  maybe  made  of 
fire-clay,  or  of  cast  iron,  or  of  both  materials.  It  seems  best  to  construct  the  retort 
of  fire-clay  for  the  chief  part  of  its  length,  and  only  to  make  the  part  where  the 
charge  is  introduced  of  cast  iron  for  a  short  extent.  The  outer  cylinder,  (7,  can  be 
made  of  wrought  iron  with  a  fire-clay  lining.  The  whole  rests  and  turns  on  the 
friction  rollers,  D.  Through  the  pipes  F,  heating-gas  enters  from  a  generator  into 
the  annular  combustion  chamber,  X,  and  the  air  necessary  for  combustion  through  the 
apertures,  e.  The  heating-gas  arrives  in  the  immovable  pipe,  J,  which  is  connected  by 
the  ring-shaped  conduit,  a,  with  the  tubes  F.  Air  enters  through  the  tube  K  into 
the  interior  of  the  retort.  E,  and  hereby  the  solid  product  of  the  reaction,  manganese 
and  magnesium  manganite,  is  emptied.  This  evacuation  is  facilitated  by  wings  placed 


35° 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


spirally,  fixed  on  the  axle,  n.  The  gases,  charged  with  the  chlorine  generated,  escape 
through  the  tube,  N  which  also  serves  for  charging  the  retort.  The  axles,  n  and  o, 
may  be  either  immovable,  or  may  turn  in  the  opposite  direction  to  the  retort,  E. 
The  products  of  combustion  issue  from  the  ring-shaped  combustion  chamber,  JT, 
through  the  apertures,  H,  into  the  fixed  smoke  chamber,  P.  The  manganite  obtained 
is  treated  with  hydrochloric  acid  for  the  production  of  chlorine  ;  the  lyes  are  evaporated 
dow-n  and  mixed  with  a  portion  of  the  manganite ;  they  are  again  conveyed  into  the 


-Fig.  311. 


Fig.  312. 


decomposition  chamber,  E.  The  hydrochloric  acid  is  thus  almost  completely  converted 
into  chlorine.  Working  results  on  this  modification  have  not  yet  been  made  known. 

For  the  utilisation  of  the  chlorine  residues,  Schaffner,  of  Aussig,  precipitates  the 
manganous  chloride  with  lime,  dries  the  precipitate,  and  calcines  it  in  a  reverbera- 
tory  furnace,  obtaining  protosesquioxide  of  manganese,  employed  with  iron  ore  in 
the  blast  furnace.  The  solution  of  calcium  chloride  simultaneously  obtained  is 
precipitated  by  sulphuric  acid,  yielding  the  material  known  as  annaline  ;  that  is  to 
say,  the  gypsum  used  in  paper  manufacture.  In  the  process  of  soda-making  from 
sodium  and  iron  sulphides,  as  suggested  by  Malcherbe  and  improved  upon  by  Kopp, 
for  the  oxides  and  carbonate  of  iron,  the  corresponding  manganese  compounds  may 
be  substituted.  Carbonate  of  manganese  may  be  used  to  convert  sodium  sulphide 
into  soda,  and  may  also  serve  for  the  preparation  of  permanganates.  A.  Leykauf 
suggests  that  the  residues  of  chlorine  manufacture  should  be  employed  to  form  a 
violet-coloured  paint,  known  as  Nuremberg-violet,  a  compound  of  ammonia,  oxide  of 
manganese,  and  phosphoric  acid.  In  England  the  residues  are  frequently  employed 
in  the  purification  of  coal-gas  and  as  disinfectants.* 

Of  the  processes  for  obtaining  chlorine  without  manganese,  the  most  important  is 
that  of  Deacon,  in  which  hydrochloric  vapours  are  oxidised  by  atmospheric  oxygen  ; 


Deacon  and  Hurter  found  that  the  decomposition  of  hydrochloric  acid  by  oxygen 
takes  place  at  a  much  lower  temperature  if  the  gaseous  mixture,  instead  of  simply 
passing  through  ignited  tubes  or  over  porous  substances,  is  led  over  heated  salts  of 
copper,  lead  (except  the  sulphate),  or  compounds  of  manganese.  The  most  efficacious 
are  the  compounds  of  copper  ;  so  that,  if  a  mixture  of  hydrochloric  acid  with  an  excess 
of  atmospheric  air  is  passed  over  porous  bodies,  soaked  in  solution  of  copper  sulphate 
and  heated  to  360°  to  400°,  all  the  hydrochloric  acid  is  burnt  to  chlorine  and  water. 
In  this  reaction,  which  begins  at  260°,  the  copper  sulphate  remains  unchanged  unless  the 
temperature  is  raised  too  high.  Not  until  about  425°  are  formation  and  volatilisation 
of  copper  chloride  perceptible.  The  power  of  resistance  as  well  as  the  efficacy  of 
the  copper  sulphate  can  be  intensified  by  joining  with  it  certain  salts  which  are  in 

*  Chlorine  residues,  as  long  as  they  were  procurable,  were  an  excellent  agent  for  the  precipitation 
and  purification  of  sewage.     See  Slater,  Sewage  Treatment,  p.  102. 


SECT,  in.]       CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.         351 

themselves  without  action  upon  the  gaseous  mixture,  e.g.,  potassium  or  sodium 
sulphate.  Numerous  experiments  showed  the  conditions  for  the  decomposition 
between  air  and  hydrochloric  acid  in  presence  of  copper  sulphate. 

1.  The  quantity  of  the  hydrochloric  acid  decomposed  by  i  mol.  copper  sulphate  in 
gaseous  mixture  of  similar  composition  and  at  the  same  temperature  depends  upon  how 
often  the  gaseous  molecules  pass  through  the  sphere  of  activity  of  the  copper  sulphate. 

2.  For  all  velocities  of  the  gases  in  transit  the  opportunity  for  efficacy  is  the  same 
for  long  tubes  of  the  same  section  in  one  and  the  same  time. 

3.  In  long  tubes  of  different  section  the  opportunities  for  action  are  alike  when  the 
speeds  of  the  currents  are  inversely  as  the  squares  of  the  diameters  of  the  tubes. 

4.  In  porous  masses  the  efficacy  increases  directly  as  the  rapidity. 

5.  Circumstances  being  otherwise  equal,  the  quantity  of  the  hydrochloric  acid  de- 
composed varies  with  the  square  root  of  the  number  expressing  the  proportion  between 
hydrochloric  acid  and  oxygen. 

6.  At  very  high  temperatures  a  little  copper  chloride  is  formed,  but  its  quantity  is 
in  no  proportion  to  the  quantity  of  chlorine  formed. 

7.  The  efficacy  of  the  copper  salt  extends  to  gaseous  molecules  not  in  contact  with 
the  salt ;  the  decomposition  of  the  hydrochloric  acid  takes  place  under  circumstances  in 
which  no  material  exchange  can  take  place  between  the  copper  salt  on  the  one  hand 
and  the  hydrochloric  acid  and  air  on  the  other. 

In  the  technical  execution  of  the  Deacon  process  the  hydrochloric  acid  is  either 
prepared  from  sodium  chloride  and  sulphuric  acid  in  an  ordinary  salt-cake  furnace  or  it 
is  liberated  from  aqueous  acid  already  obtained.  On  a  small  scale  the  latter  is  pre- 
ferable, as  in  this  manner  it  is  always  practicable  to  produce  a  current  of  hydrochloric 
acid  of  uniform  strength,  whilst  the  evolution  of  hydrochloric  acid  from  the  sulphate 
furnaces  is  very  rapid  at  first  and  then  becomes  very  slow.  On  the  large  scale  this 
defect  may  be  avoided  by  having  several  salt-cake  furnaces  in  serial  action,  so  that 
when  the  evolution  declines  in  one  the  activity  of  the  next  begins.  The  gas  obtained 
in  either  manner  is  immediately  mixed  with  a  quantity  of  air  which  contains  more 
oxygen  than  suffices  to  convert  all  the  hydrochloric  acid  into  chlorine,  and  is  passed 
through  heated  U-shaped  tubes  of  cast  iron,  which  supply  the  temperature  required 
for  the  process.  The  composition  of  the  gaseous  mixture  can  be  checked  at  any  time 
by  means  of  a  small  air-pump,  which  at  every  stroke  of  the  piston  forces  a  certain 
volume  of  the  gas  through  a  standard  soda-lye  coloured  with  litmus.  The  succeeding 
decomposition  furnace  consists  of  a  cast-iron  chest  in  which  are  chambers,  each 
provided  in  its  lower  part  with  a  grating,  or  false  bottom.  Upon  this  stand  in  the  first 
chamber,  and  also  in  the  second,  upright  drain-pipes  which  have  been  steeped  in  a  hot 
concentrated  solution  of  2  mols.  copper  sulphate  and  3  mols.  sodium  sulphate  and 
dried.  The  other  chambers  are  filled  with  fragments  of  brick  or  clay  balls  which  have 
been  treated  in  the  same  manner.  The  entire  furnace  is  enclosed  with  an  air-jacket  and 
this  again  with  a  jacket  of  masonry  traversed  by  fire-flues,  serving  to  keep  back  a 
part  of  the  radiant  heat  from  being  lost.  Another  part  is  restored  in  the  process 
itself  by  the  combustion  of  the  hydrochloric  acid.  The  pipes  serve  to  prevent  any 
obstruction  of  the  apparatus  by  ferric  oxide  or  chloride.  It  has  been  observed  that, 
especially  when  an  iron  apparatus  is  used  for  producing  and  conducting  hydrochloric 
acid,  the  acid  always  carries  with  it  ferric  chloride,  from  which  it  cannot  be  freed 
before  it  enters  the  decomposition  furnace.  In  this  it  deposits  the  iron  upon  the  copper 
sulphate,  either  as  chloride,  or,  if  the  formation  of  chlorine  has  already  set  in,  as 
pulverulent  ferric  oxide.  This  iron  dust  falls  out  of  the  drain-pipes  through  the 
grating  into  the  space  below,  where  it  is  easily  removed.  Deacon  has  recently 
removed  the  partition  walls  from  the  decomposition  furnace. 

After  the  gaseous  mixture  has  passed  through  the  decomposition  furnace,  it  consists 


352  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

of  chlorine,  nitrogen,  water,  excess  of  oxygen,  and  unburnt  hydrochloric  acid.  The 
latter  is  eliminated  as  the  gases  (the  temperature  of  which  has  been  previously 
reduced  by  means  of  cold  air)  are  passed  through  a  scrubber  charged  with  dilute 
hydrochloric  acid  and  water.  The  gas  is  then  freed  from  the  accompanying  water  by 
a  tower  charged  with  calcium  chloride,  or  preferably  a  coke-tower  in  which  sulphuric 
acid  trickles  down,  and  it  is  then  ready  for  use  in  the  chloride  of  lime  chambers.  Of 
course  the  drying  arrangement  is  superfluous  if  an  aqueous  liquid  is  to  be  saturated 
with  chlorine,  as  in  the  preparation  of  potassium  chlorate.  For  the  latter  purpose, 
Kunheim  uses  the  chlorine  obtained  by  Deacon's  method.  The  chlorine  is  so  completely 
absorbed  by  the  milk  of  lime  in  its  passage  that  mere  traces  are  present  in  the  escaping 
air.  The  draught  in  the  entire  plant  is  effected  by  any  suction  apparatus  placed  beyond 
the  chloride  of  lime  chambers. 

Of  other  methods  for  producing  chlorine,  the  following  deserve  notice : — 

1.  MacDougal,  Rawson,  and  Shanks's  process,  consisting  in  the  decomposition  of 
calcium  chromate  by  hydrochloric  acid,  the  result  being  the  formation  of  chromium 
and  calcium  chlorides,  and  the  evolution  of  free  chlorine — 

2CaCr04  +   i6HCl  =  Cr2Cl6  +  zCaCL,  +  3H20  +  6C1. 

158  parts  of  chromic  acid  yield  106  parts  of  chlorine.  The  chloride  of  chromium  is 
again  precipitated  with  carbonate  of  lime,  and  by  ignition  converted  into  chromate  of 
lime.  Only  three-eighths  of  the  chlorine  contained  in  the  hydrochloric  acid  is  given  up, 
while  manganese  yields  one-half. 

2.  Yogel's  method  of  decomposing  chloride  of  copper  by  heat.     3  mols.  of  chloride 
yield  i  mol.  of  chlorine ;  according  to  Laurens  the  process  is — 

2CuCl2  =  01,  +  Cu2Cl2. 

The  chloride  in  the  crystalline  state  is  mixed  with  half  its  weight  of  sand,  and  heated  in 
earthenware  retorts  to  200°  to  300°,  yielding  chlorine  gas,  while  the  remaining  proto- 
chloride  of  copper  is  re-converted  into  perchloride  by  the  action  of  hydrochloric  acid. 
Mallet  has  constructed  a  peculiar  rotating  apparatus  for  the  decomposition  of  this  salt, 
the  same  apparatus  serving  to  prepare  oxygen.  100  kilos,  of  cupric  chloride  yield  6  to 
7  cubic  metres  of  chlorine  gas. 

3.  Peligot's  method.     When  3  parts  of  bichromate  of  potassa  and  4  parts  of  con- 
centrated hydrochloric  acid  are  gently  heated,  the  fluid  yields,  on  cooling,  crystals  of 
bichromate  of  chloride  of  potassium,  KCl,Cr03;  at  100°  this  salt  yields  chlorine. 

The  production  of  chlorine  from  calcium  and  magnesium  chlorides  appears  especially 
important,  as,  if  this  end  is  reached,  the  Leblanc  process  will  probably  be  entirely  super- 
seded by  the  ammonia-soda  process.  Among  the  many  attempts,  those  of  Solvay  and 
Pechiney  demand  especial  attention. 

Solvay  ignites  the  residues  of  calcium  chloride  with  clay.  From  the  mass  the 
carbonic  acid  is  expelled  by  an  addition  of  hydrochloric  acid,  and  the  organic  matter  is 
destroyed  by  heating  in  the  air.  To  prevent  the  mass  from  caking  together  in  the 
furnace  there  is  added  to  the  mixture  of  calcium  chloride  with  silica  or  clay  a  sufficient 
quantity  of  the  residues  of  former  decompositions  or  of  brickbats.  It  appears  that  sand 
is  not  adapted  for  the  process,  but  a  kind  of  infusorial  earth,  known  in  Belgium  as 
"  ergeron."  Before  entering  the  apparatus  the  air  is  passed  through  vessels  containing 
pieces  of  caustic  soda,  so  as  to  take  up  carbonic  acid  and  moisture.  The  decomposi- 
tion apparatus  is  made  of  iron,  coated  with  a  mixture  of  clay,  soda,  and  nitrifiable 
matters. 

The  chlorine  prepared  in  this  manner  is  strongly  diluted  with  air  and  nitrogen.  To 
make  it  fit  for  the  production  of  chloride  of  lime,  the  pulverulent  slacked  lime  is  spread 
out  in  layers  of  suitable  thickness  upon  a  bed  of  porous  mineral  matters — e.g.,  gravel, 
flints,  sand,  or  asbestos  cloth.  The  layers  of  lime  are  laid  methodically,  as  is  done 
with  the  masses  for  purifying  coal  tar.  The  chambers  may  be  arranged  in  series,  but 


SECT,  in,]        CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.        353 

in  any  case  they  must  be  placed  so  that  the  chloriferous  mixture  of  gases  may  encounter 
the  layer  of  lime  in  its  whole  thickness,  and  pass  through  from  above  downwards.  Each 
of  the  six  lead  chambers,  B  (Figs.  313,  314),  connected  by  the  reverser,  ^l,and  arranged 
in  a  circle,  is  provided  with  two  false  bottoms,  upon  which  is  laid  first  asbestos  cloth 
on  a  bed  of  gravel,  and  then  the  lime.  The  chloriferous  gases  enter  the  reverser,  A. 
and  pass  from  there  through  a  pipe,  C,  into  the  upper  part  of  the  chamber  B  which 
has  been  longest  in  use. 

They  pass   downwards,  Fig.  313.  Fig.  314. 

first  through  the  upper 
and  then  the  lower  layer 
of  lime,  and  return 
through  D  to  the  re- 
verser, passing  thence  to 
the  upper  part  of  the 
next  chamber  B,  which 
they  traverse  in  the 
same  manner,  and  so  on 
until  they  arrive  at  the 
chamber  with  the  most 
recent  charge  of  lime. 
Five  chambers  B  are 
always  in  use,  as  the 
sixth  is  disconnected  for 
emptying  and  refilling 
as  soon  as  its  contents 
are  sufficiently  strong. 

The  process  of  Wei- 
don  and  Pechiney  has 
been  at  work  for  a  year 

at  Salindres,  and  promises  to  be  of  importance  for  the  utilisation  of  magnesium 
chloride. 

The  solution  is  evaporated  until  it  corresponds  to  the  formula  MgCl2.6H2O,  and  then 
mixed  with  i'3  equivalent  of  MgOfor  the  formation  of  oxychloride.  For  mixing  there 
is  used  a  revolving  pan,  A  (Figs.  315  and  316),  turning  on  rollers,  a.  Movement  is 
taken  from  the  driving  belt,  B,  by  means  of  the  toothed  wheel,  c  ;  the  agitators,  (7,  Z>,  E, 
are  driven  in  the  same  manner.  The  magnesia  is  introduced  into  the  pan  containing 
the  concentrated  magnesium  chloride,  with  constant  stirring.  The  oxychloride  is 
formed  with  liberation  of  heat,  and  congeals  to  hard  masses,  broken  into  lumps  by  the 
stirrers. 

It  has  the  following  composition  : — 


MgCl2  . 
MgO  . 
H20  . 

Impurities 


35  -oo ;  Cl  =  26  •  1 6  per  cent. 
19-84 
41-16 
4-00 


It  is  broken  up  and  sifted.  What  passes  through  a  sieve  with  meshes  of  5  mm.  is 
returned  to  the  magnesium  chloride  for  the  further  preparation  of  oxychloride.  The 
granular  oxychloride  is  dried.  The  temperature  must  not  exceed  300°.  At  Salindres, 
Pechiney  uses  for  a  drying  chamber  a  channel  of  masonry.  The  oxychloride  is  placed  in 
seven  layers,  each  of  5  to  6  cm.  in  thickness,  upon  small  trucks,  which  are  drawn  through 
the  heating  channel  as  in  Figs.  317  and  318.  To  keep  out  the  external  air  on  the  admission 
of  a  truck,  the  door,  a,  is  opened,  the  truck  is  pushed  into  the  chamber  A,  and  the  door, 
a,  is  again  closed.  The  slides,  c  and  d,  are  then  raised  and  the  entire  train  of  trucks  drawn 


354 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


Fig-  315 


forwards  in  the  channel  by  the  contrivance,  G,  so  that  the  first  truck  partly  enters  the 
chamber  J3,  and  can  be  entirely  drawn  into  it  by  the  hook,  Z>.    It  can  be  removed  after 

lowering  the  slide,  d, 
and  opening  the  door. 
The  gases  at  300°  enter 
at  M,  and  leave  the 
channel  through  the 
pipe,  N. 

!Hf  V&.  The   measuring   ap- 

paratus, A,  of  the  filling 
arrangement  (Fig.  319) 
is  divided  into  seven 
compartments  corre- 
sponding to  the  basins 
on  the  trucks.  Each 
compartment  can  be 
closed  below  by  a  door, 
a.  By  turning  the 
wheels,  (7,  all  these  doors 
may  be  simultaneously 
opened  or  closed.  Below 
the  measuring  apparatus 
is  a  hopper,  D,  mov- 
able on  wheels  and  also 
divided  into  seven  com- 
partments contracted 
below.  Underneath,  on 


Fig.  316, 


Fig.  317. 


the  height  of  the  drying  channel,  there  is  a  movable  frame, 
E,  to  receive  any  empty  truck.  In  Fig.  319  the  frames 
and  trucks  are  shown  in  a  position  ready  to  be  loaded. 
Before  the  truck  is  brought  into  this  position  there  are 
placed  between  each  two  basins  two  short  iron  partitions, 
d,  which  determine  the  thickness  of  the  layer  of  oxychloride. 
The  partitions  are  secured  by  the  screws,  n,  the  heads  of 
which  press  against  the  cross  rails,  o,  which  form  a  part  of 

Fig.  318. 


the  partitions.      To  the  movable  frame  there  are  fixed  below  two  rails,  R,  upon  which 
the  truck  moves.     The  rails  are  fixed  to  the  levers,  F,  so  that  the  truck  can  be  raised 


SECT,  in.]        CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.         355 


•towards  the  top  of  the  frame  by  turning  the  screw,  M,   which  is  in  connection  with 

the  great  lever,  G  ;  when  the  partitions  have  been  introduced  the  frame  is  turned  by 

means  of  a  toothed  wheel  with  a  crank,  which 

is  only  shown  in   dotted  lines   in   the   figure; 

the  hopper  is  moved   above  it ;  the  measuring 

apparatus  is  filled,  and  the  contents  are  then 

emptied  into   compartments  of    the  truck    by 

turning  the  wheel,  C.    The  frame  is  then  turned, 

the  partitions  removed,  and  the  truck  moved 

into  the  drying  stove. 

The  oxy chloride  loses  up  to  65  per  cent,  of 
water  and  5  to  8  per  cent,  of  the  chlorine  in 
the  state  of  hydrochloric  acid  ;  100  parts  oxy- 
•chloride  of  the  above  composition  yield  73*36 
per  cent,  of  residue  of  the  following  composi- 
tion : 


MgCl2  . 
MgO  . 
H,0  . 

Impurities 


44-45;  01  =  33 -30  per  cent. 
28-36 
21-62 
5 '47 


The  decomposition  of  the  oxychloride  is 
effected  in  chambers,  which  are  heated  by  gas 
generator  fires.  Each  of  the  narrow  work- 
•chambers,  A  (Figs.  320  and  321),  opens  upward 
into  the  combustion  chamber,  B,  and  is  fitted 
with  an  inspection  slit,  q.  The  movable  re- 
generator turner,  D,  consists  of  cast-iron  tubes  divided  into  three  compartments 
i,  o,  u.  When  the  valve,  N,  is  opened  (Fig.  322),  heating  gas  passes  through  the  pipes, 
V  and  C  (connected  at  JF),  into  the  compartments,  o,  to  arrive  by  way  of  the  pipe,  d,  in 
the  combustion-chamber,  B.  The  air  needed  for  burning  this  heating-gas  enters  at 
the  bottom  of  the  compartments,  i  and  u;  rises  in  them  upwards  and  issues  from  their 


Fig.  320. 


FIG.  321. 


upper  end  through  the  broad,  flat  pipe,  T,  into  the  combustion  chamber,  B.  The  com- 
bustion gases  go  downwards  through  the  working-chambers,  A,  then  through  the 
-channels  a  and  z  and  round  the  iron  pipes,  D,  in  order  finally  to  escape,  through  Q 


556 


CHEMICAL   TECHNOLOGY. 


[SECT.  in. 


FIG.  322. 


and  P,  into  the  channel  G.  For  the  easy  connection  of  the  burner  with  the  pipe  P,  the 
piece,  Q,  can  be  raised  or  lowered  by  the  lever,  S.  When  the  burner  is  in  the  position 
with  respect  to  the  furnace  (properly  speaking)  which  is  shown  in  Fig.  321  the  rails 
upon  the  block-truck,  K,  are  fixed  to  other  rails  (of  which  one  is  shown  at  r,  Fig.  321), 
in  such  a  manner  that  the  burner  can  be  pushed  over  upon  these  other  rails  and  be 
carried  upon  them  to  another  block-truck  opposite  the  next  furnace.  Whilst, 
therefore,  in  one  furnace  a  solid  substance  giving  off  chlorine  is  being  heated  in 
a  current  of  air,  the  movable  regenerative  burner  can  be  used  for  heating  the  work- 
chambers  of  another  similar  furnace.  As  soon  as  these  work-chambers  are  hot  enough, 
the  valve,  N,  is  closed,  the  pipe  Q  is  lowered  and  the  block-truck,  J£,  upon  which  the 
entire  regenerative  burner  rests,  is  drawn  away  from  the  furnace  until  the  wheels  of 
the  burner  are  opposite  the  rails.  The  openings  for  introducing  the  gases  into  the 

work-rooms  must  be  closed  by  the  door  E, 
and  the  openings  for  removing  the  products 
of  combustion  from  the  working-chambers 
by  the  doors  F.  The  doors  E  and  F, 
when  in  the  closed  position,  are  pressed 
tightly  by  screws.  The  work-chambers,  A, 
are  now  charged  with  magnesium  oxy- 
chloride  in  small  pieces  by  a  tilting-truck, 
which,  after  being  loaded,  has  been  brought 
into  the  proper  position  upon  the  cover  of 
the  furnace.  After  the  lid  has  been  re- 
moved a  hopper  is  placed  over  the  opening 
H,  and  the  oxychloride  is  shot  into  the 

hopper,  so  that  it  falls  into  the  work-chamber  A.  The  cover  of  the  openings  H 
is  then  quickly  put  on  again,  and  air  is  admitted  through  several  openings  (not 
shown  in  Fig.  321)  in  the  door  E  to  A.  The  oxychloride  is  quickly  heated  by 
taking  up  a  part  of  the  heat  previously  stored  up  in  the  walls  of  the  chambers,  and 
there  escapes  from  these  chambers  a  mixture  of  gases  and  vapours  containing  chlorine 
and  hydrochloric  acid.  This  mixture  goes  from  A  through  the  channels  a  into 
the  space  between  the  masonry  of  the  furnace  and  the  door  F,  then  through  the 
channel  I  (Fig.  322)  and  the  pipes,  m,  to  corresponding  arrangements  for  utilising  the 
chlorine.  When  the  decomposition  of  the  oxychloride  is  sufficiently  advanced,  the  access 
of  air  to  the  work-chambers  is  cut  off;  the  door  F  is  opened,  and  the  residual  oxide 
contained  in  the  chambers  A  is  taken  out.  The  cover  of  the  opening  H  is  again  put 


Fig.  323. 


Fig.  324. 


325- 


Fig.  326. 


in  its  place,  and  after  opening  the  door  E,  the  movable  generative  burner  is  brought 
back  to  the  position  shown  in  Fig.  321  when  the  work-rooms  of  the  furnace  (strictly 
so  called)  are  again  heated  for  the  next  operation. 

A  refrigerator  is  connected  with  the  decomposition  apparatus.  It  consists  of  a  stone 
tower  filled  with  glass  tubes,  through  which  cold  water  flows  down.  The  glass 
tubes  (Figs.  323  to  328)  project  with  their  ends  from  the  sides  of  the  tower.  On  one 
side,  A,  each  tube  is  connected  by  a  caoutchouc  pipe  with  the  main,  w,  which  is  supplied 
with  water  from  the  hollow  column,  JV(Fig.  323).  On  the  other  side,  C,  the  water 
flows  through  flexible  pieces,  s,  into  channels,  m,  from  which  it  is  carried  off  through 


SECT,  in.]       CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.         357 

the  hollow  column,  M  (Fig.  223).  That  the  glass  tubes,  c,  may  be  less  likely  to  break, 
they  are  kept  always  filled  with  water.  As  the  acid  liquid  condensing  on  the  surface 
of  the  tubes  flows  to  the  end,  A,  the  joints  here  must  be  well  closed.  For  this  purpose 
there  is  on  the  end  of  the  glass  tube  a  short  caoutchouc  tube,  i,  with  a  flange  (Figs. 
325  and  326),  which  is  firmly  pressed  against  the  stone  by  the  tube-shaped  part  of  the 
stuffing-box,  n.  The  stuffing-boxes  are  drawn  on  by  screws,  which  pass  through  the 
ring-shaped  flanges,  and  catch  in  threads  cut  in  the  rail,  R.  The  gases  or  vapours  to 
be  cooled  are  most  conveniently  introduced  at  P,  near  the  cover  of  the  tower,  and  escape 


Fig  327. 


Fig.  328. 


near  the  bottom,  on  the  opposite  side.  The 
liquid  condensed  in  the  tower  runs  out  through 
the  opening  S. 

The  mixture  of  nitrogen,  superfluous  air, 
chlorine,  and  hydrochloric  acid  is  let  out  of  the 
decomposition  apparatus  through  this  tube- 
cooler  by  means  of  two  gasometer  bells  dipping 
into  a  solution  of  calcium  chloride  and  moving 

alternately  up  and  down,  then  through  a  number  of  sandstone  vessels,  and  lastly 
through  a  scrubber.  The  hydrochloric  acid  in  the  gases  is  thus  completely  condensed, 
and  a  mixture  of  chlorine  and  air  is  carried  on.  The  hydrochloric  acid  from  the 
various  condensers  is  mixed  and  marks  on  the  average  17°  Tw. 

Of  100  parts  of  the  chlorine  of  a  charge,  15  parts  remain  in  the  residues,  45-23  are 
evolved  as  free  chlorine,  and  3977  parts  form  hydrochloric  acid.  As  about  7  parts  are 
lost  in  drying,  the  original  100  parts  of  chlorine  are  distributed  as  follows  : — 


Loss  in  drying 
Left  in  residues 
Free  chlorine 
Chlorine  as  HC1 


6 '60  per  cent. 
14-00        ,, 
42-25 
37-15 


As  a  further  loss  of  5  per  cent,  is  admitted  the  result  is — 


Loss  |  on  drying  ' 
ssl  general        . 
01  returned  f  residues  . 
to  process  {  as  HC1     . 
Free  chlorine  obtained 


'.     5 -co}11'27  Percent- 


13-30] 

35  '29  > 


40-14 


To  obtain  40*14  free  chlorine  there  must  be  produced  100  -48-59  =  51-51  parts  of 
chlorine. 

The  yield  will  probably  be  increased  by  improvements — e.g.,  by  heating  more 
strongly.  The  residue,  after  the  decomposition  in  the  furnace,  is  placed  in  vessels 
cooled  by  water  and  provided  with  agitators. 

The  refrigeration  is  quickly  effected.  The  mass  is  then  sifted  ;  about  £  pass  through 
the  sieve,  being  almost  completely  decomposed  and  containing  scarcely  4  per  cent,  of 
chlorine.  The  part  remaining  on  the  sieve,  about  ^  of  the  mass,  is  still  solid  oxychloride, 
slightly  decomposed.  The  chlorine  is  about  40  per  cent.  This  part  of  the  residue  is 


558 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


at  once  returned  to  the  furnace,  whilst  the  magnesia  (at  Salindres)  is  dissolved  in 
hydrochloric  acid,  and  is  again  submitted  to  the  process. 

At  Salindres  there  are  at  work  (December  1887)  two  fires  with  eight  chambers  each. 
A  thousand  kilos,  of  chlorine  ought  to  be  produced  in  twenty-four  hours,  but  the  present 
yield  is  720  to  760  kilos.  The  author  states  that  at  Stassfurt  200,000  tons  of  mag- 
nesium chloride  yearly  are  allowed  to  flow  into  the  river,  so  that  a  ton  of  chlorine 
ought  to  be  produced  decidedly  cheaper  at  Stassfurt  than  it  is  now  in  England. 

Properties  and  Uses  of  Chlorine.— At  the  ordinary  temperature  and  pressure  of  the 
atmosphere  chlorine  is  a  greenish-yellow  gas,  its  sp.  gr.  =  1*33  ;  it  possesses  a  pecu- 
liarly disagreeable,  irritating  'odour,  and  is  soluble  in  water,  i  volume  absorbing 
2 '5  volumes  of  gas,  forming  the  well-known  aqua  chlorii,  or  acidum  muriaticum 
oxygenatum  aqua  solutum  of  the  pharmaceutists,  and  the  chlorine  water  of  the  scientific 
chemist.  The  bleaching  property  of  chlorine  gas,  shared  also  by  its  solution,  is  due 
to  the  great  affinity  of  chlorine  for  hydrogen,  so  that  the  chlorine,  while  seizing  upon 
the  hydrogen  of  the  organic  body,  in  most  instances  causes  the  simultaneous  decom- 
position of  water,  and  by  the  formation  "of  ozone  destroys  the  organic  colouring  matter, 
hydrochloric  acid  being  formed  at  the  same  time,  a  fact  requiring  attention  in  the 
use  of  chlorine  as  a  bleaching  agent.  When  linen,  or  rather  flax,  raw  cotton,  and  paper 
pulp  are  bleached  by  chlorine,  the  fibre,  really  cellulose,  is  not  acted  upon,  but  only  the 
colouring  matter  is  oxidised  by  the  ozone  formed.  Chlorine  cannot  be  used  to  bleach 
animal  matters,  or  such  as  contain  nitrogen,  these  becoming  yellow  by  its  action. 
Chlorine  is  not  suited  for  transport  either  as  gas  or  in  aqueous  solution,  therefore  one 
of  its  combinations  with  oxygen  and  a  base,  viz.,  a  hypochlorite,  is  used.  Hydrated 
oxide  of  calcium  or  slaked  lime  is  the  chief  constituent  of  bleaching-powder.  Usually 
the  alkali  manufacturers  prepare  bleaching-powder. 

Chloride  of  Lime. — In  the  production  of  chloride  of  lime  the  chlorine  passes  from  the 
generator  through  the  tube,  M,  Fig.  329,  into  a  room  constructed  of  large  blocks  and 

slabs  of  sandstone  joined  by 
means  of  asphalt  cement,  or 
a  mixture  of  coal-tar  and 
fire-clay.  Sometimes  the 
room  is  built  of  bricks  laid 
in  a  similar  cement,  the 
interior  being  lined  with 
asphalt ;  leaden  chambers 
also  are  used  for  this  pur- 
pose. The  room  is  fitted 
with  several  shelves  upon 
which  slaked  lime  is  placed 
in  layers  of  3  to  4  inches 

and  more  in  thickness.  The  chlorine  gas  is  readily  absorbed,  heat  being  evolved.  Care 
is  to  be  taken  that  the  temperature  does  not  exceed  25°,  because  then  calcium  chlorate 
is  formed  ;  this  is  prevented  by  admitting  the  gas  slowly.  As  soon  as  the  absorption 
ceases,  the  bleaching-powder  is  removed  with  rakes  from  the  shelves,  and  fresh  lime 
introduced.  Frequently  the  chloride  of  lime  is  somewhat  diluted  by  an  admixture  of 
slaked  lime. 

Chloride  of  lime,  on  a  system  involving  the  use  of  several  chambers,  has  been 
successfully  manufactured  at  the  Lari  alkali  works  at  Petrowitz  for  eighteen  months. 
According  to  L.  Jahne,  the  system  consists  of  a  lead  chamber,  2  metres  in  height, 
divided  by  cross  walls  into  four  completely  distinct  compartments.  The  chlorine  is 
supplied  from  three  sandstone  generators,  placed  at  a  suitable  distance,  having  a 


Fig.  330- 


D     «- 
1 

—   c 

t 

A 

£  *' 

SECT,  in.]       CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.         359 

common  delivery-pipe,  and  which  are  charged  and  emptied  at  equal  intervals  of  time, 
so  that  a  uniform  current  of  chlorine  is  always  supplied  to  the  chambers.     Each  of 
the  four  chambers,  A  to  D  (Fig.  330),  has  at  that  corner  of  the  top  which  is  nearest  to 
the  middle  of  the  system,  a  pipe  for  the  removal  of  the  chlorine,  and  at  the  angle 
diagonally  opposite  a  longer  escape-tube.      In  each  chamber  there  is  also,  besides  the 
working  door  and  the  opening  at  the  bottom  for  withdrawing  the  finished  product,  a 
bell  for  observing  the  gases,  a  thermometer,  and  an  opening  for 
taking  samples.     The  ends  of  the  eight  entrance  and  exit  tubes 
and  the  chlorine  main,  open  into  a  reversal  apparatus,  and  there 
are  arranged    accordingly  three  chief  exit-pipes  which  open 
through  a  lead  main  into  the  chimney.     The  connection  of 
the  ends  of  the  various  tubes  is  effected  by  placing  a  leaden 
ball  over  each  two   ends,  so  that  the  chlorine  main  in  the 
middle  is  connected  with  the  entrance-pipe  of  A,  the  exit- 
pipe  of  A  with  the  entrance-pipe  of  7>',  the  exit  of  B  with  the  entrance  (7,  &c. 

Liquid  Chloride  of  Lime. — When  it  is  desired  to  prepare  a  solution  of  chloride  of 
lime,  the  apparatus  shown  in  Fig.  331  is  employed.  Two  or  four  earthenware  vessels, 
A,  about  2  hectolitres  capacity,  are  placed  in  the  leaden  trough,  B,  the  bottom  of  which 
.is  protected  by  a  cast-iron  plate  and  a  stoneware  slab,  F,  from  the  direct  action  of 
the  fire  at  D.  B  represents  a  concentrated  solution  of  calcium  chloride  serving  the 
purpose  of  a  bath,  such  a  solution  boiling  at  i79'5°.  By  the  syphon  funnel,  K,  the 
hydrochloric  acid  is  poured  into  A.  I  is  a  perforated  cistern  filled  with  manganese. 
S  is  the  leaden  gas  tube.  The  chlorine,  being  first  washed  in  R,  passes  through  n  into 
T,  filled  with  pieces  of  manganese,  to  decompose  any  vapours  of  hydrochloric  acid 
carried  over,  and,  lastly,  the  chlorine  passing  through  m  reaches  the  absorption  vessel, 
S.  This  vessel  is  a  lead-lined 

wooden    cask,    fitted    with    an  1'ig-  33  *• 

axle  bearing  spokes  to  which 
are  fastened  gutta-percha  floats. 
The  bearings  andplummer-blocks 
of  the  axle  are  made  of  guaiacum 
wood  and  ebonite.  The  axle,  o, 
gears  with  a  suitable  motive 
power,  the  purpose  being  to  keep 
the  milk  of  lime  in  continuous 
motion  while  the  gas  is  being 
admitted. 

The  chlorine  gas  enters  above 
the  level  of  the  fluid,  which  is 
kept  constantly  stirred,  to  assist 

in  the  absorption.  From  the  vessel  wherein  the  absorption  takes  place  a  small  tube 
leads  into  another  vessel  filled  with  water  to  a  depth  of  1 8  to  24  centimetres  ;  a  tube 
fitted  to  this  vessel  leads  into  the  open  air  to  convey  away  any  unabsorbed  chlorine. 
As  in  the  preparation  of  solid  chloride  of  lime,  it  is  here  necessary  to  guard  against  an 
increase  in  temperature  and  also  saturation  ;  Schlieper  has  proved  that  too  concentrated 
solutions  evolve  oxygen,  while  too  dilute  solutions  yield  calcium  chlorate. 

Numerous  researches  have  been  published  on  the  Formation  of  Chloride  of  Lime.  In 
the  chlorination  of  lime  the  presence  of  water  is  of  capital  importance,  though  there  exist 
the  most  contradictory  views.  Graham,  and  subsequently  Frike  and  Reimer,  main- 
tained that  an  anhydrous  calcium  hydrate  was  incapable  of  chlorination.  Gopner  thinks 
an  excess  of  8  per  cent,  the  most  favourable,  but  by  no  means  sufficient  (?).  Richters 


360  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

and  Junker  recommend  an  excess  of  water  of  i  to  2  per  cent.     Davis  recommends  3 

to  4  per  cent.      Kopfer  obtained  chloride  of  lime  on  chlorinising  lime   imperfectly 

slaked.     Lunge  and  Schappi  show  that  imperfectly  slaked  lime  may  be  chloridised, 

and  that  only  ^  mol.  water  of  hydration  may  be  communicated  to  the  chloride  of 

lime,  according  to  which  the  great  absorption  of  chlorine  is  intelligible — 

2Ca(OH)2  +  2C12  =  2CaOCls.H2O  +  HS0;  and 

CaO  +  H2O  =  Ca(OH)2. 

It  has  not  been  found  possible  to  chlorinate  a  perfectly  anhydrous  caustic  lime,  which 
goes  against  Gopner's  formula.  Chloride  of  lime  containing  42  to  43  per  cent,  of 
•effective  (bleaching)  chlorine  can  be  easily  obtained ;  thus  any  formula  which  regards 
such  proportions  as  exceptional  becomes  untenable.  The  strongest  chloride  of  lime  is 
prepared  with  dry  chlorine  and  a  hydrate  of  lime  containing  2  to  4  per  cent,  excess  of 
water.  If  the  chlorine  is  imperfectly  dried,  an  excess  of  i  to  2  per  cent,  is  most 
favourable.  The  formation  of  calcium  chloride  is  unimportant. 

Scheurer-Kestner  gives  the  highest  temperature  in  normal  working  as  55°,  Hurter 
as  40°,  Gmelin  as  18°,  and  Bobierre  as  50°.  On  using  moist  chlorine,  Schappi  obtained 
at — 

Temperature.  Effective  Chlorine. 

-17°  ...  2-30 

O  ...  19-88 

7  —  33-24 

21  -  35-50 

21  ...  39-50 

30  ...  40-10 

40  ...  41-18 

45  ...  40-50 

So  ...  41-52 

60  ...  39-40 

90  ...  4-26 

Hence  it  is  an  error  to  suppose  that  hydrate  of  lime  cannot  absorb  chlorine  at  o°, 
as,  after  two  hours'  action,  a  20  per  cent,  chloride  was  produced,  and  a  weak  sample  was 
even  obtained  below  o°.  With  dry  chlorine  the  most  favourable  temperature  is  10° 
to  16° ;  with  moist  chlorine,  20°  to  60°,  though  the  action  is  best  between  40°  and  45°. 
The  residue  obtained  on  dissolving  chloride  of  lime  in  water  consists  chiefly  of  calcium 
hydroxide,  as  appears  from  the  following  analysis  of  a  good  sample  : — 

CaO       .  .  .  39-89 

Bleach  do.  .  .  43-13 

ClasCaCl2  .  .  0-29 

H20        .  .  .  17-00 

C0a  0-42 


100-73 


H.,0  .     82-65 

CaCO3    .         .  .0-95 

CaCl2     .         .  .0-44 

Ca(OH)2         .  .6-80 

H20  (free)      .  .9-82 


1 00-66 


The  latest  experiments  by  Lunge  confirm  the  formula  CaOCl2  for  chloride  of  lime. 

The  bleaching  salts  obtained  from  the  bivalent  metals,  calcium,  strontium,  and  prob- 
ably barium,  have  probably  the  nature  of  double  salts  of  the  formula  C1...R...OC1,  in 
which  all  the  chlorine  can  be  directly  replaced  by  carbonic  acid. 

Properties  of  Chloride  of  Lime. — Chloride  of  lime  is  a  white  powder,  the  bleach- 
ing constituents  of  which  dissolve  in  about  10  parts  of  water,  whilst  the  excess  of 
lime  is  undissolved.  The  bleaching  action  is  manifested  only  on  the  addition  of  an 
acid. 

The  loss  of  value  of  chloride  of  lime  on  preservation  in  casks  at  temperatures  from 
5°  to  17°  was  examined  by  J.  Pattinson.  Three  sorts  of  chloride  of  lime  had  on 
January  29,  1885  (I.),  and,  after  being  kept  for  a  year  in  casks,  on  January  5,  1886 
(II.),  the  following  respective  compositions  : — 


SECT,  in.]       CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.          361 


A 

B 

C 

I. 

II. 

I. 

II. 

I. 

II. 

Effective  chlorine 

37  -oo 

33-«o 

38-30 

35-10 

36-00 

39-20 

01  as  chloride 

o-35 

2-41 

0-59 

2-42 

0-32 

1-97 

Cl  as  chlorate 

0-25 

— 

0'08 

— 

0-26 

Lime  . 

44  '49 

43'57 

43-34 

42-64 

44  '66 

43-65 

Magnesia    . 

0-40 

o-34 

0-31 

0-36 

o-43 

0-38 

Ferric  oxide 

0-05 

0*05 

O'O4 

0-04 

0'02 

O'O2 

Alumina 

0'43 

o-35 

O'4I 

0-36 

0-33 

0'35 

Manganic  oxide 

trace 

trace 

trace 

trace 

trace 

trace 

CO,     . 

0-13 

0-80 

0-30 

1-48 

0-48 

i'34 

Silicates 

0-40 

0-50 

0-30 

0-04 

0-50 

0-50 

Water 

i6'45 

18-15 

16-33 

17-20 

17-00 

18-89 

Total  chlorine 

37-60 

36-24 

38-97 

37-52 

36-58 

34-87 

Chlorametry, — As  only  the  chlorine  which  exists  in  chloride  of  lime  in  the  form  of 
CaOCl2  comes  into  play  in  its  applications,  such  quantity  determines  its  value. 

Gay-Lussac  makes  use  of  the  oxidising  action  of  chloride  of  lime  upon  arsenious 
acid,  a  volume  of  dry  chlorine  gas  dissolved  in  water  being  employed.  The  solution  of 
chlorine  is  poured  into  a  graduated  tube  divided  into  100  parts,  each  of  these  divisions 
corresponding  to  one-hundredth  of  chlorine.  A  solution  of  arsenious  acid  in  dilute 
hydrochloric  acid  is  also  prepared,  the  strength  of  the  solution  being  such  that  equal 
bulks  of  the  two  liquids  suffer  mutual  decomposition : — 
Arsenious  acid,  As2O3,' 


yield 


J  Arsenic  acid,  As205, 


(Hydrochloric  acid,  4C1H. 


Water,  2H2O, 
Chlorine,  2C12, 

Water  is  decomposed ;  its  oxygen  combines  with  the  arsenious  acid,  forming  arsenic 
acid,  while  the  hydrogen  combines  with  the  chlorine.  Usually  i  litre  of  dry  chlorine 
gas  is  dissolved  in  i  litre  of  distilled  water.  The  normal  solution  of  arsenious  acid 
is  so  prepared  that  it  is  entirely  decomposed  by  the  chlorine  water  to  arsenic  acid. 
The  test  is  carried  out  as  follows  : — Take  10  grammes  of  the  sample,  and  triturate  with 
distilled  water,  adding  sufficient  of  the  latter  to  make  up  a  litre.  Next  take,  by 
means  of  a  graduated  pipette,  10  c.c.  of  the  arsenious  acid  solution,  and  pour  it  into  a 
beaker,  adding  a  drop  of  indigo  solution  to  impart  a  faint  colour ;  next  add,  by  means 
•of  a  burette,  sufficient  of  the  bleaching-powder  solution  to  cause  the  colour  nearly  to 
disappear,  then  add  more  of  the  indigo  solution,  and  again  bleaching-powder  solution, 
until  the  fluid  becomes  quite  colourless.  The  normal  arsenious  acid  solution  is  pre- 
pared by  dissolving  4-4  grammes  of  this  acid  in  32  grammes  of  hydrochloric  acid,  the 
liquid  to  be  di'ubed  to  i  litre.  If  10  grammes  of  bleaching-powder  contain  i  litre  of 
chlorine  gas,  it  is  of  100°  strength. 

Penot's  Test. — Penot  has  modified  Gay-Lussac's  method  in  the  following  particulars : 
— For  the  arsenious  acid  solution  he  substitutes  sodium  arsenite,  and  for  the  indigo 
solution  a  colourless  iodised  paper,  which  is  turned  blue  by  the  smallest  quantity  of 
free  acid.  The  paper  is  prepared  in  the  following  manner: — i  gramme  of  iodine, 
7  grammes  sodium  carbonate,  3  grammes  of  starch,  and  £  litre  of  water  are  mixed. 
When  the  solution  becomes  colourless,  it  is  diluted  to  £  litre ;  in  this  fluid  white 
paper  is  soaked.  The  arsenical  fluid  is  prepared  by  dissolving  4-44  grammes  of  arsenious 
acid,  and  13  grammes  of  crystallised  sodium  carbonate  in  i  litre  of  water.  This  solution 
is  poured,  by  means  of  a  burette,  into  the  solution  of  the  chloride  of  lime  intended  to 
be  tested  (10  grammes  of  the  sample  to  i  litre),  the  completion  of  the  reaction  being 
known  by  the  paper  remaining  uncoloured.  Mohr,  again,  has  modified  this  process, 
not,  however,  in  very  essential  particulars. 

Wagner's   Method. — This   test,  discovered   in  1859,  is   the   so-called   iodometrical 
method,  and  is  based  upon  the  fact  that  a  solution  of  chloride  of  lime  separates  the 


362  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

iodine  from  a  weak  (i  to  10)  and  slightly  acidified  potassium  iodide  solution,  the 
iodine  being  quantitatively  estimated  by  means  of  sodium  thiosulphate : 

x  (  Sodium  iodide,  alSTal, 

Iodine,  2!,  I      .jd    I  godium  tetrathionate,  Na2S4O6, 

Sodium  thiosulphate,  2Na2S203  +  5H20,j    *  |  Water,  5H  O. 

The  test  is  thus  executed:  100  c.c.  =  i  gramme  of  bleaching-powder  solution, 
obtained  by  dissolving  10  grammes  of  chloride  of  lime  in  i  litre  of  water,  are  mixed 
with  25  c.c.  of  solution  of  iodide  of  potassium  acidified  with  dilute  hydrochloric  acid. 
The  ensuing  clear,  deep  brown  coloured  solution  is  treated  with  sodium  thiosulphate 
solution  until  quite  colourless.  The  sodium  thiosulphate  solution  is  composed  of  24*8 
grammes  of  that  salt  to  i  litre  of  water;  i  c.c.  of  this  solution  neutralises  0*0127 
gramme  of  iodine  and  0-00355  gramme  of  chlorine. 

G.  Lunge's  method  for  determining  the  bleaching  chlorine  in  chloride  of  lime 
depends  on  the  observation  that  hypochlorous  acid  if  mixed  with  hydrogen  peroxide 
immediately  gives  up  its  active  oxygen,  as  does  the  hydrogen  peroxide  itself,  so  that 
we  obtain  a  double  quantity  of  oxygen.  A  turbid  solution  of  chloride  of  lime  is 
obtained  in  the  ordinary  manner  with  10  grammes  of  the  sample  to  250  c.c.  of  water. 
5  c.c.  of  the  solution  (  =  0*2  gramme  chloride  of  lime)  are  drawn  off  with  a  pipette, 
and  this  is  let  flow  into  the  external  space  of  the  decomposition  bottle  of  the  nitro- 
meter. Into  the  interior  tube  there  is  poured  an  excess  of  hydrogen  peroxide  ;  for 
this  purpose  2  c.c.  of  the  commercial  article  are  sufficient.  The  quantity  need  not 
be  accurately  measured,  and  the  proportion  of  actual  hydrogen '  peroxide  does  not 
need  to  be  determined  as  long  as  it  is  in  excess.  The  little  bottle  is  then  fixed  upon 
the  caoutchouc  stopper,  grasping  it  by  the  neck,  so  as  to  avoid  warming  it ;  the  cock  of 
the  nitrometer  is  then  turned  so  as  to  connect  the  little  bottle  with  the  measuring 
tube,  the  mercury  in  which  has  been  previously  fixed  at  o°.  The  bottle  is  inclined  so 
that  the  liquids  mix ;  it  is  shaken  for  a  few  moments,  the  mercury  in  both  tubes  is 
placed  at  the  same  level,  and  the  result  is  read  off.  If  0*2  gramme  chloride  has 
been  used,  each  c.c.  of  gas  at  o°  and  at  a  pressure  of  760  mm.  represents  5  French 
degrees  or  1-632  per  cent,  of  efficient  chlorine.  If  we  dissolve  7*917  grammes 
chloride  of  lime  in  250  c.c.,  and  use  for  each  test  5  c.c.  of  the  solution,  i  c.c.  of  gas 
represents  2  per  cent,  chlorine. 

The  determination  of  bleaching  chlorine — i.e.,  of  free  HOC1  or  NaOCl,  is  also 
effected  by  titration  with  sodium  arsenite.  According  to  Penot,  it  is  not  usual  to 
titrate  back  with  solution  of  iodine,  but  to  ascertain  the  end  of  the  reaction  by 
spotting.  Here  all  the  HOC1  and  NaOCl  are  converted  into  NaCl  ;  it  is  therefore 
quite  unnecessary  to  resort  to  other  reducing  agents,  such  as  zinc  powder,  &c.  We 
have  in  the  sodium  arseniate  now  present  an  indicator  for  the  next  operation,  which 
even  surpasses  potassium  chromate. 

For  determining  the  total  chlorine  present  as  hypochlorite  and  chloride,  a  part  of 
the  liquid  obtained  in  the  last  operation  is  titrated  with  decinormal  silver  nitrate  until 
the  reddish-brown  colour  of  silver  arseniate  appears. 

For  determining  the  chlorate  another  portion  of  the  liquid  obtained  in  the  former 
operation  (which  contains  no  hypochlorite,  but  all  the  chlorate)  is  boiled  in  the  valve  flask 
with  a  strong  solution  of  ferrous  sulphate,  the  value  of  which  with  permanganate  has 
been  accurately  ascertained,  and,  after  cooling,  it  is  titrated  back  with  permanganate. 

Chlorometric  Degrees. — In  Germany,  Britain,  Russia,  and  America  the  strength  of 
chloride  of  lime  is  expressed  in  degrees,  which  give  the  percentage  of  effective  chlorine ; 
in  France  (and  in  some  German  works)  the  degrees  represent  the  number  of  litres 
chlorine  gas,  at  o°  and  at  a  pressure  of  760  mm.,  which  can  be  liberated  from  i  kilo,  of 
the  sample  in  question.  The  following  table  gives  the  chlorometric  degrees  for  France 
and  for  Britain  and  Germany : — 


SECT,  in.]       CHLORINE,  CHLORIDE  OF  LIME,  AND  CHLORATES.         363 


French 
Degrees. 

65 

70 

75 
So 

85 
90 


English  and  German 
Degrees. 
20*65 
22-24 
23-83 
25-42 
27-01 
28-60 


French 

Degrees. 

100 

105 
110 

115 

1 20 

125 


English  and  German 

Degrees. 

31-80 

33 '36 

34-95 

38-I3 
3972 


The  percentage  may  be  calculated  from  the  French  degrees  by  multiplying  the 
latter  with  0-318  (i  litre  chlorine  gas  weighs  3*18  grammes). 

Chloride  of  Alkali. — A  solution  of  hypochlorite  of  potassa  is  known  in  commerce 
under  the  name  of  Eau  de  Javette,  while  the  corresponding  soda  solution  is  known  as 
JSau  de  Labarraque ;  these  solutions  are  prepared  by  passing  chlorine  gas  into  a 
solution  of  either  caustic  (i)  or  carbonated  (2)  alkali — 

(i)  2NaOH      +    01,    =    NaOCl    +    NaCl    +    H3O; 
(a)  2Na2C03    +    01,    +    H2O    =    NaOCl    +    NaCl    +    2NaHC03; 
or  by  exhausting  bleaching  powder  with  water,  and  precipitating  the  solution  with 
sodium  sulphate  or  carbonate  solution,  calcium  sulphate  or  carbonate  being  thrown 
down,  while  the  hypochlorite  and  chloride  of  the  alkali  remain  in  solution. 

Aluminium  hypochlorite,  or  Wilson's  bleaching  liquor,  is  obtained  by  mixing 
chloride  of  lime  solution  with  aluminium  sulphate;  it  acts  by  evolving  oxygen, 
leaving  aluminium  chloride  in  solution.  Hypochlorite  of  magnesia  (Ramsay's  or 
Crouvelle's  bleaching  liquor)  is  obtained  by  adding  magnesium  sulphate  to  a  solution 
of  bleaching  powder ;  the  result  is  the  formation  of  a  very  energetic  bleaching  com- 
pound, which,  especially  for  the  purpose  of  bleaching  finely  woven  fabrics,  as  muslins,  <fec., 
is  preferable  to  chloride  of  lime  on  account  of  the  absence  of  caustic  lime.  Varren- 
trapp's  bleaching  salt,  or  zinc  hypochlorite,  is  another  energetic  bleaching  compound 
obtained  by  treating  a  solution  of  chloride  of  lime  with  zinc  sulphate,  the  result  being 
the  precipitation  of  calcium  sulphate,  while  zinc  hypochlorite  remains  in  solution ; 
zinc  chloride  may  be  employed,  but,  of  course,  the  solution  then  retains  calcium 
chloride.  Hypochlorite  of  baryta  is  sometimes  used,  hypochlorous  acid  being  obtained 
by  the  addition  of  very  dilute  sulphuric  acid. 

Potassium  Chlorate  (Chlorate  of  Potassa). — This  salt  (KC103)  consists,  in  100  parts, 
of  38-5  of  potassa  and  61-5  of  chloric  acid;  its  crystals  are  rhombic  and  tabular  in 
form.  It  formerly  was  prepared  by  passing  chlorine  gas  into  a  concentrated  solution 
of  potassium  carbonate,  the  result  being  the  formation  of  potassium  chlorate  and 
chloride.  As  the  chlorate  is  the  less  soluble  it  crystallises  first,  while  by  evaporation 
the  mother  liquor  yields  potassium  chloride.  The  chlorate  is  then  washed  with 
cold  water,  and  purified  by  recrystallisation.  100  kilos,  of  potassium  carbonate 
yield  in  this  manner  9  to  10  kilos,  of  the  chlorate.  At  the  present  day,  however, 
potassium  chlorate  is  prepared  by  a  method,  a  suggestion  of  the  late  Dr.  Graham. 
Chlorine  is  caused  to  act  at  a  high  temperature  upon  milk  of  lime,  with  the  result  of 
the  formation  of  calcium  chlorate  and  chloride,  the  calcium  chlorate  being  after- 
wards decomposed  by  potassium  chloride.  The  method  by  which  potassium  chlorate 
is  prepared  on  the  large  scale  according  to  this  plan  is  the  following : — i  moL  of 
potassium  chloride  and  6  mols.  of  hydrate  of  lime,  having  been  mixed  with  water, 
are  submitted  to  the  action  of  chlorine  gas;  the  solution  yields  on  evaporation 
crystallised  potassium  chlorate,  while  calcium  chloride  remains. 

According  to  Lange  there  are  used  for  saturating  the  milk  of  lime  two  mutually 
connected  cylinders  lined  with  lead,  and  provided  with  agitators  (compare  Fig.  331). 
Both  are  connected  with  each  other  and  with  the  chlorine  generator  in  such  a  manner 
that  the  contents  of  the  one  approach  saturation,  whilst  the  chlorine  left  unabsorbed  in 
the  other  is  taken  up  by  fresh  milk  of  lime.  As  soon  as  complete  saturation  is  reached 


364  CHEMICAL   TECHNOLOGY.  [SECT.  ui. 

in  the  first  cylinder  fresh  milk  of  lime  is  substituted  for  the  contents,  and  the  current 
of  chlorine  is  turned  so  that  it  first  enters  the  second  cylinder.  The  lye  of  calcium 
chloride  and  chlorate  obtained  has  a  rose-red  colour,  which  some  chemists  refer  to 
permanganic  acid,  and  others  to  ferric  acid,  as  it  appears  when  manganese  has 
been  used.  The  colour  is  the  sign  of  perfect  saturation  even  where  the  chlorine  (as  at 
Kunheim's  works  at  Berlin)  is  obtained  by  the  Deacon  process.  The  red  liquid  after 
settling  is  mixed  with  potassium  chloride,  concentrated  down  to  sp.  gr.  1-28,  and  let 
crystallise.  The  mother  liquor  from  the  first  crop  of  crystals  is  again  concentrated  to 
sp.  gr.  i '3 5,  when  a  second,  though  smaller,  crop  of  potassium  chlorate  is  obtained. 
About  1 2  per  cent,  of  the  chlorate  remains  in  the  mother  liquor,  which  consequently 
has  to  be  worked  up  for  chlorine.  The  crystals  obtained  contain  calcium  chloride 
and  iron  as  impurities.  To  remove  these  the  crude  chlorate  is  dissolved  in  the  smallest 
possible  quantity  of  hot  water;  to  10  hectolitres  of  the  liquid  there  are  added  2^  kilos, 
of  soda,  and  the  solution  after  settling  is  let  crystallise.  For  the  formation  of  chlorate 
a  small  excess  of  chlorine  is  necessary,  but  a  special  application  of  heat  is  not  needed, 
as  the  heat  developed  during  reaction  is  sufficient. 

Calcium  chlorate  is  also  formed  by  evaporating  a  solution  of  chloride  of  lime  to 
dryness,  and  is  then  converted  into  the  potassium  salt  by  adding  potassium  carbonate 
or  chloride.  Old  chloride  of  lime,  which  has  partly  lost  its  bleaching  power,  contains 
calcium  chlorate,  and  may  be  used  in  the  manufacture  of  potassium  chlorate. 

According  to  Muspratt,  a  solution  of  chlorine  in  milk  of  magnesia  is  evaporated 
down  to  6o°-98°  Tw.,  so  that,  on  cooling,  a  portion  of  magnesium  chloride  crystallises 
out.  This  lye  is  decomposed  by  the  addition  of  potassium  carbonate  with  formation  of 
potassium  chlorate  and  magnesium  chloride.  The  bulk  of  the  former  crystallises  out. 
The  mother  liquor  still  retains  5  to  10  per  cent,  of  the  potassium  chlorate,  which  is  not 
worth  extraction.  This  lye  is  now  further  treated  with  hydrochloric  acid  and  steam. 
The  potassium  chlorate  is  then  decomposed  into  potassium  chloride,  with  liberation 
of  chlorine,  which  is  absorbed  by  means  of  magnesia  or  lime.  The  solution, 
which  contains  hydrochloric  acid  in  excess,  is  neutralised  with  magnesium  carbon- 
ate, and  forms  then  a  solution  of  magnesium  chloride,  with  a  very  slight  impurity 
of  potassium  chloride,  and  in  Germany  would  have  very  little  value.  But  as 
the  yield  is  larger  than  with  the  lime  process,  the  magnesia  process  deserves  more 
attention. 

Properties. — Potassium  chlorate  crystallises  in  leaflets  of  a  nacreous  lustre,  perma- 
nent in  the  air,  which  dissolve  in  16  parts  of  water  at  15°,  in  8  parts  of  water  at 
35°,  and  in  r6  part  of  water  at  100°.  If  heated  they  give  off  oxygen,  and  if  rubbed 
together  with  combustible  matter  they  explode  most  violently.  One  kilo,  potassium 
chlorate,  if  strongly  ignited,  or  if  heated  with  0^5  kilo,  pyrolusite  or  i  kilo,  ferric 
oxide,  yields  391  grammes  or  274  litres  oxygen.  It  is  extensively  vised  in  pyrotechny, 
in  percussion  caps,  &c.,  as  a  constituent  of  the  white  gunpowder  of  Augendre  and  other 
explosives,  for  preparing  permanganates,  as  an  oxidising  agent  in  tissue-printing — e.g., 
in  the  production  of  aniline-blacks,  and  recently  to  a  large  extent  in  obtaining  violet 
colours  from  dtmethylaniline.  In  the  production  of  aniline-blacks  a  few  per  cents,  of 
potassium  chlorate  are  added  to  the  colour,  and,  after  printing,  the  black  is  fixed  by 
steam  at  3-4  atmospheres.  At  this  temperature  the  chlorate  in  contact  with  the 
organic  matter  is  decomposed,  when  there  occurs  an  oxidation,  and  sometimes  a 
destruction,  of  the  colouring  matter,  though  generally  the  colour  is  rendered  brighter 
and  more  beautiful.  In  the  alizarine  works  in  the  transformation  of  sulphanthra- 
quinonic  acid  into  sodium  alizarate,  potassium  chlorate  is  added  to  the  melt  to  prevent 
the  reduction  of  the  alizarine. 

Potassium  Perchlorate  (KC104). — This  salt  is  sometimes  used  in  pyrotechnics  as  a 
substitute  for  the  more  dangerous  chlorate,  It  is  obtained  by  cautiously  heating  the 


SECT.  IIL]  BROMINE.  365 

chlorate  until  the  mass  becomes  pasty.     It  is  separate  from  the  potassium  chloride 
formed  simultaneously  by  recrystallisation  from  hot  water. 

BKOMINE. 

Bromine  is  found  in  sea-water,  which  contains  about  0*06  gramme  per  litre.  The 
mother  liquor  of  many  brine-springs — e.g.,  those  of  Schoenebeck  (near  Magdeburg), 
those  of  the  basins  of  the  Ohio  and  the  Kanawha,  especially  at  Mason  City,  Pomeroy, 
and  Parkersburg,  at  Alleghany  and  Monongahala,  in  Western  Pennsylvannia,  as  well 
as  the  mother  liquors  from  working  the  salts  of  Stassfurt  and  Leopoldshall,  are  so  rich 
in  bromine  that  its  extraction  is  remunerative.  In  order  to  prevent  admixtures  of 
chlorine,  the  mother  liquor  of  sp.  gr.  i'32,  containing  0*15  to  0^35  per  cent,  bromine, 
is  mixed  with  dilute  sulphuric  acid,  when  hydrobromic  and  hydrochloric  acids  are 
liberated;  the  mixture  is  heated  to  120°,  thus  separating  the  volatile  hydrochloric 
acid  from  the  less  volatile  hydrobromic  acid  which  remains  in  the  liquid.  On  cooling, 
sulphates  separate  out.  The  acid  liquor,  separated  from  the  crystals,  is  distilled  with 
manganese  peroxide  and  sulphuric  acid.  As  a  receiver  are  used  two  WoulfFs  bottles, 
the  first  of  which  is  empty,  whilst  the  second  contains  soda-lye.  In  the  first  are 
condensed  water,  some  bromine,  bromoform,  bromine  chloride,  and  carbon  bromide, 
whilst  the  bromine  vapours  pass  into  the  second  bottle,  and  dissolve  there  as  sodium 
bromide  and  brornate.  The  lye  is  evaporated  to  dryness,  the  residue  ignited  (to  convert 
the  bromate  into  bromide)  and  distilled  with  sulphuric  acid  and  pyrolusite,  thus 
yielding  pure  bromine,  which  is  best  collected  and  preserved  under  concentrated 
sulphuric  acid. 

According  to  the  process  of  A.  Frank,  the  distillation  of  the  bromine  mother 
liquors  with  pyrolusite  and  sulphuric  acid  is  effected  at  Stassfurt  in  large  cubical  stone 
vessels  containing  3  cubic  metres,  and  braced  together  with  iron  bars.  At  some 
distance  from  the  ground  there  is  introduced  a  perforated  plate  of  the  same  stone  upon 
which  the  pyrolusite  is  laid  in  pieces  of  the  size  of  a  nut.  This  vat  is  covered  with  a 
plate  of  the  same  material,  which  is  lifted  by  means  of  a  rope,  with  a  counterpoise 
passing  over  a  pulley.  In  this  plate  there  is  a  stoneware  pipe  for  the  admission  of 
steam ;  it  is  provided  with  a  man-hole  and  an  opening  for  introducing  the  bromine- 
lye  and  the  dilute  sulphuric  acid.  There  is  another  aperture  for  the  escape  of 
bromine  vapours.  The  stones  after  a  time  allow  the  solution  of  manganese  chloride 
to  ooze  through,  and  have  to  be  coated  with  tar.  This  introduces  a  new  defect : 
the  hydrocarbons  of  the  tar  are  converted  into  bromine  substitution-compounds, 
and  thus  considerable  quantities  of  bromine  are  lost,  and  the  product  is  rendered 
impure.  The  loss  at  every  new  tarring  is  estimated  at  50  kilos,  of  bromine.  A 
kind  of  stone  has  since  been  discovered  at  Porta,  Westphalia,  which  does  not  require 
this  costly  preparation,  and  can  be  used  at  once. 

The  bromine-lyes  are  placed  in  a  large  cistern  situate  above  the  distilling  vessels,  in 
which  they  can  be  warmed  by  a  steam-pipe.  Not  all  kinds  of  manganese  are  fit  for 
this  use,  that  of  a  medium  hardness  being  the  most  suitable.  The  rest  of  the  charge, 
both  the  bromine-lye  and  the  acid,  is  run  in  through  one  of  the  small  apertures  in 
the  stone  lid,  which  is  then  immediately  closed  with  a  clay  ball  held  down  with  iron 
weights.  As  soon  as  the  apparatus  is  duly  closed,  steam  is  allowed  to  enter,  when 
abundant  vapours  of  bromine  escape  through  the  leaden  pipe  fitted  in  the  second 
aperture  of  the  stone  plate.  This  lead  pipe  leads  to  a  cooling  worm  of  stoneware,  sur- 
rounded by  cold  water,  in  which  the  bromine  is  condensed.  The  lower  end  of  the 
worm  opens  into  the  middle  tubulure  of  a  large  three-necked  Woulff's  bottle,  in  which 
bromine  and  bromine  water  collect.  In  one  of  the  lateral  tubulures  there  is  a  movable 
glass  syphon,  by  means  of  which  the  bromine  water  can  be  drawn  off  into  stoneware 


366 


CHEMICAL  TECHNOLOGY. 


[SECT.  m. 


jugs.  In  the  other  tubulure  there  is  a  bent  glass  tube,  which  passes  down  to  the  bottom 
of  a  conical  iron  vessel  which  widens  upwards,  and  which  is  filled  with  water  and 
iron  borings.  The  vapours  of  bromine  which  have  escaped  condensation  in  the 
bottle  combine  with  the  iron.  The  impure  iron  bromide  thus  obtained,  as  well  as  the 
bromine  water  drawn  off,  are  returned  to  the  distilling  apparatus  for  the  next 
operation. 

In  the  distillation  there  escapes  at  first  scarcely  anything  but  bromine ;  towards 
the  end  of  the  operation  there  appears  bromine  chloride,  and,  ultimately,  when  there 
is  no  more  bromine  present,  pure  chlorine  passes  over.  These  three  stages  of  the 
operation  can  be  easily  distinguished  by  the  colour  of  the  gas  in  the  glass  receivers. 
In  regular  work  the  process  is  continued  only  to  the  first  appearance  of  bromine 
chloride.  An  operation  which  takes  two  hours  yields  from  2  to  z\  kilos,  of  bromine. 

In  this  process  for  obtaining  bromine  the  apparatus  must  be  emptied  after  each 
operation  and  residues,  still  containing  bromine  and  chlorine,  contaminated  with  salts 
of  manganese,  <fec.,  must  be  run  off.  Instead  of  the  single  distillatory  vessels  charged 
with  bromine-lye,  Frank  employs  a  series  of  stills  placed  like  stairs,  and  directly  above 
each  other,  B  (Fig.  332),  connected  by  pipes  and  cocks.  Into  the  uppermost  of  these 

vessels  the  lye,  serving  for  the 
Fig-  332-  production  of  bromine,  enters 

t        -  — ,1  —  v  I, ,'     through    the    pipe,   b,   whilst 

into  the  lowest  there  passes  a 
current  of  chlorine  and  steam, 
which  is  evolved  in  separate 
generators,  either  by  the  in- 
troduction of  steam  into  the 
chlorine  generator,  D,  or  by 
conveying  the  two  conjointly 
by  means  of  pipes  or  by  draw- 
ing the  chlorine  by  means  of 
the  current  of  steam.  They 
are  mixed  and  distributed  in 

the  bromine-lye.  The  chlorine  and  steam  entering  the  lowest  vessel  liberate  the 
bromine  from  its  compounds,  and  drive  it,  partly  as  pure  bromine,  partly  as  bromine 
chloride,  and  mixed  with  some  free  chlorine,  into  the  next  higher  still,  containing 
fresher  lye,  and  so  on  through  the  entire  column.  Both  the  free  chlorine  and  the 
chlorine  in  the  bromine  chloride,  in  as  far  as  it  is  present,  are  absorbed,  and  in  decom- 
posing the  bromine  compounds  present  in  the  lyes  and  at  the  end  of  the  column  there 
escape  merely  vapours  of  bromine  (nearly  pure)  and  steam  to  the  condensers.  The 
number  of  the  stills  depends  on  their  size  and  on  the  quantity  and  the  strength  of  the  lye 
to  be  operated  upon.  As  soon  as  the  lowest  still  is  sufficiently  driven  off,  its  contents  pass 
into  the  dechlorinising  vessel,  C,  which  is  at  a  lower  level,  and  is  connected  by  means 
of  pipes  and  cocks.  In  this  process  the  mother  liquor  is  of  course  free  from  the  salts 
-of  manganese,  &c.,  which  interfere  with  the  treatment  of  the  residues  from  the 
ordinary  process. 

In  the  apparatus  used  at  the  United  Chemical  Works  of  Leopoldshall  the  bromine- 
lye  flows  through  the  tube,  a,  fitted  with  a  hydraulic  joint  into  a  drum,  6,  of  fire-clay 
or  sandstone  extending  transversely  through  the  entire  width  of  the  tower,  which  is 
provided  on  each  side  with  a  row  of  openings  directed  obliquely  downwards.  Below 
this  drum  there  is  a  horizontal  sandstone  plate,  e,  well  cemented  into  its  place,  in 
which  are  cemented  conically  shaped  earthern  pipes,  cut  off  obliquely  below  and 
provided  with  a  slit  above  (Figs.  333  and  334).  They  are  fixed  with  the  oblique  point 
•downwards,  whilst  the  upper  part  is  free  and  projects  to  the  same  height  above  the  plate. 


SECT. 


III.] 


BROMINE. 


367 


These  pipes  are  so  fixed  that  each  stream  of  liquid  issuing  from  the  openings  of  the 
drum,  b,  falls  in  the  place  between  two  ranks  of  the  tubes.  The  lye  distributes  itself 
equally  above  the  plates,  flows  through  the  slits  of  the  tubes  and  out  at  their  points  in 
fine  streams  upon  the  balls,  which  fill  the  tower  nearly  to  the  top.  The  vapours  given 
off  are  led  through  the  tube  o  of  the  stoneware  worm,  placed  in  the  cooler,  p,  and  the 
liquefied  bromine  collects  in  the  bottle,  q.  In  the  recipient,  B,  there  lie  four  sandstone 


Fig.  333- 


Fig-  334- 


plates,  5,  above  each  other,  joining  close  up  to  three  of  the  walls,  but  leaving  a  small 
interval  against  tne  fourth  wall.  The  intervals  are  alternately  on  two  opposite  sides, 
and  each  plate  is  provided  with  a  row  of  fine  holes.  In  the  middle  of  the  apparatus 
there  is  a  short  sandstone  pipe  which  can  be  connected  above  with  the  steam  pipe,  and 
which  penetrates  all  the  sandstone  plates.  It  is  placed  close  up  to  another  short  sand- 
stone pipe,  r,  which  lies  on  the  bottom  and  extends  straight  through  the  apparatus,  and 
is  bored  longitudinally,  and  is  also  fitted  with  lateral  openings  arranged  at  regular 
intervals.  The  lye  trickling  through  the  tower,  A,  collects  beneath  the  sieve-like  false 
bottom,  c,  arrives  from  here  through  the  tube  z  in  the  apparatus,  B,  and  flows  zig- 
zag downwards  over  all  the  plates  in  the  direction  indicated  by  the  arrows,  in  order  to 
pass  from  the  bottom  through  the  ascending  pipe,  i,  into  the  exit  channel,  k.  The 
apparatus  is  constantly  kept  full  of  liquid  to  the  point  of  the  tube  z.  At  the  same 
time  steam  is  led  in  through  the  pipe  g,  and  keeps  the  lye  constantly  boiling.  The 
vapours  rise  chiefly  through  the  holes  of  the  plates,  s,  and  thus  compel  the  lye  to  take 
its  way  over  the  plates  through  the  slits.  By  this  apparatus  the  lye  is  completely  freed 
from  small  adhering  traces  of  free  chlorine  and  bromine.  The  vapours  collect  in  the 
upper  part  of  the  apparatus,  mix  there  with  the  chlorine  arriving  from  the  washing 
apparatus,  Z>,  through  the  tube  I  (shown  in  the  figure  by  dotted  lines),  rise  through 
the  tube  z  (which  offers  a  sufficient  transverse  section),  back  into  the  tower,  A,  which 
they  traverse  from  below  upwards.  Into  the  vessel,  n,  there  plunges  a  stoneware  pipe, 
d,  suspended  by  a  strap  to  the  rod,  t,  so  as  to  admit  of  turning.  Above  the  entrance 
of  the  tube  x  lies  a  perforated  false  floor,  and  upon  it  a  charge  of  iron  filings.  These 
are  covered  with  a  second  false  bottom,  upon  which  a  slight  current  of  water  is  passed 


368  CHEMICAL   TECHNOLOGY,  [SECT,  in 

through  the  pipe/.  The  vapours  not  condensed  in  the  cooler,  p,  pass  from  below  into 
the  moistened  iron  turnings ;  all  the  chlorine  and  bromine  are  absorbed,  and  the  lye 
dropping  off  flows  continually  through  the  tube  v,  into  the  receiver,  w,  whilst  air  and 
watery  vapour  escape  freely  from  the  top  of  the  tube  d.  For  the  production  of  the 
uniform  current  of  chlorine  which  is  necessary,  the  tubing,  ra,  connected  with  the 
chlorine  generator  is  bent  at  right  angles.  At  its  lowest  point,  a  glass  tube,  h,  pro- 
vided with  a  tubulure,  is  inserted,  so  that  the  small  quantity  of  condensed  water  which 
nere  collects  escapes  through  the  flexible  pipe,  u,  connected  with  the  tubulure  into  the 
washing  apparatus,  D. 

Crude  bromine  when  obtained  by  the  earlier  process  always  contains  chlorine, 
even  when,  as  it  is  done  at  Stassfurt,  the  WoulfFs  bottle  is  slightly  warmed  towards 
the  end  of  the  operation,  so  as  to  drive  the  volatile  bromine  chloride  into  the  iron 
borings.  It  must  therefore  be  submitted  to  rectification.  This  takes  place  in  glass 
retorts  containing  about  15  litres  each,  the  necks  of  which  are  cemented  into  glass 
receivers,  surrounded  with  cold  water.  Each  retort  is  placed  in  a  small  special  sand 
bath,  so  that  if  a  retort  bursts  the  damage  may  be  as  limited  as  possible.  Only  a 
small  watery  fraction  contains  chlorine ;  it  is  removed  and  returned  to  the  stone  vats. 

At  Stassfurt  bromine  is  sent  off  in  strong  glass  bottles  with  ground  stoppers.  The 
stoppers  are  covered  over  with  melted  shellac,  then  luted  with  clay  and  tied  with 
parchment  paper.  Four  or  twelve  such  bottles  are  packed  in  a  box.  Stassfurt  and 
Leopoldshall  furnish  yearly  about  300  tons  of  bromine,  and  North  America  about  200 
tons.* 

Properties  and  Applications  of  Bromine. — Bromine  as  a  liquid  appears  in  mass  of  a 
dark  reddish  brown,  but  in  thin  layers  of  a  hyacinth  red.  Its  odour  is  strong,  and 
resembles  that  of  chlorine.  Bromine  is  rather  freely  soluble  in  water  but  more 
readily  soluble  in  solution  of  potassium  bromide,  in  hydrobromic  acid,  and  in  hydro- 
chloric acid — in  the  last-mentioned  liquid  13  per  cent.  The  aqueous  solution  is 
reddish  brown,  and  on  exposure  to  light  it  is  decomposed,  like  chlorine  water,  with  the 
liberation  of  oxygen  and  the  formation  of  hydrobromic  acid.  At  15°  100  parts  of 
bromine  water  contain  3*226  parts  of  bromine.  With  water,  bromine  forms  at  o°  a 
solid,  crystalline  hydrate.  Bromine  dissolves  readily  in  ether,  alcohol,  -chloroform,  and 
hydrogen  sulphide.  In  aqueous  sulphurous  acid  it  dissolves,  forming  hydrobromic 
acid;  it  boils  at  63°  and  is  converted  into  dark-red  vapour.  At  7-2°  bromine  forms 
a  reddish-brown  crystalline  mass.  With  colouring- matters  bromine  behaves  like 
chlorine.  It  turns  organic  matters  brown.  Like  iodine,  potassium  bromide,  ammo- 
nium and  cadmium  bromide,  and  potassium  hypobromate,  it  is  used  in  photography 
and  pharmacy.  In  the  form  of  bromethyl,  bromamyl,  and  brommethyl,  it  serves  in 
the  production  of  certain  coal-tar  colours,  e.g.,  Hofmann's  blue.  Since  1874  bromine 
is  used  in  the  production  of  cosine  (tetrabromfluoresceine).  It  is  also  used  as  a  dis- 
infectant. Cinnabar,  blende,  and  copper  pyrites  are  decomposed  and  dissolved  by 
bromine. 

IODINE. 

Iodine  was  discovered  in  1811  by  Courtois  in  a  lye  obtained  from  sea-weeds.  The 
first  iodine  manufactory  was  set  up  by  Tissier,  at  Cherbourg,  in  1824.  It  occurs  in 
sea-water  and  is  taken  up  by  marine  plants.  In  the  crude  nitre  of  South  America  it 
is  found  in  large  quantity,  and  in  smaller  proportions  in  some  brine  springs.  The  pre- 
sence of  iodine  in  the  phosphorites  of  Amberg  in  Bavaria  and  of  Diez  (on  the  Lahn),  as 
also  in  the  French  departments  of  Lot  and  of  Tarn  and  Garonne,  may  possibly  become 

*  This  latter  quantity  could  be  indefinitely  increased  if  the  demand  were  greater,  which  would 
be  the  case  if  better  means  of  transport  could  be  adopted.  Shippers  fear  it,  and  the  freight  is 
consequently  high. 


SECT,  in.]  IODINE.  369 

of  commercial  importance.  Kuhlmann  of  Lille  obtains  iodine  as  a  lye-product  in  pre- 
paring superphosphate  from  French  phosphorites,  which  in  1000  kilos,  contain  ^  kilo, 
of  iodine.  The  chief  seat  of  the  iodine  manufacture  is  at  Glasgow,  where  there  are 
twelve  works.  There  are  two  in  Ireland,  and  ten  to  twelve  in  the  Department  of 
Finisterre  in  France,  arid  also  in  Asturias.  At  Tarapaca  in  Peru,  and  Antofagasta  in 
Bolivia,  iodine  is  obtained  in  very  considerable  quantities  from  the  mother-liquors  of  the 
nitre  works. 

In  order  to  obtain  iodine  from  sea-weeds,  the  latter  are  first  converted  into  kelp, 
that  is  to  say,  they  are  incinerated,  the  product  broken  to  pieces  and  lixiviated  with 
water,  leaving  an  insoluble  residue  of  30  to  40  per  cent.,  and  yielding  to  the  liquid  60 
to  70  per  cent.  This  solution,  having  a  sp.  gr.  of  i'i8  to  1*20,  contains  chlorides, 
sulphates,  and  carbonates  of  alkalies,  potassium  sulphide,  chloride,  and  iodide,  and  hypo- 
sulphites of  alkalies  ;  by  evaporating  and  cooling  the  liquor,  the  potassium  sulphate 
and  potassium  and  sodium  chlorides  are  removed.  To  the  remaining  mother-liquor, 
previously  poured  into  shallow  open  vessels,  dilute  sulphuric  acid  is  added,  the  result 
being,  that  while  a  strong  evolution  of  gases,  sulphuretted  hydrogen,  and  carbonic  acid 
takes  place,  there  is  formed  a  thick  scum  and  a  deposit  of  sulphur  at  the  bottom 
of  the  vessel ;  the  sulphur  when  washed  and  dried  is  sold.  When  the  evolution  of  gas 
has  completely  ceased,  more  sulphuric  acid  is  added,  and,  according  to  Wollaston's 
method,  the  required  quantity 

of  manganese ;    this  mixture    is  l%'  335- 

poured  into  a  large  leaden  dis- 
tilling apparatus,  C,  Fig.  335. 
By  this  means  the  iodine  is  set 
free,  carried  over  in  the  state  of 
vapour  to  the  receivers,  B,  B',  B", 
and  condensed  as  a  solid  crystal- 
line mass.  In  Paterson's  large 
iodine  works  at  Glasgow  this 
operation  is  carried  on  in  a  cast- 
iron  hemispherical  vessel  of  1*3 
metre  diameter,  the  cover  being 

a  leaden  dome,  to  which  are  fitted  two  earthenware  still  heads,  connected  by  means 
of  porcelain  tubing  with  two  earthenware  receivers,  Fig.  335,  each  consisting  of  4  to  5 
parts.  At  Cherbourg,  iodine  is  obtained,  according  to  Barruel's  plan,  by  passing 
chlorine  gas  into  the  mother-liquor ;  by  this  plan  the  iodine  is  separated  from  the 
iodide  of  magnesium,  the  latter  taking  up  chlorine  instead — 

(MgI2  +  01,  =  Mg012  +  I,). 

A  more  recent  method,  by  which  all  the  iodine  present  in  the  mother-liquor  is  obtained, 
consists  in  distilling  the  liquor  with  chloride  of  iron — 

(2NaI  +  FeaCl6  =  2!  +  2NaCl  +  2FeCl2). 

As  iodine  is  only  very  slightly  soluble  in  water,  i  part  of  iodine  requiring  5524  parts 
of  water  at  10°  to  12°  for  its  solution,  that  is,  i  grain  of  iodine  to  12  ounces  of  water, 
it  is  carried  over  with  the  steam  and  deposited  at  the  bottom  of  the  receiver  in  the 
form  of  a  black  powder.  When  iodine  is  prepared  by  the  aid  of  chlorine,  the  quantity 
of  gas  should  be  exactly  sufficient  to  decompose  the  iodide  of  magnesium,  for  if  the 
quantity  of  chlorine  be  too  small  no  iodine  is  separated ;  and  if  too  large,  chloride  of 
iodine  is  formed  and  free  bromine,  both  of  which,  being  volatile,  escape.  The  iodine 
when  removed  from  the  receivers  is  drained  on  porous  bricks  or  tiles,  and  dried  between 
folds  of  blotting-paper.  It  need  hardly  be  said  that  the  iodine  should  not  come  in 
contact  with  a  metallic  surface.  The  iodine  thus  obtained  has  to  be  purified  by  sub- 
limation, an  operation  carried  on  in  the  apparatus  represented  in  Fig.  336,  consisting 

2  A 


37° 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


Fig.  336. 


of  stoneware  retorts,  C  C,  placed  in  the  sand-bath,  B,  heated  as  shown  in  the  woodcut. 
Each  of  these  retorts  is  filled  with  upwards  of  40  Ibs.  of  crude  iodine,  and  entirely 

surrounded  by  sand  in  order  to  prevent  the 
sublimation  of  any  iodine  in  the  necks  of 
the  retorts.  These  are  then  connected  with 
the  receiver  or  condenser,  E,  R,  in  which 
the  crystalline  iodine  is  deposited,  the  tubes, 
a  b,  a  b,  being  for  the  purpose  of  carrying  off 
the  watery  vapour,  i  ton  of  kelp  yields  on 
an  average  4-07  kilos,  of  iodine. 

Allary  and  Pellieux  evaporate  the  sea- 
weed lyes  after  separating  the  potassium 
chloride  and  sulphate  and  roast  the  residue 
to  oxidise  the  sulphur  compounds.  The 
.residue  is  lixiviated,  the  solution  evapo- 
rated, pulverised  and  extracted  with  alcohol. 
The  alcohol  is  distilled  off  and  the  residue,  consisting  of  potassium  and  sodium  iodide 
in  a  saturated  solution,  is  mixed  with  a  quantity  of  potassium  carbonate  equivalent  to 
the  sodium  iodide  present,  and  treated  with  carbon  dioxide.  There  are  formed  potas- 
sium iodide  and  sodium  carbonate  which  is  converted  into  bicarbonate  and  deposited. 
The  residual  solution  of  potassium  iodide  is  neutralised  with  hydrochloric  acid  and 
recrystallised  from  alcohol  in  order  to  eliminate  traces  of  potassium  chloride. 

Vitali  saturates  the  sea- weeds  with  a  solution  of  potash  so  that  on  incineration  no 
iodine  may  be  lost.  The  ash  is  heated  to  redness  with  potassium  dichromate.  The 
yield  is  said  to  be  much  greater  than  after  treatment  with  chlorine. 

The  process  of  Stanford  is  carried  out  on  the  large  scale  by  the  British  Sea- weed 
Company,  at  Dalmuir,  near  Glasgow. 

To  prevent  losses  Pellieux  lets  the  fresh  weeds  ferment  before  incineration  in  shaft 
furnaces. 

The  crude  nitre  of  Chili  and  Bolivia  contains  0-059  to  0-175  Per  cent,  iodine  in  the 
state  of  sodium  iodate,  besides  traces  of  sodium  and  magnesium  iodide.  The  mother- 
liquors  from  refining  the  crude  nitre  and  converting  it  into  potash  saltpetre  are  treated 
for  iodine  by  passing  in  a  current  of  S02  until  the  iodine  begins  to  redissolve.  Latterly 
nitrous  acid  is  preferred  to  sulphurous.  The  iodine  liberated  is  dried  and  refined  by 
sublimation.  The  iodine  present  as  iodides  is  precipitated  by  means  of  chlorine. 
One  litre  of  the  mother-liquors  from  refining  nitre  contains  2-3  to  4-8  grammes  iodine. 
At  Peruana  in  Tarapaca  the  concentrated  lyes  of  sodium  saltpetre  have  the  fol- 
lowing composition : — 

Sodium  nitrate 28 

„       chloride n 

,,  sulphate  .  .  .  •  •  3 

Magnesium  sulphate  ....  3 

Sodium  iodate 22 

Water 33 


The  quantity  of  the  solution  of  sodium  bisulphite  necessary  for  precipitation 
depends  on  the  proportion  of  iodine  present.  The  two  liquids  are  mixed  by  means  of 
a  mechanical  agitator,  when  the  iodine  falls  to  the  bottom  of  the  vat  as  a  black  mud. 
Flakes  of  iodine,  which  rise  to  the  surface,  are  skimmed  off  with  wooden  ladles  and 
put  in  settling  vats.  The  mother-liquor  thus  chiefly  freed  from  iodine  is  run  off  into 
a  deep  receiver,  and  is  first  treated  for  nitrate.  It  is  afterwards  again  treated 


SECT,  m.]  NITRIC   ACID   AND   NITRATES.  371 

for  iodine.  The  iodine  mud  deposited  at  the  bottom  of  the  precipitating  vat  is  re- 
peatedly washed  with  clean  water,  filtered  and  converted  by  means  of  a  filter-press 
into  blocks  of  0*2  metre  in  thickness.  This  crude  iodine  contains  80-85  Per  cent- 
pure  iodine,  5—10  per  cent,  of  fixed  matter,  and  5-10  per  cent,  of  water.  It  is  distilled 
in  an  iron  retort,  connected  with  eight  stone- ware  receivers,  each  0-9  metre  long  and  075 
metre  in  diameter.  The  last  is  closed  with  a  wooden  cover,  luted  on  with  clay,  as  are 
all  the  joints  of  the  apparatus.  The  sublimed  iodine  is  packed  in  small  pitched  kegs. 

Iodine  has  recently  been  brought  into  commerce  in  the  form  of  copper  iodide, 
obtained  by  treating  the  lyes  with  a  mixture  of  sodium  bisulphite  and  copper 
sulphate. 

Properties  and  Uses. — Iodine  (1=127;  SP-  gr-  =  4'94)  is  a  black-grey  coloured 
crystalline  substance,  with  a  metallic  appearance  not  unlike  graphite.  On  being 
heated  iodine  is  converted  into  vapours  which,  according  to  Stas,  when  concentrated 
exhibit  a  blue  colour,  and  a  violet  in  a  more  dilute  state.  Iodine  fuses  at  115°, 
and  boils  above  200°.  It  is  somewhat  soluble  in  water,  readily  so  in  alcohol,  ether, 
hydriodic  acid,  potassium  iodide  solution,  carbon  disulphide,  chloroform,  benzol, 
aqueous  solution  of  sulphurous  acid,  and  solution  of  sodium  thiosulphate.  A  solution 
of  iodine  imparts  a  violet  colour  to  starch.  Adulteration  of  iodine  with  either  pul- 
verised charcoal  or  graphite  may  be  at  once  detected  by  treating  a  sample  with  alcohol 
or  a  solution  of  sodium  thiosulphate,  in  each  of  which  the  iodine,  if  pure,  ought  to 
dissolve  completely,  leaving  no  residue  on  sublimation.  Sometimes  the  weight  of 
iodine  is  fraudulently  increased  by  the  addition  of  water.  Iodine  is  largely  used  in 
photography  in  the  form  of  potassium  iodide;  for  the  preparation  of  other  iodine 
compounds,  for  instance,  mercury  iodide  ;  also  in  the  preparation  of  some  of  the  tar 
colours,  iodine  violet,  iodine  green,  and  cyanine  blue,  the  latter  a  compound  of  iodine 
and  lepidin,  a  volatile  base.  The  total  production  of  iodine  in  Europe  and  Chili 
amounted  in  1869  to  3453  cwts.,  more  than  half,  or  1829  cwts.,  being  produced  in 
Scotland  and  Ireland.  At  the  present  day  the  production  of  iodine  at  the  South 
American  nitre  works  is  estimated  at  300  tons  yearly.  Scotland  and  Ireland  now 
produce  130  tons,  and  France  50  tons. 

Iodine  is  also  used  in  the  production  of  eosine,  blue  shade  (tetraiodofluoresceine). 
According  to  the  analysis  of  Wanklyn  (1872)  the  iodine  of  commerce  contains — 

Good.  Inferior. 

Iodine          .        .        .    88'6i  ...  76-21 

Chlorine       .        .        .      0-52  ...  o-88 

Ash       ....      072  ...  I'll 

Water  ....    10-15  ••*  21-80 


lOO'OO  lOO'OO 

NITRIC   ACID  AND  NITRATES. 

Soda  Saltpetre. — This  salt,  NaNO3,  known  as  cubic  nitre,  Chilian  and  Peruvian 
saltpetre,  is  found  in  the  middle  regions  of  the  rainless  district  of  the  west  coast  (costa 
seca)  of  South  America,  most  abundantly  between  19°  and  24°  S.  Lat.  The  chief 
localities  are  in  the  southern  extremity  of  Peru,  in  the  province  Tarapaca,  on  the 
barren  coasts  of  Bolivia,  and  the  desert  of  Atacama.  It  is  found  in  beds  (caliche  or  tierra 
salitrosa)  of  £  to  i|  metre  in  thickness,  extending  for  more  than  240  kilometres  to  the 
neighbourhood  of  Copiapo  in  the  north  of  Chili.  The  beds  are  covered  with  clay,  and 
consist  almost  entirely  of  clean,  dry,  hard  salt,  and  have  apparently  been  formed  from 
sea-weed. 

The  superjacent  rock  (lostra)  is  from  J  to  2  metres  thick,  and  consists  chiefly  of 
a  hard  conglomerate  of  sand,  felspar,  porphyry,  and  other  minerals.  The  composition 


372  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

of  the  caliche  varies.  It  contains  from  48  to  75  per  cent,  sodium  nitrate,  20  to  40  per 
cent,  sodium  chloride,  and  undetermined  quantities  of  sodium  sulphate,  calcium  sul- 
phate, potassium  nitrate  and  iodate,  magnesium  chloride,  as  well  as  insoluble  matter, 
and  organic  substances  including  guano.  It  is  broken  up  in  a  disintegrator,  and 
placed  in  dissolving  pans.  Some  of  the  works  operate  in  open,  quadrangular  cisterns ; 
those  better  arranged  use  closed,  egg-shaped  pans,  provided  with  two  movable  covers, 
the  one  for  introducing  the  caliche  and  the  other  for  taking  out  the  spent  mineral. 
The  mass  rests  upon  a  perforated  false  bottom  at  about  one-quarter  the  height  of  the 
pan,  and  which  consists  of  four  pieces  movable  on  hinges.  The  pans  are  filled  up  to  the  top 
with  comminuted  caliche,  mother- liquor  is  run  in  to  half  height,  and  heat  is  applied  by 
means  of  steam.  In  i^  to  2  J  hours  the  lye  is  sufficiently  saturated  with  nitre,  and  is  run 
off  into  settling  vats.  After  standing  for  some  hours,  the  clear  lye  is  let  flow  into  flat 
crystallisers.  The  residue  in  the  pan  is  removed.  The  crystals  formed,  after  the 
mother-liquor  has  drained  off,  are  spread  out  in  layers  of  0-3  to  0*5  metres  in  thick- 
ness upon  a  large  floor  (Cencha)  exposed  to  currents  of  air,  and  dried  by  frequent 
turning. 

/Sodium  Nitrate. — This  salt,  also  known  as  cubical  saltpetre,  Chili-  saltpetre,  nitrate 
of  soda,  NaN03,  containing  in  100  parts  36*47  soda,  and  63*53  Par>ts  nitric  acid,  is 
found  native  in  the  district  of  Atacama  and  Tarapaca,  near  the  port  of  Iquique,  in  Peru. 
The  deposit  chiefly  consists  of  the  pure,  dry,  hard  salt,  and  is  close  to  the  surface  of  the 
soil.  It  is  also  found  in  other  parts  of  Peru  mixed  with  sand,  in  some  places  close  to 
the  surface  of  the  soil,  in  others  at  a  depth  of  2'6  metres.  Valparaiso  being  the  great 
exportation  depot  for  Peru,  Bolivia,  and  Chili,  both  surface  and  deep  soil  salts  are 
met  with  in  the  trade  of  that  important  port.  The  unrefined  Chili  saltpetre  is  crys- 
talline, brown  or  yellow,  and  somewhat  moist;  but  the  salt  sent  to  the  European 
markets  is  commonly  semi-refined  by  being  dissolved  in  water  and  evaporated  to  dry- 
ness.  The  composition  of  a  sample  in  100  parts  is  : — 

Sodium  nitrate 94*03 

Sodium  nitrite o-3i 

Sodium  chloride    .         . 1-52 

Potassium  chloride 0*64 

Sodium  sulphate 0*92 

Sodium  iodide 0^29 

Magnesium  chloride 0^93 

Boric  acid traces 

Water 1-96 


lOO'OO 


Being  deliquescent  the  salt  is  not  employed  in  the  manufacture  of  gunpowder,  but 
may  be  used  for  blasting  powder.  It  is  largely  used  for  the  preparation  of  sulphuric 
and  nitric  acids ;  for  purifying  caustic  soda ;  for  making  chlorine  in  the  manufacture 
of  bleaching  powders  ;  for  the  preparation  of  sodium  arseniate ;  in  the  curing  of  meat ; 
in  glass-making •  in  the  preparation  of  red  lead ;  in  large  quantities  in  the  conversion  of 
crude  pig-iron  into  steel,  by  Hargreave's  and  by  Heaton's  processes ;  for  preparing 
potassium  nitrate  ;  and  for  the  preparation  of  artificial  manures  and  composts,  it  being 
also  used  unmixed  as  a  manure  for  grain  crops. 

It  may  be  seen  from  the  analysis  of  nitrate  of  soda  quoted  above  that  that  salt 
contains  a  small  quantity  of  iodine,  which  at  Tarapaca  is  extracted  from  the  mother- 
liquor  remaining  from  the  re-crystallisation.  According  to  M.  L.  Krafft  the  iodine 
amounts  to  0-59  gramme  in  i  kilo,  of  crude  nitrate  ;  40  kilos,  of  iodine  being  prepared 
per  day.  M.  Nollner  thinks  that  the  formation  of  the  nitre  deposits  in  Chili  and 
other  parts  of  South  America  has  taken  place  under  the  influence  of  marine  plants 
containing  iodine.  In  order  to  give  some  idea  of  the  large  and  increasing  exportation 


SECT,  in.]  NITRIC   ACID   AND  NITRATES.  373 

of  Chili  saltpetre,  we  quote  from  the  published  statistics,  that  in  1830,  18,700  cwts., 
and  in  1869,  2,965,000  cwts.,  were  shipped.* 

Potassium  Saltpetre.— (KN03  =  101-2.  In  100  parts,  46-5  parts  potassa,  and  53-5 
parts  nitric  acid.) — This  salt  is  to  some  extent  a  native  as  well  as  a  chemical  product. 
The  well-known  flocculent  substance  often  observable  on  walls,  especially  those  of 
stables,  is  composed  in  a  great  measure  of  nitrates ;  a  similar  phenomenon  is  seen  in 
subterranean  excavations,  and  even  in  many  localities  the  surface  of  the  soil  is  covered 
with  an  efflorescent  saline  deposit,  consisting  largely  of  potassium  nitrate.  These 
deposits  are  most  common  in  Spain,  Hungary,  Egypt,  Hindostan,  on  the  banks  of  the 
Ganges,  in  Ceylon,  and  in  some  parts  of  South  America,  as  at  Tacunga  in  the  State  of 
Ecuador ;  while  in  Chili  and  Peru  nitrate  of  soda,  so-called  Chili  saltpetre,  is  found 
in  very  large  quantities  under  a  layer  of  clay  as  above-mentioned. 

Occurrence  of  Native  Saltpetre. — Although  native  saltpetre  is  met  with  under  a 
variety  of  conditions,  they  all  agree  in  this  particular,  that  the  salt  is  formed  under  the 
influence  of  organic  matter.  As  already  stated,  the  salt  covers  the  soil,  forming  an 
efflorescence,  which  increases  in  abundance,  and  which  if  removed  has  its  place  supplied 
in  a  short  time.  In  this  manner  saltpetre,  or  nitre  as  it  is  sometimes  called,  is  obtained 
from  the  slimy  mud  deposited  by  the  inundations  of  the  Ganges,!  and  in  Spain  from  the 
lixiviation  of  the  soil,  which  can  be  afterwards  devoted  to  the  raising  of  corn,  or  arranged 
in  saltpetre  beds  for  the  regular  production  of  the  salt.  The  chief  and  main  condition 
of  the  formation  of  saltpetre,  which  succeeds  equally  in  open  fields  exposed  to  strong 
sunlight,  under  the  shade  of  trees  in  forests,  or  in  caverns,  is  the  presence  of  organic 
matter — viz.,  humus — inducing  the  nitre  formation  by  its  slow  combustion ;  the  col- 
lateral conditions  are  dry  air,  little  or  no  rain,  and  the  presence  in  the  soil  of  a 
weathered  crystalline  rock  containing  felspar,  the  potassa  of  which  favours  the  forma- 
tion of  the  nitrate  of  that  base.  All  the  known  localities  where  the  formation  of  nitre 
takes  place  naturally,  including  the  soil  of  Tacunga,  formed  by  the  weathering  of 
trachyte  and  tufstone,  are  provided  with  felspar.  The  nitric  acid  is  due  to  the  slow 
combustion  of  nitrogenous  organic  matter  present  in  the  humus,  it  having  been  proved 
that  the  nitric  acid  constantly  formed  in  the  air  in  enormously  large  quantities  by  the 
action  of  electricity  and  ozone,  as  evidenced  by  the  investigations  of  MM.  Boussingault, 
Millon,  Zabelin,  Schonbein,  Froehde,  Bottger,  and  Meissner,  has  nothing  what- 
ever to  do  with  the  formation  of  nitre  in  the  soil ;  a  fact  also  supported  by  Dr. 
Goppelsroder's  discovery  of  the  presence  of  a  small  quantity  of  nitrous  acid  in  native 
saltpetres. 

Mode  of  Obtaining  Saltpetre. — The  mode  of  obtaining  saltpetre  in  the  countries 
where  it  is  naturally  formed  is  very  simple,  consisting  in  a  process  of  lixiviation  with 
water,  to  which  frequently  some  potash  is  added  for  the  purpose  of  decomposing  the 
nitrate  of  lime  occurring  among  the  salts  of  the  soil,  the  solution  being  evaporated  to 
crystallisation.  Soils  yielding  saltpetre  are  termed  Gay  earth  or  Gay  saltpetre.  The 
process  by  which  nitrate  of  potassa  is  naturally  formed  is  imitated  in  the  artificial 
heaps  known  as  saltpetre  plantations,  formerly  far  more  general  than  at  the  present 
time,  it  having  been  found  that  the  importation  of  Indian  saltpetre,  and  the  manu- 
facture of  potassium  nitrate  by  conversion  from  sodium  nitrate,  are  cheaper  sources. 
Thus,  saltpetre  beds  are  to  be  met  with  only  under  peculiar  conditions,  as,  for  instance, 
in  Sweden,  where  all  landed  proprietors  are  required  to  pay  a  portion  of  their  taxes  in 
saltpetre. 

The  mode  of  making  these  plantations  may  be  briefly  described  as  follows: — 
Materials  containing  much  carbonate  of  lime — for  instance,  marl,  old  building  rubbish, 

*  The  exports  from  Chili  to  Europe  were,  in  1882,  410,000  tons,  and  in  1883,  530,000  tons, 
f  The  mud  of  the  Ganges  contains,  after  exposure,  8-3  per  cent,  of  potassium  nitrate  and  3  per 
cent,  calcium  nitrate.     The  yearly  export  of  saltpetre  from  India  is  25,000  tons. 


374  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

ashes,  road  scrapings,  stable  refuse,  or  mud  from  canals — is  mixed  with  nitrogenous 
animal  matter,  all  kinds  of  refuse,  and  frequently  with  such  vegetable  substances  as 
naturally  contain  nitrate  of  potassa,  such  as  the  leaves  and  stems  of  the  potato,  the 
leaves  of  the  beet,  sunflower  plants,  nettles,  &c.  These  materials  are  arranged  in  heaps 
of  a  pyramidal  shape  to  a  height  of  2  to  2  J  metres,  care  being  taken  to  make  the  bottom 
impervious  to  water  by  a  well  puddled  layer  of  clay,  the  heap  being  in  all  directions 
exposed  to  the  action  of  the  atmosphere,  the  circulation  of  which  is  promoted  through 
the  heap  by  layers  of  straw.  The  heap  is  protected  from  rain  by  a  roof,  and  at  least 
once  a  week  watered  with  lant  (stale  urine).  The  formation  of  saltpetre  of  course 
requires  a  considerable  length  of  time,  but  when,  taught  by  experience,  the  workmen 
suppose  a  heap  ripe,  the  watering  is  discontinued,  the  salt  containing  saltpetre  soon 
after  efflorescing  over  the  surface  of  the  heap  to  6  to  10  centimetres  in  thickness ;  this 
layer  is  scraped  off,  and  the  operation  repeated  from  time  to  time  until  the  heap 
becomes  decayed  and  has  to  be  entirely  removed.  In  Switzerland  saltpetre  is  artifi- 
cially made  by  many  of  the  farmers,  simply  by  causing  the  urine  of  the  cattle,  while  in 
stable  in  the  winter  time,  to  be  absorbed  by  a  calcareous  soil  purposely  placed  under 
the  loose  flooring  of  the  stables,  which  are  chiefly  built  on  the  slope  of  the  mountains, 
so  that  only  the  door  is  level  with  the  earth  outside,  the  rest  of  the  building  hanging 
over  the  slope,  and  being  supported  by  stout  wooden  poles  ;  thus  a  space  is  obtained, 
which,  freely  admitting  air,  is  filled  with  marl  or  other  suitable  material.  After  two 
or  three  years  this  material  is  removed,  lixiviated  with  water,  mixed  with  caustic  lime 
and  wood  ash,  and  boiled  down.  The  liquor  having  been  sufficiently  evaporated,  is 
decanted  from  the  sediment  and  left  for  crystallisation ;  the  quantity  of  saltpetre  vary- 
ing from  50  to  200  Ibs.  for  each  stable.* 

Treatment  of  the  Ripe  Saltpetre  Earth. — The  crude  salt  from  the  heaps  is  converted 
into  potassium  nitrate  by  the  following  processes: — a.  The  earth  is  lixiviated  with 
water,  this  operation  being  known  as  the  preparation  of  raw  lye.  b.  The  raw  lye  is 
broken,  that  is  to  say,  it  is  mixed  with  a  solution  of  a  potash  salt  in  order  to  convert 
the  magnesium  and  calcium  nitrates  present  into  potassium  nitrate.  c.  Evapora- 
tion of  this  liquor  to  obtain  crude  crystallised  saltpetre,  d.  Refining  the  crude  salt- 
petre. 

Preparation  of  Raw  Lye. — The  ripe  earth  is  lixiviated  to  obtain  all  the  valuable 
soluble  matter,  it  being  expedient  to  use  as  little  water  as  possible  in  order  to  save  fuel 
in  the  subsequent  evaporation,  for  which  the  liquor  is  ready  when  it  contains  from  12 
to  13  per  cent,  of  soluble  salts. 

Breaking  ^vp  the  Raw  Lye. — The  raw  lye,  sometimes  known  as  soil  water,  contains 
the  nitrates  of  lime,  magnesia,  potassa,  soda,  the  chlorides  of  calcium,  magnesium,  and 
potassium ;  also  ammoniacal  salts  and  organic  matter  of  vegetable  as  well  as  of  animal 
origin.  In  order  to  convert  the  magnesium  and  calcium  nitrates  into  potassium  nitrate, 
the  raw  lye  is  broken  up  as  it  is  termed,  that  is  to  say,  there  is  added  to  it  a  solution 
of  i  part  potassium  carbonate  in  2  parts  water — 


Calcium  nitrate,  Ca(N"03)8 
Magnesium  nitrate,  Mg(N03) 
Potassium  carbonate,  2K2CO, 


[Potassium  nitrate,  4.KN03. 
yield  \  Calcium  carbonate,  CaCO3. 

(Magnesium  carbonate,  MgCO3. 


The  calcium  and  magnesium  chlorides  are  also  decomposed,  being  converted  into 
carbonates,  while  potassium  chloride  is  formed.  The  addition  of  the  solution  of 
potassa  to  the  raw  lye  is  continued  as  long  as  a  precipitate  is  formed  ;  in  order,  how- 
ever, to  have  some  approximative  idea  of  the  quantity  of  potassium  carbonate  which  may 
be  required  a  test  experiment  is  made  with  £  litre  of  the  raw  lye. 

Sometimes  potassium  sulphate  is  used  instead  of  the  carbonate,  but  in  that  case  the 
magnesia  salts  of  the  raw  lye  have  first  to  be  decomposed  by  milk  of  lime,  an  operation 
*  In  London  100  tons  of  saltpetre  were  obtained  in  a  similar  manner  in  1873. 


SECT,  in.]  NITKIC   ACID  AND  NITRATES.  375 

which  has  to  be  followed  by  the  evaporation  of  the  fluid.  If,  after  this,  potassium 
sulphate  is  added,  calcium  sulphate  is  precipitated — 

[Ca(N03)2  +  K2S04  -  2KN03  +  CaSOj. 

When  potassium  chloride  is  used  for  the  decomposition  of  raw  lye,  the  salts  of  magnesia 
are  first  removed  by  the  addition  of  milk  of  lime  ;  and  the  clear  supernatant  fluid 
having  been  decanted  from  the  sediment,  there  is  added  a  mixture  of  equal  molecules 
of  potassium  chloride  and  sodium  sulphate,  the  result  being  the  formation  of  gypsum, 
while  the  sodium  nitrate  generated  exchanges  with  the  potassium  chloride,  carrying 
over  to  the  latter  the  nitric  acid,  and  taking  up  the  chlorine  to  form  common  salt. 

Boiling  down  the  Raw  Lye. — The  clarified  raw  lye  decanted  from  the  precipitate 
of  the  earthy  carbonates  consists  of  a  solution  in  which  there  are  present  the  potassium 
and  sodium  chlorides,  potassium  nitrate,  ammonium  carbonate,  excess  of  potassium 
carbonate,  and  colouring  matter.  The  boiling 

down  of  this  liquid  is  effected  in  copper  cauldrons,  Fl£-  337- 

Fig.  337,  so  set  in  the  furnace  as  to  admit  of  the 
circulation  of  the  hot  air  and  smoke  from  the  fire- 
place, passing  by  c  c  below  the  heating  pan,  and 
thence  by  g  into  the  chimney.  In  some  works 
this  waste  heat  is  utilised  in  drying  the  saltpetre 
flour.  As  the  bulk  of  the  fluid  in  the  cauldron 
decreases  by  evaporation,  fresh  lye  enters  by 
means  of  a  pipe  and  tap  from  the  pan,  D.  About 
the  third  day  the  alkaline  chlorides  begin  to  be 
deposited,  and  the  workmen  have  then  to  take 
great  care  to  prevent  these  salts  from  becoming 

what  is  technically  termed  burnt,  which  might  give  rise  to  serious  explosions,  and  for 
this  purpose  the  liquid  is  stirred  with  stout  wooden  poles.  After  each  stirring  the 
loose  saline  matter  is  removed  from  the  boiling  liquid  by  means  of  perforated  copper 
ladles.  However,  as  a  hard  deposit  is  always  formed,  a  peculiar  arrangement  exhibited 
in  Fig.  337,  consisting  of  a  shallow  vessel,  m,  suspended  by  a  chain,  h,  and  weighted 
with  a  piece  of  stone,  is  lowered  into  the  middle  of  the  cauldron  to  about  6  centi- 
metres from  the  bottom,  the  object  being  to  catch  the  solid  particles,  which  would, 
when  aggregating,  form  an  incrustation,  previously  to  their  reaching  the  bottom  of 
the  vessel ;  and  as  no  ebullition  takes  place  at  m,  the  particles  once  deposited  remain 
there,  and  can  be  readily  removed  by  raising  the  dish  out  of  the  cauldron,  and  empty- 
ing it  into  a  box  placed  over  the  cauldron,  the  bottom  of  the  box  being  perforated  to 
admit  of  any  liquor  which  may  have  been  raised  with  the  solid  salt  to  return  again  to 
the  cauldron.  The  deposit  thus  removed  consists  chiefly  of  gypsum  and  carbonate  0? 
lime. 

When  a  portion  of  the  impurities  contained  in  the  boiling  liquid  have  been  removed, 
the  raw  lye  still  frequently  contains  some  sodium  chloride,  as  this  salt  is  not,  as  is 
the  case  with  nitre,  more  soluble  in  boiling  than  in  cold  water.  The  abundant  crystal- 
lisation of  the  saltpetre  is  a  sign  that  the  lye  has  been  sufficiently  evaporated  ;  in 
order,  however,  to  prove  this,  a  small  sample  is  taken,  and  if  on  cooling  the  nitre 
crystallises  so  that  the  greater  part  of  the  sample  becomes  a  solid  mass,  the  liquid  is 
run  into  tanks  and  left  for  5  or  6  hours,  during  which  time  impurities  are  deposited, 
and  the  liquid  rendered  quite  clear.  As  soon  as  the  temperature  of  the  liquid  has 
fallen  to  60°,  it  is  poured  into  copper  crystallisation  vessels ;  after  a  lapse  of  24  hours 
the  crystallisation  is  complete,  and  the  mother-liquor  being  separated  from  the  salt  is 
employed  in  a  subsequent  operation. 

Refining  the  Crude  Saltpetre. — The  crude  saltpetre  is  yellow-coloured,  and  contains 
on  an  average  some  20  per  cent,  of  impurities,  consisting  of  deliquescent  chlorides, 


376  CHEMICAL  TECHNOLOGY.  [SECT.  HI. 

earthy  salts,  and  water.  The  object  to  be  attained  by  the  refining  is  the  removal  of 
these  substances.  At  the  present  day  a  large  portion  of  the  refined  saltpetre  met  with 
in  commerce  is  obtained  by  the  refining  of  the  crude  saltpetre  imported  from  India. 
It  may  be  noted  that  this  importation  is  steadily  increasing,  there  being,  in  1860, 
16,460,300  kilos.,  and  in  1868,  33,062,000  kilos,  of  the  salt  brought  to  England;  and, 
indeed,  the  production  of  saltpetre  from  natural  sources  in  Europe  is  now  limited  to 
very  few  and  unimportant  localities. 

The  method  of  refining  saltpetre  is  based  upon  the  fact  that  potassium  nitrate 
is  far  more  soluble  in  hot  water  than  are  the  sodium  and  potassium  chlorides.  600 
litres  of  water  are  poured  into  a  large  cauldron,  and  24  cwts.  of  the  crude  saltpetre  are 
added  at  a  gradually  increasing  temperature ;  as  soon  as  the  solution  boils,  36  cwts. 
more  crude  saltpetre  are  added.  Supposing  the  crude  nitre  to  contain  20  per  cent,  of 
alkaline  chlorides,  the  whole  of  the  nitre  will  be  dissolved  in  this  quantity  of  water, 
while  a  portion  of  the  chlorides  will  remain  undissolved  even  at  the  boiling-point. 
The  non- dissolved  salt  is  removed  by  a  perforated  ladle,  and  the  scum  rising  to  the 
surface  of  the  boiling  liquid  by  the  aid  of  a  flat  strainer.  The  organic  matter  present 
in  the  solution  is  removed  by  the  aid  of  a  solution  of  glue — from  20  to  50  grammes  of 
glue  dissolved  in  2  litres  of  water  are  taken  for  each  hundredweight  of  saltpetre.  In 
order  that  the  saltpetre  may  crystallise,  the  quantity  of  water  is  increased  to  1000 
litres,  and  as  soon  as  this  water  is  added  the  organic  matter  entangled  in  the  glue  rises 
as  a  scum  to  the  surface  and  is  removed.  The  operation  having  progressed  so  far,  and 
the  liquid  being  rendered  quite  clear,  it  is  kept  at  a  temperature  of  88°  for  about  twelve 
hours,  and  then  carefully  ladled  into  copper  crystallising  vessels,  constructed  with 
the  bottom  a  little  higher  at  one  end  than  at  the  other.  The  solution  would  yield  on 
cooling  large  crystals  of  saltpetre,  but  this  is  purposely  prevented  by  keeping  the  liquid 
in  motion  by  means  of  stirrers,  so  as  to  produce  the  so-called  flour  of  saltpetre,  which 
is  really  the  salt  in  a  finely  divided  state.  This  is  next  transferred  to  wooden  boxes, 
termed  wash- vessels,  10  feet  long  by  4  feet  wide,  provided  with  a  double  bottom,  the 
inner  one  being  perforated  ;  between  the  two  bottoms  holes  are  bored  through  the 
sides  of  the  vessel,  and  when  not  required  plugged  with  wooden  pegs.  Over  the  flour 
of  saltpetre  contained  in  these  wooden  troughs,  60  Ibs.  of  a  very  concentrated  solution 
of  pure  potassium  nitrate  are  poured,  and  allowed  to  remain  for  two  to  three  hours, 
the  plugs  being  left  in  the  holes.  The  plugs  are  then  removed,  the  liquor  run  off,  the 
holes  again  plugged,  and  the  operation  twice  repeated,  first  with  a  fresh  60  Ibs.,  and 
next  with  24  Ibs.  of  the  solution  of  potassium  nitrate,  followed  in  each  case  by  an  equal 
quantity  of  cold  water.  The  liquors  which  are  run  off  in  these  operations  are  of  course 
collected,  the  first  being  added  to  the  crude  saltpetre  solution,  while  the  latter,  being 
solutions  of  nearly  pure  nitre,  are  again  employed.  The  saltpetre  is  next  dried  at  a 
gentle  heat  in  a  shallow  vessel,  sifted,  and  packed  in  casks. 

Preparation  of  Potassium  Nitrate  from  Chili  Saltpetre. — During  the  last  twenty 
years  the  preparation  of  potassium  nitrate  from  Chili  saltpetre  has  become  an  im- 
portant branch  of  manufacturing  industry.  The  product  obtained  by  any  of  the 
following  processes  is  called  "  converted  saltpetre,"  to  distinguish  it  from  the  preceding 
preparation.  The  method  of  procedure  may  be  one  of  the  following : — 

I.  The  sodium  nitrate  is  decomposed  by  means  of  potassium  chloride — 
roo  kilos,  of  sodium  nitrate         "I     .        JIIQ'I  kilos,  potassium  nitrate. 
8  7 -9  kilos,  of  potassium  chloride  /  ^         \  68*8  kilos,  common  salt. 

MM.  Longchamp,  Anthon,  and  Kuhlmann  first  suggested  this  mode  of  preparation, 
which  is  now  generally  used  on  the  large  scale,  as  the  decomposition  of  both  salts  is 
very  complete,  and  as  the  common  salt  as  well  as  the  saltpetre  can  be  utilised.  The 
potassium  chloride  is  obtained  by  the  decomposition  of  carnallite,  or  by  means  already 
mentioned. 


SECT,  in.]  NITKIC   ACID  AND   NITRATES.  377 

Equivalent  quantities  of  sodium  nitrate  and  of  chloride  of  potassium  are  dissolved 
in  water  contained  in  a  cauldron  of  some  4000  litres  cubic  capacity.  As  the  nitrate  of 
soda  of  commerce  (Chili  saltpetre)  does  not,  as  regards  purity,  vary  very  much  from 
96  per  cent.,  some  7  cwts.  are  usually  taken,  while  of  the  chloride  of  potassium,  which 
varies  in  purity  from  60  to  90  per  cent.,  a  quantity  is  taken  corresponding,  as  regards 
the  amount  of  pure  chloride,  to  the  quantity  of  sodium  nitrate.  The  chloride  of  potas- 
sium is  first  dissolved,  the  hot  solution  being  brought  to  a  sp.  gr.  =  1*2  to  1*21 •  next 
the  sodium  nitrate  is  added,  and  the  liquid  brought,  while  constantly  heated,  to  a 
sp.  gr.  =  i'5-  The  sodium  chloride  continuously  deposited  is  removed  by  perforated 
ladles,  and  placed  on  a  sloping  plank  so  that  the  mother-liquor  may  flow  back  into  the 
cauldron,  care  being  taken  to  wash  this  salt  afterwards,  so  as  to  remove  all  potassium 
nitrate,  the  washings  being  poured  back  into  the  cauldron.  When  the  liquid  in  the 
cauldron  has  been  brought  to  1*5  sp.  gr. — an  aqueous  solution  of  potassium  nitrate  at 
15°,  with  a  sp.  gr.  =  1*144,  contains  21*074  per  cent,  of  that  salt — the  fire  is  ex- 
tinguished, the  liquid  left  to  clear,  the  common  salt  still  present  carrying  down 
all  impurities,  and  when  clear  it  is  ladled  into  very  shallow  crystallising  vessels, 
where  the  crystallisation  is  finished  in  twenty-four  hours.  The  mother-liquor  having 
been  run  off,  the  crystals  are  thoroughly  drained  and  covered  with  water,  which 
is  left  in  contact  with  the  salt  for  some  seven  to  eight  hours,  and  then  run  off;  this 
operation  is  repeated  during  the  next  day ;  the  mother-liquor  and  washings  are  poured 
back  into  the  cauldron  at  a  subsequent  operation. 

2.  Sodium  nitrate  is  first  converted   into  sodium  chloride  by  means  of  barium 
chloride,  barium  nitrate  being  formed,  and  in  its  turn   converted   into  potassium 
nitrate  by  the  aid  of  potassium  sulphate : — 

a.     85  kilos,  of  sodium  nitrate       )      .  , ,    (130*5  kilos,  barium  nitrate. 
122  kilos,  of  barium  chloride    J  1 5 8' 5  kilos,  of  common  salt. 

/3.  130*5  kilos,  of  barium  nitrate]      87*2  kilos,  of  potassium  sulphate, 
require  for  conversion  intof  or 

potassium  nitrate  I      69*2  kilos,  of  potassium  carbonate. 

When  potassium  sulphate  is  used,  permanent-white,  baryta-white,  or  barium  sul- 
phate is  obtained  as  a  by-product,  while  if  potassium  carbonate  is  used,  barium  car- 
bonate  remains,  and  of  course  may  be  readily  re-converted  into  barium  chloride. 
In  order  to  estimate  the  advantages  of  either  process,  the  following  points  must  be 
kept  in  view : — a.  Taking  into  consideration  that  it  is  profitable  to  convert  native 
barium  carbonate  into  barium  chloride — for  instance,  by  exposing  witherite  to  the 
hydrochloric  acid  fumes  produced  in  alkali  works  by  the  decomposition  of  salt — and  to 
precipitate  an  aqueous  solution  with  dilute  sulphuric  acid  to  obtain  permanent-white, 
it  may  be  inferred  that  it  will  also  pay  to  obtain  it  as  a  by-product.  6.  Notwith- 
standing the  complication  of  this  process,  it  is  advantageous  as  producing  a  far  purer 
potassium  nitrate. 

3.  Sodium  nitrate  is  converted  by  means  of  potash  into  the  nitrate  of  that  base, 
pure  soda  being  obtained  as  a  by-product : — 

85  kilos.  Chili  saltpetre  1      .  , ,    f  101*2  kilos,  of  potassium  nitrate. 

69*2  kilos,  potassium  carbonate/  \53  kilos,  of  soda  (calcined). 

This  mode  of  manufacturing  saltpetre  was  first  introduced  into  Germany 
during  the  Crimean  War  (1854-55)  by  M.  Wollner,  of  Cologne,  who  established 
large  works  to  prepare  saltpetre  in  this  way,  and  very  soon  after,  during  the  con- 
tinuance of  the  war,  five  other  manufactories  of  potash  saltpetre  had  been  established 
on  this  method.  In  1862  the  production  amounted  to  7,500,000  Ibs.  of  potash  salt- 
petre, the  potassium  carbonate  required  being  obtained  from  beet-root  molasses,  the 
soda  resulting  as  a  by-product  being  even  superior  to  that  produced  by  Leblanc's 
process. 


378  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

According  to  M.  Lunge's  description,  this  process,  first  suggested  by  MM.  Land- 
mann  and  Gentele,  afterwards  modified  by  M.  Schnitzer,  and  practically  applied  by 
M.  Nollner,  is  carried  on  in  Lancashire  in  the  following  manner : — There  is  added 
to  a  caustic  potash  lye  of  1-5  sp.  gr.,  containing  about  50  per  cent,  of  dry  caustic 
potassa,  an  equivalent  quantity  of  sodium  nitrate,  and  the  whole,  after  a  short  time, 
is  crystallised.  The  potassium  nitrate  having  been  separated  from  the  mother-liquor, 
that  fluid,  the  density  of  which  has  been  greatly  decreased  by  the  reaction,  is  by  evapo- 
ration again  brought  to  its  former  density,  and  yields  on  cooling  another  crop  of 
crystals  of  potash-saltpetre.  Usually  there  then  only  remains  a  solution  containing 
caustic  soda  with  saline  impurities ;  sometimes,  however,  a  third  crop  of  crystals  is 
obtained.  The  deposit  during  the  evaporation  is  chiefly  sodium  carbonate  derived 
from  the  sodium  chloride  contained  in  the  potassium  chloride  from  which  the  caustic 
potassa  is  made,  this  chloride  being  also  converted  into  carbonate.  The  small  quantities 
of  undecomposed  potassium  and  sodium  chlorides  and  calcium  sulphate  are  retained 
in  the  mother-liquor,  which  is  evaporated  to  dryness  and  ignited,  yielding  a  dry  caustic 
soda  of  a  bluish-colour.  The  crystallised  potassium  nitrate  is  noAv  carefully  refined  to 
remove  all  impurities  to  about  0*1  per  cent,  of  sodium  chloride,  converted  into 
saltpetre-flour,  and  treated  as  already  described.  Notwithstanding  that  the  various 
operations  have  been  carried  on  in  iron  vessels,  the  salt  does  not  contain  any  of  this 
metal,  nor  is  the  colour  in  any  way  affected .  The  flour  is  dried  in  a  room  2  metres 
wide  by  5  metres  in  length,  built  of  brick- work,  similarly  to  the  chloride  of  lime  rooms, 
and  having  a  pointed  arched  roof  2  metres  in  height.  The  saltpetre-flour  is  spread  on 
a  wooden  floor,  under  which  extends  a  series  of  hot-air  pipes,  keeping  the  temperature 
at  70°,  and  very  rapidly  effecting  the  drying. 

Testing  the  Saltpetre. — If,  when  perfectly  pure,  saltpetre  is  carefully  fused  and 
allowed  to  cool,  it  becomes  a  white  mass,  exhibiting  a  coarsely  radiated  fracture ;  even 
so  small  a  quantity  as  ^th  of  sodium  chloride  causes  the  fracture  to  appear  some- 
what granular ;  with  TVth  the  centre  is  not  at  all  radiated,  and  is  less  transparent ; 
and  with  -^th  the  radiation  is  only  slightly  perceptible  at  the  edges  of  the  fracture. 
Sodium  nitrate  has  the  same  effect.  This  method  of  testing  the  purity  of  nitre,  due  to 
M.  Schwartz,  is  employed  in  Sweden,  where  every  landowner  pays  a  portion  of  his 
taxes  in  saltpetre  of  a  specified  degree  of  purity.  A  great  number  of  methods  of 
testing  saltpetre  have  been  suggested  by  various  authors  for  the  purposes  of  the  manu- 
facture of  gunpowder,  not,  however,  in  sufficiently  general  use  to  interest  the  reader. 
Werther's  test  for  chlorine  and  sulphuric  acid  is  by  solutions  of  the  barium  and  silver 
nitrates ;  the  silver  solution  is  such  that  each  division  of  the  burette  corresponds  to 
0*004  grammes  of  chlorine,  and  the  baryta  solution  to  0*002  gramme  of  sulphuric 
acid.  According  to  Reich's  plan,  0-5  gramme  of  dried  and  pulverised  saltpetre  is 
ignited  to  a  dull  red  heat,  with  from  4  to  6  times  its  weight  of  pulverised  quartz ;  the 
nitric  acid  is  expelled,  the  loss  of  weight  consequently  indicating  the  quantity,  the 
sulphates  and  chlorides  not  being  decomposed  at  a  dull  red  heat.  If  the  loss  =  d,  we 
have  1*874  d  potassium  nitrate,  or  1*574  d  sodium  nitrate. 

Another  method,  due  to  Dr.  A.  Wagner,  is  based  upon  the  fact  that  when  salt- 
petre, or  any  other  nitrate,  is  ignited,  access  of  air  being  excluded,  with  an  excess 
of  chromic  oxide  and  sodium  carbonate,  the  nitric  acid  oxidises  the  chromic  oxide 
according  to  the  formula  Cr203  +  NO.  =  2Cr03  +  N02.  76*4  parts,  by  weight,  of 
chromic  oxide  are  oxidised  to  chromic  acid  by  54  parts  of  nitric  acid,  or  i  of 
chromic  oxide  by  07068  of  nitric  acid.  The  operation  is  performed  by  taking  from  0.3 
to  0*4  gramme  of  the  nitrate,  mixing  it  intimately  with  3  grammes  of  chromic  oxide 
and  i  gramme  of  sodium  carbonate,  introducing  this  mixture  into  a  hard  German  glass 
combustion-tube,  one  end  of  which  is  drawn  out,  and  a  vulcanised  india-rubber  tube 
attached  to  it,  which  is  made  to  dip  for  about  a  quarter  of  an  inch  into  water,  while  to 


SECT.   III.] 


NITRIC  ACID. 


379 


the  other  open  end,  by  means  of  a  cork  and  glass  tube  bent  at  right  angles,  an  ap- 
paratus is  fitted  for  the  evolution  of  carbonic  acid  gas,  which  is  made  to  pass  through 
the  tube  before  igniting  it,  and  kept  passing  through  all  the  time  until  the  tube  is 
quite  cool  again  after  ignition.  The  contents  of  the  tube  are  placed  in  warm  water, 
and  after  filtration  the  chromic  acid  is  estimated  by  Rose's  method.  This  process  of 
estimating  nitric  acid  has  been  found  to  yield  very  accurate  results. 

Uses  of  Saltpetre. — This  salt  is  employed  for  many  purposes,  the  most  important 
being  (i)  The  manufacture  of  gunpowder.  (2)  The  manufacture  of  sulphuric  and 
nitric  acids.  (3)  Glass-making,  to  refine  the  metal  as  it  is  termed.  (4)  As  oxidant 
and  flux  in  many  metallurgical  operations.  By  the  ignition  of  i  part  of  nitre  and  2  of 
argol,  in  some  cases  refined  argol  (cream  of  tartar),  black  flux  is  formed  consisting  of 
an  intimate  mixture  of  potassium  carbonate  and  finely  divided  charcoal.  The  ignition 
of  equal  parts  of  saltpetre  and  cream  of  tartar  gives  white  flux,  consisting  of  a  mixture 
of  potassium  carbonate  and  undecomposed  saltpetre;  both  these  mixtures  are  often 
used.  Black  flux  may  also  be  made  by  intimately  mixing  potassium  carbonate  with 
lamp-black  and  white  flux.  (5)  When  mixed  with  common  salt  and  sugar  in  the 
salting  and  curing  of  meat.  (6)  For  preparing  fluxing  and  detonating  powders. 
Baume's  fluxing  powder  is  a  mixture  bf  3  parts  of  nitre,  i  of  pulverised  sulphur,  and 
i  of  sawdust  from  resinous  wood;  if  some  of  this  mixture  be  placed  with  a  small 
copper  or  silver  coin  in  a  nutshell  and  ignited,  the  coin  is  melted  in  consequence  of 
the  formation  of  a  readily  fusible  metallic  sulphide,  while  the  nutshell  is  not  injured. 
Detonating  powder  is  a  mixture  of  3  parts  saltpetre,  2  potassium  carbonate,  and  i  pul- 
verised sulphur  ;  this  powder  when  placed  on  a  piece  of  sheet-iron,  and  heated  over  a 
lamp,  will  explode  with  a  loud  report,  yielding  a  large  volume  of  gas : 


Saltpetre,  6KN03,  \ 

Potassium  carbonate,  2K2C03,  [     — 
Sulphur,  58.  J 


Nitrogen,  6N. 
Carbonic  acid,  2C02. 
Potassium  sulphate,  5K2S04. 


(7)  For  manure  in  agriculture, 
the  preparation  of  Heaton  steel. 


(8)  In  many  pharmaceutical  preparations.     (9)  For 


NITEIC  ACID. 


Methods  of  Manufacturing  Nitric  Acid. — This  acid  (NH03)  is  generally  manufac- 
tured by  decomposing  nitrate  of  soda  by  sulphuric  acid,  and  condensing  the  vapours  set 
free.  It  is  obtained  on  the  large  scale  by  placing  in  a  cast-iron  vessel,  A,  Fig.  338,  the 
nitrate  to  be  operated  upon,  to  which  is  added  by  means  of  a  funnel  strong  sulphuric 

Fig-  338- 


acid.    The  lid  is  replaced,  and  the  vessel  connected  by  means  of  the  clay-lined  tube,  B, 
with  the  glass  tube,  C,  dipping  into  the  large  stoneware  flask,  D,  which  serves  the  purpose 


380  CHEMICAL  TECHNOLOGY.  [SECT.  HI. 

of  a  receiver.  This  flask  is  connected  by  means  of  a  tube,  a,  to  a  similar  vessel,  ZX, 
and  that  to  a  third  vessel,  J)",  and  so  on,  in  order  to  completely  condense  the  vapours 
which  might  have  escaped  through  the  first,  second,  and  third  vessels.  The  iron 
vessel,  A,  is  heated  by  means  of  the  fire  placed  in  the  hearth,  F,  the  smoke  and  hot 
gases  being  carried  off  by  G  H.  At  the  outset  of  the  operation  the  damper,  d,  is  so 
regulated  as  to  shut  off  the  lower  channel,  and  cause  the  smoke  and  hot  gases  to  pass 
through  E,  heating  the  vessels  Z>,  D' ',  and  D",  this  precaution  being  required  to  prevent 
their  cracking  by  the  hot  acid  vapours  entering  from  A.  As  soon,  however,  as  the 
distillation  has  fairly  commenced,  the  damper  is  altered  to  shut  off  E,  and  pass  the  hot 
air  and  gases  through  G.  The  nitric  acid  condensed  in  the  first  receiver  is  sufficiently 
strong  for  immediate  use,  but  to  facilitate  the  condensation  some  water  has  been 
poured  through  the  openings,  br  b",  into  the  other  receivers,  the  acid  from  which  is 
weaker  and  known  in  the  trade  as  aquafortis. 

Very  frequently  the  distillation  of  nitric  acid  is  conducted  in  a  series  of  glass  retorts 
placed  on  a  sand-bath ;  there  are  generally  two  rows  of  retorts,  the  heating  apparatus 
being  a  galley  oven.  If  the  acid  is  to  be  pure,  the  first  condensations  are  collected  in 
separate  receivers,  as  the  acid  first  condensed  contains  hydrochloric  acid  due  to  the 
chlorides  contained  in  the  nitrates  under  operation. 

The  proportion  of  materials  employed  is — 

30  kilos,  of  potassium  nitrate  to  29  kilos,  of  strong  sulphuric  acid ;  or, 
17        „        sodium  nitrate       to  14/5    „  „  „  „ 

The  sodium  bisulphate  which  remains  may  either  be  used  for  the  preparation  of 
fuming  sulphuric  acid,  or  may  be  mixed  with  common  salt,  and  ignited,  to  produce 
hydrochloric  acid  and  neutral  sodium  sulphate,  available  in  the  preparation  of  sodium 
carbonate. 

The  nitric  acid  (NHOg)  resulting  from  the  above  operation  is  a  colourless,  trans- 
parent fluid,  having  a  sp.  gr.  of  1*55,  and  boiling  at  80°.  When  diluted  with  water 
the  boiling-point  is  higher.  An  acid  containing  100  parts  (NHO3)  and  50  parts  of 
water  boils  at  129°,  but  if  the  dilution  with  water  is  carried  further  the  boiling-point 
is  again  lowered ;  consequently  when  such  an  acid  is  heated  above  100°  the  result  is 
that  at  first  water  with  only  a  trace  of  acid  distils  over,  and  if  the  process  be  continued 
the  boiling-point  gradually  increases  until  it  reaches  130°,  when  there  distils  over  what 
is  termed  double  aquafortis,  sp.  gr.  =  i'35  to  1*45,  ordinary  or  single  aquafortis 
having  a  sp.  gr.  =  rig  to  1*25.  Nitric  acid,  when  in  contact  with  air,  emits  fumes, 
owing  to  the  absorption  of  water  from  the  atmosphere. 

Bleaching  Nitric  Acid. — The  stronger  acid  manufactured  as  described  is  usually 
of  a  yellow  colour,  due  to  the  presence  of  hyponitric  acid.  If  a  colourless  acid  is 
desired,  the  crude  acid  must  be  submitted  to  a  bleaching  operation,  conducted  as 
follows: — The  coloured  acid  is  poured  into  large  glass  vessels  placed  in  a  water- 
bath,  heated  to  80°  to  90°,  and  left  in  these  vessels  as  long  as  any  coloured  vapours  are 
given  off.  The  escaping  hyponitric  acid  is  carried  by  means  of  glass  or  glazed  earthen- 
ware tubes  either  into  a  sulphuric  acid  chamber  and  there  utilised,  or  into  the  flue  of  a 
chimney,  and  thus  into  the  air.  Any  hydrochloric  acid  present  in  the  nitric  acid  is 
also  carried  off  as  chlorine.  In  order  to  remove  any  sulphuric  acid  it  is  necessary  to 
distil  the  nitric  acid  over  pure  barium  nitrate,  while  the  last  traces  of  hydrochloric 
acid  can  be  removed  by  distillation  over  pure  silver  nitrate. 

Condensation  of  the  Nitric  Acid. — More  recently  improvements  have  been  made  in 
the  manufacture  of  nitric  acid,  bearing  especially  upon  the  possibility  of  omitting  the 
bleaching  process,  and  a  better  mode  of  condensing  the  vapours  of  the  acid.  The  first 
point  is  supplied  by  an  arrangement  introduced  in  the  manufactory  of  M.  Cheve,  in 
Paris.  Every  practical  chemist  knows  that  the  red  vapours  appear  only  at  the  outset 
and  towards  the  end  of  the  distillation  of  the  nitric  acid,  and  it  is  therefore  only 


SECT,  in.]  NITRIC   ACID.  381 

required  to  distil  fractionally  to  obtain  on  the  one  hand  a  red-coloured  acid,  the  acidum 
nitroso-nitricum  or  acidum  nitrictim  fumans  fortissime  of  the  pharmaceutists,  and  on 
the  other  a  colourless  acid,  which  can  be  forthwith  delivered  to  the  consumer.  In 
order  to  practically  effect  the  fractional  distillation,  a  tap  of  porcelain  or  hard-fired 
stoneware,  constructed  as  exhibited  in  Fig.  339, 

is  fixed  by  means  of  A,  in  communication  with  Fig.  339. 

the  iron  distilling  vessel,  while  the  tubes  B  and 
£'  are  connected  with  two  different  receivers. 
The  tap  is  bored  in  such  a  manner,  that  at 
pleasure  either  the  communication  between  A 
and  E\  or  the  communication  between  A  and 
B,  can  be  established.  By  proper  management, 
therefore,  it  is  possible  to  separate  the  red- 
coloured  acid  entirely  and  without  any  additional  expense,  from  the  colourless 
acid.* 

For  preparing  a  chemically  pure  nitric  acid  it  is  best  to  distil  the  tetra-hydrated 
acid  (sp.  gr.  i-42.  —  84°  Tw.)  in  glass  vessels  and  receive  the  product  which  goes 
over  separately  as  long  as  it  occasions  a  turbidity  with  a  solution  of  silver  nitrate. 
The  receiver  is  then  changed  and  the  rest  of  the  acid  distilled  off  down  to  a  small 
residue.  At  some  works  a  purified  nitre  is  used  for  obtaining  nitric  acid  free  from 
chlorine. 

Instead  of  the  apparatus  figured,  horizontal  cylinders  of  cast  iron  are  employed  as 
stills,  fixed  so  that  they  are  uniformly  encompassed  by  the  hot  gases.  The  acid  going 
over  last  should  be  collected  separately  as  the  iron  is  attacked  when  the  cylinder  has 
cooled  down.  The  two  ends  of  the  cylinder  are  not  exposed  to  the  fire  and  are  best 
closed  with  plates  of  sandstone,  cemented  in  with  a  mixture  of  iron  filings,  sal 
ammoniac,  sulphur  and  vinegar.  This  cement  dries  quickly  and  resists  the  action  of 
heat  and  acid.  The  front  plate  has  in  its  upper  half  an  opening  for  introducing  the 
nitre.  This  opening  can  be  closed  by  a  stone  plug,  luted  in  with  .clay.  In  this  plug 
there  is  a  small  hole  through  which  the  sulphuric  acid  is  introduced.  The  gases  which 
escape  are  collected  in  the  usual  way  by  passage  through  a  scrubber.  The  proportion 
of  sulphuric  acid  to  nitre  is  not  uniform.  Some  makers  use  to  i  mol.  nitre  if  mol. 
sulphuric  acid,  in  which  case  the  bisulphate  formed  so  reduces  the  melting-point  of  the 
residue  of  sulphate  that  it  may  be  run  out  at  the  end  of  the  operation. 

The  strength  of  the  sulphuric  acid  depends  on  that  of  the  nitric  acid  to  be  pro- 
duced. In  most  cases  an  acid  is  taken  of  171 8  sp.  gr.  (=  143°  Tw.)  The  mixture 
froths  then  least,  so  that  the  retorts  or  cylinders  can  be  filled  up  rather  high.  The 
mean  strength  of  the  nitric  acid  thus  obtained  ranges  from  1*38  to  1*41  sp.  gr.  (76°  to 
82°  Tw.).  For  nitric  acid  at  1-50  to  1-52  sp.  gr.  dried  nitre  is  employed  and  sulphuric 
acid  of  sp.  gr.  1-85  (=  170°  Tw.). 

The  bisulphate  remaining  serves  either  for  producing  fuming  sulphuric  acid  and 
anhydride  or  it  is  ignited  with  common  salt  to  yield  salt-cake  and  hydrochloric 
acid. 

Nitric  acid  may  be  produced  by  the  action  of  manganous  chloride  upon  sodium 
nitrate.  If  a  mixture  of  both  salts  is  heated  to  230°  there  are  evolved  nitrous  fumes 
(N02  -f  O),  and  there  remains  a  manganese  oxide  (Mn508  =  2MnO  +  3Mn03)  which  may 
serve  for  the  production  of  chlorine. 

*  Coloured  nitric  acids  are  sometimes  decolorised  by  the  addition  of  a  small  quantity  of  lead 
peroxide,  which  gives  off  oxygen  to  the  lower  nitrogen  oxides,  and  is  at  the  same  time  converted 
into  lead  nitrate,  which  is  almost  insoluble  in  nitric  acid.  A  so-called  "  single  aquafortis  "  supplied 
to  dyers  has  to  be  very  carefully  purified  from  sulphuric  acid  and  the  lower  nitrogen  oxides,  bat 
may  contain  a  certain  proportion  of  hydrochloric  acid  or  of  ammonium  chloride. 


382 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


Fig.  340. 


If  the  mixture  of  N02  and  0  is  passed  into  a  condensation  apparatus  along  with 
water  it  is  converted  into  nitric  acid,  the  excess  of  the  hyponitric  acid  being  resolved 
into  nitric  acid  and  nitric  oxide.  If  the  air  in  the  apparatus  is  sufficient  to  convert  the 

entire  nitric  oxide  into  nitric  acid  the  process  is  repeated. 
From  numerous  experiments  in  clay  retorts,  conducted 
by  Kuhlmann,  he  found  on  this  process  100  parts  nitre 
yielded  a  mean  of  125  to  126  nitric  acid  at  60°  Tw.,  the 
yield  in  the  ordinary  process  being  127-128  per  cent. 
A  similar  result  was  obtained  with  chlorides,  especially 
calcium  and  magnesium  chlorides.  The  sulphates  also, 
even  those  which  are  very  permanent  and  do  not  in  any 
wise  play  the  part  of  an  acid,  effect  the  decomposition 
of  the  alkaline  nitrates. 

For  obtaining  nitric  acid  by  the  oxidation  and  con- 
densation of  the  lower  oxides  of  nitrogen,  Rohrmann 
(Fig.  340)  uses  an  earthen  condensing  columm.  The 
lower  part,  A,  contains  a  perforated  inverted  beaker,  a. 
At  the  foot  is  the  efflux  pipe,  C,  and  on  the  other  side 
the  outflow,  D,  which  receives  the  junction-pipe,  Et 
through  which  is  led  nitric  oxide  gas  obtained  in  any 
manner.  To  the  pipe,  E,  is  affixed  the  piece,  F,  through 
which  there  enters  a  pipe,  G,  which  at  its  upper  end 
receives  the  blast,  H,  for  the  introduction  of  steam  and 

air.  Above  the  beaker,  A,  rise  the  beakers,  E,  in  the  form  of  a  column.  They  have  a 
large  aperture,  «7,  at  the  bottom,  with  a  thickened  margin  at  the  under  side.  Over 
the  opening,  J,  is  the  inverted  beaker,  S,  the  side  of  which  is  perforated  like  a  sieve. 
In  the  earthen  pipe-connections  placed  between  the  several  columns,  there  is  intro- 
duced a  lantern  provided  with  glass  discs.  The  openings  for  the  access  of  air  in  the 
blast  can  be  altered. 

The  Densities  of  Nitric  Acid. — According  to  J.  Kolb,  the  connection  between  the 
sp.  gr.  of  nitric  acid  and  its  per  centage  of  concentrated  acid  is  as  follows  : — 


ioo  parts  contain 

Density. 

ioo  parts  contain 

Density. 

NH03. 

NA- 

Ato°. 

At  iS°C. 

NHO3. 

N205- 

Ato°. 

At  15°  C. 

IOO  '00 

8571 

I'S59 

I-530 

50-99 

43-70 

I-34I 

•323 

97-00 

83-14 

I-548 

1-520 

45'OQ 

38-57 

•300 

•284 

94'DO 

80-57 

1-537 

1-509 

40-OO 

34-28 

•267 

•251 

92-00 

78-85 

1-529 

I-503 

33-86 

29-02 

•226 

•211 

9I-OO 

78-00 

1-526 

1-499 

30-00 

2571 

•2OO 

•I8S 

9O-OO 

77-15 

I-522 

1-495 

2571 

22-04 

•171 

•157 

85-00 

72-86 

I-503 

1-478 

23-00 

1971 

•153 

•138 

80  -oo 

68-57 

1-484 

1-460 

20-00 

17-14 

•132 

•I2O 

75-00 

64-28 

I-465 

1-442 

15-00 

12-85 

•099 

•089 

69-96 

60  -oo 

1-444 

I-423 

11-41 

977 

1-075 

I-067 

65-07 

5577 

1-420 

1*400 

4-00 

3-42 

I-O26 

I'022 

60'00 

51-43 

1-393 

1-374 

2'OO 

1-71 

I-OI3 

I'OIO 

55-00 

47-I4 

1-365 

1-346 

The  following  table  exhibits  comparative  data  of  density  and  degrees  according  to 


SECT.    III.] 


NITRIC   ACID. 


383 


Degrees  according 
to  Beaum^. 

Density. 

100  parts  contain  at  o° 

ioo  parts  contain  at  15°  C. 

NH03. 

N205. 

NH03. 

N205- 

6 

•044 

67 

57 

7-6 

6-5 

7 

•052 

8-0 

6-9 

9'0 

77 

9 

•067 

IO'2 

87 

II'4 

9'8 

10 

•075 

II'4 

9-8 

127 

io'9 

15 

•116 

17-6 

iS'i 

19-4 

16-6 

20 

•161 

24  '2 

207 

26-3 

22'5 

25 

•2IO 

3i  '4 

26-9 

33-8 

28-9 

30 

•26l 

39-1 

33  '5 

4i-5 

35-6 

35 

•321 

48-0 

41-1 

507 

43'5 

40 

•384 

58-4 

50*0 

617 

52-9 

45 

"454 

72-2 

61-9 

78-4 

72  '2 

46 

•470 

76-1 

65-2 

83-0 

7I-I 

47 

•485 

80-2 

687 

87-1      - 

747 

47°  B.  correspond  to  96°  Twaddell. 
46°  92°        „ 

45° 


43 
42° 

38° 


84° 
80° 
70° 


34°  B.  correspond  to  60°  Twaddell. 

29°  ,  50° 


25° 
20° 
14° 

7° 


40° 
30° 
20° 


Nitric  acid  of  i  -52  sp.  gr.  boils  at  86° 
,,  1-50  „  99° 

»  i '45  »  ii5° 

»  i '42  „  123° 

„  1-40  „  119° 


Nitric  acid  of  i'35  sp.  gr.  boils  at  117° 

,i  i'3°  »  "3° 

„  1-20  „  108° 

,,  I  'IS  n  104° 


Fuming  nitric  acid  is  generally  now  obtained  by  mixing  in  a  retort  ioo  parts  of  nitre 
with  3-5  parts  of  starch  and  adding  ioo  parts  of  sulphuric  acid  at  sp.  gr.  1*85.  The 
retort  should  only  be  filled  to  one-third. 

Fuming  nitric  acid  or  even  nitric  acid  of  sp.  gr.  1*26,  if  it  comes  in  contact 
with  dry  packing  materials,  may  give  rise  to  fires.  Straw,  or  the  like,  should  there- 
fore be  previously  steeped  in  a  solution  (saturated  in  the  cold)  of  Glauber's  salt, 
Epsoms — i.e.,  magnesium  sulphate,  &c. 

Technical  Applications  of  Nitric  Acid. — The  technical  application  of  nitric  acid  is 
based  on  its  property  of  oxidation  when  in  contact  with  certain  substances,  the  acid  split- 
ting up  into  nitrogen  dioxide,  hyponitric  acid  and  ozone,  the  latter  forming  with  the 
body  which  caused  the  decomposition  of  the  acid  either  an  oxide  or  a  peculiar  com- 
pound, while  the  hyponitric  acid,  when  organic  substances  are  present  capable  of 
combining  with  it,  forms  the  nitro-compounds,  nitrobenzole,  nitronaphthaline,  nitro- 
glycerine, nitromannite,  nitrocellulose,  or  gun-cotton,  &c.  A  large  number  of  metals 
are  soluble  in  moderately  concentrated  nitric  acid,  but  the  strongest  acid  fails  to  act 
upon  iron  and  lead.  Proteine  compounds,  albumen,  the  skin  of  the  hands,  silk,  horn, 
feathers,  &c.,  are  stained  yellow  by  nitric  acid,  hence  the  use  of  this  acid  in  dyeing 
silk.  If  the  acid  is  in  contact  with  these  substances  for  any  length  of  time,  they  are 
completely  decomposed,  and  partly  converted  into  picric  acid.  Starch,  cellulose,  and 
sugar,  are  converted  by  the  action  of  nitric  acid  into  oxalic  acid  ;  but  very  dilute  nitric 
acid  converts  starch  into  dextrine,  and  concentrated  acid  into  xyloidine.  Owing  to  the 
property  nitric  acid  possesses  of  destroying  certain  pigments — for  instance,  indigo — it 
is  sometimes  employed  in  calico  printing  to  produce  a  yellow  pattern  on  an  indigo 
ground.  This  acid  is  also  used  in  dyeing  woollen  materials ;  in  hat-making,  to  prepare 
a  mercurial  solution  used  in  dressing  felt  hats ;  in  the  manufacture  of  sulphuric  acid ; 
in  the  preparation  of  lacquers ;  in  the  preparation  of  nitrate  of  iron,  a  mordant  used  in 
dyeing  silk  and  cotton  black ;  for  preparing  picric  acid  from  carbolic  acid,  and  naphtha- 
line-yellow from  naphthaline;  in  the  manufacture  of  nitrobenzol,  nitrotoluol,  and 


384  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

phthalic  acid ;  and  for  the  preparation  of  nitrate  of  silver,  arsenic  acid,  fulminating 
mercury,  nitroglycerine,  dynamite,  &c. 

It  serves  further,  under  the  name  fiouille,  for  producing  a  compound  of  iron 
fraudulently  used  for  "  loading  "  or  "  weighting  "  black  silks  in  the  process  of  dyeing, 
of  which  ten  tons  are  consumed  daily  in  Lyons. 

EXPLOSIVES. 

Gunpowder. — The  substance  known  as  gunpowder,  or  simply  as  powder,  is  a  more 
or  less  finely  granulated  mechanical  mixture  of  saltpetre,  sulphur,  and  charcoal,  the 
quantities  of  these  materials  being  properly  denned.  It  ignites  at  300°,  also  when 
touched  with  a  red-hot  or  burning  body,  or  under  certain  conditions  by  friction  or  a 
sudden  blow.  Powder  under  these  conditions  burns  off  rapidly  but  not  instantaneously, 
yielding  as  the  products  of  its  combustion  nitrogen,  carbonic  acid,  or  carbonic  oxide, 
while  there  remains  a  solid  substance  consisting  of  a  mixture  of  potassium  sulphate  and 
carbonate.  When  the  powder  is  ignited  in  a  closed  vessel,  the  sudden  evolution  of  the 
large  volume  of  gases  causes  a  pressure  almost  impossible  to  be  withstood ;  and  even  in 
guns  and  large  ordnance,  in  which  one  side  of  the  vessel  is  formed  by  the  yielding  shot, 
the  metal  forming  the  other  sides  must  possess  great  strength  and  elasticity.  In  guns 
and  artillery  the  pressure  only  lasts  as  long  as  the  ball  is  inside  the  gun,  therefore  the 
slower  the  combustion  of  the  powder  through  its  entire  mass,  the  lower  is  the  velo- 
city of  the  projectile. 

Manufacture  of  Gunpowder. — It  is  essential  that  the  materials  employed  in  the 
manufacture  of  powder  should  be  very  pure ;  the  saltpetre  should  not  contain  any 
chlorides  ;  the  sulphur  should  be  free  from  sulphurous  acid,  hence  not  flowers  of  sul- 
phur but  refined  roll  sulphur  is  used ;  and  lastly  the  charcoal  requires  very  great 
attention.  The  wood  from  which  it  is  intended  to  prepare  a  charcoal  for  gunpowder 
should  be  such  as  yields  the  least  possible  quantity  of  ash,  while  the  charcoal  should  be 
soft,  like  that  used  in  pharmacy.  The  stems  of  the  hemp  and  flax  plants,  especially  the 
former,  yield  excellent  charcoal,  but  in  consequence  of  the  limited  supply,  the  wood  of 
the  wild  plum  tree  (Prunus  padus)  is  largely  used  in  Germany,  France,  and  Belgium  ; 
and  in  England  the  lime,  willow,  poplar,  horse-chestnut,  hazel,  cherry,  alder,  and 
other  light  white  woods  are  employed  for  this  purpose.  All  these  varieties  yield  on 
being  carbonised — effected  in  various  ways,  in  retorts  similar  to  those  used  in  gas-works, 
in  pits  dug  in  the  earth,  or  by  the  aid  of  superheated  steam,  the  wood  being  placed  in 
boilers,  &c. — from  35  to  40  per  cent,  charcoal.  The  temperature  during  the  progess 
of  carbonisation  being  kept  as  low  as  possible,  there  is  obtained  a  very  soft  reddish- 
brown  charcoal,  known  as  charbon  roux.  The  charcoal  prepared  in  cylindrically  shaped 
retorts  is  very  inappropiately  designated  distilled  charcoal. 

Mechanical  Operations  of  Powder  Manufacture. — These  operations  include  : — 

I.  The  pulverising  of  the  ingredients.  2.  The  intimate  mixing  of  these  substances 
3.  The  moistening  of  the  mixture.  4.  The  caking  or  pressing.  5.  The  granulation 
and  sorting  of  the  grain,  as  it  is  termed.  6.  Surfacing  the  powder.  7.  Drying. 
8.  Sifting  from  the  dust. 

Pulverising  the  Ingredients. — This  operation  can  be  performed  in  three  different 
ways : — 

a    By  means  of  revolving  drums. 

b.  By  mill  stones ;  or 

c.  In  stamping-mills. 

a.  The  pulverisation  by  means  of  revolving  drums  is  an  invention  due  to  the  French 
Revolution,  and  has  the  advantages  of  being  very  effective,  rapid  in  execution,  and  of 
preventing  the  flying  about  of  the  ingredients  in  a  fine  dust.  The  drums  are  made  of 


SECT,  in.]  EXPLOSIVES.  385 

wood,  lined  with  stout  leather,  and  provided  with  a  series  of  projections.  The  substance 
to  be  pulverised  is  put  into  the  drum  with  a  number  of  bronze  balls  of  about  ^  inch 
diameter,  their  action  aided  by  that  of  the  projections,  when  the  drum  is  turned  on  its 
horizontal  axis  at  a  moderate  speed,  soon  effecting  a  reduction  to  a  fine  powder.  The 
charcoal  and  sulphur  are  separately  pulverised  ;  the  saltpetre  being  obtained  as  a  flour. 
(See  Saltpetre.) 

b.  Grinding  by  the  aid  of  mill-stones.     Two  heavy  vertical  stones,  similar  to  those 
in  066  for  crushing  linseed,  revolve  on  a  fixed  horizontal  stone.     This  contrivance  is  the 
most  frequently  used. 

c.  Stampers  are  now  employed  only  in  small  powder-mills.     Frequently  10  to  12 
stamps  made  of  hard  wood  are  placed  in  a  row,  each  stamp  being  fitted  with  a  bronze 
shoe,  the  entire  weight  being  about  i  cwt.     The  stamps  are  moved  by  machinery,  and 
make  from  40  to  60  beats  a  minute.     The  materials  to  be  pulverised  are  placed  in 
mortar-shaped  cavities  in  a  solid  block  of  oak  wood,  each  cavity  containing  16  to  20  Ibs. 
In  Switzerland  hammers  instead  of  the  stampers  are  employed. 

Mixing  the  Ingredients. — The  mixing  is  performed  by  the  aid  of  drums  similar  in 
size  and  shape  to  those  used  in  the  pulverisation,  but  made  of  stout  leather  instead  of 
wood.  The  mixing  of  100  kilos,  of  the  ingredients,  aided  by  the  action  of  150  bronze 
balls,  takes  fully  three  hours,  the  drum  making  ten  revolutions  a  minute.  It  is  usual 
to  moisten  the  materials  with  i  to  2  per  cent,  of  water,  supplied  by  fine  jets  regulated 
by  taps. 

When  stampers  and  mill-work  are  employed,  the  sulphur  and  charcoal  are  first 
separately  pulverised  by  1000  blows,  and  saltpetre  having  been  mixed  with  these 
ingredients  in  the  proper  proportion,  the  machinery  is  again  set  in  motion,  and  at  first, 
after  every  2000  blows,  and  then  after  every  4000  blows,  the  contents  of  the  stamp- 
holes  are  removed  from  the  one  to  the  other,  this  operation  being  repeated  some  six  or 
eight  times.  Where  drums  are  used  for  the  mixing  operation,  the  moistening  takes 
place  after  the  mixture  has  been  removed  to  a  wooden  trough,  where  8  to  10  per  cent, 
of  its  weight  of  water  is  added,  care  being  taken  to  stir  with  a  wooden  spatula. 

Caking  or  Pressing  the  Powder. — This  operation,  which  in  stamping-mills  is  the 
last  of  a  continuous  series,  is  separately  performed  where  other  machinery  is  employed. 
In  the  French  and  German  powder-mills,  the  compression  is  effected  in  a  rolling-mill, 
the  rollers  having  a  diameter  of  o'6  metre.  The  lower  roller  is  made  of  wood,  the  upper 
of  bronze ;  between  the  two  an  endless  piece  of  stout  linen  is  arranged,  and  upon  this 
the  moist  powder  is  placed.  The  cakes  are  i  to  2  centimetres  in  thickness  with  the 
hardness  and  very  much  the  appearance  of  clay-slate. 

The  operation  of  pressing  is  of  great  importance ;  the  stronger  the  pressure  the 
greater  the  quantity  of  active  material  present  in  a  given  bulk,  and  hence  the  larger 
the  volume  of  gas  given  off  by  the  ignition  of  the  powder.  In  many  English  powder- 
mills  the  pressing  is  effected  by  very  powerful  hydraulic  machines,  because,  within 
certain  limits,  the  more  the  materials  are  pressed,  the  more  slowly  the  powder  burns 
when  finished,  while  the  temperature  of  ignition  being  lower,  the  expansion  of  the 
gases  is  less.  If  the  powder  were  finished  either  without  having  undergone  any  pressure 
at  all,  or  with  only  a  slight  pressure,  it  would  act  as  a  detonating-powder,  the  decom- 
position being  instantaneous  throughout  its  entire  mass. 

Granulation  of  the  Cake,  and  Sorting  the  Powder. — The  conversion  of  the  cake  into 
granules  is  effected — 

1.  By  means  of  sieves. 

2.  By  means  of  peculiarly  constructed  rollers,  Congreve's  method ;  or 

3.  According  to  Champy's  method. 

The  granulation  of  gunpowder  by  the  aid  of  sieves  is  carried  on  in  the  following 
manner  : — The  sieves  consist  of  a  circular  wooden  frame,  across  which  a  piece  of  parch- 

2  B 


386  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

ment  is  stretched  perforated  with  holes  ;  the  sieves  are  named  according  to  their 
uses,  and  by  the  size  of  these  holes ;  that  employed  for  breaking  up  the  cake  having 
larger  holes,  and  bearing  a  name  different  from  the  sieves  used  to  produce  the  granules 
this  sieve  again  being  distinguished  from  that  employed  for  sorting  the  powder  into 
the  variously  sized  grains  as  commercially  known.  The  sieves  are  provided  with  a 
so-called  rummer,  a  lens-shaped  disc  made  of  hard  wood,  guaiacum,  box,  or  oak-wood, 
motion  being  imparted  to  the  sieves  by  hand  if  they  are  small,  or  by  suitably  arranged 
machinery  if  they  are  large,  in  which  case  Lefebvre's  granulating-machine  fitted  with 
«ight  sieves  in  an  octagonal  wooden  frame  is  generally  employed. 

Congreve's  granulating-machine  consists  of  three  pairs  of  brass  rollers,  0^65  metre 
in  diameter,  provided  with  diamond-shaped  projections  2  millimetres  high,  the  projec- 
tions of  the  upper  rollers  being  coarser  than  those  of  the  others.  The  broken-up  cake 
is  conveyed  to  the  upper  rollers  by  means  of  an  endless  canvas  sheet.  The  mode  of 
feeding  this  sheet  is  somewhat  peculiar  and  ingenious :  the  loose  bottom  of  a  square 
box  filled  with  coarsely  pounded  cake  is  made  to  rise  slowly  upwards,  and  discharge  the 
«ake  uniformly  upon  the  sheet  through  an  opening  in  the  side  of  the  box.  ,The  cake 
while  passing  through  the  rollers  is  granulated,  and  then  showered  upon  two  sets  of 
wire-gauze  sieves  to  which  a  to-and-fro  motion  is  imparted.  Below  these  sieves  again 
is  a  frame  containing  wire-gauze,  the  meshes  of  which  are  too  small  to  admit  of  the 
passage  of  ordnance  powder,  while  the  dust  and  cartridge-powder  readily  fall  through 
upon  another  wire-gauze,  the  meshes  of  which  retain  the  rifle-powder  but  let  the  dust 
pass.  The  quantity  of  dust  made  by  tbe  Congreve  machine  is  very  small,  owing  to 
the  fact  that  the  rollers  do  not  crush  but  break  the  cake.  Champy's  method,  by  which 
&  very  round-grained  powder  is  obtained,  is  performed  in  the  following  manner : — 
Through  the  hollow  axis  of  a  wooden  drum  a  copper  tube,  perforated  with  very  small 
holes,  is  carried,  and  from  these  holes  water  sprouts  in  a  fine  spray  upon  the  broken-up 
powder-cake  placed  in  the  drum,  to  which  a  comparatively  rapid  motion  is  imparted. 
Each  drop  of  water  forms  the  nucleus  of  a  grain  of  powder,  which  is  constantly  in- 
creasing in  size  by  being  turned  round  in  the  midst  of  a  mass  of  damp  powder-cake ; 
the  rotation  of  the  drum  is  discontinued  as  soon  as  the  grain  has  attained  a  sufficient 
size.  The  powder  thus  obtained  is  almost  perfectly  globular,  but  not  of  the  same  size ; 
the  sorting  is  effected  by  means  of  sieves,  the  over-sized  grains  being  returned  to  the 
drum,  as  well  as  the  under-sized  grains,  which  become  the  nuclei  of  proper-sized  grain. 
According  to  the  Berne  method,  round-grained  powder  is  prepared  by  causing  the 
-angular-shaped  powder  to  be  rotated  in  stout  linen-bags ;  but  by  this  plan  much  dust 
is  formed. 

Polishing  the  Granulated  Powder. — The  aim  of  this  operation  is  to  impart  symmetry 
to  the  grain,  and  to  separate  all  the  dust.  It  is  performed  in  drums  similar  to  those 
described  above ;  5  cwts.  of  the  powder  is  polished  at  a  time,  the  drums  rotating  slowly 
for  a  few  hours. 

In  some  countries  the  polishing  is  effected  by  placing  the  powder  in  casks  internally 
provided  with  quadrangular  rods.  In  Holland,  Dr.  Wagner  states  that  some  black- 
lead  is  added  to  the  powder  during  this  operation  to  prevent  ignition,  but  this  is  not 
generally  done.  Highly-polished  powder  does  not  readily  attract  moisture,  and  is  to 
be  preferred  in  a  very  damp  climate. 

Drying  the  Powder. — It  is  clear  that  this  operation  requires  very  great  care  in 
more  than  one  respect.  In  small  powder-works  the  powder  is  sometimes  dried  by 
exposure  to  the  heat  of  the  sun,  being  spread  out  on  canvas  sheets  stretched  in  wooden 
frames  ;  or  the  drying-room  is  heated  by  a  stove.  In  large  powder-mills  other  methods 
of  drying  the  powder  are  general. 

The  quality  of  the  powder  very  much  depends  on  the  care  bestowed  upon  the 
drying.  A  too  rapid  drying  entails  the  following  disadvantages :  a.  The  powder  may 


SECT,  in.]  EXPLOSIVES.  387 

be  very  wet  and  not  polished ;  coarse  ordnance  and  ordinary  military  powder  is  never 
polished,  and  hence  blackens  the  hands ;  while,  although  the  water  is  driven  off,  the 
nitre  is  carried  to  the  surface  of  the  grain,  which  thereby  cakes  together,  b.  By  the 
too  rapid  evaporation  of  the  water,  channels  and  cracks  are  made  in  the  grain,  impair- 
ing its  density,  increasing  its  bulk,  and  rendering  it  more  hygroscopic,  c.  Lastly, 
rapid  drying  entails  a  large  amount  of  dust.  For  these  reasons  gunpowder,  before 
being  placed  in  the  drying-rooms,  is  exposed  for  some  time  to  a  gentle  heat  in  a  well- 
ventilated  room,  the  heat  from  a  waste  steam-pipe  being  sufficient. 

Sifting  the  Dust  from  the  Powder. — Having  been  dried,  the  powder  is  sometimes 
glazed,  as  it  is  termed ;  that  is  to  say,  again  polished  in  the  manner  above  described ; 
but  generally  this  second  polishing  is  dispensed  with,  and  the  dry  powder  cleansed 
from  the  dust  which  adheres  to  it,  by  being  placed  in  bags,  made  of  a  peculiar  kind  of 
woollen  fabric,  and  arranged  in  frame-work  to  which  a  to-and-fro  motion  is  given  by 
machinery,  the  fine  dust  passing  between  the  threads  of  the  fabric  into  a  box.  The 
loss  thus  occasioned  amounts  on  an  average  to  0*143  Per  cen^-j  the  dust  consisting 
chiefly  of  charcoal. 

Properties  of  Gunpowder. — Good  powder  is  recognised  by  the  following  properties  : 
i.  Its  colour  should  be  slate-black;  when  blue-black  it  indicates  that  the  powder 
contains  too  much  charcoal,  while  a  deep  black  colour  shows  the  powder  to  be  damp. 
If  the  charcoal  employed  was  the  so-called  charbon  roux,  the  colour  of  the  powder  will 
be  a  brown-black.  2.  It  should  not  be  too  much  polished  so  as  to  shine  like  burnished 
black-lead.  Small  shining  specks  indicate  that  the  saltpetre  has  crystallised  on  the 
surface.  3.  The  grains  should  be  uniform  in  size,  unless,  of  course,  two  differently 
sized  powders  have  been  mixed.  4.  The  grain  should  crack  uniformly  when  strongly 
pressed,  it  should  withstand  pressure  between  the  fingers,  and  should  not  be  readily 
crushed  to  powder  when  pressed  between  the  hands.  5.  When  pulverised  the  mass 
should  feel  soft ;  hard  sharp  specks  show  that  the  sulphur  has  not  been  well  pulverised. 

6.  Powder  should  not  blacken  the  back  of  the  hands  or  a  sheet  of  white  paper  when 
gently  rubbed.     If  it  does  so,  there  is  either  powder-dust  or  too  much  moisture. 

7.  When  a  small  heap  of  powder  is  ignited  on  paper  the  combustion  should  be  rapid, 
completely  consuming  the  powder  and  not  setting  fire  to  the  paper.     If  black  specks 
remain,  the  powder  either  contains  too  much  charcoal,  or  it  is  an  indication  that  that 
substance  has  been  badly  incorporated  with  the  rest  of  the  materials.     Yellow  streaks 
left  after  the  ignition  show  the  same  defects  for  the  sulphur.     If  no  grains  of  powder 
remain,  it  is  a  proof  that  the  powder  was  not  well  mixed ;  when  any  remaining  grains 
of  powder  cannot  be  separately  ignited,  the  saltpetre  used  was  impure.     If  the  powder 
on  being  ignited  sets  fire  to  the  paper,  it  is  a  proof  that  it  is  either  damp  or  of  very 
inferior  quality. 

Gunpowder  can  absorb  more  than  14  per  cent,  of  moisture  from  the  air ;  if  the 
quantity  of  water  thus  taken  up  is  not  above  5  per  cent.,  the  powder,  on  being  gently 
dried,  reassumes  its  former  activity ;  but  if  the  quantity  of  water  absorbed  exceeds 
that  amount,  the  gunpowder  will  not  burn  off  rapidly,  and  when  dried  the  single  grains 
become  covered  with  an  efflorescence  of  saltpetre,  of  course  impairing  the  com- 
position and  active  qualities  of  the  powder.  Even  what  is  termed  dry  powder  contains 
at  least  2  per  cent,  of  hygroscopic  moisture.  Powder  can  be  exploded  by  a  heavy 
blow  as  well  as  by  an  increase  of  temperature,  and  as  regards  its  explosion  by  a  blow, 
very  much  depends  upon  the  material  upon  which  it  is  placed  and  with  which  the 
blow  is  imparted.  The  following  list  exhibits  in  decreasing  order  the  materials  between 
which  a  blow  most  readily  ignites  powder :  Iron  and  iron,  iron  and  brass,  brass  and 
brass,  lead  and  lead,  lead  and  wood,  copper  and  copper,  copper  and  bronze.  For  this 
reason  gunpowder  magazines  are  provided  with  doors  turning  upon  bronze  and  copper 
hinges,  the  locks  also  being  of  copper.  When  dry  powder  is  rapidly  heated  to  above 


3SS  CHEMICAL  TECHNOLOGY.  [SECT.  ra. 

300°  it  explodes.  Even  if  only  a  very  small  portion  of  the  powder  is  thus  rapidly 
elevated  in  temperature,  the  entire  quantity,  be  it  large  or  small,  is  exploded ;  hence 
a  very  small  quantity  touched  by  a  red-hot  or  burning  body  is  sufficient  to  effect  an 
explosion.  It  is  generally  held  that  the  charcoal  is  first  ignited,  and  that  it  spreads 
the  ignition  to  the  other  materials.  Although  Mr.  Hoarder  found  by  experiment  that 
powder  does  not  ignite  when  touched  with  a  red-hot  platinum  wire  while  under  the 
receiver  of  an  air-pump,  Professors  v.  Schrotter  and  Abel  proved  that  gunpowder  so 
placed  ignited  rapidly  when  heated  by  a  spirit-lamp. 

Composition  of  Gunpowder. — Gunpowder  consists  very  nearly  of  2  molecules  of 
saltpetre,  i  molecule  of  sulphur,  and  3  of  charcoal.  Accordingly  100  parts  of  powder 

contain — 

Saltpetre 74*84 

Sulphur 11-84 

Charcoal  (No.  I.) 13 -32 

The  above  figures  approximately  express  the  composition  of  the  best  kinds  of  sport- 
ing and  rifle-powder.  Ordinary  powders,  such  as  blasting-powder,  consists  of  nearly 
equal  molecules  of  potassium  nitrate  and  sulphur,  with  6  molecules  of  charcoal. 
Accordingly  100  parts  contain — 

Saltpetre *  "...     66-03 

Sulphur 10*45 

Charcoal  (No.  II.) 23-52 

Products  of  the  Combustion  of  Powder. — Drs.  Bunsen  and  Schischkoff  found  the 
composition  of  a  sporting  and  rifle-powder  to  be,  in  100  parts,  as  follows  : 

Saltpetre •     78'99 

Sulphur  .' 9-84 

Carbon     . 7-69 

Charcoal,      Hydrogen         . .0-41 

consisting  of    Oxygen    . 3-07 

.Ash traces 

The  residue  of  this  powder  after  combustion  was  found  to  consist  of — 
Potassium  sulphate  .        .        .        .        .        .56-62 

„          carbonate         ......     27-02 

„  hyposulphite 7-57 

,,  sulphuret          .         .        .        ,         .         .       1-06 

Hydrated  potassium  oxide  (caustic  potassa)     .        .       1-26 
Potassium  sulphocyanide         .        .        .        .        .      o'86 

Saltpetre 5-19 

Carbon      .         .         .         .         .        .        .  '      .         .       0*97 

Ammonium  carbonate \ 

Sulphur [  traces 

100-55 

It  appears  from  this  analysis  that  the  residue  left  after  ignition  of  the  gunpowder 
consists  essentially  of  potassium  sulphate  and  carbonate,  and  not,  as  has  been  formerly 
stated,  of  potassium  sulphide.  The  composition  of  the  smoke  of  the  powder  was 
ascertained  to  be — 

Potassium  sulphate 64-29 

„          carbonate 23-48 

„          hyposulphite 4-90 

„          sulphide .        — 

Caustic  potassa 1-23 

Potassium  sulphocyanide 0-55 

Saltpetre  .        . 2-48 

Carbon  (charcoal)     .         .         .        .         .         .        .1-86 

Ammonium  sesquicarbonate 0*11 

Sulphur    ....... 


SECT.   III.] 


EXPLOSIVES. 


389 


From  these  figures  it  is  clear  that  the  smoke  of  gunpowder  consists  essentially  of 
the  same  substances  as  the  residue  from  the  combustion,  the  only  difference  being  that 
the  sulphur  and  potassium  nitrate  of  the  powder  have  been  more  completely  converted 
into  potassium  sulphate,  while,  instead  of  the  potassium  sulphide,  ammonium  car- 
bonate makes  its  appearance.  100  parts  by  volume  of  the  gaseous  products  of  the 
combustion  were  found  to  consist  of — 


Carbonic  acid     .        . 

Nitrogen 

Carbon  monoxide 

Hydrogen  . 

Sulphuretted  hydrogen 

Oxygen 

Nitrous  oxide 


52-67 

41-12 

3'88 

I  '21 

0-60 


The  solid  residues  of  combustion  formed  during  the  generation  of  the  gases  were 

found  to  be — 

Potassium  sulphate 62*10 

„         carbonate  .......  18*58 

„         hyposulphite 4 '80 

„         sulphide     .......  3-13 

„         sulphocyanide 0*45 

„         nitrate 5 '47 

Charcoal 1*07 

Sulphur .         .  0*20 

Ammonium  sesquicarbonate         .         .  4-20 


The  decomposition  of  powder  by  its  ignition  may  be  represented  by  the  following 
f  ormulse : — 

Grm. 
'K2SO4 0-422 


i  gramme. 
>of  powder 


K2CO,  . 

.        . 

0-126 

K2S20,  . 

. 

0-032 

Kesidue 
0-680    " 

K2S 
KCNS  . 
KNO,    . 

1  •; 

0*021 
0-OO3 
0-037 

C 

.     . 

0-007 

Saltpetre 

•     0789) 

s 

O'OOI 

Sulphur 
Charcoal 

;°;^   yields  after 
H  0*004    combustion" 

(NH4)2CO,  +  2(NH4HCOS) 
Grm. 

fN          ...   0-0990  = 

0*028 
c.c. 

79-40 

(o  0-030' 

GfclSCS         I  f^f^ 

.     O'2OIO   = 

10171 

01IA.      -^°U 

.     O-OO9O   = 

7-49 

34     |H 

.     O-OOO2   = 

2*34 

SH. 

.     O'OOlS   = 

1*16 

0*994     |Q  —* 

.     0-OOI4  = 

1*00 

193-10 


The  proportions  of  the  mixtures  used  in  different  countries  for  military  powder  are  : 


Saltpetre 
Sulphur  . 
Charcoal 


Germany. 
•     74 
.     10 
16 


Russia. 

75 
10 


Britain. 

75 
IO 

15 


France. 
74 
I0i 

I  Si 


Since  the  American  civil  war  compressed  gunpowder  has  been  introduced,  especially 
the  so-called  "prismatic  powder."  It  is  merely  ordinary  powder,  which  has  been 
•compressed  in  hexagonal  moulds.  The  pressed  grain  has  the  shape  of  a  smooth  hexa- 
gonal prism  (Fig.  341)  perforated  by  six  tubes.  When  ignited,  the  grain  burns  both 
from  without  and  from  within,  in  consequence  of  the  tubes.  Yet  it  burns  more  slowly 
than  finely  granulated  powder,  and  imparts  a  greater  force  to  the  projectile. 


39<> 


CHEMICAL   TECHNOLOGY. 


[SECT.  in. 


Fig.  341. 


Testing  Gunpowder. — In  order  to  determine  the  strength  or  projectile  force  of  gun- 
powder, and  to  ascertain  which  sample  is  dependent  for  equality  of  composition  on  the 
mechanical  treatment  the  powder  has  undergone,  the  following  apparatus  are  used  :— 
Test  mortar,  rod  testing  machine,  lever  testing  machine,  ballistic  pendulum,  and  chrono- 
scope.  The  first  of  these  contrivances  is  a  piece  of  heavy  ordnance,  charged  with  92 

grammes  of  powder,  and  a  ball  weighing  29-4  kilos.,  the 
mortar  being  placed  at  an  angle  of  45°.  The  bore  of  the 
mortar  is  191  millimetres  in  diameter  by  239  in  depth. 
Powder  of  good  quality  should  propel  the  ball  a  distance  of 
225  metres,  and  frequently  the  ball  is  carried  a  distance  of 
250  to  260  metres.  The  rod  gunpowder  testing  apparatus 
consists  of  a  mortar  placed  vertically,  and  which,  when 
charged  with  22  to  25  grammes  of  powder,  lifts  a  weight 
of  8  Ibs.,  made  to  move  between  toothed  rods ;  by  the 
height  this  weight  is  raised,  springs  attached  to  the  weight 

fastening  in  the  notches  of  the  rods   and  holding   it,  the  quality  of   the  powder  is 
judged. 

Pyrotechnics. — Chemical  Principles  of  Pyrotechny. — Under  the  name  of  fireworks  we 
include  certain  mixtures  of  combustible  substances  employed  as  signals,  as  destructive 
agents  (for  instance,  congreve  rockets),  and  for  purposes  of  display. 

The  various  forms  are,  according  to  the  end  in  view,  so  contrived  as  to  burn  off 
either  rapidly  or  slowly,  and  with  more  or  less  emission  of  gaseous  matter,  heat,  and 
light.  These  mixtures  are  mainly  distinguished  as  heat-producing,  ignition  com- 
municators (technically  termed  a  fuse),  and  light-producing.  The  principle  of  the 
rational  manufacture  of  fireworks,  applying  the  word  in  its  extended  sense,  is  that 
neither  any  excess  of  the  combustible  nor  of  the  combustion  promoting  and  supporting 
agents  should  be  employed,  and  that  unavoidable  accessory  materials,  viz.,  such  as  are 
intended  only  to  keep  the  essential  ingredients  in  a  certain  required  shape,  the  paper 
casings,  &c.,  be  in  precisely  the  quantity  required.  The  best  proportions  of  the  com- 
bustible and  combustion-supporting  substances  can  be  readily  ascertained  by  theoretical 
calculations;  for  instance,  it  will  be  evident  that  a  mixture  of  2  equivalents  of  salt- 
petre and  i  equivalent  of  sulphur  (i),  or  a  mixture  of  2  equivalents  of  saltpetre  and 
3  equivalents  of  sulphur  (2),  is  in  each  instance  wrong  ;  in  the  latter,  too  much  of  the 
combustible  body  is  used  ;  and  in  the  former  case,  too  much  of  the  supporter  of  com- 
bustion is  employed — 

(1)  S  can  take  up  from  2KNO3  at  most  30 ;  consequently,  30  remain  inactive. 

(2)  38  and  2KNO3  yield  either  K2S  and  2S03,  or  a  mixture  of  K2SO4,  K2S,  and 

S02,  in  each  case  some  sulphur  remaining  unburnt. 

We  have  to  bear  in  mind,  however,  that  it  is  not  always  possible  to  elucidate  theo- 
retically the  decomposition  of  firework  mixtures,  as  the  affinity  of  the  substances  which 
react  upon  each  other  is  not  well  known,  and  depends  on  accessory  conditions  and  com- 
paratively unknown  influences.  It  will  require  a  more  advanced  knowledge  of  the 
products  of  the  decomposition  of  the  different  substances  and  their  specific  heat  before 
we  can  predict  with  some  degree  of  certainty  the  best  mixtures.  As  regards  the 
existing  mixtures,  they  are  the  result  of  a  lengthy  series  of  experiments,  really  made 
by  rule  of  thumb,  though  with  a  certain  correspondence  with  the  best  composition 
theory  can  give,  that  is  to  say,  many  of  these  mixtures  have  been  somewhat  modified 
and  improved  by  modern  science. 

The  More  Commonly  Used  Firework  Mixtures. — These  mixtures  consist  mainly  of 
saltpetre,  sulphur,  and  charcoal,  either  in  the  same  proportions  as  those  in  use  for  gun- 
powder, or  with  an  excess  of  sulphur  and  charcoal.  Some  mixtures  contain,  instead  of 
saltpetre,  potassium  chlorate  and  other  salts,  not  always  essential  to  the  combustion,  but 


SECT,  in.]  EXPLOSIVES.  391 

intended  either  to  intensify  the  light  evolved  or  impart  to  it  a  distinctive  colour,  as  in 
signals  and  Bengal  lights. 

Gunpowder  is  used  in  fireworks  when  it  is  desired  that  there  should  be  projectile 
force.  A  slower  combustion  of  the  powder  is  obtained  partly  by  the  use  of  so-called 
meal  powder,  that  is,  pulverised,  not  granulated  powder,  partly  by  compressing  the 
mixture.  If,  however,  it  is  intended  to  produce  loud  reports,  granulated  powder 
is  used. 

Saltpetre  and  Sulphur  Mixture. — This  consists  of  2  molecules  (75  parts  by  weight) 
of  saltpetre,  and  i  molecule  (25  parts  by  weight)  of  sulphur,  and  is  used  as  the  chief 
constituent  of  such  firework  mixtures  as  are  intended  to  burn  off  slowly  and  evolve  a 
strong  light.  However,  this  mixture  is  not  used  by  itself,  for  two  reasons,  viz.,  it  does 
not  develop  a  sufficient  degree  of  heat  to  support  its  continued  combustion,  and  it  does 
not  possess  a  sufficient  projectile  force,  being  capable  of  producing  in  the  best  possible 
condition  of  complete  ignition  only  i  molecule  of  sulphurous  acid — 

2KN03  +  S  =  K2SO4  +  S02  +  N; 

that  is  to  say,  i  part  by  bulk  of  this  mixture  only  yields  7 '28  volumes  of  gas.  For 
these  reasons  the  saltpetre-sulphur  mixture  is  employed  with  charcoal  or  floury  gun- 
powder. 

Grey-coloured  Mixture.— Such  a  mixture,  sanctioned  by  long  use,  is  that  known  as 
grey-coloured  mixture,  consisting  of  93*46  per  cent,  of  saltpetre-sulphur  and  6-54  of 
floury  gunpowder.  This  mixture  is  the  chief  constituent  of  other  compounds  intended 
to  burn  slowly,  emitting  at  the  same  time  a  brilliant  light,  owing  to  the  fact  that  the 
potassium  sulphate  formed  by  the  combustion  acts  similarly  to  a  solid  brought  to  an 
incandescent  state.  All  mixtures  intended  to  emit  light,  including  coloured  lights,  are 
prepared  upon  the  same  principle,  that  the  salt  which  is  to  give  colour  shall  be  non- 
volatile at  the  temperature  of  combustion. 

Potassium  Chlorate  Mixtures ;  Friction  Mixtures ;  Percussion  Powders. — This  salt, 
KC103,  when  in  presence  of  combustible  substances,  gives  off  its  oxygen  to  the  latter 
more  readily,  rapidly,  and  completely  than  saltpetre ;  accordingly,  this  salt  is  used  in 
all  mixtures  in  which  it  is  desired  to  combine  rapid  ignition  with  combustion.  Formerly 
a  mixture  of  80  parts  by  weight  of  potassium  chlorate  and  20  parts  of  sulphur  was 
added  to  intensify  and  quicken  the  combustion  of  mixtures  consisting  of  more  slowly 
burning  salts.  A  mixture  of  sulphur,  charcoal,  and  potassium  chlorate  constitutes  an 
active  percussion  powder.  A  mixture  of  equal  parts  by  weight  of  black  antimony 
sulphide  and  potassium  chlorate  is  used  for  the  purpose  of  discharging  ordnance 
by  means  of  a  percussion  tube  put  in  the  touch-hole  of  the  gun.  Sir  William 
Armstrong  uses  for  this  purpose  a  mixture  of  amorphous  phosphorus  and  potassium 
chlorate. 

Mixture  for  Igniting  the  Cartridges  of  Needle-guns.—  This  mixture  consists  either 
of  potassium  chlorate  and  black  antimony  sulphide,  or  a  compound  containing  mercury 
fulminate.  The  following  is  a  good  preparation : — 16  parts  of  potassium  chlorate, 
8  of  black  antimony  sulphide,  4  of  flour  of  sulphur,  and  i  of  charcoal  powder  are 
moistened  with  either  gum  or  sugar-water,  and  about  5  drops  of  nitric  acid  added. 
A  small  quantity,  technically  known  as  the  pill,  is  placed  in  the  cartridge  and  ignited 
by  the  friction  produced  by  the  sudden  passage  of  the  steel  needle  through  it.  In  this 
country  either  the  above  or  a  mixture  of  amorphous  phosphorus  and  potassium 
chlorate  is  used.  Leaving  the  silver  and  mercury  fulminates  out  of  the  question, 
the  explosive  bodies  and  their  applicability  to  warlike  purposes  and  military  pyro- 
techny  have  not  been  sufficiently  investigated.  Nitromannite  or  fulminating  mannite, 
the  alkaline  picrates,  and  nitroglycerine,  of  which  we  shall  presently  treat  more  fully, 
especially  deserve  notice.  M.  Dessignolles,  who  suggests  that,  instead  of  saltpetre, 
potassium  picrate  should  be  used  in  the  manufacture  of  gunpowder,  states  that  quite 


392  CHEMICAL  TECHNOLOGY.  [SECT.  ra. 

different  products  are  formed  by  the  ignition  of  potassium  picrate,  when  effected  in 
the  open  air  (a,  or  under  pressure  (6) : — 

a.  2C6H2K(N02)30  =  K2C03  +  5C  +  3N  +  NO  +  N02  +  4  C02  +  CHN. 

Potassium  picrate. 

b.  2C6H,K(N02)30  =  K2C03  +  6C  +  sN  +  sCO2  +  2H2  +  O. 

Potassium  picrate. 

Fulminating  aniline,  diazobenzol  chromate,  obtained  by  the  action  of  nitrous  acid 
upon  aniline,  and  the  precipitation  of  the  product  by  the  aid  of  a  hydrochloric  acid 
solution  of  potassium  bichromate,  is,  according  to  MM.  Caro  and  Griess,  an  efficient 
substitute  for  fulminating  mercury. 

Heat-producing  Mixtures. — These  consist  chiefly  of  floury  gunpowder  and  grey  mix- 
ture, to  which  are  added  certain  organic  substances,  as  pitch,  resin,  tar,  igniting  readily, 
but  consumed  more  slowly  than  any  firework.  The  heat  generated  by  the  combustion 
of  fireworks  is  much  higher  than  is  required  to  ignite  wood,  but  not  of  sufficient 
duration  to  cause  the  thorough  burning  of  the  wood ;  hence  the  addition  of  tar,  &c. 

Coloured  Fires. — The  salts  employed  to  produce  coloured  flames  are — barium,  stron- 
tium, and  sodium  nitrates,  and  the  ammoniacal  copper  sulphate.  The  so-called  cold 
fuse  mixture,  composed  of  grey  mixture,  flour  gunpowder,  and  antimony  sulphide, 
moistened  with  brandy  and  then  mixed,  produces  a  white  flame.  The  mixtures 
for  coloured  fires  used  in  artillery  laboratories  are  the  undermentioned,  calculated  for 
100  parts  of  each  mixture : — 

a.  b.                     c.                     d.  e. 

Green.  Red.  Yellow.  Blue.  White. 

1.  Potassium  chlorate      ....     327  ...  297  ...  —  ...  54-5  ...  — 

2.  Sulphur 9-8  ...  17-2  ...  23-6  ...  ...  20 

3.  Charcoal 5-2  ...  17  ...  3-8  ...  i8'i  ...  — 

4.  Barium  nitrate 52-3  ...  —  ...  —  ...  —  ...  — 

5.  Strontium   „ —  ...  457  ...  —  ...  —  ...      

6.  Sodium        „ —  ...  —  ...  9-3  ...  —  ...      

7.  Ammoniacal  copper  sulphate     .         .      —  ...  —  ...  —  ...  27-4  ...  — 

8.  Saltpetre —  ...  —  ...  62'8  ...  —  ...  60 

9.  Black  antimony  sulphide  .         .        .      —  ...  57  ...  —  ...  —  ...  e 
IO.  Flour  gunpowder        .        .        .        .      —  ...  —  ...  ...  ...  ft 

It  is  hardly  necessary  to  mention  that  great  care  is  required  in  mixing  these  materials, 
and  that  each  ingredient  ought  be  pulverised  separately. 

According  to  M.  Uhden,  a  beautiful  white  flame  edged  with  blue  is  obtained  by  the 
ignition  of  the  following  mixture  : — 20  parts  of  saltpetre,  5  of  sulphur,  4  of  sulphuret 
of  cadmium,  and  i  of  charcoal.  Thallium  chloride  with  other  ingredients  yields  a 
beautiful  green  flame.  Magnesium  was  used  during  the  Abyssinian  war  in  various 
ways  when  a  brilliant  light  was  required.  The  chlorates  of  the  alkaline  earths  and 
sodium  chlorate  would  be  preferable,  were  it  not  for  the  expense,  and  for  the  facts 
that  these  salts  are  rather  hygroscopic  and  liable  to  spontaneous  combustion.  The 
barium  and  strontium  carbonates  are  sometimes  used  instead  of  the  nitrate.  Ac- 
cording to  MM.  Dessignolles  and  Castelhaz,  most  brilliant  coloured  flames  are  obtained 
with  ammonium  picrate  in  the  following  proportions  : — 

Yellow   f  Ammoniura  picrate  .  .     50 

(Ferrous  „  .  N  .  50 

Green  I  Ammonium  „  .  .  48 

( Barium  nitrate  .  .  •  S2 

j^e(j  |  Ammonium  picrate  .  .  54 

1  Strontium  nitrate     .  .  .46 

More  Recent  Explosives. — Dessignolles  proposes  to  substitute  potassium  picrate  for 


SECT,  in.]  EXPLOSIVES.  393 

saltpetre  in  the  manufacture  of  gunpowder.  The  fearful  power  of  picrate  powder, 
which  is  also  known  as  Bobosuf  powder,  Dessignolles  powder,  and  Fontaine  powder,  is 
fully  known.  Mellinite  consists  essentially  of  picric  acid.  Nitromannite, 

C6H8N6018  -  C6H8(O.N02)6, 

is  formed  on  dissolving  mannite  in  fuming  nitric  acid,  and  separates  out  on  the  addition 
of  concentrated  sulphuric  acid.  It  crystallises  from  boiling  alcohol  in  fine  silky 
needles,  which,  if  heated  to  120°,  burn  with  detonation,  and  explode  violently  if  struck. 
Nitromannite  has  been  substituted  for  fulminating  mercury  as  a  material  for  per- 
cussion caps.  It  is  said  to  undergo  decomposition  on  long  keeping.  Nitrised  cane- 
sugar  has  been  in  transient  use  as  an  explosive  agent  under  the  name  Vixorite. 
Fulminating  aniline  (diazobenzol  chromate),  made  by  the  action  of  nitrous  acid  upon 
aniline  and  precipitating  the  product  with  potassium  dichromate,  has  also  been  pro- 
posed as  a  substitute  for  mercury  fulminate.  Hellhoffite  is  a  solution  of  nitrobenzol 
in  nitric  acid.* 

Nitroglycerine  (nitroleum,  pyroglycerine,  glyceryl  trinitrate,  or  glono'ine). — This  sub- 
stance was  discovered  in  1847  by  Dr.  A.  Sobrero,  while  a  student  in  the  laboratory  of 
Professor  Pelouze,  at  Paris.  Since  the  year  1862,  M.  Alfred  Nobel,  a  Swede,  has  manu- 
factured this  liquid  on  the  large  scale.  The  formula  of  nitroglycerine  is  C3H5N3O9  or 

•C1  IT     1  *       C  H 

/xrr»5\  \®3>  consequently,  it   consists  of  glycerine,     Vj5 1 0  ,  in  which  3  atoms  of  H 

\*Wj/r  "-3) 

•have  been  replaced  by  3  atoms  of  NO2.    100  parts  of  nitroglycerine  yield  on  combustion — 

Water 20 'O  parts 

Carbonic  acid       .        .        .        .  58*0      „ 

Oxygen 35,, 

Nitrogen i8'5      „ 

lOO'O       „ 

As  the  specific  gravity  of  nitroglycerine  is  i'6,  i  part  by  bulk  will  yield  on  com- 

•bustion — 

Aqueous  vapour     .         .        .'        -554  volumes 
Carbonic  acid         ....    469        „ 

Oxygen 39        „ 

Nitrogen 236        „ 

1298 

According  to  experiments  made  in  Belgium,  the  combustion  of  nitroglycerine  does 
not  yield  free  oxygen,  but  a  large  quantity  of  nitrous  oxide ;  hence,  the  following 
•equation  will  give  some  idea  of  the  mode  of  explosion  : — 

/Carbonic  acid,  6COr 
2  molecules  of          )  _  J  Water,  5H2O. 
Nitroglycerine,  CSHSNSOJ  ~  j  Nitrous  oxide,  N2O. 
V  Nitrogen,  N4. 

M.  Nobel  states  that  the  heat  set  free  by  explosion  causes  the  gases  to  expand  to  eight 
times  their  bulk ;  accordingly,  i  volume  of  nitroglycerine  will  yield  10,384  volumes  of 
.gas,  while  one  part  by  bulk  of  powder  only  yields  800  volumes  of  gas ;  the  explosive 
force  of  nitroglycerine  is,  therefore,  to  that  of  powder — 

By  volume  as  13  :  i, 
By  weight  as    8  :  I. 

In  order  to  prepare  nitroglycerine,  very  strong  nitric  acid,  density  95°  to  98°  Tw.  = 
1-476  to  i -49  sp.  gr.,  is  mixed  with  twice  its  weight  of  concentrated  sulphuric  acid, 
3300  grammes  of  this  mixture,  thoroughly  cooled,  are  poured  either  into  a  glass 

*  Compare  Eissler,  Handbook  of  Modern  Explosives.    London  :  Lockwood  &  Son. 


394  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

flask  or  into  a  glazed  earthenware  jar,  placed  in  a  pan  of  cold  water,  and  there  is 
next  gradually  added  500  grammes  of  concentrated  and  purified  glycerine,  having  a 
density  at  least  of  49°  to  51°  Tw.  =  sp.  gr.  1-246  to  1-256,  care  being  taken  to  stir 
constantly.  According  to  Dr.  E.  Kopp's  recipe  (1868)  the  acid  mixture  should  consist 
of  3  parts  of  sulphuric  acid  at  153°  Tw.  =  1-767  sp.  gr.,  and  i  part  of  fuming  nitric  acid. 
To  350  grammes  of  glycerine  2800  grammes  of  the  acid  mixture  are  added ;  and  in  per- 
forming this  operation  care  should  be  taken  to  avoid  any  perceptible  heating  for  fear 
of  converting  by  a  violent  reaction  the  glycerine  into  oxalic  acid.  The  mixture  is  now 
left  to  stand  for  five  or  ten  minutes,  and  afterwards  poured  into  five  or  six  times  its 
bulk  of  very  cold  water,  to  which  a  rotatory  motion  has  been  imparted.  The  newly 
formed  nitroglycerine  sinks  to  the  bottom  of  the  vessel  as  a  heavy  oily  liquid, 
which  is  washed  by  decantation ;  but  if  not  intended  for  transport — and  experience 
has  proved  the  transport  of  nitroglycerine  to  be  highly  dangerous — the  washing  may  be 
dispensed  with,  as  neither  any  adhering  acid  nor  water  impairs  the  explosive  properties. 
Nitroglycerine  is  now  generally  made  on  the  spot  in  America  and  elsewhere  by  those 
whom  experience  in  mining,  quarrying,  and  engineering  matters  has  taught  the  real 
value  of  this  very  powerful  agent. 

Nitroglycerine  is  an  oily  fluid  of  a  yellow  or  brown  colour,  heavier  than  and 
insoluble  in  water,  soluble  in  alcohol,  ether,  and  other  fluids ;  when  exposed  to  con- 
tinuous cold,  not  of  great  intensity,  it  becomes  solidified,  forming  long  needle-shaped 
crystals.  The  best  means  of  exploding  nitroglycerine  is  a  well-directed  blow,  neither 
a  spark  nor  a  lighted  body  will  cause  the  ignition,  which  even  with  a  thin  layer 
takes  place  with  difficulty,  only  part  being  consumed.  A  glass  bottle  filled  with 
nitroglycerine  may  be  smashed  to  pieces  without  causing  the  contents  to  explode. 
Nitroglycerine  may  even  be  gently  heated  and  volatilised  without  decomposition  or 
combustion,  provided  violent  boiling  is  carefully  prevented.  When  a  drop  of  nitro- 
glycerine is  caused  to  fall  on  a  moderately  hot  piece  of  cast-iron  the  liquid  is  quietly 
volatilised ;  if  the  iron  is  red-hot  the  liquid  burns  off  instantaneously,  just  as  a  grain 
of  powder  would  do  under  the  same  conditions ;  if,  however,  the  iron  is  at  that  heat 
which  will  cause  the  immediate  boiling  of  the  nitroglycerine,  it  explodes  with  great 
force.  Nitroglycerine,  especially  if  sour  and  impure,  is  liable  to  spontaneous  decom- 
position, which,  accompanied  by  the  formation  of  gas  and  of  oxalic  acid,  may  have 
been  the  proximate  cause  of  some  of  the  dreadful  explosions  of  this  substance,  it  being 
surmised  that  the  pressure  exerted  by  the  generated  gases  upon  the  fluid  in  hermeti- 
cally closed  vessels  had  something  to  do  with  the  occurrences.  On  this  account  M.  K. 
last  advises  that  vessels  containing  nitroglycerine  should  be  only  loosely  stoppered,  or 
if  being  transported  provided  with  safety-valves.  Nobel  secures  nitroglycerine  from 
explosion  by  dissolving  it  in  pure  wood-spirit,  from  which  it  may  be  again  separated 
by  the  addition  of  a  large  quantity  of  water.  Mr.  Seeley  on  this  score  observes  that  :— 
i.  The  wood -spirit  is  expensive,  and  lost  in  the  large  quantity  of  water  required  for 
precipitating  the  nitroglycerine;  2.  Wood-spirit,  being  volatile,  may  evaporate,  and 
leave  the  nitroglycerine  unprotected ;  3.  There  is  a  chance  of  chemical  action  between 
these  bodies ;  4.  The  vapour  of  wood-spirit  is  very  volatile,  and  forms  with  air  an 
explosive  mixture.  Many  suggestions  have  been  made  as  to  rendering  nitroglycerine 
safe  to  warehouse ;  among  them  may  be  noted  the  mixing  with  pulverised  glass  in  a 
manner  similar  to  Gale's  process  for  gunpowder.  Wurtz  recommends  the  mixture 
of  nitroglycerine  with  equally  dense  solutions  of  either  zinc,  calcium,  or  magnesium 
nitrates,  so  as  to  form  an  emulsion,  the  nitroglycerine  being  recovered  simply  by  the 
addition  of  water.  The  taste  of  nitroglycerine  is  sweet,  but  at  the  same  time  burning 
and  aromatic ;  it  is  a  violent  poison  even  in  small  doses,  and  its  vapour  is  of  course  equally 
virulent,  hence  great  care  is  required  in  working  with  this  substance  in  localities  where, 
as  in  mines  and  pits,  the  supply  of  fresh  air  is  limited.  Instead  of  manufacturing 


SECT,  in.]  EXPLOSIVES.  395 

nitroglycerine  in  works  specially  arranged  for  that  purpose,  and  transporting  this 
dangerous  compound,  it  is  better,  as  advised  by  and  executed  under  the  direction  of 
Dr.  E.  Kopp,  at  the  Saverne  quarries,  to  have  the  quantity  required  for  daily  use 
prepared  on  the  spot  by  intelligent  workmen.  Notwithstanding  the  very  serious 
accidents  which  have  been  caused  by  the  explosions  of  nitroglycerine  in  this  country 
as  well  as  abroad,  and  the  consequent  prohibition  of  its  use,  there  is  no  reason  why  this 
powerful  agent  should  not  be  employed  according  to  Kopp's  suggestion.  Instead  of  the 
acid  mixture  used  in  the  preparation  of  nitroglycerine,  M.  Nobel  suggests  the  follow- 
ing:— In  3^  parts  of  strong  sulphuric  acid  of  1-83  sp.  gr.  is  dissolved  i  part  of 
saltpetre,  and  the  fluid  cooled  down ;  the  result  is  the  separation  of  a  salt  consisting 
of  one  molecule  of  potassa,  4  molecules  of  sulphuric  acid,  and  6  molecules  of  water, 
and  which  at  32°  F.  is  altogether  eliminated  from  the  fluid,  leaving  an  acid  which,  by 
the  gradual  addition  of  glycerine,  is  converted  into  glonoine,  afterwards  separated  by 
water,  as  already  described. 

Nobefs  Dynamite. — Under  the  name  of  dynamite,  Nobel,  in  1867,  brought  out  a  new 
explosive  compound,  consisting  of  75  parts  of  nitroglycerine  absorbed  by  25  parts  of  any 
porous  inert  matter,  as  finely  divided  charcoal,  silica.  As  evidenced  by  the  experiments 
of  Bolley  and  Kuiidt,  dynamite  has  the  advantage  over  nitroglycerine  of  not  being 
exploded  even  by  the  most  violent  percussion,  therefore  requiring  a  peculiarly  arranged 
cartridge.  The  explosion  is  attended  with  such  force  that  large  blocks  of  ice  are  shat- 
tered to  atoms.  Dynamite  burns  off  quietly  in  open  air,  or  even  when  loosely  packed, 
the  combustion  being  accompanied  by  an  evolution  of  some  nitrous  acid ;  but  when 
dynamite  is  exploded  there  are  generated  only  carbonic  acid,  nitrogen,  and  aqueous 
vapour,  no  smoke  being  formed,  and  only  a  white  ash  left.  Dynamite  is  not  affected 
by  damp,  and  undoubtedly  offers  great  advantages  as  regards  its  use  in  mining, 
quarrying,  and  similar  operations,  for  although  the  price  exceeds  four  times  that  of 
powder  dynamite  performs  eight  times  as  much  work  with  less  danger  and  less  labour 
in  boring  blast  holes.  The  dynamite  is  placed  in  cartridges  of  thick  paper,  and 
ignited  by  means  of  a  fusee,  which  passes  through  the  sand  serving  the  purpose  of  a 
wad.  Dynamite  can  be  transported  without  danger  of  explosion.  Dittmar's  dualine  is 
a  mixture  of  nitroglycerine  with  sawdust  or  wood-pulp  as  used  in  paper  mills,  both 
previously  treated  with  nitric  and  sulphuric  acids. 

The  annual  production  of  dynamite  in  Europe  is  now  7000  tons. 

Lithofracteur,  Dualine,  Colonia-powder,  Fulminatine,  Sebastine,  Serranine,  Atlas 
powder,  Yulcan  powder,  Neptune  powder,  and  Forcite  are  all  mixtures  containing  nitro- 
glycerine. 

The  gelatine  dynamites,  which  are  obtained  by  dissolving  7  to  8  per  cent,  of 
collodion  cotton  in  nitroglycerine,  form  a  solid  gelatinous  mass,  blasting  gelatine.  It 
combines  the  shattering  power  of  nitroglycerine  with  a  more  or  less  decided  propelling 
action,  and  will  doubtless  before  long  supersede  dynamite.* 

Gun-Cotton. — If  cotton  is  treated  with  a  mixture  of  nitric  acid  and  sulphuric 
acid  there  is  formed,  according  to  the  proportions  and  the  conditions  of  action,  either 
gun-cotton  or  collodion-cotton,  bodies  which  differ  considerably  in  their  properties. 

Gun-cotton  (pyroxiline,  fulmicoton)  was  simultaneously  discovered  by  SchOnbein 
and  Bottger.  The  raw  material  is  cotton,  generally  the  waste  of  spun  cotton  freed 
from  all  impurities,  mechanical  and  chemical.  After  being  thoroughly  torn  up  and 
loosened  by  machinery  and  dried,  it  is  ready  for  nitrising. 

For  this  purpose  there  are  used  i  part   nitric  acid  at  1*516  sp.  gr.  and  3  parts 

*  The  employment  of  nitroglycerine  and  its  mixtures  for  criminal  purposes  is  a  fatal  objection 
to  Kopp's  suggestion.  These  substances  should  be  manufactured  only  in  works  carefully  con- 
structed and  guarded,  and  should  be  supplied  only  to  responsible  persons. 


396  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

sulphuric  acid  at  1*842  sp.  gr. ;  the  acids  are  poured  into  a  large  cylindrical  vessel 
of  cast-iron,  in  which  revolves  an  iron  shaft  fitted  with  arms  driven  by  conical 
wheels.  After  the  acids  are  mixed  they  are  let  off  into  cast-iron  vessels,  which 
stand  lower,  and  are  closed  with  covers.  Each  vessel  has  a  conical  bottom  with 
a  cock  for  letting  off,  from  which  a  branch  leads  to  a  common  cast-iron  main  leading 
to  the  nitrising  room.  Here  there  are  thick  brick  walls  in  which  there  is  a  special 
cavity  for  each  vessel  (at  Waltham  Abbey  a  long  open  channel),  in  which  cold  water  is 
constantly  flowing.  In  these  cavities  there  are  placed  quadrangular  cast-iron  nitrising 
vessels,  which  have  a  grate  at  their  back  part.  The  quantity  of  acid  used  is  always 
twenty  times  greater  than  is  necessary — about  20  kilos.  Into  each  there  is  put  a 
small  quantity  of  cotton,  about  ^  kilo. ;  it  is  stirred  about  with  an  iron  fork,  and  when 
nitrised  it  is  hard  on  the  grating.  As  the  cotton,  in  spite  of  being  pressed,  has  either 
consumed  or  absorbed  eleven  times  its  weight  of  acid,  about  an  equal  quantity  of  fresh 
acid  is  added  to  the  vessel.  After  twenty  charges  the  entire  acid  mixture  will  thus 
have  been  renewed.  The  cotton  requires  a  very  careful  treatment,  so  as  not  to  obtain 
portions  which  have  entirely  or  partially  escaped  the  action  of  the  acid.  For  this 
purpose  the  nitrised  cotton  is  placed  in  small  stoneware  pots,  set  in  a  cistern  constantly 
traversed  by  cold  water.  Here  it  remains  for  some  time  to  cool. 

At  Waltham  Abbey  the  nitrised  cotton  is  whizzed.  It  is  then  placed  in  a  large 
tank  of  water  with  a  dash-wheel,  and  is  whizzed  again.  It  is  then  transferred  to  other 
washing  tanks,  each  time  with  fresh  water  gently  heated  by  steam  pipes,  to  which  soda 
and  elutriated  chalk  are  sometimes  added  to  remove  the  last  traces  of  acid.  The 
cotton  is  next  transferred  to  a  hollander,  as  they  are  used  in  paper-mills,  where  it  is 
converted  into  a  uniform  paste  amidst  continual  washing.  Every  four  hours  the  water 
is  run  off  and  fresh  water  is  run  on.  After  from  twenty-four  to  thirty-six  hours  01 
upwards  of  such  washing  a  sample  of  the  lot  (potcher)  is  tested  for  its  explosion  point. 
If  satisfactory,  it  is  once  more  whizzed  and  stored  for  use. 

Properties  of  Gun-cotton. — In  its  outward  appearance  gun-cotton  does  not  differ 
from  ordinary  cotton,  neither  is  any  difference  perceptible  by  microscopic  investigation. 
It  is  insoluble  in  water,  alcohol,  and  acetic  acid,  difficultly  soluble  in  pure  ether,  but 
readily  soluble  in  ether  which  contains  alcohol,  and  in  acetic  ether.  Gun-cotton  is 
liable  to  spontaneous  decomposition,  which  may  even  induce  its  spontaneous  com- 
bustion j  this  decomposition  is  attended  with  the  evolution  of  aqueous  vapour  and  of 
nitrous  acid  fumes,  the  remaining  substance  containing  formic  acid.  As  regards  the 
temperature  at  which  gun-cotton  ignites  statements  differ ;  it  has  in  some  instances 
been  dried  at  90°  to  100°  without  any  dangerous  consequences,  while  it  has  been 
found  to  ignite  at  43°.  Instances  are  on  record  of  serious  explosions  of  gun-cotton 
having  taken  place  under  conditions  which  leave  no  doubt  that  the  greatest  care  is 
required  in  handling  and  warehousing  this  substance ;  for  instance,  a  small  magazine, 
filled  with  gun-cotton,  situated  in  the  Bois  de  Vincennes,  Paris,  was  exploded  by  the 
sun's  rays ;  and  at  Faversham  the  Le  Bouchet  drying  rooms,  which  could  not  possibly 
be  heated  above  45°  to  50°,  exploded  with  great  violence.*  Gun-cotton  explodes  by 
percussion,  leaving  no  residue  after  its  ignition.  Good  gun-cotton  may  be  burned  oft 

*  The  extraordinary  statements  just  given  are  to  be  explained  by  the  presence  of  impurities.  If 
the  least  trace  of  acid  remains  the  gun-cotton  will  sooner  or  later  explode  spontaneously,  even  at 
common  temperatures.  Or  if  fatty  matter  or  other  impurities  are  left  adhering  to  the  fibre,  bye- 
products  are  formed  which  lead  to  decomposition.  The  behaviour  of  gun-cotton  when  heated 
depends  on  the  gradual  or  sudden  rise  of  temperature.  In  the  former  case  the  gun-cotton  ignites 
at  a  lower  point.  Cold  gun-cotton  burns  harmlessly  if  a  light  is  applied  to  it,  but  if  it  has  been 
gradually  heated  it  explodes  as  if  it  had  been  fired  by  a  detonator.  The  fearful  explosion  at 
Stowmarket  in  1871  was  traced  to  the  malicious  addition  of  acid  to  some  of  the  finished  and  dried 
•discs  in  the  magazine. 


SECT.  HI.] 


EXPLOSIVES. 


397 


Fig.  342. 


when  placed  on  dry  gunpowder  without  igniting  the  latter.     It  is  very  hygroscopic,  but 
may  be  kept  for  a  length  of  time  under  water  without  affecting  its  explosive  properties. 

Gun-cotton  is  generally  regarded  as  trinitro-cellulose,  C6H7(N02)3O5,  but  according 
to  Eder  it  is  cellulose  hexanitrate,  C13H14O4(N03)6 ;  collodion  cotton  is  mainly  the 
tetranitro-cellulose,  C12H16O6(NO3)4. 

The  apparatus  of  Hess  for  determining  the  chemical  stability  of  explosives,  especially 
gun-cotton  and  nitroglycerine,  is  shown  in  Fig.  342.  The  samples,  p,  of  the  explosives 
are  placed  in  vessels  of  badly  conductive  mate- 
rials in  a  heating  chest,  W,  with  double  sides, 
the  intermediate  space  being  filled  with  water. 
In  the  samples  is  placed  a  thermometer,  t,  which 
passes  through  the  chest.  The  temperature  of 
the  heating-room,  which  can  be  kept  at  a  suit- 
able point  by  the  burner,  S,  can  be  read  off  on 
the  thermometer,  t ;  the  thermo-regulator,  R, 
serves  to  keep  the  internal  temperature  at  70°. 
The  overstepping  of  the  temperature  of  t  in 
the  explosives,  if  found  by  regular  observation, 
is  the  consequence  of  a  decomposition,  the  pro- 
gress of  which  is  to  be  regularly  followed. 
Samples  of  100  grammes  will  suffice.  In  order 
to  make  the  observation  without  danger  it  may 
be  watched  from  a  distance  by  means  of  a  tele- 
scope. The  samples,  as  is,  shown  in  the  middle 
vessel,  p,  may  be  placed  in  a  perforated  capsule 
provided  with  a  cover,  and  suspended  by  a 

flange.     It  can  be  raised  or  lowered  into  cold  water  by  means  of  a  cord,  S,  passing 
over  pulleys. 

The  examination  of  gun-cotton  is  effected  by  Alberts  as  follows  :  the  samples  are 
dried  for  two  hours  at  40°,  then  rubbed  through  a  fine  sieve  of  brass  wire.  An 
average  sample  of  10  grammes  is  then  taken  and  dried  in  the  exsiccator  until  its 
weight  is  constant.  The  requisite  quantity  of  gun-cotton  (about  0*48  gramme),  is 
weighed  into  a  small  flask,  provided  with  a  glass  stopper,  and  holding  about  10  c.c. 
After  the  nitrometer  (holding  140  c.c.)  is  prepared  as  usual,  about  5  c.c.  pure  con- 
centrated sulphuric  acid  is  poured  into  the  flask,  the  gun-cotton  is  stirred  up  in  it  with 
a  platinum  wire,  the  contents  of  the  flask  are  emptied  as  completely  as  possible  into 
the  funnel  of  the  nitrometer,  and  without  loss  of  time  it  is  drawn  into  the  measuring 
tube  by  turning  the  three-way  cock.  By  repeatedly  rinsing  out  the  flask,  each  time  with 
3  c.c.  of  concentrated  sulphuric  acid,  always  stirring  with  the  platinum  wire,  all  the 
rest  of  the  substance  is  brought  into  the  funnel  and  thence  into  the  measuring-tube. 
Lastly,  the  funnel  and  the  wire  are  rinsed  with  sulphuric  acid  which  is  also  conveyed 
into  the  measuring-tube.  The  three-way  cock  is  closed  and  the  work  is  complete  as 
usual  by  shaking.* 

*  The  ordinary  way  to  analyse  samples  of  gun-cotton  is  to  dry  a  quantity  until  the  weight  is 
constant,  and  then  to  weigh  100  grains  into  a  small  light  flask  closed  with  a  stopper,  or  into  a 
roomy  test-tube  with  a  well-fitting  cork,  an  excess  of  a  mixture  of  18  parts  anhydrous  ether  and 
3  parts  anhydrous  alcohol  is  poured  upon  the  gun-cotton,  the  stopper  is  inserted  and  the  flask  is 
let  stand  for  15  minutes,  with  occasional  shaking.  The  liquid  is  then  poured  off  and  the  sample 
rinsed  with  a  little  more  of  the  same  mixture.  The  residue  of  gun-cotton  is  allowed  to  evaporate 
under  the  air-pump.  If  any  loss  of  weight  is  formed  the  deficiency  is  due  to  a  lower  compound  of 
cellulose,  which  has  been  dissolved  out.  The  remaining  quantity  is  again  treated  in  the  same 
manner  with  acetic  ether,  which  dissolves  the  true  gun-cotton.  If  any  matter  remains  undissolved 
it  is  cotton  fibre  which  has  escaped  the  action  of  the  acids. 


398  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

Gun-cotton  has  been  used  with  success  for  filtering  strong  acids,  &c.,  and  if  steeped 
in  potassium  permanganate  as  an  application  to  wounds  which  have  become  offensive. 

Collodion  Cotton. — Maynard  used  the  solution  of  gun-cotton  in  alcohol  and  ether  as 
an  adhesive,  and  gave  it  the  name  of  collodion.  If  it  is  poured  in  a  thin  film  upon  the 
skin  there  is  formed  on  the  evaporation  of  the  ether  an  impervious  and  adherent  layer. 
It  is  used  in  surgery  instead  of  court-plaster  for  closing  up  incised  wounds,  and  for  the 
production  of  photographs  on  glass  (so-called  collodion  process).  Legray  produces  by 
the  following  process  a  collodion  cotton  perfectly  soluble  in  ether :  80  grammes  of 
dried  and  pulverised  potassium  nitrate  are  mixed  with  120  grammes  of  concentrated 
sulphuric  acid,  and  4  grammes  of  cotton  are  thoroughly  immersed  by  the  aid  of  a 
glass  rod  or  porcelain  spatula  in  the  pulpy  acid  mass,  which  is  stirred  about  for  a  few 
minutes ;  next  the  vessel  containing  acid  and  cotton  is  placed  in  a  large  quantity  of 
water,  and  the  converted  cotton  washed  until  all  the  acid  is  eliminated,  when  it  is 
dried.  Soluble  cotton  may  be  made  with  sodium  nitrate,  1 7  parts ;  sulphuric  acid, 
sp.  gr.  =  i-8o,  33  parts;  cotton,  ^  part.  -The  converted  cotton  is  soluble  in  acetic 
ether,  acetate  of  methyl  oxide,  wood-spirit,  and  aceton ;  the  usual  solvent  is  a 
mixture  of  18  parts  of  ether  and  3  parts  of  alcohol. 

Collodion  cotton  has  recently  been  used  in  the  manufacture  of  celluloid,  a  substance 
which  is  not  explosive,  but  highly  inflammable. 

Fulminating  Mercury. — The  compound  known  as  fulminating  mercury  is  a  com- 
bination of  f  ulminic  acid,  an  acid  unknown  in  a  free  state,  and  of  oxide  of  mercury ;  its 
formula  may  be  written  C2Hg2N2O2.  In  100  parts  it  consists  of  77*06  of  peroxide  of 
mercury  and  23-94  of  fulminic  acid.  According  to  the  late  Dr.  Gerhardt's  view,  this 
body  is  a  nitre-compound  which  may  be  regarded  as  cyan-methyl,  the  hydrogen  of  the 
methyl  of  which  has  been  replaced  by  hyponitric  acid  and  mercury ;  the  formula  is  then  : 

CJ  -v^M2  tCN.    This  substance  was  first  discovered  by  Mr.  Howard,  and  was  known,  until 

Liebig  gave  the  clue  to  its  nature,  as  Howard's  detonating  powder.  It  is  prepared 
on  a  large  scale  in  the  following  manner :  First,  2  Ibs.  of  mercury  arc  dissolved, 
by  the  aid  of  a  gentle  heat,  in  10  Ibs.  nitric  acid  (<sp.  gr.  1*33),  and  10  Ibs.  more 
of  nitric  acid  are  then  added.  The  resulting  fluid  is  poured  into  six  tubulated 
retorts,  and  to  the  contents  of  each  retort  is  added  10  litres  of  alcohol  (sp.  gr.  0-833). 
If  the  ingredients  are  mixed  by  measure  instead  of  weight,  for  every  volume  of  mercury 
there  is  taken  7^  volumes  of  nitric  acid,  and  10  volumes  of  alcohol.  After  a  few 
minutes  a  strong  evolution  of  gas  takes  place,  and  at  the  same  .time  a  white  precipitate, 
the  fulminate  of  mercury,  is  formed.  The  retorts  are  fitted  with  tubulated  receivers, 
from  which  glass  tubes  carry  off  the  very  poisonous  gas  and  fumes,  either  to  a  flue  or 
directly  to  the  outside  of  the  shed  in  which  the  operation  is  performed.  The  pre- 
cipitate is  collected  on  filters,  and  washed  with  cold  water  to  eliminate  the  free  acid. 
The  fulminate  is  next  dried,  filtered,  and  all  being  placed  on  plates  of  copper  or  earthen- 
ware, heated  by  steam  to  less  than  100°.  100  parts  of  mercury  yield  in  practice  from 
118  to  128  parts  of  fulminate,  while,  according  to  theory,  142  should  be  obtained. 
The  dried  fulminate  is,  with  cautious  manipulation,  divided  into  small  portions,  kept 
separately  in  a  paper  bag.  The  fulminate  thus  prepared  is  a  crystalline  white-coloured 
substance,  which,  by  being  heated  to  1 86°,  or  by  a  smart  blow,  explodes  with  a  loud 
report.  When  placed  on  iron  and  struck  with  an  iron  instrument,  the  detonation  is 
much  increased.  This  substance  also  explodes  by  contact  with  concentrated  sulphuric 
acid.  When  mixed  with  30  per  cent,  of  its  weight  of  water,  the  crystalline  fulminate 
may  be  rubbed  to  powder  with  a  wooden  pestle  on  a  marble  slab.  The  manufacture 
of  this  substance  on  a  large  scale  requires  peculiar  arrangements,  into  the  particulars 
of  which  we  cannot  here  enter. 

Percussion-Caps. — The  fulminate  of  mercury  is  chiefly  used  for  filling  percussion- 


SECT.   III.] 


AMMONIA. 


399 


caps.  For  this  purpose  100  parts  of  the  fulminate  are  rubbed  to  powder  with  30  parts 
of  water,  50  to  62*5  parts  of  saltpetre,  and  29  of  sulphur.  This  mixture  is  dried 
sufficiently  to  admit  of  being  granulated,  after  which  it  is  forced,  by  means  of  machinery, 
into  the  copper  caps,  and  simultaneously  covered  with  either  a  layer  of  varnish  or  tin- 
foil, to  protect  it  from  damp.  Tin-foil  being  more  expensive  is  not  used  for  military 
gun-caps.  The  best  varnish  for  the  purpose  is  a  solution  of  mastic  in  oil  of  turpentine. 
The  caps  are  finally  dried  by  a  gentle  heat,  and  packed  in  boxes.  One  kilogramme  of 
mercury  converted  into  fulminate  suffices  for  the  filling  of  40,000  gun-caps  of  the 
larger  or  military  size,  and  for  57,600  caps  of  the  size  used  by  sportsmen. 

AMMONIA. 

The  ammonia  and  the  ammoniacal  salts  employed  in  the  arts  are  chiefly  obtained 
by  the  dry  distillation  of  coal.  Comparatively  small  quantities  are  obtained  as  bye- 
products  in  the  manufactures  of  animal  charcoal  and  of  the  f errocyanides ;  also  from 
stale  urine,  faecal  waters,  from  beet-treacle,  and  from  the  action  of  superheated  steam 
upon  certain  cyanides. 

Ammonia,  NH3,  consists  of  i  volume  of  nitrogen  and  3  volumes  of  hydrogen,  con- 
densing to  2  volumes  of  ammonia  gas,  a  colourless  gas  of  a  peculiar  and  well-known 
odour  and  sharp  biting  taste.  At  15°  water  absorbs  727,  and  at  o°  1050,  times  its 
own  bulk  of  this  gas,  the  solution  being  known  as  liquid  ammonia,  or  spirit  of  sal- 
ammoniac,  the  sp.  gr.  of  which  is  0-824  (  =  31-3  per  cent.  NH3).  Usually,  however,  a 
weaker  and  more  stable  liquid  ammonia  is  prepared  for  pharmaceutical  and  technical 
purposes,  having  a  sp.  gr.  =  0-960  (=  9-75  per  cent.  NH3).  The  following  table 
shows  the  specific  gravity  of  liquid  ammonia,  and  the  percentage  of  ammonia  con- 
tained : — 


Specific 

Per 

Specific 

Per 

Specific 

Per 

Specific 

Per 

Specific 

Per 

Specific 

Per 

gravity 

cent. 

gravity 

cent. 

gravity 

cent. 

gravity 

cent. 

gravity 

cent. 

gravity 

cent. 

at  14°. 

NH3. 

at  14°. 

NH3. 

at  14°. 

NHS. 

at  14°. 

NH3. 

at  14°. 

NHS. 

at  14°. 

NHS. 

0-8844 

36-0 

0-8976 

30-0 

0-9133 

24-0 

0-9314 

l8'0 

0-9520 

12  "O 

0-9749 

6-0 

0-8864 

35  '0 

o  9001 

29-0 

0-9162 

23-0 

0-9347 

17-0 

0-9556 

II'O 

0-9790 

.S'O 

0-8885 

34  'o 

0-9026 

28-0 

0-9191 

22  -O 

0-9380 

16-0 

0-9593 

IO'O 

0-9831 

4-0 

0-8907 

33  Po 

0-9052 

27-0 

0-9221 

21  -O 

0-9414 

15-0 

0-9631 

9'0 

0-9873 

3-0 

0-8929 

32-0 

0-9078 

26*0 

0*9251 

2O  "O 

0-9449 

14-0 

0-9670 

8-0 

0-9915 

2'O 

0-8953 

31-0 

0-9106 

25-0 

0-9283 

ig-O 

0-9484 

13-0 

0-9709 

7-0 

0-9959 

I'D 

Ammoniacal  gas  is  abundantly  soluble  in  alcohol.  It  has  numerous  technical 
applications,  e.g.,  in  extracting  the  colouring  matters  of  orchilla-weeds,  in  the  produc- 
tion of  ammoniacal  cochineal,  as  an  addition  in  the  manufacture  of  snuff,  in  purifying 
coal-gas  from  carbonic  acid  and  carbon  disulphide,  in  saponifying  fats  and  oik,  in  the 
manufacture  of  ferrocyanides  along  with  carbon  disulphide,  for  dissolving  silver  (silver 
chloride)  from  its  ores,  in  bleach-works,  in  the  manufacture  of  lakes  and  colours,  and  in 
the  production  of  indigo. 

In  Java  (at  the  suggestion  of  Sasser)  ammonia  has  been  added  to  the  fermenting 
mass  of  indigo  and  the  colour  is  thus  rendered  purer. 

The  uses  of  ammonia  in  the  ammonia-soda  process  and  in  the  artificial  production 
of  ice  are  of  great  importance. 

Preparation  of  Liquid  Ammonia. — By  decomposing  with  caustic  lime  either  ammo- 
nium chloride  or  sulphate,  ammoniacal  gas  is  set  free,  and  can  be  absorbed  by  water, 
care  being  taken  that  the  lime  is  in  excess.  When  ammonium  carbonate  is  prepared 
on  the  large  scale  by  the  sublimation  of  a  mixture  of  chalk  and  sal-ammoniac,  a 
large  quantity  of  ammoniacal  gas,  14  parts  for  each  100  parts  of  ammonium  car- 
bonate, is  obtained  and  may  be  utilised.  Wagner  has  been  the  first  to  observe  that 
the  technical  preparation  of  liquid  ammonia  might  be  combined  with  the  preparation 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


of  baryta-white  by  precipitating  a  solution  of  ammonium  sulphate  with  caustic  baryta 
water ;  the  clear  supernatant  liquor  will  be  a  solution  of  caustic  ammonia. 

According  to  Isambert,  the  reaction  taking  place  during  the  production  of  ammonia, 
CaO  +  2NH4C1  =  CaCl2  +  2NH3  +  H20,  involves  a  consumption  of  10,900  calories.  At 
common  temperatures,  even  in  a  vacuum,  the  ammonia  escapes  from  the  mixture  because 
there  is  formed  the  molecular  compound  CaCl2.2NH3,  which  gives  off  ammonia  only  at 
1 80°  to  200°.  Baryta  and  strontia  drive  off  ammonia  from  ammonium  chloride  at 
1 80°  to  200°,  whilst  it  is  liberated  by  litharge  at  common  temperatures. 

Inorganic  Sources  of  Ammonia. — i.  Native  ammonium  carbonate,  met  with  in  large 
quantities  in  the  guano  deposits  of  South  America,  was  imported  into  Germany  as  a 
commercial  article  in  1848.  On  being  analysed  this  substance  was  found  to  consist  of 
— Ammonia,  20*44;  carbonic  acid,  54*35;  water,  21*54;  and  insoluble  matter,  21*54 
parts.  It  is,  therefore,  an  ammonium  bicarbonate,  (NH4)HCO3. 

2.  The  preparation  in  Tuscany  of  native  ammonium  sulphate  as  a  bye-product  of 


Fig-  343- 


the  preparation  of  boracic  acid  has  recently  become  important.  The  suffioni  contain, 
in  addition  to  boracic  acid,  potassium,  sodium,  ammonium,  rubidium,  &c.,  sulphates ; 
and  that  the  quantity  of  these  substances  is  by  no  means  small  may  be  inferred  from 
Travale's  researches,  from  which  it  appears  that  four  suffioni  yielded  within  twenty- 
four  hours  5000  kilos,  of  saline  matter,  consisting  of  150  kilos,  of  boracic  acid,  1500 
kilos,  of  ammonium  sulphate,  1750  kilos,  of  magnesium  sulphate,  750  kilos,  of  the 
ferrous  and  manganous  sulphates,  &c.  The  ammonia  is  probably  due  to  the  decom- 
position of  nitrogenous  organic  matter,  occurring  largely  in  the  Tuscan  mountains,  the 
soil  near  the  lagoons  being  impregnated  with  ammonium  sulphate.  In  combination 
with  the  sodium,  magnesium,  and  iron  sulphates,  ammonium  sulphate  forms  the 
mineral  Boussingaultite,  discovered  by  Bechi. 

3.  The  ammoniacal  salts  due  to  volcanic  action  are  of  little  or  no  value  to  industry. 
Mascagnin,  ammonium  sulphate,  is  met  with  on  Vesuvius  and  Etna;  sal-ammoniac  is 


SECT,  in.]  AMMONIA.  40I 

sometimes  also  found  on  Etna,  as  in  the  years  1635  and  1669,  in  such  large  quantities 
as  to  become  temporarily  an  article  of  commerce  at  Catania  and  Messina. 

Attempts  to  convert  atmospheric  nitrogen  into  ammonia  have  led  hitherto  to  no 
practical  results, 

Organic  Sources  of  Ammonia. — Industrially  speaking,  the  organic  sources  of 
ammonia  are  far  more  important  than  the  inorganic.  Coal  takes  here  the  first  place. 
In  the  production  of  coal-gas  and  of  coke,  it  yields  up  its  nitrogen  as  ammonia,  which 
is  obtained  as  gas  liquor. 

The  ammonia  of  the  gas-water  may  be  utilised  in  various  ways.  Where  fuel  is 
cheap,  and  crude  ammonium  sulphate  or  crude  sal-ammoniac  a  marketable  article,  the 
gas-water  may  be  at  once  neutralised  by  an  acid,  and  the  liquid  thus  obtained  evapo- 
rated. This  is  done  in  a  sal-ammoniac  factory  at  Liverpool,  where,  during  the  colder 
season  of  the  year,  300  cwts.  weekly  of  this  salt  are  prepared.  Generally,  however, 
the  gas-water  is  submitted  to  a  process  of  distillation,  and  the  ammonia  evolved 
converted  into  sulphate,  as  in  Mallet's  apparatus,  or  into  sal-ammoniac,  as  in  Rose's 
apparatus. 

Mallet's  Apparatus, — This  apparatus,  in  use  in  many  of  the  large  gas-works,  is 
shown  in  vertical  section  in  Fig.  343.  The  plan  of  action  is  to  force  steam  into  large 
vessels  filled  with  gas-water,  the  effect  being  the  volatilisation  of  the  ammonium 
carbonate.  Sometimes  lime  is  added.  The  volatilised  ammonia — of  course  if  lime  is 
added  caustic  ammonia  is  evolved — is  next  conveyed  into  an  acid  liquor,  and  thus  con- 
verted into  ammonium  sulphate.  The  apparatus  consists  of  two  cylindrical  boiler- 
plate vessels,  A  and  E.  A  is  heated  directly  by  the  fire,  and  is  provided  with  a  leaden 
tube,  c,  dipping  into  the  liquid  contained  in  £,  this  vessel  being  placed  to  catch  the 
waste  heat  from  the  fire,  b  and  e  are  man-holes ;  a  and  a1  stirrers.  By  means  of 
the  tube,  d,  the  fluid  from  B  can  be  run  off  into  A .  Gas-water  is  poured  into  both 
vessels  and  lime  added ;  ammonia  is  set  free,  while  calcium  carbonate  and  sulphide 
are  formed,  and  of  course  remain  in  the  vessels  after  the  volatilisation  of  the  ammonia. 
The  vessel,  B,  is  also  filled  with  ammoniacal  water,  and  when  the  operation  is  in  pro- 
gress this  water,  already  warmed,  is  run  by  the  aid  of  the  tube,  h,  from  D  into  B.  E  is 
a  gas-water  tank,  from  which  B  is  filled  by  means  of  g.  The  ammonia  set  free  in  A  is, 
with  the  steam,  conveyed  by  the  pipe,  c,  into  B,  thence  through  c',  into  the  wash- vessel, 
O,  and  thence  again  through  c",  into  the  first  condenser,  D.  The  partially  condensed 
vapour  now  passes  into  the  condensing  vessel,  F,  the  worm  of  which  is  surrounded  by 
cold  water.  The  dilute  ammonia  is  collected  in  G,  and  forced  by  means  of  the  pump, 
R,  into  (7,  whence  it  is  occasionally  syphoned  into  either  A  or  B.  The  non-condensed 
ammoniacal  gas  is  carried  from  G,  through  a  series  of  Woulfe's  bottles,  the  first  bottle, 
H,  containing  olive  oil  for  the  purpose  of  absorbing  any  hydrocarbons  mixed  with  the 
gas ;  the  bottle,  J,  contains  caustic  soda  lye,  in  order  to  purify  the  ammonia  and  retain 
impurities  ;  the  bottle,  K,  is  half -filled  with  distilled  water.  The  ammoniacal  gas  having 
passed  through  K,  is  conveyed  to  the  large  lead -lined  wooden  tank,  Z,  filled  with  dilute 
sulphuric  acid  if  it  is  intended  to  prepare  ammonium  sulphate,  or  with  water  for  making 
liquid  ammonia.  The  vessel,  Z,  is  placed  in  a  tank  of  water ;  i  is  a  small  pipe  for  intro- 
ducing acid  ;  while  the  tube  leading  to  M  serves  to  carry  off  any  unabsorbed  ammonia, 
M  being  also  filled  with  acid. 

Lungds  Apparatus. — This  apparatus,  also  intended  for  the  utilisation  of  gas-water, 
is  shown  in  Fig.  344 ;  a,  is  the  boiler ;  h  the  gas  tube  connected  with  the  worm,  c, 
which  is  placed  in  a  tank,  d,  filled  with  gas  liquor,  run  into  a  by  means  of  the  tube,  e. 
The  tube,  /,  is  so  fitted  to  a  as  to  admit  of  discharging  the  waste  liquor  readily,  b  re- 
presents a  stirrer  fitted  to  the  boiler  by  a  stuffing  box,  and  being  intended  to  rake  up 
the  lime  and  prevent  it  getting  caked  to  the  bottom  of  a  /  hv  a  tube  intended  for  run- 
ning gas-liquor  into  d,  from  a  tank  placed  at  a  higher  level ;  i,  a  tube  provided  with  a 

2  C 


402  CHEMICAL   TECHNOLOGY.  [SECT,  m 

tap  and  fitted  to  the  cover  of  d,  to  convey  any  gas  or  vapours  from  d  into  the  worm. 
k  represents  a  wash  vessel,  sometimes  filled  simply  with  water,  at  others  with  milk 
of  lime.  The  gas  and  vapours  having  passed  through  k,  are  conveyed  to  the  absorp- 
tion vessel,  I.  The  tube,  m,  through  which  the  gas  passes,  is  funnel-shaped,  and  oppo- 
site to  the  mouth  of  the  funnel,  at  the  bottom  of  the  tank,  a  thick  disc  of  lead  is  fixed 
because  at  this  spot  the  action  of  the  gas  would  soon  wear  away  the  leaden  lining 

Fig.  344- 


of  the  vessel.  o  is  a  smaller  wooden  tank,  also  lead-lined,  into  which  sulphuric 
acid  is  poured,  and  whence  it  runs  into  I  through  the  stoneware  syphon,  p.  Any 
vapours  given  off  are  caught  by  the  hood,  r,  and  thence  conveyed  by  a  tube  into  the 
chimney.  The  saline  matter  deposited  in  I  is  removed  by  a  leaden  pail,  as  shown 
in  the  cut ;  when  this  pail  is  filled  it  is  drawn  up  by  means  of  the  chain  and  pulley 
aided  by  the  counter-weight,  t.  The  salt  (ammonium  sulphate)  is  placed  in  the 
basket,  u,  from  which  the  mother -liquor  adhering  to  the  salt  drains  again  into  the 
tank,  I.  Evaporation  is  therefore  unnecessary  with  this  apparatus. 

According  to  Kunheim,  the  presence  of  ammonium  sulphide  is  especially,  trouble- 
some in  working  up  as  gliquors.  To  remove  it,  and  at  the  same  time  to  utilise  all 
the  sulphur,  a  powerful  but  greatly  subdivided  stream  of  common  air  is  allowed  to 
act  upon  the  cold  gas  liquor.  The  ammonium  sulphide  is  then  split  up  into  sul- 
phuretted hydrogen  and  ammonia.  The  former,  along  with  the  excess  of  air,"is  passed 
through  finely  divided  feirichy dioxide  and  thus  absorbed.  The  hydroxide  is  sus- 
pended in  a  dilute  solution  of  an  alkaline  earth.  • 

Among  the  recent;  apparatus  for  distillation  the  following  deserve  notice. 

The  apparatus  of  H.  Griineberg  consists  of  a  still,  A  (Fig.  345  and  346),  a  rectifier, 
B,  a  condensing  apparatus,  C,  connected  with  an  absorption  vessel,  Z>,  and  a  hydraulic 
joint,  E.  The  vertical  cylindrical  pan,  A,  has  an  internal  concentric  compartment,  a, 
which  passes  through  the  lower  part  of  the. pan  and  is  prolonged  below.  It  is  closed 
with  a  vaulted  bottom,  which  latter  has  an  exit  cock,  /,  serving  to  remove  the  im- 
purities of  the  lime  (introduced  through  the  pipe,  e,  into'  the  cylinder,  a),  as  well  as  to 
run  off  the  calcium  sulphate  formed.  In  the  compartment,  a,  the  tube,  b,  is  suspended 
concentrically  down  to  the  cylindrical  affix.  This  tube,  6,  is  closed  below  and  fitted 
with  small  outflow  tubes,  «,  but  above  it  is  connected  with  the  main  pan,  A,  by  means 
of  the  collar,  c,  with  its  series  of  perforations  at  d.  In  the  above-mentioned  cylindrical 


SECT.    III.] 


AMMONIA. 


appendage  there  is  a  small  stirring  apparatus,  s,  serving  to  keep  the  lime  introduced 
through  e  in  close  contact  with  the  liquid  descending  from  the  internal  tube,  b,  through 
the  tubes,  t,  and  freed  from  volatile  ammoniacal  compounds.  The  pan,  h,  has  an  exit 
pipe,  h,  hydraulically  cut  off  from  the  cylindrical  vessel,  i,  outside  the  apparatus.  It  has 
also  an  exit-cock,  g,  for  complete  emptying.  Upon  the  pan,  A,  there  is  fixed  a  rectifier 
of  ordinary  construction,  or  in  its  place  a  scrubber  filled  with  coke.  It  is  connected  with 
the  refrigerator,  C,  by  the  tube,  k.  The  refrigerator  is  fed  from  the  cistern,  R.  The 
pipe,  I,  serves  to  convey  away  the  water  which  has  been  warmed  in  C  to  the  rectifier. 

Fig.  345  and  346. 


The  crude  gas-liquor  flows  from  F  into  the  cooler,  C,  and  hence,  by  means  of  the 
tube,  I,  through  the  rectifier,  B,  into  the  descending  tube  of  the  still-pan,  A.  At  the 
bottom  of  the  piece,  a,  of  this  pan  it  meets,  whilst  flowing  down  through  the  pipes,  t, 
with  the  milk  of  lime  which  is  there  present.  It  is  there  decomposed,  a  reaction  which  is 
assisted  by  the  occasional  movement  of  the  agitator,  s.  The  liquid,  which  now 
contains  free  ammonia,  rises  up  in  the  cylinder,  a,  and  flows  over  at  its  upper  margin 
into  the  main  pan,  A.  From  this  it  is  carried  off  by  the  tube,  h,  at  the  bottom,  after 
the  ammonia  has  been  expelled.  The  vapours  evolved  in  A  pass  through  the  apertures, 
d,  into  the  rectifier,  and  from  here  either  into  the  cooler,  (7,  which  at  the  same 
time  separates  the  gases  and  the  vapours  from  each  other,  or,  if  it  is  desired  to  obtain 
ammonium  sulphate,  into  a  lead  vessel  full  of  sulphuric  acid.  In  the  former  case  the 


404 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


ammoniacal  liquor  condensed  in  C  flows  through  the  tube,  m,  into  the  vessel,  E  (cut 
off  by  a  hydraulic  joint),  and  flows  from  there  through  n;  the  tube,  o,  conveys  the 
nncondensed  vapours  into  the  cistern,  D,  lined  with  lead  and  filled  with  sulphuric 
acid,  and  from  there  the  gases  not  absorbed  are  conveyed  into  the  furnace  by  the 
tube,  p. 

Recently  the  column,  B  (Fig.  347),  has  been  connected  with  a  regulator.  R.  This 
is  an  ascending  pipe  enclosed  in  a  cooling  cylinder.  It  renders  it  possible  to  carry  off 
the  vapours  entering  the  cooling  worm,  Z),  as  concentrated  (as  rich  in  ammonia),  as  it 
may  be  desired  by  simply  regulating  the  temperature  of  the  refrigerating  cylinder, 
which  receives  a  constant  inflow  and  outflow  of  cooling  water.  The  more  plentiful  this 
flow  and  consequently  the  colder  the  cylinder,  R,  the  richer  are  the  ammoniacal  vapours 
issuing  from  the  tube,  k.  To  prevent  the  injurious 
cooling  of  the  lime  vessel  and  of  the  steam  pipes 
leading  to  it,  and  to  supply  it  with  more  heat, 
this  lime  vessel,  C,  is  connected  with  the  still-pan, 
A,  and  the  steam  pipes  are  carried  up  within  the 

Fig-  347- 


ing.  348. 


Fag.  349. 

spaces  A  and  G.  This  is  done  in  order  to  keep  these  parts  of  the  apparatus  as  hot  as 
possible,  and  thus  accelerate  the  operation  as  well  as  to  convey  hot  vapours  into  the 
acid,  and  thus  prevent  any  further  evaporation  of  the  saline  lye. 

H.  Griineberg  and  E.  Blum  further  recommend,  the  application  of  a  so-called 
stairs  column  for  gas  liquor.  The  liquid  enters  above  at  a  (Figs.  348  and  349),  into 
the  upper  column,  which  it  traverses  in  the  opposite  direction  to  the  ascending  vapours, 
so  that  the  ammonia  is  expelled.  From  the  lower  column,  b,  the  water  flows  through 
the  pipe,  c,  to  the  lime-vessel,  d,  where  the  combined  ammonia  is  set  free  by  the  action 
of  milk  of  lime.  The  liquid  thus  treated  passes  through  the  pipe,  e,  to  the  mud  bag,/, 
and  flows  over  upon  the  steps  of  the  column  to  the  outfall,  g.  Inversely  the  steam  serving 


SECT.    III.] 


AMMONIA. 


405 


350. 


in  the  distillation  enters  the  perforated  worm-tube,  underneath  the  stair  column,  ascends 
high  up  the  column,  being  guided  by  the  concentric  partitions,  */  passes  through  the 
pipe,  k,  into  I,  which  compel  the  steam  to  traverse  the  liquid  in  the  lime  pan,  and  then 
ascends  through  m  to  the  upper  column,  which  it  leaves  at  n,  in  admixture  with  the 
ammoniacal  vapours.  Thus,  the  expelled  water  which  contains  only  a  part  of  the 
ammonia  liberated  by  the  lime,  comes,  on  the  stair  column,  in  intimate  contact  with  the 
fresh  steam. 

The  apparatus  of  J.  Gareis,  designed  for  small  gasworks,  contains  the  liquid  to  be 
distilled  in  the  two  vessels,  A  and  C  (Fig.  350),  whilst  B  contains  also  an  addition  of 
milk  of  lime,  admitted  from  the  cistern,  D.  The  boiler,  A,  is  heated  by  direct  fire 
in  the  grate,  b,  and  the  smoke,  &c.,  escapes 
through  the  flue,  n,  into  the  chimney.  The 
gases  and  vapours  evolving  from  the  liquid 
in  A,  traverse  the  liquid  mixed  with  milk 
of  lime  in  B,  in  the  direction  of  the  arrows, 
heat  it  to  a  boil,  and  pass  them  in  the 
same  manner  through  the  fresh  gas  liquor 
in  the  cistern,  C,  finally  arriving  through 
h  in  the  condensers,  when  all  the  ammonia 
has  been  expelled  by  prolonged  boiling 
from  the  liquor  in  B  ;  this  pan  is  emptied 
by  opening  the  cock,  i,  and  after  closing 
it  again  the  cock,  k,  is  opened,  when  the 
liquid  in  brushes  from  below  into  A.  The 
liquid  here  rises  up,  flows  over  the  upper 
edge  of  A,  and  falls  into  B.  When  this 
has  received  the  requisite  quantity  of 
liquid  the  cock,  k,  is  closed,  and  by  opening 
the  cock,  I,  so  much  milk  of  lime  is  trans- 
ferred from  D  to  B  as  is  sufficient  for 
liberating  the  combined  ammonia.  The 
receiver,  (7,  is  then  again  filled  with  fresh 
gas  liquor  from  a  cistern  fixed  at  a  higher 
level.  C  is  advantageously  filled  slowly, 
say  in  four  hours  ;  to  this  end  the  gas 
liquor,  entering  at  £,  runs  slowly  through 

the  warmer,  V,  and  arrives  in  the  receiver,  C.  By  removing  the  cover,  o,  the  pan,  A, 
may  be  cleaned  out  as  required.  For  cleaning  B,  there  are  several  small  man-holes, 
p.  The  smallest  size  of  the  apparatus  works  up  i  cubic  metre  of  gas  liquor  in  twenty- 
four  hours,  and  uses  50  kilos,  of  waste  coke. 

Ammonia  from  Lant  or  Stale  Urine. — An  adult  man  produces  daily  on  an  average 
30  grammes  urea,  representing  a  yearly  yield  of  24*2  kilos,  ammonium  sulphate.  Lant, 
or  .stale  urine,  is  a  very  important  source  of  ammonia.  Whenever  nitrogenous  organic 
bodies  are  decaying,  ammonia  is  always  formed ;  when  the  organic  substance  is  a 
proteine  compound,  there  is  formed  ammonium  carbonate  as  well  as  sulphide ;  but 
when  the  organic  substance  contains  no  sulphur,  only  ammonium  carbonate  is  formed, 
as  is  the  case  with  the  urea,  CH4N2O,  contained  in  urine,  the  urea  by  taking  up  the 
elements  of  the  water  being  converted  into  ammonium  carbonate.  Lant  is  frequently 
employed  without  further  preparation  for  various  purposes,  on  account  of  the  ammo- 
nium carbonate  it  contains,  as,  for  instance,  in  washing  wool  and  removing  the  fat 
from  flannel  and  other  woollen  fabrics.* 

*  Practical  dyers  maintain  that  lant  leaves  the  wool  in  a  better  condition  for  dyeing  than  pure 
ammonia  or  soap,  and  gives  it  a  more  kindly  "  handle." 


406 


CHEMICAL  TECHNOLOGY. 


[SECT.  m. 


The  apparatus  exhibited  in  Fig.  351,  contrived  by  Figuera,  and  until  lately  in 
operation  at  a  large  establishment  for  the  utilisation  of  the  contents  of  the  latrines  and 
cloacae  of  Paris,  consists  of  a  steam-boiler,  W,  the  steam  generated  in  which  is  con- 
veyed to  two  large  iron  cylinders  filled  with  lant.  The  ammonium  carbonate  expelled 
is,  with  the  steam,  condensed  in  a  leaden  worm ;  the  cooled  liquid  is  conveyed  to  a 
tank  filled  with  acid,  and  thus  converted  into  ammonium  sulphate.  The  arrange- 
ment of  the  apparatus  is  as  follows  :— The  wooden  vessel,  A,  contains  some  250  hecto- 
litres of  lant.  and  is  filled  by  means  of  the  tube,  h.  C  and  (7  are  two  cylindrical  sheet- 
iron  vessels  of  100  hectolitres  capacity ;  P  and  P'  are  similar  vessels,  the  use  of  which 
will  be  presently  explained.  At  the  commencement  of  the  operation  the  boiler,  W,  is 
filled  with  about  130  hectolitres  of  exhausted  lant,  taken  from  the  vessels  C  and  C'. 
The  lant  in  A,  warm  in  consequence  of  having  served  for  condensation,  is  conveyed  to 
C  by  a  tube,  and  thence  by  the  tube,  h",  to  C',  cold  lant  being  poured  into  A.  The 
boiler,  W,  is  fitted  with  three  tubes,  viz.,  T,  the  steam  pipe,  m,  a  safety  tube,  brought 
to  within  a  few  centimetres  from  the  bottom  of  the  boiler,  and  carried  above  the  roof 
of  the  shed,  and  n  a  smaller  safety  tube ;  V  is  a  tube  fitted  with  a  stopcock.  The 
steam  evolved  in  W  is  carried  by  T  into  C",  evolving  from  the  liquid  therein  the  am- 


monium  carbonate  it  holds  in  solution.  The  carbonate,  with  the  steam,  passes  through 
t  into  the  vessel,  P,  which  serves  to  retain  any  liquid  carried  over  from  C'.  The  car- 
bonate of  ammonia  vapour  now  passes  from  P  through  the  tube,  T',  to  C,  and  taking 
up  in  that  vessel  more  ammonium  carbonate,  is  conveyed  through  the  tube,  T',  into  P' 
(which  again  serves  the  purpose  of  P),  and  thence  through  T"  into  the  leaden  worm  of 
the  condensing  apparatus.  The  condensed  liquor,  a  more  or  less  concentrated  solution 
of  ammonium  carbonate,  is  run  through  t"  into  S,  a  wooden  vessel,  lead  lined,  and  filled 
with  a  sufficient  quantity  of  sulphuric  acid  to  saturate  the  ammonium  carbonate.  The 
whole  operation  lasts  about  twelve  hours  ;  after  this  time  the  waste  liquid  in  the  boiler 
is  run  off  by  opening  the  stopcock,  F,  and  the  operation  again  repeated.  On  an  average 
the  lant  operated  upon  at  Bondy,  near  Paris,  yields  per  cubic  metre  from  9  to  12  kilos, 
of  ammonium  sulphate,  and  at  each  operation  200  kilos,  of  that  salt  are  obtained  by 
the  working  of  one  of  the  apparatus  just  described.  It  is  stated  that,  from  the  800,000 
cubic  metres  of  urine  yearly  run  waste  in  Paris  alone,  there  could  be  obtained,  by 
proper  treatment,  700,000  to  800,000  kilos,  of  ammonium  sulphate. 

Ammonia  from  Bones.— By  the  destructive  distillation  of  animal  substances,  such  as 
bones,  hoofs  of  horses,  refuse  horn,  skins,  hides,  decayed  meat,  &c.,  there  is  obtained  a 
series  of  products,  among  which  ammonium  carbonate  prevails,  with  cyanogen  com- 
pounds, ammonium  sulphide,  and  tarry  matter — a  very  complex  liquid  containing 


SECT.   III.] 


AMMONIA 


407 


pyrrol,  bases  of  the  ethylainme  series,  pyridin,  C5H5N,  picolin,  C6H7N,  lutidin,  C,H  N, 
and  collidin,  08HUN.  The  organic  matter  of  these  substances  contains  from  12  to  18 
per  cent,  nitrogen  ;  the  organic  matter  of  bones  contains  18  per  cent,  of  nitrogen,  and, 
as  the  organic  matter  amounts  to  about  one-third  of  the  weight  of  the  bones,  these 
contain  about  6  per  cent,  of  nitrogen.  Buffalo  horn  contains  17,  waste  woollen  fabrics 
10,  and  old  leather  6"j  per  cent,  of  nitrogen. 

It  is  evident  that  the  quantity  of  ammonia  in  the  products  of  the  dry  distillation 
of  animal  substances  depends  upon  the  kind  and  condition  of  these  materials,  and  upon 
the  temperature  at  which  the  operation  takes  place.  The  ammonium  carbonate  is 
obtained  in  the  condensers  as  a  solid  saline  mass,  the  crude  hartshorn,  or  sal  cornu  cervi, 
or  in  solution  (so  called  spiritus  cornu  cervi),  floating  on  the  surface  of  the  tar.  At  the 
present  time  the  manufacture  of  ammonia  and  its  salts  from  the  products  of  the  dry 
distillation  of  animal  substances  is  a  matter  of  but  limited  industrial  importance,  owing 
to  the  extended  coal-gas  manufacture.  Indeed,  dry  distillation  is  now  only  carried  on 
for  the  purpose  of  obtaining  animal  charcoal,  and  the  occurrence  of  ammoniacal  pro- 
ducts is  rather  considered  as  a  necessary  but  unavoidable  evil.  A  large  quantity  of 
animal  matter  is  used  for  the  manufacture  of  phosphorus  and  of  prussiates,  and  in 
these  operations  the  manufacture  of  ammoniacal  salts  is  either  left  altogether  out  of 
the  question  or  effected  only  on  a  limited  scale. 

Ammonia  from  Beet-Sugar. — When  the  beet-root  juice  is  boiled,  ammonia  is  evolved 
in  large  quantities,  and  may  be  utilised  in  the  preparation  of  ammonium  sulphate. 
The  ammonia  yielded  by  the  juice  is  the  product  of  the  decomposition  of  the  aspartic 
acid  and  betain  present  in  the  roots.  According  to  Renard,  a  beet-root  sugar  manu- 
factory which  yearly  consumes  200,000  cvvts.  of  beets  might  thus  obtain  887  cvvts.  of 
ammonium  sulphate. 

Technically  Important  Ammoniacal  Salts. — Sal-ammoniac,  ammonium  chloride, 
NH4C1,  consists  100  parts  of — 

Ammonia,  3 1  '83 )       f  Ammonium,  33  75 

Hydrochloric  acid,  68*22)       (Chlorine,        66 '25 

From  the  thirteenth  to  the  middle  of  the  eighteenth  century  this  salt  was  imported 
into  Europe  exclusively  from  Egypt,  where  it  was  obtained  by  the  combustion  of 
camel's  dung.  The  camel  feeds  almost  exclusively  upon'-  plants  containing  salts,  and 
the./sal-ammoniac  is  sometimes  found  ready  formed  in  the  animal's  stomach.  The  sal- 
ammoniac  having  » t  sublimed 

with  the  soot  from  the  com-  Fig. 

bustion  of  the  dung,  was  col- 
lected and  refined  by  a  second 
sublimation. 

In  localities  where  dung  is 
used  as  fuel,  it  has  been  tried 
to  obtain  sal-ammoniac  by 
combustion  with  common  salt. 
The  first  sal-ammoniac  manu- 
factory in  Germany  was  estab- 
lished  by  Gravenhorst 
Brothers,  at  Brunswick,  in 
1759.  We  have  already  seen 
how  crude  sal-ammoniac  may  be  prepared  from  gas-water  or  by  other  means.  The 
salt,  no  matter  whence  derived,  is  purified  by  sublimation  in  cast-iron  cauldrons, 
W>  Fig-  35 2,  Uned  with  fire-clay.  As  soon  as  the  crude  sal-ammoniac  is  put  into  these 
vessels  and  tightly  rammed,  heat  is  applied,  at  first  gently,  so  as  to  drive  off  any 


4o8 


CHEMICAL   TECHNOLOGY. 


[SECT.  in. 


353- 


moisture.  This  effected,  iron  lids,  F,  G,  H,  are  luted  to  the  cauldrons  ;  the  lids  can  be 
readily  moved  by  means  of  the  pulleys  and  chains  provided  with  counter-weights, 
B,  C,  D.  Instead  of  iron  covers  lead  hoods  sometimes  are  employed,  the  opening  of 
which  is  temporarily  closed  with  an  iron  disc.  The  hoods  or  covers  are  always  securely 
fastened  to  the  cauldrons,  to  prevent  them  being  forced  off  by  the  pressure  of  the 
vapours.  The  temperature  has  to  be  regulated  during  the  process  with  great  nicety, 
for  too  low  a  degree  of  heat  yields  a  loose  salt,  and  with  too  high  a  degree  of  heat  the 
organic  matter  present  in  the  crude  sal-ammoniac  is  liable  to  give  off'  empyreumatic 
matter,  spoiling  the  appearance  of  the  sublimed  salt  and  interfering  with  its  good 
quality.  Experience  has  proved  that  it  is  expedient  to  have  the  sublimation  vessels 
of  rather  large  size,  zj  to  3  metres  interior  diameter.  When  the  sublimed  sal- 
ammoniac  cake  has  attained  a  thickness  of  6  to  12  centimetres  the  operation  is  discon- 
tinued and  the  cake  removed.  The  furnace  is  provided  with  an  oven  for  drying  the 
sal-ammoniac,  this  oven  being  shut  with  a  door,  E,  movable  by  means  of  a  chain 
running  over  a  pulley,  and  aided  by  a  counterpoise.  At  the  present  day  sal-ammoniac 
is  often  sublimed  in  earthenware  vessels  or  large  glass  flasks,  the  crude  salt  being  first 
mixed  with  20  to  30  per  cent,  of  its  weight  of  powdered  animal  charcoal,  then  dried 
over  a  good  fire,  and  next  put  into  the  stoneware  sublimation  vessels,  B  and  M,  Fig. 
353,  placed  in  two  rows  over  the  fire-place,  G.  Each  of  these  vessels  is  50  centimetres  in 

height  ;  the  openings  are  surrounded 
by  an  iron  plate  properly  fitted  to  the 
neck  and  provided  with  a  flange  upon 
which  rest  the  earthenware  vessels 
wherein  the  sublimed  sal-ammoniac  is 
condensed.  When  glass  flasks  are  used, 
the  height  of  these  vessels  is  60  centi- 
metres by  30  centimetres  diameter. 
Sixteen  of  these  flasks,  each  charged 
with  9  kilos,  of  the  mixture  of  sal- 
ammoniac  and  charcoal,  are  placed 
upon  a  furnace  in  cast-iron  pots,  which 
are  filled  with  sand.  The  cover  is  in  this  case  a  leaden  plate.  The  sublimation  is  care- 
fully conducted,  and  goes  on  slowly,  lasting  about  twelve  to  sixteen  hours.  After  this 
time,  the  leaden  plates  are  removed,  bungs  or  plugs  of  cotton-wool  inserted,  and  the 
flasks  allowed  to  cool  very  gradually,  for  as  the  salt  expands  on  cooling  the  glass 
vessels  may  be  broken.  The  cake  of  sal-ammoniac  when  quite  cool  is  scraped  clean 
with  a  knife,  and  afterwards  presents  a  perfectly  crystalline  appearance.  When  it 
is  desired  to  obtain  the  salt  free  from  iron,  the  crude  salt  should  be  mixed,  before 
sublimation,  with  about  5  per  cent,  of  superphosphate  of  lime,  or  with  3  per  cent,  of 
ammonium  phosphate  ;  by  this  addition  any  iron  chloride  is  decomposed  and  left  in  the 
retort  as  phosphate.  The  sal-ammoniac  of  commerce  is  met  with  either  in  a  crystal- 
line state  or  as  a  compact  fibrous  sublimed  material  ;  in  the  latter  case  the  cakes  or 
discs  have  a  meniscus  shape,  weigh  abroad  from  5  to  10,  but  in  England  usually  about 
50  kilos.,  and  exhibit  the  appearance  of  having  been  formed  in  layers.  Crystalline 
sal-ammoniac  is  obtained  by  adding  to  previously  re-crystallised  sal-ammoniac  a 
boiling  hot  and  saturated  solution  of  the  same  salt,  so  as  to  form  a  thickish  magma, 
which  is  next  placed  in  moulds  similar  in  shape  to  those  in  use  for  making  loaf-sugar  ; 
after  draining,  the  loaf  of  sal-ammoniac  is  removed,  dried,  and  packed  in  paper  ready 
for  sale.  Besides  the  use  made  of  sal-ammoniac  in  chemical  laboratories,  by  pharma- 
ceutists and  veterinary  surgeons,  it  is  industrially  in  demand  for  tinning,  zincing,  and 
soldering,  in  calico-printing  and  dyeing,  in  the  manufacture  of  paints  and  pigments,  in 
the  preparation  of  platinum,  snuff,  and  very  largely  in  the  preparation  of  a  mastic  — 


S-ECT.  in.]  AMMONIA.  409 

i  part  of  sal-ammoniac,  2  of  sulphur,  and  50  of  iron  filings  —  used  in  joining  steam- 
pipes,  the  sockets  and  spigots  of  iron  gas-  and  water-pipes,  &c.  Sal-ammoniac  is  also 
employed  in  the  preparation  of  pure  ammonia  liquida  and  ammoniacal  salts. 

Ammonium  Sulphate.  —  It  has  been  already  mentioned  that  ammonium  sulphate, 
(NH4)2S04,  is  met  with  native  in  small  quantities  in  the  mineral  known  as  mascagnin, 
in  larger  quantities  in  the  boracic  acid  of  Tuscany,  while  it  is  also  found  in  Boussin- 
gaultite. 

The  modes  of  preparing  this  salt  from  the  ammoniacal  water  of  gas-works,  lant,  the 
products  of  the  dry  distillation  of  bones,  by  the  aid  of  sulphuric  acid,  or  by  double 
decomposition  by  means  of  gypsum  or  iron  sulphate,  have  been  already  given.  The 
concentration  of  the  weak  solution  by  evaporation  yields  the  crystalline  salt,  which, 
however,  when  obtained  from  liquors  containing  tarry  matters  is  usually  of  a  deep 
brown  colour,  and  has  therefore  to  be  purified  by  being  dissolved  in  hot  water,  filtered 
through  animal  charcoal,  and  then  re-crystallised,  the  best  plan  being  to  evaporate  the 
solution  rapidly,  and  remove  the  salt  gradually  by  means  of  perforated  ladles.  The 
salt  is  then  drained  by  being  placed  in  baskets,  and  next  quickly  dried  on  heated  fire- 
clay slabs,  in  which  operation  any  particles  of  tar  are  decomposed.  Sulphite  of 
ammonia  obtained  by  saturating  ammonium  carbonate  solution  with  sulphurous  acid 
gas  is,  when  exposed  to  air,  gradually  converted  into  sulphate.  Ammonium  sulphate 
is,  industrially  speaking,  far  the  most  important  of  the  ammonia  salts,  because  besides 
being  very  largely  used  in  artificial  manure  mixtures,  and  by  itself  for  the  same 
purpose,  it  is  extensively  employed  in  alum-making,  and  is  the  starting-point  of  the 
preparation  of  ammonium  chloride,  ammonium  carbonate,  liquid  ammonia,  and  other 
similar  products. 

Ammonium  Carbonate,  as  met  with  in  commerce,  was  formerly  supposed  to  be  am- 
monium sesquicarbonate,  but  the  investigation  of  H.  "Vogler,  in  1878,  showed  that  it  is 
approximately  a  mixture  of  ammonium  bicarbonate  and  carbaminate. 

The  salt  used  in  pharmacy  and  industry  under  this  name  is  in  reality  ammonium 
sesquicarbonate,  and  composed  according  to  the  formula 

(NH4)40308,  or  2([NH4]2C03)  +  CO2. 

It  is  obtained  either  directly  from  the  products  of  the  distillation  of  bones,  or  by  sub- 
liming a  mixture  of  chalk  and  sal-ammoniac. 

Among  the  products  of  the  dry  distillation  of  bones  is  found  a  solid  sublimate, 
essentially  impure  ammonium  carbonate,  purified  by  sublimation.  For  pharmaceutical 
use  ammonium  carbonate  is  prepared  by  submitting  a  mixture  of  either  ammonium 
chloride  or  sulphate  with  chalk  —  4  parts  of  the  ammonia  salt,  4  of  chalk,  and  i  of 
charcoal  powder  —  to  a  low  red  heat.  The  product  is  a  perfectly  pure  white  salt  ; 
during  the  operation  a  large  quantity  of  ammoniacal  gas  is  evolved,  which  is  either 
absorbed  by  water  or  by  coke  moistened  with  sulphuric  acid.  Kunheim  decomposes 
the  sal-ammoniac  by  subliming  it  with  barium  carbonate,  barium  chloride  being 
obtained  as  a  bye-product.  When  freshly  prepared,  ammonium  carbonate  is  a  trans- 
parent crystalline  mass,  which,  while  absorbing  water  from  the  atmosphere,  and 
evolving  ammonia,  is  superficially  converted  into  ammonium  bicarbonate  (ammonium 

"VTTT     •, 

hydrocarbonate,       jr4  [  C03).      Owing  to  the  penetrating  odour  emitted  by  this  salt, 


it  is  known  as  smelling  salts.  Impure  ammonium  carbonate  is  also  used  for  cleaning 
woollen  and  other  fabrics,  for  the  removal  of  grease  from  cloth,  and  further,  for  the 
production  of  the  orchil  pigments.  Pure  ammonium  carbonate,  besides  its  use  in 
pharmacy,  is  an  ingredient  of  baking  and  yeast  powders. 

Ammonium  Nitrate.  —  This  salt,  (NH4)N03,  is  prepared  by  the  double  decomposition 
of  solutions  of  ammonium  sulphate  and  potassium  nitrate.  The  potassium  sulphate 
is  first  separated,  and  the  solution  of  ammonium  nitrate  having  been  concentrated  by 


4  jo  CHEMICAL  TECHNOLOGY.  LSEGT-  m- 

evaporation  is  left  to  crystallise,  its  crystalline  form  being  similar  to  that  of  saltpetre, 
When  dissolved  in  water  this  salt  produces  cold,  and  is  therefore  used  in  freezing 
mixtures  ;  while  the  fact  that  when  strongly  heated  it  is  converted  into  nitrous  oxide 
and  steam  (N30  +  2H20)  might  perhaps  render  it  of  use  in  the  preparation  of  a 
blasting  powder. 

The  manurial  value  of  ammoniacal  salts  is,  according  to  C.  0.  Harz,  higher  than  it 
is  commonly  assumed.  Barley,  rice,  clover,  peas,  flourish  better  with  ammoniacal 
manures  than  with  nitre.  The  behaviour  of  maize  and  oats  is  the  reverse  ;  wheat  and 
barley  take  an  intermediate  position,  wheat  inclining  more  to  ammonia. 

PHOSPHORUS. 

Phosphorus  is  widely  distributed  in  nature  as  phosphates.  The  most  important 
phosphatic  mineral  is  Apatite,  Ca3Cl  (P04)3,  which  as  Phosphorite  and  Staffelite  forms 
massive  deposits  ;  less  abundant  are  Vivianite,  Fe3(P04)a.8H30  ;  Turquoise, 

A12P04(OH)3H20, 

and  pyromorphite,  Pb5Cl(P04)3.  Phosphorus  is  a  frequent  constituent  of  iron  ores 
and  a  very  important  ingredient  of  agricultural  soils,  being  necessary  for  all  culti- 
vated plants.  Phosphorus  is  also  an  indispensable  constituent  of  the  animal  body  — 
e.g.,  of  the  brain  ;  the  bones  consist  chiefly  of  calcium  phosphate. 

Preparation  of  Phosphorus.  —  Bone-ash  is  now  the  only  material  used  by  phosphorus 
makers,  as  the  commercial  preparation  of  phosphorus  has  not  succeeded  by  using  either 
apatite  and  other  varieties  of  pure  phosphorite  which  contain  about  18-6  per  cent,  of 
phosphorus  —  as  well  as  sombrerite  (a  mineral  met  with  on  the  American  island  of 
Sombrero),  consisting  of  calcium  phosphate  and  carbonate,  and  imported  into  England 
for  the  manufacture  of  superphosphates  ;  or  the  Navassa  guano,  also  imported  from 
the  United  States,  containing,  according  to  Ulex's  researches,  one-third  of  its  weight 
of  phosphoric  acid  ;  or  iron  phosphate,  as  proposed  by  Minary  and  Soudray,  by  dis- 
tilling that  substance  with  previously  well-ignited  coke-powder. 

Bones,  as  used  by  the  manufacturers,  contain  :  — 

In  dry  state,  but  not  ignited,      from  n  to  12*0  per  cent,  of  phosphorus. 
As  bone-black  „     16  to  i8'o         „  „ 

As  bone-ash  (white  burnt  bones)  „     20  to  25  -5         „  „ 

The  composition  of  bone-ash  is  exhibited  by  the  following  results  of  analysis  :  — 

i.  a. 

Calcium  carbonate  .....  10^07  ...  9*42 

Magnesium  phosphate     .        .        .        .  2-98  ...  2*15 

Tricalcium  phosphate      .        .        .        .  83  '07  ...  84*39 

Calcium  fluoride      .....  3-88  ...  4^05 

The  bone-ash  is  decomposed  by  means  of  sulphuric  acid,  according  to  a  plan  first 
suggested  by  Nicolas  and  Pelletier  :  — 

a.  Bone-ash,  Ca3(P04)2       }    .  ,  ,  (  Acid  calcium  phosphate,  CaH4(P04)z 

Sulphuric  acid,  2HaS04J  (Calcium  sulphate,  2CaS04. 

The  acid  calcium  phosphate  is  heated  with  charcoal,  and  converted  by  loss  of  water 
into  calcium  metaphosphate  :  — 


Acid  calcium          Calcium 
phosphate.      metaphosphate. 

Calcium  metaphosphate  yields,  when  ignited  to  a  white   heat  with  charcoal,  two- 
thirds  of  its  weight  of  phosphorus,  while  one-third  remains  in  the  residue  — 


SECT,  in.]  PHOSPHORUS.  411 

~  ,  .  ,       ,  „  ,-rt^.  x  .  ( Tribasic  calcium  phosphate,  Ca_(PO,)g 

c.  Calcium  metaphosphate,  3Ca(PO3U    •  lrl  !  .        .  s\      4/2 

i        ,-N  yielcl  1  Carbonic  oxide,  i  oCO 

Charcoal,  loC  '  1-™.      i  l» 

"Phosphorus,  4P. 

The  ordinary  mode  of  preparing  phosphorus  includes  the  following  operations : — 
In  some  instances  the  preparation  of  phosphorus  is  cotemporary  with  other  busi- 
nesses, viz.,  glue-boiling,  the  preparation  of  sal-ammoniac,  yellow  prussiate  of  potash, 
ifec.,  but  generally  in  England  the  phosphorus  makers  do  not  even  burn  the  bones  to 
ashes,  but  purchase  bone-ash  and  occasionally  apatite ;  this  salt,  however,  is  very  diffi- 
cult to  treat  with  sulphuric  acid,  and  is  also  objected  to  on  account  of  its  hardness,  for 
it  has  to  be  ground  to  a  very  fine  powder.  English  makers  only  carry  out  these 
four  processes  : — 

i.  Burning  the  bones  and  grinding  the  bone-ash  to  powder. 

2    Decomposition  of  the  bone-ash  by  sulphuric  acid,  and  evaporation  of  the  acid 
phosphate  previously  mixed  with  charcoal. 

3.  The  distillation  of  the  phosphorus. 

4.  The  refining  and  preservation  of  the  phosphorus. 

Burning  of  the  Bones  to  Ash. —  i.  The  bones  to  be  used  for  phosphorus  making  are 
obtained  either  from  bone-boilers  or  from  the  waste  bone-black  of  sugar-refiners.  The 
aim  of  the  ignition  of  the  bones  is  the  complete  destruction  of  the  organic  matter. 
The  operation  is  conducted  in  a  kiln  very  similar  to  those  in  use  for  burning  lime. 
A  layer  of  brushwood  having  been  put  at  the  bottom  of  the  kiln,  bones  form  the  next 
stratum,  and  so  on  alternately.  The  wood  having  been  lighted,  the  combustion  of  the 
bones  ensues.  In  order  to  carry  off"  the  fumes,  the  smell  of  which  is  very  offensive,  a  hood 
made  of  boiler-plate  is  placed  on  the  kiln,  and  either  connected  with  a  tall  chimney,  or 
the  smoke  and  gases  are  conducted  into  the  fire  of  the  kiln  and  burnt.  The  white 
burnt  bones  are  withdrawn  through  an  opening  reserved  in  the  wall  on  purpose,  the 
kiln  being  kept  continuously  in  operation,  as  is  the  case  with  some  lime-kilns. 

100  kilos,  of  fresh  bones  yield  from  50  to  55  kilos,  of  white  burnt  bone-ash,  which 
is  converted  into  a  coarse  powder  by  means  of  machinery. 

Decomposition  of  the  Bone-ash  l>y  Sulphuric  Acid. — 2.  100  kilos,  of  the  bone-ash,  of 
which  about  80  per  cent,  is  tribasic  phosphate,  require  for  decomposition  : — 
10673  kilos,  sulphuric  acid  of  1-52  specific  gravity. 
85-68     „  „  „  17°  „ 

73 '63    „  ..  »  1<8o  „ 

Payen  advises  that  for  100  kilos,  of  bone-ash  100  parts  of  sulphuric  acid  at  50  per 
cent,  or  1-52  sp.  gr.  be  taken.  The  operation  of  mixing  the  acid  and  bone-ash  is 
effected  in  lead-lined  wooden  tanks,  or  in  wooden  tubs  internally  coated  with  pitch  or 
coal-tar  asphalte.  The  liquor  decanted  from  the  precipitate  has  a  sp.  gr.  of  1*05  to 
1-07  =  12°  to  14°  Tw.  The  sediment  is  lixiviated  with  water,  and  the  liquor  obtained 
( =  6°  to  8°  Tw.)  evaporated  with  the  first  liquor  in  leaden  pans.  A  second  lixiviation 
of  the  sediment  yields  a  fluid  which  is  used  instead  of  water  for  the  purpose  of  diluting 
the  oil  of  vitriol.  The  evaporation  in  the  leaden  pans  (these  are  smaller,  but  otherwise 
similar  in  construction  to  those  used  for  evaporating  sulphuric  acid)  is  continued  until 
the  fluid  has  attained  a  sp.  gr.  of  i'45  =  84°Tw.,  when  it  is  mixed  with  charcoal- 
powder,  or  rather  granulated  charcoal,  of  the  size  of  small  peas,  in  the  proportion  of  20 
to  25  parts  of  charcoal  to  100  of  liquor,  and  quickly  dried  after  having  been  put  into 
cast-iron  pots  placed  on  a  furnace. 

The  dry  mass  consists  of  phosphate  of  lime,  carbon,  and  water,  to  an  amount  of 
5  to  6  per  cent.  At  the  commencement  of  the  manufacture  of  phosphorus  the  idea 
prevailed  that  in  the  preceding  preparation  the  phosphoric  acid  was  present  in  the  free 
-tate,  while  the  lime  had  combined  with  sulphuric  acid ;  but  Fourcroy  and  Vauquelin 
tinding  that  the  tribasic  calcium  phosphate  as  met  with  in  bone-ash  (Ca3(P04)2)  was,  by 


4t2  CHEMICAL  TECHNOLOGY.  [SECT.  ra. 

the  action  of  the  sulphuric  acid,  converted  into  acid  calcium  phosphate  (CaH4(PO4)2), 
supposed  that  more  sulphuric  acid  was  required,  an  opinion  opposed  by  Javal,  who 
proved  that  when  pure  phosphoric  acid  is  intimately  mixed  with  carbon,  it  yields  only 
a  small  quantity  of  phosphorus,  because  the  acid  is  volatilised  at  a  temperature  lower 
than  that  required  for  its  decomposition,  or  rather  reduction  by  carbon.  Owing  to 
the  presence  of  water  in  the  mixture,  there  is  given  off  during  the  distillation  in  addi- 
tion to  oxide  of  carbon,  hydrogen  carbide  and  phosphide. 

Distillation  of  Phosphorus. — 3.  The  mixture  of  acid  calcium  phosphate  and  char- 
coal is  distilled  in  fire-clay  retorts  similar  in  shape  to  those  used  for  distilling  Nbrd- 
hausen  sulphuric  acid,  while  the  furnace  in  which  these  retorts  are  placed  is  also 
similar  in  construction  and  holds  twelve  retorts  on  each  side.  The  body  of  the  retorts 
is  placed  on  the  side  of  the  fire,  while  the  neck  passes  through  an  opening  in  the  wall 
of  the  furnace,  that  portion  of  the  wall  being  only  lightly  bricked  up,  as  the  retorts, 
after  the  distillation  is  finished  and  the  furnace  cooled,  have  to  be  removed,  in  order 
to  clear  out  the  residue  and  introduce  fresh  mixture.  Between  each  pair  of  retorts  is 
left  a  space  of  some  1 2  to  15  centimetres,  in  order  to  afford  room  for  the  passage  of  the 
flame.  As  already  mentioned,  the  heat  causes  the  acid  calcium  phosphate,  (CaH4(P04)s), 
to  be  converted  into  calcium  metaphosphate,  (Ca(P03)2),  which,  with  increased  heat, 
gives  off  two-thirds  of  its  phosphorus,  there  being  left  in  the  retorts  one-third  in  the 
shape  of  calcium  triphosphate,  (Ca3(P04)2).  The  receivers  used  in  Germany  are  con- 
structed in  the  following  manner  : — The  material  is  clay,  glazed.  The  receiver  consists 
of  two  parts,  one  of  which  is  a  cylindrical  vessel  open  at  the  top,  into  which  the  other 
part  fits,  and  is  fixed  by  means  of  a  rim  which  is  prolonged  so  as  to  form  a  neck, 
between  which  and  the  first  part  is  inserted  a  tube  fitted  on  the  neck  of  the  retort, 
while  the  other  end  of  this  tube  dips  for  about  10  centimetres  into  the  receiver,  the 
latter  being  filled  with  water.  Into  each  retort  6  to  9  kilos,  of  the  mixture  intended 
to  be  operated  upon  are  introduced  ;  the  retorts  are  then  placed  in  the  furnace  and  the 
brickwork  is  restored.  This  having  been  done,  the  fire  is  kindled  and  kept  up  very 
gently  for  some  time  in  order  to  dry  the  fire-clay  used  in  joining  the  bricks.  The 
receivers  are  filled  with  water  and  fitted  to  the  retorts.  In  each  receiver  a  small  iron 
spoon  is  placed  fastened  to  an  iron  wire  which  serves  as  a  stem.  After  six  to  eight 
hours'  firing  the  heat  has  been  so  much  increased  as  to  cause  the  expulsion  of  any 
moisture  left  in  the  material  placed  in  the  retorts,  while  quantities  of  hydrocarbon  gase? 
and  oxide  of  carbon  are  formed  and  expelled  with  the  sulphurous  acid.  Subsequently 
other  gases  are  given  off,  and  because  they  contain  some  hydrogen  phosphide  are 
spontaneously  inflammable.  As  soon  as  this  phenomenon  is  observed,  the  joints  of  the 
receivers  and  apparatus  connecting  it  with  the  retort  are  luted  with  clay,  care  being 
taken  to  leave,  by  the  insertion  of  an  iron  wire,  a  small  opening  for  the  escape  of  the 
gases,  which  are  as  speedily  as  possible  removed  by  well-arranged  ventilators  from  the 
building  in  which  the  furnace  is  placed.  The  appearance  of  amorphous  phosphorus  at 
the  small  opening  indicates  the  commencement  of  the  distillation.  The  spoon  is  then 
placed  in  the  receiver  in  such  a  direction  that  any  phosphorus  coming  over  may  collect 
in  it.  During  the  progress  of  the  operation,  and  as  long  as  any  phosphorus  distils 
over,  the  evolution  of  combustible  gases  continues,  and  consequently  a  small  blue- 
coloured  flame  is  observed  at  the  opening  in  the  lute.  The  water  in  the  receivers  is 
kept  cool  during  the  operation.  After  forty-six  hours,  with  a  greatly  increased  firing, 
a  full  white-heat  is  reached,  and  the  quantity  of  phosphorus  coming  over  has  decreased 
so  much  as  to  make  a  continuation  of  the  ignition  process  wasteful.  The  receivers 
are  therefore  disconnected  from  the  retorts,  and  the  crude  phosphorus,  a  mixture  of 
phosphorus,  phosphorus  silicide  and  carbide,  amorphous  phosphorus,  and  other  allotropic 
modifications  of  this  element,  is  poured  into  a  tub  containing  water.  The  furnace 
having  become  cool  is  broken  up  and  the  retorts  are  removed,  the  contents  taken  out 


CECT.    III.] 


PHOSPHOKUS. 


413 


with  an  iron  spatula,  and  the  retorts  replaced  after  having  been  re-filled  with  fresh 
mixture.  100  kilos,  of  the  mixture  yield  about  14-5  kilos,  of  crude  and  12-6  kilos,  of 
refined  phosphorus.  As  to  Wohler's  method  of  preparing  phosphorus  by  the  ignition 
of  a  mixture  of  charcoal,  sand,  and  bone-ash,  the  process  is  not  well  adapted  for 
practical  use,  because  it  requires  a  very  high  temperature,  which  would  melt,  or  nearly 
so,  and  at  any  rate  soften,  the  retorts.  Moreover,  the  proposed  mixture  contains  only 
one-third  the  quantity  of  phosphoric  acid  met  with  in  the  mixture  now  in  general 
use. 

Refining  and  Purifying  the  Phosphorus. — 4.  As  already  stated,  the  crude  phos- 
phorus is  contaminated  with  carbon,  silicon,  red  and  black  phosphorus,  and  various 
other  impurities,  which  in  former  days  were  eliminated  by  forcing  the  phosphorus 
through  the  pores  of  stout  wash-leather  by  means  of  a  machine  exhibited  in  Fig.  354, 
C  representing  a  tightly  tied  piece  of  wash-leather  containing  the  crude  phosphorus, 


Fig.  354- 


Fig.  355- 


G 


Fig.  356. 


the  bag  being  placed  on  a  perforated  copper  support,  situated  in  a  vessel  filled  with 
water  at  50°  to  60°.  As  soon  as  the  phosphorus  is  molten,  there  is  placed  on  the 
wash-leather  a  wooden  plate,  D  D,  which  by  the  aid  of  the  mechanical  arrangement  E, 
and  the  lever,  G  G,  can  be  forced  downwards  so  as  to  cause  the  fluid  phosphorus  to 
pass  through  the  pores  of  the  leather,  the  impurities  being  retained.  More  recently 
French  manufacturers  have  introduced  another  system  of  purifying  phosphorus,  viz.  : — 
«.  By  filtration  through  coarsely  powdered  charcoal,  which  is  placed  in  a  layer  of  6  to 
10  centimetres  on  a  perforated  plate  of  the  vessel,  A,  Fig.  355,  two-thirds  filled  with 
water,  kept  by  means  of  the  water-bath,  B,  at  a  temperature  of  60°.  The  molten 
phosphorus  placed  on  A  passes  through  the  layer  of  charcoal,  and  is  thereby  purified. 
It  flows  through  the  open  tap,  (7,  and  the  tube,  E  (Fig.  356),  being  collected  in  the 
vessel,  F,  filled  with  water,  maintained  by  means  of  the  water-bath,  6f,  at  a  tempera- 
ture sufficiently  high  to  render  the  phosphorus  fluid,  so  that  it  may,  when  aided  by 
hydraulic  pressure,  pass  through  the  perforated  bottom,  II,  and  the  wash-leather 
spread  over  it.  The  filtered  phosphorus  may  be  run  off  by  means  of  the  tap,  J. 

According  to  another  process  of  purification  (6),  porous,  unglazed  porcelain  or 
earthenware  plates  are  fixed  in  an  iron  cylinder  connected  with  a  steam-boiler.  The 
steam  yielded  by  the  latter  forces  the  molten  phosphorus— previously  mixed  with  char- 
coal powder  for  the  purpose  of  preventing  the  pores  of  the  plates  becoming  choked— 
through  the  earthenware  plates.  The  charcoal  containing  some  phosphorus  is  used  in 
the  distillation  of  the  phosphorus.  This  method  of  purification  yields  from  100  kilos. 


CHEMICAL  TECHNOLOGY. 


[SECT.  HI. 


of  crude,  95  kilos,  of  refined,  phosphorus.  In  Germany  crude  phosphorus  is  purified 
by  distillation,  this  operation  being  carried  on  in  iron  retorts  of  a  peculiar  make,  and 
shaped  like  the  glass  retorts  used  in  chemical  laboratories.  The  neck  of  these  retorts 
dips  for  a  depth  of  15  to  20  millimetres  in  water  contained  in  a  basin  filled  to  the 
rim,  so  that  any  phosphorus  which  is  discharged  into  this  water  causes  it  to  over- 
flow. The  crude  phosphorus  having  been  fused  under  water  is  next  mixed  with  12 
to  1 5  per  cent,  of  its  weight  of  moist  sand,  and  this  mixture  is  placed  in  the  retorts 
in  quantities  of  5  to  6  kilos.,  the  object  of  the  mixing  with  sand  being  to  prevent 
the  phosphorus  becoming  ignited  during  the  filling  of  the  retorts.  Crude  anhydrous 
phosphorus  yields  by  this  process  of  distillation  about  90  per  cent,  of  the  refined 
product.  In  a  phosphorus  manufactory  at  Paris  the  crude  phosphorus  is  purified  by 
chemical  means — viz.,  by  mixing  with  TOO  kilos,  of  the  crude  substance  3-5  kilos,  of 
sulphuric  acid  and  the  same  quantity  of  bichromate  of  potash  ;  a  slight  effervescence 
ensues,  but  the  result  is  that  the  phosphorus  is  rendered  very  pure,  and  may,  after 
washing  with  water,  be  at  once  cast  in  the  shape  of  sticks.  The  yield  of  refined  phos- 
phorus by  this  process  is  96  per  cent. 

Moulding  the  Refined  Phosphorus. — It  has  long  been  the  custom  to  mould  phos- 
phorus into  the  shape  of  sticks  formed  by  the  aid  of  a  glass  tube  open  at  both  ends, 
one  of  these  being  placed  in  molten  phosphorus  covered  by  a  stratum  of  warm  water. 
The  liquid  phosphorus  is  sucked  by  the  operator  into  the  tube  until  it  is  quite  filled. 
The  lower  opening  of  the  tube  being  kept  under  water  is  closed  by  the  finger  of  the 
operator ;  the  tube  is  instantly  transferred  to  a  vessel  filled  with  very  cold  water,  bv 
which  the  phosphorus  is  solidified.  It  is  removed  from  the  glass  tube  by  pushing  it 
out  with  a  glass  rod  or  iron  wire  while  being  held  under  water.  Instead  of  suction  by 
the  mouth,  a  caoutchouc  bag  similar  to  that  used  in  volumetric  analysis  for  the  purpose 
of  sucking  liquids  into  pipettes  may  be  employed.  In  the  French  phosphorus  works 
the  glass  tubes  are  fitted  at  the  top  with  an  iron  suction  tube  provided  with  a  stop- 
cock. The  operator,  who  has  from  one  to  two  thousand  of  these  tubes  at  his  disposal, 
sucks,  either  by  mouth  or  with  a  caoutchouc  bag,  the  molten  phosphorus  into  the  glass 
tube,  and  having  turned  off  the  stop-cock,  rapidly  transfers  the  tube  to  a  vessel  filled 
with  cold  water.  When  all  the  tubes  are  filled  the  phosphorus  is  removed  by  opening 

the  stop-cock  and  pushing  the  stick  out 

Fig  357.  by  the  aid  of  a  wire.     A  clever   work- 

man may  mould  in  this  way  2  cwts.  of 
phosphorus  daily. 

Another  mode  of  performing  the 
moulding  has  been  introduced  by  Seu- 
bert.  The  apparatus  contrived  by  him 
for  this  purpose  is  exhibited  in  Fig.  357, 
and  consists  of  a  copper  boiler  fitted 
on  a  furnace ;  to  the  flat  bottom  of 
this  boiler  is  fastened  by  hard  solder 
an  open  copper  trough  communicating 
with  the  water-tank,  C.  In  the  boiler 
is  fitted  a  copper  funnel,  A,  provided 
with  a  horizontal  tube,  B.  This  portion 
of  the  apparatus  is  intended  for  the 
reception  of  the  phosphorus,  of  which 

it  will  hold  8  to  10  kilos.  At  the  end  of  the  horizontal  tube  is  placed  a  stop-cock,  B, 
while  the  portion  of  the  projecting  mouth  of  the  tube  beyond  the  cock  is  widened 
out  and  fitted  by  means  of  bolts  and  nuts,  with  a  flange-like  copper  plate,  into  which 
are  inserted  two  glass  tubes,  a  a.  Into  the  copper  trough  is  let  a  wooden  partition, 


SECT,  m.]  PHOSPHORUS.  415 

c  c,  which  serves  the  purpose  as  well  of  supporting  the  glass  tubes  as  of  preventing  the 
communication  of  the  hot  water  in  the  boiler  and  a  portion  of  the  trough  with  the 
cold  water  of  the  tank  and  the  portion  of  trough  nearest  to  it.  The  vessel  A  having 
been  filled  with  refined  phosphorus,  the  water  in  D  is  gently  warmed  so  as  to  cause  the 
fusion  of  the  phosphorus.  As  the  warm  water  reaches  to  the  partition,  c  c,  it  is  clear 
that  on  opening  and  closing  the  tap  B,  some  phosphorus  will  pass  through  and  flow 
out  of  the  tubes  a  a,  but  that  remaining  in  these  tubes  will  solidify,  and  on  opening 
the  tap  B  again  the  soh'd  sticks  of  phosphorus  may  be  removed  from  the  glass  tubes 
by  taking  hold  of  the  piece  of  projecting  phosphorus,  the  phosphorus  being  imme- 
diately immersed  under  water  in  the  tank  C,  and  kept  there  protected  from  the 
action  of  the  light.  While,  according  to  Seubert,  it  would  be  possible  for  a  workman 
to  mould  in  an  hour's  time  30  to  40  kilos,  of  phosphorus,  Fleck  has  found  that,  under 
the  most  favourable  conditions  of  temperature,  it  takes  six  hours  to  mould  50  kilos, 
of  phosphorus.  If  it  is  desired  to  prepare  granulated  phosphorus  with  this  apparatus, 
a  stratum  of  6  to  8  centimetres  thickness  of  hot  water  is  so  carefully  poured  on  cold 
water  as  not  to  mix  ;  next  the  tap,  B,  is  opened  sufficiently  to  cause  the  phosphorus 
to  form  drops,  which,  immediately  on  falling  into  the  cold  water,  becomes  a  hard  solid 
mass.  For  practical  purposes  granulated  phosphorus  is  preferable  to  the  moulded 
sticks.  The  phosphorus  is  stored  either  in  strong  sheet-iron  tanks  or  in  wooden  boxes 
lined  with  thinner  (tinned)  sheet-iron,  these  vessels  being  capable  of  holding  6  cwts. 
of  phosphorus  covered  with  a  stratum  of  water  fully  3  centimetres  deep.  When  large 
quantities,  say,  from  i  to  5  cwts.,  of  phosphorus  have  to  be  sent  off,  it  is  usually 
packed  in  water  in  small  wine  casks,  and  the  casks  having  been  tightly  closed,  are 
coated  externally  with  molted  pitch,  then  rolled  through  chaff,  and  lastly  covered  with 
stout  canvas  sewed  tightly  round  the  cask.  Another  method  of  packing  phosphorus 
consists  in  placing  it  in  well-made  water-tight  sheet-iron  or  tinned  iron  canisters,  such 
as  are  largely  used  in  London  for  the  purpose  more  particularly  of  conveying  oil 
paints,  and  which  are  closed  by  soldering  on  a  lid  very  securely.  In  some  cases  these 
canisters  are  packed  in  wooden  boxes  to  the  number  of  six  or  twelve,  according  to  size 
and  weight. 

The  process  for  obtaining  phosphorus  proposed  by  Fleck  depends  on  the  solubility 
of  calcium  phosphate  in  hydrochloric  acid  and  its  separation  as  acid  calcium  phosphate 
on  evaporating  down  the  solution  in  stoneware  vessels.  According  to  theory  156 
parts  calcium  triphosphate  Ca3(P04)2  require  73  parts  anhydroiis  hydrochloric  acid, 
yielding  in  parts  calcium  chloride,  100  parts  acid  calcium  phosphate,  and  18  parts  of 
water.  On  igniting  100  parts  acid  calcium  phosphate  and  20  parts  carbon  there  are 
formed  21-3  parts  phosphorus,  5*2  parts  calcium  triphosphate,  and  46*7  parts  carbon 
monoxide.  If  the  residual  mixture  of  calcium  triphosphate  and  carbon  is  incinerated 
and  again  treated  with  hydrochloric  acid,  calcium  phosphate  is  again  obtained  from  the 
solution  on  evaporation  and  so  on.  It  is  thus  possible  to  extract  in  this  manner  all 
the  phosphorus  from  the  bones  if  the  acid  is  free  from  sulphuric  acid.  The  bones, 
cleansed,  broken  up  and  freed  from  fat,  are  treated  with  dilute  hydrochloric  acid  at 
10°  Tw.  The  bones  are  then  laid  in  hydrochloric  acid  at  5°  Tw.,  in  which  they  are  left 
until  completely  softened ;  this  second  liquid  serves  instead  of  water  for  mixing  the 
acid  for  the  lixiviation  of  fresh  bones.  When  the  first  liquid,  a  solution  of  acid 
calcium  phosphate  and  calcium  chloride,  marks  24°  Tw.,  it  is  placed  in  the  evaporating 
vessels. 

In  the  choice  of  these  vessels  lies  one  of  the  difficulties  of  the  Fleck  process,  as 
hydrochloric  solutions  cannot  be  evaporated  in  leaden  vessels,  but  require  the  use  of 
stoneware  vessels,  not  easy  to  be  procured.  The  lye  crystallises  when  it  reaches  50°  Tw. 
The  crystalline  paste  is  pressed  and  mixed  with  one-fourth  its  weight  of  charcoal  powder 
in  an  earthen  pan  at  100°  and  rubbed  through  a  copper  sieve.  The  crude  phosphorus 


416 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


obtained  is  refined  and  moulded  as  usual.  The  residue  of  calcium  phosphate  and 
carbon  is  incinerated  and  lixiviated  with  strong  hydrochloric  acid.  The  bones  which 
have  been  freed  from  calcium  phosphate  are  worked  up  for  glue. 

Properties  of  Phosphorus. — When  perfectly  pure  and  kept  under  distilled  water, 
which  previously  to  being  employed  for  this  purpose  has  been  by  boiling  deprived  of 
the  air  it  held  in  solution,  and  has  been  cooled  either  under  a  layer  of  oil  or  in  well- 
stoppered  bottles,  and  in  perfect  darkness,  phosphorus  is  a  colourless  and  transparent 
substance ;  but  usually  it  has  a  white-yellow  colour  and  waxy  appearance.     Its  sp.  gr. 
is  =  i"3  to  i '84.     When  the  temperature  of  the  air  is  not  too  low  this  element  is  as 
soft  as  wax,  but  becomes  brittle  in  cold  weather.     Phosphorus  cannot  be  pulverised ; 
is  tough ;  but  when  molten  in  a  bottle  under  warm  water  and  shaken  until  the  fluid 
is  quite  cold  the  substance  is  thereby  reduced  to  a  finely  divided  state ;  instead  of 
water  it  is  better  to  use  either  alcohol,  urine,  or  a  weak  aqueous  solution  of  urea. 
Phosphorus  fuses  at  44°  to  45°,  and  remains,  especially  if  kept  under  an  alkaline 
solution,  fluid  for  a  considerable  time  though  cooled  far  below  its  melting-point,  but 
solidifies  suddenly  when  touched  by  a  solid  body.     At  290°  phosphorus  boils,  and  it 
evaporates  sensibly  at  the  ordinary  temperature  of  the  air.     By  slow  oxidation  (fumes 
of  phosphorus  are  given  off  at  the  ordinary  temperature  of  the  air)  there  is  formed  not 
only  phosphorus  acid  but  nitrate  of  ammonia  and  antozone.     Phosphorus  is  in  the 
state  of  vapour  slightly  soluble  in  water.     The  solid  element  itself  is  slightly  soluble 
in  alcohol  and  ether,  also  in  linseed  oil  and  oil  of  turpentine,  the  best  solvents  being 
sulphide  of  carbon,  chloride  of  sulphur,  and  chloride  of  phosphorus.     At  75°  phos- 
phorus ignites  in  contact  with  air,  and  in  order  to  ignite  it  by  friction  this  temperature 
has  to  be  reached.     Amorphous  or  red  phosphorus  requires  a  very  high  temperature 
(300°)  for  ignition.     Commercial  phosphorus  usually  contains  some  impurities,  such  as 
sulphur,  arsenic,  and  sometimes  traces  of  calcium,  due  to  the  lime  of  the  bone-ash  used 
in  the  preparation.     Beside  being  used  in  chemistry,  phosphorus  is  chiefly  employed  in 
the  making  of  matches  ;  also  for  what  is  termed  liquid  fire  (a  solution  of  phosphorus 
in  sulphide  of  carbon),  for  the  preparation  of  tar  colours,  and  for  hardening  some 
copper  alloys. 

Amorphous  or  Red  Phosphorus. — Dr.  Schrotter,  of  Vienna,  discovered  in  1848  that 
the  property  possessed  by  ordinary  phosphorus  (first  noticed  in  1844  by  E.  Kopp)  of 

becoming  coloured  red  by  the  action  of  light,  was 

Fl'--  358.  due  to  the  formation  of  an  allotropic  modification, 

which  has  been  since  termed  red  or  amorphous 
phosphorus.  This  is  best  prepared  by  heating 
ordinary  phosphorus,  with  exclusion  of  air  and 
water,  in  a  closed  vessel  and  under  pressure,  to 
250°  for  a  length  of  time.  On  the  large  scale  this 
operation  is  conducted  in  an  apparatus  invented 
by  A.  Albright,  of  Birmingham.  In  Fig.  358, 
g  represents  a  glass  or  porcelain  vessel,  filled  for 
five-sixths  of  its  capacity  with  pieces  of  phosphorus 
to  be  heated  to  230°  to  250°.  The  vessel,  /,  is 
placed  in  a  sand-bath,  b,  heated  by  the  fire.  To 
the  vessel,  g,  is  fitted  an  air-tight  lid,  into  which 
is  fastened  the  bent  tube,  i,  provided  with  a  tap, 
k,  and  dipping  into  the  vessel,  n,  which  is  filled 
with  water,  or  preferably  with  mercury  covered 
with  a  layer  of  water.  The  tap,  k,  is  left  open  at  the  commencement  of  the  operation 
for  securing  the  escape  of  the  air  contained  in  g,  and  as  soon  as  no  more  air  escapes 
the  tap  is  closed,  and  the  heat  increased  so  as  to  convert  the  ordinary  into  amorphous 


SECT,  in.]  MATCHES:   PRODUCTION   OF   FIRE.  417 

phosphorus.  The  time  required  for  the  operation  depends  upon  conditions  which 
can  be  met  only  by  experience.  After  the  thorough  cooling  of  the  apparatus,  the 
vessel,  g,  is  opened,  and  the  red  phosphorus  removed.  It  is  then  placed  under  water 
and  crushed  to  a  pulp  in  order  to  remove  any  unconverted  ordinary  phosphorus. 
Carbon  disulphide  might  be  used  for  this  purpose,  but  the  danger  of  ignition  (by 
accident)  of  the  solution  of  ordinary  phosphorus  thus  obtained  is  prohibitive.  Nickles 
proposes  to  separate  ordinary  from  amorphous  phosphorus  by  shaking  up  the  mixture  of 
amorphous  and  ordinary  phosphorus  with  a  fluid,  the  specific  gravity  of  which  is  less 
than  that  of  amorphous  phosphorus  (2*1),  and  greater  than  that  of  ordinary  phos- 
phorus (i'84).  A  solution  of  calcium  chloride  at  66°  to  71°  Tw.  can  be  used  for  this 
purpose ;  the  ordinary  phosphorus  floats  in  this  fluid  and  can  then  be  readily  taken 
up  by  carbon  disulphide,  while  the  operation  can  be  carried  on  in  a  closed  vessel. 
When  very  large  quantities  of  amorphous  phosphorus  have  to  be  purified  it  is  best 
to  follow  Coignet's  plan,  consisting  in  treating  the  boiling  mixture  of  the  two  varieties 
of  phosphorus  with  caustic  soda  solution,  whereby  the  ordinary  phosphorus  is  con- 
verted into  phosphuretted  hydrogen  gas,  and  sodium  hypophosphite  formed,  the 
remaining  amorphous  phosphorus  being  purified  by  washing  with  water.  R.  Bottger 
suggests  the  use  of  a  solution  of  copper  sulphate,  which  with  ordinary  phosphorus 
forms  copper  phosphide. 

Properties  of  Amorphous  Phosphorus. — This  substance  occurs  either  in  powder  of  a 
red  or  scarlet  colour  or  in  lumps  of  a  red-brown  hue ;  fracture  conchoidal,  sometimes 
with  an  iron-black  hue;  sp.  gr.  =  2'i.  Amorphous  phosphorus  is  not  soluble  in 
carbon  disulphide  or  other  solvents  of  ordinary  phosphorus.  It  is  unaltered  by 
exposure  to  air ;  and  when  heated  to  290°  is  re-converted  into  ordinary  phosphorus. 
When  mixed  and  rubbed  with  dry  potassium  bichromate,  red  phosphorus  does  not 
explode,  and  when  mixed  with  nitre  it  does  not  burn  off  by  friction,  but  only  by 
application  of  heat,  and  then  noiselessly.  It  explodes,  however,  when  mixed  with 
potassium  chlorate.  With  lead  peroxide,  amorphous  phosphorus  ignites  by  friction 
with  a  slight  explosion,  but  when  heat  is  also  applied  a  violent  explosion  ensues. 

Owing  to  its  properties  and  behaviour  with  several  oxides,  its  non- volatility 
and  non-poisonous  properties,  as  well  as  on  account  of  its  less  ready  ignition, 
amorphous  phosphorus  is  an  excellent  material  for  the  making  of  matches ;  but 
amorphous  phosphorus  is  not  in  general  use  for  this  purpose.  It  is,  however,  used  for 
preparing  phosphorus  iodide,  which  serves  for  the  preparation  of  iodides  of  amyl. 
ethyl,  and  methyl,  used  in  the  manufacture  of  cyanin,  ethyl  violet,  and  other  coal-tar 
colours.  Sir  William  Armstrong's  explosive  mixture  for  shells  contains  amorphous 
phosphorus  and  potassium  chlorate.  From  66,000  cwts.  of  bones  there  are  annually 
prepared  in  Europe  some  5500  cwts.  of  phosphorus. 

The  production  of  phosphorus  in  1 880  was  approximately  as  follows : — 

England  (Albright  &  Wilson  at  Oldbury,  near  Birmingham)     1750  tons 
France  (Coignet  Freres,  at  Lyons)  .         .         .                   .         .     1500     ,, 
Philadelphia 18     „ 

There  is  a  phosphorus  factory  in  Sweden,  but  its  output  is  not  known.  The  yearly 
consumption  of  phosphorus  in  Germany  is  estimated  at  1200  tons. 

MATCHES:  PRODUCTION  OF  FIRE. 

In  the  year  1823,  Dobereiner,  at  Jena,  discovered  that  finely  divided  spongy 
platinum  has  the  property  of  igniting  a  mixture  of  atmospheric  air  and  hydrogen  gas, 
and  he  contrived  the  so-called  Dobereiner  hydrogen  lamp,  which  has  been,  and  is  still 
occasionally,  employed  to  procure  fire  and  light.  About  the  same  period  there  was 
invented  a  kind  of  phosphorus  match  of  the  following  arrangement : — Equal  parts  of 

2  D 


4i 8  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

sulphur  nnd  phosphorus  were  cautiously  fused  in  a  glass  tube ;  after  the  fusion  was 
completed  the  tube  was  tightly  corked.     If  it  were  desired  to  obtain  fire,  a  thin  splint 
of  wood  was  immersed  in  this  mixture,  and  some  of  it  having  been  fixed  to  the  wood,  the 
latter  on  being  brought  into  the  air  became  ignited  by  the  combustion  of  the  mixed 
substances,  which  took  fire  spontaneously  in  the  air.     It  is  evident  that  this  rather 
clumsy  contrivance  never  became   general.     Of    far  more  importance  as  suited  for 
practical   purposes  were  the  chemical  matches  or  dip  splints,  first  manufactured  at 
Vienna,  as  early  as  1812.     These  splints  were  tipped  with  sulphur  covered  with  a 
mixture  of  potassium  chlorate  and  sugar,  to  which  for  the  purpose  of  imparting  colour 
was  added  some  vermilion,  while  a  little  glue  gave  a  pasty  and  adhesive  consistency. 
By   touching   this   composition  with  concentrated   sulphuric    acid    ignition    ensued ; 
the  acid  was  kept  in  a  small  glass  or  leaden  bottle  into  which  some  asbestos  had  been 
inserted,  which  acted  as  a  sponge  for  the  acid.     The  only  friction  matches  known  up 
to  the  year  1844  were  discovered  and  made  by  M.  Chancel,  assistant  to  the  well-known 
Professor  Theiiard  of  Paris,  1805.     The  "  Promethean s,"  first  made  in  England  in  or 
about  the  year  1830,  were  contrived  on  the  same  principle,  viz.,  the  ignition,  by  friction 
between  two  hard  substances,  of  a  mixture  of  potassium  chlorate  and  sugar  fixed  to  a 
kind  of  paper  cigarette,  which  contained  also  a  small  glass  globule  filled  with  sulphuric 
acid  ;  however,  the  high  price  of  this  kind  of  match  prevented  its  general  use.     Under 
the  name  of  "  Congreves"  the  first  real  friction  matches  were  made  in  1832.     On  the 
sulphur-tipped  splints  was  glued  a  small  quantity  of  a  mixture  of  one  part  of  potas- 
sium chlorate  and  two  parts  of  black  antimony  sulphide,  to  which  some  gum  or  glue 
was  added.     By  strongly  rubbing  this  composition  between  two  pieces  of  sand-paper 
the  mixture  became  ignited,  but  frequently  also,  on  becoming  detached  from  the  wooden 
splint,  flew  about  in  all  directions  without  igniting  the  sulphur  or  the  wood.  It  is  not  well 
known  who  was  the  first  to  substitute  phosphorus  for  antimony  sulphide ;  but  accord- 
ing to  Nickles,  phosphorus  matches  were  already  used  in  Paris  as  early  as  1805,  while 
in  1809  Derepas  proposed  to  mix  magnesia  with  phosphorus  in  order  to  lessen  its  great 
inflammability  when  in  a  finely  divided  state.     Derosne  (i Si 6)  appears  to  have  been  the 
first  who  made  phosphorus  friction  matches  at  Paris.     However,  it  was  not  before  the 
middle    of    1833   that   phosphorus  matches    became   more    generally   known,   when 
Preshel,   at   Vienna   (a   city  famous  for  the  match  and  fusee   industry),  made  not 
only  phosphorus  matches,  but  also  fusees  and  German  tinder  slips  tipped  with  the 
phosphorus  composition.     About  the  same  period  F.  Moldenhauer,  at  Darmstadt,  made 
phosphorus  lucifer  matches.    The  South  Germans  attribute  to  Kammerer  the  invention 
of  phosphorus  lucifer  matches,  while  in  England,  according  to  the  opinion  of  the  late 
celebrated  Faraday,  John  Walker,  of  Stockton,  Durham,  was  the  inventor  of  lucifer 
matches,  or  at  least  the  first  maker.     The  older  kind  of  matches,  although  very  com- 
bustible, ignited  with  a  rather  sharp  report,  owing  to  the  presence  of  chlorate  of  potash 
in  the  mixture,  while,  moreover,  the  too  ready  ignition  by  concussion  rendered  the 
carriage  of  these  matches  so  unsafe  that  in  Germany  the  transport,  as  well  as  the 
manufacture,  became  prohibited.     In  the  year  1835  Trevany  substituted  a  mixture 
of  red  lead  and  manganese  for  a  portion  of  the  chlorate  of  potash,  thereby  greatly 
improving  the  composition.     In  1837  Preshel  altogether  discarded  this  salt,  substituting 
peroxide  of  lead,  or,  as  Bottger  advised,  either  a  mixture  of  red  lead  and  potassium 
nitrate,  or  of  lead  peroxide  and  nitrate.     From  this  period  the  manufacture  of  matches 
became  an  extensive  industry,  greatly  aided  by  the  manufacture  of  phosphorus  on 
the  large  scale. 

In  the  course  of  time  other  improvements  were  made,  as,  for  instance,  the  substitu- 
tion for  sulphur  of  wooden  splints,  thoroughly  dried  and  soaked  in  wax,  paraffine,  or 
stearic  acid,  and  the  coating  of  the  composition  with  a  varnish  to  protect  it  from  the 
action  of  moisture,  while,  at  the  same  time,  the  appearance  of  the  matches  was 


SECT,  in.]  MATCHES:   PRODUCTION   OF   FIRE.  419 

rendered  more  ornamental.  At  the  present  day  matches  are  the  product  of  an  industry 
which  cannot  possibly  be  much  more  improved  in  a  technical  point  of  view,  besides 
being,  as  regards  price,  within  the  reach  of  all. 

However  useful  phosphorus  lucifer  matches  may  be,  it  is  a  great  drawback  to  their 
utility  that  the  combustible  composition  is  a  poisonous  mixture  ;  while,  moreover,  the 
workpeople  engaged  in  that  department  of  the  lucifer-match  making  in  which  the 
phosphorus  is  handled  are  often  affected  by  a  peculiar  kind  of  caries  of  the  jawbones, 
the  real  cause  of  which  is  the  more  difficult  to  ascertain  as  the  workpeople  engaged  in 
the  manufacture  of  phosphorus,  and  exposed  to  its  vapours  to  such  an  extent  as  to 
render  their  breath  luminous  in  the  dark,  are  not  similarly  affected.  The  discovery  of 
the  red  or  amorphous  phosphorus,  which  is  neither  poisonous  nor  very  inflammable, 
affords  a  happy  substitute  for  the  ordinary  phosphorus,  but  the  former  is  by  no  means 
generally  used  in  the  preparation  of  matches. 

Manufacture  of  Lucifer  Matches. — The  operations  required  are : 

1.  The  preparing  of  the  splints  of  wood. 

2.  The  mixing  of  the  combustible  composition. 

3.  The  dipping,  drying,  and  packing  of  the  matches. 

i.  The  Preparation  of  the  Wooden  Splints. — Generally  white  woods  are  used  for 
this  purpose,  such  as  white  fir,  pine,  aspen,  more  rarely  fir  (Fohrenholz),  some- 
times beech,  lime-tree,  birch,  willow,  poplar,  and  cedar.  The  shape  of  the  splints 
is  usually  square  in  section,  but  abroad  the  splints  are  sometimes  cylindrical. 
The  square  splints  are  readily  made  by  hand,  simply  by  splitting  up  a  block  of 
wood  of  the  length  required  for  the  splint.  A  cutting  tool,  a  large  knife,  similar 
to  that  which  is  sometimes  used  by  chaff-cutters,  is  very  frequently  used  for  the 
purpose  of  cutting  the  wooden  splints,  while  a  contrivance  similar  to  that  in  use 
for  propelling  the  hay  or  straw  forward  is  also  employed,  being  so  arranged  as,  after 
every  cutting  stroke,  to  propel  the  wood  the  length  required  for  a  splint.  More 
generally  the  operation  of  splitting  the  block  of  wood  parallel  to  its  fibres  and  next 
cutting  off  the  splints  to  the  required  length  is  effected  by  machinery,  consisting  of  fixed 
knives,  against  which  the  wood  is  moved  with  sufficient  force  to  split  it  up  into  splints, 
which  are  next  cut  to  the  required  length.  Instead  of  splitting  the  wood  by  these 
means,  the  splints  are  now  in  Germany  always  made  by  a  kind  of  plane,  invented  by 
S.  Romer,  of  Vienna,  by  which  the  wood  is  cut  into  circular  splints.  The  cutter  of 
this  plane  differs  from  that  of  the  ordinary  carpenter's  plane  in  possessing,  instead  of 
the  cutting  edge,  a  slight  bend,  in  which  three  to  five  holes  have  been  bored  in  such  a 
manner  that  one  of  the  edges  of  these  holes  is  sharpened ;  in  practice,  three  holes  are 
preferred.  When  this  plane  is  forced  against  a  lath  of  wood,  placed  edgeway,  the 
cutting  tool  penetrates  into  the  wood,  splitting  it  up  into  as  many  small  sticks  or 
splints  as  the  cutter  contains  holes.  When  a  number  of  thin  splints  have  been  cut 
from  the  lath,  it  is  again  planed  true  with  an  ordinary  plane  and  then  the  operation 
repeated.  The  dividing  of  the  thin  sticks  into  splints  of  the  required  length  is  effected 
by  a  tool  consisting  of  a  narrow  trough  about  6  centimetres  wide  and  provided  with  a 
slit  in  which  works  a  knife  fastened  to  a  lever.  A  clever  workman  can  prepare  400,000 
to  450,000  splints  daily.  In  the  south-west  of  Germany  a  plane  for  cutting  wooden 
splints,  the  invention  of  Anthon,  at  Darmstadt,  and  similar  in  action  and  construction 
to  that  above  mentioned,  is  in  general  use ;  but  throughout  an  extensive  portion  of  the 
empire  the  manufacture  of  the  splints  has  become  a  separate  trade,  often  carried  on  in 
woods  and  forests,  the  splints  being  sold  to  the  lucifer-match  makers  in  bundles  ready 
for  dipping. 

Instead  of  making  the  splints  by  hand,  they  are  occasionally  made  by  a  machine, 
such  as  that  of  Pelletier,  at  Paris  (1820),  having  on  a  bench  a  plane  36  centimetres 
long  by  9  wide,  made  to  move  backwards  and  forwards,  while  a  piece  of  wood  is  placed 


420  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

so  that  it  is  caught  by  the  fore-cutter,  which  consists  of  a  steel  knife  provided  with 
twenty-four  teeth  sharpened  like  little  knives,  the  second  cutter  removing  the  small 
laths  from  the  plank  of  wood.  Cochot's  machine  (1830)  consists  of  a  large  iron  wheel 
i  metre  in  diameter,  on  the  periphery  of  which  are  fixed  thirty  wood»n  blocks  length- 
ways of  the  size  of  the  splints.  When  the  wheel  is  turned  round,  the  blocks  of  wood 
are  caught  by  the  knives  fastened  to  a  small  cylinder,  and  the  wood  is  split  up  into 
splints,  which  are  removed  from  the  block  by  another  knife.  Jeunot's  machine, 
patented  in  1840  in  France,  is  of  a  similar  construction.  Neukrantz,  at  Berlin  (1845), 
contrived  a  tool  based  upon  the  principle  of  the  hand-plane,  the  wood  intended  to  be 
cut  being  moved  against  a  fixed  steel  cutter,  which  produced  sixteen  to  twenty  splints 
at  a  movement.  Krutzsch,  at  Wlinschendorf,  Saxony,  has  improved  upon  this  plan 
(1848)  by  perforating  a  steel  plate  with  about  400  holes  placed  as  near  together  as 
possible ;  the  edges  of  these  holes  having  been  sharpened,  a  block  of  wood  is  forced  in 
the  direction  of  its  fibres  against  the  plate  and  thus  divided  into  splints.  A  piece  of 
wood  3  centimetres  in  thickness  and  width  by  i  metre  in  length  yields  400  lengths, 
each  of  which  can  be  cut  up  into  fifteen"  splints  ;  6000  of  the  latter  are  made  in  two 
minutes.  Of  the  several  tools  and  machines  contrived  for  the  purpose  of  cutting 
splints — and  the  number  of  these  contrivances  is  very  large — we  quote  the  following  of 
German  origin.  The  machine  invented  by  C.  Leitherer,  at  Bamberg  (1851),  consists 
of  what  might  be  termed  a  kind  of  guillotine,  viz.,  a  box  at  the  bottom  of  which  is 
placed  the  wood  to  be  formed  into  splints,  the  fibre  of  the  wood  being  vertical.  In 
front  of  this  box  is  placed  a  framework,  in  which  a  heavy  block,  provided  with  four 
cutters,  each  terminated  by  eight  to  ten  narrow  tubes  (somewhat  similar  to  cork- 
borers),  can  be  made  to  move  rapidly,  so  as  to  give  forty-five  strokes  a  minute,  the 
wooden  block  intended  to  be  cut  into  splints  being  made  to  move  under  the  cutting 
tool  after  each  stroke.  Wrana's  machine  is  in  principle  the  same  as  that  of  Neukrantz, 
but  has  been  greatly  improved,  the  plane  not  being  fixed,  but  supported  by  a  piece  of 
wood.  Long's  machine,  again,  consists  of  a  series  of  cylinders,  between  which  the 
block  of  wood  is  placed,  while  knives  are  so  arranged  as  to  cut  the  block  into  splints 
while  the  wood  moves  on  by  the  motion  imparted  to  the  cylinders. 

3,.  The  Preparation  of  the  Combustible  Composition  is  carried  on  in  the  following 
manner : — The  glue,  or  gum,  or  any  other  similar  substance  is  first  dissolved  in  a 
small  quantity  of  water  to  the  consistency  of  a  thin  syrup,  with  which,  having  been 
heated  to  50°,  the  phosphorus  is  incorporated  by  gradually  adding  it  and  keeping  the 
mixture  stirred  so  as  to  form  an  emulsion,  to  which  are  next  added  the  other  ingre- 
dients after  having  been  pulverised.  In  order  to  obtain  a  good  composition,  it  is 
essential  that  there  should  be  neither  too  much  nor  too  little  phosphorus,  for  an  excess 
of  phosphorus  will  not  only  tend  to  increase  unnecessarily  the  price  of  the  composition, 
but  it  has  also  the  effect  of  rendering  it  unfit  for  igniting  the  sulphur  and  stearin 
wherewith  the  matches  are  tipped,  because  the  phosphoric  acid  generated  by  the  com- 
bustion of  the  phosphorus  is  deposited  as  an  enamel-like  mass,  which  prevents  further 
combustion.  It  appears  that  the  best  proportion  is  from  one-tenth  to  one-twelfth  of 
phosphorus. 

A  much  smaller  quantity  of  phosphorus  is  required  if  this  element  is  first  dissolved 
in  carbon  disulphide  and  the  solution  added  to  the  other  constituent  of  the  composi- 
tion ;  the  carbon  disulphide  while  rapidly  volatilising  leaves  the  phosphorus  in  a  very 
finely  divided  state.  As  phosphorus  is  very  readily  soluble  in  sulphide  of  carbon,  and 
as  the  latter  is  moderately  cheap,  the  method  has  the  advantage  that  the  mixing  of 
the  materials  can  take  place  without  the  application  of  heat.  It  is,  however,  evident 
that  the  greatest  care  is  required  in  manipulating  such  a  liquid  as  sulphide  of  carbon, 
and  far  more  when  phosphorus  is  dissolved  therein.  C.  Puscher  suggested  (1860)  the 
use  of  phosphorus  sulphide,  PXS,  instead  of  pure  phosphorus  in  the  composition  for 


SECT.    III.] 


MATCHES:  PRODUCTION  OF  FIKE. 


421 


matches.  He  prepared  a  composition  containing  3^5  per  cent,  of  this  sulphuret,  and 
obtained  excellent  matches. 

Among  the  metallic  oxides  which  are  employed  in  the  mixture,  preference  is  given 
either  to  a  mixture  of  lead  peroxide  and  potassium  nitrate,  or  to  a  mixture  of  the 
former  with  lead  nitrate  obtained  by  treating  red  lead  with  a  small  quantity  of  nitric 
acid  and  leaving  this  mixture  for  a  period  of  several  weeks  to  dry.  Glue,  gum,  and 
dextrine  are  used  as  excipients  ;  the  first,  however,  is  objectionable  because  it  carbon- 
ises and  prevents  the  combustion.  Perhaps  a  dilute  collodion  solution  or  a  mixture  of 
sandarac  or  similar  resin,  with  benzole,  might  be  used  as  an  excipient  instead  of  the  gum. 

The  mixtures  actually  used  in  the  trade  are  kept  secret,  but  the  following  recipes 
may  give  some  idea  of  the  composition  : — 


Phosphorus     .        ,  •      . 
Gum  Senegal  .         . 
Lamp-black    ,         . 

Red  lead         .        .        . 
Nitric  acid,  sp.  gr.  i  '384 

Phosphorus     .  .        . 

Glue      ..        .  .        . 
Lead  peroxide 

Potassium  nitrate  . 

Phosphorus  . 
Gum  Senegal  . 
Lead  peroxide 
Fine  sand  and  smalt 


I  -5  parts 


II. 


8'O  part? 
21 'O      „ 

24 '4      „ 
24 -o      ,, 


A  mixture  of  lead  ni- 
trate and  peroxide, 
technically  known  as 
oxidised  red  lead. 

Dissolved  in  the  required 
quantity  of  carbon  di- 
snlphide. 


111. 


3  'o  parts 
3-0      „ 

2'0        „ 
2'O 


No  doubt  there  is  room  for  great  improvements  in  these  compositions. 

3.  Dipping  and  Drying  the  Splints. — In  order  to  fix  the  sulphur  and  combustible 
composition  to  one  end  of  the  splints,  it  is  clear  that  these  should  not  touch  each  other, 
but  be  so  arranged  as  to  leave  an  intermediate  space.  A  contrivance  is  employed, 
consisting  of  small  planks,  0*3  metre  long  by  10  centimetres  wide,  the  surface  being 
provided  with  narrow  grooves  placed  both  together,  and  just  large  enough  each  to 
hold  a  single  splint,  Fig.  359.  The  splints  are  one  by  one  placed  in  the  grooves,  an 
operation  usually  performed  by  girls.  One  plank  having  been  filled  another  is  placed 

Fig.  359- 


Fig.  360. 


Fig.  361. 


on  the  top  of  it.  The  surface  of  the  plank  on  one  side  is  provided  with  a  piece  of 
coarse  flannel,  while  the  other  side  is  grooved  for  holding  splints.  Each  of  the  planks 
has  at  the  end  a  round  hole,  through  which  pass  iron  rods,  Figs.  360  and  361,  in  the 


422 


CHEMICAL  TECHNOLOGY. 


[SECT. 


top  of  which  a  screw  thread  is  cut,  so  that  as  soon  as  some  twenty  to  twenty-five 
planks  have  been  filled  with  splints  and  placed  one  upon  another,  they  are  fastened  so 
as  to  form  a  framework.  A  clever  hand  can  fill  during  ten  hours  fifteen  to  twenty-five 
of  these  frames,  each  containing  2500  splints.  Attempts  have  lately  been  made  to  per- 
form this  work  by  machinery,  and  the  machine  constructed  by  0.  Walsh,  at  Paris 
(1861),  enables  a  lad  to  frame  500,000  to  600,000  splints  in  ten  hours. 

The  sulphur  intended  for  dipping  the  splints  is  kept  in  a  molten  state  over  a  mode- 
rate fire  in  a  shallow  rectangular  trough,  in  the  middle  of  which  a  stone  is  placed  as 
precisely  level  as  possible.  The  quantity  of  sulphur  is  so  regulated  that  it  covers  the 
stone  to  a  depth  of  i  centimetre.  In  the  operation  of  dipping,  the  ends  of  the  splints 
are  made  to  just  touch  the  stone  and  immediately  removed,  care  being  taken  to  cause,, 
by  shaking  the  frame,  any  superfluous  sulphur  to  flow  into  the  trough  again. 

In  the  dipping  apparatus  of  Roller  the  mixture  is  in  the  cast-iron  pan,  a  (Figs.  362, 
363,  and  364).  In  its  middle  there  is  a  dipping  plate,  b,  in  two  ribs,  c,  upon  which  the 
ignition  mass  is  spread  in  the  usual  manner.  Into  this  stratum  of  uniform,  thick- 
ness the  woods,  previously  fixed  in  the  frame,  z,  are  dipped  with  the  end  to  be  coated. 
In  order  to  dip  all  the  splints  equally  deep,  even  if  they  have  been  laid  unevenly,  the 


Fig.  362. 


Fig.  363- 


press  plate,/,  is  held  by  its  handle,  g,  and  rolled  over  the  filled  frame.  The  weight  off 
pushes  down  any  splints  which  stand  up  above  the  level  and  presses  all  down  to  the 
planed  surface  of  the  dipping  plate,  b.  For  guiding  the  press  plate,  /,  there  serve  the 
two  counter-guides,  h,  which  turn  on  the  pivot,  i,  and  the  joint,  k,  in  a  curve  approaching 
to  a  cycloid. 

When  at  rest  the  press  plate,  /,  stands  perpendicularly  behind  the  dipping  table, 
whilst  the  counter-guides,  h,  come  in  contact  with  the  angles,  m,  the  press  plate,/,  turns 
on  the  connecting  bolt,  /,  and  the  pieces,  n,  are  supported  against  the  side  of  the  pan. 
The  hollow  space,  o,  of  the  dipping  pan,  closed  below  by  the  foot,  serves  for  warming  the 
ignition  mass,  if  needful,  by  hot  water,  steam,  or  hot  air.  The  funnel,  p,  serves  for 
introducing  hot  water  or  letting  off  that  which  has  become  cold  through  the  cock,  r. 

Inodorous  matches,  when  dry,  are  coated  with  a  coloured  solution  of  resin,  or  some- 
times finally  with  collodion.  Phosphorus  is  recovered  from  matches  which  adhere 
together  by  boiling  in  water. 

Matches  with  Amorphous  Phosphorus. — This  variety  of  match  was  invented  in  1848 
by  Bottger,  at  Frankfort,  and  was  prepared  industrially  by  Furth,  at  Schiittenhofen ; 
Lundstrom,  at  Jonkoping  (Sweden) ;  Coignet,  at  Paris  "(under  the  name  of  Allumettes 
hygieniques  et  de  surete  au  phosphore  amorphe) ;  De  Villiers  and  Dalernagne,  Paris 
(under  the  name  of  Allumettes  androgynes) ;  also  by  Fcirster  and  Wara.  These  matches 
are  of  two  kinds  :  (a)  Those  which  are  free  from  phosphorus,  the  amorphous  phosphorus 
being  incorporated  with  the  sand-paper ;  (0)  Those  which  are  free  from  phosphorus 
both  in  the  match  and  on  the  sand-paper. 


SECT,  m.]  MATCHES:   PRODUCTION  OF  FIKE.  423 

To  the  matches  of  the  first  category  belong :  (i)  Matches  the  composition  of  which 
is  free  from  phosphorus,  consisting  simply  of  a  pasty  mass,  the  main  constituents  of  which 
are  antimony  sulphide  and  potassium  chlorate.  (2)  The  amorphous  phosphorus,  mixed 
with  some  very  fine  sand  or  other  substance  promoting  friction,  is,  with  glue,  put  on  to 
the  box  in  which  the  matches  are  contained  ;  or,  as  is  the  case  with  the  androgynes,  at 
the  other  end  of  the  splint.  The  friction  surface  on  the  boxes  consists  of  a  mixture  of 
9  parts  of  amorphous  phosphorus,  7  parts  of  pulverised  pyrites,  3  parts  of  glass,  and 
i  part  of  glue.  The  matches  ignite  readily  by  friction  on  the  surface  containing  this 
composition,  but  do  not  ignite  when  rubbed  on  any  other  rough  surface.  These  so- 
called  safety  matches  are  largely  manufactured  at  Jonkoping,  under  the  Swedish  name 
of  Sakerhets-Tdndstickur  (security  fire  matches).  Jettel  (1870)  uses  for  the  friction 
surface  a  compound  consisting  of  equal  parts  of  amorphous  phosphorus,  pyrites,  and 
black  antimony  sulphide;  for  coating  on  the  two  sides  of  1000  small  boxes,  each  con- 
taining fifty  matches,  about  80  grammes  of  this  mixture  are  required.  It  need 
hardly  be  mentioned  that  in  England  safety  matches  are  largely  made  and  of  excellent 
quality. 

B.  Forster  and  F.  Wara,  at  Vienna,  have  introduced  a  "  non-poisonous  "  match. 
The  amorphous  phosphorus  is  mixed  up  with  the  combustible  composition  in  the 
usual  way,  so  that  these  matches  ignite  readily  by  being  rubbed  on  any  rough  surface, 
but  the  ignition  is  accompanied  by  noise,  owing  to  the  potassium  chlorate  contained  in 
the  mass. 

As  regards  the  matches  belonging  to  the  second  category — viz.,  such  as  neither 
contain  phosphorus  nor  require  a  phosphorus-containing  surface,  we  may  give  the 
analysis,  by  Wiederhold,  of  the  composition  of  those  made  by  Kummer  and  Glinther,  at 
Konigswalde,  near  Annaberg,  in  Saxony : 

Potassium  chlorate 8  parts 

Black  antimony  sulphide         .        .        .        .  8      „ 

Oxidised  red  lead 8      „ 

Gum  Senegal I      „ 

Oxidised  red  lead  is  a  variable  mixture  of  lead  peroxide,  nitrate,  and  undecomposed 
red  lead.  Wiederhold,  at  Cassel,  suggested  (1861)  the  following  ignition  mixture : — 

Potassium  chlorate 7 '8  parts 

Lead  hyposulphite 2'6      „ 

Gum  arabic i  'o      „ 

This  is  the  best  anti-phosphorus  mixture.  Jettel,  at  Gleiwitz,  gives  the  following 
mixtures  free  from  phosphorus  : — 

a.  6.  e.  d. 

Potassium  chlorate       .        .        .    4*0  ...  7*0  ...        3*00        ...        8*0 

Sulphur I'O  ...  i'o  ...          —          ...          — 

Potassium  bichromate .        .        .0*4  ...  2*0  ...                       ...        0*5 

Antimony  sulphide       ...      —  ...  —  ...                       ...        8'Q 

Sulphur  auratum,  SbS3  (Stibium  } 

sulphuratum  aurantiacum)          -    —  ...  —  ...        0*25 
(Antirnonium  sulphuratum,  B.P.)J 

Lead  nitrate         ....      —  ...  2*0  ...                      ...         — 

While  R.  Peltzer  has  called  attention  to  the  applicability  of  copper-sodium  hypo- 
sulphite for  the  preparation  of  a  phosphorus-free  ignition  mass,  Fleck*  has  also 
remarked  the  use  which  might  be  made  of  sodium  in  this  respect. 

Wax  or  Vesta  Matches. — Instead  of  the  phosphorus  composition  being  fixed  to  a 
wooden  splint,  in  the  wax  matches  (allumettes  bougies)  it  is  attached  to  a  thin  taper 
made  of  a  few  cotton  threads  (four  to  six)  immersed  in  a  molten  mixture  of  2  parts  of 

*  Jahreslericht  der  Chem.  Techndogie  (Dr.  Wagner),  1868,  p.  220. 


424  CHEMICAL  TECHNOLOGY.  [SECT.  HI. 

stearine  and  i  part  of  wax  or  paraffine.  The  tapers,  while  this  mixture  is  hot,  are 
drawn  through  a  hole  perforated  in  an  iron  plate,  the  opening  of  which  corresponds  to 
the  desired  thickness  of  the  taper.  The  taper  is  next  cut,  by  means  of  machinery,  into 
suitable  lengths ;  afterwards  the  phosphorus  composition  is  affixed  and  the  vestas  put 
into  boxes. 

Zulzer's  machine  for  cutting  the  tapers  and  for  making  them  into  matches  has  the 
following  arrangement: — The  wicks,  having  been  rolled  on  a  drum,  are  forced  between 
two  cylinders,  which  impart  the  fatty  composition,  and  next  the  tapers  are  carried  by 
the  machinery  across  grooves  in  planks  to  holes  in  a  movable  vertical  iron  plate, 
which  is  connected  with  a  cutting  apparatus  intended  to  divide  the  tapers  into  suitable 
lengths.  As  the  cutters  are  placed  at  the  entrance  of  the  holes,  the  tapers,  after 
having  been  separated  from  the  main  wicks,  are  left  dangling  in  those  holes,  and,  by  a 
mechanical  contrivance,  the  plate  containing  the  holes  is  lifted  sufficiently  to  bring 
another  row  of  holes  level  with  the  wick-producing  apparatus.  When  a  plate  has 
been  thus  filled  with  tapers  it  is  removed,  another  put  in  its  place,  and  the  ends  of  the 
tapers  immediately  immersed  in  the  phosphorus  composition,  and  next  placed  in  a 
drying  room.  Marseilles  is  the  great  centre  of  the  wax-match  industry,  while  Austria 
stands  next. 

PHOSPHATES,  MANURES. 

Since  Liebig  demonstrated  the  importance  of  phosphoric  acid,  of  nitrogen  (as 
nitric  acid  and  ammonia),  and  of  potash  as  plant-food,  so-called  artificial  manures  have 
come  more  and  more  into  use  in  agriculture. 

Poudrette. — Repeated  attempts  have  been  made  to  bring  the  contents  of  cess- 
pools, <fcc.,  into  a  portable  condition.  But  as  the  cesspools  contain  in  the  mean  96  per 
cent,  of  water  and  only  0-35  per  cent,  of  nitrogen,  with  0*2  per  cent,  of  phosphoric 
acid,  the  attempt  seems  vain.  However,  a  manure  obtained  by  precipitating  sewage 
contains,  according  to  Tidy,  3  per  cent,  ammonia  and  5  per  cent,  tricalcium  phosphate 
derived  exclusively  from  the  sewage.  So  that  irrigation  is  not  the  only  method  of 
utilising  human  excreta,  though  in  dry,  hot  climates  it  may  be  the  best.* 

Guano. — On  certain  islands  off  the  Peruvian  coast  the  droppings  of  sea-fowl  had 
accumulated  to  a  depth  of  60  metres.     In  1853  the  quantity  of  these  deposits  was 
estimated  at  1 2  million  tons,  but  they  are  now  nearly  exhausted. 
Guano  contains : 

i.  n.  in. 

Sal-ammoniac 2*25  ...  6*500  ...  4-2 

Ammonium  urate        .        .        .        .     12*20  ...  3*244  ...  9-o 

oxalate     ....     1773  •••  I3'35i  —  io'6 

phosphate        .        .        .      6-90  ...  6*250  ...  6-o 

carbonate         .        .        .      0*80  ...  —  ...  — 

bromate  ....       1*06  ...  — 

magnesium  phosphate     .11-63  •••  4 ''96  ...  2 '6 

Sodium  phosphate      ....      —  ...  5*291  ...  — 

Calcium  phosphate     ....     20*16  ...  9'94O  ...  14*3 

„        oxalate 1*30  ...  16*360  ...  7-0 

„        carbonate      ....       1*65  ...  —  ...  — 

Sodium  chloride          ....      0*40  ...  0*100  ...  — 

Potassium  sulphate     ....      4*00  ...  4*227  ...  5*5 

Sodium  sulphate          ....      4*92  ...  1*119  •••  3'8 

Waxy  matter 0*75  ...  0*600 

Sand  and  clay 1*68  ...  5*904  ...  4*7 

Water 4'3"0 

Organic  matter 8*26J  *"  22*718 


ICO'OO  lOO'OOO  ICO'O 

Compare  Slater,  Sewage  Treatment,  1888. 


SECT,  in.]  PHOSPHATES,   MANURES.  425 

A  more  recent  analysis  gave : 

Per  cent. 

Ca3P2Og 31759    P./)s=i5-552percent. 

Mg2P207          ....      1-568 

MgS04 0-838 

CaSO4     ........  IQ.-II3 

CaCO, 1-612 

NaCl 7-238 

Fe203,  Al./)3  ....  0-598 
Insoluble  ....  3-840 

Water 16-175 

C5H3(NH4)N408  .  .  .  3-122 
NH4N03  ....  1-499 
(NH4).2C03  ....  2-823 

Organic  matter      .        .        .  13-815  =  2-513  N  =  3'O52  NH3 


100-000  =  5-075  total  N  =  6-i63  NH3 

Guano  from  Mejillones  contains  about  70  per  cent,  tricalcium  phosphate  and  only 
o'3  to  o'8  per  cent,  nitrogen.  Guano  from  the  Aves  Islands,  on  the  coast  of  Venezuela, 
contains  45  to  50  per  cent,  of  phosphate  and  0-3  to  0*4  per  cent,  nitrogen.  Guano 
from  Sydney  Island  contains  34  per  cent,  phosphoric  acid  and  0-28  per  cent, 
nitrogen;  that  from  Cape  Verde,  n  per  cent,  phosphoric  acid  and  0-3  nitrogen. 

Guano  is  used  powdered  and  sifted,  but  generally  rendered  soluble  by  admixture 
with  sulphuric  acid  (chamber  acid)  to  get  the  phosphoric  acid  into  solution.  The 
pasty  mass  solidifies  on  cooling  from  the  formation  of  gypsum,  and  is  therefore  again 
pulverised  and  sifted. 

Bone  Meal. — The  bones  are  deprived  of  fatty  matter  and  ground  finely.  Various 
samples  of  bone  meal  had  the  following  compositions : 

I.                    n.  in. 

Bone  earth 63-3  ...        60-7  ...  47-7 

(Containing  phosphoric  acid)     .        .  25-5  ...        25-4  ...  2o-o 

Organic  matter 29-7  ...         31-8  ...  42-5 

Nitrogen 3-9                     3-5  ...  4-7 

Water 3-9                      5-0  ...  7-4 

Sand 3-1  ...          2-5  ...  2-4 

Precipitated  Tricalcium  Phosphate  can  scarcely  be  produced  to  advantage  at  the 
present  prices  for  hydrochloric  acid. 

Superphosphate. — To  render  soluble  the  phosphoric  acid  present  in  natural  phos- 
phates, they  are  mixed  with  sulphuric  acid — 

Ca3(P04)2    +    2H2S04    =    2CaS04    +    CaH4(P04)3.» 

Monocalcium  phosphate  is  freely  soluble  in  water,  whilst  tricalcium  phosphate, 
Ca3P208,  is  sparingly  soluble. 

The  most  important  materials  for  the  manufacture  of  superphosphate  are  the 
phosphorites.  That  occurring  in  large  masses  in  Estremadura  is  nearly  pure  phos- 
phate, but  large  quantities  are  met  with  in  commerce  which  contain  only  60  per  cent, 
along  with  considerable  quantities  of  silica  and  calcium  chloride,  f  Of  less  value  are  the 
staffelites  from  the  valley  of  the  Lahn. 

The  Canadian  phosphorite  contains : 

Tricalcium  phosphate 91-20 

Calcium  fluoride 7-60 

„       chloride 0-78 

Sand 0-90 


100-58 

*  Compare  Griffith  :  Treatise  on  Manures,  p.  146. 
f  And  occasionally  calcium  fluorides. 


426  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

South  Carolina  phosphate  contains  : 

Moisture 779 

Organic  matter 4-60 

Silica io-35 

Calcium  carbonate       .        .        .        .        .        .  8*20 

Tricalcium  phosphate 6i'89 

Earthy  and  alkaline  salts 7-17 


1 00 'GO 

Coprolites,  the  fossil  excrements  of  saurians,  are  found  in  the  lias   at  Norfolk, 
Suffolk,  Cambridgeshire,  &c.,  in  England,  and  near  Helmstadt,  in  Germany. 
A  sample  of  Cambridge  coprolites  contained : 

Moisture O'I2 

Organic  matter  and  combined  water  .         .        .  5-61 

Silica O'i8 

Carbon  dioxide 6-50 

Phosphoric  acid 30-2 1 

Lime     .........  49*01 

Fluorine 3-08 

Alkaline  salts 5-29 

100-00 

In  general  the  proportion  of  phosphate  in  coprolites  varies  from  15  to  70  per  cent.,* 
so  that  they  must  be  examined  before  being  used  for  superphosphate.  The  spent 
animal  charcoal  from  sugar  works  is  of  less  value. 

The  materials  are  finely  ground  and  mixed  with  the  requisite  quantity  of  sulphuric 
acid  in  pits  provided  with  agitators.  The  mixture  Is  rendered  dry  by  the  combination 
of  the  calcium  sulphate  with  water  (CaSO4.2H20),  and  is  then  broken  up. 

Double  superphosphate  is  made  by  separating  the  gypsum  from  the  soluble  phos- 
phate, when  the  solution  of  the  latter  is  evaporated. 

The  so-called  reversion  of  superphosphates  (i.e.,  their  return  to  an  insoluble  form) 
is  occasioned  partly  by  the  formation  or  presence  of  aluminium  or  ferric  phosphates, 
and  partly  by  the  action  of  calcium  carbonate.  Superphosphates  made  from  the  Lahn 
phosphorites  are  peculiarly  liable  to  this  change.! 

From  a  double  superphosphate,  I.,  the  quantities  given  under  II.  were  dissolved 
out  by  lixiviation  with  small  quantities  of  water  in  a  filter,  and  those  under  III.  by 
immediate  treatment  with  much  water. 

i.  n.  in. 

PA          •        •        •     49'9Q  ...  47'20  ...  45-80 

S03    .  .  .  .          I'2O  ...  I '2O  ...  I -2O 

SiO2  .  .  .  0-50  ...  ...  — 

CaO  .  .  .  17-24  ...  15-20            ...  1470 

MgO  .  .  .  1-15  ...  1-12            ...  i-ri 

Fe,0,  .  .  .  2-87  ...  1-32            ...  0-66 

A120S  .  .  .1-38  ...  1-33  ...  1-38 

Na,jO  .  .  .  0*40  ...  0*40            ...  0*40 

Water  .  .  .  23-52  ...  ...  — 

Organic  .  .  1-53 

An  immediate  great  dilution  dissolves  out  1-4  per  cent,  less  phosphoric  acid  than 
does  gradual  lixiviation. 

*  Fragments  of  wood  have  been  found  among  coprolites  as  rich  in  phosphoric  acid  as  the 
animal  remains. 

t  The  author  thinks  that  the  preference  given  to  soluble  phosphates  is  an  error  which  has  cost 
Germany  200,000,000  marks.  Foreign  phosphorites  have  been  imported  and  the  Lahn  phosphorites 
exported  at  very  low  prices. 


SECT,  in.]  BORIC  ACID  AND   BOKAX.  427 

As  nitrogenous  manures,  in  addition  to  guano  and  bone-dust,  there  are  ammonium 
sulphate,  nitre,  dried  blood,  horn-dust,  and  shoddy.  Of  sources  of  potash  the  chief  are 
kainite  and  potassium  chloride. 

For  determining  nitrogen  in  ammonium  sulphate  the  ammonia  is  driven  off  into 
normal  acid  by  boiling  with  soda-lye.  Saltpetres  are  examined  by  means  of  the  nitro- 
meter. Organic  nitrogen  and  total  nitrogen  in  mixed  manures  are  best  determined  by 
the  Kjeldahl  process.  The  sample  is  boiled  with  strong  sulphuric  acid,  to  which  phenol 
is  added  if  a  nitrate  is  present.  All  the  nitrogen  is  thus  converted  into  ammonia, 
which  is  distilled  off. 

For  determining  the  soluble  phosphoric  acid  the  following  procedure  was  agreed 
upon  at  a  meeting  of  agricultural  chemists  held  on  November  30,  1885  : — 

Five  grammes  of  the  sample  are  rubbed  up  with  the  strong  citrate  solution  and 
gradually  washed  into  a  ^-litre  flask.  The  mixture  is  filled  up  to  the  mark  with  the 
dilute  solution  of  citrate,  let  stand  for  eighteen  hours  at  the  temperature  of  the  room 
with  frequent  shaking,  and  filtered.  50  c.c.  of  the  filtrate  are  mixed  with  so  much 
molybdenum  solution  that  not  less  than  i  c.c.  of  the  solution  may  come  to  each  milli- 
gramme P2O5,  and  so  much  strong  ammonium  nitrate  (see  below)  is  added  as  is  equal 
to  a  quarter  the  volume  of  the  mixture.  After  standing  twenty  minutes  in  the  water- 
bath  and  subsequent  cooling,  the  liquid  is  filtered,  the  precipitate  washed  with  dilute 
ammonium  nitrate  (see  below),  and  rinsed  back  into  the  beaker  with  ammonia  at  2^5  per 
cent,  through  the  perforated  filter.  The  filter  is  well  washed,  and  to  the  ammoniacal 
solution  magnesia  mixture  is  added  drop  by  drop,  with  constant  stirring.  The  whole 
is  filtered  after  one  hour,  the  precipitate  is  washed  with  ammonia  at  2  per  cent.,  dried, 
and  ignited. 

Preparation  of  the  Solutions. — (i)  Strong  solution  of  citrate.  150  grammes  citric  acid 
are  put  in  a  i  -litre  bottle,  dissolved  in  water,  and  neutralised  with  ammonia.  To  the  solu- 
tion are  added  10  grammes  citric  acid,  and  the  liquid  is  filled  up  to  the  mark  with  water. 

(2)  Dilute  solution  of  citrate,     i  volume  of  the  foregoing  strong  solution  is  mixed 
with  4  volumes  water. 

(3)  Strong  solution  ammonium  nitrate.      750  grammes  ammonium  nitrate  are  dis- 
solved in  water,  and  the  solution  is  diluted  to  i  litre. 

(4)  Dilute  ammonium  nitrate.     100  grammes  ammonium  nitrate  are  dissolved  in 
water,  and  the  solution  is  made  up  to  i  litre. 

(5)  Molybdic  solution.     150  grammes  ammonium  molybdate  are  dissolved  in  water, 
the  solution  is  diluted  to  i  litre,  and  poured  into  i  litre  nitric  acid  of  sp.  gr.  1-2. 

(6)  Magnesia  mixture,     no  grammes  pure  crystalline  magnesium  chloride  and  140 
grammes  ammonium  chloride  are  dissolved  in  700  c.c.  liquid  ammonia  (at  8  per  cent, 
actual  ammonia)  and  1300  c.c.  of  water. 

BORIC   ACID  AND  BOEAX. 

Boric  acid  occurs  native  as  sassoline,  H3B03 ;  in  100  parts- 
Anhydrous  boric  acid,  B2OS        .        .        .        .56*45 
Water •     43'55 

lOO'OO 

and  further  in  the  following  minerals : — 

Boracite,  or  magnesium  borate  and  chloride  with  62  '5  per  cent,  boric  acid 

Rhodicite,  or  calcium  borate      .         .         .  ,,  30  to  45 

Hayescine,  tiza,  or  calcium  borate     .         .  ,,  30  to  44 

Hydroboracite   .        .        .         .         »        .  „  47 

Tincal  or  borax,  sodium  borate  .         .  „  36*53 

Datholite,  or  boro-silicate .        .         .         .  ,,  18 

Botryolite „  2O'35 

Axiiiite ,,  2  to  6'6 

Tourmaline  2  to  1 1  '8 


428  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Boric  acid  is  found  also  in  small  quantities  in  many  mineral  waters  and  in  sea- 
water.  Larderellite,  or  ammonium  borate,  and  lagonite,  or  iron  borate,  are  both 
found  in  very  small  quantities  in  Tuscany,  and  are  interesting  to  mineralogists  only. 

Boric  acid  is  found  as  sassolin  in  many  volcanic  regions,  mixed  with  sulphur,  in 
the  hot  springs  of  Sasso,  in  Tuscany,  and  also  between  Volterra  and  Massa  Maritima 
in  the  clefts  and  rents  of  volcanic  formation  of  rock.  H offer  and  Mascagui  (1776) 
first  mentioned  the  occurrence  of  boric  acid  in  the  waters  subjected,  in  the  clefts 
of  the  rock,  to  the  sulphurous  exhalations.  The  little  pools  formed  in  these  clefts 
are  variously  known  as  fumacchi,  fumarole,  soffioni,  and  mofetti.  The  boric  acid 
deposits  in  some  cases  cover  an  extent  of  six  miles.  Since  1818  artificial  soffioni  have 
been  constructed,  and  the  benefit  derived  by  the  country  from  the  introduction  of  the 
industry  is  immense.  The  first  artificial  lake  was  situated  near  Monte  Cerboli,  and  the 
product  was  for  some  time  known  as  larderellite,  from  the  owner's  name,  Larderel.  The 
production  from  these  works  alone  amounted  in  1839  to  7X7>333  kilos.,  and  in  1867  to 
2,350,000  kilos.  The  increase  has  been  greatest  since  1854,  owing  to  the  energy  with 
which  Gazzeri  and  Durval  entered  upon  the  construction  of  the  artificial  soffioni. 

The  soil  of  the  natural  lakes,  or  beds  of  the  natural  soffioni,  are  of  a  slimy  for- 
mation, and  have  a  peculiar  seething  movement  due  to  the  escape  of  the  sulphurous 
vapours  from  the  fumaroles  or  vents.  According  to  Payen,  this  vapour  or  steam  may 
be  considered  as  condensible  and  as  non-condensible,  the  former  containing,  besides 
water,  calcium,  magnesium,  and  ammonium  sulphate,  iron  chloride,  hydrochloric  acid, 
organic  substances,  a  fishy-smelling  oil,  clay,  sand,  and  a  small  quantity  of  boric  acid. 
The  non-condensed  vapour  consisted  of — 

Carbonic  acid     .....  0-5730 

Nitrogen    .        '.        .         .        .         .  0-3480 

Ox}?gen 0-0657 

Sulphuretted  hydrogen       .         .         .  0-0133 

Payen  is  of  opinion  that  the  vapours  contain  no  boric  acid,  while  C.  Schmidt 
thinks  otherwise,  as  the  vapours,  when  condensed  without  contact  with  the  water  of 
the  soffioni,  yield  boric  acid.  The  condensed  vapours  contain  0*1  per  cent,  boric 
acid. 

Theory  of  the  Formation  of  the  Native  Boric  Acid. — Dumas  and  Payen  founded  a,n 
explanation  of  the  formation  of  volcanic  boric  acid  upon  the  hypothesis  that 
there  exists  in  the  interior  of  the  volcano  or  beneath  the  under-crust  of  the 
earth  a  layer  of  boron  sulphide  (B2S3),  which  under  the  action  of  the  mineral  waters 
becomes  converted  into  boric  acid  and  sulphuretted  hydrogen.  P.  Bolley  gives  the 
action  as  similar  to  that  occurring  in  the  formation  of  sal-ammoniac,  a  very  common 
mineral  in  volcanic  regions.  Professor  Becchi,  of  Florence,  found  boron  nitride  (BN) 
in  one  of  the  under-strata,  from  which  he  prepared  artificially,  by  means  of  steam, 
ammonia  and  boric  acid.  Also  "VVarington  (1854)  and  Popp  (1870)  attributed  the 
appearance  of  boric  acid  and  ammonia  in  volcanoes  to  the  decomposition  of  boron 
nitride  by  evaporation.  Recently  (1862)  Becchi  has  obtained  boric  acid  by  the  de- 
composition of  calcium  borate  in  a  stream  of  superheated  steam. 

TJie  Production  of  Boric  Acid. — The  most  general  method  of  obtaining  boric  acid 
is  by  the  evaporation  of  the  water  of  the  natural  or  artificial  soffioni.  The  water  is 
either  naturally  or  artificially  introduced  into  the  natural  fumaroles,  as  these  sometimes 
do  not  re-supply  themselves  with  sufficient  rapidity.  As  soon  as  the  water  has  absorbed 
a  considerable  quantity  of  the  vapours  it  is  removed  and  placed  in  a  large  mason-work 
cistern ;  this  cistern  is  imbedded  in  the  soil  near  the  fumaroles,  and  the  natural  heat 
is  sufficient  to  cause  evaporation.  The  vapours  are  condensed  in  a  wooden  chimney 
The  separated  impurities,  gypsum,  &c.,  remain  in  the  cistern.  As  soon  as  the  solution 
is  of  a  sp.  gr.  =  1-07  —  ro8  at  80°,  it  is  poured  into  leaden  crystallising  vessels,  where 


SECT.    III.] 


BOEIC   ACID  AND  BORAX. 


429 


the  boric  acid  crystallises  out.  The  mother  liquor  is  evaporated  to  dryness.  It 
should  be  remembered  that  the  entire  operation  is  conducted  with  the  assistance  of  the 
natural  heat  of  fumaroles  only.  Occasionally  the  boric  acid  is  only  present  in  the 
natural  waters  to  0*002  of  a  part  ;  and  in  these  cases  fuel  must  be  used  in  the  evapo- 
ration, which  therefore  entails  the  expense  of  carriage,  as  fuel  is  very  scarce  near  the 
soffioni.  Charcoal  is  generally  used.  But  by  this  means  an  acid  is  obtained,  containing 
about  70  to  80  per  cent,  hydrated  boric  acid,  with  10  per  cent,  impurities.  Clouet 
removes  the  impurities  by  treatment  with  5  per  cent,  of  ordinary  hydrochloric  acid. 
Boric  acid  for  pharmaceutical  purposes  may  be  prepar/ed  by  dissolving  i  part  of  borax 
in  4  parts  of  boiling  water,  and  decomposing  the  solution  with  one-third  part  of 
sulphuric,  or  better  with  one-half  part  of  hydrochloric  acid  of  1*2  sp.  gr.  The  acid 
separates  on  cooling,  and  can  be  purified  by  crystallisation. 

In  100  parts  of  commercial  boric  acid  from  Tuscany,  H.  Yohl  (1866)  found : 


Boric  acid       . 

•  45  '1996 

...   47-6320   ... 

48-2357 

...     45-2487 

...     48-1314 

Water  of  crystallisation 

.  34-8916 

...   35-6983   ... 

37-2127 

...     34-9010 

...     38-0610 

Water     .... 

•     4-5019 

...     2-5860    ... 

I  -0237 

...       4-4990 

...       1-5240 

Sulphuric  acid 

•     9-6I3S 

...     7-9096   ... 

8-4423 

-       9-5833 

...       7-8161 

Silicic  acid 

.       O'8l2I 

1-2840    ... 

0-6000 

0-2134 

0-0861 

Sand        .... 

.     0-2991 

0-5000     ... 

0-1000 

...       0-7722 

...      0-4154 

Iron  oxide 

.    0-1266 

0-1631     ... 

O-O92O 

0-1030 

0-0431 

Manganous  oxide    .         . 

.     0*0031 

traces     ... 

traces 

traces 

traces 

Alumina           .         .         . 

.    0-5786 

0-0802     ... 

0-0504 

•••       0-1359 

...       0-1736 

Lime       .... 

.     0-0109 

...       0-3055     ... 

0-1578 

traces 

traces 

Magnesia        .         . 

.     0-6080 

traces 

traces 

traces 

traces 

Potash    .... 

O  "2  "-  "i,  I 

0-1:178 

0*6140 

OMTIyl 

Ammonia 

.     2-9891 

...                 W    *»33  *             ... 
...                 3-5I65            ... 

w  j  i  /  *-* 
3-5i69 

...       3-7659 

<j  i\  i  ^q. 
3-0890 

Soda       .... 

.     0-0029 

traces     ... 

traces 

traces 

traces 

Sodium  chloride 

.      O-IOI2 

...       0-0595     ... 

0-0401 

0-1671 

0-0321 

Organic  substances  and  loss 

.    0-0918 

O'OIOI 

O'OIOI 

— 

0-0449 

lOO'COOO 


Properties  and  Uses  of  Boric  Acid. — Pure  boric  acid  crystallises  in  mother-of- 
pearl-like  leaves,  which  at  100°  C.  lose  half  their  water  of  crystallisation  without 
melting,  the  other  half  being  driven  off  at  a  red-heat.  After  cooling,  the  anhydrous 
acid  appears  as  a  hard,  transparent,  brittle  glass  of  1-83  sp.  gr.  i  part  boric  acid 
dissolves  in  25*6  parts  water  at  15°  C.,  and  in  2-9  parts  at  100°  C.  At  8°  a  saturated 
solution  has  a  sp.  gr.  of  1*014.  I*  imparts  a  green  colour  to  the  flame  of  the  spirit- 
lasip.  In  a  chemical  point  of  view  it  is  similar  to  silicic  acid.  Boric  acid  is  largely 
used  in  the  preparation  of  borax  for  glazing  porcelain,  and,  mixed  in  a  weak  aqueous 
solution  with  sulphuric  acid,  in  the  preparation  of  the  wicks  of  stearine  and  paraffine 
candles.  It  is  also  used  for  colouring  gold,  for  decorating  iron  and  steel,  in  the 
preparation  of  flint-glass,  and  artificial  precious  stones.  In  1859  boric  acid  was 
used  in  the  preparation  of  hydrated  oxide  of  chromium,  known  under  the  name  of 
Pannetier's  green,  Vert-Guignet,  &c. 

Borax. — Borax,  or  sodium  biborate,  when  anhydrous  according  to  the  formula 
Na2B407,  contains  in  i  oo  parts : 


Anhydrous  boric  acid  (B20.t) 


69-05 
30-95 


It  is  found  native  in  Alpine  lakes,  on  the  snow-capped  mountains  of  India,  China, 
Persia,  in  Ceylon,  and  Great  Thibet.  It  is  found  in  large  quantity  at  Potosi  in 
Bolivia,  where  the  Borax  Lake,  according  to  Moore's  analysis  (1870),  contains  in  i  litre 


43o  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

of  its  water  (sp.  gr.  =  1-027)  3'9^  grammes  of  borax.  Pyramid  Lake,  Humboldt  Co., 
Nevada,  yields  also  large  quantities.  By  the  heat  of  the  sun  the  water  of  the  borax 
lakes  is  evaporated,  and  the  borax  crystallises  out  and  is  gathered  and  brought  into 
commerce  under  the  name  of  tincal.  It  appears  in  small  six-sided  crystals,  more  or 
less  smooth.  The  Clear  Lake  in  California,  to  the  north  of  San  Francisco,  yields  daily 
2000  kilos,  of  borax. 

Formerly  tincal  was  purified  by  washing  in  water  containing  soda,  to  free  the 
borax  from  adhering  fatty  substances  which  combine  with  the  soda  to  form  an  almost 
insoluble  soap.  After  the  borax  has  been  well  washed,  it  is  dissolved  in  boiling  water ; 
for  each  100  parts  of  refined  salts  there  are  added  12  parts  of  sodium  carbonate.  The 
solution  is  next  filtered,  and  then  evaporated  to  26°  to  30°  Tw.  It  is  now  placed  in 
wooden  crystallising  vessels  lined  with  lead,  where  it  is  necessary  to  allow  the  fluid  to 
cool  gradually.  Another  method  is  to  place  the  tincal  in  cold  water,  and  to  stir  in 
i  per  cent,  of  caustic  lime.  The  fatty  substances  are  thus  removed,  combining  with 
the  lime  to  form  an  insoluble  calcium  soap.  2  per  cent,  of  calcium  chloride  is  added  to 
the  fluid,  which  is  next  evaporated,  and  set-  aside  to  crystallise.  Clouet  recommends  the 
powdering  of  the  tincal,  which  is  next  mixed  with  10  per  cent,  sodium  nitrate,  and 
calcined  in  a  cast-iron  pan,  the  fatty  substances  being  thus  destroyed.  The  calcined 
mass  is  dissolved  in  water,  and  the  solution  evaporated  to  crystallisation. 

Borax  from  Boric  Acid. — In  1818  the  manufacture  of  borax  from  boric  acid 
was  commenced,  and  since  that  time  borax  has  sunk  to  three-fourths  it  former  price. 
Both  according  to  the  proportion  of  water  and  the  crystalline  form,  there  may  be  con- 
sidered two  varieties  of  borax — (i)  the  ordinary  or  prismatic  borax;  (2)  octahedral 
borax.  The  prismatic  borax  (Na2B407  +  ioH20)  contains  in  100  parts : 

Boric  acid     .  ...  ' 36-6 

Soda     .        .        .        . i6-2 

Water  of  crystallisation       .         .        .        .         .      47-2 


ICO'O 


The  octahedral  borax  (Na2B407  +  5H20)  contains  in  100  parts  : 


Boric  acid) 

Soda          }  .....        •        ' 

Water  .        .......     30-64 


Prismatic  borax  is  manufactured  in  the  following  manner  : — There  are  dissolved  in  a 
lead-lined  vessel,  A,  Fig.  365,  26  cwts.  of  crystallised  sodium  carbonate  in  about  1500 
litres  of  water,  heated,  by  means  of  steam,  to  the  boiling-point.  The  boiler,  C,  is  for 
the  purpose  only  of  generating  steam,  which  is  passed  by  the  pipe,  c,  and  the  rose,  m, 
into  A.  By  means  of  the  large  taps,  b  and  r,  the  fluid  may  be  removed  from  A. 
Through  the  tube,  a,  the  substances  thrown  down  from  the  solution  can  be  removed. 
Boric  acid  is  added  in  quantities  of  8  to  10  Ibs.  after  the  solution  has  been  heated  to 
the  boiling-point.  Besides  carbonic  acid  a  small  quantity  of  ammonium  carbonate  is 
developed,  and  passes  by  o  into  the  vessel  D,  containing  dilute  sulphuric  acid,  by  which 
it  is  absorbed.  To  saturate  the  solution  of  26  cwts.  of  soda,  24  cwts.  of  crude  boric 
acid  are  necessary.  The  boiling  saturated  solution  marks  32°  to  33°  Tw.,  and  has  a 
temperature  of  104°.  If  the  solution  is  too  strong,  water  is  added ;  if  too  weak,  a  small 
quantity  of  crude  borax,  to  bring  it  to  32°  Tw.  The  solution  is  allowed  to  stand  in  A 
until  all  insoluble  substances  are  deposited.  The  clear  lye  is  conducted  by  means  of 
the  tap,  r,  into  the  crystallising  vessels,  P,  P,  the  mud  or  deposit  being  received  into  K. 
The  crystallising  vessels  are  of  wood  lined  with  lead.  The  crystallisation  is  complete 
in  two  to  three  days,  and  the  mother  liquor  is  drawn  off  into  the  vessel  H.  The 


SECT.  III.] 


BORIC   ACID  AND  BOKAX. 


431 


crystals  are  placed  to  drain  on  the  inclined  plane,  M.  The  mother  liquor  is  retained  for 
the  solution  of  a  fresh  quantity  of  soda.  After  three  or  four  operations,  the  mother 
liquor  contains  sufficient  sodium  sulphate  to  admit  of  profitable  crystallisation  ;  and  the 
lye  is  allowed  to  cool  at  30°.  As  the  solubility  of  sodium  sulphate  has  reached  the 


Fig.  366. 


maximum  at  a  temperature  of  33°,  it  is  clear  that  the  crystallisation  of  the  sulphate 
commences  at  the  completion  of  that  of  the  borax.  After  the  crystallisation  of  the 
sodium  sulphate,  the  mother  liquor  is  evaporated  to  dryness,  and  the  saline  residue  is 
sold  to  the  glass-manufacturer. 

Purifying  the  Borax. — The  cnide  borax  to  be  purified  is  placed  in  a  lead -lined 
wooden  cistern,  A,  Fig.  366,  heated  by  steam.  The  borax  is  suspended  in  a  wire  sieve 
immediately  under  the  surface  of  the 
water  with  which  A  is  filled.  To  100 
parts  of  borax,  5  parts  of  crystallised 
sodium  carbonate  are  added,  and  the  liquid 
is  strengthened  from  time  to  time  till  it 
marks  33'8°  T\v.  When  the  solution  has 
settled  it  is  removed  by  the  tap  to  the 
cooler,  B.  To  prevent  loss  of  lye,  the 
floor  under  B  is  stippled  with  waterproof 
cement,  and  sloped  towards  a  gutter. 
The  crystallising  vessel  is  of  thick  timbers, 
H,  F,  H,  lined  stoutly  with  lead  ;  this 


vessel  is  filled  with  lye  to  within  an  inch 
of  the  edge,  the  cover  being  then  placed  on. 
when  removed,  is  found  covered  with  small  crystals,  the  larger  crystals  falling  to  the 
bottom  of  the  vessel.  To  hasten  the  cooling,  spaces  are  left  in  the  timbers,  F  ;  but  the 
crystallisation  is  not  effected  under  sixteen  to  twenty-eight  days.  After  this  time  the 
lye  still  has  a  temperature  of  .27°  to  28°  C.  When  quite  cool  the  foreign  substances 
separate  from  the  borax.  The  vessel,  B,  contains  the  large  borax  crystals  from  which  the 
adhering  mother  liquor  is  separated  by  a  sponge.  If  the  crystals  are  not  thus  carefully 
treated,  they  split  into  thin  leaves ;  for  this  reason  also  the  cooling  should  be  gradual. 
The  crystals  are  dried  on  a  wooden  table,  finally  sorted,  and  packed. 


The  steam  condenses  on  the  cover,  which, 


432  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

In  England  borax  is  prepared  from  boric  acid  in  the  following  manner : — The 
crude  boric  acid  is  mixed  with  half  its  weight  of  calcined  soda  and  submitted  to  the 
action  of  heat  in  a  muffle-oven.  The  ammonia,  which  as  sulphate  is  an  important 
constituent  of  crude  boric  acid,  is,  with  carbonic  acid,  given  off  during  the  process, 
and  passes  through  a  tube  to  a  condensing  chamber.  The  melted  mass  is  removed,  and 
lixiviated  in  an  iron  pan  ;  the  suspended  matter  is  allowed  to  settle,  and  the  clear  liquor 
is  put  to  cool  into  smaller  vessels,  in  which  beautiful  crystals  form.  It  has  already  been 
mentioned  that  this  manufacture  had  its  origin  in  France,  where  sulphuric  vapours 
were  employed.  A  mixture  of  calcined  Glauber  salts  and  boric  acid  were  placed  in  a 
retort  and  subjected  to  distillation,  the  residue  on  lixiviation  and  crystallisation  yielding 
borax.  Kohnke  substitutes  caustic  soda  for  the  sodium  carbonate,  the  borax  crystal- 
lising from  a  very  alkaline  solution. 

Recently  borax  has  been  obtained  from  native  calcium  borate,  tiza,  ulexite,  frank- 
landite,  or  borocalcite  (formula,  according  to  Wohler,  Na2B407  +  2CaB407  +  i8H20  ;  or 
according  to  more  recent  determinations,  NaCaB5O9.8H20),  which  occurs  in  large 
quantities  in  California  and  Nevada,  in  Greece  and  Nova  Scotia,  at  Tarapaca  in  Peru, 
and  in  Western  Africa.  Treatment  with  sulphuric  acid  gives  only  unsatisfactory 
results,  and  hydrochloric  acid  is  therefore  employed.  The  acid  is  poured  upon  the 
mineral  to  two-thirds  of  its  weight  with  twice  the  quantity  of  water,  and  the  whole 
heated  to  the  boiling-point,  and  allowed  to  digest.  The  heat  must  be  maintained 
to  the  completion  of  the  digestion,  and  the  water  lost  by  evaporation  re-supplied.  The 
clear  liquor  is  then  decanted,  and,  on  cooling,  the  boracic  acid  crystallises  out,  the 
mother  liquor  retaining  sodium  or  calcium  chloride  with  a  slight  excess  of  hydro- 
chloric acid.  Stassfurt  boracite,  or  stassfurtite,  is  also  becoming  largely  used  in  the 
preparation  of  borax. 

Prismatic  borax  is  colourless,  and  forms  transparent  crystals  of  175  sp.  gr., 
soluble  in  1 2  parts  cold  and  2  parts  boiling  water,  the  solution  having  a  weak  alkaline 
reaction  upon  test-paper,  although  borax  is  an  acid  salt.  By  exposure  to  the  air  it 
loses  water.  At  a  moderate  heat  it  separates  into  a  spongy  mass  known  as  calcined 
borax,  and  at  a  red  heat  assumes  a  glassy  appearance ;  in  this  condition  it  is  used 
as  a  blowpipe  flux. 

Octahedral  Borax. — Octahedral  borax  (Na,B407  +  5H20)  is  prepared  in  the  following 
manner  : — Prismatic  borax  is  dissolved  in  boiling  water  till  the  solution  marks  49°  Tw. 
=  1*260  sp.  gr.  This  solution  is  then  allowed  to  cool  very  slowly.  When  the 
temperature  has  fallen  to  79°  C.,  the  octahedral  crystals  begin  to  form,  the  formation 
continuing  till  the  temperature  reaches  56°.  After  this  the  mother  lye  yields  only 
prismatic  crystals.  Unless  great  care  be  taken,  a  mixed  crystallisation  results. 
Buran  recommends  the  preparation  of  octahedral  borax  by  evaporating  a  borax  solution 
to  53°  Tw.  =  i'282  sp.  gr.,  when  it  is  removed  to  a  crystallising  vessel.  When  10  cwts. 
of  borax  are  operated  upon,  the  process  will  take  six  days  to  complete.  The  prismatic 
and  octahedral  salt  crystallise  in  distinct  layers  that  can  be  separated  mechanically. 
Indian  borax  and  Chinese  half-refined  borax  sometimes  contain  octahedral  crystals. 
Octahedral  borax  is  known  in  French  commerce  under  the  names  of  calcined  borax, 
jewellers'  borax,  surface  borax,  &c.  It  is  distinguished  from  prismatic  borax  by  its 
crystalline  form  and  the  proportion  of  water  contained,  by  its  sp.  gr.  =  i'Si,  and  its 
greater  hardness.  While  the  prismatic  borax  remains  unaffected  in  transparency  by 
exposure  to  air,  the  octahedral  borax  rapidly  becomes  opaque,  and,  absorbing  five 
equivalents  of  water,  is  converted  into  the  prismatic  salt. 

Uses  of  Borax. —  The  uses  of  borax  are  very  numerous.  Molten  borax  has  the 
property,  at  high  temperatures,  of  fluxing  metallic  oxides,  vitrefying  with  them  into 
coloured  transparent  glasses ;  for  instance,  with  cobaltous  oxide  a  blue  glass  is  formed, 
and  with  chromic  oxide  a  green  glass.  This  property  is  of  great  utility  in  chemical 


SECT,  in.]  BORIC  ACID  AND  BORAX.  433 

analysis,  as  the  various  metallic  oxides  may  be  thus  distinguished  in  the  blowpipe 
flame.  It  is  also  used  for  soldering  metals ;  and  is  a  constituent  of  Strass,  used 
in  glass  manufacture  and  enamelling.  It  is  used  extensively  in  glazing  the  finer 
kinds  of  earthenware,  and  for  separating  metals  from  their  ores.  Borax  forms 
with  shellac  in  proportion  of  i  part  to  5  a  peculiar  varnish,  soluble  in  water, 
and  used  when  mixed  with  aniline  black  to  stiffen  felt  hats.  With  casein  it  gives  a 
fluid  resembling  a  solution  of  gum-arabic,  for  which  it  is  often  substituted.  Borax 
is  made  into  a  soap  for  washing  purposes,  into  a  solution  for  cleansing  the  hair,  and  it 
is  also  used  in  various  cosmetics,  &c.  It  is  largely  employed  to  fix  mineral  mordants. 
According  to  Clouet,  a  mixture  of  boric  acid  and  potassium  or  sodium  nitrate  is  in 
many  cases  a  better  flux  than  borax.  He  recommends  100  parts  boric  acid  and  100 
parts  of  the  nitrate  to  be  placed  in  an  enamelled  iron  kettle  with  10  per  cent,  water 
and  heated  till  fluid.  When  cooled,  flat  white  crystals  are  formed;  those  made  with 
potassium  nitrate  can  be  used  for  crystal-glass  manufacture,  and  those  with  sodium 
nitrate  for  enamelling.  Chromium  borate  is  known  in  commerce  as  Vert-Guignet  or 
Pannetier's  green.  Borax  sold  in  powder  under  fanciful  names  is  often  adulterated 
with  soda  ash,  common  salt,  and  even  with  quicklime. 

The  Chilian  borosodium  calcite  has  the  following  composition : — 

I.  II.  III.  IV. 

Water        ....  27-33  —  I3'8  ...  40'9°  ...  31 '50 

Lime          ....  17-44  ...  J5'4  •••  8'38  ...  I2'34 

Salt 7-19  ...  31-6  ...  14-20  ...  3-80 

Insoluble  .        .        .  10-69  ...  10-3  ...  1*04  ...          0*21 

Sulphuric  acid  .        .  12*60  ...          9'4  ...  1*20  ...  trace 

Boric  acid         .        .         .  22-55  •••  J9'6  ...  22-32  ...  47'52 

Soda          ....      2-33  ...  ...          3-96  ...          1-63 

According  to  the  proposal  of  Lunge,  the  borate  ground  a,nd  elutriated  is  mixed  with 
two-thirds  its  weight  of  common  hydrochloric  acid  and  double  the  quantity  of  water,  heat 
being  applied  until  the  decomposition  is  complete.  It  is  now  allowed  to  settle,  and  the 
clear  hot  liquor  is  drawn  off  with  a  syphon.  On  cooling,  the  boric  acid  crystallises  out 
almost  entirely,  whilst  sodium  and  calcium  chloride  remain  in  solution  with  the  excess  of 
hydrochloric  acid.  The  proportion  of  two-thirds  refers  to  the  average  composition 
of  the  mineral,  and  must  be  arranged  according  to  each  sample.  The  crystals  of  boric 
acid  are  drained,  pressed,  or  whizzed,  washed  in  cold  water,  whizzed  again,  and  obtained 
almost  absolutely  pure,  so  that  on  treatment  with  soda  they  yield  pure  borax  on  the  first 
crystallisation. 

The  bulk  of  the  borax  consumed  in  Germany  is  prepared  from  boronite-calcite. 
The  manufacture  consists  of  four  processes : 

1 .  Boiling  the  calcium  borate  with  soda. 

2.  Working  up  the  residues. 

3.  Fine  crystallisation. 

4.  Working  up  the  lyes. 

The  first  process  is  conducted  in  large  pans  fitted  with  powerful  agitators,  and 
heated  by  the  direct  introduction  of  steam.  2500  kilos,  of  the  lime  salt  are  stirred  up 
with  four  to  five  times  its  quantity  of  water,  and  the  soda  is  gradually  introduced 
when  the  mixture  boils.  The  soda  should  be  in  slight  excess.  A  mixture  of  soda  ash 
and  bicarbonate  is  preferred.  The  boiling  is  completed  in  three  to  four  hours. 

As  the  neutral  borate  contains  only  4  molecules  of  crystalline  water,  the  formation 
of  this  salt  is  a  serious  loss.  The  contrary  condition  is  also  to  be  avoided.  If  there  is 
no  excess  of  soda  the  crystallisation  is  sluggish.  After  the  whole  has  settled,  the  clear 
supernatant  lye  is  run  off  and  the  mud  is  passed  through  a  filter-press.  The  lye  is 
kept  to  crystallise  in  iron,  four-sided  cisterns,  holding  1000  to  1500  litres.  It  must 
have,  on  the  average,  a  strength  of  49°-5g°  Tw. 


434  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

In  three  or  four  days  the  crude  borax  has  separated  out  in  thick  crystalline 
crusts  on  the  sides  and  bottoms  of  the  cisterns.  The  average  pure  sodium  biborate 
(Na2B407  +  ioH20),  contained  in  these  crude  crystals  is  40  to  50  per  cent.,  the 
residue  being  sodium  sulphate  and  chloride.  The  lyes  can  be  used  for  boiling  several 
times  in  succession,  but  if  they  become  too  concentrated  it  is  better  to  evaporate  them 
down.  The  first  crystallisation  obtained  on  evaporation  contains  borax  enough  to 
be  added  to  the  crude  borax  for  further  treatment. 

The  filter  press  turns  out  the  mud  from  the  boiling  in  solid  cakes,  which  still 
contain  a  quantity  of  mother  liquor.  They  are  lixiviated  with  hot  water ;  the  lye  is 
concentrated  and  added  to  the  crude  borax. 

The  next  stage  is  the  fine  crystallisation  conducted  in  large  four-sided  iron  cisterns 
holding  8-10  cubic  metres.  They  are  enclosed  with  an  outer  coating  of  wood,  the 
space  between  the  wood  and  the  iron  being  packed  with  sawdust,  peat,  &c.,  to  prevent 
sudden  changes  of  temperature. 

The  crude  borax  is  dissolved  in  as  much  pure  water  as  to  yield  a  solution  which 
boiling  marks  50°  Tw.  The  so-called  fine  lye  can  be  repeatedly  used  for  dissolving  fresh 
quantities  of  crude  borax,  but  the  solutions  must  be  made  stronger  each  time,  as  the 
sp.  gr.  is  raised  by  the  sodium  sulphate,  &c. 

Care  must  be  taken  not  to  make  the  solutions  too  strong.  From  such  lyes 
octahedral  borax  crystallises  out  containing  only  5  mols.  water  of  crystallisation,  which 
involves  considerable  loss,  as  the  prismatic  borax — the  commercial  quality — crystallises 
with  10  molecules  of  HS0. 

To  remove  iron  and  traces  of  organic  matter  a  small  quantity  of  sodium  hypochlorite 
is  added,  until  the  lye  is  colourless  in  water  and  gives  no  reaction  with  potassium 
ferrocyanide.  The  hot  lye  is  run  into  the  crystallisation-cisterns,  which  must  be  quite 
full  and  carefully  covered,  to  prevent  too  rapid  cooling.  In  ten  to  fourteen  days, 
according  to  the  weather  and  the  season,  the  temperature  will  have  fallen  to  33°,  and 
the  crystallisation  of  the  borax  will  be  completed.  At  33°  the  sodium  sulphate  begins 
to  crystallise,  and  the  lye  must  be  let  off. 

The  crystalline  crusts  are  rinsed  with  pure  cold  water  to  remove  drops  of  mother 
liquor,  and  are  then  detached  by  striking  the  outsides  with  a  hammer.  The  borax  is 
finally  dried  in  baskets,  in  a  drying-chamber  at  30°  for  twenty-four  hours,  and  any  dirt 
adhering  to  the  under  side  of  the  crystals  is  removed. 

The  lyes  from  the  coarse  and  the  fine  crystallisations  must  not  be  too  often  used  for 
repeated  boilings,  as  they  would  become  too  rich  in  sodium  sulphate  and  chloride. 
Hence  large  evaporating  pans  are  provided  to  receive  them.  In  winter  after  being 
concentrated  they  are  received  into  crystallising  vats  set  in  the  open  air,  when  sodium 
sulphate  crystallises  out  in  quantity.  In  summer  the  sulphate  and  the  common  salt 
have  to  be  boiled  out,  which  involves  a  loss  of  borax. 

In  order  to  recover  the  borax  (about  10  per  cent.)  which  attaches  itself  to  the 
sodium  sulphate,  it  is  heated  very  gently  until  the  latter  salt  melts  in  its  own  water  of 
crystallisation.  The  melted  sulphate  is  then  run  off,  and  the  borax  which  has  remained 
undissolved  remains  in  hard  pieces,  which  may  be  added  to  the  fine  crystallisation. 

Diamond-Boron  or  Adamantine. — Wohler  and  H.  Deville  in  1857  were  the  first  to 
notice  that  boron  occurs,  similarly  to  carbon  in  two  allotropic  conditions,  namely, 
crystalline*  and  amorphous.  Diamond  boron  is  prepared,  in  two  ways,  either  by  the 
reduction  of  calcined  borax  with  aluminium — 

Boric  acid,  B,CU        .}ds      f  Alumina,. A1.0,,  ' 
Aluminium,  2A1)      *  (Boron,  2B; 

or  by  converting  amorphous  boron  into  crystalline.     The  latter  method  gives  the 

*  Graphitic  boron  is  by  a  later  discovery  of  Wohler's  (1867)  resolved  into  boron-aluminium  j 
formula,  AlBj. 


SECT,  in.]  SALTS   OF  ALUMINIUM.  ,  435 

better  result.  100  grammes  of  anhydrous  boric  acid  are  mixed  with  60  grammes  of 
sodium  in  a  small  iron  crucible  heated  to  a  red  heat.  To  this  mixture  40  to  50  grammes 
of  common  salt  are  added,  and  the  crucible  is  luted  clown.  As  soon  as  the  reaction  is 
finished,  the  mass,  consisting  of  amorphous  boron  with  boric  acid,  borax,  and  common. 
salt  intermingled,  is  stirred  into  water  acidified  with  hydrochloric  acid.  The  boron  is 
filtered  out,  washed  with  a  weak  solution  of  hydrochloric  acid,  and  placed  upon  a 
porous  stone  to  dry  at  the  ordinary  temperature.  Molten  iron,  it  is  well  known, 
converts  amorphous  carbon  into  crystalline  graphitic  carbon,  and  aluminium  exercises 
a  similar  action  upon  boron.  The  crystalline  boron  is  prepared  in  the  following  manner  : 
— A  small  crucible  is  filled  with  amorphous  boron,  in  the  centre  of  which  a  small  bar  of 
aluminium,  weighing  4  to  6  grammes  is  placed.  The  crucible  is  submitted  to  a  tempera- 
ture sufiicient  to  melt  nickel  for  one-and-a-half  to  two  hours.  After  cooling,  the 
aluminium  will  be  found  covered  with  beautiful  crystals  of  boron.  The  diamond 
boron  is  easily  separated  from,  the  graphitoid.  The  former  is  a  transparent  tetragonal 
crystal,  of  a  garnet -red  or  honey -yellow  colour,  or,  if  perfectly  pure,  colourless.  It  is 
very  brittle,  hard,  and  lustrous;  it  will  scratch  rubies  easily.  This  discovery  may 
in  time  be  of  great  technical  importance. 

SALTS   OF   ALUMINIUM. 

Alum. — Alum  is  a  saline  substance,  consisting  of  aluminium  sulphate,  potassium,  or 
ammonium  sulphate,  and  water  of  crystallisation.  It  occurs  native  as  potash  alum  and 
as  ammonia  alum,  being,  in  fact,  a  double  salt,  consisting  of  either  aluminium  sulphate 
and  potassium  sulphate,  or  aluminium  sulphate  and  ammonium  sulphate.  The  alum 

known  as  potash  alum,      2 1 4SO4  +  24H20,  is  found  in  alum-shale.      But  all  natural 

K2j 

alums  are  more  of  mineralogical  than  of  technical  interest,  the  alums  of  commerce  being 
always  artificially  prepared.  We  shall,  therefore,  pass  on  to  the  consideration  of  the 
latter. 

Material  of  Alum  Manufacture. —  The  manufacture  of  alum  is  based  on  the 
formation  of  aluminium  sulphate  and  sodium  aluminate  from  the  various  alum  ores. 
These  ores  or  earths,  necessitating  different  methods  of  treatment,  may  be  divided  into 
four  groups,  viz. : — 

1.  Those  which  contain  alumina,  potassa,  and  sulphuric  acid  in  such  proportions 
that  the  addition  of  an  alkaline  salt  is  not  requisite.  •  To  this  group  belong  alum-stone 
and  several  varieties  of  alum-shale. 

2.  Those   in  which   the  aluminium  sulphate  is  alone  present,  necessitating  the 
addition  of  alkali  salts  in  large  quantities.     To  this  group  belong  the  alum-shale  and 
alum-earths  found  in  the  brown-coal  formation. 

3.  Those  in  which  alumina  only  is  contained,  and  to  which  both  sulphuric  acid  and 
alkali  salts  must  be  added.     To  this  group  belong — (a)  clay,  (b)  cryolite,  (c)  bauxite, 
alumina  terhydrate  (Gibbsite),  (d)  refuse  slack. 

4.  To  the  fourth  group  belong  those  materials,  such  as  felspar,  containing  alumina 
and  potash  in  sufficient  quantity,  but  needing  the  addition  of  sulphuric  acid. 

Preparation  of  Alum  from  Alum-stone  (ist  Group}. — Alum-stone  or  alunite  occurs 
only  in  volcanic  regions,  and  is  the  product  of  the  action  of  the  sulphurous 
vapours  upon  substances  rich  in  felspar.  It  is  found  at  Tolfa,  near  Civita  Vecchia,  and 
in  large  quantities  at  Muszag,  in  Hungary.  The  crystallised  alum-stone  consists 
of  potassium  and  aluminium  sulphates  with  aluminium  hydroxide,  according  to 
Mitscherlich— K2S04  +  A12(S04)3  +  2(A12O33H2O). 

Alum-stone  loses  its  water  at  a  red  heat,  the  product  of  the  calcination  being 
oifluenced  by  water,  while  unburnt  alum-stone  is  not.  At  a  strong  red  heat  the 


436  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

aluminium  sulphate  separates  into  alumina,  sulphurous  acid,  and  oxygen,  and  the 
potassium  sulphate  is  also  decomposed.  The  mineral  is  calcined  in  lime-kilns  in  the 
ordinary  manner  or  in  reverberatories.  The  calcined  alum-stone  is  lixiviated  with 
boiling  water,  the  supernatant  liquor  decanted,  and  the  alum  crystallised  out.  Roman, 
rock,  or  roche  alum  is  prepared  in  a  similar  manner,  the  red  colour  being  due  to 
peroxide  of  iron.*  Latterly,  the  calcined  stone  is  lixiviated  with  dilute  sulphuric  acid 
instead  of  water. 

Preparation  of  Alum  from  Alum-Shale  and  Alum-Earths  (2nd  Group}. — This 
mode  of  preparation  yields  the  greatest  amount  of  alum  with  as  much  facility  as  does 
alum-stone. 

Alum-Shale. — Alum-shale  or  schist  is  a  sulphurous  iron  pyrites  found  under  beds  of 
clay  in  Upper  Bavaria,  in  Prussia,  near  Dlisseldorf,  Saxony,  Bohemia,  Belgium, 
Hurlet  and  Campsie,  near  Glasgow,  &c.  Only  very  inferior  kinds  require  an  addition 
of  alkali  salts. 

Alum-Earths. — Alum-earth  is  more  qr  less  a  mixture  of  weathered  iron  pyrites  with 
various  bituminous  matters.  The  sulphur  is  present  partly  in  a  free  state,  partly  as  iron 
and  vitriol  pyrites ;  the  iron  is  present  partly  as  sulphide,  partly  as  iron  humate. 

Preparation  of  Alum. — The  preparation  of  the  alum  may  be  considered  in  the 
following  six  operations  : — 

1.  Roasting  the  Alum-Earth. — The  roasting  of  the  alum-earth  is  the  easiest  of  the 
operations.     The  greater  part  of  the  alum  manufactured  is  produced  by  precipitating 
aluminium  sulphate  with  a  solution  of  alkali  salts.     It  is  not  always  necessary  that  the 
schist  should  be  burnt  to  concentrate  the  aluminium  sulphate,  a  lengthy  weathering 
being  sufficient.      The  action  may  be   explained   as   follows : — By   the   weathering, 
the  iron  bisulphide  absorbs  oxygen,  to  form  iron  sulphate,    which    separates    into 
protoxide  of  iron  and  sulphuric  acid,  the  latter  acting  upon  the  alumina  forming  an 
equivalent  quantity  of  aluminium  sulphate.     Or  by  roasting,  the  bisulphide  is  decom- 
posed to  monosulphide  and  sulphur,  which,  with  the  sulphur  of  the  alum-earth,  gives 
rise  to  sulphurous  acid,  and  this  acting  upon  the  alumina  produces  aluminium  sulphate 
and  sulphite.     The  roasting  or  calcination,  however,  should  not  take  place  with  earths 
that  have  been  subjected  to  less  than  a  year's  weathering,  as  there  is  found  to  be  in 
practice  a  loss  of  one-sixth  of  the  aluminium  sulphate. 

2.  Lixiviation. — The  lixiviation  of  the  calcined  alum  earths  is  effected  in  a  lixivia- 
tion  cistern  in  which  the  earth  is  placed.     These  tanks  stand  in  rows  of  five,  the  best 
arrangement  being    to    build  them  on  a  slope    near  the  calcination  heaps.      Each 
vessel  has  a  length  of  6  to  7  metres,  is  5  metres  broad,  and  about  1-3  metre  in  height. 
They  are  three-parts  filled  with  the  burnt  earth,  and  completely  with  water ;    the 
lixivium  flows  from  the  highest  tank  to  the  lowest.     If  the  lye  is  not  of  ri6  sp.  gr. 
fresh  shale  is  added. 

3.  Evaporation  of  the  Lye. — The  concentration  of  the  raw  lye  by  evaporation  is 
accomplished  in  leaden  pans.     These,  however,  deteriorate,  crack,  are  easily  melted, 

*  The  composition  of  Roman  alunite,  according  to  C.  Schwarz,  is—- 
Silica      13*40  per  cent. 

Alumina  .  .  .  .  35'5o 
Potassa  .  .  .  .  1 2-  50 
Sulphuric  acid  .  .  .  30-00 
Ferric  oxide ....  0^05 

Water 8-50 

The  alunite  is  most  advantageous  if  roasted  at  500°,  and  extracted  with  sulphuric  acid  at  from 
1*297  to  I '530  sp.  gr.  Roman  alum  crystallises  in  cubes.  If  such  alum  is  dissolved  in  water  and 
the  liquid  is  heated  to  100°,  basic  alum  is  deposited  and  the  mother  liquor  yields  on  evaporation 
octahedral  crystals.  Common  alum  can  be  converted  into  the  cubic  kind  by  digesting  with 
aluminium  hydroxide  at  40°. 


SECT,  m.]  SALTS  OF  ALUMINIUM.  437 

and  their  place  is  now  generally  supplied  by  cisterns  of  masonry.  But  most  to  be 
preferred  is  Bleibtreu's  method  of  heating  with  gas,  introduced  in  the  alum  works  on 
the  banks  of  the  Rhine.  The  treatment  of  the  raw  lye  while  being  concentrated 
depends  upon  its  condition  and  upon  the  ferrous  sulphate  it  contains.  As  ferrous  sul- 
phate is  commonly  present  in  large  quantities  in  the  raw  lye  or  liquor,  many  of  the 
German  alum  works  are  also  vitriol  works.  When,  however,  the  quantity  of  ferrous 
sulphate  is  too  small  to  admit  of  being  advantageously  treated  for  the  preparation  of 
copperas,  the  liquor  is  at  once  evaporated  until  it  has  attained  a  sp.  gr.  of  1*40.  During 
the  ebullition  basic  iron  sulphate  is  deposited,  the  liquor  becomes  of  yellow-red  colour, 
assumes  a  somewhat  slimy  condition,  and  has  to  be  rendered  clear  before  alum  is 
obtained  from  it.  This  clearing  is  effected  by  pouring  the  liquor  into  large  wooden 
water-tight  tanks ;  the  liquor  having  deposited,  the  suspended  matter  is  tapped  or 
syphoned  off  from  the  sediment,  and  transferred  to  the  precipitation  tanks. 

4.  Alum-flour. — The  precipitation  of  flour  of  alum  is  effected,  in  case  it  is  desired  tc 
make  potash-alum  by  the  addition  to  the  liquor  of  a  potash  salt,  or  of  an  ammonia 
salt  if  it  is  desired  to  make  ammonia-alum.     The  solution  of  the  alkaline  salt  is  called 
the  precipitant ;   by  the  combination  of  the  aluminium  sulphate  contained  in  the 
liquor  with  the  precipitant  alum  is  formed,  and  deposited  as  a  solid  salt,  care  being 
taken  to  prevent  the  formation  of  large  crystals  by  keeping  the  liquid  stirred.     By 
this  means  the  alum  is  deposited  as  a  crystalline  powder  or  so-called  flour  of  alum, 
which  by  being  washed  with  cold  water  can  be  freed  from  any  adhering  mother 
liquor.     The  precipitation  was  formerly  effected  by  the  addition  of   wood-ash  lye  or 
lant ;  at  the  present  day  potassium  chloride  obtained  either  from  kelp,  carnallite,  or 
beet-  root  molasses,  and  potassium  sulphate  derived  from  the  decomposition  of  kainite, 
are    employed    for    this    purpose.      Potassium   chloride   is    useful    only    when    the 
solution  contains  large  quantities  of  ferrous   sulphate,  which,  being  converted  into 
ferric  chloride,  forms  potassium  sulphate.    Potash  can  only  be  used  when  the  lye  contains 
enough  free  sulphuric  acid  to  combine  with  the  salt ;  for  otherwise  a  portion  of  the 
aluminium  sulphate  would  become  precipitated  as  insoluble  alumina.     The  ammonia 
salt  made  use  of  is  generally  ammonium  sulphate ;  100  parts  of  aluminium  sulphate 
require  for  precipitation — 

Potassium  chloride       .        .        .        .         .     43'S  parts 

„          sulphate 50^9    „ 

Ammonium  sulphate 47*8    „ 

The  liquor  covering  the  alum-flour  is  somewhat  of  a  green  colour,  and  contains  little 
alum,  but  chiefly  ferroso-ferric  chloride,  iron  and  magnesium  sulphates,  or  magnesium 
chloride,  dependent  upon  whether  the  precipitation  was  effected  by  sulphates  or 
by  chlorides.  This  liquor  is  used  for  making  impure  alum,  ferrous  sulphate,  or  is 
employed  in  the  preparation  of  ammonium  sulphate. 

5.  Washing  and  Re-crystallisation. — The  floury  alum  is  generally  washed  in  the 
hydro-extractor  or  centrifugal  machine  and  the  liquor  obtained  again  used  for  pre- 
paring alum.    The  washed  floury  alum  is  (6)  converted  into  large  crystals  by  re-crystal- 
lisation, the  alum  at  the  same  time  being  purified.     For  this  purpose  the  alum-flour 
is  dissolved  in  40  per  cent,  of  its  weight  of  boiling  water,  the  operation  being  carried 
on  in  wooden  lead-lined  tanks.     The  hot  solution  is  run  into  crystallising  vessels, 
where  the  crystallisation  is  finished,  according  to  the  temperature  of  the  air,  in  eight  to 
ten  days.     From  this  operation  hardly  any  mother  liquor  remains,  the  vessel  being 
almost  entirely  filled  with  alum  crystals. 

Preparation-  of  Alum  from  Clay  (yd  Group). — The  manufacture  of  alum  and  of 
aluminium  sulphate  from  such  materials  as  contain  only  alumina,  to  which  consequently 
sulphuric  acid  and  alkaline  salts  have  to  be  added,  has  come  largely  into  practice  in 


438  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

England.  The  materials  employed  are : — (a)  clay,  (b)  cryolite,  (c)  bauxite,  (d)  blast- 
furnace slag. 

(a)  Preparation  of  Alum  from  Clay. — The  clay  to  be  employed  for  this  purpose 
should  be  as  free  as  possible  from  calcium  and  iron  carbonates.  It  is  first  gently 
heated  in  contact  with  air,  partly  with  the  view  of  dehydration,  partly  for  the 
purpose  of  converting  any  iron  into  oxide,  and  lastly  to  render  the  clay  more  readily 
soluble  in  acids.  By  dehydration  the  clay  becomes  porous  and  fit  to  take  up 
sulphuric  acid  by  capillarity.  The  gently  ignited  and  powdered  clay  is  gradually  put 
into  sulphuric  acid  of  140°  Tw.  (  =  1-52  sp.  gr.)  contained  in  a  leaden  pan,  and  heated 
nearly  to  the  boiling-point.  The  mass  effervesces  and  becomes  thick,  and  is  next 
transferred  to  iron  tanks,  where  it  solidifies.  It  is  afterwards  lixiviated  with  water,  or, 
better,  with  the  liquor  obtained  by  washing  the  alum-flour.  The  lixivium,  having  become 
clear  by  standing,  is  syphoned  off  from  the  sediment,  and  boiled  with  a  sufficient 
quantity  of  potassium  bisulphate  or  ammonium  sulphate  from  gas  liquor.  The  hot 
solution  is  transferred  to  a  shallow  leaden  pan,  and  kept  stirred  for  the  purpose  of 
converting  the  alum  on  separating  into  flour.  The  flour  is  washed,  dried,  and  is  then, 
converted  into  large  crystals  as  described  above.  The  product  known  in  the  trade  as 
alum-cake  is  the  result  of  the  action  of  sulphuric  acid  upon  clay ;  it  is  met  with  in  a 
pulverised  state,  is  used  more  especially  in  the  manufacture  of  inferior  kinds  of  paper,  in 
dyeing,  and  as  a  precipitant  for  sewage,  and  contains  from  13  to  17  per  cent,  of  alumina. 

(b)  Preparation  of  Alum  from  Cryolite. — Since  the  year  1857  alum  and  aluminium 
sulphate  have  been  prepared,  along  with  soda,  from  the  mineral  known  as  cryolite  or 
Greenland  spar,  A12F6  +  6NaF2,  and  consisting  in  i  oo  parts  of — 

Fluorine  .';''.  ,.  .  .  .  .  54*5 
Aluminium  ;  .  '  ,:  .  .  .  .  .  13*0 
Sodium  '  .  .  .  .  u  .  .  •  32'5 

The  following  are  the  methods  employed  for  this  purpose : — 

(a)  Decomposition  of  Cryolite  by  Ignition  with  Calcium  Carbonate  according  to 
Thomsen's  Method. — i  molecule  of  cryolite  is  ignited  with  6  molecules  of  calcium  car- 
bonate, carbonic  acid  escapes,  and  soluble  sodium  aluminate  and  insoluble  calcium 
fluoride  are  formed  —  Al2F6.6NaF  +  6 CaC03  =  Al2(ONa)6  +  6CaF2  +  6C02.  From 
the  ignited  mass  the  sodium  aluminate  is  obtained  by  lixiviation  with  water,  and  into 
the  solution  carbonic  acid  gas  is  passed.  The  result  is  the  precipitation  of  hydrated 
gelatinous  alumina  and  sodium  carbonate,  which  remains  in  solution.  If  it  be  desired 
to  obtain  the  alumina  as  an  earthy  compact  precipitate,  sodium  bicarbonate  is  used  as 
a  precipitant  instead  of  carbonic  acid.  While  the  clear  liquor  is  boiled  down  for  the 
purpose  of  obtaining  sodium  carbonate,  the  precipitated  alumina  is  dissolved  in  dilute 
sulphuric  acid ;  this  solution  is  evaporated  for  the  purpose  of  obtaining  aluminium 
sulphate  (so-called  concentrated  alum),  or  the  solution,  after  having  been  treated  with  a 
potassa  or  ammonia  salt,  is  converted  into  alum.  100  Ibs.  of  cryolite  yield  33  Ibs.  of 
alumina,  which  require  90  Ibs.  of  sulphuric  acid  to  yield  a  neutral  solution ;  100  Ibs.  of 
cryolite  will  therefore  yield  305  Ibs.  of  alum,  and  may  give  in  addition — 

Calcined  soda 75-0  Ibs.,  or 

Crystallised  sodium  carbonate       .         .         .  203x3    „     or 

Caustic  soda 44-0    „     or 

Sodium  bicarbonate      .         .        .        .         .119-5,, 

(j3)  Decomposition  of  Cryolite  urith  Caustic  Lime  by  the  Wet  Way  (Sauerwein's  Method). 
— Yery  finely  ground  cryolite  is  boiled  with  water  and  lime,  the  purer  the  better,  and 
as  free  from  iron  as  possible,  in  a  leaden  pan.  The  result  is  the  formation  of  a  solution 
of  sodium  aluminate  and  insoluble  calcium  fluoride — 

Al,Fl4,6NaFl  +  6CaO  =  Al2(ONa)6  +  6CaFl,. 


SECT,  m.]  SALTS   OF   ALUMINIUM.  439 

When  the  calcium  fluoride  has  been  deposited,  the  clear  liquid  is  decanted,  and  the 
sediment  washed,  the  first  wash-water  being  added  to  the  decanted  liquor,  and  the 
second  and  third  wash-waters  being  used  instead  of  pure  water  at  a  subsequent 
operation.  In  order  to  separate  the  alumina  from  the  solution,  of  sodium  aluminate, 
there  is  added  to  the  liquid,  while  being  continuously  stirred,  very  finely  pulverised 
cryolite  in  excess,  the  result  of  the  decomposition  being  exhibited  by  the  following 
formula — Al2(ONa)6  +  Al2KaGFin  -  2A1203+  i2NaF.  When  no  more  caustic  soda  can 
be  detected  in  the  liquid — a  small  quantity  of  which  should,  after  filtration,  yield, 
upon  the  addition  of  a  solution  of  sal-ammoniac  and  application  of  heat,  a  pre- 
cipitate of  alumina — it  is  left  to  stand  for  the  purpose  of  becoming  clear.  The 
clarified  solution  of  sodium  fluoride  is  then  drawn  off,  and  the  alumina  treated  as 
above  described.  The  solution  of  sodium  fluoride  having  been  boiled  with  caustic  lime 
yields  a  caustic  soda  solution  which,  having  been  decanted  from  the  sediment  of  calcium 
fluoride,  is  evaporated  to  dryness.  The  calcium  fluoride  obtained  as  a  bye-product 
of  the  cryolite  industry  is  now  used  in  glass-making. 

(y)  The  decomposition  of  cryolite  by  sulphuric  acid  yields  sodium  sulphate,  con- 
vertible into  carbonate  .by  Leblanc's  process,  and  aluminium  sulphate  free  from  iron- 
238  parts  of  cryolite  require  for  decomposition  240  parts  of  anhydrous  or  321  parts  of 
ordinary  sulphuric  acid.  The  resulting  compounds  are  aluminium  sulphate,  sodium 
sulphate,  and  hydrofluoric  acid  :  Al2Na0Fl2  +  6H2S04  =  Al2(S04)33Na2SO4  +  1 2HF.  This 
method  of  decomposing  cryolite  is,  however,  by  no  means  to  be  recommended,  as, 
owing  to  the  liberation  of  hydrofluoric  acid,  peculiarly  constructed  apparatus  are 
required ;  while  the  sodium  sulphate  has  to  be  converted  into  sodium  carbonate. 
Persoz  suggests  that  cryolite  should  be  treated  in  platinum  vessels  with  three  times  its 
weight  of  strong  sulphuric  acid,  to  be  recovered  with  the  hydrofluoric  acid  by  distil- 
lation. The  solid  residue  should  be  treated  with  cold  water  in  order  to  dissolve  the/ 
larger  part  of  the  sodium  bisulphate  contained  in  the  saline  mass,  from  which  the 
anhydrous  aluminium  sulphate  is  extracted  with  boiling  water,  and  converted  by  the 
addition  of  potassium  or  ammonium  sulphate  into  alum  free  from  iron.  The  solution  of 
sodium  bisulphate,  having  been  evaporated  to  dryness,  is  employed  for  the  preparation 
of  fuming  sulphuric  acid,  Glauber's  salt  remaining  as  a  residue. 

(c)  Preparation   of  Alum  from  Bauxite. — In  some  parts  of  Soiithern  France,  in 
Calabria,  near  Belfast,  Ireland,  and  other  parts  of  Europe,  a  mineral  occurs  consisting 
essentially  (60  per  cent.)  of  hydrated  alumina  of  greater  or  less  purity,  termed  bauxite, 
from  the  fact  of  having  been  first  found  in  the  commune  of  Baux,  in  France.     In  order 
to  prepare  alum  and  aluminium  sulphate  from  this  mineral,  it  is  first  disintegrated  by 
being   ignited  with  sodium   carbonate,  or  with  a  mixture  of  sodium  sulphate  and 
charcoal ;  in  each  instance  the  lixiviatioii  of  the  ignited  mass  yields  sodium  aluminate, 
from  which,  by  processes  already  described  under  Cryolite,  alum,  or  aluminium  sulphate 
and  soda  are  prepared. 

(d)  Preparation  of  Alum  from  Blast-Furnace  Slag. — J.Lurmann  recommends  that  the 
slag  should  be  decomposed  by  means  of  hydrochloric  acid.     From  the  resulting  solution 
of  aluminium  chloride  *  the  alumina  is  precipitated  by  calcium  carbonate,  any  dis- 
solved  silica   being  precipitated   at   the  same  time.      The   alumina  is   dissolved  in 
sulphuric   acid,    leaving   the   silica;    100  kilos,   of  slag  containing   25   per   cent,   of 
alumina  yield  180  kilos,  of  alum  and  31  kilos,  of  silica. 

Alum  from  Felspar  (qth  Group}. — The  manufacture  of  alum  from  minerals  (for 
instance,  felspar)  containing  alumina  and  potassa  is  not  of  any  industrial  importance. 

*  Crude  aluminium  chloride  is  used  as  a  disinfectant  under  the  name  of  chloralum,  and  as  a 
precipitant  for  sewage.  Compare  Slater's  Sewage  Treatment. 


440  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Properties  of  Alum.— Potash-alum,  K3  J4S04  +  24H,0,  orK2S04  +  A1,(SO<), 
consists  in  100  parts  of — 


Potassa 9*95 

Alumina 10-83 

Sulphuric  acid 337  * 

Water 45'S1' 


It  crystallises  readily  in  regular  octahedra,  loses  at  60°  18  mols.  of  water,  and  fuses  at 
92°  in  its  water  of  crystallisation,  yielding  a  colourless  fluid  which  retains  its  state  of 
aggregation  for  some  time  after  cooling  before  it  solidifies  into  a  crystalline  mass.  At 
a  temperature  a  little  below  red  heat  alum  loses  all  its  water,  becoming  converted  into 
burnt-alum,  alumen  ustum,  a  white,  porous,  readily  friable  mass.  "When  ignited 
with  carbonaceous  matter,  air  being  excluded,  potash-alum  forms  a  pyrophoric 

compound. 

100  parts  of  water  at    o°  dissolve    3-9  parts  of  potash-alum 
„  »  20         „         15-8        „  „ 

»  »i  40  „  31'2  r,  „ 

„  „         loo         „      360-0        „  „ 

The  solution  of  alum  in  water  (the  salt  is  insoluble  in  alcohol)  has  an  astringent, 
sweet  taste,  and  possesses  an  acid  reaction  so  strong  that  when  alum  is  heated  with 
common  salt  hydrochloric  acid  is  evolved;  while  a  concentrated  solution  of  alum 
destroys  the  blue  colour  of  many  —  not  of  all  —  artificial  ultramarines. 

Ammonia  Alum.  —  This  salt, 


'  or  (NH4)*S°4  +   A12(S04)3    +    24H20, 
consists  in  100  parts  of  : 

Ammonia       ......  3-89 

Alumina         ......  11-90 

Sulphuric  acid       .....  35'  10 

Water    .  48-11 


lOO'OO 

Ammonia-alum  is  now  far  more  extensively  manufactured  than  potash-alum. 
When  ammonia-alum  is  strongly  heated,  ammonium  sulphate,  water,  and  sulphuric 
acid  are  driven  off,  and  alumina  remains. 

loo  parts  of  water  at    o°  dissolve  5-22  parts  of  ammonia-alum 
ii  »  20        „        i3"C5        „  ,i 

»  »  4°        „        27-27        „  „ 

»»  »          I0°        ii      421-90        ii  M 

Soda-Alum. — The  formula  of  this  salt  is — 


+    24H20,  or  Na,S04    +    A12(S04)3    +    24H,O, 
containing  in  100  parts — 

Soda 6-8 

Alumina  n-2 

Sulphuric  acid 34-9 

Water 47-1 

lOO'O 

It   is   as  readily  prepared   from   aluminium   sulphate    and   sodium  sulphate  as  the 
alums  already  mentioned,  but  its  solubility  prevents  the  separation  from  the  mother 

*  Manmene  questions  the  existence  of  45-51  per  cent,  of  water  in  alum. 


SECT,  in.]  SALTS   OF  ALUMINIUM.  441 

liquor,  while  its  solution  when  boiled  loses  the  property  of  crystallising.  As  iron 
cannot  be  removed  from  this  salt  by  re-crystallisation,  the  materials  it  is  obtained  from 
should  be  free  from  that  metal.  The  solutions  should  be  mixed  cold,  and  gently 
evaporated  at  a  temperature  not  exceeding  60°. 

Neutral  or  cubical  alum  (K2S04  +  A1203, 2  S03)  is  obtained  either  by  adding  to  an 
alum  solution  so  much  potassium  or  sodium  carbonate  as  will  begin  to  separate  the 
alumina,  or  a  solution  of  alum  is  treated  with  gelatinous  alumina.  By  boiling  1 2  parts 
of  alum  and  i  part  of  slaked  lime  in  water,  the  same  salt  is  obtained.  This  neutral 
salt  is  often  preferred  in  dyeing  and  calico  printing,  as  it  does  not  affect  certain 
colours.  When  ammonia-alum  is  similarly  treated,  it  also  yields  a  neutral  alum. 
Blesser  (a)  and  Schmidt  (b)  found  the  following  to  be  the  composition  of  cubical  alum 
in  100  parts  : — 

(«)  W 

Sulphuric  acid 34'52  ...  33'95 

Alumina ir86  ...  11-48 

Potassa 9-44  ...  9-04 

Water 45-27  ...  45-61 

101-09  •••          loo-oS 

Insoluble  or  basic  alum,  A12K2.2S04,  is  obtained  by  boiling  a  solution  of  alum  with 
hydrate  of  alumina ;  it  is  a  white,  insoluble  powder,  and  as  regards  its  composition 
similar  to  alum-stone.  Basic  alum  is  soluble  in  acetic  acid. 

Aluminium  Sulphate. — The  active  principle  of  alum  is  evidently  the  aluminium 
sulphate,  not  the  potassium  and  ammonium  sulphates,  the  object  of  the  preparation  of 
the  double  salt  being  simply  the  obtaining  of  a  definite  compound,  which,  while  it 
readily  crystallises,  can  be  obtained  in  a  pure  state,  especially  free  from  iron,  a  very 
injurious  ingredient  in  alum  used  in  dyeing  and  calico-printing.*  However,  at  the 
present  day,  with  improved  methods  of  manufacture,  aluminium  sulphate  is  largely 
prepared,  and  of  excellent  quality.  It  is  often  sold  under  the  name  of  concentrated 
alum  or  cake  alum,  as  it  occurs  in  the  trade  as  square  cakes.  It  is  white,  somewhat 
transparent,  and  may  be  cut  with  a  knife ;  is  readily  soluble  in  water,  contains  always 
free  sulphuric  acid,  and  also  to  some  extent  potassa-  and  soda-alum. 

In  the  pure  state  this  salt  has  the  formula  A13(S04)3+  i8H2O,  and  contains  in  100 
parts — alumina,  iS'yS;  sulphuric  acid,  38'27  ;  water,  42^95;  total,  100.  That  the 
composition  of  this  salt  as  met  with  in  commerce  varies  greatly  may  be  inferred 
from  the  following  results  of  Varrentrapp's  analyses  of  different  samples  of  this 
salt: — 

i.  2.  3-  4. 

Alumina     .        .        .     15*3         ...         I2'5         ...         15'!         ...         13-0 
Sulphuric  acid  .        .     38-0        -~         30-6        ...         38x3        ...         34*0 

According  to  the  formula,  the  quantify  of  sulphuric  acid  in  these  samples  should  have 
been — 

I-  2.  3.  4- 

35'8  «.  29-2  43'3  3o-5 

The  quantity  of  water  even  varies  between  56  and  48  per  cent,  for  different  parts 
of  the  same  cake.  "Weygand  found  a  sample  of  this  salt  prepared  at  Schwemsal  to 
contain — alumina,  I5'57;  sulphuric  acid,  38'i3;  oxide  of  iron,  i'i5;  potassa,  0*62; 
water,  45*79  parts.  The  aluminium  sulphate  prepared  from  cryolite  at  Harburg  con- 
tains about  5  per  cent,  of  sodium  sulphate.  The  results  obtained  in  the  analyses  by 
H.  Fleck  of  various  samples  of  cake-alum  are — 

*  An  almost  infinitesimal  trace  of  iron  renders  alum  unfit  for  dyeing  alazarine  reds  or  roses. 


442  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Aluminium  sulphate     .        .        .  47'35        ...        5o'8o        ...        51-63 
Sodium               „           ...      4-35         ...  1-24         ...          077 

Free  sulphuric  acid      .        .        .      073         ...          0-27 

Water 47'37         •••         47'47         •••         46'94 


99-80         ...         9978         ...        99-34 

Cake-alum  is  prepared  either  from  clay,  cryolite,  or  bauxite,  by  methods  already 
described.  When  clay  is  employed,  the  iron  has  to  be  removed  from  the  dilute  solution 
of  the  aluminium  sulphate  by  precipitation  as  Berlin  blue  by  means  of  potassium 
ferrocyanide.  When  cryolite  is  used,  the  alumina,  separated  from  the  solution  of 
sodium  aluminate  by  carbonic  acid  or  powdered  cryolite,  is  put  into  sulphuric  acid, 
contained  in  a  wooden  lead-lined  tank,  and  heated  to  80°  to  90°,  the  addition  of  the 
alumina  to  the  acid  being  continued  until  solution  ceases  to  take  place.  The  solution 
having  been  clarified  by  standing  for  some  time  is  next  evaporated  in  a  copper  vessel 
until  the  salt  fuses ;  it  is  then  cast  into  moulds.  With  due  care  aluminium  sulphate 
may  be  used  in  dyeing  and  calico-printing,  but  it  cannot  be  altogether  substituted  for 
alum,  owing  to  its  variable  composition. 

Aluminium  hydrochlorate,  formerly  known  as  muriate  of  alumina,  may  be  prepared 
in  an  impure  state  by  the  process  of  Georges  Fournier,  who  lixiviates  pyritic  alum  shales, 
previously  well  weathered,  allows  ferrous  sulphate  to  crystallise  but  and  adds  to  the 
residual  lye  of  aluminium  sulphate  containing  iron  sulphate,  sodium  chloride.  At  tem- 
peratures of  —  i°  or  —  2°  sodium  sulphate  crystallises  out  and  is  drained  by  whizzing. 
The  mother  liquor  is  aluminium  hydrochlorate. 

Slater  dissolves  in  crude  hydrochloric  acid  a  mineral  found  in  the  North  of  Ireland 
which  differs  from  bauxite  by  containing  3  instead  of  2  mols.  of  combined  water 
and  by  being  easily  soluble  in  hydrochloric  acid.  Both  these  forms  of  aluminium 
hydrochlorate  are  well  adapted  for  the  treatment  of  sewage  and  refuse  waters  -by 
precipitation. 

Sodium  Aluminate. — Sodium  aluminate  is  now  prepared  on  the  large  scale,  as  it 
has  been  found  to  be  a  useful  form  of  soluble  alumina,  especially  in  dyeing  and  calico- 
printing.  The  preparation  of  this  compound  is  based  upon  the  solubility  of  alumi- 
nium hydroxide  in  caustic  potassa-  or  soda-lye,  and  the  ready  decomposition  of  the 
solution  by  carbonic  and  acetic  acids,  sodium  bicarbonate  and  sodium  acetate,  sal- 
ammoniac,  &c. 

Sodium  aluminate  was  first  brought  under  the  notice  of  dyers  by  Macquer  and 
Hausmann  in  1819,  but  owing  to  the  preparation  being  too  expensive  it  did  not  come 
into  industrial  application  until  comparatively  recently.  We  have  already  described 
the  mode  of  manufacturing  sodium  aluminate  from  cryolite ;  but  in  Germany — the 
chief  seat  of  the  cryolite  industry — this  salt  is  not  made  on  the  large  scale ;  in  France 
it  is  manufactured  by  Merle  &  Co..  at  Alais,  and  in  England  at  the  Washington 
Chemical  Works.  In  France  bauxite,  containing  60  to  75  per  cent,  of  alumina  and 
from  12  to  20  per  cent,  of  oxide  of  iron,  is  the  raw  material,  and  is  treated  with  sodium 
hydroxide  or  carbonate.  If  caustic  soda  is  used,  the  pulverised  mineral  is  boiled  with  a 
solution  of  the  alkali ;  while  if  the  carbonate  is  employed,  the  mixture  is  ignited  in  a 
reverberatory  furnace.  In  either  case  sodium  aluminate  is  produced,  dissolved — in  the 
case  of  ignition,  the  semi-fused  mass  is  lixiviated  with  water — and  evaporated  to 
dryness.  The  salt  met  with  in  commerce  is  a  white  powder  with  a  green-yellow  hue, 
dry  to  the  touch,  and  consisting  of — 

Alumina      .    _    .        .        .        .        .        .48 

Soda   ........    44 

Sodium  chloride  and  sulphate  .  .8 


SECT,  in.]  ,    SALTS   OF  ALUMINIUM.  443 

Al  ) 
The  formula,  ^  2  j-  06,  would  require  — 


Alumina  ...        .        .        .     5279 

Soda 47'2i 


Sodium  aluminate  is  equally  soluble  in  cold  and  hot  water.  Exposed  to  air  it 
absorbs  moisture  and  carbonic  acid,  and  consequently  on  being  dissolved  in  water  the 
salt  so  changed  yields  a  turbid  solution,  owing  to  alumina  being  suspended.  The  aqueous 
solution  of  this  salt  -is  not  stronger  than  14°  to  18°  Tw.  =  1*07  to  1^09  sp.  gr. 
According  to  Le  Chatelier,  Deville,  and  Jacquemart,  aluminium  sulphate  is  the  starting- 
point  of  the  preparation  of  sodium  aluminate  by  precipitating  from  the  sulphate 
the  alumina,  and  re-dissolving  the  latter  in  caustic  soda-lye.  Sodium  aluminate  is 
largely  used  in  the  preparation  of  an  opaque,  milky-looking  glass,  or  semi-porcelain. 
Sodium  aluminate  is  a  bye-product  of  Balara's  method  of  soda  manufacture  from 
bauxite,  Glauber's  salt,  and  coal ;  this  bye-product,  or  rather  product  of  the  second 
stage  of  the  process,  is  decomposed  by  carbonic  acid  into  sodium  carbonate  and  alumina, 
which  is  thrown  down.  The  Pennsylvania  Salt  Manufacturing  Company  at  Natrona, 
near  Pittsburg,  manufacture  large  quantities  of  sodium  aluminate,  which  is  used  in 
soap-boiling  under  the  name  of  natrona  refined  saponifier.* 

Aluminium  Hydrate,  A12(OH)6,  is  obtained  by  adding  to  sodium  aluminate  cream 
of  lime,  when  insoluble  calcium  aluminate  separates  out — 

Al2(ONa)6   +    3Ca(OH)2   =   6Na(OH)   +   Ca3Al206. 

After  washing,  the  precipitate  is  dissolved  in  hydrochloric  acid,  and  the  solution 
decomposed  with  a  fresh  quantity  of  calcium  aluminate,  when  aluminium  hydroxide  is 
deposited,  which  is  washed  and  dried — 

Ca3Al206   +   I2HC1   =   3CaCl2  +   A12C16   +  6H20. 
A12C16  +   Ca3Als06  +  6H20    =  -sCaCl,   +   2A1S(OH)6. 

Aluminium  hydrate  is  obtained  also  on  precipitating  a  solution  of  sodium  with 
carbonic  acid,  sodium  bicarbonate,  or  sal-ammoniac,  or  by  precipitating  a  solution  of 
alum  with  sodium  carbonate. 

Aluminium  hypochlorite  has  been  proposed  for  bleaching ;  aluminium  sulphite  for 
disinfection  and  for  preserving  articles  of  animal  food  ;  and  aluminium  oxalate  for  pre- 
serving articles  of  marble,  dolomite,  &c.  Aluminium  chloride,  free  from  iron,  &c.,  was 
proposed  some  time  ago  as  a  disinfectant,  under  the  name  of  chloralum,  but  at  present 
it  is  used  for  "  carbonising  "  wool.  Aluminium  acetate  is  used  in  dyeing  f  (see  Mordants). 
A  very  questionable  aluminium  carbonate  has  been  proposed  for  sanitary  purposes. 
Applications  of  Alum  and  Aluminium  Salts. — Owing  to  the  great  affinity  of  the 
alumina  contained  in  alum  for  textile  fibres,  especially  wool  and  cotton,  alum  is  largely 
used  as  a  mordant  in  dyeing,  except  when  the  tar  colours  are  employed.  Again,  owing 
to  the  affinity  of  alumina  for  many  pigments,  alum  is  employed  in  the  preparation  of  the 
lake  colours,  combinations  of  active  colouring  principles  with  alumina.  It  is  also  used 
in  the  melting  of  tallow ;  for  hardening  gypsum ;  it  is  found  in  the  preparation  used 
for  sizing  hand-made  paper,  the  alum  in  this  case  forming  with  the  glue  or  size  an 
insoluble  compound.  Alum  with  resin  is  employed  for  the  same  purpose  in  machine- 
made  paper,  an  aluminium  pinate  being  formed.  It  is  very  largely  used  for  the 
preparation  of  aluminium  acetate,  and  with  common  salt  in  the  tawing  of  leather. 
Alum  is  employed  in  clarifying  turbid  fluids,  more  especially  water ;  in  this  case  the 

*  Sodium  aluminate  is  nsed  by  Maxwell  Lyte  for  the  treatment  of  soda  by  precipitation,  for 
which  purpose  it  is  very  suitable. 

t  Aluminium  acetate,  for  the  production  of  alizarine  roses  and  reds  in  dyeing  and  tissue-printing, 
is  being  to  some  extent  superseded  by  aluminium  sulphocyanide  (rhodanide).  Compare  Hummel, 
Dyeing  of  Textile  Fabrics,  p.  172.  Aluminium  nitrate  is  also  occasionally  used  as  a  mordant. 


444  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

alum  takes  up  the  alumina  suspended  in  the  water,  and,  forming  an  insoluble  (basic) 
alum,  carries  down  organic  and  other  suspended  impurities.  A  boiling  solution  of 
alum,  common  salt,  and  potassium  nitrate  is  used  by  jewellers  for  the  purpose  of 
colouring  gold— that  is  to  say,  to  produce  a  film  of  pure  gold  on  the  alloy,  the  copper 
of  which  is  dissolved  by  the  boiling  solution.  Sodium  aluminate  is  used  in  dyeing  and 
calico-printing ;  further,  for  the  preparation  of  lake  colours,  the  induration  of  stone, 
and  the  manufacture  of  artificial  stone,  and  for  the  saponifi  cation  of  fats  in  the  stearine 
candle  manufacture,  an  alumina  soap  being  first  formed,  which  is  decomposed  by  acetic 
acid  into  aluminium  acetate  and  free  fatty  acid. 

ULTRAMARINE. 

Ultramarine  is  a  splendid  blue  colour,  formerly  obtained  in  small  quantities  from 
lazulite.  Its  analysis  led  to  the  production  of  artificial  ultramarine — an  invention 
ascribed  by  the  French  to  Guimet,  but  by. the  Germans  to  C.  Gmelin. 

Raw  Materials. — These  are — i.  Aluminium  silicate  as  free  as  possible  from  iron,  a 
good  china  clay,  the  kaolin  of  Cornwall  being  esteemed  the  best;  2.  Calcined  sodium 
sulphate  ;  3.  Calcined  soda ;  4.  Sodium  sulphide,  as  a  bye-product  of  the  manufacture ; 
5.  Sulphur;  6.  Pulverised  charcoal,  or  pit-coal. 

Porcelain,  or  china  clay,  is  generally  used,  or  a  white  clay,  the  composition  of 
which  is  nearly  the  same.  Small  quantities  of  lime  and  magnesia  have  no  injurious 
effect,  but  the  oxide  of  iron  should  not  exceed  i  per  cent.  The  composition  of  the 
clay  should  approach  as  nearly  as  possible  to  the  formula  H2Al,Si208 ;  the  silica  may  be 
combined  or  partly  free.  The  clay  is  washed  with  water  and  treated  in  the  same 
manner  as  for  making  porcelain;  ib  is  next  dried,  ignited,  and  ground  to  a  very 
fine  powder.  The  sodium  sulphate  should  not  contain  any  free  acid,  lead,  or  iron.  If 
the  sulphate  does  not  possess  the  requisite  qualities,  it  is  dissolved  in  water,  milk  of 
lime  being  added  to  neutralise  the  acid  and  to  precipitate  oxide  of  iron.  The  clear 
solution  is  left  to  crystallise,  and  the  crystals  are  ignited  in  a  reverberatory  furnace 
and  then  pulverised.  The  clear  solution  is  in  some  cases  evaporated  to  dryness  and 
ignited  in  iron  vessels.  Barium,  but  not  potassium,  salts  form  ultramarine.*  The 
calcined  soda  is  obtained  from  the  alkali  works,  and  should  contain  at  least  90  per  cent, 
of  sodium  carbonate ;  it  is  also  finely  pulverised.  Very  recently  caustic  soda  has  been 
substituted  in  some  ultramarine  works.  Sodium  sulphide  (Na2S)  is  usually  a  bye-pro- 
duct of  the  process  of  making  ultramarine,  and  is  obtained  either  in  solution  or  as  a 
dry  powder.  The  sulphur  is  used  very  finely  pulverised.  The  carbonaceous  matter 
employed  is  also  in  a  very  fine  powder.  Its  use  was  introduced  by  Leykauf  for  the 
purpose  of  deoxidation.  In  order  to  have  the  carbon  in  as  finely  divided  a  state  as 
possible  it  is  ground  to  a  pulp  with  water  under  granite  stones  ;  the  pulp  is  lixiviated, 
and  the  fine  powder  obtained  dried  and  passed  through  a  sieve ;  in  some  cases  resin 
and  pitch  are  employed.  For  ultramarines  which  must  not  have  their  colour  discharged 
by  alum,  pure  silica,  either  as  fine  glass,  sand,  or  pulverised  quartz,  is  used.  Several 
substances  are  used  to  reduce  the  depth  of  colour  of  ultramarine — viz.,  gypsum,  barium, 
sulphate,  baryta  white,  and  flour ;  the  last  is  employed  in  making  up  washing  blue. 

Manufacture  of  Ultramarine. — The  methods  of  ultramarine  preparation  may  be 
classified,  according  to  the  crude  materials  employed,  as  the  three  following : — 
(a)  Preparation  of  sulphate,  or  Glauber's  salt,  ultramarine. 
(6)  „          ,,     soda-ultramarine, 

(c)  ,,  ,,     silica-ultramarine. 

(a)  Preparation  of  Sufyhate- Ultramarine. — This  ultramarine  is  prepared  according 

*  See  Chemical  News,  vol.  xxiii.  pp.  119,  142,  204. 


SECT,  in.]  ULTRAMARINE.  445 

to  the  Nuremberg  process  from  kaolin,  sodium  sulphate,  and  charcoal ;  the  preparation 
consisting  in  two  distinct  stages,  viz. : — 

(a)  Preparation  of  green  ultramarine. 
(/3)  Conversion  of  green  into  blue  ultramarine. 

(a)  Preparation  of  Green  Ultramarine. — In  order  to  obtain  a  most  intimate  mixture 
of  the  dry  and  finely  pulverised  materials,  small  quantities  are  weighed  off,  mixed  in 
wooden  troughs  by  means  of  shovels,  and  several  times  passed  through  sieves.  If 
solutions  of  Glauber's  salt,  soda,  and  sodium  sulphide  are  used  instead  of  powders 
the  kaolin  is  mixed  with  these  solutions,  and  the  whole  evaporated  to  dryness,  gently 
ignited  in  a  reverberatory  furnace,  and  then  pulverised  and  sifted.  The  quantities  of 
the  crude  materials  vary,  but  the  following  conditions  have  to  be  complied  with : — 
i.  Soda,  whether  sulphate  or  caustic,  must  be  present  in  such  quantity  that  it  can 
saturate  half  of  the  silica  of  the  clay  (kaolin).  2.  There  must  be  sufficient  soda 
remaining  to  form  with  the  sulphur  a  certain  quantity  of  sodium  polysulphide. 
3.  There  ought  to  remain  enough  sulphur  and  sodium  to  form  another  sodium  sul- 
phide (Na2S)  after  deducting  from  the  whole  mixture  as  much  green  ultramarine  as, 
according  to  its  composition  as  proved  by  recent  analysis,  the  silica  and  alumina 
present  are  capable  of  forming.  The  following  figures  will  give  an  idea  of  the  pro- 
portions : — 

I.  n. 

Kaolin  (dried)      ....         100        ...         100 
Calcined  Glauber's  salt         .         .     83-100       ...  41 

Calcined  soda      ....         —          ...          41 
Carbon  (char- or  pit-coal)   .         .  17         ...  17 

Sulphur —         ...  13 

For  100  parts  of  calcined  soda  So  parts  of  calcined  Glauber's  salt,  and  for  100  parts  of 
the  latter  60  of  dry  sodium  sulphide,  are  taken. 

It  is  usual  to  have  a  large  quantity  of  this  mixture  prepared  for  use.  If  this 
mixture  is  ignited  without  access  of  air,  a  white  mass  is  obtained,  which,  having  been 
treated  with  water,  is  a  light,  somewhat  flocculent,  white  substance,  to  which  Ritter 
has  given  the  name  of  white  ultramarine.  It  becomes  green  by  exposure  to  air,  and 
blue  by  being  calcined  in  contact  with  air.  The  mixture  is  well  rammed  into  fire-clay 
crucibles,  placed  in  furnaces  similar  in  construction  to  those  used  for  burning  porcelain, 
being  raised  to,  and  maintained  at,  a  high  temperature  with  a  very  limited  supply  of  air. 
This  operation  lasts  from  seven  to  ten  hours,  and  is  completed  at  a  bright  white  heat. 
The  furnace  is  closed  and  slowly  cooled;  on  removing  the  crucibles,  the  contents  appear  as 
a  semi-fused  grey-  or  yellow-green  mass,  which  is  repeatedly  treated  with  water.  The 
ultramarine  thus  obtained  is  in  porous  lumps,  which  are  pulverised  into  an  impalpable 
powder ;  this  is  washed,  dried,  and  again  ground,  then  sifted,  and  finally  packed  in 
boxes  or  casks,  and  sent  into  the  market  as  green  ultramarine,  consisting,  according  to 
Stolzel's  analysis  (1855),  in  100  parts,  of — 

Alumina 3O-n 

Iron 0'49  (ferric  oxide,  07) 

Calcium 0-45 

Sodium 19-09  (soda,  2573) 

Silica 37"46 

Sulphuric  acid 076 

Sulphur 6-o8 

.  ,     .         Chlorine 0-37 

Magnesia,  potassa,  phosphoric  acid     .  traces 

94-81 
Oxygen         ...       .       .        .      5'i9 


446  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Green  ultramarine  is  a  pigment  of  comparatively  inferior  value,  owing  to  its  being 
less  brilliant  than  the  green  copper  pigments. 

(/3)  Conversion  of  Green  into  Blue  Ultramarine. — This  operation  may  be  variously 
effected,  generally  by  roasting  the  green  ultramarine  and  sulphur  at  a  low  temperature 
with  access  of  air,  so  as  to  form  sulphurous  acid,  while  a  portion  of  the  sodium  is 
oxidised  into  soluble  sulphate  and  afterwards  washed  out ;  but  the  sulphur  originally 
present  in  the  green  ultramarine  remains  combined  with  a  smaller  quantity  of  sodium. 
The  roasting  may  be  variously  carried  out,  but  very  frequently  the  apparatus  consists 
of  a  fixed  iron  cylinder  similar  to  a  gas-retort,  provided  with  a  stirring  apparatus,  by 
means  of  which  the  mixture  of  green  ultramarine  and  sulphur  (25  to  30  Ibs.  of  the 
former  to  i  Ib.  of  sulphur)  is  submitted  equally  to  the  source  of  heat.  The  addition  of 
sulphur  is  repeated  until  the  desired  blue  colour  is  produced  ;  but  in  some  works  this 
calcination  is  interrupted  by  repeated  lixiviation,  the  object  being  to  produce  a  superior 
article.  Muffle-ovens  and  a  kind  of  reverberatory  oven  are  also  used  for  this  operation. 
The  sulphurous  acid,  which  is  evolved  in  large  quantities,  is  now  generally  employed  in 
making  sulphuric  acid,  sometimes  a  co-product  of  ultramarine  manufacture,  and  used 
for  the  preparation  of  the  sodium  sulphate  required.  The  ultramarine,  when  quite 
blue,  is  pulverised,  lixiviated,  dried,  and  finally  separated  into  various  qualities  known 
in  the  trade  as  No.  oo,  i,  2,  3,  &c. 

(b)  Preparation  of  Soda-Ultramarine. — As  manufactured  in  France,  Belgium,  and 
some  parts  of  Germany,  this  ultramarine  is  either  pure  soda-ultramarine  or  a  mixture 
of  soda-  and  sulphate-ultramarine.     The  materials  and  proportions  are — 

i.  II.  m. 

Kaolin 100  ...  ioo  ...  100 

Sulphate          ....  —  ...  41 

Soda       .        .        .        .        .  ioo  ...  41  ...  90 

Carbon  (char- or  pit-coal)       .  12  ...  17  ...  6 

Sulphur           ....  60  ...  13  ...  ioo 

Kosin      .....  —  ...  ...  6 

The  ignition  takes  place  either  in  crucibles,  or,  better,  in  a  reverberatory  furnace ; 
the  result  is  the  formation  of  a  brittle  and  porous  green  substance,  which  absorbs 
oxygen  very  rapidly,  so  that,  during  the  cooling  of  the  mass  in  the  oven,  the  greater 
part  is  converted  into  blue  ultramarine.*  The  complete  conversion,  after  the  addition 
of  sulphur,  is  obtained  by  heating  to  redness  in  large  muffles,  the  bottoms  of  which 
consist  of  plates  of  fire-clay  and  the  lids  of  iron,  the  product  being  distinguished  from 
the  foregoing  by  a  greater  depth  and  beauty  of  colour.  By  increasing,  within  certain 
limits,  the  quantities  of  soda  and  sulphur,  the  formation  of  blue  ultramarine  may  be 
at  once  obtained,  the  product  containing  10  to  12  per  cent,  of  sulphur. 

(c)  Preparation  of  Silica-  Ultramarine. — Silica-ultramarine  is  really  soda-ultramarine 
in  the  preparation  of  \vhich  silica  to  the  amount  of  5  to  10  per  cent,  of  the  weight  of 
the  kaolin  is  added.     The  calcination  at  once  yields  blue  ultramarine,  and  further 
treatment  with  sulphur  is  therefore  unnecessary. 

This  ultramarine  is  not  acted  upon  by  a  solution  of  alum,  and  may  be  recognised 
by  its  peculiar  red  hue,  the  intensity  of  which  is  increased  by  an  increase  of  silica. 
Notwithstanding  the  superiority  of  the  ultramarine  obtained  by  this  process,  its  pre- 
paration is  disadvantageous  owing  to  the  tendency  of  the  mixture  of  crude  materials  to 
fuse  during  ignition. 

The  composition  of  the  two  chief  kinds  of  ultramarine  with  a  reddish  blue  (I.)  and 
a  pure  blue  tone  (II.)  appears  from  the  following  analysis  by  B.  Hofmann  : — 

*  Ultramarine  green  cannot  be  obtained  by  this  process. 


SECT.  nr.  ULTRAMARINE,  447 

i.  n. 

Clay  residues 3-61  ...  2-11 

Silica         .        .        .        .        .        .  4077  ...  3777 

Alumina 2374  ...  29-54 

Potassa     .                 .                                 0-83  ...  1-38 

Soda          ......  18-54  ...  21-61 

Sulphur     .        .        .        .        .        .  13-58  ...  7-87 

101-07  •••  100.28 

Siliceous  blues  from  the  Hirschberg  works  (I.  to  IV.)  and  from  the  Marienberg 
works  (V.  and  VI.)  had,  according  to  Guckelberger's  analysis,  the  following  composi- 
tions : — 

I.  II.  III.  IV.  V.  VI. 

Si  .  .  19-2  ...  19-0  ...  19-0  ...  19-3  ...  19-3  ...  19-0 

Al  .  .  i2'6  ...  12-7  ...  13-0  ...  12-5  ...  i2'8  ...  13-0 

Na  .  16-5  ...  16-8  ...  16-5  ...  16-8  ...  i6'i  ...  15-9 

S     .  .  14-2  ...  14-0  ...  13-8  ...  13-9  ...  14-0  ...  14-0 

O    •  •  37'5  •••  37'5  -  377  -  37'5  -  37'8  ...  38-1 

Since  1873  the  Nuremberg  Ultramarine  Works  produces  violet  and  red  ultra- 
marine. These  kinds  are  obtained  by  treating  blue,  green,  or  white  ultramarine,  at 
a  high  temperature  and  with  access  of  air,  with  acids  or  salts  which  give  off  acids  if 
strongly  heated.  A  violet  is  first  formed,  and  on  heating  more  strongly  a  red.  Violet 
ultramarine  can  also  be  obtained  by  hydroxylating  the  blue  and  the  green  kinds. 

Constitution  of  Ultramarine. — The  cause  of  the  blue  colour  of  ultramarine  has  been 
the  subject  of  repeated  investigation.  In  1758,  Marggraf  refuted  the  view  then  pre- 
valent that  lazulite  contained  copper,  which  was  the  cause  of  its  colour.  As  he 
detected  the  presence  of  iron  he  thought  this  metal  must  be  the  colouring  principle. 
Guy  ton  de  Morveau  ascribed  the  colour  to  iron  sulphide. 

As  according  to  Guckelberger  there  are  in  the  colour  almost  exactly  Na2CaSi2,  the 
charge  must  contain  Si2Na4.  On  exposure  to  the  action  of  S02  at  a  suitable  tempera- 
ture, without  escape  of  oxygen,  there  is  formed  from  Na3  +  2S02  =  S  4-  NaaS04 — i.e.,  the 
nascent  sulphur  fills  up  the  vacancy  formed  by  the  exit  of  Na2 ;  we  may,  therefore, 
obtain  from  Si2Al2Na4O9,  the  compound  Si,Al2Na,S09 — i.e.,  ultramarine  blue.  Hence 
there  is  no  Na2S  in  the  compound,  and  if  on  the  action  of  aqueous  acids  H2S,  or 
along  with  it  S02,  is  obtained  and  free  sulphur  is  separated  out,  this  ensues  because 
the  constituents  of  water  combine  with  the  nascent  sulphur.  The  composition 
of  ultramarine  green  agrees  with  the  formula  Si6AlcN"a8S2024.  Under  the  influence 
of  heat  the  5  mols.  Na2S04  of  the  charge  are  converted  by  carbon  into  5Na2S03. 
With  the  increase  of  temperature  4  mols.  Na2S03  are  resolved  into  3Na2S04  +  Na2S. 
The  fifth  mol.  may  for  the  first  be  considered  as  unaltered.  The  regenerated 
sulphate  (3  mols.)  is  again  reduced  by  carbon  to  3Na2S03,  which  along  with  the 
still  existing  mol.  Na2SO3  undergo  the  well-known  change  on  heating,  so  that  in  a 
certain  stage  there  are  present  3Na2S04  and  2Na2S.  On  increase  of  temperature 
the  Si02  enters  into  reaction,  and  by  the  aid  of  carbon  it  withdraws  Na20  from 
sodium  sulphate.  There  is  formed  Si6Al6Na6024,  an  unsaturated  nucleus  with  two 
free  affinities.  The  escaping  S03  acts  upon  the  existing  2Na2S  ;  there  are  formed 
sulphate  and  2NaS,  which  satisfy  the  free  affinities  of  the  nucleus. 

In  the  blue  strata  the  same  process  goes  on  at  first,  but  the  S02  escaping  from  the 
green  acts  by  removing  sodium,  so  that  §  sulphur  must  be  found  in  the  crude  green 
and  |-  in  the  crude  sulphur,  as  experiment  has  shown  £  sulphur  escapes  partly  as  SO2 
and  partly  free.  The  compound  examined  by  Silber  is,  according  to  Guckelberger, 
to  be  considered  as  Si6Al6Na4(OH)2023.  If  we  suppose  in  this  compound  HO 
replaced  by  the  equivalent  NaS,  the  simplest  expression  for  ultramarine  blue  will  be=» 


44S  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Si6  Al6Na4(NaS)2023.  The  siliceous  colour,  Si6AlcNa4(NaS)2  +  S2,  contains  the  sulphur, 
either  as  NaS — S,  or  we  have  — S — S — ,  instead  of  A1203. 

Properties  of  Ultramarine. — Artificial  ultramarine  is  an  impalpable  powder  of  a  fine 
blue  colour,  entirely  insoluble  in  water,  and,  when  washed  with  distilled  water,  leaving 
no  residue  on  evaporation  of  the  filtrate.  It  is  not  acted  upon  by  alkalies,  but  is  highly 
sensitive  to  the  action  of  even  very  dilute  acids  and  acid  salts,  sulphuretted  hydrogen 
being  evolved  and  the  colour  discharged.  Native  ultramarine  obtained  from  lapis  lazuli 
is  not  thus  decomposed  by  weak  acid  solution.  There  sometimes  accidentally  occurs  in 
soda  furnaces  a  more  or  less  blue  ultramarine  which  exhibits  the  same  resistance  to  acids. 
That  kind  of  ultramarine  commercially  termed  acid  proof  is  manufactured  with  the 
addition  of  silica,  as  described,  but  it  really  only  resists  the  action  of  alum-salts.  Ultra- 
marine is  now  largely  used  for  the  purposes  to  which  smalt,  litmus,  and  Berlin  blue 
were  applied — that  is  to  say,  ultramarine  is  employed  as  a  paint,  as  a  pigment  in  stereo- 
chromy,  for  paper-hangings,  calico-printing  with  albumen  as  fixing  material,  for  colour- 
ing printing-ink,  for  the  bluing  of  linen  and  cotton  fabrics,  paper,  stearine-  and  paraffine- 
candles,  and  lump-sugar.  For  1000  cwts.  of  sugar  2\  Ibs.  of  the  pigment  are  employed, 
a  quantity  so  small  as  to  be  perfectly  innocuous ;  further,  ultramarine  does  not  contain 
anything  injurious  to  health.  Green  ultramarine  is  a  dull-coloured  powder  used  by 
wall-paper  stainers,  and  is  sometimes  mixed  with  indigo-carmine  and  a  yellow  pigment 
to  improve  the  colour. 

Adulterations  of  ultramarine  with  Berlin  blue,  smalt,  and  other  blue  pigments  do 
not  now  occur,  as  ultramarine  is  a  cheaper  material ;  but  to  obtain  lighter  tints, 
ultramarine  is  sometimes  mixed  with  chalk,  kaolin,  alabaster,  and  chiefly  with  barium 
sulphate. 

COMPOUNDS  OF  TIN  AND  ANTIMONY. 

Mosaic  Gold  (Aurum  Musivum). — The  substance  known  under  this  name  is  in 
reality  a  bisulphide  of  tin  (SnS2),  prepared  in  the  following  manner : — 4  parts  of  pure 
tin,  with  2  of  mercury,  are  amalgamated  by  the  aid  of  a  gentle  heat,  and  introduced 
wich  z\  parts  of  sulphur  and  2  of  sal-ammoniac  into  a  flask,  and  heated  on  a  sand-bath, 
at  first  gently,  and  then  gradually  increasing  to  a  full  red  heat.  First  the  sal-ammoniac 
volatilises,  and  next  mercury  in  the  shape  of  cinnabar  mixed  with  a  trace  of  the  sulphide 
of  tin ;  while  there  is  left  the  preparation  known  as  mosaic  gold,  forming  the  upper  layer 
of  the  remaining  contents  of  the  flask,  the  lower  portion  being  of  badly  coloured  sul- 
phide. The  rationale  of  the  formation  of  this  peculiar  coloured  sulphide — that  is, 
peculiar  as  regards  its  physical  appearance — is  not  quite  clearly  explained ;  the  compound, 
moreover,  may  be  prepared  without  mercury.  When  properly  prepared,  it  appears  as  a 
golden-coloured  metallic  substance,  greasy  to  the  touch,  and  soluble  in  the  alkaline  sul- 
phurets.  It  is  chiefly  used  for  imitating  gilding  on  painted  surfaces,  but  its  employment 
is  very  much  restricted  from  the  fact  that  the  bronze-colours  give  a  more  satisfactory 
result.  Indeed,  in  the  English  market  mosaic  gold  is  almost  obsolete. 

Tin  Crystals  (solid)  (Stannous  Chloride,  SnCl2.2H20). — By  the  name  of  tin-salt  the 
trade  understands  chloride  of  tin  (SnCl2),  but  the  commercial  article,  being  prepared  by 
dissolving  granulated  tin  in  hydrochloric  acid  and  evaporating  the  solution,  is  really 
SnCl2+2H20.  According  to  H.  Nollner,  hydrochloric  acid  gas  should  be  caused  to 
act  on  granulated  tin  placed  in  earthenware  receivers,  and  the  concentrated  tin-salt 
solution  thus  obtained  evaporated  in  block-tin  vessels.  The  salt  occurs  in  the  trade  in 
colourless,  transparent,  diliquescent  crystals,  of  course  very  soluble  in  water.  The 
aqueous  solution,  unless  acidulated  with  more  hydrochloric  or  tartaric  acid,  soon  depo- 
sits a  basic  salt.  Tin-salt  is  used  chiefly  in  dyeing  and  calico-printing.* 

*  Copper  vessels  may  be  used  for  dissolving  tin  in  hydrochloric  acid,  as  whilst  any  tin  remains 
undissolved  the  copper  is  not  attacked.  Stannous  chloride  is  also  used  in  the  liquid  state  as  single 


SECT,  in.]  COMPOUNDS   OF  ANTIMONY.  449 

Tin  Chloride,  Stannic  Chloride  (SnCl45H20)  is  obtained  by  dissolving  stannic  oxide 
in  hydrochloric  acid.  If  it  be  desired  to  obtain  the  solid  stannic  chloride,  the  solution 
is  mixed  with  clean  sand  or  infusorial  earth,  dried  and  distilled  in  a  current  of  super- 
heated steam.* 

The  so-called  "  nitrate  of  tin  "  is  made  by  dissolving  grain  bar  tin  (not  granulated) 
in  single  aquafortis,  which  must  be  absolutely  free  from  sulphuric  acid  or  the  lower 
oxides  of  nitrogen,  though  it  may  contain  a  proportion  of  hydrochloric  acid.  The 
operation  must  be  conducted  very  carefully,  the  temperature  must  not  be  allowed  to  rise, 
and  no  red  fumes  must  be  given  off.  This  mordant,  which  is  of  a  peculiar  reddish 
yellow  colour,  served  in  grounding  cochineal  scarlets,  is  now  consequently  nearly  fallen 
into  disuse. 

Pink  Salt,  SnCl4  +  2NH4C1,  is  used  in  tissue-printing,  though  less  in  Britain  than 
on  the  Continent.  A  concentrated  solution  of  this  salt  is  not  affected  by  boiling,  but  if 
diluted  it  deposits  all  its  stannic  oxide  upon  the  fibre.  Its  neutral  character  is  its  great 
recommendation . 

Stannate  of  Soda,  preparing  salt  (Na2Sn03). — This  salt  is  now  very  largely  used  in 
dyeing  as  well  as  in  calico-printing,  and  is  prepared  in  various  ways,  sometimes  by 
fusing  tin-ores  with  caustic  soda  and  lixiviating  the  molten  mass  with  water;  or, 
according  to  Brown,  by  boiling  soda  lye  with  metallic  tin  and  litharge,  the  effect 
being  the  formation  of  sodium  stannate  and  metallic  lead.  Hiiffely  somewhat 
modifies  this  process  by  digesting  litharge  with  soda  lye  at  22  per  cent,  in  a  metallic 
vessel.  Into  the  solution  of  sodium  plumbate  thus  obtained,  granulated  tin  is  placed 
and  heat  applied.  Sometimes  a  sodium  stannite  is  used,  made  by  dissolving  tin- 
salt  in  an  excess  of  caustic  soda,  but  this  preparation  is  unstable  and  does  not  answer 
well  in  dyeing  and  printing ;  it  is  only  extemporaneously  used  on  a  limited  scale  by 
small  dyers."}" 

COMPOUNDS  OF  ANTIMONY. 

Antimony  Oxide. — This  substance  (Sb303),  obtained  by  calcining  antimony  sul- 
phide, or  by  the  precipitation  of  a  solution  of  antimony  chloride  with  a  solution 
of  sodium  carbonate,  finally  washing  and  drying  the  precipitate,  has  of  late  been  used 
as  a  substitute  for  white-lead,  but  it  does  not  cover  so  well  and  is  more  expensive,  though 
it  is  not  affected  by  sulphuretted  hydrogen.  As  this  oxide  takes  up  oxygen  in  the 
presence  of  alkalies,  and  is  converted  into  antimonic  acid  (Sb205),  it  has  been  lately 
proposed  for  use  in  the  preparation  of  aniline  red  and  for  the  conversion  of  nitrobenzol 
into  aniline ;  also  for  the  preparation  of  calcium  iodide  by  keeping  antimonic  oxide 
suspended  in  milk  of  lime,  and  adding  iodine  as  long  as  the  latter  is  taken  up. 

Black  Antimony  Sulphide. — This  compound  (Sb3S3)'  obtained  by  liquation,  occurs 
in  commerce  in  the  conical  shape  it  has  assumed  while  cooling ;  its  colour  is  like  that  of 
graphite,  but  it  has  a  stronger  metallic  lustre,  is  of  a  deeper  black  colour,  a  fibrous, 
crystalline  structure,  and  very  brittle ;  it  usually  contains  iron,  lead,  copper,  and  arsenic, 
and  is  employed  for  separating  gold  from  silver,  in  veterinary  surgery ,  pyrotechny,  and  in 

and  double  muriates,  differing  merely  in  their  concentration ;  single  muriates  vary  from  40°  to  60° 
Tw.  and  double  muriates  from  70°  to  120°.  The  former  contain  i  to  2  oz.  metallic  tin  in  the 
pound,  and  the  double  kind  from  z\  to  5  oz.  All  forms  of  stannous  chloride  are  used  as  mordants. 
See  Slater  :  Manual  of  Colours  and  Dye  Wares. 

*  The  various  liquids  used  by  dyers  and  printers  under  the  names  of  solution,  composition,  &c., 
are  made  by  dissolving  metallic  tin  in  mixtures  of  hydrochloric  acid  and  nitric  acid,  differing 
greatly  in  strength  and  proportions,  and  with  or  without  the  addition  of  alkaline  chlorides.  Oxalic 
acid  or  tartaric  acid  is  often  added  to  the  finished  solution. 

t  The  author  states  that  "  some  years  ago  the  use  of  a  double  sodium  salt  of  arsenic  and  stannic 
acids  was  introduced  among  English  dyers."  The  use  of  this  dangerous  preparation,  though 
not  prohibited  by  law,  is  condemned  by  the  best  authorities  as  affording  no  advantages  com- 
mensurate with  its  poisonous  properties. 

?.  F 


45° 


CHEMICAL   TECHNOLOGY. 


[SECT.  iii. 


the  preparation  of  the  percussion  pellets  used  in  the  cartridges  of  the  now  celebrated 
Prussian  needle-gun. 

Neapolitan  Yellow. — This  pigment,  used  as  an  oil  paint  and  in  glass  and  porcelain 
staining,  is  of  an  orange-yellow  colour,  and  very  permanent.  It  is  lead  antimo- 
iiiate,  and  is  prepai-ed  as  follows  : — i  part  of  potassium  antimonio-tartrate  (tartar 
emetic),  2  parts  of  lead  nitrate,  and  4  parts  of  common  salt,  are  fused  at  a  moderate 
red  heat,  and  kept  at  that  temperature  for  two  hours.  The  molten  mass  is  put  after 
cooling  into  water  and  becomes  disintegrated,  the  salt  dissolving  and  the  pigment 
precipitating.  When  required  for  staining  glass  or  porcelain  it  is  mixed  with  a  lead- 
glass.  It  has  recently  been  prepared  by  roasting  a  mixture  of  antimonious  acid 
and  litharge. 

Antimony  Cinnabar. — Antimony  oxysulphide  (Sb.-SgO^,  is  a  compound  in  colour 
similar  to  vermilion,  and  is  obtained  by  causing  sodium  or  calcium  dithionite  to  act 
upon  antimonious  chloride  in  water,  and  boiling  this  mixture,  a  precipitate  being 
readily  deposited  ;  it  is  a  soft,  velvety  powder,  unaltered  by  the  action  of  air  and  light, 
and  suited  for  either  oil-  or  water-colour.  This  substance  may  be  prepared  on  a  large 
scale  by  the  following  process  : — (i)  Black  antimony  sulphide  is  calcined  in  a  current 
of  air  and  steam,  antimonic  oxide  being  formed  as  well  as  sulphurous  acid,  which  may 
be  employed  for  the  preparation  of  calcium  dithionite  from  soda  waste  ;  the  antimonic 
oxide  is  next  dissolved  in  crude  hydrochloric  acid.  (2)  Large  wooden  tubs  which 
admit  of  being  internally  heated  by  steam,  are  for  |ths  of  their  capacity  filled  with  the 
solution  of  calcium  dithionite,  and  the  solution  of  antimonious  chloride  is  gradually 
added,  the  liquid  being  stirred  and  heated  to  about  60° ;  the  reaction  soon  ensues,  and 
the  precipitate  having  subsided,  is  thoroughly  washed  and  dried  at  a  temperature  not 
exceding  50°.  There  are  prepared,  on  a  large  scale,  by  operative  pharmaceutical  and 
manufacturing  chemists,  numerous  varieties  of  antimoiiial  preparations,  among  which 
are  several  sulphides  and  one  oxysulphide,  different  from  the  preparation  here 
mentioned. 

Antimony  Pentasulphide,  Sb2S3,  is  obtained  by  decomposing  sodium  sulphanti- 
moniate  with  hydrochloric  acid.  It  is  used  for  vulcanising  caoutchouc,  for  which 
purpose  sodium  thiosulphate  is  added. 

COMPOUNDS   OF  ARSENIC. 

Arsenic  Acid,  according  to  Schoop,  is  obtained  on  the  large  scale  in  the  following 
manner.  The  plant  shown  (Fig.  367)  in  plan  in  ^v  of  its  natural  size,  consists  of  the 

Fig-  367- 


generators,  A,  the  absorbent  vessels,  B,  a  neutralising  pan,  0,  and  an  evaporating  pan,  D. 
Six  generators,  A,  are  connected  in  a  suitable  manner  with  five  receivers,  v.     ~R™™  *k« 


From  the 


SECT.   III.] 


COMPOUNDS   OF   ARSENIC. 


last  receiver  the  tube,  r,  leads  to  the  condensing  pots,  B.  After  the  gases  have  passed 
through  these  vessels,  they  enter  the  chimney  through  the  tube,  z.  Shortly  before  this 
exit,  there  is  a  glass  tube  inserted  for  observing  the  colour  of  the  gases.  Each 
generator  consists  of  an  earthen  vessel,  A  (Fig.  368  in  ^  natural  size),  which  has  three 
apertures  provided  with  hydraulic  joints.  The  middle,  largest  aperture  serves  to 
admit  a  cylindrical  stoneware  piece,  R.  This  piece  is  perforated  like  a  sieve  in  its  lower 
half.  The  arsenical  powder  is  introduced  through  a  smaller  opening,  o,  in  the  cover, 
whilst  the  third  smaller  opening  receives  the  escape-pipe,  n.  The  entire  stoneware 
vessel  stands  in  a  wooden  vat,  Jf,  and  can  be  surrounded  with  water,  the  temperature 
of  which  can  be  regul  ated  at  pleasure  by  meansof  the  steam-  or  water-pipes,  w  and  d. 
The  exit  pipe,  n,  opens  into  an  earthen  vessel,  which  has  essentially  the  same  form  as 
that  shown  in  the  conde  nsing-vessel,  B  (Fig.  369,  in  -^  of  its  natural  size),  but  having 
three  openings  instead  of  two.  The  five  receivers,  r,  are  connected  below  with  the 


Fig.  370 


generators  in  such  a  manner  that  the  fumes  of  a  generators  have  to  traverse  two  to 
three  receivers  before  arriving  at  the  real  condensation -pots,  B.  This  arrangement  is 
to  prevent  loss  in  case  the  contents  of  any  generator  boil  over.  The  condensing  pots 
B  (Figs.  369  and  370),  have  two  large  apertures  for  the  gas-entrance-  and  exit-pipes, 
as  well  as  a  small  hole,  i,  for  supplying  water  or  dilute  nitric  acid.  Near  the  bottom 
there  is  a  smaller  opening,  x,  provided  with  a  stoneware  cock  for  letting  off  nitric  acid. 
The  number  of  the  pots  is  at  least  60,  to  avoid  imperfect  condensation.  In  proportion 
as  the  contents  of  the  pots  nearest  the  generators,  A,  reacn  the  necessary  concentration 
{sp.  gr.  1-32  to  i'35),  they  are  drawn  off  and  replaced  by  a  similar  quantity  of 
liquid  from  the  next  pot,  further  from  the  generators.  Whilst  water  is  put  into  the 
pot  nearest  the  chimney,  nitric  acid  of  sp.  gr.  1*34  is  drawn  off  from  the  first 
•condensing-pot.  Into  each  generator  there  are  poured  180  kilos,  nitric  acid  of  sp.  gr. 
1'35  to  i '4°>  and  150  kilos,  powdered  arsenic  (so-called  white  arsenic)  are  then  added. 
Whilst  pure  nitric  acid  has  an  oxidising  action  only  at  high  temperatures,  crude  nitric 
•acid  begins  to  act  at  common  temperatures.  The  chief  reaction  sets  in  at  65°  and  is 
most  violent  at  70°,  declining  afterwards.  Hence,  at  the  outset  but  little  arsenic  is 
added ;  the  water-bath  is  then  heated  to  70°  by  turning  in  steam,  and  the  remainder  of 
the  arsenic  is  added  in  small  portions.  The  reaction  lasts  about  sixty  hours.  At  last 
the  heat  is  raised  and  the  end  of  the  process  is  ascertained  by  sampling.  A  small 
sample  is  heated  in  a  porcelain  capsule  with  a  little  arsenic,  over  a  spirit  or  gas  flame, 
and  if  only  traces  of  nitrous  fumes  escape  the  operation  is  broken  off.  The  mass  is 
allowed  to  cool  a  little,  and  it  is  then  drawn  with  syphons  out  of  the  generators,  A,  into 
the  neutralising  pan,  C.  If  the  mixture  from  all  the  six  generators  contains  any  free 
nitric  acid,  arsenic  is  added,  and  if  it  contains  an  excess  of  arsenious  acid,  nitric  acid  is 


452  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

added.  In  either  case  heat  is  applied  until  the  escape  of  gases  entirely  ceases.  The 
concentration  of  the  arsenic  acid  is  carried  to  195°  Tw.  A  continual  oversight  of  the 
generators  is  necessary  to  prevent  rising  over.  If  the  evolution  of  gases  is  very 
violent,  cold  water  is  run  from  the  pipe,  w,  into  the  vat,  If,  and  it  is  not  heated  again 
until  the  contents  are  quiet.  In  general  the  temperature  does  not  fluctuate  much,  as 
the  escape  of  gas  absorbs  the  more  heat  the  more  rapid  it  becomes.  Arsenic  must 
never  be  added  in  large  quantities  at  once.  As  much  air  enters  through  the  loose 
cover  as  is  needed  to  oxidise  the  nitrogen  oxides.  If  the  glass  tube,  g  (Fig.  367),  has 
a  yellow  colour  near  the  chimney,  there  is  either  too  little  air  in  the  pots,  B,  or  the 
reaction  in  A  is  too  violent.  With  careful  watching,  75  per  cent,  of  the  nitric  acid 
may  be  recovered. 

Besides  serving  for  the  production  of  magenta  (a  process  now  generally  superseded), 
sodium  arseniate  is  used  as  a  mordant  in  tissue  printing  and  in  turkey-red  dyeing.  It 
is  now  being  superseded  in  the  latter  industry  by  sodium  phosphate. 

Arsenic  acid  is  tested  by  dissolving  an  average  sample  in  a  solution  of  sodium  bicar- 
bonate and  titrating  with  solution  of  iodine.  It  has  been  already  stated  how  arsenic 
acid  is  tested  for  free  nitric  acid  or  arsenious  acid.  The  commercial  product  is  gener- 
ally valued  according  to  its  sp.  gr. 

COMPOUNDS   OF  GOLD,   SILVER,   AND   MERCURY. 

Cassius's  Purple,  Gold  Purple. — The  preparation  which  bears  this  name  was  dis- 
covered by  Dr.  Cassius,  at  Ley  den,  in  the  year  1663.  It  is  prepared  by  adding  to  a 
solution  of  gold  chloride  a  certain  quantity  of  tin  sesquichloride.  Dr.  Bolley  prescribes 
the  following  process : — First,  107  parts  of  the  double  tin  and  ammonium  chloride 
are  digested  with  pure  metallic  tin  until  the  metal  is  quite  dissolved ;  18  parts  of 
water  are  then  added,  and  the  liquid  mixed  with  the  gold  solution  previously  diluted 
with  36  parts  of  water.  The  result  is  the  throwing  down  of  a  purple  or  black  coloured 
precipitate,  about  the  chemical  constitution  of  which  nothing  is  certainly  known. 
Well-prepared  Cassius's  purple  should  contain  39*68  per  cent,  of  gold. 

Salts  of  Gold. — The  double  salts  of  gold  and  sodium  chloride  (AuCl3,NaCl  +  2H80), 
and  the  corresponding  potassium  salt  (2Au013,KCl  +  5H20),  are  employed  in  photo- 
graphy and  medicine. 

Salts  of  Silver,  Silver  Nitrate,  Lunar  Caustic. — This  salt  (AgN03)  is  now  pre- 
pared on  the  large  scale  by  dissolving  silver  containing  copper  in  nitric  acid,  evapo- 
rating the  solution  to  dryness,  and  igniting  the  residue  until  all  the  copper  nitrate  is 
decomposed.  The  residue  is  next  exhausted  with  pure  water,  the  solution  filtered  and 
left  to  crystallise.  For  medical  purposes  the  crystals  are  fused,  and,  while  liquid, 
poured  into  moulds  to  form  small  round  sticks.  The  most  extensive  use  of  silver 
nitrate  obtains  in  photography,  a  re-crystallised  neutral  and  pure  salt  being  preferred. 
Under  the  name  of  Sel  Clement,  there  is  now  in  use  in  photography  a  mixture  of  fused 
silver,  sodium  and  magnesium  nitrates,  recommended  as  preferable  to  silver  nitrate 
alone.  It  is  stated  that  the  consumption  of  this  salt  for  photographic  purposes 
amounted,  in  1870,  to  1400  cwts.  for  Germany,  France,  England,  and  the  United 
States ;  the  money  value  of  this  quantity  being  estimated  at  ^630,000. 

Marking  Ink. — A  large  quantity  of  silver  nitrate  is  also  used  for  the  purpose  of 
making  indelible  ink  for  marking  linen.  This  ink  often  consists  of  two  different  fluids, 
one  a  solution  of  pyrogallic  acid  in  a  mixture  of  water  and  alcohol,  being  intended  to 
moisten  the  linen  previous  to  writing  ;  the  other,  or  writing  fluid,  consisting  of  a  solu- 
tion of  ammoniacal  nitrate  of  silver  thickened  with  gum.  More  recently  aniline  black 
has  been  applied  in  the  marking  of  linen.* 

*  The  number  of  marking-inks  is  now  almost  endless,  and  many  of  them  corrode  linen. 


SECT,  in,]  COMPOUNDS  OF   MERCURY.  453 

Mercurial  Compounds. — The  more  important  mercurial  compounds  which  are  manu- 
factured on  the  large  scale  are  the  following  : — 

Mercuric  Oxide,  HgO,  is  prepared  by  cautiously  heating  a  mixture  of  mercuric 
nitrate  with  mercury.  It  is  sometimes  applied  to  the  iron  hulls  of  steamers  to  prevent 
the  attachment  of  mollusca,  &c. 

Mercuric  Chloride. — The  substance  commonly  known  as  corrosive  sublimate  is  the 
perchloride  of  mercury,  HgCl2,  molecular  weight  =135,  consisting,  in  100  parts,  of 
73'8  parts  of  mercury  and  z6'z  parts  of  chlorine.  It  is  prepared  either  by  sublima- 
tion from  a  mixture  of  mercuric  sulphate  and  common  salt,  or  by  dissolving  the 
same  oxide  in  hydrochloric  acid,  and  also  by  boiling  a  solution  of  magnesium  chloride 
with  the  peroxide  (MgCl2  -1-  HgO  =  HgCl2  +  MgO).  When  sublimed,  this  salt  forms  a 
white  crystalline  mass,  which  fuses  at  260°,  boils  at  290°,  is  soluble  in  13-5  parts 
of  water  at  20°,  and  in  r85  parts  of  the  same  liquid  at  100°.  It  is  more  readily 
dissolved  by  alcohol,  i  part  of  the  salt  requiring  only  2-3  parts  of  cold  and  i'i8  parts 
of  boiling  alcohol.  Mercuric  chloride  has  been  industrially  employed  as  a  preservative 
for  timber  by  Kyan,  and  is  used  in  the  manufacture  of  aniline-red,  in  dyeing 
and  calico-printing,  in  etching  on  steel-plates,  and  for  the  preparation  of  other 
mercurial  salts.  Lately,  the  use  of  the  double  salt,  HgCl2,2KCl,  obtained  by  boiling 
potassium  chloride  with  mercury  peroxide,  has  been  suggested  as  a  preservative 
for  timber.  It  should  be  borne  in  mind  that  this  preparation  of  mercury  is  extremely 
poisonous  and  easily  absorbed  by  the  skin  of  the  hands. 

Cinnabar  or  Vermilion. — Under  this  name  is  designated  the  mercuric  sulphide, 
HgS,  which  occurs  native  in  crystalline  or  compact  red-coloured  masses,  and  was  known 
in  Pliny's  time  by  the  term  minium.*  The  use  of  mercuric  chloride  in  the  manufac- 
ture of  aniline  red,  and  in  dyeing  and  printing,  has  practically  ceased.  The  cinnabar, 
or  vermilion  of  commerce,  used  as  a  pigment,  is  always  artificially  prepared  either  by  the 
dry  or  wet  way.  By  the  former  process  540  parts  of  mercury  and  75  of  sulphur  are  very 
intimately  mixed.  The  ensuing  black-coloured  powder  is  introduced  into  iron  vessels,  and 
•exposed  to  a  moderate  heat  so  as  to  cause  the  fusion  of  the  mass,  which,  after  cooling,  is 
broken  up  and  then  introduced  into  earthenware  and  loosely  closed  vessels,  heated  on  a 
sand-bath.  The  sublimed  mass  is  of  a  cochineal-red  colour,  exhibits  a  fibrous  fracture, 
and  yields  when  pulverised  a  scarlet  powder,  which  is  the  more  beautiful  the  purer  the 
materials  used  in  its  preparation  and  the  greater  the  care  taken  to  avoid  an  excess  of 
sulphur.  Some  chemists  allege  that  a  greatly  improved  vermilion  is  obtained  if  i  part 
of  antimony  sulphide  is  added  to  the  mixture  of  sulphur  and  mercury  previously  to 
the  sublimation,  and  the  sublimed  and  pulverised  mass  placed  in  a  dark  room  for 
several  months  and  treated  with  either  dilute  nitric  acid  or  caustic  potassa.  Accord- 
ing to  Liebig,  vermilion  is  obtained  in  the  wet  process  by  treating  the  white 
precipitate  of  the  Pharmacopoeia,  or  hydrargyrum  amidato  bichloratwm,  with  a  solu- 
tion of  sulphur  in  ammonium  sulphide.  Hofmann  considers  white  precipitate  to  be 
ammonium  chloride,  in  the  ammonium  of  which  2  equivalents  of  mercury  have 

,TT 

taken  the  place  of  2   equivalents  of  hydrogen;    formula    NJ-rA       Other   chemists, 

*••"•&»• 

again,  hold  different  views  as  to  the  constitution  of  this  body,  which  has  been  used 
in  medicine  since,  if  not  before,  the  time  of  Paracelsus.  Vermilion  is  generally 
•obtained  by  precipitating  a  solution  of  corrosive  sublimate  in  ammonia  with  a 
solution  of  sulphur  in  ammonium  sulphide;  or,  according  to  Martius,  by  agi- 
tating, in  a  suitable  vessel,  i  part  of  sulphur  of  mercury,  and  2  to  3  of  a  con- 
centrated solution  of  liver  of  sulphur.  According  to  Brunner's  method,  by  which 
decidedly  the  finest  vermilion  is  obtained,  114  parts  by  weight  of  sulphur  and  300 

*  Bed  lead,  afterwards  called  minium,  was,  as  far  as  it  appears,  unknown  to  the  ancients,  being 
first  prepared  by  the  Arabs  and  Saracens. 


454  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

parts  by  weight  of  mercury  are  mixed,  with  the  addition  of  a  small  quantity  of  caustic 
potassa  solution,  and  incorporated  by  being  shaken  by  machinery.  The  resulting 
black  compound  is  next  treated  with  a  solution  of  75  parts  caustic  potassa  in  400  parts 
of  water,  and  heated  on  a  water-bath  to  45°.  The  mixture  assumes  a  scarlet-colour 
after  a  few  hours,  and  as  soon  as  this  is  apparent  the  semi-liquid  mass  is  poured  into 
cold  water,  next  collected  on  niters,  washed,  and  dried.  The  vermilion  of  commerce 
is  often  adulterated  with  red  lead,  iron  peroxide,  chrome  lead,  and,  more  frequently, 
with  from  15  to  20  per  cent,  of  gypsum.  These  adulterations  are,  however,  readily 
detected,  as  they  are  left  behind  when  the  vermilion  is  sublimed.  Red  lead,  one  of 
the  most  usual  adulterations  of  vermilion,  can  be  readily  detected  either  by  treating  a 
small  quantity  of  the  suspected  sample  with  nitric  acid,  when,  in  consequence  of  the 
formation  of  puce-coloured  lead  peroxide,  the  mass  assumes  a  brown  colour,  or  by 
the  addition  of  hydrochloric  acid,  when  chlorine  is  given  off.  Pure  cinnabar  is  com- 
pletely and  readily  soluble  in  hydrosulphuret  of  sodium  sulphide  (NaSH). 

Red  lead,  or  antimonial  cinnabar,  is  sometimes  passed  off  as  vermilion  by  steeping 
it  in  a  solution  of  eosine.  If  such  a  sample  is  digested  in  alcohol,  the  cosine  is  dissolved 
away,  and  the  red  lead,  &c.,  is  revealed. 

COMPOUNDS  OF   COPPEE. 

Copper  Sulphate,  Blue  Vitriol,  Blue  Stone.— This  salt  is  met  with  naturally  in 
kidney-shaped  masses,  or  as  an  outer  covering  of  minerals  containing  copper,  as 
well  as  in  solution,  as  referred  to  under  Cementation-copper.  Copper  sulphate,  blue- 
or  Cyprus-vitriol  crystallises  in  the  shape  of  triclinohedrical  blue-coloured  crystals, 
soluble  in  two  parts  of  hot  and  four  of  cold  water,  and  insoluble  in  alcohol.  100  parts 
of  the  salt  contain — 

Sulphuric  acid          .         .         .     32-14 
Oxide  of  copper        .         .         .3179 

Water 36-07 

Formula— CuS04  +  sH20. 

Preparation  of  Blue  Vitriol. — Pure  copper  sulphate  is  obtained  by  heating  metallic 
copper  with  concentrated  sulphuric  acid ;  the  metal  is  oxidised  by  a  portion  of  the 
oxygen  of  the  acid,  while  sulphurous  acid  escapes  : 

(Cu  +  2H2S04  =  CuS04  +  2H20  +  SO,). 

If  the  metal  is  previously  converted  into  copper  oxide  by  exposure  to  a  red  heat, 
only  half  the  quantity  of  sulphuric  acid  is  required.  Copper  sulphate  is  manu- 
factured on  a  large  scale  by  any  of  the  following  processes ; — i.  By  the  evaporation  of 
cementation  water  until  crystallisation  is  attained.  2.  By  heating  sheets  of  copper  in 
a  reverberatory  furnace  to  the  boiling-point  of  sulphur  ;  a  quantity  of  that  element 
being  then  thrown  in,  and  the  flues  and  other  openings  closed,  the  effect  is  the  forma- 
tion of  copper  sulphide  (Cu2S),  which  is  converted  by  a  comparatively  low  heat  and 
the  action  of  the  oxygen  of  the  air  into  sulphate  (Cu2S  +  50  =  CuS04  +  CuO).  The 
mass  is  next  placed  in  a  suitable  vessel,  and  as  much  sulphuric  acid  is  added  to  it  as 
is  sufficient  to  saturate  the  oxide  of  copper.  The  clear  solution,  having  been  decanted 
from  the  insoluble  residue,  is  set  aside  for  crystallisation.  3.  By  treating  the  crude 
copper  obtained  by  smelting  the  ores,  and  containing  about  60  per  cent,  of  metal, 
with  sulphuric  acid.  The  resulting  solution  is  evaporated  in  leaden  vessels,  and  the 
clear  liquid  left  to  crystallise  in  copper  pans.  From  the  mother  liquor  of  the  crystals- 
metallic  copper  is  precipitated  by  means  of  iron,  because  the  presence  of  a  large- 
quantity  of  iron  sulphate  renders  this  mother  liquor  unfit  for  the  further  making 
of  blue  vitriol.  This  method  of  obtaining  copper  sulphate  is  the  least  expensive,. 


SECT,  m.]  COMPOUNDS  OF  COPPER.  455 

but  the  salt  is  not  quite  pure,  containing,  according  to  M.  Herter  s  analysis  of  Mans- 
feld  blue  vitriol,  about  3  per  cent,  of  iron  sulphate,  and  0*083  per  cent,  of  metallic 
nickel.  Very  frequently  the  scraps  and  refuse  of  copper-smithies,  copper-scale,  and 
other  residues  of  that  metal,  are  used  in  preparing  copper  sulphate.  4.  At  Mar- 
seilles, malachite  is  dissolved  in  sulphuric  acid  to  obtain  blue  vitriol.  5.  In  Norway, 
iron  pyrites  containing  copper  are  roasted  and  treated  with  water,  the  copper  con- 
tained being  precipitated  with  sulphuretted  hydrogen,  and  the  copper  sulphide, 
when  dry,  converted  into  sulphate  by  exposure  to  a  gentle  heat.  6.  Large  quantities 
of  copper  sulphate  are  obtained  as  a  bye-product  of  silver-refining  (especially  when 
silver  is  treated  for  the  purpose  of  extracting  the  gold  it  contains),  by  boiling — usually 
silver  coins,  chiefly  Mexican  and  Peruvian  dollars — with  strong  sulphuric  acid  ;  silver 
sulphate  and,  as  the  coins  contain  some  copper,  the  sulphate  of  that  metal,  are 
formed,  while  the  gold  is  left  as  an  insoluble  substance.  The  silver  is  reduced  to  the 
metallic  state  (Ag2S04  +  Cu  =  CuS04  +  2 Ag)  by  means  of  sheets  of  copper  placed  in  the 
acid  solution,  which  is  previously  diluted,  and  which,  after  having  been  decanted  from 
the  sediment  of  spongy  metallic  silver,  yields  on  evaporation  a  very  pure  copper  sul- 
phate. 7.  Copper  sulphate  is  also  obtained  as  a  bye-product  of  the  hydrometallur- 
gical  process  of  extracting  silver,  or  Ziervogel's  process.  In  order  to  separate  the  iron 
sulphate  from  the  crude  blue  vitriol,  as  obtained  at  copper-smelting  works  from 
various  cupriferous  refuse,  the  crude  salt  is  roasted  so  as  to  bring  about  a  partial  de- 
composition. By  this  means  the  irons  ulphate  is  decomposed,  and  the  oxide  of  that 
metal  formed  is  insoluble  in  water.  The  saline  mass  is  dissolved  in  water,  and  the 
clear  solution,  decanted  from  the  sediment,  evaporated  to  crystallisation.  According 
to  Bacco's  plan,  the  crude  blue-vitriol  is  dissolved  in  water,  and  copper  carbonate 
added  to  the  solution,  to  cause  the  precipitation  as  oxide  of  all  the  iron  present,  while 
an  equivalent  quantity  of  copper  oxide  is  dissolved  and  converted  into  sulphate. 
The  purified  copper  sulphate  solution  having  been  filtered  is  evaporated  and  left  to 
crystallise. 

Double  Vitriol. — Under  the  name  of  double  vitriol,  a  mixture  of  the  copper  and 
iron  sulphates  crystallised  together,  and  sometimes  containing  white  vitriol,  is  met 
with  on  the  Continent.  The  Salzburg  vitriol,  known  by  the  brand  of  a  double  eagle, 
contains  about  76  per  cent.,  the  Admont  83  per  cent.,  and  the  double  Admont  80  per 
cent,  of  ferrous  sulphate.  Of  later  years,  however,  these  vitriols  have  been  less  in 
demand. 

Applications  of  Blue  Vitriol. — As  the  base  of  the  pigments  obtainable  from  copper, 
the  sulphate  is  very  frequently  used,  and  should  be  pure,  or  at  least  free  from  iron 
and  zinc  sulphates.  Blue  vitriol  also  serves  for  the  manufacture  of  copper  acetate, 
for  bronzing  iron,  for  bringing  out  the  colour  of  alloys  of  gold.  It  is  used  in 
dyeing  and  printing  in  various  ways,  for  gal vano- plastic  purposes,  and  during  the  last 
twenty  years  large  quantities  of  this  salt  have  been  sent  to  Mexico  and  Peru  to  be 
applied  in  the  American  amalgamation-process  of  extracting  silver. 

Copper  Pigments. — (Brunswick  Green,  Bremen  Blue  or  Green,  Casselmanris  Green, 
Scheele's  Green,  Oil  Blue,  Schweinfurt  Green,  Verdigris.). — Brunswick  Green. — Under 
this  name  several  compounds  of  copper  are  applied  as  oil-paints.  The  pigment  now 
chiefly  in  use  bearing  this  name  is  basic  copper  carbonate  (CuC03  +  CuH2O2),  an 
imitation  of  mountain-  or  mineral-green,  and  obtained  from  either  finely  pulverised 
malachite  or  the  sediment  often  met  with  in  cupriferous  cementation  liquids.  Bruns- 
wick green  is  prepared  on  a  large  scale  by  the  decomposition  of  ferrous  sulphate 
by  means  of  either  sodium  or  calcium  carbonate,  and  in  other  cases  by  the 
decomposition  of  copper  chloride  by  means  of  a  carbonated  alkali.  The  ensuing 
precipitate  is  washed  with  boiling  water,  and  afterwards  mixed  with  a  smaller  or  larger 
quantity  of  barium  sulphate,  zinc- white,  or  gypsum,  and  frequently  with  Schweinfurt 


456  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

green  (copper  aceto-arsenite)  in  order  to  obtain  the  desired  hue.  Another  variety  of 
Brunswick  green,  rarely  met  with  in  the  present  day,  appears  to  be  a  kind  of  artificially 
prepared  atacamite,  a  copper  oxychloride,  the  formula  of  which  is,  according  to  Eitt- 
hausen,  CuCl2.3Cu(HO)2. 

Bremen  Blue  or  Bremen  Green. — These  substances  are  essentially  hydrated  copper 
oxide,  and  are  met  with  as  a  very  bright  spongy  blue  mass  with  a  greenish  hue.  The 
value  is  greater  according  to  the  finer  blue  colour  and  loose  spongy  texture.  When  used 
with  water,  gum,  or  glue,  this  pigment  yields  a  bright  blue  colour,  hence  its  first  name  ; 
but  when  it  is  mixed  with  linseed  oil,  the  blue  colour  turns  within  twenty-four  hours  to 
green,  in  consequence  of  the  saponification  of  the  copper  oxide,  which  becomes  oleate, 
palmitate,  and  linoleate  of  that  base.  Bremen  green  occurs  in  various  hues,  obtained 
by  mixing  the  precipitate  with  well-cleansed  gypsum.  At  the  present  time  the  pig- 
ment is  generally  obtained  from  copper  oxychloride  (CuCl23CuO  +  4.H20).  This  pre- 
paration may  be  made  in  various  ways,  provided  care  be  taken  that  the  light  green 
paste — technically  known  as  oxide — contains  no  cuprous  chloride  (CuCl2).  Gentele's 
method  is  as  follows  : 

i.  1 1 2 '5  kilos,  of  common  salt,  and  in  kilos,  of  copper  sulphate,  both  free  from 
iron,  are  ground  together  with  sufficient  water  to  promote  reaction.  2.  112*5  kilos,  of 
old  copper  sheeting  is  cut  into  pieces  a  square  inch  in  size,  and  placed  with  water 
acidulated  with  sulphuric  acid  in  rotating  casks  so  as  to  remove  all  rust,  oxide,  and 
oxychloride  from  this  metal,  which  is  next  washed  with  water.  3.  The  clean  metal  thus 
obtained  is  next  placed  in  what  are  known  as  oxidisation-closets  and  covered  for  a  thick- 
ness of  half  an  inch  with  the  paste  mentioned  above.  A  mutual  action,  aided  by  that  of 
the  atmosphere,  is  set  up,  the  result  being  that  the  copper  chloride  first  takes  up  copper, 
becoming  cuprous  chloride ;  this  in  its  turn  takes  up  oxygen  from  the  atmosphere 
and  water,  and  thus  becomes  converted  into  the  green-coloured  insoluble  hydrated  copper 
oxide,  the  action  being  greatly  aided  by  the  turning  over  of  the  mass  with  a  copper 
spade  every  two  or  three  days.  As  the  treatment  of  cuprous  chloride  with  alkalies 
or  alkaline  earths  gives  rise  to  the  separation  of  red  or  yellow  coloured  suboxide, 
the  mass  should  not,  on  being  tested  and  previous  to  further  operations,  yield 
even  the  faintest  indication  of  the  presence  of  suboxide,  since  the  slightest  trace 
would  spoil  the  hue  of  the  pigment  to  be  obtained ;  consequently,  in  some  works 
the  pasty  mass  is  left  for  years  before  it  is  used  for  further  operations.  The  action  is 
accelerated  by  causing  the  mass  to  become  dry  before  turning  it  over  with  a  spade,  the 
consequence  being  that  the  air  gets  thorough  access,  and  a  complete  oxidation  is 
obtained  in  from  three  to  five  months'  time.  The  mass  is  then  cleaned  with  the 
smallest  possible  quantity  of  water,  and  is  thus  separated  from  the  non-oxidised  metallic 
copper.  4.  To  about  6  gallons  of  this  cleaned  material  are  added  6  kilos,  of  hydrochloric 
acid,  and  this  mixture  is  allowed  to  stand  for  about  two  days.  5.  Into  a  tank  or  tub 
— the  blue  tub — are  poured  1 5  gallons  of  clear  colourless  potassa  lye.  This  having  been 
done,  the  acid  mixture  is  first  diluted  with  6  more  gallons  of  .water,  and  then,  as 
rapidly  and  expeditiously  as  possible,  poured  into  the  blue  tub,  the  mixture  being 
continuously  stirred.  The  result  of  this  last  operation  is  that  the  previously  basic 
copper  compound,  converted  by  HC1  into  neutral  cupric  chloride,  is,  when  brought 
in  contact  with  the  potassa,  converted  into  blue-coloured  copper  oxyhydrate  or 
Bremen  blue,  while  potassium  chloride  is  also  formed.  6.  After  the  mass  has 
become  pasty,  it  is  left  to  stand  for  a  couple  of  days,  and  then  thoroughly  washed  by 
decantation  to  remove  the  potassium  chloride.  The  cupric  oxyhydrate  is  then  put 
on  cloth  filters,  kept  moist,  and  exposed  to  the  air  for  some  time.  It  is  next  dried  at  a 
temperature  of  from  30°  to  35°,  since  at  a  higher  temperature  the  hydrate  of  the  oxide  by 
losing  its  water  becomes  blackish-brown  coloured.  It  is  clear  that  Bremen  blue  can  be 
differently  obtained,  but  these  differences  of  preparation  do  not  bear  so  much  upon  the 


SECT,  m.]  COMPOUNDS  OF   COPPER.  457 

precipitation  of  the  hydrated  oxide  as  upon  the  means  of  obtaining  copper  chloride ; 
these  means  may  of  course  be  varied  in  many  ways  ;  for  instance,  by  causing  a  mixture 
of  common  salt,  dilute  sulphuric  acid,  and  copper  scraps  to  act  upon  each  other,  the  mass 
being  afterwards  exposed  to  the  action  of  the  air ;  by  the  action  of  hydrochloric  acid 
upon  copper  and  its  oxide  ;  or  by  partly  decomposing  neutral  copper  nitrate  by  means 
of  sodium  carbonate.  In  this  case  a  precipitate  of  copper  carbonate  is  formed,  which 
while  giving  off  its  carbonic  acid,  becomes  converted  into  a  basic  copper  nitrate 
(CuN306  +  CuH8Oj),  deposited  as  a  heavy  green  powder.  A  solution  of  zinc-oxide  of 
potassa  (solution  of  zinc- white  in  caustic  potassa)  is  next  added,  the  result  being  the 
formation  of  a  deep  blue  pigment,  very  spongy  and  very  covering  (a  technical  term  in 
use  by  painters),  consisting  of  copper  zincate  with  a  small  quantity  of  basic  copper 
nitrate.  A  magnesia  Bremen  blue  is  obtained  by  the  precipitation  of  a  solution  of 
the  magnesium  and  copper  sulphates,  to  which  some  cream  of  tartar  is  added  by  means 
of  potassa,  care  being  taken  to  pour  the  saline  solution  into  the  alkaline,  and  to  keep 
an  excess  of  the  latter. 

Casselmann's  Green. — Dr.  Casselmann  discovered  this  pigment,  a  beautiful  green 
free  from  arsenic.  It  is  prepared  by  mixing  together  boiling  solutions  of  copper 
sulphate  and  an  alkaline  acetate ;  the  resulting  precipitate  is  a  basic  salt  of 
copper  (CuS04  +  3CuH202  +  4H20).  After  drying,  this  salt  is,  next  to  Schweinfurt 
green,  the  finest  of  all  colours  obtained  from  copper,  and  being  free  from  arsenic,  is 
highly  commendable,  though  poisonous,  like  most  preparations  of  copper,  especially 
the  acetates. 

Mineral  Green  and  Blue. — This  pigment,  also  known  as  Scheele's  green,  is  not  so 
frequently  used  now  as  formerly.  It  is  essentially  a  mixture  of  hydrated  copper 
oxide  and  arsenite,  and  does  not  cover  very  well.  It  is  prepared  by  dissolving  i  kilo, 
of  pure  copper  sulphate  in  12  litres  of  water,  to  which  is  added,  with  constant 
stirring,  a  solution  of  350  grammes  of  arsenious  acid  and  i  kilo,  of  purified  potash 
(carbonate)  in  8  litres  of  water.  The  resulting  grass-green  coloured  precipitate 
is  washed  with  boiling  water  and  dried.  Another  pigment,  sometimes  known  as 
mineral  green,  is  obtained  from  malachite,  or  basic  hydrated  copper  oxide.  By  the 
term  mineral  blue  is  generally  understood  a  kind  of  Berlin  blue,  rendered  less  deep 
coloured  by  the  addition  of  pipe-clay  or  other  white-coloured  powders,  but  the  terms 
also  applies  to  a  pigment  formerly  obtained  by  grinding  and  washing  the  purest  pieces 
of  copper  lazulite,  a  mineral  (2CuCOs+  CuH202)  found  in  the  Tyrol  and  near  Lyons. 
This  pigment  is  artificially  obtained  in  France,  Holland,  and  Belgium,  by  precipitating 
a  solution  of  copper  nitrate  with  caustic  lime  or  caustic  potassa,  and  afterwards  mix- 
ing the  previously  washed  precipitate  with  chalk,  gypsum,  or  heavy  spar.  The  pig- 
ment is  sent  into  the  trade  for  use  chiefly  as  a  water-colour.  Under  the  name  of  lime 
blue  a  similar  preparation  occurs  in  quadrangular  lumps,  obtained  by  precipitating  a 
solution  of  100  parts  of  copper  sulphate  and  12^  parts  of  sal-ammoniac  with  a  milk  of 
lime  containing  30  parts  of  caustic  lime.  The  precipitate  is  a  mixture  of  hydrated 
copper  oxide  and  calcium  sulphate,  according  to  the  formula,  2CaS04.2H2O  +  3CuOHr 
This  pigment  exhibits  a  purer  tint  than  Bremen  blue,  but  though  it  covers  pretty  well 
as  a  water-colour,  it  is  almost  useless  as  an  oil-colour. 

Oil  Blue. — A  pigment  which,  when  ground  with  oils  and  varnishes,  yields  a  beau- 
tiful violet-blue,  and  is  essentially  composed  of  copper  sulphide,  (CuS),  there  being 
employed  in  its  manufacture  either  the  native  mineral,  known  as  cupreous  indigo,  or  an 
artificially  prepared  sulphide,  obtained  by  fusing  finely  divided  metallic  copper  with 
hepar  sulphuris,  a  mixture  of  several  potassium  sulphides.  The  fused  mass  is 
treated  with  water,  and  the  copper  sulphide  remains  in  small  blue-coloured  crystals, 
which,  after  drying,  are  pulverised  and  mixed  with  oil. 

Schweinfurt  Green  or  Emerald  Green. — This  pigment  is  by  far  the  most  beautiful,  but 


458  CHEMICAL   TECHNOLOGY.  [SECT.  m. 

also  the  most  poisonous,  of  all  green-coloured  copper  pigments.  In  Germany  this 
substance  is  known  under  a  number  of  aliases  derived  from  the  peculiar  depth  of  hue 
as  modified  in  various  manufactories  by  means  of  barium  sulphate,  lead  sulphate,  and 
chrome-yellow.  The  constitution  and  mode  of  preparation  of  this  pigment  remained, 
at  least  on  the  Continent,  a  trade  secret,  until  the  researches  of  MM.  Braconnot  and 
Liebig  made  the  particulars  known.  According  to  Ehrmann,  pure  emerald  or  Schwein- 
furt  green  is  a  copper  aceto-arsenite,  Cu(C,H3O2)2.3Cu(As02)2;  in  100  parts — oxide 
of  copper,  31*29 ;  arsenious  acid,  58'65  ;  acetic  acid,  io-o6.  Wagner  states  that 
this  formula  is  only  empirical,  because  a  portion  of  the  copper  is  present  as  suboxide, 
and  a  portion  of  the  arsenic  as  arsenic  acid. 

According  to  Ehrmann's  statement,  this  pigment  is  prepared  by  first  separately 
dissolving  equal  parts  by  weight  of  arsenious  acid  and  neutral  copper  acetate  in 
boiling  water,  and  next  mixing  these  solutions  while  boiling.  There  is  immediately 
formed  a  flocculent  olive-green  coloured  precipitate  of  copper  arsenite,  while  the 
supernatant  liquid  contains  free  acetic  acid.  After  a  while  the  precipitate  becomes 
gradually  crystalline,  at  the  same  time  forming  a  beautifully  green  pigment,  which  is 
separated  from  the  liquid  by  filtration,  and  after  washing  and  carefully  drying  is 
ready  for  use.  The  mode  of  preparing  this  pigment  on  a  large  scale  was  originally 
devised  by  Braconnot,  as  follows: — 15  kilos,  of  copper  sulphate  are  dissolved  in  the 
smallest  possible  quantity  of  boiling  water  and  mixed  with  a  boiling  and  concen- 
trated solution  of  sodium  or  potassium  arsenite,  so  prepared  as  to  contain  20  kilos,  of 
arsenious  acid.  There  is  immediately  formed  a  dirty  greenish-coloured  precipitate, 
which  is  converted  into  Schweinf urt  green  by  the  addition  of  some  1 5  litres  of  concen- 
trated wood  vinegar.  This  having  been  done,  the  precipitate  is  immediately  filtered 
off  and  washed.  It  thus  appears  that  the  preparation  of  this  pigment  aims  first  at 
the  least  expensive  preparation  of  neutral  copper  arsenite,  which  is  next  converted 
into  aceto-arsenite  by  digesting  the  precipitate  with  acetic  acid.  The  pigment  is 
available  as  a  water-  and  an  oil-colour,  but  does  not  cover  very  well  in  oil,  although  it 
dries  rapidly.  The  colour  cannot  be  used  for  mural  painting,  as  the  lime  absorbs  the 
acetic  acid,  leaving  a  yellowish-green  copper  arsenite.  The  Schweinfurt  green  consists 
of  microscopically  small  crystals ;  if  these  crystals  are  pulverised,  the  colour,  previously 
grass-green,  becomes  paler.  Air  and  light  do  not  affect  this  pigment,  which  is  insoluble 
in  water,  but  becoming,  when  boiled  with  it  for  a  length  of  time,  brown-coloured, 
probably  in  consequence  of  the  loss  of  some  acetic  acid.  It  is  a  well-known  fact  that 
paper-hangings  containing  this  pigment,  and  pasted  on  damp  walls,  cause  the  inmates 
of  the  rooms  to  suffer  from  headaches,  due  in  all  likelihood  to  volatile  arsenical 
emanations,  among  which  is  hydrogen  arsenide.  The  use  of  this  pigment  is  very 
limited. 

Copper  Stannate. — This  preparation,  also  known  as  Gentele's  green,  is  obtained  by 
precipitating  a  solution  of  copper  sulphate  with  sodium  stannate,  washing  and  drying 
the  precipitate,  which  forms  a  beautifully  green  copper  pigment,  innocuous,  at  least  as 
compared  with  the  foregoing. 

Verdigris. — Under  this  name  we  meet  in  commerce  with  a  neutral  and  a  basic 
copper  acetate ;  the  one,  a  crystalline  substance,  is  Cu(C2H302)2.H2O,  a  salt  formerly 
only  prepared  in  Holland,  and  designated  as  "  distilled  verdigris,"  in  order  to  mislead 
as  to  its  mode  of  manufacture. 

The  basic  salt,  blue  verdigris,  is  chiefly  prepared  at  and  near  Montpellier,  by  em- 
ploying the  marc  of  grapes,  the  skin  and  stems  of  the  bunches  after  the  juice  has 
been  squeezed  out,  which  readily  forms  acetic  acid  by  fermentation.  Into  the  marc 
are  placed  sheets  of  copper  previously  moistened  with  a  solution  of  copper  acetate. 
The  metal  becomes  coated  with  a  layer  of  verdigris,  which  is  removed  by  scraping.  It 
is  next  kneaded  with  water,  after  which  the  paste  is  put  into  leathern  bags  and  pressed,. 


SECT,  in.]  COMPOUNDS   OF  ZINC   AND   CADMIUM.  459 

so  as  to  obtain  rectangular  cakes.  The  metal  is  again  treated  in  the  same  manner  until 
it  is  entirely  converted  into  basic  verdigris,  having  a  blue  colour,  and  known  as  French 
verdigris.  Formula — Cu(C2HsO2)2.Cu(OH)2.5H2O.  A  green-coloured  verdigris  is 
obtained  at  Grenoble  and  elsewhere  by  submitting  sheets  of  copper  to  the  action 
of  vapours  of  vinegar,  or  by  placing  the  metal  between  pieces  of  coarse  flannel, 
soaked  with  that  liquid  in  a  warm  place.  The  formula  of  the  substance  thus  pro- 
duced is— Cu(C2H3O2)2.2Cu(OH)2. 

Neutral  copper  acetate  first  made  by  the  Saracens  in  Southern  Spain,  and  since  the 
middle  of  the  fifteenth  century  by  the  Dutch,  is  now  obtained  either  by — i.  Dis- 
solving the  basic  salt  in  acetic  acid.  2.  Or  by  the  double  decomposition  of  copper 
sulphate  and  lead  acetate  :— CuSO4  +  Pb(C2H302)2  =  PbS04  +  Cu(C2H302)2. 

By  the  first  method  the  basic  acetate  is  dissolved  in  4  parts  of  acetum  destillatum 
(purified  vinegar)  or  in  wood  vinegar,  the  liquid  being  placed  in  a  copper  cauldron  and 
heat  applied.  The  clear  liquid  is  decanted,  and  then  evaporated  in  copper  pans  until  a 
saline  crust  makes  its  appearance,  when  the  fluid  is  transferred  to  wooden  vessels  pro- 
vided with  thin  laths  serving  as  a  solid  nucleus  for  the  crystals.  According  to  the  second 
plan,  the  solutions  of  the  two  salts  are  mixed,  the  liquid  decanted  from  the  sediment  of 
lead  sulphate,  and  next  evaporated,  after  the  addition  of  some  acetic  acid,  until  a  crust 
of  the  salt  is  formed.  Instead  of  lead  acetate,  the  calcium  and  barium  acetates  are  now 
used.  The  neutral  copper  acetate  is  met  with  in  commerce  in  "  bunches"  (grappes), 
consisting  of  deep  green-coloured,  non-transparent  crystals,  soluble  in  13-4  parts  of  cold, 
in  5  parts  of  hot  water,  and  in  14  parts  of  boiling  alcohol.  This  salt,  like  the  basic  ace- 
tates, is  highly  poisonous. 

Applications  of  Verdigris. — Both  basic  and  neutral  are  employed  as  oil-  and  water- 
colours.  In  Eussia,  verdigris,  mixed  with  white:lead,  is  frequently  used  as  an  oil 
paint,  the  result  being  the  formation  of  copper  carbonate  and  basic  lead  acetate. 
The  former  of  these  substances  yields  with  the  undecomposed  white-lead  a  bright  blue 
colour,  which,  after  painting,  turns  to  a  peculiarly  fine  green,  the  usual  colour  of  the 
iron  roofs  of  the  houses  in  Russia,  more  especially  in  Moscow  and  the  interior  of 
the  country.  In  Holland  the  same  mixture  is  frequently  applied  as  a  paint  to  out- 
door woodwork,  of  which  it  is  an  excellent  preservative.  Verdigris  is  sometimes 
further  applied  in  the  preparation  of  other  copper  colours — for  instance,  Schwein- 
furt  green ;  also  in  dyeing  and  calico-printing,  though  less  commonly  than  formerly ; 
in  gilding  (see  Gold).  The  neutral  salt  was  formerly  used  in  the  preparation  of  acetic 
acid. 

Egyptian  Slue,  a  blue  pigment  known  to  the  Egyptians  from  time  immemorial, 
and  lately  rediscovered,  is  obtained  by  fritting  a  mixture  of  sand  (free  from  iron)  70 
parts,  copper  oxide  15  parts,  chalk  25  parts,  and  sodium  carbonate  6  parts.* 

COMPOUNDS   OF   ZINC   AND   CADMIUM. 

Zinc- white. — Under  this  name  there  has  during  the  last  fourteen  years  been 
brought  into  the  market  anhydrous  white  zinc  oxide,  applied  instead  of  white-lead 
as  a  pigment.  Zinc-white  is  prepared  for  this  purpose  by  oxidising  metallic  zinc  in 
fireclay  retorts,  placed  to  the  number  of  8  to  1 8  in  a  reverberatory  furnace.  As 
soon  as  these  retorts  are  at  a  bright  white-heat,  cakes  of  zinc  are  placed  in  them,  and 
the  vapours  of  the  metal  on  leaving  the  retort  are  brought  into  contact  with  a  current  of 
air  heated  to  300° ;  oxidation  results,  and  the  oxide,  a  very  loose,  snow-white,  flocculent 
material,  is  carried  by  the  current  of  hot  air  into  condensing  chambers,  and  gradually 

*  Concerning  these  preparations  and  pigments,  the  reader  may  consult,  A.  H.  Church,  Chemistry 
of  Paints  and  Painting,  London,  Seeley  &  Co.;  and  Gentele,  Lehrbuch  der  Farbenfabrikation,  Bruns- 
wick, Vieweg  &  Son. 


460  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

4 

deposited.  The  oxide  thus  prepared  is  immediately  fit  for  use  ;  it  is  of  a  pure  white  colour, 
and  very  light.  Zinc- white  is  also  prepared  by  exposing  metallic  zinc  to  the  action  of 
superheated  steam,  hydrogen  being  at  the  same  time  evolved,  and  used  for  illuminating 
purposes,  as  at  Narbonne,  St.  Chinian,  Ceret,  and  a  few  other  places,  where  it  is  known 
as  platinum-gas,  because  the  flame  is  used  for  imparting  a  white  heat  to  small  coils  of 
platinum  wire,  thus  producing  a  very  steady  and  highly  pleasant  light.  As  regards 
the  use  of  zinc- white  as  a  pigment,  it  is  rather  more  expensive  than  white-lead,  yet 
according  to  some  it  is  a  better  covering  material  in  the  surface  proportion  of  10  to  13, 
that  is  to  say,  13  parts  by  weight  of  zinc- white  cover  as  much  space  as  10  of  white-lead : 
moreover,  zinc- white  is  i-.ot  affected  by  sulphuretted  hydrogen.  Like  white-lead,  this 
compound  may  be  mixed  with  other  pigments.  By  mixing  Rinmann's  green  with 
it  a  green  colour  may  be  obtained ;  blue  with  ultramarine ;  lemon-yellow  with  cadmium 
orange- yellow  (cadmium  sulphide). 

A  zinc  carbonate  has  been  proposed  as  a  pigment ;  it  is  prepared  by  precipitating 
solution  of  zinc  sulphate  with  ammonium  carbonate. 

Zinc-white  is  often  prepared  directly  from  its  ores  ;  the  roasted  ores  are  heated  upon 
the  grate  of  a  furnace  and  when  fully  ignited  submitted  to  a  current  of  air  passed 
underneath  the  grate.  The  escaping  vapours  are  again  strongly  heated  along  with 
a  current  of  air  and  condensed  in  lead  chambers.  Schnabel  digests  zinc  dust  with 
ammonium  carbonate  in  leaden  vessels.  The  great  advantage  of  zinc-white  is  that  it  is 
not  blackened  by  sulphur-gases,  and  that  it  is  less  injurious  to  workmen  than  white 
lead. 

White  Vitriol,  Zinc  Sulphate. — Zinc- vitriol  (ZnS04  +  7H2O),  zinc  sulphate  or 
white  vitriol,  is  found  as  a  native  mineral,  as  a  product  of  the  oxidation  of  zinc  blende; 
it  is  also  prepared  by  dissolving  zinc  in  dilute  sulphuric  acid,  and  by  roasting  native 
zinc  sulphide.  This  vitriol  occurs  in  white  agglomerated  crystals  and  in  small  acicular- 
shaped  crystals,  as  purified  zinc  sulphate ;  it  is  used  as  a  "  dryer "  in  oil  paints  and 
varnishes  ;  as  a  mordant  in  dyeing ;  for  disinfecting  purposes,  and  sometimes  as  a  source 
of  oxygen,  since,  on  being  submitted  to  a  red  heat,  it  gives  off  sulphurous  acid  and 
oxygen,  zinc  oxide  remaining. 

Zinc  Cnromate. — This  preparation,  obtained  by  precipitating  a  solution  of  zinc  sul- 
phate with  potassium  bichromate,  is  a  very  fine  yellow-coloured  powder,  used  now  and 
then  in  pigment  printing,  because  it  is  soluble  in  ammonia,  and  thrown  down  again  as 
a  powder  insoluble  in  water  when  that  menstruum  is  volatilised.  A  basic  zinc 
chromate  is  used  as  a  pigment  in  the  paint  trade. 

Zinc  Chloride. — This  compound  of  zinc,  ZnCl,,  is  obtained  either  by  dissolving 
zinc  in  hydrochloric  acid,  or  more  cheaply  by  causing  the  hydrochloric  acid  gas  given 
off  in  manufacturing  soda  to  act  upon  native  zinc  sulphide.  By  this  action  sul- 
phuretted hydrogen  is  formed,  which  can  be  burned  to  produce  sulphurous  acid  for  the 
sulphuric  acid  chambers.  The  solution  of  zinc  chloride  thus  obtained  is  evaporated  to 
the  consistency  of  a  syrup. 

Anhydrous  zinc  chloride  is  obtained  by  heating  an  intimate  mixture  of  dried 
zinc  sulphate  and  sodium  chloride;  zinc  chloride  is  formed  which  sublimes,  and 
sodium  sulphate  which  is  left  behind  (ZnSO4  +  2NaCl  =  Na2S04  +  ZnCl,).  This  anhy- 
drous chloride  may  be  sometimes  advantageously  used  instead  of  strong  sulphuric  acid, 
for  instance,  in  rape  and  colza  oil  refining,  and  perhaps,  although  it  would  be  more 
expensive  and  less  manageable,  in  the  manufacture  of  garancine  from  madder.  This 
chloride  has  of  late  been  employed  instead  of  sulphuric  acid  in  the  manufacture  of  stearic 
acid,  and  in  the  preparations  of  ether  and  parchment  paper.  Zinc  chloride  in  a 
strong  and  crude  solution  is  largely  and  very  successfully  used  for  preserving  timber ; 
in  paper-making  for  the  decomposition  of  bleaching  powder,  for  bleaching  the  half -stuff 
and  rags,  and  also  in  sizing  paper.  The  disinfectants  sold  as  Sir  William  Burnett's 


SECT,  in.]  COMPOUNDS   OF   LEAD.  461 

Fluid  and  Drew's  Disinfectant  are  solutions  of  zinc  chloride.  The  salt  used  in 
soldering  iron,  zinc,  pewter,  &c.,  is  a  compound  of  zinc  and  ammonium  chlorides 
(2NH4C1  +  ZnCl2) ;  its  solution  is  obtained  by  dissolving  3  parts  by  weight  of  zinc  in 
strong  hydrochloric  acid,  and  adding  after  the  solution  is  complete  an  equal  weight 
of  sal-ammoniac.  Zinc  oxy chloride,  obtained  by  mixing  zinc  oxide  with  a  concen- 
trated solution  of  zinc  chloride,  or  with  solutions  of  iron  or  manganese  chlorides, 
has  been  recently  proposed  by  M.  Sorel  as  a  plastic  mass  suited  for  stopping  hollow 
teeth. 

Cadmium  Yellow  (Jaune  brilliant ;  CdS). — This  pigment  is  prepared  by  the  action  of 
sulphuretted  hydrogen  upon  soluble  cadmium  salts ;  a  little  free  acid  should  be  present. 
The  hotter  and  more  concentrated  the  solution,  the  more  the  product  inclines  to  a  red. 

COMPOUNDS   OF   LEAD. 

Lead  Oxide,  PbO,  is  used  in  used  in  the  arts  as  massicot  or  as  litharge. 

Massicot. — Massicot,  or  yellow  lead  oxide,  occurs  as  a  yellow  or  ruddy-coloured 
powder,  obtained  either  by  heating  lead  carbonate  or  nitrate,  or  by  calcining  metallic 
lead  on  the  hearth  of  a  reverberatory  furnace.  Before  lead  chromate  was  known, 
massicot  was  used  as  a  yellow  pigment.  At  a  red  heat  this  substance  fuses  and  becomes 
glassy.  In  most  instances  it  is  not  a  pure  lead  oxide,  but  is  mixed  with  lead  silicate, 
the  fact  being  that  lead  oxide  at  a  red  heat  strongly  attacks  any  material  containing 
silica,  dissolving  the  silica  and  combining  with  it. 

Litharge. — Litharge  is  a  fused  crystalline  lead  oxide,  and  is  obtained  as  a  bye- 
product  of  the  separation  of  silver  from  lead  in  the  process  described  under  Silver. 
Litharge  always  contains  a  larger  or  smaller  quantity  of  copper  oxide,  antimony  oxide, 
traces  of  silver  oxide,  and,  according  to  Dr.  Wittstein,  metallic  lead,  varying  in 
quantity  from  1*25  to  3*10  per  cent.  The  copper  oxide  can  be  removed  by  digesting 
the  litharge  with  a  cold  solution  of  ammonium  carbonate.  Litharge  absorbs 
carbonic  acid  from  the  atmosphere,  combines  at  a  higher  temperature  with  silica, 
forming  with  it  a  readily  fusible  glass,  is  soluble  in  acetic  and  nitric,  and  also 
in  very  dilute  hydrochloric  acids,  and  is  equally  soluble  in  boiling  solutions  of  caustic 
potassa  and  soda.  It  is  insoluble  in  ammonium  carbonate  and  in  the  potassium  and 
sodium  carbonates.  Litharge  is  largely  used,  entering  into  various  compounds  for 
glass,  so-called  crystal-glass,  flint-glass,  strass  for  imitating  jewels,  for  glazing  pottery 
and  earthenware,  as  a  flux  in  glass  and  porcelain  staining,  for  the  preparation  of 
boiled  linseed  and  poppy-seed  oil,  for  the  preparations  of  lead  plaster,  putty,  minium, 
red-lead,  and  lead  acetate.  A  solution  of  lead  oxide  in  caustic  soda  lye  is  employed  in 
the  preparation  of  sodium  stannate  ;  this  solution  is  also  used  for  imparting  to  combs 
and  other  toilet  articles  made  of  horn  the  appearance  of  tortoiseshell  or  of  buffalo-horn. 
A  very  dilute  solution  is  used  as  a  hair-dye,  and  in  metallochromy  to  produce  iridescent 
colours  on  brass  and  bronze. 

Minium.  Red  Lead. — Red  lead  is  a  combination  of  lead  oxide  with  peroxide, 
the  formula  being  Pb204.  Red  lead  of  excellent  quality  is  largely  manufactured  near 
Newcastle-on-Tyne,  by  carefully  heating  lead  oxide  in  a  reverberatory  furnace  expressly 
built  for  that  purpose,  the  access  of  air  being  limited  so  as  to  prevent  the  fusion  of  a  por- 
tion of  the  oxide  to  litharge  which  cannot  then  be  converted  into  minium.  Sometimes 
metallic  lead  is  oxidised  in  a  reverberatory  furnace,  the  process,  as,  for  instance,  at 
Shrewsbury,  being  so  arranged  that  at  the  hotter  places  of  the  furnace  massicot,  and  at 
the  cooler  red  lead,  is  produced.  The  finest  coloured  minium,  or  Paris-red,  is  obtained 
from  lead  carbonate  by  the  same  method.  According  to  Burton's  plan,  lead  sulphate 
is  heated  with  Chili  saltpetre,  and  after  the  mass  has  been  exhausted  with  water  the 
red-lead  is  left,  while  sodium  sulphate  and  nitrite  are  dissolved.  Red  lead  is  used 


462  CHEMICAL  TECHNOLOGY.  [SECT.  m. 

for  a  variety  of  purposes,  many  similar  to  the  applications  of  lead  oxide.  Besides 
being  applied  as  a  cement,  when  mixed  with  linseed-oil  and  mastic,  for  the  flanges 
of  steam-pipes,  it  chiefly  enters  the  market  as  a  pigment,  being  for  that  purpose 
either  mixed  with  water  or  with  linseed-oil,  in  both  instances  covering  extremely 
well. 

Lead  Peroxide. — When  red-lead  is  treated  with  moderately  strong  nitric  acid, 
there  are  formed  lead  nitrate  and  peroxide  of  that  metal,  Pb02,  a  brown-coloured 
powder  largely  used  in  the  composition  of  the  phosphorus  mixtm^e  for  lucifer  matches. 
The  mixture  known  in  lucifer  match  works  as  oxidised  minium,  is  a  dried  composition, 
consisting  of  lead  nitrate,  lead  peroxide,  and  undecomposed  red-lead,  and  obtained 
by  drying  a  magma  of  minium  and  nitric  acid. 

White-lead,  basic  lead  carbonate,  2PbCO3.Pb(OH)2,  or  rather  hydrate  carbonate,  is 
commercially  known  as  of  the  Dutch,  French,  or  English  manufacture,  according  to 
the  method  employed.  The  Dutch  process  for  making  white- lead  is  founded  on  the 
fact  that  when  metallic  lead  comes  in  contact  with  the  vapours  of  acetic  acid,  car- 
bonic acid,  and  oxygen,  at  a  sufficiently  high  temperature,  the  metal  is  converted 
into  basic  lead  carbonate.  It  is  quite  evident  from  this  brief  statement  that  the  chief 
conditions  being  fulfilled,  the  methods  of  operation  may  be  more  or  less  varied.  In 
Holland,  Belgium,  and  some  parts  of  Germany,  the  lead — as  pure  as  possible  and 
free  from  silver,  which,  even  in  small  quantities  greatly  impairs  the  good  colour  of  the 
white-lead — is  cast  into  thin  strips,  which  are  wound  in  a  spiral  P,  Fig.  371,  in  coarse 
earthenware  pots,  A  (Fig.  371).  Common  vinegar,  C,  is  poured  into  the  lower  part  of 


these  pots,  some  beer-yeast  being  added.  The  lead  is  supported  and  placed  on  a  perforated 
piece  of  wood,  B,  so  as  to  prevent  direct  contact  with  the  vinegar.  After  this  the  pots  are 
covered  with  leaden  plates  and  buried  (see  Fig.  372)  in  amass  of  horse-dung  or  spent-tan 
and  dung.  The  fermentation  of  the  dung  causes  the  requisite  increase  of  temperature, 
and  the  vinegar  evaporating,  aided  by  the  oxygen  of  the  air,  converts  the  lead  into  basic 
acetate,  which,  in  its  turn,  is  converted  into  basic  lead  carbonate  by  the  carbonic  acid 
resulting  from  the  fermenting  manure.  This  rather  clumsy  process  has  given  place 
in  Germany  to  the  chamber  method,  consisting  essentially  in  the  following  arrange- 
ment. Instead  of  the  pots  being  made  the  receptacles  for  the  lead,  the  strips  of  that 
metal  are  bent  and  suspended  on  a  series  of  laths  run  lengthwise  through  the  chamber, 
on  the  floor  of  which  is  placed  a  layer  of  spent  tan,  marc  of  grapes,  or  other  ferment- 
able material,  saturated  with  vinegar.  An  improvement  upon  this  arrangement  is  to 
have  the  chamber  constructed  with  a  double  flooring,  one  water-tight,  the  other  a 
light  planking  perforated  so  as  to  admit  of  the  vapours  of  vinegar  being  carried  into 
the  compartment.  The  action  upon  the  lead  is  in  each  case  the  same  ;  it  is  converted 
chiefly  into  white-lead,  and  this  crude  product  is  purified  from  any  adhering  lead 
acetate  by  washing  with  water  before  being  brought  into  the  market.  There  is  still  in 
use  in  this  country  a  modification  of  the  method  practised  by  the  Dutch,  who,  by-the- 
byv  are  not  the  inventors  of  white  lead  manufacture,  the  true  origin  being  Moorish, 


SECT,  in.]  COMPOUNDS   OF   LEAD.  463 

the  trade  being  successfully  carried  on  by  these  semi-savages*  in  Southern  Spain,  whence 
the  Dutch  brought  over  the  art  in  the  sixteenth  century  to  Holland.  The  modification 
consists  in  the  following  arrangement : — Granulated  lead  is  first  moistened  with  about 
I '5  per  cent,  of  vinegar,  the  metal  being  previously  placed  on  hurdles  in  a  wooden  box, 
the  interior  of  which  is  heated  by  means  of  steam  to  35°,  some  steam  being  introduced 
to  keep  the  lead  moist.  If  care  is  taken  to  supply  carbonic  acid,  after  from  ten  to 
fourteen  days  the  operation  is  finished,  and  the  product  having  been  lixiviated  with 
water  and  dried,  is  ready  for  use. 

English  Method  of  Manufacturing  White  Lead. — According  to  this  plan  the  metal  is 
melted  in  a  large  iron  cauldron,  and  then  made  to  flow  on  the  hearth  of  a  reverberatory 
furnace,  so  as  to  convert  the  lead,  by  proper  access  of  air,  into  litharge,  which  is 
obtained  in  a  very  finely  divided  state  by  a  peculiar  arrangement  of  the  furnace.  The 
hearth  is  constructed  with  a  gutter,  into  which  the  fusing  mass  flows,  and  the  sides 
or  walls  of  the  gutter  are  perforated  to  admit  of  the  passage  of  the  molten  litharge, 
while  the  heavier  metal  sinks  to  the  bottom.  The  litharge  is  next  mixed  with  -^^ 
of  its  weight  of  a  solution  of  lead  acetate,  and  then  placed  in  a  series  of  closed 
troughs  communicating  with  each  other  and  admitting  of  the  passage  of  a  current  of 
impure  carbonic  acid,  obtained  by  the  combustion  of  coke  in  a  furnace  provided  with  a 
blast  to  give  an  impulse  to  the  gas.  The  litharge  is  continually  stirred  by  machinery 
to  accelerate  the  absorption  of  the  carbonic  acid  gas.  White  lead  made  by  this  process 
covers  very  well,  and  is  preferred  to  that  prepared  by  the  wet  method.  We  may 
mention  in  passing  that  it  is  the  custom  in  this  country  to  bring  white  lead  into  the 
market  ground  with  linseed  oil  to  a  thick  paste,  packed  in  strong  oaken  kegs  or  in  iron 
canisters. 

French  Method  of  Preparing  White  Lead. — This  method,  invented  by  MM.  Thenard 
the  elder,  and  Hoard,  is  not  only  generally  adopted  in  France  but  in  all  countries  where 
it  is  desired  to  carry  out  a  really  sound  and  rational  plan  of  white  lead  manufacture. 
The  method  is  as  follows  : — Litharge  is  dissolved  in  acetic  acid  to  obtain  a  solution  of 
basic  lead  acetate  — Pb(C2H30)202  +  Pb(OH2),  and  through  the  solution  a  current 
of  carbonic  acid  gas  is  passed.  Two  molecules  of  oxide  of  lead  are  converted  into 
white  lead,  while  neutral  lead  acetate  remains.  Litharge  is  again  added  to  the  solu- 
tion of  this  salt,  and,  by  digestion,  more  lead  subacetate  is  obtained,  which  is  applied 
as  just  described. 

Apparatus  used  in  White  Lead  Manufacture  at  Clichy. — The  machinery  and  contri- 
vances at  Clichy,  near  Paris,  for  effecting  the  method  just  explained,  are  exhibited  in 
Fig-  373-  In  the  tub,  A,  the  litharge  is  dissolved  in  acetic  acid.  B  C  is  a  stirrer,  moved 
by  means  of  the  shaft  shown  in  the  engraving,  bearing  at  the  top  a  pulley  for  the 
strap.  The  solution  of  basic  lead  acetate  can  be  run  off  through  the  tap  into  the 
vessel,  E,  made  of  copper  and  tinned  inside,  the  object  being  to  let  the  impurities  the 
solution  might  contain  subside.  From  E  the  fluid  is  led  into  the  decomposition  vessel 
constructed  with  800  tubes,  which  pass  from  the  top  to  a  depth  of  32  centimetres  beneath 
the  level  of  the  fluid.  These  tubes  are  in  communication  with  the  main  pipe,  gg,  which 
also  communicates  with  the  washing  apparatus,  P,  answering  the  purpose  of  purifier  for 
the  carbonic  acid  gas  generated  in  the  small  lime-kiln,  GT,  by  the  ignition  of  a  mixture  of 
parts  by  bulk  of  chalk  and  i  part  by  bulk  of  coke  with  sufficient  access  of  air.  The 
decomposition  of  the  basic  lead  acetate  being  finished  in  from  twelve  to  fourteen 
hours,  the  supernatant  liquor,  neutral  lead  acetate,  is  run  off  into  the  vessel,  i,  and 
the  semi-fluid  magma  of  white-lead  passes  into  0.  The  pump,  R,  serves  to  again  convey 
the  neutral  acetate  to  the  tank,  A,  and  the  operation  is  re-commenced.  The  white  lead 
in  O  is  well  washed — the  first  wash-water  being  conveyed  back  to  the  tank,  A,  and 

*  How  the  builders  of  the  Alhambra  and  the  inventors  of  the  rotation  of  crops  can  be  called 
-"  semi-savages,"  is  an  unsolved  problem. — EDITOR. 


464 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


after  drying  is  ready  for  use.  In  order  to  obtain  the  carbonic  acid  cheaply,  it  has  been 
proposed  to  ignite  a  mixture  of  chalk  or  limestone,  charcoal,  and  peroxide  of  manga- 
nese (CaC03  +  C  +  3MnO2  =  Mn3O4  +  CaO  +  2CO2.)  Where  admissible,  the  carbonic 
acid  resulting  from  the  fermentation  of  beer-wort,  or  of  distillery- wash,  may  be  applied. 

Fig-  373- 


Natural  sources  of  carbonic  acid  sometimes  occur  in  the  neighbourhood  of  active  or 
extinct  volcanoes  ;  and  near  Brohl,  close  to  the  Laacher  Sea  in  Rhenish  Prussia,  a 
locality  well-known  to  tourists,  a  very  plentiful  and  continuous  supply  of  carbonic 
acid  is  naturally  obtained  and  actually  applied  for  the  purpose  under  consideration. 

Among  the  very  various  suggestions  for  improved  methods  of  making  white  lead, 
and  for  which  an  enormous  number  of  patents  have  been  taken  out,  especially  in  this 
country  and  in  the  United  States,  we  briefly  mention  the  following  : — Button  and 
Dyer  first  slightly  moisten  litharge  with  water,  next  mix  it  with  a  small  quantity  of  a 
solution  of  lead  acetate,  place  the  mixture  in  a  stone  trough,  agitating  and  passing 
hot  carbonic  acid  over  it.  Pallu  (1859)  causes  finely-divided  lead  to  be  thrown  with 
great  force,  by  means  of  a  centrifugal  machine,  on  an  inclined  plane,  care  being  taken 
to  moisten  th#  lead  with  acetic  acid.  After  the  lapse  of  an  hour,  the  finely  divided 
lead  is  converted  into  acetate  and  carbonate.  A  solution  of  lead  acetate  is  then 
poured  over  the  mass,  and  the  lead  acetate  it  contains  is  dissolved,  while  the  white 
lead  is  carried  into  a  tank,  and  there  forms  a  deposit.  Griineberg  (1860)  prepares 
white  lead  by  submitting  granulated  lead  to  the  simultaneous  action  of  air,  acetic  and 
carbonic  acid,  aided  by  the  rapid  motion  of  the  metal.  From  private  information 
obtained  from  the  largest  wholesale  house  in  London  dealing  in  white  lead,  whose  con- 
nections and  trade  relations  embrace  literally  the  whole  world,  we  have  learned  that 
not  loooth  part  of  the  lead,  as  it  is  technically  termed,  of  good  and  saleable  quality 
met  with  in  the  trade,  is  made  by  these  new  processes,  since  the  products  of  most  of 
them  are  deficient  in  some  respect  or  other. 

Theory  of  Preparing  White  Lead. — Leaving  out  of  the  question  the  prepai'ation  of 
white  lead  from  lead  sulphate,  the  preparation  of  the  pigment  as  regards  all  the  other 
methods  is  dependent  upon  : — 

1 .  The  formation  of  basic  lead  acetate ; 

2.  The  decomposition  of  that  compound  into  neutral  lead  acetate  and  white  lead. 
Viewing  white  lead  for  this  purpose  simply  as  a  lead  carbonate,  although  we  shall 
presently  see  that  the  white  lead  of  commerce  is  not  so  simply  constituted,  the  forma 
tion  may  be  illustrated  by  the  following  formulae  : — 


IECT.  in.]  COMPOUNDS  OF  LEAD. 


Acetic  acid.  Basic  lead  acetate. 

,  +  200,  +  2PbC03 


Basic  lead  acetate.  Lead  car-       Neutral  lead 

bonate.  acetate. 

It  is  therefore  evident  that  a  comparatively  very  small  quantity  of  lead  acetate  can 
produce  a  large  quantity  of  white  lead,  and  the  manufacture  of  that  material  would  be 
endless  but  for  the  fact  that  white  lead  retains  some  neutral  lead  acetate,  and  that 
the  loss  of  acetic  acid  cannot  be  practically  avoided. 

Properties  of  White  Lead.  —  When  unadulterated  and  well-made,  white  lead  is  an 
exquisitely  fine  white  coloured  powder,  devoid  of  taste  and  smell.  The  white  lead  of 
commerce  exhibits,  according  to  the  mode  of  preparation,  different  features  ;  one  pre- 
paration is  met  with  in  flakes,  having  been  obtained  by  the  corrosion  of  thin  strips  of 
lead  placed  in  pots.  The  lead  known  as  Krems  lead  is  pure  white  lead  made  up  into 
cakes  by  means  of  gum-water. 

The  variety  of  white  lead  known  as  pearl  white  is  blued  with  either  a  small  quantity 
of  indigo  or  Berlin  blue.  The  white  lead  of  commerce  has  frequently  been  made  the 
object  of  chemical  analysis,  especially  by  Dr.  G.  J.  Mulder  and  M.  Griineberg.  The 
results  of  the  analyses  of  the  undermentioned  samples  prove  the  correctness  of  the 
formula  given  above.  The  numbers  refer  to  :  —  i.  Krems  white  lead.  2.  Precipitated 
by  the  Clichy  method  and  manufactured  at  Magdeburg.  3.  From  the  Harz.  4.  An- 
other sample  from  Krems.  5.  A  sample  from  a  chemical  laboratory  by  imitating 
the  Dutch  method  on  a  limited  scale.  6,  7.  Samples  from  Klagenfurt,  Carynthia. 
.  English  lead  manufactured  according  to  the  Dutch  method. 

i.                 2.  3.                4.                 5.  6.  7.               8. 

Oxide  of  lead      .     8377  ...  85-93  ...  86-40  ...  86-25  •••  84'42  •••  8672  ...  86-5  ...  86-51 

Carbonic  acid     .     15-06  ...  11-89  •••  H'53  •••  "'37  •••  I4'45  •••  H'28  ...  11-3  ...  11-26 

Water         .        .       1*01  ...     2*01  ...  2*13  ...     2-21  ...     1-36  ...  2-00  ...  2*2  ...  2-23 

It  is  certain  that  the  covering  properties  of  white  lead  are  dependent  upon  its  state 
of  aggregation,  because  a  loose  crystalline  white  lead  does  not  cover  nearly  as  well  as 
the  perfectly  amorphous  lead  prepared  by  the  old  Dutch  method.  It  appears  that  the 
covering  power  increases  with  the  amount  of  hydrated  lead  oxide.  This  is  proved 
by  the  fact  that  those  who  merely  choose  white  lead  by  its  covering  power  are  often 
misled,  a  fact  lately  tested  by  the  editor  of  this  work,  by  giving  to  a  workman, 
thoroughly  acquainted  with  white  lead  as  commercially  met  with,  a  mixture  of 
carefully  prepared  and  dried  hydrated  lead  oxide,  to  which  white  precipitate, 
bismuth  subnitrate,  and  bismuth  carbonate  had  been  added.  The  man,  after  testing 
a  series  of  samples  of  purposely  adulterated  white  lead,  all  of  which  he  detected 
as  adulterated,  was  unable  to  speak  with  certainty  of  the  above  mixture,  which 
he  took  for  pure  lead. 

Adulteration  of  White  Lead.  —  It  has  been,  and  is  still,  to  some  extent,  the  cus- 
tom in  manufactories  to  add  to  white  lead  a  certain  quantity  of  barium  sulphate 
either  native  or  artificially  prepared.  Lead  is  often  mixed  with  lead  sulphate, 
chalk,  barium  carbonate,  barium  sulphate,  and  pipe-clay;  but  these  adulterations 
are  most  common  in  the  retail  trade.  None  of  these  substances  ought  to  be 
present  ;  they  possess  no  covering  power  and  needlessly  absorb  oil.  Pure  white  lead 
ought  to  be  perfectly  soluble  in  very  dilute  nitric  acid,  and  in  the  resulting  clear 
solution  caustic  potassa  should  not  produce  a  precipitate.  A  residue  insoluble 
in  the  dilute  nitric  acid  indicates  the  presence  of  gypsum,  heavy-spar,  or  lead 

2  G 


466  CHEMICAL  TECHNOLOGY.  [SECT.  HI. 

sulphate.  The  lead  sulphate  may  be  recognised  by  reducing  the  lead  with  the 
blowpipe.  Barium  sulphate  can  be  made  evident  by  ignition  with  charcoal  in 
the  blowpipe  flame,  treating  the  residue  with  dilute  hydrochloric  acid,  and  adding 
a  solution  of  gypsum,  which  again  yields  a  precipitate  of  barium  sulphate.  Gypsum 
does  not  yield  an  insoluble  precipitate  with  dilute  nitric  acid,  but  does  so  with  a 
solution  of  ammonium  oxalate.  According  to  Dr.  Stein,  the  most  simple  method 
of  estimating  quantitatively  a  mixture  of  white  lead  and  barium  sulphate,  is  to 
heat  the  weighed  sample  in  a  piece  of  combustion-tube,  and  to  collect  the  carbonic 
acid  in  a  Liebig's  potassa-bulb,  a  chloride  of  calcium-tube  being  fastened  by  a  per- 
forated cork  to  the  combustion-tube  to  absorb  the  moisture.  The  quantity  of 
carbonic  acid  given  off  stands  in  direct  proportion  to  the  quantity  of  lead  carbonate 
present.  Pure  white  lead  of  good  quality  gives  off  about  14-5  per  cent,  of  the 
gas,  and,  according  to  Dr.  Stein's  researches,  the  undermentioned  series  of  mix- 
tures gave  off  the  quantities  of  carbonic  acid  indicated  : — 

33*3  parts  of  white  lead  and  66 '6  parts  of  heavy-spar  lost  by  ignition  4*5-5  per  cent. 
66-6  „  „  33-3  „  „  „  6-5-7        „ 

80-0  „  „  20-0  „  „  „  13-0          „ 

50-0  „  „  50-0  „  „  „  10-10-4    „ 

Applications  of  White  Lead. — The  extensive  applications  of  this  material  as  a  con- 
stituent of  paints,  "  to  give  body,"  as  the  term  runs,  and  as  putty,  and  for  various 
chemical  operations  are  well  known.  It  has  been  experimentally  proved  by  Dr.  G.  J. 
Mulder  in  his  treatise  On  the  Chemistry  of  Drying  Oils  and  the  Practical  Applica- 
tions to  be  drawn  therefrom,  that  the  quantity  of  white  lead  used  in  proportion  to 
linseed  oil  for  painting  purposes  is  far  too  great,  being  on  an  average  from  2 50  to  280 
parts  of  white  lead  to  100  parts  of  oil,  while  the  author  found  that  52  parts  of  un- 
adulterated white  lead,  or  44  parts  of  oxide  of  lead  (PbO)  to  100  parts  of  raw  or 
boiled  linseed  oil  are  amply  sufficient  quantities.  White  lead,  however  useful,  is  very 
sensitive  to  the  action  of  sulphuretted  hydrogen,  by  which  it  is  blackened  and  dis- 
coloured, causing  not  only  all  the  white  paint  to  be  spoiled,  but  also  all  pigments  and 
paints  of  which  white  lead  is  a  constituent,  as  may  be  seen  to  a  very  large  extent  every 
summer  at  Amsterdam,  where  sulphuretted  hydrogen  is  abundantly  given  off  from 
the  stagnant  canals.  The  action,  however,  of  the  sea  air  in  autumn  has  the  effect  of 
somewhat  restoring  the  blackened  and  discoloured  painted  surfaces  to  their  primitive 
hue.  Thenard  suggested  that  pictures  which  had  become  blackened  should  be 
cleaned  by  means  of  hydrogen  peroxide,  the  oxygen  of  which  present  as  ozone  converts 
the  blackened  lead  colours  into  white  lead  sulphate. 

In  this  country  it  has  become  an  almost  universal  custom  to  sell  white  lead  ready 
ground  with  linseed  oil  into  a  thick  paste.  This  practice  certainly  saves  painters  a 
great  deal  of  trouble,  but  is  also  pregnant  with  the  difficulty  of  detecting  adulteration, 
while  there  is  a  chance  of  an  inferior  oil,  rosin  oil,  being  added.  The  oil  almost 
entirely  prevents  the  action  of  any  acid  upon  the  paste ;  even  if  very  strong  nitric 
acid  be  taken,  and  heat  applied,  the  decomposition  and  disintegration  are  very  slow 
and  incomplete,  and,  besides,  owing  to  the  insolubility  of  lead  nitrate  in  nitric  acid, 
the  action  of  strong  nitric  acid  upon  oil  thus  mixed  gives  rise  to  a  variety  of  com- 
pounds, which  interfere  with  the  usual  modes  of  testing  the  white  lead.  To  remove 
the  oil  in  order  to  test  white  lead,  the  best  plan  is  to  thoroughly  incorporate  some 
of  the  sample  with  a  mixture  of  chloroform  and  strong  alcohol  in  equal  parts, 
and  to  wash  the  mass  by  decantation  or  on  a  filter  with  a  fluid  composed  of  2  parts 
of  chloroform  and  i  of  strong  alcohol.  The  quantity  of  the  oil  may  then  be  ascer- 
tained by  the  evaporation  of  this  solvent.  After  washing  once  or  twice  with  boiling 


SECT.  ni.]       COMPOUNDS  OF  MANGANESE  AND  CHEOMIUM.  467 

alcohol  and  then  drying,  the  white  lead  can  be  readily  tested  by  any  of  the  known 
methods. 

The  proposed  electrolytic  method  of  producing  white  lead  seems  not  to  promise 
good  results. 

White  Lead  from  Chloride  of  Lead. — M.  Tourmentin  prepares  white  lead  from  basic 
lead  chloride,  obtained  by  the  action  of  common  salt  upon  litharge,  by  mixing  that 
compound  with  water,  passing  through  it  a  current  of  carbonic  acid,  and  next  boiling 
the  fluid  in  a  leaden-pan  with  powdered  chalk  until  a  test  sample,  when  filtered,  does 
not  become  blackened  by  the  addition  of  ammonium  sulphide.  The  white  lead  thus 
formed  is  freed  from  salt  by  washing  with  water. 

Basic  Lead  Chloride  as  a  /Substitute  for  White  Lead. — Mr.  Pattinson,  of  the 
Felling  Chemical  Works,  near  Newcastle-on-Tyne,  has  proposed  that,  instead  of  white 
lead,  a  basic  lead  chloride  (oxychloride)  should  be  used,  and  he  prepares  that  sub- 
stance by  adding  to  a  hot  solution  of  lead  chloride  (PbCl2),  containing  from  400 
to  500  grammes  of  the  salt  to  the  cubic  foot,  an  equal  bulk  of  saturated  lime-water. 
This  addition  causes  the  throwing  down  of  the  compound  (PbCl2  +  PbH202),  which, 
after  having  been  collected  on  a  filter  and  washed,  is  dried  and  used  as  a  pigment. 
The  lead  chloride  is  obtained  directly  from  galena,  which  is  decomposed  in  leaden 
vessels  with  strong  hydrochloric  acid.  The  sulphuretted  hydrogen  thus  formed  is 
carried  by  suitable  tubing  to  a  burner  in  the  sulphuric  acid  chamber,  the  resulting 
sulphurous  acid  from  the  combustion  being  used  for  the  production  of  sulphuric 
acid.  Pattinson's  white  lead  is  not  so  white  as  ordinary  white  lead,  its  colour 
verging  to  yellow,  but  this  is  110  objection  where  white  lead  is  to  be  used  with  other 
paints,  and  the  less  so  as  Pattinson's  oxychloride  of  lead  covers  well. 

Lead  Sulphate  (PbS04),  obtained  as  a  bye-product  in  the  preparation  of  aluminium 
acetate  from  alum  and  sugar  of  lead,  or  in  obtaining  acetic  acid  by  the  action  of 
sulphuric  acid  upon  lead  acetate,  or  in  a  very  impure  state  as  a  deposit  in  the  lead 
chambers  of  sulphuric  acid  works,  is  a  difficult  bye-product  to  utilise.  It  cannot  be 
easily  reduced  to  metallic  lead,  and  its  low  covering  power  prevents  its  use  as  a 
pigment.  It  may  be  used  in  the  manufacture  of  lead  chromate  (which  see). 

Cassel  Yellow  and  Turner's  Yellow. — If  i  part  of  ammonium  chloride  is  melted  with 
10  parts  lead  oxide  there  is  produced  a  yellow  foliaceous  crystalline  mass,  which,  when 
finely  ground  and  elutriated,  is  sold  as  Cassel  yellow.  Its  composition  is  said  to  be 
PbCl2,7PbO.  If  lead  oxide  is  treated  with  solution  of  sodium  chloride,  a  white  lead 
oxychloride  is  produced,  which,  after  melting,  is  known  as  Turner's  yellow.  Its 
formula  is  PbCl2,5PbO.  Both  these  preparations  have  been  superseded  by  chrome 
yellow. 

COMPOUNDS   OF   MANGANESE   AND   CHROMIUM. 

Manganese. — Of  all  the  ores  of  manganese  met  with  in  various  degrees  of  oxidation, 
only  the  peroxide,  mineralogically  known  as  pyrolusite,  polianite,  and  technically  as 
glass-makers'  soap,  is  industrially  of  much  importance.  When  perfectly  pure  this 
mineral  consists  of  63-64  per  cent,  of  manganese,  and  36-36  per  cent,  of  oxygen, 
its  formula  being  Mn08 ;  but  the  ore,  as  met  with  in  commerce,  frequently  contains 
baryta,  silica,  and  water,  and  sometimes  oxides  of  iron,  nickel,  cobalt,  and  lower  oxides 
of  manganese — viz.,  Braunite,  Mn203;  Manganite,  Mn,Os,H2O;  Hausmannite,  Mn304; 
and  various  other  minerals,  as  potassa  compounds,  lime,  &c.  In  Germany  the  ore  is 
purified  by  most  ingeniously  contrived  machinery,  which  might  be  very  advanta- 
geously applied  to  a  great  many  other  metallic  ores  and  phosphatic  minerals.  Manganese 
is  industrially  employed  in  making  oxygen,  the  preparation  of  bromine  and  iodine, 
glass-making,  colouring  enamels,  for  producing  mottled  soaps,  in  puddling  iron,  and 
in  dyeing  and  calico-printing,  for  preparing  potassium  permanganate ;  but  the  largest 


468  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

consumers  are  the  manufacturers  of  chlorine.  The  bulk  of  the  manganese  of  commerce 
is  derived  from  Germany,  which  supplies  about  700,000  cwts.  to  Europe  annually.  It 
is  found  also  very  largely  and  of  excellent  quality  in  Spain,  as  well  as  in  Italy,  Greece, 
Turkey,  Sweden,  and  British  India. 

Testing  the  Quality  of  Manganese. — The  value  of  manganese  for  technical  purposes 
depends — i.  On  the  quantity  of  oxygen  it  is  capable  of  yielding,  or  the  quantity  of 
chlorine  it  will  evolve,  not  taking  into  account  the  0  of  the  MnO.  2.  On  the  nature 
and  quantity  of  the  substances  soluble  in  acids,  such  as  the  calcium  and  barium  car- 
bonates and  ferrous  oxide,  which,  not  yielding  chlorine,  saturate  a  certain  quantity  of 
hydrochloric  acid.  But  even  if  these  impurities  are  absent,  it  may  happen  that,  of  two 
samples  of  manganese,  one  requires  more  acid  than  the  other  to  evolve  the  same  bulk 
of  chlorine  gas,  as,  for  instance,  when  one  of  the  samples  contains  in  addition  to 
manganese  peroxide  (MnO.,)  also  the  sesquioxide  (Mn203),  especially  if  the  latter  is 
present  as  hydrate.  3.  On  the  quantity  of  water,  which  may  amount  even  to 
15  per  cent. 

According  to  the  experiments  of  Fresenius,  the  most  suitable  temperature  for 
drying  a  weighed  sample  of  manganese,  in  order  to  estimate  the  water  it  contains,  is 
1 20°,  no  water  of  hydratation  being  expelled  at  that  heat ;  but  for  commercial  analysis 
the  drying  of  a  sample  at  100°  is  quite  sufficient,  provided  it  be  kept  at  that  heat  for 
some  hours  consecutively.  Among  the  many  methods  proposed  for  testing  manganese, 
that  originally  invented  by  Thompson  and  Berthier,  and  improved  upon  by  Will  and 
Fresenius,  is  based  on  the  fact  that  a  molecule  of  manganese  peroxide  treated  with  sul- 
phuric acid  is  capable  of  converting,  by  the  0  given  off,  i  moL  of  oxalic  acid  into 
2  mols.  of  COj. 

From  the  weight  of  C08  evolved  the  quantity  of  manganese  peroxide  actually 
present  in  the  sample  is  calculated.* 

Potassium  Permanganate. — This  salt  (KMnOJ,  used  for  disinfecting,  bleaching, 
and  other  oxidising  purposes,  and  constantly  employed  in  chemical  laboratories, 
owes  its  efficiency  to  the  fact  that,  in  contact  with  dilute  sulphuric  acid,  it  yields 
manganous  oxide  and  oxygen  (Mn2O7=  2MnO  +  50).  The  potassium  permanganate  is 
for  technical  purposes  prepared  in  the  following  manner : — 500  kilos,  of  caustic  potassa 
solution  at  84°  Tw.  (=  1-44  sp.  gr.)  are  added  to  105  kilos,  of  potassium  chlorate,  and 
the  mixture  evaporated  to  dryness,  there  being  gradually  added  180  kilos,  of  powdered 
manganese,  and  the  heating  continued  to  the  fusion  of  the  mass,  which  is  stirred  until 
cold.  The  powder  thus  obtained  is  heated  in  small  iron  crucibles  to  a  red  heat,  and 
when  semi-fluid  is  cooled ;  the  mass  is  next  broken  up  and  put  into  a  large  cauldron 
filled  with  hot  water,  and  left  standing  for  about  an  hour.  The  clear  liquid  having 
been  decanted  from  the  sediment,  hydrated  manganese  peroxide,  is  evaporated  to 
crystallisation ;  180  kilos,  of  manganese  yield  98  to  100  kilos,  of  crystallised  permanga- 
nate. Approximately  the  process  may  be  elucidated  as  follows : — 

(a)  By  the  fusion  of  the  potassium  manganate  and  potassium  chloride — 
6Mn03    +    2KC103    +    i2KOH    =    6K,MnO4    +    2KC1    +    6H,0. 

(6)  During  the  solution  of  the  fused  mass  in  water,  the  potassium  manganate  is 
converted  into  potassium  hydrate,  hydrated  manganese  peroxide,  and  potassium  per- 
manganate, 3K,MnO4  +  6H,O  =  4KOH  +  2KMn04  +  MnO,  +  4H2O.  Consequently 
one-third  of  the  manganic  acid  is  lost  by  the  formation  of  manganese  peroxide. 
This  also  occurs  when,  according  to  M.  Tessie  du  Motay's  plan,  the  conversion  of 
potassium  manganate  into  permanganic  acid  is  effected  by  magnesium  sulphate — 
3K,Mn04  +  2MgSO4  =  2KMnO4  +  Mn02  +  2K,SO4  +  2MgO.  Dr.  Staedeler  therefore 
suggests  that  the  potassium  manganate  should  be  converted  into  permanganate  by 
chlorine,  according  to  the  formula — 2K2Mn04  +  Cl  =  KC12  +  2KMn04.  For  disinfecting 
*  See  Select  Methods  in  Chemical  Analysis,  by  W.  Crookes,  F.R.S. 


SECT,  in.]  COMPOUNDS   OF   CHROMIUM.  469 

purposes  a  mixed  sodium  and  v  potassium  permanganate,  or  even  the  latter  alone,  is 
usual ;  the  well-known  Condy's  fluid  is  a  solution  of  this  salt  in  water.  Kuhne's  dis- 
infectant is  a  mixture  of  sodium  permanganate  and  ferric  sulphate.  Potassium  per- 
manganate is  used  to  some  extent  in  dyeing,  and  for  staining  wood.* 

The  Berlin  Joint-Stock  Chemical  Company  produces  permanganates  by  the  electro- 
lysis of  a  manganate. 

Ohromates. — The  yellow,  neutral  salt,  K,Cr04,  is  prepared  by  heating  chrome 
iron  ore,  previously  pulverised  and  elutriated,  with  potassium  carbonate  and  nitrate 
on  the  hearth  of  a  reverberatory  furnace.  The  oxygen  of  the  saltpetre  causes  the 
higher  oxidation  of  the  ferrous  oxide  and  chromium  sesquioxide,  the  latter  being 
converted  into  chromic  acid.  The  thoroughly  sintered,  not  molten,  mass  is,  after 
cooling,  again  ground  up  and  lixiviated  with  boiling  water,  and  also  boiled  for  a  time 
to  extract  the  neutral  potassium  chromate.  Wood  vinegar  is  added  to  the  solu- 
tion to  precipitate  the  alumina  and  silica,  after  which  the  clear  liquid  is  evaporated, 
until  a  film  of  saline  material  begins  to  form,  when  it  is  left  to  crystallise.  The 
crystals  take  a  column-like  form,  and  are  of  a  lemon-yellow  colour,  readily  soluble 
in  water,  but  insoluble  in  alcohol,  and  having  a  great  tendency  to  become  converted 
into  potassium  bichromate  or  red  chromate.  This  conversion  of  the  neutral  salt  into 
the  bi-  or  acid-  salt  is  at  once  effected  by  the  addition  to  its  solution  of  sulphuric  or 
nitric  acid — preferably  the  latter,  on  account  of  the  formation  of  potassium  nitrate, 
which  may  be  either  sold  or  used  in  the  manufacture  of  the  neutral  chromate. 

The  potassium  dichromate  or  acid  chromate,  K2Cr207,  crystallises  in  anhydrous, 
aurora-red  coloured  triclinohedric  prismatic  crystals,  soluble  in  10  parts  of  water. 
This  solution  is  highly  caustic  and  poisonous.  When  heated  to  redness  the  salt  gives 
off  oxygen,  leaving  chromium  oxide  and  neutral  potassium  chromate  in  the  retort. 

Jacquelain  proposes  that  the  chrome-iron  should  be  mixed  with  chalk  and  the 
mixture  heated  and  frequently  stirred,  then  cooled,  pulverised,  and  put  into  water, 
with  the  addition  of  enough  sulphuric  acid  to  produce  a  weak  reaction,  the  result 
being  the  formation,  first  of  calcium  chromate,  which,  by  the  addition  of  the  acid, 
becomes  the  bichromate  of  that  base.  The  ferrous  sulphate  present  in  this  solution 
is  precipitated  by  means  of  chalk.  In  order  to  convert  the  calcium  bichromate  into 
the  corresponding  potassium  salt,  it  is  only  necessary  to  add  a  solution  of  potassium 
carbonate,  the  result  being  of  course  the  precipitation  of  calcium  carbonate  and  the 
exchange  of  the  chromic  acid  from  the  lime  to  the  potassa.  According  to  Tilghman's 
process  chrome-iron  ore  is  mixed  with  2  parts  of  lime,  2  of  potassium  sulphate  and 
heated  for  eighteen  to  twenty  hours  in  a  reverberatory  furnace.  The  same  inventor 
suggests  the  heating  of  chrome-iron  ore  with  powdered  felspar  and  lime.  Mr. 
Swindells  ignites  chrome  ore  with  equal  parts  of  either  sodium  or  potassium  chloride 
to  the  highest  possible  white  heat,  at  the  same  time  exposing  the  mixture  to  a  con- 
stant current  of  superheated  steam,  the  formation  of  sodium  or  potassium  chromate 
resulting.  The  most  important  improvement  in  the  preparation  of  potassium  chro- 
mate is  the  substitution  of  potash  for  saltpetre  and  the  use  of  a  furnace  so  constructed 
\s  to  admit  of  the  proper  access  of  air  to  the  strongly  heated  mass,  the  oxygen  of  the 
air  being  made  to  oxidise  the  chromic  oxide  to  chromic  acid.  Another  improvement 
is,  that  in  using  lime  instead  of  alkali,  the  oxidation  of  the  chromic  oxide  is  greatly 
accelerated,  by  reason  that  when  lime  is  employed  instead  of  potassa  the  heated 
materials  do  not  become  semi-fused  or  pasty,  but,  remaining  pulverulent,  admit  of 
the  readier  access  of  air,  as  well  as  preventing  the  sinking,  on  account  of  higher 
specific  gravity,  of  a  portion  of  the  chrome  ore  to  the  bottom  of  the  hearth,  and  there 
becoming  withdrawn  from  the  action  of  the  heat. 

*  Latterly  sodium  permanganate  has  been  prepared  and  used  at  great  expense  for  deodorising 
the  Thames. 


470  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

Applications  of  the  Potassium  Chromates. — Before  the  year  1820  the  salts  spoken  of 
were  only  used  for  the  preparation  of  chrome-yellow  ;  their  preparation  was  then  very 
expensive,  viz.,  the  calcination  of  the  chrome-iron  ore  with  potassium  nitrate  only. 
At  this  date  M.  Koachlin  discovered  the  applicability  of  potassium  dichromate  to  the 
obtaining  of  what  is  technically  termed  "  discharge "  for  Turkey  red — a  madder 
colour — a  discovery  soon  followed  by  others  bearing  upon  the  useful  applications 
of  this  salt,  among  which  are  the  formation  of  chrome-yellow  and  chrome-orange  in 
calico-printing,  chrome-black  in  dyeing,  the  oxidation  of  catechu  and  Berlin  blue,  the 
discharge  of  indigo  blue,  the  bleaching  of  palm  oil  and  other  fatty  substances,  the  pre- 
paration of  mixtures  for  the  heads  of  lucifer  matches,  the  preparation  of  mercurous 
chromate  and  chromic  oxide  as  green-coloured  pigments  in  glass-  and  china-painting, 
and  for  the  preparation  of  Guignet's  Green,  a  peculiar  hydrated  chromium  oxide, 
CraO32H20,  obtained  by  heating  i  part  of  potassium  bichromate  and  3  parts  of  crys- 
tallised boric  acid,  and  used  as  a  pigment  in  calico-printing.  As  might  be  expected, 
all  these  discoveries  gave  a  strong  impulse  to  the  manufacture  of  the  potassium 
chromates,  which  have  recently  found  still  further  useful  applications  in  the  obtaining 
of  colours  from  coal-tar — i.e.,  aniline  violet,  aniline  green,  and  alizarine,  in  the  manu- 
facture of  chlorine  gas,  in  defuseling  brandy  and  other  spirits,  and  in  the  purification 
of  wood-vinegar  made  from  the  crude  pyroligneous  acid. 

According  to  M.  J.  Persoz,  there  exist,  America  excepted,  only  six  manufactories 
of  the  potassium  chromates — viz.,  two  in  Scotland,  one  in  France,  one  at  Trjbndhem, 
Norway,  and  one  at  Kazan,  near  the  Oural,  Russia ;  the  total  production  of  these  works 
amounted  in  1869  to  60,000  cwts.* 

Sodium  Chromate  (Na2Cr04). — Walberg  mixes  6  parts  finely-ground  chrome  ore 
(containing  44  per  cent.  Cr803),  3  parts  soda-ash  (containing  92  per  cent,  sodium 
carbonate),  and  3  parts  chalk  in  a  reverberatory  in  the  oxidising  flame ;  the  charge  of 
the  furnace  being  i  ton.  The  hot  mass  is  lixiviated  with  water,  forming  a  lye  of 
84°  Tw.  It  is  then  boiled  down  in  an  iron  pan  to  104°  Tw.,  and  poured  into  tanks 
lined  with  lead.  When  cold,  there  are  formed  acicular  yellow  crystals  of 

Na2Cr04.ioHsO. 

They  are  drained  in  a  centrifugal  machine,  placed  in  a  drying-chamber,  at  a  heat  not 
exceeding  30°,  and  well  ventilated.  Here  they  effloresce,  and  are  converted  into  a 
yellow  anhydrous  powder. 

Sodium  chromate  so  prepared  has  the  composition — 

Na.jCr04 96-60 

Sodium  sulphate  .         .        .         .  0^92 

Insoluble  residue  .        .        .        .  0^40 

Water 1-28 

99 '20. 

For  producing  sodium  dichromate,  Chrystal  ignites  chrome  ore  with  lime  and  soda, 
lixiviates,  decomposes  the  neutral  chromate  with  an  acid,  and  evaporates  to  crystallisa- 
tion. Ammonium  chromates  may  be  obtained  from  the  sodium  salts  by  double  decom- 
position. 

Chromic  Acid,  Cr08,  is  obtained  by  decomposing  potassium  dichromate  with  sulphuric 
acid.  It  is  used  in  galvanic  batteries  in  place  of  nitric  acid. 

Chrome-Yellow,  Lead  Chromate  (PbCrO4),  is  not  to  be  confounded  with  yellow 
chrome,  the  neutral  potassium  chromate.  There  are  in  technical  use  three  different 
compounds  of  lead  and  chromic  acid — viz.,  neutral  lead  chromate  or  chrome-yellow, 
basic  chromate  or  chrome-red,  and  a  mixture  of  these  two  salts  constituting  chrome- 
orange.  The  first  of  these  substances  is  obtained  by  two  methods: — (i)  By  the 

*  There  is  also  a  manufactory  of  the  chromates  at  Sowerby  Bridge,  near  Halifax. 


SECT.  HI.]  COMPOUNDS  OF  CHROMIUM.  471 

precipitation  of  a  solution  of  potassium  chromate  with  a  solution  of  lead  acetate  ;  or 
(2)  by  the  use  of  lead  sulphate  or  chloride.  According  to  the  first  plan,  the  operation 
begins  with  the  preparation  of  a  solution  of  lead,  for  which  purpose  granulated 
lead  is  put  into  wooden  tubs  placed  one  above  the  other,  and  the  taps  each  tub  is 
provided  with  being  turned  off,  vinegar  is  poured  into  the  upper  tub.  In  about  ten 
minutes  the  tap  at  the  bottom  of  the  tub  is  opened,  and  the  contents  let  into  the 
second  tub.  The  operation  is  repeated  with  all  the  tubs,  four  to  eight  in  number,  the 
object  simply  being  to  moisten  the  lead  thoroughly  with  the  vinegar,  so  as  to  cause 
rapid  oxidation  on  its  subsequent  exposure  to  air.  The  metal  soon  becomes  coated 
with  a  bluish-white  coloured  film,  and  when  this  is  apparent,  vinegar  is  again  poured 
into  the  topmost  tub  and  left  for  about  an  hour,  after  which  it  is  run  off  into  the 
second  tub,  and  the  operation  continued  until  there  is  obtained  a  saturated  solution  of 
basic  lead  acetate.  To  prepare  chrome-yellow  enough  vinegar  is  added  to  obtain  an 
acid  reaction,  and  the  fluid  left  to  deposit  any  suspended  sediment.  At  the  same  time, 
in  another  tub,  a  solution  of  25  kilos,  of  potassium  bichromate  in  500  litres  of  water  is 
kept  in  readiness.  The  clear  lead  solution  is  next  poured  into  the  bichromate  solution 
as  long  as  any  precipitate  ensues.  This  precipitate  is  well  washed,  and  usually  mixed 
with  gypsum,  or  barium  sulphate,  to  obtain  the  lighter  chrome  colours ;  finally  it  is 
dried.  According  to  Liebig,  chrome-yellow  is  obtained  from  lead  sulphate,  an  almost 
useless  bye-product  from  calico-printing  and  dye-works,  by  digesting  it  with  a  warm 
solution  of  neutral  potassium  chromate.  The  depth  of  colour  of  the  ensuing  yellow  pig- 
ment depends  upon  the  quantity  of  lead  sulphate  which  is  converted  into  lead  chromate. 
The  white  lead  deposit  from  the  sulphuric  acid  chambers  is  too  impure  for  this  use. 

Dr.  Habich  states  that  there  exist  two  binary  compounds  of  lead  chromate  and 
sulphate,  the  formula  of  which  are  :— PbS04  +  PbCr04  and  2PbS04  +  PbCr04.  The 
former  is  obtained  when  a  solution  of  potassium  bichromate,  previously  mixed  with 
enough  sulphuric  acid  to  cause  its  dissociation,  is  precipitated  with  a  solution  of  lead; 
while  the  second  compound  is  formed  if  the  quantity  of  sulphuric  acid  is  doubled. 
When  dry  it  has  a  bright,  sulphur-yellow  colour  with  a  fiery  fracture.  According  to 
M.  Anthon  a  beautiful  chrome-yellow  is  obtained  by  the  digestion  of  100  parts  of 
freshly  precipitated  lead  chloride  with  47  parts  of  potassium  bichromate. 

Chrome-Red. — The  basic  lead  chromate,  known  as  chrome-red  and  Austrian  cin- 
nabar, PbCr04  +  PbH202,*  is  a  red-coloured  pigment  much  in  demand,  and  obtained 
from  the  yellow  or  neutral  lead  chromate,  either  by  boiling  it  with  a  caustic  potassa 
solution,  or  by  fusing  it  with  potassium  nitrate,  the  effect  being  that  half  of  the 
chromic  acid  is  withdrawn  from  the  neutral  chromate.  Liebig  and  Wb'hler  state  that 
chrome-red  is  best  obtained  by  fusing  together,  at  a  very  low  red-heat,  equal  parts  of 
potassium  and  sodium  nitrates,  gradually  pouring  into  the  fused  salt  small  quantities 
of  chemically  pure  yellow  lead  chromate.  After  cooling,  the  insoluble  chrome-red  is 
well  washed  and  dried.  It  is  then  a  magnificently  coloured  cinnabar-like  crystalline 
powder.  Dulong  prepares  chrome-red  by  precipitating  a  solution  of  lead  acetate  with 
a  solution  of  potassium  chromate  to  which  caustic  potassa  has  been  added.  The 
various  shades  and  qualities  of  chrome-red,  from  the  deepest  vermilion  to  the  palest 
red,  are  due  to  the  difference  in  size  of  the  constituent  crystalline  particles.  This 
fact  is  proved  by  experiment,  for  when  several  samples  are  uniformly  ground  to  a  fine 
powder  the  result  is  the  production  of  a  uniformly  deep-coloured  hue.  In  pre- 
paring chrome-red  of  a  deep  colour,  everything  which  might  interfere  with  or  injure 
the  crystallisation  has  to  be  avoided.  The  pigments  commercially  known  as  the 
chrome-orange  colours  are  mixtures,  in  varying  proportions,  of  the  basic  and  neutral 

*  According  to  Dr.  Duflos  (see  Handbuch  der  AngewandtenPharmaceutisch-Technisch  Chemischen 
Analyse.  &c.,  Breslau,  1871,  p.  293)  the  formula  of  this  substance  is,  2PbO,CrO,p  and  the  dried  salt 
does  not  contain  any  water  as  a  component  part. 


472  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

lead  chromates,  and  are  usually  made  by  boiling  chrome-yellow  with  milk  of  lime. 
M.  Anthon  recommends  for  the  preparation  of  a  good  chrome-orange  the  treatment  of 
loo  parts  of  chrome-yellow  with  55  parts  of  potassium  chromate  and  12  to  18  parts  of 
caustic  lime  made  into  milk  of  lime. 

Chromic  Oxide  or  Chrome-Green. — This  substance,  Cr203,  is  used  in  glass-  and 
porcelain-staining  as  a  couleur  grand  feu,  that  is  to  say,  it  stands  the  most  intense  heat, 
provided  no  reducing  materials  are  allowed  to  affect  it.  It  is  commercially  known 
under  the  name  of  chrome-green  as  an  indelible  pigment  for  printing,  being  especially 
employed  for  bank-notes.  It  is  prepared  in  various  ways,  the  finest  being  obtained  by 
heating  mercurous  chromate,  but  this  method  is  far  too  expensive  to  admit  of  any 
extensive  application.  Lassaigne  heats  equal  molecules  of  sulphur  and  yellow  potas- 
sium chromate,  and  exhausts  the  mixture  with  water,  leaving  the  insoluble  green 
sesquioxide  behind.  Wohler  prefers  to  mix  the  yellow  potassium  chromate  with 
sal-ammoniac,  to  heat  that  mixture,  and  afterwards  treat  it  with  water,  leaving  the 
insoluble  chrome-green  as  a  fine  powder. 

Among  other  methods  of  preparing  the  anhydrous  sesquioxide  is  the  heating  of  an 
intimate  mixture  of  potassium  bichromate  and  charcoal.  The  hydrated  chromium 
oxide,  according  to  the  formula  Cr4H609,  is  met  with  in  the  trade  under  a  variety 
of  names,  and  often  contains  boric  or  phosphoric  acids,  not,  however,  as  an  essential 
constituent  (see  Schiitzenberger's  formula  for  Guignet's  green),  but  as  a  remnant 
of  imperfect  preparation.  This  hydrated  oxide,  the  preparation  of  which  so  as  to 
ensure  a  good  colour  is  rather  a  difficult  matter,  requiring  very  careful  manipulation, 
is  known  as  emerald  green,  Pannetier  green,  Matthieu-Plessy  green,  and  Arnaudon 
green.  The  pigment  is  used  as  an  artist's  colour  and  in  calico-printing  as  a  substitute 
for  Schweinfurt  green,  but  is  very  expensive. 

Guignet's  green  is  best  obtained  by  melting  together  potassium  dichromate  and 
crystalline  boric  acid  at  a  red  heat.  The  melted  mass  is  lixiviated  with  hot  water, 
and  the  residue  finely  ground. 

In  an  English  manufactory  8  parts  of  boric  acid  and  3  parts  potassium  dichromate 
are  finely  pulverised,  well  mixed,  and  heated  for  four  hours  to  dull  redness  in  a  reverbe- 
ratory.  The  burnt  mass  must  have  a  peculiar  green  tone,  which  can  be  recognised  only 
by  long  experience.  In  any  case  the  mass  must  have  no  (or  but  few)  yellow  or  brown 
rusty  spots ;  if  these  are  abundant  the  entire  melt  is  worthless.  Such  spots  may  arise 
from  different  causes,  the  most  common  of  which  is  a  dirty  furnace,  or  too  high  a  tempera- 
ture. The  mass,  a  mixture  of  calcium  borate  and  chromic  oxide,  is  washed  to  remove 
the  former.  The  waters  from  the  two  first  washings  are  kept  apart  for  the  recovery  of 
the  boric  acid.  The  third  is  kept  to  be  used  for  the  first  washing  of  a  fresh  melt,  and 
the  further  waters  are  allowed  to  collect  in  a  cistern,  where  they  deposit  any  oxide  which 
may  have  been  carried  over.  The  washing  lasts  six  days.  The  mass  is  then  ground  in  a 
wet  mill,  and  washed  again,  being  mixed  up  with  water,  and  boiled  four  or  five  times  in 
the  course  of  the  day,  each  time  with  fresh  water.  Heat  is  applied  by  blowing  in 
steam.  The  mass  is  pressed,  yielding  a  product  which,  at  100°,  contains  33  per  cent, 
of  solid  matter,  and  after  ignition  26  per  cent. 

Chromic  Hydrate,  either  alone,  or  in  combination  with  boric,  phosphoric,  or  arsenic 
acid,  is  a  fine  green  pigment,  used  under  the  names  of  Mittler  green,  emerald  green, 
Pannetier  green,  Arnaudon  green,  Schnitz  green,  and  Matthieu-Plessy  green.*  It  is 
prepared,  according  to  Kothe,  by  treating  10  grammes  potassium  dichromate  with  a 
solution  of  1 2  grammes  sugar  in  i  oo  c.c.  of  water,  adding  30  c.c.  phosphoric  acid  of  sp.  gr. 
1-3,  and  the  solution  of  10  grammes  barium  chloride,  and  boiling  for  some  time. 

Dingler's  Green  is  a  mixture  of  chromium  and  calcium  phosphates. 

There  is  lamentable  confusion  in  the  momenclature  of  pigments. 


SECT,  in.]  COMPOUNDS   OF  IRON.  473 

Casali  Green  is  obtained  by  igniting  i  part  potassium  dichromate  and  3  parts  gypsum 
and  boiling  the  mass  in  very  dilute  hydrochloric  acid. 

Chrome  Alum. — This  salt,  •K.r»  [  4$O4  +  24H20,  is  obtained  in  rather  large   quan- 

iv2  j 

tities  as  a  bye-product  of  the  manufacture  of  aniline- violet,  aniline-green,  and  anthracene- 
red.  It  is  a  deep  violet-coloured  octahedrically  crystallised  substance,  now  used  to 
some  extent  as  a  mordant  in  dyeing,  for  rendering  gum  and  glue  insoluble,  for  water- 
proofing woollen  fabrics,  and  for  the  preparation  of  potassium  chromate. 

Chromium  Chloride. — This  compound,  Cr2Cl6,  best  prepared  by  the  decomposition 
of  chromium  sulphide  by  means  of  chlorine,  constitutes  a  crystalline  violet-coloured  mica- 
like  material,  employed  in  the  manufacture  of  coloured  paper  and  paper-hangings. 

Basic  Ferric  Chromate,  Fe2(Cr  04)3,  has  been  recommended  by  Kletzinsky  by  the 
name  of  siderine  yellow  as  a  water-  and  oil-colour,  drying  very  quickly.  It  is  obtained 
by  heating  a  solution  of  potassium  dichromate  mixed  with  neutral  ferric  chloride.  It 
forms  a  fiery  red  precipitate,  which  is  carefully  washed  and  dried. 

IKON  COMPOUNDS,   INCLUDING  FERROCYANOGEN. 

Copperas  or  Green  Vitriol. — The  substance  called  copperas  and  green  vitriol, 
ferrous  sulphate  (FeSO4  +  7H20),  is  met  with  in  trade  in  the  form  of  greenish- 
coloured  crystals  possessed  of  an  inky  astringent  taste ;  on  exposure  to  dry  air  the 
crystals  effloresce,  and  are  gradually  converted  into  a  yellowish  powder — basic  ferric 
sulphate.  100  parts  of  the  chemically  pure  crystallised  salt  consist  of — 

2 6'  10  parts  of  ferrous  oxide. 

29^90          „     sulphuric  acid. 

44-oo          „     water. 

Preparation  of  Green  Vitriol  as  a  Eye-product  in  Alum  Works. — Since  the  minerals 
ordinarily  used  in  the  manufacture  of  alum — the  alum  schists — generally  contain  iron 
pyrites  (FeS2),  either  as  such  or  already  partly  converted  into  a  basic  sulphate  of  the 
peroxide  (which  on  being  treated  along  with  the  alum  shale,  becomes  by  weathering 
and  roasting  converted  into  iron  protosulphate  and  peroxide),  green  vitriol  is  frequently 
a  bye-product  of  alum  manufacture,  and  is  obtained  by  evaporating  the  mother  liquor 
containing  iron,  and  leaving  it  to  crystallise.  In  some  localities,  as,  for  instance,  at 
Goslar  (Prussia),  on  the  Hartz  mountains,  the  liquor  obtained  by  the  lixiviation  of 
the  iron-containing  minerals  alluded  to  is  first  evaporated  for  the  separation  of  the 
green  vitriol,  then  a  potassium  or  ammonium  salt  is  added  to  the  remaining  acid 
liquid  to  obtain  alum. 

Preparation  of  Green  Vitriol  in  Beds. — The  material  sometimes  rather  largely  found 
in  coal  pits,  and  called  brasses  (iron  pyrites),  is  collected  and  placed  in  layers  over  a 
somewhat  excavated  surface,  which  has  been  rendered  impervious  to  water  by  puddling 
with  clay,  and  made  to  incline  slightly  in  one  direction,  where  water-tight  tanks  stand, 
into  which  scraps  of  old  iron  are  placed  with  the  view  of  saturating  any  free  acid ;  the 
pyrites,  placed  on  these  beds  to  a  thickness  varying  from  i^.to  3^  or  4  feet,  is  slowly 
oxidised  by  atmospheric  agency,  and  the  falling  rain  carries  into  the  tanks  a  more  or 
less  strong  solution  of  copperas,  which,  when  sufficiently  concentrated,  is  slowly 
evaporated,  some  scrap-iron  being  placed  in  the  evaporating-pans. 

Green  Vitriol  from  the  Residues  of  Pyrites  Distillation. — In  countries  where  iron 
pyrites  abounds,  and  fuel  and  labour  are  sufficiently  cheap  to  make  the  distillation  of 
sulphur  from  pyrites  a  profitable  business,  the  residues  are  utilised  in  green  vitriol 
making,  a  salt  which  thus  made  must,  of  necessity,  contain  a  good  deal  of  impurity. 

Green  Vitriol  from  Metallic  Iron  and  Sulphuric  Acid. — The  brown  sulphuric  acid  or 
chamber  acid,  also  such  waste  sulphuric  acid  liquids  as  are  obtained  in  the  oil  and 


474 


CHEMICAL  TECHNOLOGY. 


[SECT.    III. 


petroleum  refining,  are  sometimes  used  as  solvents  for  scrap-iron  for  the  preparation 
of  green  vitriol,  which  may  also  be  made  by  boiling  the  finely  pulverised  puddling  and 
iron  refining  slags  with  sulphuric  acid. 

Green  Vitriol  from,  Spathic  Iron  Ore. — In  localities  where  spathic  iron  (ferrous  car- 
bonate, FeCO3)  occurs  in  a  pure  state,  that  mineral  may  be  usefully  applied  to  the 
preparation  of  green  vitriol  by  treatment  with  sulphuric  acid,  and  evaporating  the 
solution  thus  obtained.  The  ferrous  sulphate,  prepared  on  the  large  scale,  is  often, 
met  with  crystallised  round  a  small  thin  stick  of  wood,  which  is  hung  up  in  the  solu- 
tion to  promote  crystallisation  ;  sometimes,  at  least  abroad,  a  so-called  black  vitriol  is 
met  with,  which  is  simply  green  copperas  superficially  coloured  black  by  means  of 
some  astringent  decoction,  such  as  nut  galls. 

Uses  of  Green  Vitriol. — This  substance  is  employed  as  a  disinfectant,  as  a  mordant 
in  dyeing  and  calico  printing  for  various  black  and  brown  shades,  for  the  preparation 
of  ink,  the  deoxidation  of  indigo — in  the  so-called  cold  vat  used  for  cotton  dyeing — in 
gas  purifying,  in  the  precipitation  of  gold  from  its  solutions,  in  the  preparation  of 
Prussian  blue,  in  the  manufacture  of  fuming  (Nordhausen)  sulphuric  acid,  in  the 
treatment  of  sewage,  and  for  a  host  of  other  purposes. 

Iron  Minium  is  a  dark  red-brown  pigment,  consisting  chiefly  of  ferric  oxide.  It  is 
obtained  by  roasting,  sorting,  and  grinding  burnt  pyrites. 

Potassium  Ferrocyanide. — The  yellow-coloured  salt,  generally  known  as  yellow 
prussiate  of  potassa  (potassium  ferrocyanide,  K4FeCy6  +  3H20),  is,  in  a  technical  point 
of  view,  a  very  important  substance.  It  crystallises  in  large  lemon-coloured  prismatic 
crystals,  which  are  not  affected  by  exposure  to  air,  are  not  poisonous,  and  possess  a 
sweetish  bitter  taste.  This  salt  is  soluble  in  4  parts  of  cold  and  2  of  boiling  water, 
but  is  insoluble  in  alcohol;  in  100  parts  there  are — 

37 '03  Potassium 

1 7 '04  Carbon      )  .-, 

\  Cyanogen. 
19-89  Nitrogen   j     ' 

13-25  Iron 
1279  Water 

At  100°  the  water  is  driven  off.  The  salt  is  prepared  on  a  large  scale  by  igniting 
such  carbon  as  contains  nitrogen  to  a  red  heat  with  potassium  carbonate  in  closed  vessels. 
The  quantities  of  the  materials  may  be  varied,  the  relative  proportions  being  given  by 
some  makers  as  100  parts  of  potassium  carbonate  to  75  of  the  nitrogenous  carbon,  or, 
according  to  Runge,  100  parts  of  potassium  carbonate,  400  of  torrified  horn,  and  10  parts 
of  iron  filings.  The  nitrogenous  materials  used  are  horns,  hoofs,  blood,  wool-dust, 
cuttings  of  hides,  and  leather. 

The  fusion  of  these  ingredients  is  carried  on  either  in  closed  iron  vessels  of  a 


Fig-  374- 


Fig-  375- 


peculiar  shape,  or  in  a  reverberatory  furnace.     The  iron-vessel,  a,  termed  a  muffle, 
(Fig.  374),  is  egg-  or  pear-shaped,  having  a  diameter  of  1-2  metre,  a  width  of  0*8  metre, 


SECT,  in.]  COMPOUNDS   OF   IRON.  475 

and  varying  from  12  to  15  centimetres  in  thickness,  with  a  short,  wide  neck  in  front. 
As  shown  in  the  woodcut,  the  iron  vessel  is  placed  in  the  furnace  in  such  a  manner  as 
to  be  exposed  to  the  action  of  the  flame  and  hot  gases  on  all  sides,  being  supported 
at  the  back  by  a  projection  about  27  centimetres  long,  and  resting  at  g  on  the  brick- 
work, leaving  space  sufficient  for  the  gases  generated  in  the  interior  to  pass  off  by  c 
into  the  chimney-flues  ;  m  is  an  iron  cover  which  is  closed  during  the  operation  of  melt- 
ing, g  being  an  opening  in  the  front  wall  of  the  furnace,  through  which  the  ingredients 
are  put  into  the  iron  vessel,  and  the  molten  mass  taken  out.  The  shallow  pan,  i,  on 
the  top  of  the  furnace,  is  intended  for  the  evaporation  of  the  liquor  obtained  by  treating 
the  molten  mass  with  water.  The  use  of  the  iron  vessel,  however,  is  attended  with  the 
serious  drawback  that  the  iron  is  eaten  into  holes  in  a  comparatively  short  space  of  time ; 
and,  though  this  action  is  greatest  on  the  lower  part  of  the  vessel,  and  it  may  there- 
fore be  turned  bottom  upwards,  and  the  holes  stopped  with  fire-clay,  the  vessel  has 
soon  to  be  replaced  by  another.  It  is  on  this  account,  and  also  owing  to  the  fact  that 
a  larger  quantity  of  raw  material  can  be  operated  upon  at  once,  that  instead  of  the 
apparatus  described  above,  there  has  come  into  general  use  a  reverberatory  furnace, 
^ig-  375>  arranged  with  a  shallow  cast-iron  pan,  a,  from  i  to  i'8  metre  in  diameter, 
with  a  rim  about  i  decimetre  high  ;  b  is  the  fire-place  ;  g,  the  bridge ;  c,  a  flue  leading 
to  the  chimney,  e.  Sometimes  the  hot  air  is  applied  to  the  heating  of  evaporating  pans, 
being  carried  under  them  before  entering  the  chimney.  The  result  of  the  ignition  is 
the  formation  of  a  black  mass,  technically  called  the  metal,  yielding  the  liquor  from  which 
the  crude  salt  crystallises.  The  salt  is  purified  by  re-crystallisation,  while  the  black 
residue  is  employed  as  a  manure  and  for  decolorising  paraffine,  &c. 

The  theory  of  the  formation  of  the  potassium  ferrocyanide  is  as  follows : — The  car- 
bonate and  potassium  sulphate,  the  nitrogenous  coal  and  the  iron  reacting  upon  each 
other,  give  rise  to  the  formation  first  of  potassium  sulphide,  which  in  its  turn  converts 
the  iron  into  sulphide,  while  the  nitrogen  contained  in  the  charcoal  unites,  under  the 
influence  of  potassium,  with  the  cyanogen  of  the  carbon,  which  again  in  its  turn  com- 
bines with  the  potassium,  giving  rise  to  the  formation  of  potassium  cyanide.  When 
the  fused  mass  is  treated  with  water,  potassium  cyanide  and  sulphide  of  iron  decompose 
each  other,  the  result  being  the  formation  of  potassium  ferrocyanide  and  sulphide, 
the  last-named  salt  remaining  in  the  mother  liquor.  M.  E.  Meyer  states  (1868)  that 
it  is  more  advantageous  to  employ,  instead  of  the  iron  sulphide,  the  carbonate  of 
that  metal,  for  the  purpose  of  converting  cyanogen  into  ferrocyanogen,  because  the 
potassium  ferrocyanide  crystallises  far  more  completely  and  freely  from  solutions  not 
containing  any  potassium  sulphide.  Liebig  has  since  proved  that  the  fused  mass  only 
contains  potassium  cyanide  and  metallic  iron,  and  not  any  potassium  ferrocyanide, 
which  is  only  formed  by  treating  the  molten  mass  with  water,  or  more  slowly  by  its 
exposure  to  moist  air.  Among  the  materials  frequently  added  to  the  fusing  mass 
are — scraps  of  metal,  the  refuse  of  leather,  dried  blood  and  other  dry  animal  offal, 
because  the  ammonia  evolved  by  their  decomposition  in  the  presence  of  ari  alkali  aids 
the  formation  of  potassium  cyanide.  According  to  M.  P.  Havrez,  the  crude  suint 
obtained  from  wool  is  an  excellent  material  for  the  preparation  of  potassium  ferro- 
cyanide,  since  100  kilos,  of  the  suint  contain  about  40  kilos,  of  potassium  carbonate, 
from  i  to  2  kilos,  of  potassium  cyanide,  and  about  50  kilos,  of  combustible  hydro- 
carbons, the  heating  value  of  which  is  at  least  equal  to  that  of  40  kilos,  of  coal. 

Attempts  have  been  made  to  obtain  the  potassium  cyanide  on  a  large  scale,  by  caus- 
ing a  current  of  ammoniacal  gas  to  pass  through  and  over  potassium  carbonate  heated 
to  redness ;  and  also  to  obtain  potassium  cyanide  from,  or  by  aid  of,  the  nitrogen  of 
the  atmosphere.  This  process  was  tried  nearly  forty  years  ago  at  Bramwell's  works 
iiear  Newcastle-on-Tyne,  but  was  found  to  be  a  failure  commercially.*  As  it  has 

*  Compare  Richardson  and  Watts'  Chemical  Technology. 


CHEMICAL  TECHNOLOGY. 


[SECT.  in. 


been  proved  by  experiment  that  baryta,  far  more  readily  than  potassa,  converts 
carbon  and  nitrogen  into  cyanogen,  forming  barium  cyanide  at  a  lower  temperature, 
baryta  might  perhaps  be  substituted  for  potassa,  but  as  yet  this  plan  is  not  carried 
out  commercially.  According  to  Gelis  (1861),  the  yellow  prussiate  may  be  prepared 
by  the  mutual  reaction  of  carbon  sulphide  and  ammonium  sulphide,  the  resulting 
sulphocarbonate  being  converted  into  potassium  sulphocyanide  by  means  of  potassium 
sulphuret,  by  which  reaction  ammonium  sulphide  and  sulphuretted  hydrogen  are  vola- 
tilised. The  potassium  sulphocyanide  is  next  converted  into  ferrocyanide  by  being 
heated  with  metallic  iron  to  redness,  iron  sulphide  being  at  the  same  time  formed. 
It  is  evident  that  this  process  could  not  be  carried  out  commercially.  Mr.  H.  Fleck 
described,  in  1863,  a  plan  for  preparing  the  ferrocyanide  by  the  action  of  a  mixture 
of  ammonium  sulphate,  sulphur  and  carbon,  upon  fusing  potassium  sulphide,  which 
thus  becomes  potassium  sulphocyanide,  one-half  of  the  nitrogen  of  the  ammonium 
sulphate  remaining  in  the  fused  metal  as  cyanogen,  while  the  other  half  escapes 
as  ammonium  sulphide,  which  is  again  converted  into  ammonium  sulphate.  The 
potassium  sulphocyanide  produced  is  treated  with  metallic  iron  at  a  red-heat,  and 
thus  potassium  cyanide  and  iron  sulphide  are  produced.  This  process  is  also  too 
cumbrous  and  expensive  on  a  large  scale. 

Applications  of  the  Yellow  Prussiate. — This  salt  is  employed  in  the  manufacture  of 
the  ferricyanide  or  red  prussiate,  in  the  preparation  of  Berlin  blue,  and  of  potassium 
cyanide  (the  impure  salt  as  met  with  in  commerce),  in  dyeing  and  calico-printing  for 
the  production  of  blue  and  brown -red  colours,  for  the  purpose  of  surface-hardening 
small  iron  articles,  as  an  ingredient  of  white  gunpowder,  and  for  use  in  chemical 
laboratories. 

Great  loss  is  experienced  in  the  manufacture  of  ferrocyanide  because  the  nitro- 
genous organic  matter  floats  and  burns  upon  the  surface  of  the  melting  potash,  whilst 
the  nitrogenous  gases  only  pass  through  a  thin  layer  of  potash,  so 
that  a  part  escapes  without  being  utilised.  To  prevent  this  the 

N  potash  is  melted  in  the  pan  E  (Fig.  376),  2  metres  high,  and  0*6 

metre  wide,  and  the  nitrogenous  bodies  are  pressed  down  to  the 
bottom  by  a  plunger,  n.  This  plunger  consists  of  a  strong  bor- 
dered plate  of  metal  with  several  perforations,  its  rod,  d,  being 
raised  and  lowered  by  means  of  a  counterpoise.  In  working,  300 
kilos,  of  potash  are  melted  in  the  cylinder,  the  plunger  is  raised, 
and  the  nitrogenous  matters  are  introduced  through  b.  The  mass 
is  forced  to  the  bottom  by  lowering  the  plunger.  The  intro- 
duction of  the  nitrogenous  matter  continues  until  all  is  melted 
up.  The  heat  is  then  raised  for  a  short  time ;  the  melt  is  drawn 
off  at  e  into  a  truck,  and  a  new  charge  is  introduced.  The 
ammonia  in  the  vapours  is  condensed  in  a  scrubber. 

For  obtaining  ferrocyanide  from  Laming's  mass,  Kunheim 
dissolves  out  the  ammonia  with  water  and  the  free  sulphur  with 
carbon  disulphide.  It  is  then  mixed  with  dry  lime.  The  dry 
mixture  is  then  either  heated  from  40°  to  100°  in  a  closed  vessel, 
with  constant  stirring  to  expel  any  undissolved  ammonia,  the 
escaping  vapours  being  passed  through  a  scrubber,  and  the  mass 
then  submitted  to  methodical  lixiviation  with  water,  or  the  lixiviation  is  applied  first, 
yielding  an  ammoniacal  lye  of  calcium  ferrocyanide.  This  lye  is  carefully  neutralised  and 
heated  to  the  boiling  point,  when  a  sparingly  soluble  compound  is  deposited,  calcium- 
ammonium  ferrocyanide.  It  is  treated  with  lime  in  closed  vessels  ;  the  compound  is 
decomposed  ;  the  escaping  ammonia  is  secured  in  the  usual  manner,  and  a  pure  lye  of 
calcium  ferrocyanide  is  obtained.  It  is  utilised  as  Prussian  blue  by  treatment  with 


Fig.  376. 


SECT,  in.]  COMPOUNDS  OF   IKON.  477 

ferrous  salts  and  subsequent  evaporation.  If  potassium  ferrocyanide  is  to  be  produced, 
calcium -potassium  ferrocyanide  is  first  formed  by  evaporating  and  adding  so  much 
potassium  chloride  as  is  sufficient  for  forming  CaK2FeCy6.  The  double  cyanide  sepa- 
rates out,  is  filtered  off,  washed,  and  boiled  with  potassium  carbonate,  which  converts  it 
into  potassium  ferrocyanide. 

Potassium  Ferricyanide. — The  red  prussiate  of  potassa,  properly  potassium  ferri- 
cyanide,  or  Gmelin's  salt,  KgFeCy,  is  prepared  on  a  large  scale  and  extensively  used 
in  dyeing  and  calico-printing.  This  salt  crystallises  in  prismatically  shaped  ruby -red- 
coloured,  anhydrous  crystals,  which  consist  in  100  parts  of — 

35-58  Potassium 

21 '61  Carbon       )  -, 

0  ,  [  Cyanogen 

25-54  Nitrogen   )    ' 

17-29  Iron. 

It  is  prepared  by  submitting  either  the  solution  of  the  yellow  prussiate  or  that  salt  in 
powder  to  the  action  of  chlorine  gas  until  a  sample,  when  heated,  yields  no  precipitate 
with  a  solution  of  a  ferric  salt.  When  the  dry  and  pulverised  yellow  prussiate  is 
acted  upon  by  chlorine  gas,  the  salt  is  frequently  placed  in  casks,  closed  so  as  only  to 
leave  a  small  outlet,  while  the  vessel  can  be  made,  by  means  of  machinery,  to  turn 
slowly  on  its  axis,  so  as  to  bring  all  the  particles  of  the  salt  into  contact  with  the 
chlorine.  Sometimes,  again,  the  pulverised  yellow  prussiate  is  placed  on  trays  in  a 
chamber,  into  the  top  of  which  chlorine  gas  is  admitted ;  when  no  more  chlorine  is 
absorbed  the  newly  formed  salt  is,  if  a  solution  of  the  yellow  prussiate  has  been 
operated  upon,  evaporated  to  dryness,  or  in  the  case  where  the  dry  powder  of 
the  salt  has  been  taken,  the  newly  formed  salt  is  dissolved  in  the  smallest  possible 
quantity  of  water,  and  the  solution  left  to  crystallise,  the  mother  liquor  containing 
potassium  chloride.  This  reaction  is  represented  by — 

K4FeCy6  +  01  =  KOI  +  K3FeCy6. 
Yellow  prussiate.  Red  prussiate. 

The  powdered  red  prussiate  is  of  an  orange-yellow  colour.  According  to  M.  E. 
Reichardt  (1869),  bromine  may  be  successfully  employed  instead  of  chlorine  for  the 
preparation  of  this  salt,  which  is  chiefly  used  for  dyeing  woollen  fabrics  blue,  and,  with 
solutions  of  caustic  soda  or  potassa,  for  the  Mercerising  process  of  cotton. 

Potassium  Cyanide,  KCy. — This  salt  is  obtained  in  an  impure  state — Liebig's  or 
crude  potassium  cyanide — by  the  fusion  of  the  yellow  potassium  prussiate  in  a  porce- 
lain crucible,  continued  as  long  as  nitrogen  escapes.  Iron  carbide  sinks  to  the  bottom 
of  the  crucible,  while  the  crude  cyanide  is  poured  off  in  a  state  of  fusion — 

(K4FeCy6  =  4KCy  +   FeC2  +2N). 

According  to  Liebig's  plan,  the  potassium  cyanide  is  prepared  by  fusing  i  mol.  of 
potassium  ferrocyanide  with  i  mol.  of  potassium  carbonate;  by  this  method 
10  parts  of  the  ferrocyanide  yield  8'8  potassium  cyanide,  mixed  with  2' 2  parts 
potassium  cyanate.  For  all  technical  and  industrial  purposes  it  is  far  cheaper  to  use 
cyan-salt,  a  mixture  of  the  potassium  and  sodium  cyanides,  prepared  by  fusing 
together  8  parts  of  previously  dried  (anhydrous)  potassium  ferrocyanide  and  2  parts 
of  sodium  carbonate.  As  this  mixture  fuses  readily,  the  iron  carbide  easily  sepa- 
rates ;  moreover,  the  salt  thus  obtained  is  less  liable  to  decomposition  on  exposure  to 
air,  and  its  preparation  requires  less  heat.  The  industrial  applications  of  the  crude 
potassium  cyanide,  or  of  the  cyan-salt,  are  the  following  : — In  the  process  of  electro- 
gilding,  for  the  preparation  of  Grenat  soluble,  potassium  isopurpurate,  from  picric  acid, 
and  in  the  reduction  of  metals.  It  has  been  mentioned,  while  treating  of  the  blast- 
furnace process,  that  potassium  cyanide  is  formed  during  the  reduction  of  iron. 

Prussian  Blue. — This  substance,  so  named  when  it  was  accidentally  discovered  at 


478  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

Berlin,  in  1710,  by  Diesbach,  is  chemically  an  iron  ferrocyanide,  more  correctly  ferrous- 
ferric  cyanide.  A  distinct  variety  of  this  substance  is  known  as  Paris  blue.  Three 
different  kinds  of  Berlin  blue  are  known,  viz.,  neutral,  basic,  and  a  mixture  of  the  two, 
differing  in  composition  and  prepared  by  different  processes. 

(a)  Neutral  Berlin  blue,  also  known  as  Paris  blue,  is  obtained  by  pouring  a  solution 
of  yellow  prussiate  into  a  solution  of  iron  chloride,  or  into  a  solution  of  a  peroxide 
salt  of  iron ;  the  result  is  the  formation  of  a  large  quantity  of  a  magnificently  blue- 
coloured  precipitate,  very  difficult  to  wash  out,  and  always  retaining  a  certain  quantity 
of  the  yellow  prussiate,  which  cannot  be  removed  by  washing. 

(6)  Basic  Berlin  blue  is  obtained  by  precipitating  a  solution  of  yellow  prussiate 
with  a  solution  of  a  ferrous  salt  (green  copperas),  the  result  being  at  first  the  forma- 
tion of  a  white  precipitate  of  ferrous  cyanide,  which,  either  by  exposure  to  air,  or  by 
the  action  of  oxidising  substances,  becomes  blue ;  because  a  portion  of  the  iron  is 
oxidised  and  another  portion  takes  up  the  cyanogen  thus  liberated,  converting  some  of 
the  ferrous  cyanide  into  the  corresponding  ferric  salt,  which  in  its  turn  combines  with 
the  unattacked  protocyanide  to  form  Berlin  blue,  with  which,  however,  some  ferric  oxide 
remains  mixed.  It  is  stated  that  basic  Berlin  blue  is  distinguished  from  neutral  Berlin 
blue  by  being  soluble  in  water ;  but  this  solubility  is  due  to  the  presence  of  some  of  the 
yellow  prussiate,  and  is  not  a  property  inherent  in  the  basic  Berlin  blue  in  a  pure  state. 

(c)  As  the  materials  employed  on  a  large  scale  are  neither  pure  ferrous  nor  pure 
ferric  salts,  but  a  peroxide  containing  protosalt  of  iron,  the  precipitate  obtained 
consists  at  first  of  a  mixture  of  neutral  Berlin  blue  with  more  or  less  of  the  white 
ferrous  cyanide,  which  afterwards  becomes  basic  Berlin  blue ;  accordingly  the  Berlin 
blue  of  commerce  is  a  variable  mixture  of  neutral  and  basic  Berlin  blues.  The  iron 
salt  employed  is  green  copperas  (ferrous  salt),  which  of  course  should  not  contain 
any  appreciable  amount  of  copper,  the  salts  of  this  metal,  as  is  well-known,  yielding 
with  yellow  ferrocyanide  a  chocolate-brown  coloured  precipitate. 

Old  Method  of  Preparing  Prussian  Blue. — Ferrous  sulphate  and  alum  are  dis- 
solved together  in  boiling  rain-  or  river- water  ;  the  fluid,  while  yet  hot,  is  decanted 
from  any  sediment  and  forthwith  poured  into  a  hot  aqueous  solution  of  ferrocyanide, 
care  being  taken  to  stir  the  mixture,  and  to  add  the  copperas  and  alum  solution  as 
long  as  any  precipitate  is  formed.  The  liquor  is  run  off,  and  the  precipitate  washed 
with  fresh  water,  until  all  the  potassium  sulphate  is  removed ;  after  which  the  preci- 
pitate is  drained  on  filters  made  of  coarse  canvas.  This  having  been  accomplished,  the 
substance  is  suspended  in  water  in  a  boiler,  and,  while  being  heated  to  the  boiling- 
point,  nitric  acid  is  added  ;  after  a  few  minutes'  boiling,  the  contents  of  the  boiler  are 
poured  into  a  large  wooden  tub  or  cask,  and  strong  sulphuric  acid  is  added.  The 
solution  is  now  allowed  to  stand  for  some  time,  during  which  the  blue  colour  fully 
develops.  The  Berlin  blue  is  then  thoroughly  washed  with  water,  drained  on  coarse 
canvas  filters,  next  dried,  pressed,  and  cut  into  cakes  ;  finally  it  is  dried  in  rooms  heated 
to  80°.  As  Berlin  blue,  when  once  quite  dry,  is  reduced  to  powder  with  great  diffi- 
culty, and  cannot  be  brought  to  the  state  of  fine  division  as  when  first  precipitated,  it 
is  also  sent  into  the  market  in  the  state  of  paste.  The  alumina  derived  from  the  alum 
is  so  intimately  mixed  with  the  blue  that  the  bulk  of  the  mass  is  thereby  increased 
without  any  very  perceptible  decrease  in  the  intensity  of  the  colour.  If  the  quantity 
of  alumina  is  very  much  increased,  the  colour,  of  course,  becomes  much  lighter,  and 
this  variety  of  Berlin  bluo  is  then  known  as  mineral  blue  ;  a  name  also  given  to  a  pre- 
paration of  copper  obtained  either  from  the  native  hydrated  copper  carbonate,  or  artifi- 
cially prepared  by  precipitating  copper  nitrate  or  chloride  by  means  of  lime  and  chalk.* 

*  The  presence  of  alumina  is  essentially  an  adulteration  which  may  be  detected  by  comparison 
with  a  genuine  sample  and  observing  how  much  of  any  inert  white  powder  may  be  added  to  the 
latter  to  bring  it  down  to  the  same  shade  as  the  former. 


SECT.  HI.]  COMPOUNDS  OF   IRON.  479 

Recent  Methods  of  Preparing  Berlin  Blue. — Among  the  improvements  made  more 
recently,  we  may  briefly  notice  the  following : — i.  The  mixing  of  the  solutions  of 
copperas  and  alum  with  that  of  yellow  prussiate  is  effected  as  above  described,  but  great 
care  is  taken  to  prevent  any  oxidation  of  the  white  precipitate,  which  is  converted  into 
an  intense  blue  by  being  treated  with  nitro-hydrochloric  acid,  the  chlorine  evolved 
serving  as  an  oxidising  agent.  The  remaining  operations,  viz.,  washing,  drying,  &c., 
are  performed  as  in  the  former  methods.  2.  Ferric  chloride  solution  is  employed  for 
the  purpose  of  converting  the  white  precipitate  into  blue,  while  the  ferrous  chloride 
thus  formed  serves  at  a  subsequent  operation  instead  of  ferrous  sulphate.  3.  In 
some  cases  manganic  chloride  (Mn,016),  is  applied ;  likewise  a  solution  of  chromic 
acid,  a  mixture  of  potassium  dichromate  and  sulphuric  acid  ;  but  it  is  self-evident  that 
the  application  of  any  of  these  improvements  is  dependent,  as  regards  success  in  a 
commercial  point  of  view,  upon  local  conditions,  and  upon  the  possibility  of  advan- 
tageously obtaining  the  various  ingredients. 

Turnbull's  Blue. — By  mixing  together  a  solution  of  red  prussiate  and  of  ferrous 
sulphate  in  such  proportions  as  to  prevent  the  entire  saturation  of  the  former  salt, 
there  is  obtained  a  blue-coloured  precipitate,  known  in  commerce  as  Turnbull's  blue, 
consisting  of  FesFejCyl8,  but  also  containing  some  chemically  combined  ferrocyanide. 

Berlin  Blue  as  a  Bye-Product  of  the  Manufactures  of  Coal- Gas  and  Animal  Charcoal. 
—  MM.  Mallett  and  Gautier-Bouchard  have  proved  experimentally  that  Berlin  blue  mav 
be  obtained  as  a  bye-product  of  coal-gas  manufacture  from  the  ammoniacal  liquor,  from 
the  spent  lime  of  the  purifiers,  and  from  Laming's  purifying  mixture.  The  spent 
lime  contains,  in  addition  to  the  calcium  and  ammonium  cyanides,  a  good  deal  of  free 
ammonia,  mechanically  absorbed  in  the  moist  lime.  Free  ammonia  is  first  removed  by 
forcing  steam  through  the  lime,  and  collecting  the  ammoniacal  gas  in  dilute  sulphuric 
acid.  The  lime  is  next  washed  with  water,  and  the  liquor  obtained,  containing  the 
cyanogen  compounds,  is  employed  for  the  manufacture  of  Berlin  blue.  According  to 
M.  KrafFt's  experiments,  1000  kilos,  of  spent  gas-lime  yield,  when  treated  as  described, 
from  12  to  15  kilos,  of  Berlin  blue,  and  from  15  to  20  kilos,  of  ammonium  sulphate. 
Mr.  Phipson  states  that  i  ton  of  Newcastle  gas-coal  yields  a  quantity  of  cyanogen 
which  corresponds  to  from  5  to  8  Ibs.  of  Berlin  blue.  The  manufacture  of  animal 
charcoal  also  yields,  if  desired,  Berlin  blue  as  a  bye-product. 

Soluble  Berlin  Blue. — As  ordinary  Berlin  blue  is  quite  insoluble  in  water,  and  the 
basic  variety  is  only  soluble  in  the  presence  of  potassium  ferrocyanide,  these  pigments  are 
only  fit  for  use  as  paints,  and  the  discovery  of  the  solubility  of  pure  Berlin  blue  in  oxalic 
acid  is  of  some  importance,  for  thereby  its  employment  as  a  water-colour  becomes 
possible.  This  soluble  blue  is  obtained  by  digesting  the  Berlin  blue  of  commerce  for  one 
to  two  days,  with  either  strong  hydrochloric  acid  or  with  strong  sulphuric  acid,  which 
latter,  after  having  been  mixed  with  the  Berlin  blue  previously  pulverised,  is  diluted 
with  its  own  bulk  of  water.  The  acid  is  next  decanted  from  the  sediment  of  blue,  and 
the  latter  thoroughly  washed  and  dried,  and  then  dissolved  in  oxalic  acid,  the  best  pro- 
portions being  8  parts  of  Berlin  blue,  treated  as  just  mentioned,  i  part  of  oxalic  acid, 
and  256  of  water.  According  to  other  directions,  Berlin  blue  readily  soluble  in  water 
can  be  obtained — i.  By  the  precipitation  of  ferrous  iodide  with  yellow  potassium 
prussiate,  care  being  taken  to  keep  the  latter  in  excess.  2.  By  mixing  a  solution  of 
ferric  chloride  in  alcoholic  ether  (tinctura  ferrichlorati  cetherea,  Ph.  Huss.)  with  an 
aqueous  solution  of  ferrocyanide. 

Pure  Berlin  blue  is  of  a  very  deep  blue  colour,  with  a  cupreous  gloss ;  it  is  insoluble 
in  water  and  alcohol,  is  decomposed  by  alkalies,  concentrated  acids,  and  by  heat.  The 
lighter  and  more  spongy  it  is,  the  better  is  its  quality ;  it  is  employed  as  a  pigment  and 
in  dyeing  and  calico-printing,  but  in  case  of  silks  and  woollens,  pigment-printing 
excepted,  it  is  obtained  on  the  tissues  by  a  circuitous  process.  The  Berlin  blue  of 


48o  CHEMICAL  TECHNOLOGY.  [SECT.  ni. 

commerce  is  frequently  adulterated  with  alumina,  pipe-clay,  kaolin,  magnesia,  heavy- 
spar,  and,  according  to  Pohl,  even  with  starch-paste  coloured  blue  by  means  of  tincture 
cf  iodine. 

CONSPECTUS  OF    INORGANIC  PIGMENTS. 

Whites. 

Bismuth  white,  pearl  white,  Spanish  white  (bismuth  oxychloride). 
China  clay,  kaolin. 

Hamburg  white,  Dutch  white,  Venice  white,  Tyrol  white  (white  lead  with  heavy- 
spar). 

Lithophan  (BaS04  +  ZnS). 

Permanent  white,  new  white,  mineral  white,  blanc  fixe  (BaS04). 
Pattinson's  white  lead  (basic  lead  chloride). 
Satin  white  (lime,  ZnO  and  a  little  indigo). 
Vienna  white,  Vienna  lime,  Bologna- lime  (prepared  chalk). 
White  lead,  Krems  white,  pearl  white,  silver  white  (lead  carbonates). 
White  lead  substitute :  Antimony  oxide. 
Zinc  carbonate. 

Zincoh'th,  Griffith's  snow  white  (zinc  sulphide  and  barium  sulphate). 
Zinc  white,  snow  white  (zinc  oxide). 

Beds. 

Antimonial  vermilion. 
Bloodstone  (Fe203). 
Chrome  red,  chrome  garnet,  chrome  vermilion,  chrome  carmine,  chrome  orange 

(basic  lead  chromate). 

Colcothar,  Paris  red,  English  red,  polishing  red,  iron  minium  (Fe203). 
Gold  purple,  Cassius'  purple. 

Mineral  lake,  pink  colour  (glass  flux  coloured  with  tin  chromate). 
Minium,    orange    minium,    Paris    red,    gold  cinnabar,    Saturn  cinnabar,  mineral 

orange  (Pb304). 

Ochre,  terra  di  sienna,  Naples  red,  red  bole,  ruddle  (ferruginous  clays). 
Realgar  (As2S2). 
Umber  (clayey-brown  iron  ore). 
Umber,  Colognese  (lignite). 
Vermilion,  cinnabar,  Chinese  red  (HgS). 

Yellows. 

Cadmium  yellow  (CdS).     Jaune  Brillant. 
Cassel  yellow,  Turner's  yellow  (lead  oxychloride). 
Chrome  yellow,  Paris  yellow,  Leipsic  yellow,  Hamburg  yellow,  crown  yellosv  (lend 

chromate). 
Cobalt  yellow. 
Litharge,  massicot. 
Mosaic  gold  (SnSf). 
Naples  yellow  (lead  antimoniate). 

Ochre,  gold  ochre,  Chinese  yellow,  Lemnian  earth  (clay  containing  ferric  hydrate). 
Orpiment  (As2S3). 
Siderine  yellow  (iron  phosphate). 
Ultramarine  yellow,  barium  yellow  (BaCr04). 
Zinc  yellow  (zinc  chromate). 


SECT,  in.]  THERMO-CHEMISTRY.  481 

Greens. 

Brunswick  green,  mountain  green  (chiefly  copper  carbonate). 

Bremen  green  (copper  hydrate). 

Casali  green  (chromic  oxide). 

Chrome  green,  emerald  green,  Guignet's  green,  Victoria  green  (chromic  oxide). 

Dingler's  green  (chromium  phosphate). 

Gentele's  green  (copper  stannate). 

Green  cinnabar,  Naples  green  (chrome  yellow  and  Prussian  blue). 

Malachite,  copper  green,  mountain  green  (copper  carbonate). 

Mittler  green,  emerald  green,  Pannetier's  green,  Arnaudon's  green,  Schnitzer  green, 

Matthieu  Plessy's  green  (chiefly  chromium  hydrate). 
Rinmann's  green,   cobalt  green,   Saxon   green,   Gellert's   green,   Scheele's  greenr 

Swedish  green  (copper  arsenite). 
Schweinfurt  green,  Mitis   green,  Neuwied   green,  Leipsic  green,  Vienna   green^ 

imperial  green,  royal  green,  Bale  green,  Kirschberg  green  (copper  aceto-arsenite). 
Ultramarine  green. 
Verdigris  (copper  acetate). 
Zinc  green  (zinc  yellow  and  Prussian  blue). 

Blues. 

Azurite,  mountain  blue,  copper  lazulite. 
Bremen  blue  (copper  hydrate). 

Berlin  blue,  Turnbull's  blue,  Erlangen  blue,  Hamburg  blue,  Milori  blue. 
Cerulean  blue  (cobaltous-stannic  oxide). 
Chrome  chloride  (violet). 

Cobalt  blue,  cobalt  ultramarine,  Leyden  blue  (alumina  cobaltate). 
Egyptian  blue  (copper  glass). 
Mineral  blue  (Prussian  blue  mixed  with  clay). 
Oil  blue,  copper  indigo  (copper  sulphide). 
Smalts,  kind's  blue  (cobalt-glass). 
Ultramarine. 

THERMO-OHEMISTRY. 

Thermo- chemistry,  the  doctrine  of  the  heat-processes  in  chemical  combinations  and 
decompositions,  does  not  yet  by  any  means  sufiice  to  explain  all  the  various  transforma- 
tions and  reactions  in  chemical  manufactures.  It  yields,  however,  already  a  basis  for 
the  greater  or  less  probability  of  the  practicability  of  certain  chemical  reactions,  as  in 
general  those  compounds  are  most  easily  produced  which  originate  with  the  liberation 
of  heat,  whilst  those  which  involve  the  absorption  of  heat  are  generally  much  more 
difficult  to  effect.  There  are,  indeed,  many  exceptions.  Thus,  in  the  formation  of 
ammonia  in  an  aqueous  solution  from  14  kilos.  N,  3  kilos.  H,  and  much  water  : 

N  +  Hs  +  aq  =  NH3.aq 

20,400  calories  (heat-units)  are  set  free,  and  yet  the  reaction  is  so  far  practically 
impossible. 

Thermo-chemistry  is  very  important  for  determining  the  consumption  of  heat  in 
the  chemical  arts,  as  we  can  can  only  decide  whether  it  is  possible  to  economise  fuel  by 
improvements  in  a  smelting-furnace,  a  decomposition-pan,  or  a  distilling  apparatus, 
if  we  first  know  the  actual  minimum  heat  needed  in  the  process  in  question.  If 
further  experience  enables  us  to  estimate  the  size  of  cooling-surfaces,  the  quantity  of 
coob'ng-water,  or  of  ice  in  obtaining  hydrochloric  or  nitric  acid,  for  regulating  certain 
processes  in  colour-works,  in  the  fermentation  trades,  &c.,  errors  are  often  committed 

2  H 


482  CHEMICAL   TECHNOLOGY.  [SECT.  in. 

in  this  respect,  as  the  plant  is  often  erected  too  large — and  consequently  too  costly — 
or,  what  is  generally  still  worse,  much  too  small.  The  right  proportions  of  size  can  only 
be  determined  in  advance  if  we  know  the  quantity  of  heat  which  must  be  produced  or 
removed.  Many  a  plant  must  be  altered  at  a  great  expense,  or  even  done  away  with, 
because  it  has  been  carried  out  on  a  basis  of  assumption,  not  of  calculation.  Such 
calculations  unfortunately  can  only  be  effected  in  part,  as  many  of  the  necessary  data 
are  still  wanting. 

As  a  unit  we  generally  take  the  quantity  of  heat  needed  to  raise  the  unit  weight 
of  water  from  p°  to  i°.  In  chemistry  there  is  generally  employed  as  a  unit  of  weight 
i  gramme,  and  the  unit  of  heat  is  known  as  a  calorie.  Berthelot  proposes  a  unit 
1000  times  greater.  Ostwald,  in  accordance  with  the  proposal  of  Schuller  and 
"Wartha,  takes  as  the  unit  K,  i.e.,  that  quantity  of  heat  which  i  gramme  water  loses 
between  the  boiling-point  and  the  freezing-point.  It  is  100  tunes  as  great  as  the 
specific  heat  of  water  between  15°  and  18°.  With  regard  to  the  variable  specific  heat 
of  water,  K  is  ioo'6  cal.  We  may  generally  put  i  cal.  (Berthelot's)  =  10  K  =  1000  col. 
For  technical  uses  it  is  preferable  to  use  the  kilo,  as  the  unit  of  weight ;  whether  we 
in  addition  take  the  specific  heat  of  water  at  o°  or  at  18°  is  seldom  of  moment  in  the 
calculations  which  here  come  into  question,  though  the  latter  value  is  preferable  since  the 
determinations  are  generally  effected  at  15°  to  18°.  As,  in  using  the  cal.,  decimal  places 
are  almost  always  reached,  and  with  K  very  frequently,  the  different  units  are  best 
given  up,  calculating,  in  round  numbers,  by  the  heat-unit  as  that  quantity  of  heat 
which  raises  i  kilo,  of  water  from  o°  to  i°  (or  from  17°  to  18°).  As  then  all  the 
calculations  are  carried  out  with  kilo.-molecular  weights,  but  with  cal.  for  gramme- 
molecular  weights,  the  numbers  in  both  cases  are  equal. 

According  to  the  general  equation  of  the  mechanical  theory  of  heat,  dQ  =  dTJ  +  dW, 
in  which  dQ,  is  the  heat  which  enters  or  passes  out,  dU  signifying  the  change  in  the 
internal  energy,  and  dW  the  external  work  ;  in  considerable  changes  of  space  the 
mechanical  work  is  to  be  considered.  When  gas  is  evolved  the  pressure  of  the  air  i 
to  be  overcome.  At  760  mm.  of  the  barometer  the  pressure  of  the  atmosphere  upon 
each  square  centimetre  of  surface  76  x  13-6  =  1033*6  grammes,  that  is,  10,336  kilos,  on 
i  square  metre.  As  425  kilogrammetres  are  the  mechanical  heat  equivalent  to  the  expan- 
sion of  i  cubic  metre,  10,336  :  425  =  24*3  heat-units.  As  the  kilo.-molecular  weight  of 
all  gases  =  22*3  cubic  metres,  in  the  development  of  i  kilo.-molecular  of  a  gas  at  o°, 
22-3  x  24-3  =  542  units  of  heat  are  consumed,  but  at  t°  542  (i  +  0*00367  t)  heat-units. 
In  the  development  of  oxygen,  2KC102  =  2KC1  +  202,  there  are  required  (if  the  oxygen 
in  the  apparatus  is  cooled  down  to  o°)  to  overcome  the  pressure  of  the  atmosphere  for 
the  3  x  32  =  96  kilos.,  or  3  x  22*3  =  66*9  cubic  metres  oxygen,  3  x  542  =  1626  heat-units  ; 
if  the  gas  escapes  at  20°,  1745  heat -units  are  required. 

This  heat  is  of  course  liberated  again  if  the  gases  are  absorbed,  as  in  the  oxidation 
of  Weldon  mud,  the  production  of  chloride  of  lime,  &c. 

In  degasifying  coals  in  the  generator,  there  are  required  to  overcome  the  pressure 
for  each  kilo,  of  coal  corresponding  to  0*3  cubic  metre  of  gas,  if  it  leaves  the  generator 
at  600°,  o'3  x  24-3  x  (i  +  0-00367)  =  24  heat-units. 

In  converting  coke  into  carbon  monoxide  there  is  also  an  increase  of  volume  as 
C,  +  0,  =  200,  and  C  +  H,O  =  CO  +  Hs. 

Let  us  take  as  an  instance  the  compounds  of  chlorine.  In  the  combination  of 
i  kilo.  Hwith  35-5  kilos.  01,  to  form  36*5  kilos.  HClr  there  are  liberated,  according  to 
Thomsen,  22,000  heat-units  ;  in  the  formation  of  solid  sodium  chloride  from  23  kilos, 
sodium  and  35*5  kilos,  chlorine  gas,  97,700  heat-units  ;  in  the  formation  of  sodium 
hydroxide  from  23  kilos,  sodium,  i  kilo,  hydrogen,  and  16  kilos,  oxygen,  101,900  heat- 
units,  whilst  the  reaction  Na2  +  0  =  Na20  furnishes  80,400  heat-units. 


SECT,  in.]  THERMO-CHEMISTRY,  483 

The  attempt  to  decompose  sodium  chloride  by  oxygen — 

2NaCl  +  O  =  Na20  +  01, 

—  195,400  +  80,400  =    -  1 15, ooo  heat-units, 

appears  futile  from  the  enormous  requirement  of  heat-units.  The  decomposition 
of  sodium  chloride  by  watery  vapour — 

NaCi    +     H20     =    NaOH    +    HC1 

—  97,700  —   57,000  +   101,900  +   22,000  =    —  30,800  heat-units, 
would  require  only  30,800  heat-units,  but  so  far  it  is  impracticable. 

General  attention  is  now  turned  to  the  production  of  chlorine  from  magnesium 
•chloride  by  ignition  in  a  current  of  air — 

MgCl2    +  0  =  MgO  +  01 

-151,000  +   144,000        =    -  7000  heat- units. 

But  if  we  assume  that  there  is  first  formed  from  the  moist  magnesium  chloride, 
magnesium  hydrate,  the  formation  heat  of  which  =  149,000  heat-units,  only  2000 
heat-units  are  required.  Pechiney  uses  oxychloride.  As  according  to  Andre  a  fused 
mixture  of  MgO  +  Mg012  gives  15,400  heat-units,  but  MgCl2.6H2O  +  MgO  -  600  heat- 
units,  it  may  be  in  part  understood  why  Pechiney's  mixture  in  its  production  must  not 
be  heated  above  300°. 

If  hydrochloric  acid  is  to  be  obtained  from  magnesium  chloride — 

Mg012      +    H2O      =     MgO     +    2HC1 

—  151,000  —  57,000  -*-  144,000  +  44,000  =  —  20,000  heat-units, 
there  are  required  20,000  heat-units.  Hence  this  process  as  regards  its  demand  for 
heat  is  less  favourable  than  the  production  of  chlorine,  because  the  formation-heat  of 
watery  vapour  is  greater  than  that  of  hydrochloric  acid.  The  case  is  still  more 
unfavourable  if  we  set  out  from  crystalline  magnesium  chloride,  since  in  the  formation 
of  MgCl2.6H2O  from  Mg012,  33,000  heat-units  are  liberated,  and  must  be  again  supplied 
during  the  decomposition.  The  evolution  of  hydrochloric  acid  on  heating  hydrated 
magnesium  chloride  has  not  hitherto  been  explained  solely  on  thermo-chemical 
procedures. 

The  oxidation  of  hydrochloric  acid  by  atmospheric  oxygen  according  to  Deacon's 
.process  seems  simple — 

2HC1    +    O    =   H2O     +    C12 
—  44,000  +  57,000  —  13,000  heat-units. 

If  the  sides  are  properly  isolated  this  temperature  suffices  to  keep  the  clay  at  the 
"temperature  required  without  any  especial  heating  of  the  mixture  of  hydrochloric 
acid  and  air.  The  size  of  the  subsequent  cooling-apparatus  depends  on  the  composition 
and  the  temperature  of  the  gaseous  mixture. 

That  chlorine  water  readily  passes  into  hydrochloric  acid  may  be  understood  from 
its  great  solution  heat  in  presence  of  much  water — 

H2O  +  C12  =  2H01.aq  +  O 
—  68,400  +   78,600  =  10,200  heat-units. 

In  order  to  render  the  demand  for  heat  in  the  Pechiney  decomposition  furnace  more 
intelligible,  let  it  be  supposed  that  the  composition  of  the  mixture  decomposed  at  1000°  is: 

MgCl2 47-5  per  cent. 

Mg   ......     30-0 

H20          .....     22-5 

Let  half  the  chlorine  escape  as  HC1 ;  200  kilos,  of  the  mass  would  then  yield — 

Cl 35-5  kilos. 

HC1          .....        .,  36-5      ,, 

H.,O  (vapour)    .         .        .         .     36*0      „ 

MgO loo-o      „ 

208 'o 


484  CHEMICAL  TECHNOLOGY.  [SECT.  in. 

In  addition,  8  kilos,  of  oxygen  have  been  consumed   from  200  cubic  metres  of 
atmospheric  air  introduced.     To  heat  them  to  1000°  there  will  be  required : 
200  x  0*31  x  1000  =  62000  heat-units. 

The  100  kilos,  magnesia  :   too  x  0*244  x  1000  =  24400  heat-units. 

The  chlorine  35*5  x  0-12  x  1000  =  4260  heat-units. 

The  HC1 :  36-5  x  0-19  x  1000  =  6935  heat-units. 

The  water  :  36  [620  +  (900-0-48)]  =  37*872  heat-units. 

For  the  evolution  of  35-5  kilos,  chlorine  from  magnesium  chloride,  there  are  re- 
quired 3500,  and  for  hydrochloric  acid  10,000  heat-units.  Hence  results  the  following 
distribution  of  heat  for  each  35-5  kilos,  of  chlorine  : 

Chemical  work    .       .  .    .    .         .         .     13-500  heat-units. 

Heating  air         .         .        .        .         .     62*000  „ 

Magnesia 24*400  „ 

Watery  vapour 37 '900  „ 

Chlorine  and  hydrochloric  acid  .         .11  '200  „ 


149-000  „ 

In  addition  come  the  losses  of  conduction  and  radiation  from  the  masonry.  As  nearly 
half  the  consumption  of  heat  goes  to  heating  the  air,  the  regulation  of  the  access  of  air 
is  very  important.  It  may  be  recommended  to  warm  the  air  before  its  admission  by 
means  of  the  gases  escaping,  on  the  same  principle  as  in  the  hot  blast  in  iron-smelting. 
At  the  same  time,  the  refrigerating  apparatus  would  be  relieved  which  has  now  to  over- 
come 62,000  +  37,900  +  1 1,200  =11 1,100  heat-units. 
In  working  up  calcium  chloride,  there  result — 

CaClz  +  O  =  CaO  +  01, 

— 170,230    +     131,360     =     38,870  heat-units,  and 
CaCl2     +     H2O       =      CaO      +      2HC1 

—  170,230  —  57,000     +  131,360  -r  44,000  =  —  51,870  heat-units. 
Hence,  as  regards  the  heat  needed  for  its  decomposition,  calcium  chloride  is  less 
advantageous  than  magnesium  chloride. 

In  obtaining  hydrochloric  acid  from  sodium  chloride  and  sulphuric  acid,  there  is  first 
formed  bisulphate : 

NaCl  +  H2S04     =     NaHSO4    +    HOI 

—  97,700  -   192,900  +     267,800      +    22,000  =    -  800  heat-units. 

The  demand  for  heat  is  therefore  almost  nil.     In  the  formation  of  monosulphate  : 
2NaCl  +  H2S04     =   Na2S04    +    2HC1 

—  195,400  -   192,900  +  328,500  +  44,000  =  -   15,800  heat-units. 
Hence  the  mixture  must  be  heated  to  complete  the  reaction,  as  experience  shows. 
To  calculate  the  heat  required  by  a  salt-cake  furnace,  let  us  suppose  that  the  98- 

kilos.  sulphuric  acid  required  to  decompose  117  kilos,  sodium  chloride  contain  30  kilos, 
of  water,  and  that  the  hydrochloric  acid  escapes  as  a  mean  at  400°,  the  watery  vapour 
at  500°,  whilst  the  sulphate  is  heated  to  600°. 

If  the  specific  heat  of  the  salt-cake  is  assumed  at  0*232,  there  are  required  to  heat 
the  142  kilos,  of  salt-cake  142  x  0-232  x  600=  19,766  heat-units.  The  specific  heat  of 
hydrochloric  acid  is,  on  the  average,  0-19,  therefore  73  x  0-19  x  400  =  5,548  heat-units. 
To  convert  water  of  17°  into  steam  at  500°  there  are  required  812  heat-units — i.e.,  for 
30  kilos.  24,360  heat-units. 

If  we  consider  the  draught  of  the  chimney,  &c.,  there  may  be  reckoned  in  round 
numbers  500  heat-units  for  the  work  performed  by  the  hydrochloric  acid  generated. 


SECT,  m.]  THERMOCHEMISTRY.  485 

Hence — 

Heating  sulphate 19,766  heat-units. 

„        hydrochloric  acid 5,54$  ,, 

„        watery  vapour 24,360  „ 

Chemical  work 15,800  „ 

Mechanical  work 500  „ 


Together  about 66,000  „ 

In  the  condensation  of  the  hydrochloric  acid,  there  have  to  be  removed  by  refri- 
geration : 

Watery  vapour 24,360  heat- units. 

HC1  specific  heat 5,548  ,, 

HC1  solution  heat 15,000  ,, 


45,000  „ 

It  is  here  supposed  that  the  watery  vapour  is  condensed,  but  not  the  fire-gases. 

These  figures  merely  show  in  what  manner  such  calculations  may  be  conducted  on 
analytical  data. 

In  accordance  with  the  easy  execution  of  the  oxidation  of  Weldon  mud,  it  is  con- 
ducted with  a  development  of  heat,  as  the  formation  of  the  manganous  hydrate  yields 
94,770,  and  that  of  the  hydrated  peroxide  116,2  80  heat-units. 

The  decomposition  of  the  latter  with  strong  hydrochloric  acid  gives — 
Mn03H2  +  4H01.aq.  =  MnCl2.aq.  +  01,     +  3H3O 

—  116,300  —  148,000      +    128,000  +     205,200  =  68,900  heat-units. 

As  soon  as  the  mixture  is  raised  to  the  temperature  of  the  reaction  the  liberation  of 
Cl  goes  on  readily. 

The  thermic  relations  of  the  manufacture  of  chloride  of  lime  have  not  been  deter- 
mined, though   it  is  known  that  in  the  formation  of   potassium  hypochlorite  in  an 
aqueous  solution  24,600  heat- units  are  liberated  according  to  the  reaction 
2KOH.aq.  +  01,  =  KCl.aq.  +  KOCLaq. 

In  the  formation  of  potassium  chlorate  in  an  aqueous  solution  there  are  liberated  : 

6KOH.aq.  +  3Cl2.aq.  =  sKCl.aq.  +  KC103.aq. 

that  is,  97,900  heat-units,  a  renewed  proof  that  the  reactions  which  give  most  heat  are 
not  always  most  easy  to  conduct. 

The  following  works  may  be  consulted  : — J.  Thomsen,  Thermochem.  Untersvxhungen 
{Leipzig,  1882  to  1888).  Berthelot,  Essai  de  mecanique  chimique  (Paris,  Dunod,  1879). 
Al.  Naumann,  Handbuch  der  Thermochemie  (Brunswick,  1882).  Horstmann,  Theoretische 
Chemie.  W.  Ostwald,  Verwatidtschafts  Lehre  (Leipzig,  1887). 


SECTION    IV. 
THE    ORGANIC   CHEMICAL   MANUFACTURES. 


ALCOHOLS  AND  ETHERS. 

Methylic  AlcoJwL — CH3.OH,  a  liquid  boiling  at  65-5°  to  66°,  is  formed  on  the  dry 

distillation  of  wood.     Leaf-bearing  trees  yield  it  in  larger  proportion  than  the  conifers. 

For  the  distillation  there  are  commonly  used  horizontal  iron  retorts,  heated  in  the 

same  manner  as  gas  retorts,  though  in  general  not  above  500°.     Occasionally,  large 

upright     retorts    are 

Fig.  377.  used,    or,   in   France, 

cylinders  of  sheet-iron 
(Fig-  377)-  Such  a 
cylinder,  A,  has  in  its 
upper  half  an  opening 
o,  to  which  a  connect- 
ing-piece is  screwed 
on.  Upon  the  cylin- 
der is  laid  the  cover, 
which  is  screwed  fast 
as  soon  as  the  cylinder 
has  been  filled  with 
wood.  The  cylinder 
itself  is  lowered  by 
means  of  the  crane, 
D,  into  a  cylindrical 
furnace,  £,  closed 
above  with  the  stone 
cover,  E.  The  pro- 
ducts given  off  on  the  application  of  heat  pass  through  the  pipe,  b  (Fig.  378),which  is  con- 
nected with  the  cylinder  and  bent  in  a  zigzag  manner,  through  the  refrigerating  appa- 
ratus c,  set  in  the  support  d,  to  which  cold  water  is  conveyed  through  /,  whilst  the 
heated  water  escapes  at  k.  Acetic  acid,  tar,  and  wood-spirit  are  liquified,  and  flow 
into  the  vat  #,  in  which  the  tar  is  chiefly  deposited.  The  lighter  liquids  run  through 
m  to  the  second  vat,  h.  The  combustible  gases  escape  through  the  pipe  i,  into  the 
open  air,  or  into  the  furnace,  though  their  value  as  fuel  is  but  small.  In  large  works 
there  are  used,  instead  of  the  wooden  vats,  cisterns  of  cement  or  masonry  sunk  into  the 
ground,  each  being  connected  with  the  next  following  by  a  pipe  at  its  upper  end.  The 
bulk  of  the  tar  collects  in  the  first  cistern,  whilst  the  wood-vinegar,  freed  from  the  tar, 
which  is  merely  mechanically  suspended,  flows  into  the  last  cistern.  Wood-gas  works, 
of  course,  produce  wood-vinegar  as  a  bye-product. 

The  watery  liquid  separated  from  the  tar  contains  methylic  alcohol,  acetone,  acetic 
acid,  &c.,  and  is  distilled.     Crude  wood-spirit  first  passes  over  and  then  acetic  acid,  which 


SECT.   IV.] 


ALCOHOLS  AND   ETHERS. 


487 


The  wood-spirit  is  purified  by  rectification  in  the  column 


is  neutralised  with  lime, 
apparatus. 

In  order  to  remove  the  last  portion  of  acetone,  the  purified  wood-spirit  is  treated 
with  chlorine  and  rectified  again.     Oak- 
wood  yields  on  distillation  i  per  cent,  of 
wood-spirit. 

The  proportion  of  methyl  alcohol  in 
commercial  wood-spirit  is  ascertained  by 
converting  it  into  methyl  iodide  by  phos- 
phorus di-iodide  (PI2) ;  5  c.c.  of  absolute 
methyl  alcohol  yield  7*19  c.c.  methyl  iodide. 

Uses. — Crude  wood-spirit  is  used  for 
denaturising  spirits ;  pure  methyl  alcohol 
is  used  in  the  manufacture  of  coal-tar 
colours  and  in  ice-machines,  after  con- 
version into  ether. 

Ethyl  Alcohol  (ordinary  alcohol), 
C2H5.OH.  The  production  of  alcohol  by 
fermentation  will  be  described  below.  It 
is  obtained  in  the  anhydrous  state  by 
distillation  over  quicklime.  Pure  alcohol 
boils  at  78°. 

The  determination  of  the  percentage  composition  of  samples  of  alcohol  is  effected 
by  means  of  the  sp.  gr.  For  technical  purposes  hydrometers  are  used.  Hitherto  the 
hydrometers  or  areometers  of  Tralles  and  Richter  have  been  most  in  use.  That  of 
Stoppani  agrees  with  the  latter.  Both  are  percentage  hydrometers — i.e.,  they  show 
by  the  number  down  to  which  they  sink  how  much  pure  alcohol  is  contained  in  the 
liquid  in  question.  The  difference  between  the  two  instruments  is  that  the  hydro- 
meter of  Tralles  indicates  percentages  by  volume,  and  that  of  Richter  percentages  by 
weight.  As  the  graduation  of  the  Richter  hydrometer  proceeds  from  inaccurate 
assumptions  that  of  Tralles  is  to  be  preferred.*  The  hydrometer  of  Tralles  has  been 
until  quite  lately  the  legally  recognised  instrument  in  Germany  for  determining  per- 
centages of  alcohol,  though  one  which  gives  percentages  by  weight  has  now  been  intro- 
duced in  its  place. 

Spirits  intended  for  technical  purposes  are  exempted  from  duty  if  they  are  dena- 
turised  by  any  one  of  a  variety  of  methods  which  the  manufacturer  may  select.  The 
most  suitable  of  all  these  agents  is  "  Dippel's  animal  oil."  The  alcohol  tables  of 
O.  Hehner,  which  give  the  proportion  of  alcohol  for  different  sp.  gr.  at  15 '5°,  are  here 
given  as  far  as  they  are  important  in  analysis  and  the  arts. 


In  England  the  hydrometer  of  Sykes  is  in  official  use. 


488 


CHEMICAL  TECHNOLOGY. 


[SECT.  rv. 


Specific  Gravity 
=  15-5° 

Absolute  Alcohol. 

Specific  Gravity 
=  i5*5°- 

Absolute  Alcohol. 

Specific  Gravity 
=  15-5°- 

Absolute  AlcohoL 

Weight. 

Volume. 

Weight. 

Volume. 

Weight. 

Volume. 

Per  Cent 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent 

I-OOOO 

O'OO 

O'OO 

0-9878 

7-40 

9'2I 

0-9758 

I6-62 

20-43 

0-9998 

o-n 

0-13 

6 

7'53 

9-37 

6 

1677 

20  '6  1 

6 

O'2I 

0.26 

4 

7-67 

9'54 

4 

16-92 

20  '80 

4 

0-32 

0-40 

2 

7'8o 

9-70 

2 

17-08 

20-99 

2 

O'42 

0'S3 

0 

7'93 

9-86 

O 

17-25 

21-19 

0 

o-53 

0-66 

0-9988 

0-63 

079 

0-9868 

6 

8-07 
8-21 

10-03 
10-21 

0-9748 

6 

17-42 
17-58 

21-39 
21-59 

6 
4 

074 
0-84 

0-93 
I  -06 

4 

2 

8-36 
8-50 

IO-38 
10-56 

4      - 

2 

1775 
17-92 

21-79 
21-99 

2 
0 

°'95 
i  -06 

1-19 

i'34 

O 

8-64 

1073 

O 

18-08  i 

22-18 

0-9978 

rig 

1-49 

0-9858 

879 

IO-9I 

0-9738 

18-23 

22-36 

6 

1-31 

l-65 

6 

8-93 

II  -08 

6 

18-38 

22-55 

4 

1-44 

1-81 

4 

9-07 

11-26 

4 

18-54 

2273 

2 

1-56 

1-96 

2 

9-21 

11-44 

2 

18-69 

22-92 

0 

1-69 

2-12 

0 

9-36 

11-61 

O 

18-85 

23-10 

O.9968 

1-81 

2'27 

0-9848 

9*50 

1179 

0-9728 

19-00 

23-28 

6 

1-94 

2'43 

6 

9-64 

11*96 

6 

19-17 

23-48 

4 

2-06 

2-58 

4 

979 

12-13 

4 

I9-33 

23-68 

2 

2-17 

272 

2 

9-93 

12-31 

2 

19-50 

23-88 

O 

2-28 

2-86 

0 

10-08 

12-49 

O 

19-67 

24-08 

0-9958 

2-39 

3-00 

0-9838 

10-23 

12-68 

0-9718 

19-83 

24-28 

6 

2-50 

3-I4 

6 

10-38 

12-87 

6 

20  -oo 

24-48 

4 

2'6l 

3-28 

4 

10-54 

13-05 

4 

20-17 

24-68 

2 

272 

3  '42 

2 

10.69 

13-24 

2 

20-33 

24-88 

O 

2-83 

3'5S 

O 

10-85 

»3'43 

O 

20-50 

25-07 

0-9948 

2-94 

3-69 

0-9828 

II'OO 

13-62 

0-9708 

20-67 

25-27 

6 

3-06 

3-83 

6 

11-15 

13-81 

6 

20-83 

25-47 

4 

3-i8 

3-98 

4 

11-31 

I3-99 

4 

21*00 

25-67 

2 

3-29 

4-12 

2 

11-46 

14-18 

2 

21*15 

25-86 

O 

3  '4i 

4-27 

O 

11-62 

1437 

O 

21-31 

26-04 

0-9938 

3'53 

4-42 

0-9818 

1177 

14-56 

0-9698 

21-46 

26-22 

6 

3-65 

4'56 

6 

11-92 

I4-74 

6 

21-62 

26-40 

4 

376 

47i 

4 

12-08 

I4-93 

4 

2177 

26-58 

2 

3'88 

4-85 

2 

12-23 

15-12 

2 

21-92 

26-77 

0 

4'OO 

S'oo 

O 

12-38 

15-30 

O 

22-08 

26-95 

O-9928 

4-12 

5-i6 

0-9808 

12-54 

15-49 

0-9688 

22-23 

27-I3 

6 

4-25 

5-32 

6 

12-69 

15-68 

6 

22-38 

27-31 

4 

4'37 

5  '47 

4 

12-85 

15-86 

4 

22-54 

27-49 

2 

4-50 

5-63 

2 

13-00 

16-05 

2 

22-69 

27-68 

O 

4-62 

578 

O 

I3'i5 

16-24 

O 

22-85 

27-86 

0-9918 

475 

5  "94 

0-9798 

13-31 

I6'43 

0-9678 

23-00 

28-04 

6 

4-87 

6-10 

6 

13-46 

16-61 

6 

23-15 

28-22 

4 

5-00 

6-24 

4 

13-62 

16-80 

4 

23-31 

28-41 

2 

5'i2 

6-40 

2 

1377 

16-98 

2 

23-46 

28-59 

O 

5-2S 

6'5S 

O 

13-92 

17-17 

O 

23-62 

2877 

0-9908 

5'37 

6-71 

0.9788 

14-09 

1737 

0-9668 

2377 

28*95 

6 

5-|o 

6-86 

6 

14-27 

I7-59 

6 

23*92 

29*13 

4 

5-62 

7-01 

4 

HHS 

17-81 

4 

24-08 

29*31 

2 

575 

7-17 

2 

14-64 

18-03 

2 

24-23 

29-49 

0 

5-87 

7'32 

O 

14-82 

18-25 

O 

24-38 

29-67 

0-9898 

6-00 

7-48 

0-9778 

15-00 

18-48 

0-84I8 

82-62 

87-61 

6 

6-14 

7-66 

6 

I5-I7 

18-68 

6 

82-69 

87-67 

4 

6-28 

7-83 

4 

I5-33 

18-88 

4 

82-77 

8773 

2 

6'43 

8-01 

2 

I5-50 

19-08 

2 

82-85 

8779 

O 

6-57 

8-18 

O 

15-67 

19-28 

O 

82-92 

87-85 

0-9888 

671 

8-36 

0-9768 

15-83 

19-49 

0-8408 

83-00 

87-91 

6 

6-86 

8'54 

6 

16-00 

19-68 

6 

83-08 

87-97 

4 

7-00 

872 

4 

16-15 

19-87 

4 

83-15 

88-03 

2 

7-13 

8-88 

2 

16-31 

20  -06 

2 

83-23 

88-09 

O 

7-27 

9-04 

O 

16  46 

2O-24 

0 

83-31 

88-16 

SECT.   IV.] 


ALCOHOL. 


489 


Specific  Gravity 
=  15-5°. 

Absolute  Alcohol. 

pecific  Gravity 
=  15-5°. 

Absolute  Alcohol. 

pecific  Gravity 
=  iS'S0. 

Absolute  Alcohol. 

Weight.  \ 

Volume. 

Weight. 

Volume. 

Weight. 

Volume. 

Per  Cent.1 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

0-8398 

83-38 

88-22 

0-8278 

88-04 

91-81 

0-8158 

92-52 

95-08 

6 

83-46 

88-28 

6 

88-12 

91-87 

6 

92-59 

95-13 

4 

83-54 

88-34 

4 

88-20 

9I-93 

4 

92-67 

95-I9 

2 

83-62 

88-40 

2 

88-28 

91-99 

2 

92-74 

95-24 

O 

83-69 

88-46 

0 

88-36 

92-05 

0 

92-81 

95-29 

0-8388 

8377 

88-52 

0-8268 

88-44 

92-12 

0-8148 

92-89 

9",°35 

6 

83-85 

88-58 

6 

88-52 

02-lS 

6 

92-96 

9  "40 

4 

83-92 

88-64 

4 

88-60 

92-24 

4 

93  -°4 

95-45 

2 

84-00 

88-70 

2 

88-68 

92-30 

2 

93-11 

95'SO 

0 

84-08 

8876 

0 

88-76 

92-36 

O 

93-18 

95-55 

0-8378 

84-16 

88-83 

0-8258 

88-84 

92-42 

0-8138 

93-26 

95-61 

6 

84-24 

88-89 

6 

88-92 

92-48 

6 

93-33 

95'66 

4 

84-32 

88-95 

4 

89-00 

92-54 

4 

93HI 

9571 

2 

84-40 

89-01 

2 

89-08 

92-60 

2 

93H8 

95-76 

O 

84-48 

89-08 

O 

89-16 

92-66 

O 

93-55 

95-82 

0-8368 

84-56 

89-14 

0-8248 

89-23 

9271 

0-8I28 

93-63 

95-87 

6 

84-64 

89-20 

6 

89-31 

9277 

6 

9370 

95'92 

4 

84-72 

89-27 

4 

89-38 

92-83 

4 

93-78 

95^7 

2 

84^80 

89-33 

2 

89-46 

92-89 

2 

93-85 

96-03 

0 

84-88 

89-39 

0 

89-54 

92-94 

O 

93-92 

96-08 

0-8358 

84-96 

89-46 

0-8238 

89-62 

93-00 

0-8118 

94-00 

96-13 

6 

85-04 

89-52 

6 

89-69 

93-06 

6 

94-07 

96-18 

4 

85-12 

89-58 

4 

8977 

93-11 

4 

94-14 

96-22 

2 

85-I9 

89-64 

2 

89-85 

93-I7 

2 

94-21 

96-27 

0 

85-27 

8970 

O 

89-92 

93-23 

O 

94-28 

96-32 

0-8348 

85-35 

89-75 

0-8228 

90-00 

93-29 

0-8108 

94'34 

96-36 

6 

85-42 

89-81 

6 

90-07 

93-34 

6 

94-4I 

96-41 

4 

85-50 

89-87 

4 

90-14 

9339 

4 

94-48 

96-46 

2 

85-58 

89-93 

2 

90-21 

93-44 

2 

94-55 

96-50 

O 

85-65 

86-99 

O 

90-29 

93*49 

O 

94-62 

96-55 

0-8338 

85-73 

90-05 

0-82I8 

90-36 

93-54 

0-8098 

94-69 

96-60 

6 

85-81 

90-11 

6 

90-43 

93^9 

6 

94-76 

96-64 

4 

85-88 

90-17 

4 

90-50 

93^4 

4 

94-83 

96-69 

2 

85-96 

90-23 

2 

90-57 

9370 

2 

9490 

96-74 

O 

86-04 

90-29 

O 

90-64 

9375 

O 

94-97 

96-78 

0-8328 

86-12 

SO'35 

0-8208 

9071 

93-80 

0-8088 

95-04 

96-83 

6 

86-19 

90-40 

6 

90-79 

93-85 

6 

95.11 

96-88 

4 

86-27 

90-46 

4 

90-86 

93-90 

4 

95-18 

96-93 

2 

86-35 

90-52 

2 

90-93 

93-95 

2 

95-25 

96-98 

O 

86-42 

90-58 

O 

91-00 

94-00 

O 

95-32 

97-02 

0-83I8 

86-50 

90-64 

0-8I98 

91-07 

94-05 

0-8078 

95'39 

97-07 

6 

86-58 

90-70 

6 

91-14 

94-10 

6 

95'46 

97-12 

4 

86-65 

90-76 

4 

91-21 

94-I5 

4 

95-54 

97-17 

2 

8673 

90-82 

2 

91-29 

94-21 

2 

95-61 

97-22 

O 

86-81 

90-88 

O 

91-36 

94-26 

O 

95-68 

97-27 

0-8308 

86-88 

90-93 

0-8188 

91-43 

94-3I 

0-8068 

9575 

97*32 

6 

86-96 

90-99 

6 

91-50 

94-36 

6 

95-82 

97-37 

4 

87-04 

91-05 

4 

91-57 

94-41 

4 

95-89 

97-4 

2 

87-12 

91-11 

2 

91-64 

94-46 

2 

95-96 

97-46 

0 

87-19 

91-17 

O 

91-71 

94-5I 

0 

96-03 

97'5* 

0-8298 

87-27 

91-23 

0-8I78 

91-79 

94-56 

0-8058 

96-10 

97-55 

6 

8735 

91-28 

6 

91-86 

94-61 

6 

96-16 

97-60 

4 

87-42 

9I-34 

4 

9I-93 

94-66 

4 

96-23 

97-64 

2 

87-50 

91-40 

2 

92-00 

947i 

2 

96-30 

97-68 

O 

87-58 

91-46 

0 

92-07 

94-76 

O 

96-37 

9773 

0-8288 

87-65 

91-52 

0-8168 

92-15 

94-82 

0-8048 

96-43 

9777 

6 

8773 

9i'57 

6 

92-22 

94-87 

6 

96-50 

97-8i 

4 

87-81 

91-63 

4 

92-30 

94-92 

4 

96-57 

97-86 

2 

87-88 

91-69 

2 

92-37 

94-98 

2 

96-63 

97-90 

0 

8796 

9175 

O 

92-44 

95-03 

0 

96-70 

97-94 

49° 


CHEMICAL   TECHNOLOGY. 


[SECT.  iv. 


Specific  Gravity 
=  i5-5° 

Absolute  Alcohol. 

Specific  Gravity 
=  iS-50 

Absolute  Alcohol. 

Specific  Gravity 
=  iS-5°. 

Absolute  Alcohol. 

Weight. 

Volume. 

Weight. 

Volume. 

Weight. 

Volume. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cent. 

0-8038 

9676 

97-98 

0-8002 

97-96 

98-76 

0-7968 

99-03 

99'39 

6 

96-83 

98-03 

0 

98-03 

98-80 

6 

99-10 

99-43 

4 
2 

96*90 
96-96 

98-07 
98  II 

0-7998 

6 

98-09 
98-16 

98-83 
98-87 

4 

2 

99-16 
99-23 

99-47 
99-5I 

O 

97*03 

98-16 

4 

98-22 

98-91 

O 

99-29 

99-55 

0-8028 

97-10 

98-20 

2 

98-28 

98-94 

0.7958 

99-36 

99-59 

6 

97-16 

98-24 

0 

98-34 

98-98 

6 

99-42 

99-63 

4 

2 
0 

97-23 
97  '30 
97-37 

98-29 
98-33 
98-37 

0-7988 

6 
4 

98-41 
98-47 
98-53 

99-02 

99-05 
99-09 

4 

2 
O 

99-48 

99-55 
99-61 

99-67 
9971 
99-75 

0-8018 

97-43 

98-42 

2 

98-59 

99-I3 

0-7948 

99-68 

99-80 

6 

97-50 

98-46 

O 

98-66 

99-16 

6 

9974 

99-84 

4 

2 
O 

97-57 
97-63 
97-70 

98-50 
98-54 
98-59 

07978 

6 

4 

9872 
98-78 
98-84 

99-20 
99-24 
99-27 

4 

2 
0 

99-81 
99-87 
99-94 

99-88 
99-92 
99-96 

0-8008 

97-76 

98-63 

2 

98-91 

99-3I 

0-7938 

lOO'OO 

lOO'OO 

6 

97-83 

98-67 

O 

98-97 

99-35 

4 

97-90 

9871 

Chloroform,  CHC13,  a  colourless  liquid,  boiling  at  61°,  is  obtained  by  distilling 
alcohol  with  chloride  of  lime.  For  this  purpose  there  are  used  iron  vessels,  of  about 
i '4  metres  in  height  and  2  metres  in  diameter.  They  are  fitted  with  a  mechanical 
agitator,  a  pipe  for  introducing  steam  and  one  for  water,  and  a  manhole  for  filling  in 
the  chloride  of  lime.  At  the  upper  margin  of  the  generator  there  is  placed  a  per- 
forated lead  tube  (the  holes  towards  the  cylinder),  which  is  connected  with  the  water- 
supply.  A  pipe  of  75  mm.  inside  diameter,  with  a  strong  decline,  leads  to  the  con- 
denser. It  is  best  to  use  4  parts  chloride  of  lime  of  103°  to  108°  (higher  and 
lower  qualities  are  less  suitable),  3  parts  alcohol  at  96°  Tralles  in  13  parts  of  water, 
so  that  we  have  16  parts  of  liquid  to  4  parts  of  solid  matter.  For  a  daily  output  of 
115  kilos,  of  chloroform,  each  of  the  four  generators  must  have  a  charge  of  400  kilos. 
chloride  of  lime,  300  kilos,  alcohol,  and  1300  kilos,  of  water.  The  alcohol  is  first  in- 
troduced, then  water  enough  to  make  up  1600  litres  of  liquid,  next  the  agitator  is  set 
in  action,  and  the  400  kilos,  of  chloride  of  lime  are  added.  The  apparatus  is  then 
closed  air-tight,  and  the  mixture  is  heated  by  means  of  steam.  As  soon  as  the  ther- 
mometer reaches  40°  the  steam  is  shut  off.  The  agitator  is  worked  until  the  thermometer 
reaches  45°,  when  it  is  disconnected.  The  temperature  still  rises  slowly,  and  the  re- 
action reaches  its  height  at  about  60°.  In  very  hot  weather  the  temperature  rises 
much  higher,  and  in  that  case  cold  water  is  let  flow  over  the  apparatus.  Between  the 
receiver  and  the  refrigerator  there  is  a  glass-tube  introduced  in  the  connecting-pipe. 
As  soon  as  the  reaction  is  in  progress,  a  fine  rain  of  chloroform,  alcohol,  and  water  is 
seen  to  drive  through  this  tube.  As  the  air  which  issues  from  the  apparatus  is 
saturated  with  the  vapour  of  chloroform,  it  is  caused,  before  escaping,  to  pass  through 
a  washing  bottle  filled  with  water.  This  violent  "  blowing"  lasts  about  a  minute,  when 
the  chloroform  begins  to  flow.  As  soon  as  about  30  kilos,  have  been  distilled  off  from 
each  apparatus  the  agitator  is  again  set  in  motion.  When  the  chloroform  no  longer 
separates  as  a  heavy  layer  in  the  distillate,  the  tin  vessels  which  serve  as  receivers  are 
charged.  The  distillate  which  next  follows  consists  of  alcohol  saturated  with  chloro- 
form, and  it  is  collected  as  long  as  chloroform  separates  out  after  shaking  with  water. 
As  soon  as  the  distillate  becomes  clear  after  shaking,  the  efflux  cocks  are  closed,  and 
the  distillate  runs  into  the  pressure-vessels.  The  agitator  is  kept  in  motion  to  prevent 
the  solid  matter  from  settling,  and  the  distillation  is  kept  up  until  the  distillate  marks 
only  3°  Tralles.  The  lime  liquor  is  then  let  off  through  a  hole  near  the  bottom.  In 


SECT,  iv.]  ORGANIC  ACIDS.  491 

each  pressure-vessel  there  are  now  contained  500-600  litres  of  very  dilute  alcohol. 
Before  a  new  operation  is  commenced,  it  is  calculated  accurately  how  much  alcohol  is 
present  and  how  much  liquid.  If  there  are  between  270  and  300  kilos,  of  alcohol  in  the 
pressure-vessel  it  is  only  made  up  to  300  kilos.  The  quantity  of  liquid  still  required 
is  calculated  and  run  into  the  generator,  whilst  the  chloride  of  lime  is  stirred  up. 
When  this  has  been  done  the  generators  are  closed  air-tight,  and  the  contents  of  the 
pressure-vessels  are  forced  into  them.  The  turbid  alcoholic  chloroform  which  distils 
over  first  on  washing  after  rectification  is  collected  separately  and  washed  again. 

According  to  Giinther,  the  carbonic  acid  formed  from  the  oxidation  of  the  alcohol 
initiates  the  production  of  chloroform  by  setting  free  hypochlorous  acid : 

1.  CaO2012   4   C02  +  H0O   -=   2HOC1    +   CaCO3. 

2.  C,H60   +  HOC1  =  C2H40   4   HC1  +  H20. 

3.  HC1  +   HOC1  =   2C1   +   H2O. 

4.  C,H40  4   6C1   =   CC13COH    4    3HC1. 

5.  CC13COH    +   Ca02H2  =   2CHC13  +  Ca(HCOO)2. 

In  the  production  of  iodoform,  CHI3,  the  same  author  recommends  mixing  alcohol 
containing  20  to  25  parts  of  aldehyde  with  10  parts  solution  of  soda  and  then  to  intro- 
duce iodine.  The  mixture  is  allowed  to  stand  at  the  common  temperature  with  occa- 
sional stirring  until  the  separation  of  iodoform  has  begun ;  perhaps  it  is  advantageous 
to  add  here  a  little  sodium  iodide  at  the  outset.  The  formation  of  iodoform  is 
explained  by  the  following  formulae  : — 

1.  Na2COg  +  2I+  H2O  =  HOI  4  Nal  +  NaHC03. 

2.  C,H60  +  HOI  =  C2H4O  +  HI  +  H20. 

3.  HI  +  HOI  =  2!  +  H3O. 

4.  C3H40  +  61  +  3HOI  =  CI3(COH)  +  61  4-  3H,0. 

5.  CIS(COH)  4  NaHC03  =  CHI3  4  NaHCOO  4  C02. 

Chloral  hydrate,  C2HC13O.H2O,  is  obtained  by  passing  chlorine  into  alcohol.  If 
heated  with  potassa-lye  it  yields  pure  chloroform : 

C2HC130  4  KOH  =  CHC13  4  KCH02. 

Ether  (C2H.O)  boils  at  35'5°.  It  is  obtained  by  distilling  alcohol  with  sulphuric  acid  : 
C2H5OH      4  H2S04       =  C2H5.HS04  4  H20,  and 
C,HSHS04  4  C2H5OH   =  (C2H.)2O       4  H2SO4. 

As  the  sulphuric  acid  is  constantly  re-constituted,  whilst  ether  and  water  distil  off, 
alcohol  is  let  constantly  flow  in  as  fast  as  it  is  decomposed. 

ORGANIC  ACIDS. 

Among  the  organic  acids  which  are  not  obtained  from  tar  the  following  are 
technically  the  most  important. 

Acetic  Acid. — H.C2H3O2  is  formed  by  the  oxidation  of  ethyl-alcohol  by  atmospheric 
oxygen.  Aldehyde  is  first  formed,  and  on  taking  up  one  atom  oxygen  it  becomes  acetic 
acid — 

C3H6O  4  O  =  C2H40  4  H2O;  C2H4O  4  O  =  C2H4O,;  or 

CH3.CH2OH  4  Oa  =  CH3.COOH  4  H2O. 

46  kilos,  ethyl-alcohol  consequently  require  32  kilos,  or  22*3  cubic  metres  of  oxygen 
(  =  107  cubic  metres  of  atmospheric  air)  in  order  to  yield  60  kilos,  of  pure  acetic  acid 

The  following  kinds  of  vinegar  are  distinguished  by  their  origin  : — 

1.  Wine  vinegar,  containing  in  addition  to  acetic  acid,  almost  all  the  constituents 
of  wine — e.g.,  tartaric  acid,  succinic  acid,  glycerine,  and  certain  others  which  give  it  an 
agreeable  aroma. 

2.  Spirit  vinegar,  which  generally  consists  of  a  mixture  of  acetic  acid  and  water 
with  small  quantities  of  aldehyde  and  acetic  ether. 


492  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

3.  Fruit  vinegars,  obtained  from  cyder  and  perry  or  direct  from  apples,  contain, 
along  with  acetic  acid,  malic  acid  (and  have  the  aroma  of  ripe  apples). 

4.  Beer,  malt,  or  grain  vinegar,  made  from  unhopped  beer- worts  (or  sometimes, 
under  the  name  of  alegar,  from  spoiled  beer).     It  contains,  along  with  acetic  acid  and 
small  quantities  of  aldehyde,  extractive  matter,  phosphates,  nitrogenous  matter  and 
dextrine  (which  may  be  the  cause  of  its  want  of  aroma). 

5.  Sugar  vinegar,  made  from  solutions  of  cane-sugar  or  cane-treacle.     It  is  probable 
that  with  the  addition  of  the  proper  vinous  ferments  a  true  wine  vinegar  might  be 
obtained  from  this  source.     Vinegar  is  also  made  from  sugar-beets. 

6.  Vinegar  is  also  obtained  from  pyroligneous  acid,  after  elimination  of  the  tarry 
matters,  and  acetose. 

The  Older  Method  of  Vinegar  Making. — As  regards  the  so-called  old  method  of 
vinegar  making  it  is  without  doubt  an  imitation  of  the  spontaneous  souring  of  beer, 
wine,  and  fermented  liquors  generally,  and  under  conditions  which  are  conducive  to  the 
improvement  of  the  product ;  such  conditions  are — a  suitable  temperature,  intimate 
contact  of  the  souring  liquor  with  air,  and  a  so-called  acetification  inducing  ferment. 
This  method  is  very  generally  employed  for  making  wine  vinegar — French  vinegar  as  it 
is  termed  in  England — but  may  of  course  be  used  for  malt  or  fruit  vinegar  making  as 
well.  Generally  a  '"  souring  "  vessel  or  "  mother  "  vessel  made  of  oak  wood  is  employed ; 
this  vat  is  first,  when  newly  made,  thoroughly  scalded  with  boiling  water,  and  when 
thereby  the  extractive  matter  of  the  wood  is  exhausted  the  vessel  is  filled  with  boiling 
vinegar ;  when  the  wood  is  soaked  with  vinegar  there  is  poured  into  the  vessel  one 
hectolitre  of  wine,  and  after  eight  days  again  10  litres  of  wine  are  added,  and  this 
operation  continued  weekly  until  the  vessel  is  filled  for  two-thirds  of  its  cubic  capacity. 
About  fourteen  days  after  the  last  addition  of  the  wine  the  whole  of  the  contents  will 
have  become  converted  into  vinegar.  Half  this  quantity  is  withdrawn  from  the  souring 
vessel  and  carried  to  the  store ;  to  the  remainder  more  wine  is  added,  and  the  prepar- 
ation of  vinegar  proceeded  with  uninterruptedly  by  the  operation  described.  A 
souring  vessel  may  continue  to  serve  its  purpose  for  six  years,  and  often  longer,  but 
generally  at  the  end  of  this  time  there  is  collected  in  the  vessel  so  large  a  quantity  of 
yeast  sediment,  argol,  stone,  and  other  matter,  as  to  render  the  thorough  cleansing  of 
the  vessel  necessary ;  after  this  operation  it  is  again  fit  for  further  use.  Although  it 
might  appear  that  in  this  process  of  acetification  there  is  no  great  contact  of  air,  and 
the  fluid  is  apparently  quite  at  rest,  there  is  a  constant  change  of  the  particles  of  the 
surface  of  the  fluid,  owing  to  the  fact  that  every  drop  of  vinegar  formed  sinks  to 
the  bottom  of  the  vessel,  or  at  least  below  the  surface,  owing  to  its  increased  specific 
gravity ;  while  as  regards  the  air,  that  portion  of  it  from  which  the  oxygen  has  been 
absorbed  by  becoming  specifically  lighter  (0.9  sp.  gr.)  has  a  tendency  to  rise  upwards, 
and  to  be  replaced  by  heavier  air  (ro  sp.  gr.) ;  thus  a  constant  circulation  of  air  is 
provided. 

Quick  Vinegar  Making. — The  so-called  quick  vinegar  process,  founded  on  an  older 
method  of  vinegar  preparation  suggested  by  Boerhaave  in  1720,  was  first  introduced 
by  Schutzenbach  in  1823.  The  chief  principle  of  this  method  consists  in  causing  the 
fluid,  generally  brandy,  to  be  converted  into  vinegar  by  ultimate  contact  with  the 
atmosphere  at  the  requisite  temperature ;  or,  in  other  words,  the  oxidation  of  the  alcohol 
to  acetic  acid  is  effected  in  the  shortest  time  and  with  the  least  possible  loss.  The 
intimate  contact  of  the  fluid  with  the  air  is  effected  by  :• — i.  Increasing  the  quantity  of 
air  admitted  by  means  of  a  continual  current  of  air,  made  to  meet  the  drops  of  the 
fluid  intended  to  be  converted  into  vinegar,  in  the  opposite  direction  to  that  in  which 
these  drops  fall  downwards.  2.  By  causing  the  liquid  to  be  operated  upon  to  trickle 
down  drop  by  drop.  A  peculiarly  constructed  vessel  is  required  for  this  operation ; 
according  to  the  strength  of  vinegar  desired  to  be  made  two  or  four  of  these  vessels 


SECT.   IV.J 


ORGANIC  ACIDS. 


493 


Fig.  379- 


are  employed,  these  constituting  a  group,  or  battery  as  it  is  termed.  A  sectional  view 
of  such  a  vessel  is  exhibited  in  Fig.  379  ;  it  is  made  of  stout  oaken  staves,  the  vat  being 
from  2  to  4  metres  in  height,  and  from  i  to  1*3  in 
width ;  at  a  height  of  from  20  to  30  centimetres 
from  the  bottom  of  the  vessel  are  bored,  at  equal 
distances  from  each  other,  six  holes — air-holes — of 
about  3  centimetres  in  diameter,  so  cut  that  the 
inner  mouth  of  the  hole  is  situated  a  little  deeper 
than  the  outer ;  that  is  to  say,  the  holes  are  bored 
towards  the  bottom  in  a  slightly  sloping  direction. 
About  one-third  of  a  metre  above  the  real  lower 
bottom  a  false  bottom  is  placed,  similar  in  con- 
struction to  a  sieve,  and  at  a  height  of  a  centi- 
metre above  the  air-holes ;  upon  the  false  bottom 
is  a  layer  of  beech-wood  shavings  extending  up- 
wards to  about  from  15  to  20  centimetres  below 
the  upper  edge  of  the  vat.  The  false  bottom  is 
sometimes  constructed  of  laths  of  wood,  forming  a 
kind  of  gridiron-like  network.  Before  their  appli- 
cation the  wood  shavings  are  thoroughly  washed 
with  hot  water  and  afterwards  dried.  The  tub 

is  then  nearly  filled  with  the  dry  wood  shavings,  which  are  next  "  soured."  For  this 
purpose  warm  vinegar  is  poured  over  them,  and  allowed  to  remain  in  contact  with  the 
wood  for  twenty-four  hours,  so  as  to  cause  the  acetic  acid  to  soak  into  the  wood.  At 
from  1 8  to  24  centimetres  below  the  upper  edge  of  the  vat  is  fixed  a  perforated  wooden 
disc,  the  holes  of  which  are  as  large  as  a  goose-quill,  and  are  bored  from  3  to  5  centi- 
metres apart  from  each  other.  In  order  that  the  liquid  intended  to  be  converted  into 
acetic  acid  may  trickle  slowly,  and  in  fine  spray  as  it  were,  over  the  wood  shavings 
or  thin  chips  of  wood,  through  the  holes,  strings  of  twine  or  loosely  spun  cotton  yarn 
are  passed  so  as  to  penetrate  downwards  for  a  length  of  3  centimetres,  while  at  the 
top  a  knot  is  tied  which  prevents  the  strings  slipping  through  the  holes  ;  by  the  action 
of  the  liquid,  dilute  spirits  of  wine  usually,  which  is  poured  into  the  vessel,  the  twine 
becomes  more  or  less  swollen,  and  thereby  obstructs  the  passage  of  the  fluid  so  as  to 
divide  it  into  constantly  trickling  drops.  The  sieve  bottom  is  fitted  with  from  five  to 
eight  larger  holes,  each  about  3  to  6  centimetres  wide,  which  by  means  of  glass  tubes, 
each  of  from  10  to  15  centimetres  in  length,  inserted  and  firmly  fastened  therein,  act  as 
draught  tubes,  so  placed  that  no  liquid  can  pass  through  them.  The  vat  is  covered  at 
the  top  with  a  tightly-fitting  wooden  lid,  in  the  centre  of  which  a  circular  hole  is  cut, 
which  serves  as  well  for  the  purpose  of  pouring  the  liquid  into  the  vessel  as  for  the 
outlet  of  the  air  which  enters  the  vessel  from  below.  In  consequence  of  the  absorp- 
tion of  the  oxygen  so  much  heat  is  generated  in  the  interior  of  the  vessel  that  the  air 
streams  strongly  upwards,  causing  fresh  air  to  enter  by  the  lower  air-holes. 

After  the  vinegar  tub  has  been  soured  the  fluid  to  be  converted  into  vinegar — 
generally  brandy,  more  rarely  malt  liquor  or  wine — is  poured  in ;  the  fluid  flowing  off 
from  the  first  vessel  is  poured  into  the  second,  and  if  the  original  liquid  did  not  con- 
tain more  than  from  3  to  4  per  cent,  of  alcohol,  the  fluid  which  runs  off  from  the  second 
vessel  will  be  completely  converted  into  good  vinegar.  The  vinegar  collects  between 
the  true  and  false  bottoms.  As  will  be  seen  from  the  woodcut  the  vinegar  cannot  flow 
out  until  its  level  is  equal  to  that  of  the  mouth  of  the  glass  tube.  In  consequence  of 
this  arrangement  a  layer  of  about  1 6  to  20  centimetres  in  depth  of  warm  vinegar  assists 
in  the  acetification  by  the  evolution  of  acid  vapours  which  ascends  into  the  fluid  above. 
The  tube  must  dip  into  the  lower  part  of  the  fluid  in  the  interior  of  the  tub,  as  it  is 


494 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


Fig.  380. 


there  that  the  specifically  heavier  vinegar  collects.  The  arrangement  will  be  readily 
understood  from  Fig.  380 ;  c  p  is  the  perforated  bottom,  just  below  which  is  situated 

the  wooden  tap  /z,  fastened  to  the  bent 
glass  tube,  m  m,  the  free  open .  end  of 
which  touches  the  bottom  of  the  tub. 

Recently  (1868)  Singer's  vinegar 
generator  has  been  introduced.  It  con- 
sists of  a  number  of  vessels,  one  placed 
above  the  other,  and  so  connected  to- 
gether by  wooden  tubes  that  the  liquid 
intended  to  be  converted  into  vinegar 
trickles  drop  by  drop  from  the  one 
vessel  into  another  ;  in  each  tube  is  cut 
a  longitudinal  slit,  through  which  air 
freely  circulates ;  the  apparatus  is  placed 

in  a  suitably  constructed  shed,  wherein  a  convenient  temperature  is  kept  up  and  from 
which  draught  is  excluded.  By  means  of  this  apparatus  the  loss  of  alcohol  experienced 
in  the  use  of  the  vats  above  mentioned  is  prevented.  Singer's  apparatus  is  fully  de- 
scribed in  the  Jahresbericht  der  Chem.  Technologic,  1868,  p.  580. 

The  composition  of  the  fluid  to  be  acetified  varies  very  much ;  one  of  the  mixtures 
very  generally  used  is  made  up  of  20  litres  of  brandy  of  50  per  cent.  Tralles,  40 
litres  of  vinegar,  and  120  litres  of  water,  to  which  is  first  added  a  liquid,  made  by 
soaking  a  mixture  of  bran  and  rye  meal  in  water  in  order  to  promote  the  formation  of 
the  vinegar  fungus  (Mycoderma  aceti).  The  room  in  which  the  vats  are  placed  should 
be  heated  to  20°  to  24° ;  the  temperature  in  the  vats  rises  to  36°  and  more  ;  consequently 
the  alcohol,  aldehyde,  and  acetic  acid  are  volatilised,  and  this  loss  may  amount  to  about 
one-tenth.  Taking  this  loss  into  account  we  may  assume  that  i  hectolitre  of  brandy  at 
50  per  cent.  Tralles  ( =  42  per  cent,  according  to  weight)  yields  by  weight— 

13-0  hectolitres  of  vinegar  of  3  per  cent,  acetic  acid. 
9-9  4 


7-9 
6-6 
5-6 
4'9 
4 '4 
3'9 


9 
10 


When  required  for  transport  it  is,  of  course,  most  advantageous  to  prepare  very 
strong  vinegar  which  (at  the  place  where  it  is  to  be  consumed)  can  be  diluted  with  the 
requisite  quantity  of  water. 

In  this  process  it  is  very  essential  that  the  shavings  should  be  uniformly  moistened. 
Rose  therefore  omits  the  strings,  and  places  over  the  bottom  a  rocking^trough,  which 
pours  out  the  liquid  alternately  on  each  side  of  the  false  bottom.  The  distribution  may 
be  better  effected  by  means  of  Segner's  wheel. 

In  the  process  of  Michaelis  acetification  is  effected  in  rotating  tubs. 

Pasteur  has  referred  the  formation  of  vinegar  from  alcohol  to  the  action  of  bacteria, 
and  in  1862  described  a  physiological  process  for  the  manufacture.  A  fungus  (Myco- 
derma aceti}  is  the  agent.  This  fungus  is  first  propagated  in  a  fluid,  consisting  of  water  and 
2  per  cent,  of  alcohol  with  i  per  cent,  of  vinegar  and  a  small  quantity  of  potassium, calcium, 
and  magnesium  phosphate.  The  small  plant  soon  spreads  itself  over  the  entire  surface 
of  the  fluid,  without  leaving  the  smallest  space  uncovered.  At  the  same  time  the  alcohol 
is  acetified.  As  soon  as  half  the  alcohol  is  converted  into  vinegar,  small  quantities 
of  wine  or  alcohol  mixed  with  beer  are  added  daily.  When  the  acetification  becomes 


SECT.    IV.] 


ORGANIC   ACIDS. 


495 


weaker,  the  complete  conversion  of  the  free  alcohol  still  present  in  the  fluid  is  allowed 
to  take  place.  The  vinegar  is  then  drawn  off  and  the  plant  again  employed  in  the 
same  apparatus.  Vinegar  prepared  by  this  method  possesses  much  of  the  aroma 
characteristic  of  wine  vinegar.  An  essential  condition  to  the  rapid  formation  of  vinegar 
by  this  method  is  a  strong  development  of  the  plant.  A  vessel  with  i  square  metre  of 
surface,  and  capable  of  containing  50  to  TOO  litres  of  fluid,  yields  daily  5  to  6  litres  of 
vinegar.  The  vessels  are  circular  or  rectangular  wooden  tanks,  with  but  a  slight  depth, 
and  covered  with  lids.  At  the  ends  are  bored  two  small  openings  for  the  entrance  of 
the  air.  Two  tubes  of  gutta-percha,  pierced  laterally  with  small  holes,  are  carried  down 
to  the  bottom  of  the  tank,  and  used  to  pour  alcohol  into  the  tank  without  opening  the 
lid.  The  tank  which  Pasteur  employed  had  a  surface  of  i  square  metre  and  a  depth  of 
20  centimetres.  He  found  phosphates  and  ammonia  necessary  for  the  growth  of  the 
plant.  When  wine  or  malt  liquor,  &c.,  is  employed,  these  substances  are  present  therein 
in  sufficient  quantity ;  but  when  only  alcohol  is  used,  ammonium  sulphate,  potassium 
phosphate,  and  magnesia  are  added  in  such  quantity  that  the  fluid  contains  j-f7^oTrtn  °f 
this  saline  mixture,  to  which  also  some  vinegar  is  added.  It  has  been  long  known  that 
the  addition  of  bread,  flour,  malt,  and  raisins  to  alcoholic  fluids  about  to  be  acetified 
greatly  promotes  the  formation  of  vinegar,  as  these  substances  contain  the  requisite 
organic  and  inorganic  food  suited  for  the  propagation  of  the  vinegar  fungus. 

According  to  this  method  a  manufactory  for  wine  vinegar  was  established  in 
Orleans  in  1871,  and  in  1879  E.  Wurm  erected  similar  works  at  Breslau.  He  used 
large  wooden  vats,  charged  with  200  litres  of  the  vinegar  mixture,  consisting  of  water, 
alcohol,  and  acetic  acid,  along  with  the  nutritive  salts  recommended  by  Pasteur ;  i.e., 
potassium  phosphate,  o-oi  per  cent.;  calcium  phosphate,  o'oi  per  cent.;  magnesium 
phosphate,  o'oi  per  cent.;  ammonium  phosphate,  o-o2  per  cent.  The  vats  are  closely 
covered  with  wooden  lids.  Air  is  admitted  through  small  holes  at  the  sides.  The 
fungus  is  sown  by  means  of  a  small,  thin  wooden  spatula.  The  main  conditions 
are  :  a  pure  ferment,  uniform  temperature  of  30°,  and  a  regulated  inflow  of  alcohol. 
This  process  has  not  become  more  widely  used,  as  its  production  was  not  sufficiently 
abundant. 

Vinegar  by  means  of  Platinum  Black. — Dobereiner  was  the  first  who  pointed  out 
that,  with  the  aid  of  platinum  black,  alcoholic  vapours  could  be  acetified  in  a  very  short 
time ;  and  to  this  process  the  following 
apparatus  is  especially  adapted.  Fig.  381 
shows  a  small  glass  house,  in  the  interior 
of  which  are  seen  a  number  of  compart- 
ments. The  shelves  forming  these  com- 
partments support  a  number  of  porcelain 
capsules.  The  alcohol  to  be  acetified  is 
poured  into  these  capsules,  in  each  of 
which  is  placed  a  tripod,  also  of  porcelain, 
supporting  a  watch-glass  containing  pla- 
tinum black,  or  spongy  platinum.  In  the 
roof  and  at  the  bottom  of  the  apparatus 
are  ventilators,  so  constructed  as  to  admit 
of  regulating  access  of  air.  By  means  of 
a  small  steam  pipe  the  interior  of  the 
house  is  heated  to  33°.  By  this  means 
the  alcohol  is  gently  evaporated,  and 

coming  into  contact  with  the  platinum  black  or  sponge,  is  acetified.  So  long  as  the 
ventilation  is  maintained,  the  platinum  black  retains  its  property  of  oxidising  the 
alcohol.  With  an  apparatus  of  40  cubic  metres  capacity  and  with  1 7  kiloa.  of  platinum 


Fig.  381. 


496  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

black,  150  litres  of  alcohol  can  daily  be  converted  into  pure  vinegar.  If  it  be  desired  to 
prepare  the  vinegar  without  any  loss  of  alcohol,  it  becomes  necessary  to  pass  the  outgoing 
air  through  a  condenser  in  order  to  collect  the  vapours  of  alcohol  and  acetic  acid 
which  otherwise  would  be  carried  off. 

Properties  and  Examination  of  Vinegar,  Acetometry. — The  value  of  a  vinegar  is 
dependent  upon  its  flavour  and  upon  its  strength,  or  upon  the  quantity  of  acetic  acid  it 
contains.  According  to  its  containing  more  or  less  acetic  acid  the  vinegar  tastes  more 
or  less  sour.  The  colour  varies  with  the  fluid  from  which  the  vinegar  has  been  pre- 
pared ;  wine  vinegar  is  of  a  yellow  or  red-yellow  colour,  fruit  vinegar  exhibits  a  golden 
colour,  brandy  vinegar  is  colourless,  but  as  a  rule  the  latter  is  coloured  with  caramel 
in  imitation  of  wine  vinegar.  Freshly  made  vinegar  contains,  besides  small  quantities 
of  unconverted  alcohol,  some  aldehyde,  which  always  occurs  largely  in  vinegar  not 
properly  prepared.  Recently  it  has  become  customary  to  add  a  small  quantity  of  gly- 
cerine to  the  prepared  vinegar. 

The  quantity  of  acetic  acid  contained  in  a  vinegar  depends  upon  the  alcoholic  con- 
tents of  the  fluid  to  be  acetified,  and  also  upon  the  more  or  less  perfect  conversion  of 
the  alcohol  into  acetic  acid.  Malt  vinegar  contains  from  2  to  5  per  cent.,  brandy  vinegar 
from  3  to  6  per  cent.,  wine  vinegar  from  6  to  8  per  cent,  of  acetic  acid.  The  sp.  gr.  of 
various  kinds  of  vinegars  differs  from  I'oio  to  1*030;  the  more  alcohol  a  vinegar 
contains  the  lighter  is  it,  the  more  extractive  matter  the  heavier. 

Acetometry. — Commercial  vinegar  varies  greatly  as  regards  the  quantity  of  acetic 
acid  it  contains.  The  sp.  gr.  of  a  commercial  vinegar  is  no  certain  indication  of  the 
quantity  of  acetic  acid,  owing  to  the  fact  that  the  vinegar  nearly  always  contains  foreign 
matters.  The  testing  of  the  strength  can  therefore  only  be  accurately  effected  by 
means  of  saturating  it  with  an  alkali.  According  to  the  ordinary  method,  first  intro- 
duced for  this  purpose  by  Otto,  ammonia  is  added  to  the  vinegar  to  be  tested  until  the 
previously  added  tincture  of  litmus  becomes  again  blue ;  although  this  method  is  not 
absolutely  correct — owing  to  the  fact  that  the  neutral  alkaline  acetates  exhibit  an 
alkaline  reaction — this  does  not  much  impair  the  correctness  of  this  process.  Otto's 
acetometer  is  a  glass  tube  sealed  at  one  end,  36  centimetres  long  by  1*5  wide,  whereon 
is  engraved  a  double  scale  of  divisions,  one  of  these  towards  the  bottom  of  the  tube 
serving  for  measuring  the  vinegar  coloured  by  litmus,  while  the  upper  scale  is  intended 
for  measuring  the  test  liquor.  "When  it  is  intended  to  apply  the  test  with  this 
measuring  tube,  a  certain  quantity  (indicated  by  the  divided  scale)  of  litmus  tincture  is 
first  poured  into  the  tube,  next  vinegar  is  added  in  sufficient  quantity  to  fill  the  tube 
up  to  the  second  division ;  afterwards  so  much  of  the  test-liquor  is  added  as  to  restore 
again  the  blue  colour  of  the  litmus. 

A  very  useful  apparatus  for  determining  the  value  of  vinegar  and  essence  of 
vinegar  has  been  proposed  by  Hartmann  and  Hauer,  of  Hanover.  A  box  contains  a 
bottle  of  normal  potassa-lye,  a  bottle  of  an  indicator,  a  small  pipette,  a  cylinder  with  a 
back  of  milk-glass  (Fig.  382),  and  a  mixing  vessel  for  50  and  80  per  cent,  essence  of 
vinegar  and  glacial  acetic  acid  at  100  per  cent. 

The  method  of  using  the  apparatus  is  as  follows  : — The  cylinder  (Fig.  383)  is  twice 
well  rinsed  out  with  the  vinegar  to  be  tested,  shaking  it  well,  and  expelling  the  last 
drops  by  a  centrifugal  movement.  The  sample  is  poured  in  until  the  surface  of  the 
liquid  stands  a  little  above  the  zero-point,  and  so  much  liquid  is  removed  with  the 
pipette  that  the  top  line,  o  o  (Fig.  384)  of  the  liquid,  coincides  with  the  zero  mark. 
To  this  end,  the  pipette,  which  must  be  previously  shaken  out  several  times  before  use, 
is  plunged  with  its  point  into  the  liquid.  Its  upper  opening  is  then  closed  with  the 
moistened  fore-finger,  and  raised  up  until  the  point  is  just  above  the  mouth  of  the 
cylinder.  If  too  much  liquid  was  taken  out,  so  much  is  let  flow  back  by  gently  raising 
the  fore-finger  until  the  zero-point  is  reached.  "When  this  is  done,  2  drops  of  the 


SECT.    IV.] 


ORGANIC  ACIDS. 


497 


Fig.  383. 


Fig.  384 


indicated  liquid  are  added,  and  the  normal  lye  is  cautiously  run  in  until  the  red  clouds 
in  the  cylinder  disappear  more  slowly.  The  lye  is  then  added,  drop  by  drop,  until  the 
vinegar  is  completely  saturated.  As  soon 
as  the  entire  liquid  remains  red,  after 
careful  agitation,  the  operation  is  at  an 
end.  The  cylinder  is  set  on  a  horizontal 
surface,  let  stand  for  a  minute,  and  the 
degrees  consumed  are  read  off,  which  in- 
dicate how  many  per  cents,  of  absolute 
acetic  acid  (C,H402)  are  contained  in. 

Testing  Vinegar -Essence. — This  may  be 
effected  on  the  principle  just  laid  down. 

Wood  Vinegar. — After  the  dry  distil- 
lation of  wood  a  portion  of  the  carbonised 
matter  remains  in  the  retorts  as  charcoal, 
while  the  remainder  of  the  constituents 
of  the  wood  are  eliminated  partly  in  the 
state  of  gases  and  vapours,  such  as  car- 
bonic oxide,  carbonic  acid,  hydrogen,  light 
and  heavy  carburetted  hydrogens — partly 
in  the  shape  of  a  condensed  matter,  consisting  of  a  thick,  brown,  oily  fluid  floating  upon 
a  stratum  of  a  watery  liquor.  The  latter,  wood  vinegar,  consists  essentially  of  impure 
acetic  acid,  some  propionic  and  butyric  acids,  small  quantities  of  oxyphenic  acid, 
creosote,  and  an  alcoholic  wood  spirit,  a  mixture  of  methylic  alcohol,  aceton,  and  methyl 
acetate,  the  brown,  tiiickish  fluid  substance  known  as  wood  tar,  consisting  of  a 
number  of  both  fluid  and  solid  bodies,  paraffin,  napthalin,  creosote,  benzol,  toluol,  <fec. 
A  well-conducted  distillation  will  yield  as  much  as  from  7  to  8  per  cent,  of  the  weight  of 
the  wood  of  acetic  acid.  According  to  the  researches  of  H.  Yohl,  peat  can  be  employed 
in  the  preparation  of  wood  vinegar  and  of  wood  spirit.  10  cwts.  of  peat  yield  3  kilos, 
of  acetic  acid  and  1-45  kilos,  of  wood  spirit. 

Raw  wood  vinegar  contains  in  solution  a  not  inconsiderable  quantity  of  resin,  and 
also  small  quantities  of  phenol  and  guaiacol ;  all  these  bodies  impart  a  more  or 
less  brown  colour  and  empyreumatic  odour  and  flavour,  and  they  also  render  it  a 
valuable  antiseptic.  Where  the  principal  aim  is  to  obtain  wood  vinegar,  an  iron 
retort,  somewhat  similar  to  a  gas  retort,  is  employed  for  the  distillation  of  the  wood. 
In  large  factories,  instead  of  the  wooden  receivers,  large  stone  or  brickwork  cisterns  are 
employed,  generally  several  of  such  tanks  being  used,  the  largest  quantity  of  tar  being 
condensed  in  the  first  cistern,  while  the  wood  vinegar,  mechanically  freed  from  the  tar 
and  floating  on  its  surface,  finds  its  way  into  a  second  cistern.  Pettenkofer's  patent 
wood-gas  generators  produce  a  not  inconsiderable  quantity  of  wood  vinegar. 

Purifying  Wood  Vinegar. — Raw  wood  vinegar  is  a  clear  dark  brown  fluid,  having  a 
tarry  taste  and  smoky  odour.  It  is  employed  in  small  quantities  in  the  preservation 
of  meat,  also  for  the  preservation  of  wood,  ropes,  &c. ;  but  by  far  the  largest  quantity 
is  employed  in  the  manufacture  of  the  various  acetates  used  in  dyeing  and  calico 
printing,  chiefly  as  crude  iron  acetate  and  crude  aluminium  acetate.  It  is  also  used 
in  the  preparation  of  concentrated  acetic  acid  for  industrial  purposes ;  that  is,  for  the 
production  of  aniline  from  nitro-benzol,  and  of  sugar  of  lead  (lead  acetate).  Lastly, 
it  is  largely  used  in  the  preparation  of  table  vinegar,  an  operation  economical  only 
where,  as  in  England,  there  is  a  high  duty  on  alcoholic  fluids. 

Among  the  means  of  purifying  crude  wood  vinegar,  the  most  simple — leaving  out 
of  the  question  the  filtration  of  the  crude  liquor  over  coarsely  granulated  wood  charcoal 
as  recommended  by  E.  Assmus — is  distillation,  an  operation  usually  carried  on  in  a  still 

2   I 


498  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

made  of  copper  fitted  with  a  copper  condensing  apparatus.  At  first  a  yellow  fluid 
comes  over — raw  wood  spirit,  from  which  the  wood  spirit  of  commerce  is  prepared — and 
next  the  distillate  becomes  richer  in  acetic  acid. 

The  principal  methods  at  present  employed  for  the  purification  of  wood  vinegar 
may  be  considered  as  falling  under  either  of  two  classes : — 

a.  The  first  includes  the  purifying  of  wood  vinegar  without  saturation  with  a  base ; 
while 

b.  The  second  includes  those  methods  in  which  the  wood  vinegar  is  purified  by- 
conversion into  an  acetate,  the  acetic  acid  being  next  separated  by  distillation  with  an 
acid  possessing  greater  affinity  for  the  base. 

To  the  first  class  belongs  Stoltze's  method,  consisting  in  first  obtaining  by  distillation 
10  per  cent,  of  a  liquid  which  is  employed  for  the  preparation  of  wood  spirit;  80  per 
cent,  of  the  liquid  is  next  distilled  off,  and  the  empyreumatic  substances  contained  are 
destroyed  by  the  action  of  either  ozone  or  chlorine.  The  purification  of  the  crude 
wood  vinegar  by  the  second  method  is  more  generally  in  use  among  manufacturers, 
the  inventor  of  the  system  being  Mollerat.  The  crude  wood  vinegar  is  first  saturated 
with  lime,  and  the  solution  next  precipitated  with  Glauber's  salt  to  obtain  sodium 
acetate ;  this  salt  is  purified  by  crystallisation,  and  when  in  a  dry  state  is  so  far  heated 
that  the  empyreumatic  matter  it  is  mixed  with  becomes  carbonised,  and  is  thus 
rendered  insoluble ;  the  sodium  acetate  is  then  extracted  with  water,  and  the  acetic 
acid  separated  from  it  by  distilling  the  previously  crystallised  and  dried  salt  with 
sulphuric  acid.  Instead  of  sodium  acetate,  the  calcium  acetate  is  frequently  employed 
in  the  preparation  of  acetic  acid  from  crude  wood  vinegar,  the  latter  being  saturated 
with  lime,  and  the  salt  formed  evaporated  to  dryness.  The  dry  salt  is  roasted  am! 
treated  similarly  to  the  sodium  acetate  to  calcine  any  empyreumatic  products.  The 
acid  is  employed  in  the  distillation  is,  according  to  the  method  invented  by  C.  Yolckel, 
hydrochloric  acid.  The  distillation  can  be  effected  in  a  retort  with  a  helm  of  copper 
and  a  condenser  of  lead,  tin,  or  silver.  To  100  parts  of  acetate  of  lime  90  to  95 
parts  of  hydrochloric  acid  at  ri6  sp.  gr.  are  used.  When  hydrochloric  acid  is  used  in 
this  preparation,  instead  of  sulphuric  acid,  any  contamination  of  the  crude  calcium 
acetate  with  empyreumatic  or  tarry  matter  does  not  affect  the  purity  of  the  acetic  acid 
which  is  obtained,  provided  the  crude  acetate  be  first  so  well  dried  as  to  be  free  from 
all  other  volatile  substances ;  when  sulphuric  acid  is  used  for  this  purpose,  the  result 
is  that  an  acetic  acid  is  obtained,  which  contains  not  only  a  large  quantity  of 
sulphurous  acid,  but  also  offensive  volatile  compounds,  due  to  the  decomposition  (by  the 
sulphuric  acid)  of  empyreumatic  resins  and  tarry  matter  present  in  the  crude  calcium 
acetate. 

For  the  preparation  of  acetic  anhydride  250  kilos,  of  sodium  acetate,  previously 
dried  to  a  dust,  are  placed  in  a  double  kettle  fitted  with  an  agitator.  The  temperature 
in  the  kettle  is  raised  to  140°,  and  a  strong  current  of  chloro-carbonic  oxide  is 
introduced.  The  oil  which  distills  over  must  be  carefully  condensed,  as  it  has  a  very 
irritating  effect  on  the  mucous  membranes.  The  crude  product  (150  kilos.)  is 
submitted  to  fractional  distillation,  and  100  kilos,  of  fairly  true  anhydride  may  thus  be 
obtained.  The  temperature  of  140°  must  not  be  exceeded,  as  otherwise  acetose  is 
formed  in  considerable  quantities,  and  can  scarcely  be  completely  separated  from  the 
anhydride. 

Formic  Acid,  HCHO2,  a  natural  secretion  of  ants  [and  many  other  insects,  e.g.,  larva* 
of  Cerura  vinula,  Gychrus  rostratus,  &c.]  is  obtained  by  heating  oxalic  acid  with 
glycerine. 

According  to  Lorin,  we  mix  at  108°  equal  equivalents  of  oxalic  acid  and  gly- 
cerine in  small  properties,  allowing  the  escape  of  gas  to  come  to  an  end  after 
«ach  addition.  At  first  more  water  is  liberated  than  corresponds  to  the  carbon 


SECT.   IV.] 


ORGANIC  ACIDS. 


499 


dioxide  evolved,  and  the  water  split  off  on  etherification ;  the  oxalic  acid  at  first 
yields  up  simply  its  water  of  crystallisation.  Subsequently  the  production  of  water 
and  formic  acid  ceases  almost  entirely,  though  much  carbon  dioxide  is  still  liberated,  and 
ultimately  the  water  which  has  escaped  is  exactly  equal  to  the  crystalline  water  and 
that  formed  by  etherification,  since  about  91  per  cent,  of  the  formic  acid  are  com- 
bined with  glycerine.  The  same  phenomena  occur  on  further  additions:  the  oxalic 
acid  expels  a  part  of  the  combined  formic  acid  ;  the  newly-formed  formic  acid  escapes 
in  part,  and  is  partly  taken  up  by  the  glycerine.  At  the  third  addition  the  glycerine 
is  almost  completely  saturated,  and  43  grammes  of  formic  acid  have  been  liberated.  At 
the  fourth  addition  there  is  formed  from  i  equiv.  of  oxalic  acid  exactly  i  equiv.  formic 
acid  and  the  crystalline  water.  The  synthetic  production  of  formic  acid  by  the  action 
of  moist  carbon  monoxide  upon  soda-lime  at  about  200°  deserves  attention. 

Butyric  acid,  H.C4H7O,,  is 'obtained  by  the  fermentation  of  a  solution  of  sugar 
mixed  with  putrid  cheese.  Fitz  dissolves  180  grammes  sugar  in  6  litres  water,  adds  o'l 
gramme  potassium  phosphate,  0*02  magnesium  sulphate,  i  gramme  ammonium  chloride, 
and  70  grammes  calcium  carbonate,  heats  to  110°,  lets  cool,  and  sows  with  a  pure 
culture  of  Bacillus  butylicus.  He  thus  obtains  42  grammes  pure  butyric  acid.  Stinde 
recommends  50  kilos,  carobs  (Ceratonia  siliqua)  crushed  up  to  a  thin  paste  with  water 
at  28°,  adds  after  four  or  five  days  12  kilos,  of  elutriated  chalk,  and  lets  the  whole 
ferment,  which  in  summer  is  completed  in  six  weeks.  The  thick  pasty  mass  is  then 
etherified  in  a  copper  still  by  a  mixture  of  18  kilos,  sulphuric  acid  and  30  kilos,  alcohol 
at  95  per  cent. 

Butyric  ether  is  used  in  perfumery  as  rum — or  cognac  ether. 

Valerianic  acid,  H.C5HgO2,  is  chiefly  obtained  by  heating  amylic  alcohol  with  potas- 
sium dichromate  and  sulphuric  acid.  Its  ethylic  and  amylic  ethers  are  extensively  used 
as  fruit  ethers  (oil  of  apples). 

Oxalic  Acid.,  H8.C2O4,  a  constituent  of  many  plants  (oxalis),  is  now  almost  ex- 
clusively obtained  by  melting  sawdust  with  caustic  potassa.  Mixtures  of  potassa  and 
soda  give  a  smaller  yield. 

Thorn  added  50  parts  of  sawdust  to  100  parts  hydrated  alkali  in  the  state  of  a  lye 
of  98°  Tw.,  and  then  heated  it  in  a  layer  of  i  centimetre  in  thickness  with  frequent 
stirring.  He  obtained  the  following  yields : — 


Proportion  of  KHO  to  NaHO. 

Temperature. 

Oxalic  acid. 

Per  cent. 

O-IOO 

2OO°-22O° 

33T4 

10-90 

230° 

S8-36 

20-80 

24O°-25O° 

74*76 

30-70 

240  —  250 

7677 

40-60 

240  —  250 

80-57 

60-40 

240°  —  250 

80-08 

80-20 

245° 

81-24 

IOO-O 

81-23 

In  experiments  with  different  woods  it  was  observed  that  soft  woods  proved  to  be 
the  best  material.  On  heating  50  parts  of  wood  with  40  parts  KOH  and  60  NaOH,  in 
thin  layers,  there  was  obtained  : — 


Kind  of  Wood. 

Moisture. 

.Oxalic  acid. 

Oxalic  acid  calculated  in 
wood  dried  at  100°. 

Per  cent. 

Per  cent. 

Per  cent. 

Pine 

15-0 

8o-s 

94-70 

Fir   . 

I5-0 

80-5 

94-70 

Poplar 

I4'0 

80-1 

93-14 

Beech 

8-6 

79"o 

86-43 

Oak. 

6-5 

75-1 

83-42 

5oo  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

The  melt  is  lixiviated  with  water,  the  solution  is  boiled  with  milk  of  lime,  and  the 
calcium  oxalate  is  decomposed  with  sulphuric  acid.  If  a  mixture  of  soda  and  potassa 
is  used  for  melting,  the  lye  is  concentrated  to  66°  Tw.,  when  the  sodium  oxalate  crys- 
tallises out  and  is  freed  from  the  mother  liquor  in  a  filter-press  or  a  centrifugal.  The 
sodium  oxalate  is  dissolved  in  boiling  water  and  the  liquid  is  boiled  with  milk  of  lime 
for  some  hours.  It  is  advantageous  to  use  the  solution  very  dilute,  as  otherwise  the 
decomposition  takes  place  very  slowly.  When  a  filtered  specimen  no  longer  gives  the 
reaction  of  oxalic  acid  the  lye  is  drawn  off,  the  precipitate  is  washed  with  hot  water 
and  filtered.  The  lye  is  used  again.  An  excess  of  sulphuric  acid  is  required  for  the 
decomposition  of  the  calcium  oxalate,  according  to  Chandelon,  3  mols.  sulphuric  acid 
to  i  mol.  calcium  oxalate.  The  salt  is  stirred  up  with  water  to  a  thin  paste,  and  the 
requisite  quantity  of  sulphuric  acid  (at  22°  to  30°  Tw.)  is  stirred  in.  It  is  then  heated 
for  some  hours,  after  the  addition  of  water,  and  filtered  off  from  the  calcium  sulphate. 
The  solution,  which  along  with  oxalic  acid  contains  sulphuric  acid  and  gypsum,  is  con- 
centrated to  22°  Tw.  Gypsum  separates  out  on  standing,  and  after  its  removal  the 
liquor  is  further  concentrated  to  50°  Tw.  On  cooling,  oxalic  acid  separates  out  in  long 
crystals,  and  is  purified  by  recrystallisation.  The  sulphuric  acid  can  also  be  used 
again. 

According  to  Merz,  by  quickly  heating  sodium  formiate  with  the  utmost  possible 
exclusion  of  air  to  above  400°,  a  saline  mass  is  formed,  which  contains  along  with  car- 
bonate 70  per  cent,  and  more  of  oxalate.  At  lower  temperatures  more  carbonate  is 
formed.  Potassium  formiate  behaves  in  a  similar  manner ;  calcium,  barium,  and 
magnesium  formiates  yield  merely  carbonates.  It  is,  perhaps,  possible  that  the 
synthetic  formation  of  sodium  formiate  by  means  of  carbon  monoxide  and  its  conver- 
sion into  oxalate  may  prove  a  more  advantageous  method  for  the  production  of  oxalic 
acid  than  the  reaction  of  caustic  potassa  upon  sawdust.* 

Oxalic  acid  is  used  for  bleaching  straw,  as  a  discharge  in  tissue  printing,  and  in 
certain  mordants  used  in  woollen  and  silk  dyeing.  Its  most  important  salts  are  the 
acid  potassium  and  antimony  oxalate,  now  used  in  tissue  printing  instead  of  tartar 
emetic. 

Lactic  Acid,  H.C2H503,  is  obtained  by  the  fermentation  of  sugar  with  cheese,  or 
preferably,  according  to  Kiliani,  by  heating  inverted  sugar  with  soda  lye.  Antimony 
lactate  serves  as  a  mordant  in  dyeing  in  place  of  tartar-emetic. 

Tartaric  Acid,  H2.C4H406. — Only  the  dextro-rotary  tartaric  acid  is  of  technical  im- 
portance. It  is  contained  in  grape  juice  and  is  deposited  during  fermentation  as 
so-called  tartar,  or  argol,  which  consists  chiefly  of  potassium  bitartrate.  According 
to  Kurtz,  500  to  700  kilos,  of  crude  argol  are  heated  to  boiling  in  a  wooden  vat  by  the 
introduction  of  steam.  Half  the  tartaric  acid  is  then  precipitated  by  the  addition  of 
powdered  chalk.  Less  than  the  theoretical  quantity  of  chalk  must  be  used  (18-8 
potassium  bitartrate  require  5  parts  of  chalk),  as  the  crude  argol  rarely  contains  more 
than  80  per  cent,  of  acid  potassium  tartrate,  and  besides  on  complete  neutralisation  the 
magnesia,  alumina,  and  iron  oxide  would  be  also  precipitated.  With  tartars  and  argols, 
which  are  very  rich  in  such  impurities,  it  is  advisable  at  the  beginning  of  the  operation 
to  add  12  to  25  kilos,  hydrochloric  acid,  and  not  to  neutralise  completely,  as  otherwise 
during  the  crystallisation  of  the  tartaric  acid  the  presence  of  alum,  magnesium  sulphate, 
&c.,  would  cause  much  annoyance. 

To  convert  the  neutral  potassium  tartrate  into  the  calcium  salt,  Kurtz  recommends 
gypsum  when  cheaper  than  calcium  chloride.  8'6  parts  of  gypsum  equal  5  parts  of 
chalk.  The  gypsum  may  be  added  before  or  during  the  neutralisation  with  chalk,  and 
an  excess  does  no  harm.  As  the  calcium  tartrate  obtained  from  the  lyes  is  very  pure, 
pure  gypsum  is  used  for  working  it  up  for  potassium  tartrate.  The  reaction  of  the 
calcium  sulphate  with  neutral  potassium  tartrate  is  slow,  and  requires  several  hours. 
*  It  was  formerly  obtained  by  the  action  of  nitric  acid  on  sugar. 


SECT,  iv.]  ORGANIC  ACIDS.  501 

As  soon  as  acetic  acid  occasions  no  precipitate  in  a  cooled  and  filtered  specimen,  the 
reaction  is  at  an  end.  The  contents  of  the  vat  are  allowed  to  cool  down  to  50°,  and 
are  let  off  into  another  vat  intended  for  the  deposition  of  the  calcium  tartrate,  passing 
through  a  sieve  in  order  to  keep  back  chips  of  wood,  grape  stalks,  &c.,  usually  present 
in  crude  argols.  In  three  to  four  hours  the  calcium  tartrate  is  deposited,  and  the  lye 
is  drawn  off  with  a  syphon.  It  is  rich  in  potassium  sulphate.  When  the  lime  salt 
has  been  washed  three  times  it  is  sufficiently  clear  for  further  treatment. 

In  working  up  wine-lyes  the  alcohol  present  is  first  distilled  off;  then  about  2500 
kilos,  are  placed  in  a  vat  holding  from  100  to  150  hectolitres,  which  is  almost  filled  with 
water.  About  50  kilos,  of  crude  hydrochloric  acid  are  added,  and  the  whole  is  heated 
almost  to  boiling  whilst  stirring.  The  contents  are  then  allowed  to  settle,  and  the  clear 
liquid  is  drawn  off  through  syphons  into  a  second  vat,  in  which  it  is  nearly  neutralised  with 
powdered  chalk  whilst  being  constantly  stirred.  All  the  tartaric  acid  is  precipitated  by 
the  calcium  chloride  which  is  formed.  The  liquid  is  drawn  off  into  a  third  vat,  where 
the  calcium  tartrate  is  deposited  and  washed.  The  muddy  sediment  of  the  first  vat  is 
pressed  to  recover  any  tartaric  acid  present,  and  the  residue  can  be  worked  up  for 
Frankfort  black. 

The  process  of  Dieter  has  also  proved  successful.  It  consists  in  heating  the  crude 
tartar,  or  the  dried,  or  the  freshly  pressed  and  liquid  lyes,  to  140°— 170°,  which 
is  effected  by  steam  at  a  pressure  of  3  to  7  atmospheres,  in  closed  pans ;  or  by  boiling 
under  pressure,  and  by  dry  roasting  with  superheated  steam.  The  impure  product  is 
easily  lixiviated,  and  the  tartaric  acid  solution  is  separated  out  by  means  of  filter-presses. 
The  calcium  tartrate  is  decomposed  by  sulphuric  acid.  More  than  the  theoretical 
quantity  of  sulphuric  acid  must  be  used  (which  would  be  4*9  parts  to  9^4  calcium 
tartrate),  as  fine  crystals  of  tartaric  acid  can  be  obtained  only  from  solutions  containing 
strong  mineral  acids.  The  presence  of  small  quantities  of  calcium  tartrate  or 
potassium  sulphate  (resulting  from  imperfect  washing  of  the  calcium  tartrate)  greatly 
disturbs  the  crystallisation.  The  lime-salt  is  mixed  with  the  sulphuric  acid,  the 
needful  amount  of  water  is  added  to  obtain  a  paste  which  admits  of  stirring,  and  it  it 
heated  by  means  of  steam  to  75°  with  agitation.  As  soon  as  the  sulphuric  acid  is  in  a 
certain  excess  (which  is  judged  by  the  bulk  of  the  precipitate  produced  by  a  filtered 
specimen  with  calcium  chloride),  the  tartaric  acid  is  separated  from  the  gypsum  by 
filtration,  and  is  boiled  down  in  leaden  pans  by  means  of  a  steam  worm  of  lead,  when 
a  little  gypsum  separates  out.  As  the  lye  becomes  more  concentrated  the  heat  must 
not  be  allowed  to  exceed  70°— 75°,  as  otherwise  the  tartaric  acid  will  be  turned  brown 
by  the  sulphuric  acid.  At  the  concentration  of  72°  Tw.  the  lye  is  run  into  wooden 
tanks  lined  with  lead,  or  large  earthenware  pans,  and  allowed  to  crystallise.  The  mother 
liquors  are  evaporated  down  three  times,  taking  each  time  a  crop  of  crystals.  The 
fourth  mother  liquor  is  treated  as  a  raw  material.  The  crystals  are  whizzed,*  redissolved, 
and  decolorised  with  bone-black  ;  the  solution  is  filtered,  mixed  with  a  little  sulphuric 
acid,  evaporated  down  to  72°  Tw.,  and  again  run  into  the  crystallisers.  The  acid, 
which  is  now  finely  crystallised,  is  whizzed  and  dried. 

In  some  works  the  evaporation  of  the  tartaric  solutions  is  very  successfully  carried 
on  in  lead  vacuum  pans. 

The  yearly  production  of  tartaric  acid  is,  in  hectokilos. : 

Germany 8000 

Austria-Hungary 5000 

France 3000 

Italy    .........     2000 

Spain 500 

Britain 13,000 

United  States 12,000 

amounting  in  value  to  16-20  million  marks. 

*  The  ordinary  technical  expression  for  treatment  in  a  centrifugal  machine. 


Soa  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

Tartaric  acid  is  used  in  large  quantities  as  a  discharge  in  tissue  printing,  as  a 
mordant  in  dyeing  (in  the  state  of  acid  potassium  tartrate),  in  the  preparation  of 
baking-powders,  effervescing  drinks,  &c. 

Citric  Acid,  H3.C6H507,  is  especially  present  in  the  juice  of  lemons  and  limes  (6  to  7 
per  cent.),  and  of  currants.  To  obtain  it,  limejuice  is  precipitated  with  milk  of  lime, 
the  calcium  citrate  is  decomposed  with  sulphuric  acid,  and  the  solution  of  citric  acid  is 
evaporated  down.  Citric  acid  is  used  as  a  discharge  in  tissue  printing  and  in  the 
manufacture  of  lemonades. 

Benzole  Acid,  H.CrH40,,  is  prepared  for  medicinal  uses  from  the  gum-resin  benzoin. 
For  technical  purposes  it  is  obtained  from  hippuric  acid  or  from  naphthalene  or 
toluene.  In  its  preparation  from  hippuric  acid,  which  on  boiling  with  dilute  acids  or 
on  putrefaction  is  split  up  into  benzoic  acid  and  glycocol,  the  urine  of  horses  or  cows 
is  either  boiled  for  a  long  time  with  hydrochloric  acid  or  it  is  allowed  to  putrefy,  pre- 
cipitated with  milk  of  lime,  filtered,  the  filtrate  is  concentrated,  and  the  benzoic  acid  is 
thrown  down  by  hydrochloric  acid.  For  purification  it  is  dissolved  in  weak  milk  of 
lime  with  a  little  chloride  of  lime,  reprecipitated  by  hydrochloric  acid  and  recrys- 
tallised.  The  acid  thus  obtained  has  a  slightly  urinous  odour. 

For  obtaining  benzoic  acid  from  the  phthalic  acid  produced  by  the  oxidation  of 
naphthalene,  its  calcium  salt  is  heated  to  33o°-35o° : 

2CaC8H404  +   Ca(OH)a  =   Ca(CTH5Oa),  +   aCaCO,. 

According  to  Laurent,  the  ammonium  compound  of  phthalic  acid  by  dry  distillation 
is  converted  into  phthalimide,  and  this  again  by  distillation  with  slaked  lime  into 
benzonitril ; 

C8H5OaN   +  Ca(OH),  -  C,H4N  +   2CaCO,  +  H,O. 

On  boiling  with  caustic  soda  lye,  benzonitril  is  converted  into  sodium  benzoate,  whilst 
ammonia  is  liberated : 

CrH5N   +   NaHO   +   H2O  =  NaC,H5Oa   +  NH3. 

Sodium  Benzoate. — Toluene  is  converted  into  benzylchloride,  C7H?C1,  by  treat- 
ment with  chlorine,  and  this  compound,  if  heated  with  water  under  pressure  or  boiled 
with  dilute  nitric  acid,  passes  into  benzoic  acid.  G.  Lunge  boils  100  parts  benzyl- 
chloride  with  300  parts  nitric  acid  at  60°  Tw.  and  200  parts  of  water  for  ten  hours, 
with  a  reflux  condenser.  Benzoic  acid  melts  at  121°  and  boils  at  249°. 

Tannin,  C14H1009,  is  found  chiefly  in  nut-galls  and  also  in  sumac.  It  is  obtained  by 
extracting  powdered  nut-galls  with  ether.  A  mixture  commonly  employed  consists  of 
30  parts  ether,  4  parts  water,  and  i  part  alcohol.  The  acid  obtained  by  evaporation 
may  be  purified  from  the  accompanying  gallic  acid  by  solution  in  lime  and  precipitation 
with  solid  sodium  chloride,  or  by  repeated  solution  in  water  and  treatment  with 
animal  charcoa 

Tannin  serves  for  clarifying  wines  (rarely  beers),  but  chiefly  as  a  mordant  in  dyeing, 
for  the  production  of  ink  and  of  pyrogallol,  and  in  medicine. 

TREATMENT  OF  COAL-TAR. 

The  so-called  aromatic  compounds  are  almost  entirely  obtained  from  coal-tar. 
Most  tar  is  obtained  in  the  manufacture  of  coal-gas,  and  a  smaller  quantity  from  coke- 
burning.  The  composition  of  the  tar  depends  on  the  quality  of  the  coal,  but  still  more 
on  the  temperature  employed. 

According  to  Wright,  the  specific  gravity  of  tar  is  the  higher  the  stronger  the  heat 
which  has  been  employed.  Five  tars  obtained  from  the  same  coals,  but  at  an  increasing 
temperature,  yielded : 


SECT.   IV.] 


TREATMENT  OF  COAL-TAR. 


503 


I. 

II. 

in. 

IV. 

V. 

I  -086 

I'IO2 

1-140    ... 

1-154 

1-206 

I  -2O 

...      1-03 

1-04 

1-05 

...    0-38 

9-I7 

...      9-05 

-      373      - 

3-45 

...     0-99 

lO'SO 

...      7'46 

...      4-47      — 

2-59 

...    0-57 

26-45 

-    25-83 

...     27-29      ... 

27-33 

...    19-44 

20-32 

•ft     J5'57 

...     18-13      ... 

13-77 

...    12-28 

28-89 

...    36-80 

...    41-80      ... 

47-67 

...   64-08 

Specific  gravity  of  tar 

Ammonia  liquor 

Crude  naphtha 

Light  oils 

Creosote  oils 

Anthracene  oils 

Pitch         .        .        .'"'". 

The  quantity  of  crude  naphtha  (benzol,  &c.)  of  the  light  oils  and  the  phenols  de- 
creases rapidly  with  the  rise  of  temperature.     Tar  from  the  Berlin  gasworks  contains 

in  100  parts : 

Benzol  and  Toluol o-8 

Other  clear  oils O"6 

Phenol 0-2 

Naphthaline 3*7 

Anthracene  (pure) o'2 

Heavy  oils 24*0 

Pitch  for  asphalt  and  briquettes,  &c.     .        .  55*0 

For  the  distillation  of  tar,  Lunge  recommends  the  still  intended  for  25  tons  of  tar, 
of  which  Fig.   385   shows  Fi 

the  section,  on  the  line  E 
F  of  the  ground  -  plan  ; 
Fig.  386  a  section  through 
D  C'  of  Fig.  385  ;  Fig.  387 
a  section  through  the  body 
of  the  still  itself  along  A  B 
of  Fig.  385.  The  body  is 
3  metres  in  width  and  3^ 
metres  high  without  the 
capital,  and  is  constructed 
of  boiler-plates  10  mm.  in 
thickness.  A  concavity  of 
the  bottom  corresponds  ap- 
proximately to  the  con- 
vexity of  the  cover.  The 
body  may  have  a  very  slight 
slope  towards  the  side  of 
the  outflow  cock,  a,  which, 
however,  must  be  placed  as 
close  as  possible  to  the 
bottom  or  even  in  its  flat 
part. 

The  fire-box,  b,  is  ac- 
cessible from  without  by 
the  door,  c,  which  must  be 
placed  on  the  side  opposite 
to  the  exit-cock  for  the 
pitch.  In  the  drawing  is 
shown  the  arrangement  of 
one  of  the  largest  English 
manufactories,  in  which  the 
wall  underneath  the  fire- 
doors  is  closed  in  front,  and 
the  ashpits  are  all  connected  through  the  opening,  d,  with  a  large  vaulted  channel,  e, 


CHEMICAL  TECHNOLOGY. 


[SECT.  rv. 


Fig.  386. 


which  runs  underneath  the  entire  series  of  stills,  and  which  is  accessible  only  at 
both  ends.  This  affords  complete  security  against  the  danger  of  fire,  in  case 
the  tar  in  the  stills  should  boil  over,  fill  the  receivers,  and  flow  away  from  the 

latter. 

The  flame  strikes  over  the  fire-bridge,  /,  and  beneath  the  vault,  g.  The  latter  is 
struck  as  a  tun-vault  from  the  circular  wall,  k,  upon  which  the  still  rests,  and  com- 
pletely protects  its  bottom  from  the  pointed  flame.  The  space  between  g  and  the 
bottom  of  the  still  is  merely  an  air-bath,  the  temperature  of  which  is  kept  high  by  the 

flame  playing  underneath  ^,  but 
can  never  become  excessive.  In 
g  so  much  heat  is  stored  up  that 
towards  the  end  of  the  distillation 
there  is  no  need  to  fire  up.  The 
weight  of  the  still-body,  resting 
upon  the  ring-wall,  Jc,  makes  the 
latter  a  safe  bed  for  the  protective 
vault,  which  is  quite  independent 
of  the  masonry  of  the  fire-box, 
and  can  be  repaired  without  in- 
terfering with  the  work.  The 
flame  passes  through  the  four 
flues,  h,  into  two  vertical  chan- 
nels, i,  to  arrive  at  the  cylindrical 
jacket-wall  of  the  still.  The  mas- 
sive pillar,  i',  between  the  chan- 
nels, i,  is  continued  some  distance 
above.  In  it  there  lies,  protected 
from  the  fire,  but  kept  warm  by 
the  channels,  i  and  p,  running 
close  alongside,  the  pipe  which 
connects  the  exit-cock  with  the 
body  of  the  still.  The  pillar,  i, 
compels  the  flame  to  divide  into 
a  left  and  a  right  stream,  which 
pass  round  the  lowest  part  of  the 
still-body  in  the  ring- channels,  I, 
are  hindered  from  uniting  in 
front  by  the  pillar  i",  pass  through 
the  flues,  m,  into  the  upper  ring- 
channel,  n,  pass  again  backwards, 
and  open  through  o  into  the  per- 
pendicular shafts,  p,  which  are 
connected  with  the  main  smoke- 
flue,  q.  The  shafts,  p,  are  inter- 
rupted at  suitable  places  by  slides, 
by  means  of  which  a  uniform 
heat  can  be  kept  up  on  both  sides  of  the  still-body.  Above  the  fire  flues  the  body 
is  protected  against  the  radiant  heat  with  a  wall,  0*22  metre  in  thickness; 
this  is  carried  up  above  the  cover,  and  preferably  above  the  ascending  part,  t,  of  the 
capital.  A  protection  of  this  kind  is  the  more  necessary  when,  as  it  is  to  be  recom- 
mended, the  stills  are  quite  in  the  open  air,  or  merely  covered  with  a  slight  roof  of 
corrugated  iron.  Any  explosions  or  fires  are  then  much  less  destructive  than  when 


SECT,  iv.]  TREATMENT   OF  COAL-TAR.  505 

the  stills  are  fixed  in  a  massive  building.  When  the  stills  are  uncovered,  the  masonry 
should  be  coated  with  melted  pitch  as  a  protection  against  the  rain. 

The  charging  is  effected  by  means  of  the  cast-iron  pipe,  r,  closed  with  a  slide  cock  or 
otherwise,  and  about  0*15  metre  in  width,  so  as  not  to  take  too  much  time  in  filling  the 
still.  If  the  tar  is  not  pumped  in,  but  let  flow  down  from  a  tank  at  a  higher  level, 
there  is  provided  a  filling-hole,  which  is  afterwards  closed  with  a  conical  iron  plug  or  a 
screw.  There  is  also  an  air-hole  through  which  the  height  of  the  liquid  can  be  gauged ; 
preferable  to  both  is  an  overflow  cock,  s,  of  25  millimetres  in  width.  Through  this 
there  escapes  at  first  air ;  if  tar  flows  the  feeding  is  stopped  and  *  is  closed. 

The  vapours  are  led  through  the  cast  iron  capital,  t,  which  tapers  from  0*3  to  0*15 
metre,  and  is  then  prolonged  into  an  iron-pipe  of  the  same  width,  leading  to  the  cooler. 
Sometimes  there  is  placed  at  the  base  of  the  capital  in  the  inside  a  channel  which 
leads  the  liquids  condensing  in  the  ascending  part  of  the  capital  direct  to  the  outside,  so 
that  they  may  not  drop  back  into  the  still,  and  occasion  frothing.  This  arrange- 
ment is  scarcely  necessary  if  the  ascending  part  of  the  capital  is  covered  with  poor 
conductors  of  heat.  Sometimes  a  steam-pipe  is  made  to  open  into  the  capital  to 
remove  any  obstruction.  But  with  a  capital  of  the  above  width  and  with  a  slight  fall 
such  stoppages  cannot  happen. 

Each  still  has  a  man-hole.  This  is  shown  at  u,  as  in  a  steam  boiler,  and  is 
closed  by  a  lid  pressed  down  by  a  screw  handle.  It  is  tightened  either  by  a  border 
of  fatty  clay  or  a  ring  of  asbestos  paper.  In  some  places  the  cover  of  the  man- 
hole acts  as  a  safety-valve.  It  consists  then  of  an  iron  plate  lying  loosely  upon 
a  corresponding  short  tube,  the  connecting  joints  being  connected  with  some  cement 
which  does  not  set  too  hard.  If  the  pressure  in  the  still  rises  too  high  the  cover 
of  the  man-hole  is  thrown  off  before  injury  can  be  done.  In  default  of  such  an 
arrangement  a  real  safety  valve  should  be  provided,  as  is  here  shown  at  w,  though  many 
stills  are  left  without  such  an  arrangement.  It  is  very  convenient  to  attach  a  lateral 
pipe  leading  away  from  the  capital,  with  a  safety  valve  opening  downwards,  so  that  in 
case  of  boiling  over  the  tar  may  be  led  to  a  place  protected  from  fire.  The  insertion 
of  a  thermometer,  v,  is  to  be  recommended.  It  is  inclosed  in  an  iron  tube  filled  with 
iron  filings  and  mercury  and  reaching  down  to  half  the  depth  of  the  still. 

In  the  figure  there  is  seen  a  system  of  tubes,  x  y  z,  for  introducing  steam  into  the 
still.  This  is  generally  effected  merely  by  cross  tubes  with  apertures  in  their  arms  for 
the  escape  of  the  steam.  Here  the  full  arrangement  is  shown  as  designed  by  Trewly 
and  Fenner.  The  steam  is  led  in  by  a  pipe  25  millimeteres  in  width,  with  a  cock,  x, 
which  gives  off  in  the  inside  three  descending  pipes,  y  z  y.  Of  these  y  is  connected 
with  the  ring-tube,  y',  which  lies  at  the  lowest  part  of  the  still,  and  z  is  in  connection 
with  a  system  of  branch  tubes,  z,  which  cover  the  entire  bottom  of  the  still.  Both 
from  y  and  from  z'  there  branch  off  a  great  number  of  open,  slightly  curved  exit  tubes 
with  tapering  mouths.  The  steam  streaming  in  through  this  apparatus  is  divided  into 
very  many  slender  jets,  which  sweep  over  all  parts  of  the  still-bottom,  prevent  it  from 
being  overheated,  and  carry  along  the  vapours  of  the  heavy  hydrocarbons.  In  conse- 
quence of  the  great  surface  of  the  distribution  tubes  the  steam  becomes  superheated 
before  escaping,  and  there  is  no  need  for  a  special  superheater. 

Another  still,  for  a  charge  of  25  tons,  has  the  dimensions  given  in  Fig.  388.  The 
vaulted  bottom  is  rivetted  together  out  of  1 2  plates  fixed  star-shaped,  which  are  united 
at  their  inner  ends  by  a  round  plate.  A  German  establishment  has  larger  stills,  of  4 
metres  diameter  and  4  metres  in  height  from  the  lower  angle  of  the  bottom  to  the 
upper  angle  of  the  cover,  and  are  fitted  for  the  distillation  of  35  tons  of  tar.  The 
bottom  of  the  still  either  lies  in  the  open  fire  or  is  protected  by  a  grating,  which 
is  always  to  be  recommended  where  thick  tars  are  worked,  which  readily  form  a 
deposit  of  coke  on  the  bottom  and  allow  the  plates  to  become  red  hot.  The  cooling 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


worms  have  an  inside  width  of  at  least  13  centimetres  and  an  incline  of  2  per  cent,  in 
a  length  of  48  metres.  The  trough  for  receiving  the  cooling  worm  is  5!  metres  long, 
1-53  metre  wide,  and  1-23  metre  deep.  The  longitudinal  tubes  lie  no  metre  apart, 
measured  from  middle  to  middle,  and  the  cross  tubes  are  476  metres  apart,  so  that  the 
total  surface  traversed  by  the  tar  is  about  20  square  metres,  whilst  the  largest  section  of 

Fig-  388. 

--W8S- 


the  still  is  io|  square  metres.  The  cooling  worm  is  of  wrought  iron,  and  only  that  part 
which  stands  up  out  of  the  water  and  is  connected  with  the  beak  of  the  still  is  of  cast- 
iron,  as  a  wrought  iron  piece  is  very  quickly  destroyed  at  the  point  where  the  surfaces  of 
air  and  water  come  in  contact.  In  order  to  keep  the  cooling-worm  clean,  a  steam  pipe 
is  attached  at  the  point  where  the  beak  and  the  worm  meet,  and  steam  is  blown  in  in 
case  napthaline  begins  to  be  deposited.  But  if  this  crystallisation  of  napthaline  in 
the  cooling- worm  has  made  too  much  progress  the  cooling- water  has  to  be  heated  by 
blowing  in  steam,  so  as  to  melt  the  deposit  and  open  the  way  of  issue  for  the  distillate. 
The  stills  are  filled  either  by  means  of  a  pump  or  a  montejus,  in  both  of  which  cases 
the  error  of  having  too  narrow  tubes  must  be  avoided.  For  tar  the  pipes  should  never 
be  below  130  millimetres  inside  diameter,  and  for  creosote  and  anthracene  oils  not  less 
than  80.  In  filling  the  still  with  tar  the  inflow-pipe  must  project  with  its  mouth 
beyond  the  side  of  the  still,  thus  preventing  the  tar  from  running  down  the  sides,  as 
the  plates  at  this  spot  are  quickly  corroded  by  the  sulphur-compounds  of  the  ammonia- 
water  and  the  tar.  Many  tars  are  characterised  by  an  abnormal  proportion  of  carbon, 
which  on  distiDing  attaches  itself  to  the  bottom,  and  sometimes  produces  a  considerable 
deposit  of  coke,  even  after  a  single  operation,  so  that  the  distillation  cannot  be 
completed  without  considerable  danger.  It  is  hence  advisable,  before  purchasing,  to 
distil  not  merely  a  small  quantity  of  the  tar,  but  to  shake  out  and  wash  a  small  average 
sample  with  benzol,  and  to  dry  and  weigh  the  residue.  42  Westphalian,  Ehenish,  and 
North  German  tars  gave  proportions  of  carbon  from  7  to  33  per  cent.  The  latter 

percentage  was  found  in  the  tar  of  a  large,  well-arranged  gas  works  on  the  Rhine, 
,.,,,.  ' 

which  had  in  consequence  great  difficulty  in  the  disposal  of  its  tar.  In  order  to  distil 
such  tars  without  injury  to  the  still  bottom  this  carbon  should  be  kept  in  suspension 
either  by  blowing  in  super-heated  steam,  or  by  means  of  an  agitator.  By  means  of  the 
latter  expedient  it  was  found  possible  to  effect  15  distillations,  each  of  25  tons  in 
succession,  and  to  interrupt  the  work  then  merely  to  ascertain  the  general  state  of  the 
still.  The  bottoms,  even  after  such  a  number  of  operations,  were  almost  free  from  coke, 
and  since  the  introduction  of  the  agitators  the  consumption  of  coal  had  considerably 
diminished.  The  only  disadvantage  lay  in  the  polishing  off  the  rivet-heads  in  the 


SECT,  iv.]  TREATMENT   OF   COAL-TAR.  507 

bottom,  and  wearing  out  the  chains  of  the  agitator,  so  that  after  six  months  it  was 
necessary  to  re-rivet  the  bottom  and  to  renew  the  chain.  The  bottoms  of  the  stills 
were  uninjured,  although  they  had  no  protective  vaults,  and  the  wearing  of  the  rivet- 
heads  is  avoided  if  they  are  counter-sunk.  It  was  only  possible  to  distil  highly 
carboniferous  tars  by  means  of  agitators,  and  to  work  upon  hard  pitch,  which  was 
softened  by  the  addition  of  tar-oils  of  low  value. 

The  cooler  for  pitch  is  best  made  of  masonry,  and  not  of  iron,  as  the  latter  material 
cools  too  unequally,  and  renders  a  frequent  cleansing  of  the  cooler  needful.  After 
cleaning  out  with  a  pick-axe  it  is  recommended  to  admit  steam  as  dry  as  possible. 

The  distillation  must  be  conducted  very  cautiously  at  first,  as  the  tar  is  apt  to  boil 
over  as  long  as  any  ammonia  water  is  present.  According  to  the  indications  of  the 
thermometer  in  the  still  the  following  fractions  are  separated : 

1.  First  runnings        .        .        .          up  to  105  or  1 10° 

2.  Light  oils up  to  210° 

3.  Carbolic  oils  (for  phenol  and  naphthaline),  up  to  240° 

4.  Heavy  oils      .        .        .        .        .        .     up  to  270° 

5.  Anthracene  oils above  270° 

Towards  the  end  of  the  distillation  the  condensing  water  must  be  kept  warm  to 
prevent  the  distillate  from  solidfying  in  the  cooling  pipes  and  causing  an  obstruction. 
Steam  is  often  introduced  into  the  still  for  the  same  reason,  sometimes  being  previously 
super-heated.  Lunge  obtained  as  an  average : 

First  runnings        .....  2*4  to  3*5  per  cent. 

Light  oils 6'0  to  67        „ 

Heavy  oils 30-4             „ 

Hard  pitch 55-0             „ 

According  to  Haussermann  a  tar  of  German  origin  gave : 

fractions. 

Light  oil 5-0  to  8-0  per  cent. 

Heavy  oil 25*0  to  30^0      „ 

Anthracene  oils 8go  to  io-o      „ 

Pitch 50*0  to  55-0      „ 

final  Products. 

Benzol 0*6  per  cent. 

Toluol 0*4        „ 

Higher  homologues o'5        „ 

Pure  naphthaline     ....         8'O  to  12*0        „ 

Phenol S'o  to    6'o        „ 

Anthracene 0*25  to    0*3        „ 

The  value  of  the  pitch  depends  on  its  proportion  of  oils,  determined  by  dissolving 
the  sample  in  benzol,  filtering,  washing  the  residue  (in  benzol),  and  evaporating  the 
benzol,  when  the  weight  of  the  carbon  present  is  ascertained  at  the  same  time.  Another 
method,  chiefly  followed  at  briquette  works,  for  determining  the  quality  of  soft  pitch, 
consists  in  keeping  a  fragment  of  the  sample  of  about  100  millimetres  in  length  and  10 
millimetres  in  thickness,  in  hot  water  at  60°  for  two  minutes.  The  piece  must  admit  of 
being  bent  without  cracking.  For  harder  sorts  a  temperature  of  70°  is  used.  It  serves 
for  the  manufacture  of  "  coal-blocks,"  as  an  addition  to  asphalt,  to  lacquers,  for  roofing, 
papers,  &c. 

The  treatment  of  the  heavy  oil  for  naphthaline  is  generally  not  remunerative.  It  is 
therefore  used  for  saturating  wood,  for  softening  hard  pitch,  as  a  tar  varnish,  for 
producing  blacking,  for  lighting,  or  it  is  burnt  like  tar.  The  light  oil,  the  carbolic 
oil,  and  the  anthracene  oil,  are  worked  up  specially. 


5o8 


CHEMICAL  TECHNOLOGY. 


[SECT.  rv. 


The  light  oil  (crude  naphtha)  is  first  treated  with  strong  sulphuric  acid,  and  then 
with  soda-lye,  in  order  to  remove  the  pyrogenous  resins,  defines,  &c.  Lunge  mixes  100 
kilos,  of  naphtha  with  12  kilos,  sulphuric  acid  for  ten  to  fifteen  minutes,  and  lets  the 
mixture  settle  over  night.  The  naphtha  is  then  separated  from  the  acid  (the  utilisation 
of  which  has  not  yet  been  effected),  washed  repeatedly  with  water,  treated  with  soda-lye 
of  sp.  gr.  1*1,  washed  again,  and  then  distilled.  The  crude  benzol  obtained  up  to  110° 
is  farther  purified. 

According  to  Lunge,  Fig.  389  shows  an  apparatus  used  in  English  manufactories. 
The  still,  a,  is  heated  by  the  steam-pipe,  d,  which  is  continued  in  a  spiral,  b,  of  lead  or 
wrought-iron,  with  the  pipe,  g,  for  carrying  off  the  condensed  water.  The  direct  intro- 
duction of  steam  is  effected  by  the  cock,  e,  and  the  cross  of  perforated  tubes,  f  ;  h  is  the 
feed-pipe,  i  the  outlet-cock,  k  the  capital.  In  order  to  carry  away  the  steam  the  cock, 
It  is  opened,  and  the  steam  rushes  first  into  the  spirit-catcher,  v  (which  should  never 


Fig.  389- 


be  wanting),  and  into  the  cooling-pipe,  w,  a  lead  tube  of  35  mm.  inside  diameter,  the 
end  of  which,  at  u,  returns  into  the  space  where  the  receivers  are  placed.  The  cooling- 
vat  is  fed  at  x  with  cold  water,  which  runs  off  hot  at  y.  But  if  the  vapours  are  to  be 
purified,  the  cock,  I,  is  closed  and  m  is  opened.  The  vapours  then  pass  into  the 
condenser,  n,  the  lower  drum  of  which  is  connected  with  the  upper  by  about  fifty 
copper  tubes  only  10  mm.  wide.  The  condensed  oil  runs  through  the  hydraulic 
joint,  r,  back  into  the  still. 

Heat  is  applied  at  first  by  the  closed  steam-pipe,  b,  and  afterwards  by  the  intro- 
duction of  steam  through  the  pipe,y.  In  order  to  separate  the  benzol,  which  passes 
over  first  as  free  as  possible  from  toluol,  the  vapours  arriving  through  h  are  com- 
pelled to  flow  into  n  by  closing  the  cock,  I,  and  opening  m,  whilst  the  water  of  o  is 
heated  to  a  sufficient  temperature  by  means  of  the  steam-cock,  s.  For  so-called  Qo-per 
cent,  benzol  the  water  is  kept  at  60°,  for  5o-per  cent,  benzol  at  70°  or  80° ;  but  these 
numbers  cannot  be  absolutely  fixed,  and  must  be  determined  for  every  apparatus.  The 


SECT.    IV.] 


TREATMENT  OF  COAL-TAB. 


5°9 


temperature  in  o  is  kept  as  constant  as  possible.  What  condenses  in  n  flows  back 
through  r  to  the  still  a ;  it  is  chiefly  toluol,  containing  little  benzol.  What  is  not 
liquified  in  m — i.e.,  vapours  of  benzol  containing  little  toluol — passes  into  the  main 
steam-pipe,  thence  into  the  cooling-worm,  w,  and  the  benzol  condensed  there  flows 
through  u  into  the  receiver. 

After  some  time  scarcely  anything  comes  from  u,  and  now,  in  order  to  obtain 
weaker  benzoles,  the  temperature  in  o  must  be  raised.  In  general,  even  if  it  is  desired 
to  produce  pure  toluol,  it  is  possible  to  work  with  water  in  o,  which,  however,  must  be 
heated  to  a  boil.  Water  can  the  more  readily  be  used  if  the  intention  is  to  obtain 
benzol  at  30  or  40  per  cent.,  as  is  generally  the  case.  In  most  distilleries  it  is  not 
sought  to  effect  any  further  separation  into  pure  hydrocarbons,  and  hence  purification 
is  not  carried  any  further.  If  nothing  more  runs  from  the  worm,  w,  the  condenser,  n, 
is  thrown  out  of  action  by  closing  the  cock,  m,  and  opening  I.  All  the  vapours  pass 
now  directly  to  w,  and  are  there  condensed,  so  that  there  is  again  an  abundant  distil- 
late. By  degrees  this  again  grows  less,  and  when  little  or  nothing  more  is  obtained 
the  indirect  steam  from  e  is  shut  off,  and  by  opening  d,  direct,  steam  is  allowed  to  issue 
from  the  apertures  of  the  cross-tube,/,  and  we  have  then,  even  with  steam  of  only 
2^  to  3  atmospheres,  a  plentiful  distillation  of  xyloles  and  trimethyl  benzoles,  which 
mixtures  are  either  used  as  solvent  naphtha  and  burning  naphtha,  or  are  further  worked 
up  for  xylol,  &c. 

The  distillation-apparatus  of  Coupier,  very  extensively  employed,  consists  (Fig.  390) 
of  the  body,  B,  into  which  are  introduced  the  benzoles  to  be  submitted  to  fractional 
distillation.  The  still  is  heated  by  steam  admitted  by  the  pipe,  C.  The  vapours  given 
off  from  the  boiling  liquid  arrive  in  the  column,  N,  which  acts  as  a  dephlegmater,  where 
the  first  fractiona- 

tion  occurs.     The  Fig.  390. 

most  volatile  con- 
stituents of  the 
vapours,  not  con- 
densed in  N,  ar- 
rive in  the  appara- 
tus, Z>,  filled  with 
solution  of  calcium 
chloride,  which  is 
raised  by  the 
steam-pipe,  m,  to 
a  certain  tempera- 
ture, ascertained 
by  the  thermo- 
meter, t.  The 
steam  of  the  heat- 
ing-pipe escapes 
through  P.  If 
pure  benzol  (ben- 
zene) is  to  be  obtained,  the  solution  of  calcium  chloride  is  heated  to  80°.  The 
vapours  arriving  at  G  are  a  mixture  of  benzol,  toluol,  &c.  As  the  temperature  of  G  is 
not  above  80°,  the  vapours  of  toluol  or  other  homologues,  such  as  xylol,  condense  there, 
whilst  the  vapours  not  condensable  in  G  pass  on  to  the  recipients  H,  J,  K,  depositing 
there  the  last  traces  of  the  less  volatile  hydrocarbons,  and  are  finally  condensed  in  the 
refrigerator,  L  (fed  with  cold  water),  and  are  received  in  the  flask,  M.  The  liquids 
condensed  in  G,  ff,  J,  and  K  pass  back  into  the  column,  N.  As  the  receiver,  (2,  contains 
the  heaviest  products,  they  must  be  conveyed  to  the  lowest  part  of  Jft  whilst  the 


CHEMICAL  TECHNOLOGY. 


[SECT.  IY. 


products  of  condensation  from  K  are  passed  into  the  upper  part  of  the  column.  If  it 
be  desired  to  obtain,  not  benzol  but  toluol,  the  temperature  of  the  calcium  chloride 
apparatus  must  be  raised  to  108°  to  109°. 

For  obtaining  pure  benzene  a  column  apparatus  is  used,  such  as  is  employed  in 
rectifying  spirits. 

In  English  commerce  the  following  ultimate  products  of  the  light  oils  and  the  first 
runnings  are  distinguished,  to  which  Lunge  (according  to  his  own  analysis  of  the 
products  which  he  has  himself  obtained),  appends  the  results  of  fractionation  in  volume 
percentages : — 


Commercial  names. 

Boils  at 

88° 

93°      !     100° 

IIO° 

120° 

130° 

138° 

149° 

1  60° 

171° 

90  p.c.  Benzol     . 

82° 

30 

65 

90 

— 

— 

— 









50  p.c.  Benzol    . 

88° 

— 

13 

54 

74 

90 

— 

— 

— 

— 

— 

Toluol 

I  OO° 

— 

S6 

90 

— 

— 

— 

— 

— 

Carbonating  ) 
naphtha    j 

108° 

— 

— 

—  • 

i 

35 

7i 

84 

97 

— 

— 

Solvent  naphtha. 

110° 

— 

— 

— 

— 

17 

57 

7i 

90 

— 

— 

Lamp  naphtha  . 

138° 

— 

— 

— 

— 

30 

7i-5 

89 

Fig. 


Bannow's  boiling  vessel  (Fig.  391)  for  determining  the  boiling  point  of '  benzol 
consists  of  a  globular  body  holding  200  c.c.  and  made  of  sheet  platinum,  silver,  or 
copper  of  0*7  mm.  in  thickness.  The  diameter  is  about  73  mm.  The  body  consists 

of  two  parts,  which  are  held  together  by  four  screw 
clamps,  the  joint  being  made  good  with  a  washer 
of  pasteboard,  slightly  moistened  or  oiled,  i  mm. 
in  thickness.  The  upper  part  carries  a  short  piece 
25  mm.  in  length  and  20  in  width  to  receive  the 
boiling  tube.  The  glass  boiling-tube  of  12  to  14 
mm.  outside  diameter  and  100  mm.  in  length  is 
expanded  globularly  in  the  middle ;  the  side-piece 
is  melted  on  at  about  10  mm.  above  the  globe, 
almost  at  right  angles,  and  so  as  not  to  encroach 
upon  the  clear  internal  width  of  the  tube.  The 
body  stands  upon  a  plate  of  asbestos,  with  a  circular 
aperture  of  30  mm.  in  diameter ;  the  stove  is  pro- 
vided at  10  mm.  from  its  top  edge  with  four  round 
openings  for  letting  out  the  products  of  combus- 
tion. The  source  of  heat  is  a  plain  Bunsen  burner 
with  an  aperture  of  7  mm.  in  diameter ;  the  flame 
must  burn  a  pure  blue  at  every  position  of  the 
cock.  The  Liebig's  condenser  to  be  used  is  ^ 
metre  in  length,  and  is  inclined  so  that  the  out- 
flow is  100  mm.  lower  than  the  influx.  The  ther- 
mometer has  a  scale  which  can  be  displaced  by  a 
screw,  and  must  be  made  of  thin  glass ;  the  out- 
side diameter  must  not  be  more  than  half  the 
inside  diameter  of  the  boiling  tube.  It  is  so  placed 
that  the  bulb  shall  be  in  the  middle  of  the  globe 
of  the  boiling  tube.  The  charge  consists  of  1 10  c.c. ; 

the  first  3  c.c.  passing  over  are  to  be  rejected.  The  distillation  is  so  regulated  that 
5  c.c.  pass  over  per  minute  (2  drops  per  second);  it  is  continued  until  the  graduated 
receiver  is  filled  up  to  the  mark — 100  c.c.  A  correction  for  the  height  of  the  baro- 
meter is  not  applied,  but  before  every  experiment  the  thermometer  is  adjusted  to 
the  boiling  point  of  a  standard  specimen  by  means  of  the  movable  scale.  This  is 


SECT,  iv.]  TREATMENT  OF  COAL-TAR.  511 

done  at  the  moment  when  60  c.c.  of  the  100  c.c.  of  the  type  specimen  have  distilled 
over. 

On  shaking  up  with  sulphuric  acid  of  sp.  gr.  1*845  the  benzol  must  not  be 
discoloured  at  all  and  the  acid  not  immediately.  In  ten  minutes  it  may  turn  slightly 
yellow.  If  poured  into  nitric  acid  at  72°  Tw.  no  white  vapours  must  be  produced,  and 
on  shaking  the  benzol  must  not  be  coloured.  On  prolonged  standing  the  nitric  acid 
turns  slightly  reddish;  afterwards  it  becomes  colourless  and  the  redness  passes  to 
the  benzol. 

Benzene. — The  pure  substance  C6H6  boils  at  80°  and  solidifies  at  o°  •  sp.  gr.  at  o*  = 
0-8991 ;  at  15°  =  o'884i.  It  is  slightly  soluble  in  water,  easily  soluble  in  alcohol,  ether 
and  methyl-alcohol.  Common  coal-tar  benzol  contains  generally  thiophene,  C4H4S, 
and  carbon  disulphide. 

Toluol  (called  toluene  when  absolutely  pure)  a  benzyl-benzol  C7H8  or  06H5.CH8, 
boils  at  1 10° ;  its  sp.  gr.  at  15*  =  0-872.  It  is  also  obtained  from  wood-tar. 

Xylol  or  dimethyl-benzol  from  coal  tar  C8H10  =  C6H4(CHS),  boils  at  138°  to  140°. 

The  light  oil,  containing  some  benzol,  much  toluol  and  its  higher  homologues, 
phenoles,  naphthaline  and  liquid  oils  is  rectified.  The  fraction  up  to  120°  is  added  to 
the  corresponding  fraction  of  the  first  runnings  (of  the  main  distillate  up  to  150°).  The 
fraction  from  150°  to  190°  is  purified  with  acid  and  alkaline  lye,  and  is  then  taken  to  a 
second  rectification.  The  residue  (above  190°)  goes  to  the  heavy  oils.  The  second 
rectification  of  the  chemically  purified  fraction  120°  to  190°  gives  : — 

(a)  Product  up  to  120°  contains  benzol  and  toluol,  and  comes  to  the  corresponding 
product  from  the  first  runnings. 

(b)  Product  from  120°  to  127°  gives  benzene  No.  i.  for  taking  out  spots. 

(c)  Product  from  127°  to  140°  gives  benzene  No.  2. 

(d)  Product  from  140°  to  150°  gives  benzene  No.  3. 

(e)  Residue  comes  to  the  heavy  oil. 

For  obtaining  phenol  it  is  advantageous  not  to  work  up  all  the  light  oil,  but  to 
take  the  portion  which  passes  over  last,  the  so-called  carbol-oil,  which  has  in  general 
the  sp.  gr.  0-99  to  1-005.  It  is  treated  with  soda  lye,  which  dissolves  the  phenoles, 
(tar-acids),  whilst  the  oil  not  soluble  in  soda  is  worked  up  for  naphthaline.  The  solution 
of  sodium  carbolate  is  decomposed  by  the  addition  of  sulphuric  acid,  or,  better,  by  passing 
into  it  carbonic  acid. 

The  crude  carbolic  acid  thus  obtained  contains  only  about  50  per  cent,  phenol  with 
water,  creosotes,  naphthaline,  &c.  It  is  purified  by  redistillation,  and  the  part  passing 
over  between  175°  to  200°  is  set  in  a  cool  place  to  crystallise.  Or  the  crude  carbolic 
acid  is  treated  with  i  per  cent,  potassium  dichromate  and  the  quantity  of  sulphuric  acid 
at  1*845  sp.  gr.  necessary  for  its  decomposition,  stirring  constantly.  This  is  done  in  a 
fiat  vessel,  so  that  the  carbolic  acid  may  present  the  greatest  possible  surface  to  the  air ; 
the  sulphuric  acid  is  added  first,  and  then  the  solution  of  the  dichromate,  and  the  whole 
is  stirred  for  some  hours,  being  placed  if  possible  in  a  place  exposed  to  the  sun.  The  con- 
tents of  the  flat  pan  are  then  drawn  off  into  a  deep  glass  jar,  allowed  to  settle,  and  the  oil 
is  drawn  off  and  distilled  between  1 70°  to  198°,  whilst  the  first  runnings  of  this  distillation 
are  added  to  the  next  distillation  of  crude  oil,  and  the  residue  in  the  still  is  again  distilled 
with  the  crude  tar.  The  fraction  passing  over  between  170°  and  198°  is  again  treated 
in  a  flat  vessel  with  i  per  cent,  potassium  dichromate,  and  a  corresponding  quantity  of 
«trong  sulphuric  acid,  stirred  for  some  hours,  drawn  off  from  the  dregs  and  distilled  in 
a  small  column  apparatus.  The  distillate  is  collected  in  small  half -litre  bottles  until  the 
contents  of  the  still  begin  to  become  thick,  which  is  found  by  stirring  with  an  iron  rod. 
The  bottles  are  at  once  well  closed,  and  let  stand  to  crystallise,  the  oil  is  poured  off  from 
the  crystals,  which  are  melted  in  the  water  bath,  and  collected  in  dry  £  litre  glass 
bottles. 


512 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


Phenol  (carbolic  acid),  C6H5OH,  melts  at  42°  and  boils  at  182°.  It  dissolves  in  20 
parts  of  water,  but  at  any  proportion  in  alcohol,  ether  and  benzene.  Phenol  is  poisonous, 
but  it  is  a  good  disinfectant.  The  cause  of  its  turning  red  has  not  been  ascertained 
with  certainty. 

The  quantitative  determination  of  phenol  is  effected  volumetrically  with  bromine. 
It  is  used  in  preparing  colours,  explosives  (picrates)  and  as  a  disinfectant. 

Cresol,  or  the  cresylic  acid  of  coal-tar,  C7H8O  or  C6H4.CH3OH,  boils  at  190°  to  203°, 
and  is  a  variable  mixture  of  metacresol,  orthocresol,  and  paracresol. 

The  oil  drawn  off  from  sodium  carbolate  is  first  re-distilled,  and  then  set  in  a  cold 
place,  the  naphthaline  which  crystallises  out  is  pressed  and  once  more  distilled.  This 
distilled  naphthaline,  in  order  to  remove  the  pyrogenous  resins,  is  melted  in  a  double  iron 
pan  lined  with  lead,  along  with  i  per  cent,  of  sulphuric  acid  at  156°  Tw.,  and  stirred 
for  some  hours.  After  prolonged  settling,  the  sulphuric  acid  is  separated  from  the 
naphthaline  and  the  latter  is  sublimed  in  an  upright  still  over  an  open  fire.  Into  the 
naphthaline  there  opens  a  pipe  for  the  direct  admission  of  steam,  and  in  the  capital  of 
the  still  a  pipe  which  introduces  steam  from  a  fine  aperture.  As  soon  as  the  ther- 
mometer plunging  into  the  naphthaline  marks  160°,  dry  steam  is  let  in  very  gently 
from  both  pipes.  The  beak  of  the  still  opens  into  the  sublimation  building,  consisting 
of  an  antechamber  and  a  main  chamber  1 2  metres  long,  3  metres  high,  and  2  metres 
in  breadth.  The  liquid  naphthaline  passing  over  collects  in  the  antechamber,  which  is 
3  metres  in  length. 

According  to  another  communication  there  is  used  a  subliming  chamber,  A  (Fig.  392), 
5  metres  long  and  3  metres  wide.  The  wrought-iron  pan,  B,  3  metres  long  and  i  metre 

broad,  is  built  in  so  over 

392-  the  grated  arch,  C,  that 

the  fire-gases  from  the 
heating-room  pass  back- 
wards through  D,  below 
the  grated  arch,  rise  up 
in  the  flues,  E  E,  leading 
round  the  subliming 
pan,  B,  and  escape  at 
the  chimney.  The  door, 
F,  which  turns  on  an 
axle,  G,  is  luted  up 
with  clay  during  the  sub- 
limation. Two  wooden 
covers,  H,  coated  with 
sheet-iron  placed  above 

the  pan,  rest  upon  iron  clasps  which  are  secured  in  the  two  side  walls,  cutting  off  the 
door,  F.  These  two  doors  act  like  the  dephlegmators  in  distillation,  as  vapours  of  the 
heavier,  less  volatile  tar  oils,  carried  along  by  the  vapours  of  the  naphthaline  condense 
here  on  their  surfaces  and  flow  back  into  the  pan.  The  wooden  door,  J,  also  lined 
with  sheet-iron,  can  be  removed  on  cleaning  the  naphthaline  out  of  the  chamber.  To 
the  iron  air-pipe,  L,  8  centimetres  in  thickness,  there  hangs  the  dish,  M,  which  serves 
to  catch  the  water  condensed  in  the  air-pipe.  The  pan  is  filled  with  crude  naphthaline 
and  from  3  to  4  per  cent,  of  slaked  lime  is  added ;  the  doors  are  then  luted  up  with 
clay,  and  at  first  a  strong  fire  is  kept  up,  but  as  soon  as  the  sublimation  begins  it  is 
kept  very  slight  and  uniform.  In  the  door,  F,  there  is  a  small  hole  so  that  the  depth 
and  the  quality  of  the  naphthaline  remaining  in  the  pan  can  be  tested  with  an  iron  rod. 
The  hole,  of  course,  is  closed  with  a  cork.  In  two-and-a-half  to  three  days,  if  the  heat 
has  been  maintained  all  day,  the  pan  will  be  empty  down  to  6  to  8  centimetres.  It  is 


SECT,  iv.]  TREATMENT  OF  COAL-TAR.  513 

now  frequently  tested  with  the  iron  rod,  and  when  it  is  seen  that  the  naphthaline  no 
longer  congeals  upon  the  iron  the  heating  is  stopped,  because  merely  heavy  tar  oils 
remain  in  the  pan.  The  pan  is  then  emptied,  charged  afresh,  and  the  sublimation  is 
continued.  When  two  or  three  pans  have  thus  been  worked  off  the  sublimed  naph- 
thaline is  cleared  out  of  the  chamber.  It  is  melted  in  an  open  cast-iron  pan  with  an 
emptying  spout,  and  mixed  with  a  20  per  cent,  lye  at  27°  Tw.,  the  lye  is  let  off  and 
there  is  added  to  the  liquid  naphthaline  6  per  cent,  of  sulphuric  acid  at  156°  Tw., 
and  a  little  pyrolusite.  After  stirring  diligently  for  fifteen  or  thirty  minutes,  according 
to  the  size  of  the  pan,  the  naphthaline  is  allowed  to  settle,  and  in  an  hour  the  acid  is 
drawn  off.  The  naphthaline  is  then  twice  washed  with  hot  water  to  remove  any 
traces  of  acid,  and  once  more  sublimed. 

Naphthaline,  C10H8,  forms  thin,  white,  rhombic  leaflets  of  a  peculiar  odour  some- 
what like  that  of  storax,  and  of  a  burning  taste.  After  fusion  and  solidification  it  appears 
as  dazzling  white  crystalline  masses  of  sp.  gr.  ri5i.  It  melts  at  79°  and  boils  at 
216°  to  218°.  It  is  insoluble  in  cold  water,  very  slightly  soluble  in  hot  water,  easily 
soluble  in  boiling  alcohol,  benzol,  in  the  volatile  and  the  fatty  oils,  and  in  acetic  acid. 

Anthracene  oil  when  cold  forms  a  greenish-yellow  mass,  of  a  buttery  consistence, 
consisting,  besides  oils  of  high  boiling  points,  of  naphthaline,  methylnaphthaline,  anthra- 
cene, phenanthrene,  acenaphthine,  diphenyl,  methylanthracene,  pyrene,  chrysene,  retene, 
fluorene,  acridine,  &c.  The  anthracene  oil  is  let  cool,  when  crude  anthracene  crystal- 
lises out  and  is  separated  from  the  oils  in  a  filter-press.  This  28  per  cent,  crude 
anthracene  is  dissolved  by  heat  (in  a  double  pan,  arranged  for  steam-heating  and  water- 
cooling  and  fitted  with  an  agitator)  in  120  per  cent,  creosote  oil,  from  which  the 
phenols  have  been  removed  by  treatment  with  soda-lye.  This  creosote  oil,  boiling  at 
220°  to  320°  is  very  suitable  for  removing  paraffine  from  anthracene.  The  solution  of 
paraffine  is  stirred  until  cold  with  water  refrigeration  and  is  then  forced  through  a 
filter-press.  The  product  so  obtained  contains  36  to  40  per  cent,  of  actual  anthracene. 
If  it  has  to  be  brought  to  a  higher  grade  this  can  be  effected  by  a  repeated  washing  in 
tar  oils,  but  in  this  manner  much  anthracene  is  dissolved.  A  pure  product  is  obtained 
by  distilling  the  36  per  cent,  anthracene  with  caustic  potassa  at  30  per  cent.  The 
anthracene  is  distilled  in  horizontal  cylinders  of  wrought-iron  or  cast-iron,  1-2  metre 
in  diameter,  2*2  metres  long,  and  containing  about  26  hectolitres.  The  fire-gases  pass 
through  two  channels  at  the  bottom  of  the  cylinder,  which  is  protected  against  the 
direct  action  of  the  flame  by  fire-proof  plates,  and  pass  then  along  its  sides.  The 
distillate  runs  through  an  air-cooler  into  iron  pans,  in  which  the  anthracene  (now  48 
per  cent.)  crystallises.  The  residue  in  the  cylinder,  containing  carbazol  and  potassa,  as 
it  is  spontaneously  inflammable  in  contact  with  air,  is  immediately  after  distillation 
drawn  off  into  iron  chests,  allowed  to  cool  and  burnt  on  an  open  grate  in  a  furnace  for 
crude  potash.  Here  a  flue-dust  chamber  must  be  arranged  between  the  chimney  and  the 
exit  channel  in  order  not  to  let  the  fine  dust  of  potash  escape  into  the  air.  The  loss  of 
anthracene  in  this  purification  with  caustic  potassa  is,  in  good  kinds,  2  per  cent.,  but 
in  inferior  sorts  as  much  as  12  per  cent.  If  a  high-grade  anthracene  is  required,  this 
anthracene  distilled  over  potassa  can  be  easily  brought  up  to  70  per  cent,  by  dissolving 
it  in  140  per  cent,  of  heavy  benzol,  boiling  at  140°  to  170°,  stirring  till  cold,  pressing 
and  recovering  the  heavy  benzol  which  adheres  to  it  by  heating  with  indirect  steam. 
The  total  loss  in  heavy  benzol  in  large  works,  properly  arranged,  is  z\  per  cent. 
Instead  of  heavy  benzol,  creosote  oil  washed  in  soda  lye  may  be  used,  and  after 
hydraulic  pressure  the  residual  creosote  oil  may  be  removed  by  direct  steam  entering 
through  a  perforated  false  bottom.  After  the  anthracene  has  been  washed  the  heavy 
benzol  contains  large  quantities  of  phenanthrene  and  heavy  oils,  as  well  as  of  dissolved 
anthracene,  from  which  the  benzol  is  separated  by  direct  and  indirect  steam.  The 
crude  phenanthrene  and  the  oils  running  off  on  hydraulic  pressure  contain  up  to  8  per 

2  K 


5i4  CHEMICAL  TECHNOLOGY.  [SECT  iv. 

cent,  of  anthracene.  From  phenanthrene  it  is  extracted  by  adding  to  the  distilled 
anthracene,  during  the  purification  with  benzine,  about  20  per  cent,  of  phenanthrene. 
From  the  press-oils  the  anthracene  may  be  advantageously  recovered  by  fractional 
crystallisation  during  the  winter. 

Anthracene,  C14H10,  melts  at  210°  to  213°,  and  boils  at  360°.  It  is  insoluble  in  water, 
slightly  soluble  in  alcohol,  ether,  and  benzol,  but  more  freely  in  toluol* 

Organic  Colouring  Matters. — Up  to  the  middle  of  the  present  century,  organic 
colouring  matters  were  obtained  solely  from  plants  and  from  a  few  animals  (cochineal, 
&c.)  With  the  discovery  of  aniline  violet  in  1856  by  Perkins,  tar-colours  were  added 
to  those  from  natural  sources.  These  artificial  products  have  superseded  to  some 
extent  several  of  the  natural  colours,  alizarine,  the  colouring  principle  of  madder,  being 
now  almost  exclusively  obtained  from  coal-tar. 

Red  Colours. — Madder. — Madder  is  the  root  of  the  Rubia  tinctorum,  a  perennial 
plant  cultivated  in  Southern,  Central,  and  Western  Europe  ;  while  in  the  Levant  the 
R.  peregrina,  and  in  the  East  Indies  and  Japan  the  R.  mungista  (mungeet),  are  partly 
cultivated,  partly  met  with  in  the  wild  state.  According  to  researches  made  in 
England,  the  dye  imported  under  the  name  of  mungeet  from  India  is  not  the  root, 
but  the  reedy  stem  of  a  species  of  Rubia,  and  as  a  dye  it  is  inferior.  The  native 
country  of  the  madder  plant  is  the  Caucasus.  All  these  plants  are  perennial.  The 
root  varies  in  length  from  10  to  25  centimetres ;  it  is  not  much  gnarled,  and  is  gene- 
rally a  little  thicker  than  the  quill  of  a  pen.  Externally  the  root  is  covered  with 
a  brown  bark ;  internally  it  exhibits  a  yellow  red  colour.  Madder  is  met  with  in  the 
trade  as  the  root  (technically  ratine,  if  European),  and  in  powder  exhibiting  a  red- 
yellow  colour-,  and  possessing  a  peculiar  odour.  Avignon  madder,  however,  has  hardly 
any  smell ;  but  the  odour  is  particularly  marked  in  Zeeland,  or  so-called  Holland, 
madder.  The  powdered  madder  is  always  kept  in  strong  oaken  casks,  so  as  to 
exclude  air  and  light.  The  best  kind  of  madder  is  that  grown  in  the  Levant  (Smyrna 
and  Cyprus),  and  met  with  in  the  trade  under  the  name  of  lizari  or  alizari,  in 
roots,  which  are  usually  rather  thicker  than  the  roots  of  the  European  varieties,  owing 
partly  to  the  fact  that  the  Levant  madder  is  generally  of  four  to  five  years'  growth, 
while  in  Europe  the  roots  are  of  two  to  three  years'  growth  only.  Dutch  madder, 
chiefly  grown  in  the  province  of  Zeeland,  is  met  with  decorticated  (robe),  the  outer  bark 
and  sometimes  the  splint  bark  having  been  removed.  The  well-dried  roots  are 
broken  up  by  means  of  wooden  stampers  moved  by  machinery,  to  reduce  the  bark  and 
splint  bark  to  powder,  while  the  very  hard  internal  portion  of  the  root  is  left  untouched, 
this  being  separated  from  the  powder  by  means  of  sieves.  The  powder  is  put  into 
casks  and  termed  beroofde.  During  the  last  ten  or  twelve  years  the  old  madder  sheds 
(meestoven)  in  Zeeland  have  been  superseded  by  large  manufactories,  in  which  the 
madder  root  is  treated  as  it  is  in  the  Vaucluse  (France),  and  ground  up  entirely,  so- 
that  the  former  distinct  qualities  of  madder  are  no  longer  met  with.  When  the 
whole  root  is  pulverised  the  madder  is  termed  onberoofde,  non  robe.  Besides  the  Dutch 
madder,  that  from  Alsace  and  from  the  "Vaucluse,  Avignon,  occurs  very  largely  in  the 
trade.  What  is  known  as  mull  madder  is  the  refuse  and  dust  from  the  floors  of  the 
works,  and  is  the  worst  quality.  In  addition  to  colouring  matter,  madder  contains  a 
large  quantity  of  sugar,  of  which  W.  Stein  (1869)  found  as  much  as  8  per  cent.  While 
it  was  formerly  considered  that  madder  contained  no  less  than  five  different  colouring 
substances,  it  appears  from  recent  researches  that  this  root  in  the  fresh  state  only  con- 
tains two  pigments,  viz.,  ruberythrinic  acid  (formerly  termed  xanthin)  and  purpurine. 
According  to  Dr.  Rochleder,  the  former  of  these  is  converted  under  the  influence  of 

*  For  further  particulars  on  the  primary  coal-tar  products  the  reader  may  consult  G.  Lunge, 
Coal-Tar  and  Ammonia,  Gurney  &  Jackson,  London;  and  Anthracene,  its  Properties,  &c,,  by 
G.  Auerbach,  edited  by  W.  Crookes,  F.R.S.,  &c. :  Longmans,  London. 


SECT,  iv.]  TREATMENT  OF  COAL-TAR.  51$ 

a  peculiar   nitrogenous  substance   present  in  the   madder  root    into  alizarine — the 
essential  colouring  matter  of  madder — and  into  sugar : — 

C^H^  +  2H20  =  CMH,04  +  20^0P 

Ruberythrinic  Alizarine.  Sugar, 

acid. 

According  to  the  researches  of  Graebe  and  Liebermann,  alizarine  is  a  derivative 
from  anthracen,  C14H10,  the  formula  of  the  former  being  C14H8O4.  As  elsewhere  mentioned 
the  same  chemists  have  succeeded  in  converting  anthracen  into  alizarine  (169). 
Alizarine  is  yellow,  but  becomes  red  under  the  influence  of  alkalies  and  alkaline  earths. 
Madder  contains  a  red  pigment,  purpurine,  or  rubiacine,  C14Hg05,  which  by  itself,  as 
well  as  in  combination  with  alizarine,  yields  a  good  dye.* 

Madder  Lake. — We  understand  by  this  term  a  combination  of  alizarine  and  pur- 
purine (the  colouring  matter  of  madder)  with  basic  aluminium  salts.  Madder  lake  is 
prepared  by  first  washing  madder  with  water,  distilled,  or  at  least  free  from  lime  salts, 
next  exhausting  the  dye-stuff"  with  a  solution  of  alum,  the  liquor  thus  obtained  being 
precipitated  with  sodium  carbonate  or  borax.  The  bulky  precipitate,  having  been 
collected  on  a  filter,  is  thoroughly  washed  and  dried. 

Flowers  of  Madder. — The  preparation  made  from  madder  on  the  large  scale,  and 
known  in  the  trade  as  flowers  of  madder  (fleur  de  garance),  is  obtained  from  the 
pulverised  madder  by  steeping  it  in  water,  inducing  fermentation  of  the  sugar  con- 
tained in  it,  and  next  thoroughly  washing  the  residue,  first  with  warm,  next  with 
cold  water.  The  residue,  after  subjection  to  hydraulic  pressure  to  remove  the- 
water,  is  dried  at  a  gentle  heat,  and  having  been  pulverised  again,  is  used  in  the 
same  manner  as  madder  for  dyeing  purposes.  The  operation  of  dyeing  with 
the  flowers  of  madder  requires  a  less  elevated  temperature  of  the  contents 
of  the  dye-beck.  It  would  appear  that  by  the  preparation  of  the  flowers  of  madder 
the  pectine  substances  of  the  root  are  eliminated,  which  otherwise  become  insoluble 
during  the  operation  of  dyeing. 

Azak. — When  flowers  of  madder  are  treated  with  boiling  methylic  alcohol  (wood- 
spirit),  the  solution  obtained  filtered,  and  water  added  to  the  filtrate,  a  copious  yellow 
precipitate  is  obtained,  which  having  been  washed  with  water  and  dried  constitutes  the 
material  known  as  azale  (from  azala,  Arabian  for  madder),  which  has  been  suggested  for 
use  as  a  dye  material  in  France.  Probably  this  substance  is  crude  alizarine ;  as  obtained 
from  madder  or  garancine,  it  is  sometimes  met  with  in  the  trade  under  the  name  of 
Pincoffine,  having  been  first  discovered  and  prepared  by  Mr.  PincofFs  at  Manchester. 

Garancine. — This  preparation  of  madder  contains  the  colouring  principles  of  the  root 
in  a  more  concentrated,  pure,  and  more  readily  exhaustible  state.  In  order  to  pre- 
pare garancine,  madder  (generally  this  term  is  given  to  the  pulverised  root)  is  first 
moistened  uniformly  with  water,  and  next  there  is  added  £  part  of  sulphuric  acid 
diluted  with  i  part  of  water.  This  mixture  is  heated  by  means  of  steam  to  about  100° 
for  one  hour,  and  the  magma  then  thoroughly  washed  with  water  for  the  purpose  of 
eliminating  all  the  acid.  This  having  been  done,  the  garancine  is  submitted  to  hydraulic 
pressure  for  the  purpose  of  getting  rid  of  the  greater  part  of  the  water,  after  which  the 
material  is  dried  and  lastly  ground  to  a  very  fine  powder.  By  the  action  of  the  sulphuric 
acid  some  of  the  substances  contained  in  madder,  and  more  or  less  interfering  with  its 
application  as  a  dye,  are  eliminated  in  the  washing  of  the  garancine,  while  the  colouring 
matter  remains  mixed  with  the  partly  carbonised  organic  substances.  As  regards  its 
tinctorial  value  i  part  of  garancine  may  be  taken  as  equal  to  3  to  4  parts  of  madder. 

Garanceux. — As  madder  when  employed  in  dyeing  does  not  become  quite  exhausted, 
the  fluids  of  the  dye-beck  are  strained  from  the  solid  residue,  and  this  is  treated  with  half 
*  Mungistine,  C16HS06,  is  found  in  madder  from  India  (rnunjeet),  and  dyes  like  alizarine. 


5i6  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

of  its  weight  of  sulphuric  acid.  The  mass  is  next  treated  as  has  been  described  under 
garancine,  and  constitutes  after  drying  what  is  known  as  garanceux,  being  used  generally 
for  the  production  of  what  are  termed  sad  colours  (black,  deep  brown,  lilac).  As  a 
matter  of  course  garanceux  is  of  less  tinctorial  value  than  garancine. 

Colorine. — The  substance  met  with  in  commerce  under  the  name  of  colorine  is  the 
dry  alcoholic  extract  of  garancine,  and  consists  essentially  of  alizarine,  purpurine,  fatty 
matter,  and  other  substances  soluble  in  alcohol  present  in  garancine.  E.  Kopp  com- 
menced some  years  since  to  exhaust  madder  with  an  aqueous  solution  of  sulphurous 
acid,  thereby  obtaining  the  pigments  of  madder  in  a  (for  technical  purposes)  pure  con- 
dition. These  preparations,  which  are  already  extensively  used,  are  distinguished  as  : 
Green  alizarine  (Alizarine  verte),  which  from  Alsace  madder  is  obtained  to  an  amount 
of  about  3  per  cent.,  containing  with  the  alizarine  a  green  resinous  material ;  yellow 
alizarine  (Alizarine  jaune),  the  former  substance  without  the  resinous  material,  this 
having  been  "eliminated  by  suitable  solvents,  as  purpurine  and  flowers  of  madder. 
The  tinctorial  value  of  purpurine  amounts  to  10  times  and  that  of  the  green  and 
yellow  alizarine  to  32  to  36  times  that  of  madder.  Madder  of  good  quality  yields  on 
the  large  scale  — * 

Purpurine     .        .        .        .        .        .       1-15  per  cent. 

Green  alizarine 2*50        „ 

Yellow  alizarine 0-32        „ 

Flowers  of  madder       .        .        .        .     39*00        „ 

Safflower. — The  drug  to  which  this  name  is  given  consists  of  the  dried  petals  of  the 
flowers  of  the  Carthamus  tinctorius,  a  thistle-like  plant  belonging  to  the  family  of  the 
Synantherece,  a  native  of  India,  and  cultivated  in  Egypt,  the  southern  parts  of  Europe, 
and  also  to  some  extent  in  parts  of  Germany.  Saffiower  contains  a  red  matter, 
carthamine,  insoluble  in  water,  and  also  a  yellow  substance  soluble  in  that  liquid. 
The  quality  of  this  drug  is  better  according  to  its  greater  purity  from  mechanical 
admixtures,  such  as  seeds,  leaves  of  the  plant,  &c.  Carthamine,  C14H16O7,  or  Rouge  vegetal, 
is  prepared  in  the  following  manner : — The  safflower  is  exhausted  with  a  very  weak 
solution  of  sodium  carbonate,  and  in  this  fluid  strips  of  cotton-wool  are  dipped,  after 
which  the  strips  are  immersed  in  vinegar  or  very  dilute  sulphuric  acid  for  the  purpose 
of  neutralising  the  alkali.  The  red-dyed  cotton  strips  are  next  washed  in  a  weak 
solution  of  sodium  carbonate,  and  the  solution  thus  obtained  is  precipitated  with  an 
acid;  the  carthamine  thrown  down  is  first  carefully  washed,  and  next  placed  on 
porcelain  plates  for  the  purpose  of  becoming  dry.  Carthamine  when  seen  in  thin  films 
exhibits  a  gold-green  hue,  while  when  seen  against  the  light  the  colour  is  red.  When 
carthamine  has  been  repeatedly  dissolved  and  precipitated  it  is  termed  safflower- 
carmine.  Mixed  with  French  chalk  (a  magnesium  silicate),  carthamine  is  used  as  a 
face  powder.  Safflower  is  used  for  dyeing  silk,  but  the  red  colour  imparted  is,  although 
brilliant,  very  fugitive. 

Carthamine  is  used  for  red  tape,  as  the  exact  shade  preferred  by  consumers  has 
not  been  obtained  from  coal-tar  colours. 

Cochineal,  or  Cochenille. — This  substance  is  the  female  insect  of  the  Coccus  cacti 
found  on  several  species  of  cacti,  more  especially  on  the  Nopal  plant  and  the  Cactus 
opuntia.  This  insect  and  the  plants  it  feeds  on  are  purposely  cultivated  in  Mexico, 
Central  America,  Java,  Algeria,  the  Cape,  &c.  The  male  insect,  of  no  value  as  a  dye 
material,  is  winged,  the  female  wingless.  The  female  insects  are  collected  twice  a  year 
after  they  have  been  fecundated  and  have  laid  eggs  for  the  reproduction  of  young,  and 
are  killed  either  by  the  aid  of  the  vapours  of  boiling  water  or  more  usually  by  the  heat 
of  a  baker's  oven.  Two  varieties  of  cochineal  are  known  in  commerce,  viz.,  the  fine 
cochineal  or  mestica,  chiefly  gathered  in  the  district  of  Mestek,  a  province  of  Honduras, 
on  the  Nopal  plants  there  cultivated  ;  and  the  wild  cochineal,  gathered  from  cactus 

*  Since  the  introduction  of  artificial  alizarine  the  cultivation  of  madder  has  been  almost 
abandoned. 


SECT,  iv.]  TREATMENT  OF  COAL-TAR.  517 

plants  which  grow  in  the  wild  state.  This  latter  variety  is  of  inferior  quality. 
Cochineal  appears  as  small  deep  brown-red  grains,  at  the  lower  and  rather  flattened 
side  of  which  the  structure  of  the  insects  is  somewhat  discernible.  Sometimes  the 
dried  insect  is  covered  with  a  white  dust,  but  frequently  the  material  is  met  with 
exhibiting  a  glossy  appearance  and  black  colour.  The  white  dust,  very  frequently 
fraudulently  imparted  by  placing  the  grain  with  French  chalk  or  white-lead  in  a  bag, 
is,  according  to  the  results  of  microscopical  investigation,  the  excrement  of  the  insect, 
exhibiting  when  seen  under  the  microscope  the  shape  of  curved  cylinders  of  very 
uniform  diameter  and  a  white  colour.  Cochineal  contains  a  peculiar  kind  of  acid  — 
carminic  acid  —  which,  by  the  action  of  very  dilute  sulphuric  acid  and  other  reagents,  is 
split  up  into  carmine-red  (carmine)  —  also  present  in  the  insect,  together  with  the  acid 
—  and  into  dextrose  — 


Carminic  Carmine-        Dextrose. 

acid.  red. 

What  is  commonly  termed  carmine  is  prepared  by  exhausting  the  cochineal  with 
boiling  water  ;  to  the  decanted  clear  fluid  alum  is  added,  after  which  it  is  allowed  to 
settle.  By  another  method  carmine  is  prepared  by  exhausting  the  pulverised  cochinea 
with  a  solution  of  sodium  carbonate  ;  white  of  egg  is  next  added  to  this  solution  for  the 
purpose  of  clarifying  it,  and  afterwards  the  solution  is  precipitated  with  an  acid.  In 
either  case  the  washed  precipitate  is  next  diied  at  30°.  So  prepared,  a  finer  and  better 
kind  of  carmine  is  obtained,  but  the  common  carmine  —  carmine  lake  and  round  lake  —  is 
prepared  by  treating  an  aluminous  solution  of  cochineal  with  sodium  carbonate  ;  the 
larger  the  quantity  of  alumina  contained  in  these  preparations,  the  coarser  the  quality. 

Lac  Dye.  —  This  dye-stuff  is  obtained  from  a  resinous  substance,  stick  or  grain  lac, 
or  gum  resin,  and  is  derived  from  a  variety  of  the  cochineal  insect  in  the  following 
manner  :  —  The  Coccus  laccce,  a  native  of  India,  pierces  the  branches  of  certain  kinds  of 
fig-trees,  from  which  a  milky  juice  exudes,  which,  while  becoming  inspissated,  encloses 
the  insects,  and  at  last  forms  a  hard  resinous  mass  tinged  with  the  dye-stuff  contained 
in  the  insects.  This  pigment  is  extracted  from  the  resinous  matter  by  means  of  a 
solution  of  sodium  carbonate,  and  the  solution  obtained  is  precipitated  by  alum  solution. 
The  lac  dye  is  not  very  different  from  cochineal. 

Lac  shades  are  somewhat  more  permanent  than  those  obtained  from  cochineal,  as 
the  carminic  acid  is  accompanied  by  resinous  matter. 

Tyrian  Purple.  —  The  secretion  of  the  purple  snail,  which  on  exposure  to  sunlight 
forms  the  "  purple  "  of  antiquity,  is  not  now  an  article  of  commerce. 

Weed  Colours.  —  By  orchil,  or  archil  and  cudbear  (called  persio  on  the  Continent), 
we  designate  red  dyes  which  are  met  with  in  commerce  in  pasty  masses.  Orchil  is 
prepared  from  several  kinds  of  sea-weed,  Roccella  tinctoria,R.fuciformis,R.  Montagnei, 
Usnea  barbata,  Usnea  florida,  Lecanora  parella,  Unceolaria  scruposa,  Ramalina  calicaris, 
Gyrophora  pustulata,  and  others,  which  having  been  well  dried,  are  first  ground  to  a 
very  fine  powder.  This  is  mixed  with  ammonia  and  left  to  enter  into  putrefactive 
fermentation.  The  ammonium  carbonate*  acting  upon  the  peculiar  acids  —  lecanoric, 
alpha-  and  beta-orcellic,  erythrinic,  gyrophoric,  evernic,  usninic,  &c.  —  contained 
in  these  sea-weeds,  converts  these  non-nitrogenous  substances  into  orcine,  C7H80,, 
this  reaction  being  accompanied  by  the  elimination  of  water,  and  usually  also 
with  the  elimination  of  carbonic  acid.  By  taking  up  nitrogen  and  oxygen  orcine 
is  converted  into  orceine,  C7H7NO,,  constituting  the  essential  colouring  matter  of 
orchil.  This  substance  appears  as  a  red  paste,  exhaling  a  peculiar  violet  odour 
(viola  odorata)  and  having  an  alkaline  taste.  Before  the  coal-tar  colours  were 
discovered  this  dye  material  was  prepared  chiefly  in  England  and  France  from 

*  Stale  urine,  or  '«»/,  was  formerly  used  instead  of  solution  of  ammonia. 


St8  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

weeds  collected  on  the  Pyrenees,  or  imported  from  the  Canary  Islands,  or  from 
Lima  and  Valparaiso.  Cudbear,  or  red-indigo,  is  much  the  same  kind  of  product 
as  orchil,  from  which  it  differs  mainly  in  being  freed  from  all  excess  of  ammonia 
and  from  moisture,  and  in  being  reduced  to  a  fine  powder;  it  was  formerly 
prepared  in  Scotland  from  sea-weeds  found  on  the  coast.  At  a  later  period  it  was 
made  in  large  quantity  in  Germany,  in  France,  and  in  England.  Persio  was  a  red 
yiolet  powder.  Some  ten  years  ago  two  preparations  of  orchil  were  brought  into 
commerce  under  the  names  of  orchil  carmine  and  orchil  purple  (pourpre  Francois). 
-These  substances  contained  the  orchil  dyes  in  a  very  pure  condition.  Since  the  tar- 
colours  have  made  their  appearance  the  dyes  obtained  from  the  sea-weeds,  very 
beautiful  but  very  perishable  colours,  have  in  a  great  measure  become  obsolete". 

Less  Important  Red  Dyes. — Among  the  less  important  red  dyes  and  colouring 
matters  are  the  alkanet  root  (Anchusa  tinctoria) ;  dragon's  blood,  a  red-coloured  resin 
from  Dracaena  draco ;  harmala  red  from  the  seeds  of  the  Peganum  harmala,  a  plant 
growing  in  the  Steppes  of  Russia ;  chica  red,  or  carajura,  from  the  leaves  of  the 
Bignonia  chica,  a  tree  growing  in  "Venezuela ;  purple-carmine,  or  murexide,  obtained 
from  uric  acid  by  treating  it  with  oxidising  substances  (nitric  acid  for  instance)  and 
next  with  ammonia. 

Murexide  produces  reds  and  purples  equal  to  the  aniline  dyes,  but  it  is  more 
expensive,  and  the  supply  of  those  guanos  which  are  rich  in  uric  acid  is  falling  off. 

lied  Woods. — There  are  two  distinct  classes  of  red  woods  used  by  dyers  and  printers, 
by  the  manufacturers  of  red  inks  and  of  certain  pigments.  On  the  one  hand  are  the 
soft  woods,  all  produced  by  different  species  of  the  genus  Caesalpinia.  The  principal 
kinds  are  Pernambuco  wood,  Brazil  wood,  peach  wood,  Lima  wood,  Nicaragua  wood, 
Santa  Martha  wood,  Brazilette  and  Sapan  wood.  All  these  except  the  last  are 
produced  in  Central  and  South  America.  Sapan  is  a  product  of  India  and  Siam. 
The  colouring  matter  of  these  woods,  Brasiline,  (C22H1807  according  to  Kopp,  but 
to  Liebermann  C16H1405),  crystallises  in  small  colourless  needles,  but  the  watery 
solution,  on  exposure  to  the  air,  and  especially  on  boiling  or  in  presence  of  alkalies, 
turns  crimson. 

In  dyeing,  a  very  fine  but  fugitive  red  colour  is  obtained  from  the  red  woods. 

The  red  woods  are  extensively  used  for  the  production  of  red  inks.  For  this 
purpose  there  are  taken  250  grammes  red  wood,  30  grammes  alum,  30  grammes  tartar, 
and  2  litres  water,  and  the  decoction  is  boiled  down  to  2  litres.  The  liquid  is  filtered ; 
and  for  those  who  like  a  perfectly  limpid  ink  it  is  now  ready  for  use.  Those  who 
prefer  inks  which  may  clog  in  the  pen  and  dry  slowly  add  30  grammes  gum-arabic  and 
30  grammes  sugar-candy.  A  finer  and  more  permanent  ink  is  obtained  by  dissolving 
2  decigrammes  carmine  in  15  grammes  liquid  ammonia.  At  present  red  inks  are 
made  simply  with  solution  of  magenta  to  which  a  little  alum  has  been  added,  or  by 
dissolving  aurine  (rosolic  acid)  in  sodium  carbonate,  or  simply  with  eosine  alone.  Eosine 
ink  is  made  by  dissolving  i  part  eosine  in  150  to  200  parts  boiling  water.  Yiolet 
aniline  ink  is  obtained  by  dissolving  i  part  soluble  aniline  violet  blue  in  about  300 
parts  of  water. 

Brasilein,  C16H1205,  an  oxidation  product  of  brasiline,  forms  small  dark  crystals  with 
a  greyish  metallic  lustre,  which  dissolve  in  hot  water  with  a  bright  rose  colour  and  an 
orange  fluorescence. 

The  second  class  of  red  woods,  the  hard  woods,  comprise  barwood,  camwood, 
ganders — or  santalwood — and  calliatura  wood.  The  colouring  matter  of  these  woods 
is  very  sparingly  soluble  in  water  and  is  accompanied  with  a  yellow  principle,  so  that 
they  dye  tones  more  inclining  to  a  scarlet.  Barwood  and  camwood  are  obtained 
from  Africa,  and  are  both  said  to  be  the  product  of  Baphia  nitida,  though  the  colouring 
matter  of  camwood  is  found  in  practice  to  be  the  more  soluble.  They  contain  23  per 


83CT.  iv.]  TREATMENT   OF  COAL-TAR.  519 

cent,  of  colouring  matter.  In  like  manner  santalwood  and  calliatura  are  alleged  to  be 
identical,  the  tone  of  the  colour  being  modified,  perhaps  by  difference  of  soil.  Both 
are  obtained  from  India.  Their  colouring  principle,  santaline,  contains  C17H1606. 

The  dyewoods  of  whatever  colour  are  met  with  in  commerce  in  four  different 
states;  in  chips,  in  raspings,  in  liquid  extracts,  or  in  solid  or  paste  extracts.  These 
different  preparations  are  used  according  to  the  texture  of  the  materials  to  be  dyed  or 
printed. 

Most  woods  require  after  chipping  or  rasping  to  lie  exposed  to  the  air  for  some 
time,  and  to  expedite  the  process  they  are  sprinkled  with  water.  This  addition  is 
carried  to  such  a  height  that  it  becomes  a  fraud.* 

The  liquid  extracts  of  the  woods  are  often  found  to  contain  treacle  (beet),  dextrine, 
sodium  sulphate,  and  extracts  of  materials  of  little  tinctorial  value,  such  as  of  chestnut, 
and  quebracho.  Extract  of  sumac  is  rarely  added. 

The  proportion  of  the  ash  found  in  an  extract  is  no  better  guide  to  its  quality  than 
is  the  specific  gravity. 

For  detecting  and  determining  treacle,  starch,  sugar,  and  dextrine,  L.  Brueh 
proceeds  as  follows :  from  i  to  5  grammes  of  the  extract  dried  at  100°  are  treated 
with  absolute  alcohol  until  the  alcoholic  solution  no  longer  gives  colour  reactions.  The 
sugar  and  the  dextrine  remain  in  the  residue  along  with  other  colouring  matters. 

Blue  Colouring  Matters. — Indigo. — Indigo  is  the  chief  blue  dye.  Although  known 
to  the  Romans  and  Greeks,  who  used  it  for  painting  purposes,  it  was  not  employed 
as  a  dyestuff  in  Europe  until  about  the  middle  of  the  sixteenth  century.  Indigo  is  a 
substance  which  is  widely  dispersed  in  the  vegetable  kingdom.  It  is  found  in  large 
quantity  in  the  leaves  of  several  species  of  the  anil  plants,  Indigofera,  belonging  to 
the  family  of  the  Papilionacece.  Indigo  is  also  obtained  from  woad,  Isatis  tinctoria, 
JYerium  tinctorium,  Marsdenia  tinctoria,  Polygonum  tinctorium,  Asclepias  tingens,  &c. 
The  indigo  is  not  met  with  in  the  plants  ready  formed,  but  is  generated  when  the 
freshly-pressed  juice  of  the  plant  is  exposed  to  the  action  of  the  atmosphere. 

According  to  the  results  of  a  series  of  experiments,  it  appears  that  in  the  living 
plant  the  colourless  pigment  is  present  in  combination  with  a  base,  lime  or  an  alkali. 
Dr.  Schunck  states  that  the  indigo  plant  contains  a  material  which  he  has  termed 
indican,  which  either  by  fermentation  or  by  the  action  of  strong  acids  is  converted 
into  indigo  blue  and  a  peculiar  kind  of  sugar,  indigo  glycine,  according  to  the  following 
formula — 

C^NA,  +  4H20  -  flja^O,,*  6C^y 
Indican.  Indigo  blue.     Indigo  glycine. 

The  indigo  of  commerce  is  prepared  from  the  indigo  plants  in  the  East  and  West 
Indies,  Southern  and  Central  America,  Egypt,  and  other  parts.  In  Hindostan  indigo 
is  prepared  from  the  Nerium  tinctorium.  The  following  five  varieties  of  the  indigo 
plant  are  more  particularly  employed  for  the  preparation  of  this  dye  material : 
— Indigofera  tinctoria,  I.  anil,  I.  disperma ,  I.  pseudotinctoria,  and  /.  argentea.  The 
plant  requires  a  warm  climate  and  a  soil  so  situated  that  it  is  not  liable  to  become 
inundated.  When  the  plants  have  grown  to  maturity  they  are  cut  down  with  a  sickle 
•close  to  the  soil  and  transferred  to  the  factory,  where  the  indigo  is  extracted  from  the 
plant  by  the  following  process : — The  factory  is  fitted  with  large  water  tanks,  filtering 
apparatus,  presses,  a  cauldron,  drying-room,  and,  lastly,  with  fifteen  to  twenty  tanks 
t>f  brickwork  laid  in  hydraulic  cement  and  plastered  inside  with  the  same  material. 
Into  these  tanks  the  branches,  twigs,  and  the  leaves  are  placed,  and  water  is  run  in, 
care  being  taken  to  force  the  green  plants  down  under  the  water  by  the  aid  of  stout 
.wooden  balks  wedged  tight  against  the  sides  of  the  tanks.  At  the  usual  high  tempera- 
*  Compare  Slater,  Manual  of  Colours :  Lockwood  &  Son,  London. 


5 20  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

ture  of  the  air  in  the  tropical  regions  fermentation  soon  sets  in,  and  the  liquid  con- 
tained in  the  tanks  assumes  a  bright  straw-yellow  or  golden-yellow  colour,  a  large 
quantity  of  gas  is  evolved,  and  after  a  lapse  of  nine  to  fourteen  hours,  the  liquid, 
having  become  of  a  deeper  yellow  hue,  or  almost  the  colour  of  sherry  wine,  is  run  from 
the  fermenting  tanks  into  a  very  large  tank  of  similar  construction,  into  which,  when 
as  full  as  may  be  judged  convenient,  a  number  of  workmen  enter,  provided  with  long 
bamboo  poles,  and  commence  stirring  the  fluid  vigorously  for  the  purpose  of  exposing 
it  as  much  as  possible  to  the  action  of  the  air.  During  this  operation,  continued  for 
some  two  or  three  hours,  the  colour  of  the  liquid  gradually  changes  to  pale  green,  and 
the  indigo  may  then  be  seen  suspended  in  the  liquid  in  very  small  flocks.  The  liquid 
is  then  left  to  stand,  and  the  suspended  matter  gradually  subsiding,  the  water  is 
gradually  run  off  by  the  aid  of  taps  or  plugs  fitted  into  the  tank  at  different  heights. 
At  last  the  somewhat  thick,  yet  fluid,  precipitate  of  indigo  is  run  into  a  cauldron, 
where  it  is  boiled  for  about  twenty  minutes  in  order  to  prevent  it  fermenting  a 
second  time,  for  by  this  second  fermentation  it  would  be  rendered  useless.  The 
magma  is  left  in  the  cauldron  over  night  and  the  boiling  resumed  next  day,  and  then 
continued  for  three  to  four  hours,  after  which  the  indigo  is  run  on  to  large  filters,  con- 
sisting first  of  a  layer  of  bamboo,  next  mats,  and  on  these  stout  canvas,  all  placed  in 
a  large  masonry  tank.  Upon  the  canvas  is  left  a  thick,  very  deep  blue,  nearly  black 
paste,  which  is  thence  taken  and  put  into  small  wooden  boxes,  perforated  with  holes 
and  lined  with  canvas ;  a  piece  of  canvas  is  put  on  the  top  of  the  paste,  and  next  a 
piece  of  plank  is  fitted  closely  into  the  box.  So  arranged,  a  number  of  these  are 
placed  under  a  screw-press  for  the  purpose  of  eliminating,  by  a  gradually  increased 
pressure,  the  greater  portion  of  the  water,  and  thus  solidifying  the  pasty  material.  On 
being  removed  from  these  boxes  the  cakes  of  indigo  are  transferred  to  the  drying-room, 
and  there,  daylight  and  direct  sunlight  being  carefully  excluded,  gently  dried  by  the 
aid,  in  some  cases,  of  artificial  heat.  In  order  to  prevent  the  cracking  of  the  cakes, 
the  drying  has  to  be  effected  very  gently,  and  lasts  usually  for  some  four  to  six  days. 
The  dried  cakes  of  indigo  are  next  packed  in  stout  wooden  boxes  and  then  sent  into 
the  market.  The  exhausted  plants  are  used  for  a  manure,  for  although  the  boughs  on 
being  planted  in  the  soil  would  again  grow,  they  would  not  yield  either  in  quality  or 
quantity  enough  indigo  to  pay  the  expenses  of  culture.  1000  parts  cf  fluid  from  the 
fermenting  tanks  yield  0*5  to  0*75  parts  of  indigo. 

Properties  of  Indigo. — The  indigo  met  with  in  commerce  exhibits  a  deep  blue  colour, 
dull  earthy  fracture,  and  when  rubbed  with  a  hard  substance  (the  better  kinds  of 
indigo  even  when  rubbed  with  the  nail  of  the  thumb)  give  a  glossy  purplish-red 
streak.  In  addition  to  a  larger  or  smaller  quantity  of  mineral  substances,  indigo 
contains  a  glue-like  substance,  or  indigo  glue ;  a  brown  substance,  indigo  brown  ;  a  red 
pigment,  indigo  red ;  and  the  indigo  blue,  or  indigotine,  Cl6H10N202,  the  peculiar  dye 
material  for  which  the  drug  is  valued.  The  quantity  of  indigo  blue  contained  in  the 
several  kinds  of  indigo  of  commerce  varies  from  20  to  75  and  80  percent.,  and  averages 
from  40  to  50  per  cent.  Indigo  may  be  purified  according  to  Dumas'  process  by 
digestion  in  aniline,  whereby  the  indigo-red  and  indigo-brown  pigments  are  dissolved 
and  eliminated.  According  to  Dr.  V.  Warther,*  Venetian  turpentine,  boiling  parafline, 
spermaceti,  stearic  acid,  and  chloroform,  are,  at  high  temperatures,  solvents  for  indigo 
blue.f 

Testing  Indigo. — The  quality  of  indigo  is  ascertained  by  its  deep  blue  colour  and 
lightness.:}:  G.  Leuchs  found  that  in  forty-nine  samples  of  this  material  the  best  con- 
tained 60-5  per  cent.,  the  worst  24  per  cent,  of  indigotine,  the  specific  gravity  of  the 

*  See  Chemical  News,  vol.  xxiii.  p.  252. 

t  See  also  CJiemical  News,  vol.  xxv.  p.  58,  "  On  the  Solubility  of  Indigo  (Indigotine)  in  Phenic 
Acid." 

i  See  Chemical  News,  vol.  xxiv.  p.  313. 


SECT,  iv.]  TREATMENT  OF  COAL-TAR.  521 

former  being  low  and  of  the  latter  high.  Indigo  should  float  on  water,  and  when  of 
good  quality  it  should  not,  on  being  broken  to  pieces,  deposit  at  the  bottom  of  the 
vessel  filled  with  water  in  which  it  is  contained  a  sandy  or  earthy  sediment.  On 
being  ignited,  indigo  should  leave  only  a  comparatively  small  quantity  of  ash. 
When  suddenly  heated,  indigo  should  give  off  a  purplish-coloured  vapour,  sublimed 
indigotine,  and  the  drug  should  be  perfectly  soluble  in  fuming  sulphuric  acid, 
yielding  a  deep  blue  fluid.  That  kind  of  indigo  which  on  being  rubbed  with  a 
hard  body  exhibits  a  reddish  coppery  hue  is  termed  coppery-tinged  indigo,  indigo 
cuivre.  In  order  to  test  indigo  more  accurately,  a  weighed  portion  is  dried  at 
1 00°  for  the  purpose  of  ascertaining  the  quantity  of  hygroscopic  water  contained, 
which  should  not  exceed  from  3  to  7  per  cent.  Next  the  dried  indigo  is 
ignited  for  the  purpose  of  ascertaining  the  quantity  of  ash  it  yields.  For  good 
qualities  of  the  drug  this  amounts  to  7  to  9*5  per  cent.  Numerous  methods  have  been 
proposed  by  practical  dyers  as  well  as  by  scientific  men  for  the  purpose  of  ascertaining 
the  value  of  indigo  ;  that  is  to  say,  the  quantity  of  indigotine  it  contains.  Some  of 
these  processes  are  either  too  tedious,  and  cause  great  loss  of  time,  or  are  not  sufficiently 
exact.  A  commercial  sample  of  indigo  may  be  treated  first  with  water,  next  with 
weak  acids,  then  with  alkaline  solutions  and  alcohol,  and  the  ash  and  hygroscopic 
water  having  been  estimated,  the  residue  of  the  different  operations  will  be  the  indigo- 
tine, the  process  being  based  upon  the  insolubility  of  the  latter  in  the  different  solvents 
used  for  the  removal  of  the  impurities  met  with  in  the  sample  under  examination. 
Mittenzwei  proposes  to  reduce  the  indigo  by  means  of  an  alkali  and  solution  of  ferrous 
sulphate,  to  pour  over  the  surface  of  the  liquid  a  layer  of  petroleum  oil  for  the  purpose  of 
excluding  air,  to  take  by  the  aid  of  a  curved  pipette  a  known  bulk  of  the  indigo-con- 
taining fluid,  and  to  introduce  this  fluid  at  once  into  a  test-jar  placed  over  mercury, 
and  containing  a  known  and  accurately  measured  bulk  of  pure  oxygen.  As  i  gramme 
of  white  indigotine  (soluble)  requires  for  its  conversion  into  blue  (insoluble)  indigotine 
45  c.c.  of  oxygen,  the  quantity  of  gas  absorbed  gives  the  quantity  of  indigotine.  This 
method  yields  very  correct  results,  but  requires  an  experienced  manipulator. 

For  the  spectroscopic  examination  of  indigo,  Wolff  treats  0*5  grammes  of  the 
sample  to  be  examined  with  5  c.c.  of  concentrated  sulphuric  acid,  effects  its  complete 
solution  by  shaking  up  and  digestion,  and  dilutes  to  i  litre.  The  light  is  measured 
in  a  stratum  of  i  centimetre  in  thickness. 

Indigo  Blue. — This  substance,  also  known  as  indigotine,  may  be  obtained  from  the 
indigo  of  commerce,  either  by  carefully  conducted  sublimation,  or,  as  already  stated,  by 
treating  indigo  with  lime,  ferrous  sulphate,  and  water.  The  formula  of  indigo  blue 
is  C16H10N202.  When  indigo  blue,  in  the  presence  of  alkaline  substances,  is  brought 
into  contact  with  bodies  which  readily  absorb  oxygen  —  for  instance,  with  ferrous 
sulphate,  sulphites,  &c. — there  is  formed,  with  simultaneous  decomposition  of  water, 
white  indigo,  or  reduced  indigo,  C16H12N202.  The  use  of  indigo  as  a  dye  material  is  in 
great  measure  based  upon  this  reduction.  By  the  action  of  oxidising  substances,  such 
as  permanganic  acid,  chlorine,  chromic  acid,  a  mixture  of  so-called  red  prussiate  of 
potash  (potassium  ferricyanide)  with  potash,  soda,  oxide  of  copper,  <fec.,  indigo  blue 
is  converted  into  isatine,  C16H,0N204.  Indigo  blue  dissolves  in  concentrated  sulphuric 
acid,  but  becomes  thereby  radically  changed,  and  cannot  be  brought  back  to  its  primitive 
state,  forming  as  it  does  with  the  acid  a  chemical  compound — sulphindigotic  acid,  or, 
as  it  is  termed  by  dyers,  sulphate  of  indigo.  When  this  acid  solution  is  treated  with 
potassium  carbonate  there  is  formed  indigo  extract,  soluble  indigo,  a  deep  blue  precipi- 
tate soluble  in  140  parts  of  cold  water.  This  indigo  extract  is  used  as  a  water-colour 
pigment ;  while,  mixed  with  some  starch  and  a  little  gum- water,  it  is  formed  into  balls 
or  other  suitable  shapes  and  used  as  washing-blue,  ultramarine  being  also  employed  for 
the  same  purpose. 


522  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

The  present  yield  of  indigo  is  4450  tons  yearly  : — 

Bengal,  Oude,  Madras    .        .        .        .     3500 

Java 300 

Guatemala,  &c 55° 

Artificial  Indigo,  though  of  very  high  theoretical^  interest,  is  not  technically  im- 
portant, and  modifications  in  the  culture  and  treatment  of  the  indigo-plant  are  in 
progress,  which  are  likely  to  improve  the  yield,  both  in  quantity  and  quality,  thus 
reducing  the  probability  of  the  success  of  any  artificial  substitute.  It  may  be  men- 
tioned that  natural  indigo  is  a  product  of  fermentation,  set  up  by  a  specific  bacillus. 
Micro-organisms  play  important  parts  also,  both  for  good  and  evil,  in  dyeing  with  indigo. 

Logwood,  or  Campeachy. — This  dye  material  is  the  wood,  freed  from  bark  and  splint, 
of  the  logwood  tree,  Hcematoxylon  campechianum,  a  native  of  Central  America,  and 
cultivated  in  several  of  the  West  Indian  Islands.  The  colouring  matter  contained  in 
this  wood  is  called  hsematoxyline,  C,6H1406,  a  pale  yellow,  transparent,  aciculated 
crystalline  body.  By  itself  it  is  not  a  pigment,  but  is  a  colourable  material,  which 
becomes  coloured  when  brought  into  contact  with  strong  alkalies,  more  especially  with 
ammonia  and  the  oxygen  of  the  air.  The  solution  of  hsematoxyline  in  water  is  quite 
colourless,  but  becomes  at  once  purple-red  by  the  smallest  addition  of  ammonia.  The 
colouring  matter  thus  formed  is  termed  hsemateine.  Logwood  is  used  for  the  purpose 
of  dyeing  blue  and  black.  Extract  of  logwood  is  very  frequently  prepared.  As 
with  other  similar  extracts,  it  should  be  made  in  vacuum  pans  withdrawn  from  the 
oxidising  action  of  the  air,  because  the  hsematoxyline  contained  in  logwood  becomes 
thereby  altered.  The  makers  of  the  extracts  of  dyewoods  invariably  use  vacuum 
apparatus. 

Instead  of  extract  of  logwood,  there  has  been  used  since  1 880  a  preparation  known 
as  "  hematine,"  which  is  probably  impure  hsematoxyline.  1 5  parts  of  hematine  are 
reputed  equal  to  100  parts  of  the  best  logwood.  It  gives  faster  and  brighter 
shades. 

Litmus  is  used  for  giving  a  blue  tint  to  lime  and  white-wash.  It  is  obtained  from 
the  same  lichens  as  archil  and  cudbear.  The  difference  in  the  preparation  is  that  the 
fermentation  and  oxidation  have  been  carried  further,  and  that  the  red  colouring- 
matter,  ortine,  has  been  transformed  into  the  blue  compound  azolitmine — 

C7H802    +    NH3    +    202    -    C7H7N04    +    2^0. 

The  fermented  mass  is  mixed  with  chalk  and  gypsum,  and  brought  into  commerce 
moulded  into  small  cubes. 

The  bezettes  or  turnesol  rags,  obtained  in  the  South  of  France  from  the  juice  of 
Croton  tinctorium,  contain  a  different  colouring-matter.  They  are  turned  purple-red 
or  dark-green  by  ammonia.  They  are  used  in  Holland  for  colouring  cheese,  confec- 
tionery, liqueurs,  &c. 

Yellow  Colouring  Matters. — Fustic  (Cuba-wood  or  old  fustic)  is  the  wood  of  a 
species  of  mulberry  (Morus  tinctoria  or  Madura  aurantiaca}.  It  is  chiefly  imported 
from  Cuba  and  Hayti.  The  heart-wood,  which  alone  is  used,  is  of  a  yellow  colour,  here 
and  there  verging  to  orange.  The  colour  is  due  to  a  colourless  crystalline  compound, 
morine,  C12H80.,  which  is  found  in  the  wood  in  combination  with  lime  and  a  peculiar 
tannic  acid,  named  morinetannic  acid  (or  Maclurine),  C13H10O6,  which  is  found  deposited 
in  the  wood,  sometimes  in  considerable  quantities.  Morine  takes  a  yellow  colour  on 
exposure  to  air,  or  on  contact  with  alkalies.  Maclurine,  if  treated  with  caustic  potassa, 
is  split  up  into  phloroglucine  and  protocatechutic  acid. 

.       Fustic  is  used  for  dyeing  yellows  and  blacks,  where  it  serves  to  correct  the  blue 
tone  of  logwood.     It  is  extensively  used  as  a  liquid  extract  and  also  as  a  paste. 

Young  Fustic  (Zante  Fustic,  Fustet,  or  Fiset)  is  a  greenish-yellow  wood,  striped 


SECT,  iv.]  TREATMENT  OF  COAL-TAR.  523 

with  brown,  obtained  from  Rhus  cotinus,  a  shrub  growing  wild  in  the  South  of  Europe, 
and  sometimes  named  Venetian  sumac.     Its  colouring-matter,  fustine,  or  fisetine, 

C23H1003(OH)6, 
is  a  bright,  but  rather  fugitive  dye.     It  is  chiefly  used  by  some  woollen-dyers. 

Annatto  (Annotto,  Arnatto,  or  Orleans)  is  a  yellowish-red  colouring  matter, 
formerly  much  used  in  silk-dyeing,  but  now  employed  only  in  the  manufacture  of 
varnishes  and  in  colouring  butter.* 

It  is  sold  as  a  stiff  paste,  and  is  obtained  from  the  fruit  of  Bixa  Orellana,  a  shrub 
native  in  South  America,  and  cultivated  at  Cayenne,  in  the  Antilles,  and  in  India.  It 
•contains  two  colouring  matters — bixine,  a  yellow ;  and  orelline,  a  red  (C5H6O4). 

Berries  (Persian  berries,  French,  Avignon,  or  Turkey  berries)  are  the  fruit  of 
Rhamnus  infectorius,  R.  saxatilis,  and  R.  amygdalinus,  species  of  buckthorn.  They  are 
met  with  large  and  full,  of  an  olive-yellow  colour,  and  also  smaller,  wrinkled  and  dark- 
brown.  The  former  kind  are  collected  before  full  ripeness,  whilst  the  latter  are  left  to 
•dry  on  the  trees.  They  contain  a  fine  golden-yellow  colour,  chrysorhamnine,  which  Bolley 
regards  as  identical  with  quercetine,  and  an  olive-yellow  colouring  matter,  xantho- 
rhamnine.  They  are  extensively  used  in  calico-printing,  chiefly  in  the  form  of  extract, 
in  staining  paper,  and  in  the  manufacture  of  yellow  lake. 

Turmeric  is  the  dried  root  of  Curcuma  longa  and  0.  rotunda,  plants  cultivated 
•chiefly  in  Bengal.  The  roots,  which  vary  in  thickness  from  that  of  a  quill  to  a  diameter 
of  £  inch,  are  wrinkled,  and  have  ring-like  swellings  at  short  intervals.  They  contain 
ii  to  12  per  cent,  of  curcumine  (C8H1002),  a  yellow  tinctorial  principle. 

Weld  or  Wold;  a  plant  sometimes  erroneously  confounded  with  woad,  was 
formerly  much  used  for  dyeing  moderately  fast  yellows  on  silk  and  cotton  with  sodium 
aluminate.  Its  colouring  principle  is  luteoline. 

Quercitron  (commonly  named  "  bark  "  by  the  dyers)  is  the  rind  of  Quercus  infectoria, 
&  species  of  oak  growing  in  North  America.  There  are  two  varieties,  obtained  re- 
spectively from  Philadelphia  and  Baltimore,  the  former  being  superior.  It  contains  a 
jellow  colouring  matter,  quercitrine  C3SH80O17,  and  tannic  acid.  On  treatment  with 
dilute  acids,  quercitrine  splits  up  into  isodulcite  (a  sugar  of  the  formula  C6H1005)  and 
quercetine,  C27H18Oj.,,  a  bright  yellow  powder  sold  as  flavine.  Quercitron,  both  in  sub- 
stance, as  extract,  and  as  flavine,  is  more  extensively  used  than  any  other  yellow  dye. 

Among  other  yellow  dye-wares  we  may  mention  Serratula,  tinctoria,  dyers'  broom 
•(Genista  tinctoria) ;  wongshy,  the  seed  pods  of  Gardenia  Jlorida  ;  puree  or  Indian  yellow, 
a  colour  consisting  of  magnesium  euxanthate  and  free  euxanthon,  and  obtained  from 
the  urine  of  cows  fed  upon  the  leaves  of  the  mango.  The  vegetable  yellow  colours 
have  been  almost  entirely  superseded  by  chrysoidine,  tropaeoline,  picric  acid,  Victoria 
yellow,  and  other  coal-tar  colours. 

Brown,  Green,  and  Black  Colours. — Brown  colours  were  formerly  obtained  from 
•mixtures  of  reds,  yellows,  and  blues,  or  of  yellows  and  reds  with  blacks.  Browns  are 
often  dyed  with  catechu  and  other  tanniferous  extracts,  in  conjunction  with  oxidising 
agents,  such  as  potassium  dichromate,  ammonium  vanadate,  &c.  They  are  also 
;obtained  with  the  so-called  "  patent  colours  "  (Cachou  de  Laval)  invented  by  Croissant 
and  Bretonniere. 

Black  is  obtained  with  ferrous-ferric  oxide  in  conjunction  with  solutions  of  tannin 
•or  gallic  acid,  with  decoction  of  logwood  and  potassium  chromate,  or,  in  printing,  with 
aniline  black. 

Greens  were  obtained  with  mixtures  of  yellows  and  blues,  or  with  Chinese  green 
(Laokao)  from  RJiamnus  cMorophorus  and  R.  utilis,  and  with  sap  or  bladder  green  from 

*  For  this  latter  purpose  it  is  utterly  improper,  as  it  is  made  up  with  stale  urine  and  swarms 
with  bacteria,  some  of  which  may  be  morbific. 


524  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

the  berries  of  the  buckthorn  (Rhamnus  catharticus).  The  use  of  green  vegetable  colours 
has  been  much  interfered  with  by  the  introduction  of  methyl-green,  malachite  green,  &c. 

Ordinary  writing  ink  consists  essentially  of  ferric  and  ferrous  tannates  and  gallates, 
held  in  suspension  by  means  of  gum-arabic.* 

A  good  black  ink  may  be  obtained  by  extracting  i  kilo,  pulverised  gall-nuts  and  150 
grammes  logwood,  with  5  litres  hot  water,  dissolving  at  the  same  time  600  grammes  gum 
in  2 1  litres  water  and  |  kilo,  copperas  in  4  kilos,  of  water.  The  tannic  extract  and 
the  solutions  of  gum  and  copperas  are  then  poured  together,  and  a  few  drops  of  oil  of 
cloves  or  gualtheria  are  added  and  water  enough  to  make  up  16  litres. 

Tannin  Ink  is  obtained  by  dissolving  1 2  grammes  tannin,  40  grammes  copperas,  and 
50  grammes  gum  in  i  litre  of  boiling  distilled  water.  Iron  inks,  beside  attacking  the 
steel  pens,  have  the  defect  that  the  writing  in  time  turns  yellow.  Hence  the  proposal 
to  use  ammonium  vanadate  instead  of  iron  salts  deserves  notice. 

Ink  from  1000  parts  decoction  of  logw.ood  (i  part  wood  to  water)  and  i  part  yellow 
(neutral)  potassium  chromate,  with  the  addition  of  a  trace  of  mercuric  chloride,  is  at 
once  cheap,  permanent,  and  beautiful ;  the  colour  is  a  compound  of  haemateine  and 
chromium  oxide. 

To  obtain  the  so-called  alizarine  ink,  42  parts  galls  and  3  parts  madder  are  extracted 
with  water,  so  as  to  make  up  120  parts  of  liquid,  to  which  are  added  1*2  part  indigo 
sulphate,  5*2  parts  copperas,  and  2  parts  iron  pyrolignite  solution. 

The  reddish-blue  ink  from  Rouen  (encre  rouennaise),  extensively  used  in  France,  con- 
sists of  a  decoction  of  750  grammes  logwood,  35  grammes  alum,  and  31  grammes  gum 
in  5  to  6  litres  water.  Coupier's  induline  ink  is  simply  a  solution  of  induline  in  50  parts 
of  water. 

Copying  inks  are  merely  strong  common  inks  with  a  large  addition  of  gum  and 
sugar  or  glycerine.  Inks  are  prevented  from  turning  mouldy  by  the  addition  of  a  little 
quinine  sulphate,  salicylic  acid,  or  phenol. 

TAR  COLOURS. 

Repeated  attempts  have  been  made  to  arrange  the  colouring  matters  obtained  from 
coal-tar  in  natural  groups. 
R.  Nietzki  distinguishes : 

1.  Nitro  compounds. 

2.  Azo  colouring  matters. 

3.  Triphenyl  methan  colouring  matters. 

4.  Indamines  and  indophenoles. 

5.  Saffranines  and  their  allies. 

6.  Aniline  black. 

7.  Indulines  and  nigrosines. 

8.  Quinoline  and  acridine  colouring  matters. 

9.  Anthraquinone  colouring  matters. 

The  nitro-compounds  contain  the  group  NO,,  e.g.,  picric  acid,  binitrocresol. 

The  azo-colours  contain  the  groups  -  N  =  N  -  .  The  entrance  of  the  azo-group  into 
a  hydrocarbon  or  into  a  compound  similar  in  its  behaviour  (e.g.,  anisol,  phenetol)  pro- 
duces in  the  first  place  certain  coloured  compounds  which  are  not  true  colouring 
matters,  as  they  do  not  unite  with  the  animal  fibre.  This  affinity  to  the  fibre  is 
obtained  only  by  the  introduction  of  certain  groups,  which  give  the  azo-compounds 
acid  or  basic  properties.  On  the  other  hand,  the  intensity  of  the  colouring  matter  is 
generally  heightened  and  the  tone  is  essentially  modified. 

*  Hence  has  been  derived  the  custom  of  adding  gums  or  sugars  to  all  inks,  even  such  as  are 
true  solutions  and  do  not  require  to  be  suspended. 


SECT,  iv.]  TAR  COLOURS.  525 

In  colouring  matters  which,  besides  the  benzene  group,  possess  no  higher  hydrocarbon 
residue,  the  colours  represented  are  merely  yellow,  orange,  and  brown.  Only  by  intro- 
ducing the  naphthaline  residue  there  are  obtained  reds,  and  by  its  repeated  introduction 
violets  and  blues.  The  introduction  of  groups  which  are  in  themselves  indifferent  (e.g., 
the  methoxyl  groups  OCH3)  may  produce  a  striking  modification  of  the  colouration. 
The  relative  position  of  the  groups  is  also  important.  Thus  the  compound  — 

0 


HO 

has,  e.g.,  a  red  colour  if  the  benzene  nucleus,  the  meta  position,  is  occupied,  but  a  blue 
if  the  para  position  is  taken. 

The  azo-dyes  in  technical  uses  are  mostly  sulph-acids  and  behave  as  acid  colours. 
There  are  employed  in  their  production  the  sulph-acid  of  the  diazo-compounds  or  of 
the  phenoles.  In  some  cases  the  previously  formed  azo-compound  is  converted  into  a 
sulph-acid  by  treatment  with  sulphuric  acid. 

The  triphenylmethan  colouring  matters  contain,  according  to  Nietzki,  the  group 

^\/  \|/ 

C  —  NH  —  or  C  —  0  —  which  is  to  be  regarded  as  the  chromogen  of  the  compound.  If 
the  salts  of  the  nitrogenous  triphenylmethan  colours  are  decomposed  by  alkalies  there 
occurs  an  addition  of  water,  and  there  are  formed  amide-derivatives  of  triphenylcarbinol 

which  contain  the  group  —  C  —    The  ring-shaped  combination  has  therefore  become 

OH. 

open.  These  carbinol  derivatives  are  generally  regarded  as  the  bases  of  the  colouring- 
matters  and  the  latter  as  salts  of  the  former.  But  in  truth  both  possess  a  distinct  con- 
stitution, and  in  consequence  quite  distinct  properties.  The  carbinol  compounds  are 
perfectly  colourless,  whilst  their  salts,  or  more  correctly  those  of  their  anhydrides,  are 
powerful  dyes.  The  conversion  of  the  carbinol  compounds  into  colouring  matters  is 
not  effected  as  easily  as  the  formation  of  salts  from  bases  and  acids,  but  requires  in 
many  cases  a  prolonged  action,  which  often  seems  to  follow  after  the  mere  formation 
of  a  salt.  Tetramethyldiamidotriphenylcarbinol  (the  colourless  base  of  malachite 
green)  dissolves  first  in  dilute  acids  to  a  colourless  liquid.  On  heating,  or  on  prolonged 
standing,  it  becomes  intensely  green,  all  the  triphenylmethan  colouring  matters  be- 
longing here  are  para-derivatives  —  i.e.,  they  contain  the  nitrogenous  or  oxygenous  groups 
in  the  para-position  to  the  methan  carbon.  Here  belong  the  true  aniline  colours,  such 
as  malachite  green. 

Indamines  and  Indophenoles  are  formed  when  paradiamines  or  para-amidophenoles 
are  oxidised  in  presence  of  rnonamines  or  phenoles.  Indamines  are  formed  by  oxidation 
in  a  neutral,  and  indophenoles  in  an  acid  liquid.  Indophenoles  form  colouring  matters 
in  the  free  state,  and  their  salts  are  colourless  ;  in  indamines  the  reverse  holds  good. 
Both  are  readily  decomposed  by  an  excess  of  acid  with  the  formation  of  quinones. 
Their  constitutional  formulae  are  probably 

Indamine.  Indophenol. 


HN-C6H4^;  HN-C6H4 


Saffranines  contain  four  atoms  of  nitrogen  in  their  molecule,  two  of  which  are  in  the 
fcrm  of  amido  groups.     Four  atoms  of  hydrogen  may  be  replaced  by  alcohol  radicles, 


526 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


and  two  by  acid  radicles — e.g.,  of  acetyl.  They  may  also  be  converted  into  diazo- 
compounds,  in  which  generally  one,  but  sometimes  two,  amido  groups  may  be  converted 
into  diazo  groups. 

In  all   these  substitutions  the  strongly  basic  nitrogenous  group  which  serves  for   I 
the  formation  of   the  monobasic  salts  is  not  attacked.     The   acetyl   derivations   of 
saffranine  still  form  salts,  and  the  primary  diazo-compounds  have  a  strongly  bibasic 
character,  and  contain,  therefore,  an  acid  molecule  which  is  not  linked  to  the  diazo- 
group. 

The  formation  of  saffranine  from  paradiamidodiphenylamine,  with  a  simultaneous 
oxidation  with  monamines,  lets  us  conclude  that  in  it  two  benzene  nuclei  are  connected  by 
an  atom  of  nitrogen,  that  both  the  amido  groups  belong  to  this  benzene  nucleus,  and 
are  in  the  para-position  as  regards  the  atom  of  nitrogen  which  connects  them. 

The  saffranines  are  therefore  closely  related  to  the  indamines,  and  are  formed 
from  the  latter  when  heated  with  monamines  in  an  aqueous  solution,  whilst  hydrogen 
is  being  split  off,  and,  if  no  oxidising  agent  is  present,  effects  a  partial  i  eduction  of  the 
indamine.  The  amidised  indamines  (e.g.,  toluylene  blue)  are  converted  directly  on  heat- 
ing with  partial  reduction  into  colouring  matters  resembling  saffranine.  Their 
ordinary  production  depends  on  the  oxidation  of  one  mol.  of  a  paradiamine  with  two 
mols.  of  a  monamine. 

The  mono-acid  salts  of  the  saffranines  are  generally  red,  but  the  introduction  of 
alcohol  radicles  into  the  amidic  groups  modifies  the  colours  towards  a  violet.  The 
introduction  of  methoxyl  and  ethoxyl  groups  into  the  benzene  nuclei  changes  the  tone 
of  the  colours  in  the  direction  of  yellow.  Upon  animal  fibres  and  upon  cotton 
mordanted  with  tannin  the  saffranines  take  very  readily,  producing  the  colour  of  their 
mono-acid  salts. 

The  formula  for  aniline  black  is  not  yet  decided. 

Among  the  indulines  and  nigrosines  are  included  a  series  of  colouring  matters  formed 
by  the  action  of  certain  nitro-  and  azo-compounds  upon  aromatic  amines  and  having  all 
blue-grey  or  black-blue  colours.  On  heating  amido-azo-benzol  with  aniline  hydro- 
chlorate  to  1 60°,  ammonia  is  eliminated,  and  there  is  formed  a  violet  colour,  C18H15N9 
(azo-diphenyl  blue),  which  may  be  regarded  as  the  first  link  of  the  induline  series. 

Flavaniline  is  ranked  among  the  quinidine  colours.  For  anthracene  colours,  see 
below. 

Schultzand  Julius  arrange  the  2  74  most  important  colouring  matters  as  follows  : — 
i.  Nitroso    colours  —  e.g.,  naphthol   green  B   (a 
ferrous  sodium,  salt  of  nitroso-/3-naphthol 
monosulphuric  acid) 


2.  Nitro  colours — e.g.,  picric  acid 


3.  Azoxy  colours — e.g.,  sun  yellow  (Jaune  soleil),  maize,] 
acid  curcumine  (a  sodium  salt  of  azoxystilbene-' 
disulphonic  acid) 


(a 

f  SO,NaNa03S  * 

ol 

~    C10H5 

1                   1 

"    C10H6 

I  NO—  Fe—  ONJ 

i 

OH 

i 

ONH4 

2 
"4' 

-Krr\3  ',  Flavaurin  =  C6H  J 

2 

[6 

NO, 

NO; 

x 

NO*                                I 

"4" 

S03NH 

4.  Azo  colours — e.g., 


Aniline  yellow,  amidoazo- 
benzol  hydrochlorate 

Fast  yellow  B,  acid  yellow\ 
B,  the  sodium   salt    of  I  _ 
amido  azotoluol-disulph- 1 
acid  . 


CH[i]C6H3 


CH[i]C6H3  {[' 
NHn.HCl 


2lSO.Na 


rf2lCH 
J  SOjNa* 
H1]^  =  N[i]C6H, 


O,Na 


SECT.   IV.] 


TAR  COLOURS. 


5.  Hydrazon  colours  —  e.g.',  phenanthrene  red,  the] 
sodium  salt  of  a-naphthyl-a-sulphacid  azo-  }• 


527 
[4-CN-NH-Cl0H6-S03Na 


phenanthreno  quinone 


J      CgH4  —  ON—  NH  —  C1 


6.  Diphenyl    methan     colours  ;     only      auramine' 

(hydrochlorate  of  imidote  tramethyldiamido 
diphenyl-methan)    .         .         .         .         . 

7.  Triphenyl    methan    colouring  mat-^  /[i]C6HJ4]N(CH3)a 

ters  —  e.g.,  fast  green  (the  sodium  I  =  H0  _  ~  I  [i]C6H4[4]N(CH3)x 

salt     of    tetramethyl-diphenyl-  [  '  IfilC  H  rN^"^"2  —  ^6^4  —  S03Na 

pseudo-rosanilinesulpho  acid)      ' 


[i]C6H4[4]N(CH3)2 
=NH  +H20 

[i]C6H4[4]N(CH3),H01 


CH2—  C6H4—  S03Na 


8.  Anthracene    colours — e.g.,     alizarine    (a-/3-dioxy- ^ 

anthraquinone)  .         .         .         .         .     J  ~    6 

9.  Indophenoles  — e.g.,      indophenol,      dimethyl-amido-a- )     _^  JC  HMO 

naphtho-quinone  anilide       .....      J 


10.  Oxazines — e.g.,  new  blue  (naphthylene  blue  R  in 
crystals);  fast  cotton  blue  =  dimethyl-phenyl-a- 
ammonium-/3-oxynaphthoxazine  .  .  . 


ii.  Thionine  colours,  Lauth's  violet,  thionine  hydro- 
chlorate   .  .... 


12.  Eurhodines — e.g.,   neutral  violet,] 

dimethyl-diamephenazineh  =  (CH3)2N[4]C6H3 
hydrochlorate  .         .          J 

13.  Saffranines — e.g.,    Magdalas 

red,     naphthaline     red, 
naphthaline  rose,  naph- 
thaline  scarlet,    Soudan  I  =  HC=HC[5J 
red,  rosa-naphthylamine 
(diamidonaphthylnaph- 
thazonium  chloride) 


[«]C'  H    [/3] 

•-N       r  "         6f      2 


N(CHS),01 


C6H3[4]NH,.HCl 


HC=HC[6]) 

=HC[5] 
H8Nt4] 


a 
l 


[4]CH= 


Cl 


[i]     /[2]CH=CH 

PA]          i 

[4]      l[3]CH=CH 
NHS 


14.  Indulines  and  nigrosiues  —  e.g.,  fast  blue 


-^r  «,' 


' 


•CO 


15.  Artificial  indigo 


1  6.  Quinoline  and  acridine  colours  —  e.g., 
flavaniline  (hydrochlorate  of  para- 
amido  phenyl  and  lepidine 


•CO 


•   =  CfiH4 


CH3 

[i]C=CH 

[2]N=C[4]C6H4[i]NH2.HCl 


In  research,  or  for  instruction  in  organic  chemistry,  such  an  arrangement  is  doubt- 
less preferable,  but  in  technology  it  seems  more  important  to  follow  the  process  of 
manufacture. 


528  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

i.  BENZOL  COLOURS. 

Commercial  benzol  contains,  besides  benzene  (true  benzol),  toluol  (C6Hj.CH3),  xylol 
C6H4(CH3)2,  and  cumol  C6H3(CH3)3. 

Nitrobenzol. — On  the  nitration  of  benzol  there  is  formed  nitrobenzol : 

C6H6  +  HN03  =  C6H5.N02  +  H,0. 
On  nitrating  toluol, 

CGH5.CH3  +  HNO3  =  C6H,.NO.CH3  =  H20, 

there  are  produced  three  isomcric  nitrotoluols,  chiefly  orthonitrotoluol  (boiling  point 
223°)>  with  small  quantities  of  meianitrotoluol. 

The  technical  nitrobenzol  is  therefore  a  mixture  of  nitrobenzol  and  nitrotoluol  along 
with  nitroxylol.  For  its  production  there  is  run  into  the  benzol,  in  a  cast-iron 
vessel  fitted  with  an  agitator,  a  mixture  of  two  parts  strong  nitric  acid  and  sulphuric 
acid.  It  must  be  refrigerated  at  first,  which  is  effected  by  letting  water  flow  over  the 
vessel ;  after  a  few  hours  the  temperature  is  gradually  let  rise  to  60-80°.  When 
the  reaction  is  completed  the  two  liquids  are  allowed  to  separate,  and  the  nitro- 
benzol is  purified  by  washing  it  with  water.  100  kilos,  benzol  yield  135  to  140  kilos, 
nitrobenzol. 

There  are  three  nitrobenzols,  corresponding  to  the  different  benzols: — i.  Light 
nitrobenzol,  boiling  between  205  and  210°.  It  forms  the  artificial  oil  of  bitter  almonds 
(not  to  be  confounded  with  the  benzaldehyd,  C6H5.COH,  prepared  from  toluol),  or 
mirbane  oil  (essence  de  mirbane),  sp.  gr.  =  i'2O.  It  is  used  in  quantity  in  perfumery 
and  in  soap-making,  and  also  in  the  sophistication  of  wines.  2.  Heavy  nitro-benzol, 
distilling  between  210  and  220°,  sp.  gr.  =  1-19.  Its  peculiar  odour  prevents  its  use 
in  perfumery.  From  this  kind  the  "  aniline  for  reds"  is  obtained.  3.  Very  heavy 
nitrobenzol,  distilling  between  222  and  235°,  sp.  gr.  =  1*167.  Its  odour  is  unpleasant. 

Aniline. — By  amidising  nitrobenzol  there  is  obtained  crude  aniline,  aniline  oil,  the 
initial  point  for  obtaining  the  aniline  colours.  It  is  substantially  a  mixture  of  aniline 
(amidobenzol)  (C6H5NH2)  and  toluidene  amidotoluol  (C6H4  NH2.CH3).  It  is  known  in 
the  trade  as  aniline  oil.  Pure  aniline  and  pure  toluidene  alone,  form  colours  only  under 
certain  conditions. 

Aniline  was  discovered  at  Dahme,  in  Saxony,  by  Dr.  Unverdorben,  in  1826,  among 
the  products  of  the  dry  distillation  of  indigo,  and  in  1833  Runge,  at  Oranienburg,  near 
Berlin,  discovered  its  presence  in  coal-tar.  Runge  also  discovered  that  aniline  yielded, 
when  brought  into  contact  with  a  solution  of  hypochlorite  of  lime  (bleaching  powder), 
a  beautiful  violet  colour;  hence  the  name  kyanol  (blue  colouring  oil).  Fritzsche  of 
St.  Petersburg,  1841,  thoroughly  investigated  the  substance  obtained  by  Dr.  Unver- 
dorben from  indigo,  ascertained  its  composition,  and  called  it  aniline,  from  anil,  the 
Portuguese  name  for  indigo.  In  the  year  1842  Zinin  found  that  when  nitrobenzol 
was  treated  with  sulphuretted  hydrogen  there  was  formed  a  base  which  he  termed 
benzidam.  The  further  researches  of  O.  L.  Erdmann  and  Dr.  A.  W.  Hoffmann  brought 
the  fact  to  light  that  Dr.  Unverdorben's  crystalline,  kyanol,  benzidam,  and  aniline  were 
the  same  substance,  to  which  the  aniline  was  then  finally  given.  We  owe  to  the  ex- 
tensive researches  of  Dr.  A.  W.  Hoffmann  our  present  knowledge  of  aniline  and  its 
compounds. 

Coal-tar  contains  0-3  to  0-5  per  cent,  of  aniline,  but  its  extraction  from  tar  is 
attended  with  so  many  difficulties  that  it  is  preferred  to  prepare  aniline  from  nitro- 
benzol by  a  reaction  discovered  by  Zinin — that  is  to  say,  to  bring  nitrobenzol  into  con- 
tact with  reducing  agents  :  i  molecule  of  nitrobenzol,  C6H5N20  =  123,  yields  i  molecule 
of  aniline,  C6H7lSr  =  93.  *n  practice  it  is  assumed  that  100  parts  of  nitrobenzol  yield 
100  parts  of  aniline. 


SECT.    IV.] 


BENZOL   COLOURS. 


5=9 


Fig-  393- 


Although  sulphuretted  hydrogen  completely  reduces  nitrobenzol  to  aniline,  the 
trade  working  on  a  large  scale  prefers  to  follow  Bechamp's  method,  the  treatment  of 
nitrobenzol  with  iron-filings  and  acetic  acid.  The  apparatus  in  use  for  carrying  out 
this  operation  was  devised  by  Nicholson,  and  is  exhibited  in  Fig.  393.  It  consists 
essentially  of  a  cast-iron  cylinder,  A, 
of  10  hectolitres  (220  gallons)  cubic 
capacity.  A  stout  iron  tube  is  fitted 
to  this  vessel,  reaching  nearly  to  the 
bottom  of  the  cylinder.  The  upper 
part  of  this  tube  is  connected  with 
the  machinery,  G,  while  the  surface 
of  the  tube  is  fitted  with  steel  pro- 
jections. The  tube  serves  to  admit 
steam,  besides  acting  as  a  stirring 
apparatus.  Sometimes,  instead  of 
this  tube,  a  solid  iron  axle  is  em- 
ployed, and  in  this  case  there  is  a 
separate  steam -pipe,  D.  Through 
the  opening  at  K  the  materials  for 
making  aniline  are  put  into  the  ap- 
paratus, while  the  volatile  products 
are  carried  off  through  E.  H  serves 
for  emptying  and  cleaning  the  ap- 
paratus. The  S-shaped  tube  con- 
nected with  the  vessel,  J3,  acts  as 
a  safety-valve.  When  it  is  intended 
to  work  with  this  apparatus  there  is  first  poured  into  it  through  K  TO  kilos,  of 
acetic  acid  at  8°  B.  (  =  sp.  gr.  ro6o),  previously  diluted  with  six  times  the  weight  of 
water  ;  next  there  are  added  30  kilos,  of  iron-filings  or  cast-iron  borings,  and  125  kilos, 
of  nitrobenzol,  and  immediately  after  the  stirring  apparatus  is  set  in  motion.  The 
reaction  ensues  directly,  and  is  attended  by  a  considerable  evolution  of  heat  and  of 
vapours.  Gradually  more  iron  is  added  until  the  quantity  amounts  to  180  kilos.  The 
escaping  vapours  are  condensed  in  F,  and  the  liquid  collected  in  R  is  from  time  to  time 
poured  back  into  the  cylinder.  A .  The  reduction  is  finished  after  a  few  hours.  The 
resulting  thick  magma  exhibits  a  reddish-brown  colour,  and  consists  essentially  of 
hydrated  oxide  of  iron,  aniline,  acetate  of  aniline,  acetate  of  iron,  and  excess  of  iron. 
Leaving  the  acetic  acid  out  of  the  question,  the  process  may  be  elucidated  by  the  fol- 
lowing formula  : — 

C6H5N02  +  H20  +  Fe2  =  C6H7N  +  Fe2O3. 

Nitro-benzol.  Aniline.         Ferric 

oxide. 

This  magma  is  either  first  mixed  with  lime  or  is  put  into  cast-iron  cylinders  shaped 
like  gas-retorts,  and  submitted  to  distillation,  the  source  of  heat  being  either  an  open 
fire  or  steam.  The  product  of  this  operation,  consisting  of  aceton,  acetaniline,  aniline, 
nitrobenzol,  &c.,  is  rectified  by  a  second  distillation,  care  being  taken  to  collect  separately 
the  product  which  comes  over  between  115°  and  1 90°  ;  but  a  product  which  comes  over  at 
between  210°  and  220°  is  very  suitable  for  the  preparation  of  aniline  blue.  The  aniline 
oil  thus  obtained  is  a  somewhat  brown-coloured  liquid,  heavier  than  water,  and  pure 
enough  for  the  preparation  of  the  aniline  colours.  According  to  Brinmeyer,  acetic  acid 
is  not  necessary,  and  a  very  good  result  may  be  obtained  by  mixing  nitrobenzol  with 
60  parts  of  pulverised  iron  with  acidified  water  (2  to  2-5  per  cent,  of  hydrochloric  acid 

2  L 


530  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

upon  the  weight  of  nitrobenzol),  and  leaving  this  mixture  to  stand  in  a  retort  for  some 
three  days  before  distilling  off  the  aniline  oil.  In  the  aniline  oilworks  of  Coblentz  Freres, 
at  Paris,  nitrobenzol  is  reduced  by  the  aid  of  iron-filings,  a  portion  of  which  have  been 
coated  with  copper  by  being  immersed  in  a  solution  of  the  sulphate. 

The  composition  of  the  aniline  oil — essentially  a  mixture  of  aniline,  toluidine,  and 
pseudo-toluidine — depends  upon  the  nature  of  the  benzol  and  nitrobenzol  used  for 
its  preparation.  The  aniline  oil  boiling  between  180°  and  195°  (sp.  gr.  -  1-014  to 
1-021  =  2°  to  3°B.)  is  prepared  from  nitrobenzols  which  boil  between  210°  and  220°, 
and  the  aniline  it  yields  is  chiefly  used  for  aniline  red ;  while  for  aniline  blue  a  very 
heavy  nitrobenzol  is  employed,  and  for  aniline  violet  a  nitrobenzol  which  boils  at  210° 
to  225°.  The  following  table  exhibits  the  boiling-points  of  the  substances  which  have 
been  mentioned  : — 


Benzol          ....       80° 

Toluol 1 08° 

Nitro-benzol         .         .         .213° 


Nitro-toluol  .  .  .  225° 
Aniline  ....  182° 
Toluidine  108° 


As  regards  the  annual  production  of  aniline  oil,  it  is  now  (1871)  3,500,000  Ibs., 
of  which  2,000,000  Ibs.  are  consumed  in  Germany,  and  the  remainder  in  Switzerland, 
England,  and  France. 

The  so-called  pure  aniline,  which  has  been  produced  on  the  large  scale  since  1870, 
has  at  15°  the  sp.  gr.  1-0245.  1^  contains  very  small  quantities  of  toluidine  (not  above 
i  per  cent.),  and  forms  a  clear  solution  in  dilute  acids.  Its  chief  use  is  in  the  manufacture 
of  aniline  blue,  of  methyl  aniline  and  diphenyl  amine.  It  is  also  used  in  printing  for 
the  production  of  aniline  black. 

Toluidine  corresponds  in  purity  to  the  aniline  described  above.  It  contains  a  predo- 
minating quantity  of  ortho-  or  of  para-toluidine  according  to  the  manner  of  its  prepara- 
tion. The  largest  quantity  of  aniline  oil  is  that  "  for  red,"  a  mixture  of  aniline  with  the 
two  toluidines  and  a  little  xylidine,  which  distils  over  within  a  range  of  10-12°,  and  has 
the  sp.  gr.  1-004-1*006.  It  consists  approximately  of  20  percent,  aniline,  40  percent, 
toluidine,  and  40  ortho- toluidine.  Besides  aniline  for  reds  there  is  produced  a  much 
smaller  quantity  of  aniline  for  saffranine,  which  contains  a  large  relative  proportion  of 
aniline,  namely,  35  per  cent.  Its  sp.  gr.  is  i-oio,  and  it  distils  over  at  185-190°.  It 
has  a  similar  composition  to  the  so-called  echappes  from  the  manufacture  of  magenta, 
which,  indeed,  are  often  used  for  obtaining  saffranine. 

The  most  important  of  the  aniline  colours  are  the  following : — Aniline  red  (magenta), 
called  on  the  Continent  and  in  America  by  the  misleading  name  of  fuchsine,  and  for- 
merly by  the  still  worse  names  of  azaline  and  harmaline,  belongs  to  the  derivatives  of 
triphenyl  methan,  C19H16,  or  of  tolyldiphenyl  methan,  C20H18. 

CUT  O  TT     n~LT 

-.xi,  i\Ji.n-.*\-jtt.~ 

65  1643 

r~\    TT  1    /~H    TT 

^•n  oSr5  ^Mmr8 

Vy-Xl,  V_/.,_Ll, 

H  (H  (H 

Methan.  Triphenyl  methan.          Tolyldiphenyl  methan. 

If  in  triphenyl  methan  hydrogen  is  replaced  by  NH2,  and  again  by  CH3,C6H5,  &c., 
there  are  formed  leuko-bases,  which  form  with  acids  colourless  salts,  but  on  oxidation 
pass  into  colour-bases,  yielding  coloured  salts — e.g. : 

(C6H4.NH,  (C6H4.NH2  (C6H4.NH, 

0JCJL.NH,  rjC6H4.NH2  +  HC1  =    C  CPH4.NH;         +  H.O 

'   C6H4.NHf  ']  C6H4.NH;  loj^NRHCl 

in  IOH 


Paraleukaniline.  Pararosaniline.  Its  hydrochlorate. 

Magenta  is  a  mixture  of  pararosaniline  and  rosaniline  hydrochlorate  or  acetate,  rarely 


•SECT.    IV.] 


BENZOL   COLOURS. 


nitrate  or  sulphate,  the  rosaniline  being  derived  from  tolyldiphenyl  methan — e.g.,  as 
hydrochlorate,  C19H,6N3C104  and  CWH^N,C1O4. 

,CBH4.NH,  (C6H,.CH,NH, 

C   C6H4.NH,  andCj< 

(C,,H4.^H:HC1 


Salt  of  rosaniline,  with  3  mols.  of  acid,  have  an  insignificant  yellow  colour,  and  are 
decomposed  by  water  into  monacid  salts,  2  mols.  acid  being  liberated.  By  the  action 
of  nitrous  acid  upon  the  salts  of  rosaniline  there  are  formed  diazo-rosaniline  salts, 
which  on  boiling  in  water  yield  rosolic  acids. 

Aniline  red  is  produced  from  aniline  oil  by  treatment  with  various  oxidising  agents 
— e.g.,  with  stannic  chloride  (Yerguin),  carbon  perchloride  (Hofmann  and  Nathan- 
son),  mercuric  nitrate  (Gerber-Keller),  mercuric  chloride  (Schnitzer),  nitric  acid 
(Lauth  and  Depouilly),  antimonic  acid  (Medlock,  Girard,  and  De  Laire),  nitrobenzol 
and  iiitrotoluol  (Coupier).  From  100  parts  of  aniline  there  are  obtained  25  to  30 
parts  of  crystalline  magenta. 

Arsenic  Acid  Process. — If  a  mixture  of  the  cliacid  arseniates  of  aniline — 

/OH  (OH 

AsO  -  OH  of  o-  and  ^-toluidine  AsO  \  OH 

(ONH3.C6H5  (O.NH3.C7H7 

is  heated  to  180-190°,  the  acid  is  reduced,  and  there  is  formed  a  mass  of  a  cantharides 
green  colour,  containing  the  magenta  bases :  pararosaniline,  methyl-pararosaniline, 
and  probably  climethyl-pararosaniline ;  the  phosphine  bases  :  chrysaniline  and  methyl- 
chrysaniline ;  and  the  induline  bases :  melaniline  and  mauvaniline,  in  the  state  of 
arsenites  and  arseniates.  The  formation  of  pararosaniline  is  effected  by  oxidising  out 
the  hydrogen  atoms  from  a  mixture  of  i  mol.  paratoluidine  and  2  mols.  aniline  accord- 
ing to  the  following  equation  : — 

(C6H4.NH2  (C6H4.NH, 

TT  n  T 

4  2H.C6H4.NH2  +  03  =  2H20  +  O 


The  formation  of  methyl-pararosaniline  (rosaniline),  and  of  dimethyl-pararosaiiiline 
^rosotoluidine),  ensues  from  corresponding  mixtures  of  bases. 

The  melting-pot  used  in  the  arsenic  process  (Fig.  394),  i  metre  high,  consists, 
according  to  Schoop,  of  cast-iron ;  the  cover  can  be  raised  by  means  of  a  pulley.  The 
exit-pipe  for  the  distillate  is  screwed  to 
one  side.  The  contents  of  the  melting- 
pot  are  kept  in  motion  during  the  process 
by  means  of  an  agitator.  A  smaller 
opening  serves  for  taking  out  specimens 
of  the  melt.  Th«  pan  is  built  up  in  such  ^ 
a  manner  that  the  flame  gases  stream 
through  a  perforated  arch  against  the 
bottom  of  the  pan,  and  thence  pass  up 
uniformly  along  its  sides,  and  are  finally 
led  through  a  ring-shaped  channel  to  the 
chimney. 

The  following  is  the  composition  of  two  approved  aniline  oils  for  reds :- 


Aniline  . 

Orthotoluidine 

Paratoluidine 


A. 
22'0 

58-4 


68-4 


Sp.  gr.     i  -0020 


I'OOOO 


532  CHEMICAL  TECHNOLOGY.  [SECT,  iv, 

The  pan  is  charged  with  700  kilos,  arsenic  acid  at  195°  Tw.  •  300  kilos,  recovered 
arsenic  acid  of  the  same  strength,  300  kilos,  aniline  for  reds,  and  200  kilos,  of  distillate 
from  former  charges.  If  the  pan  is  cold  the  mixture  coagulates  to  a  thick  jelly. 
Generally,  the  pan  is  so  warm  from  former  operations  that  the  mixture  remains  liquid. 
The  fire  is  kindled  at  6  A.M.,  so  that  the  distillation  begins  at  t  or  2  P.M.  After 
twenty  hours  (when  20  to  25  jugs  of  distillate  have  been  collected)  the  fire  is  raised 
until  20  litres  distil  over  hourly.  After  400  litres  in  all  have  passed  over,  the  melt 
•will  have  become  thick.  Samples  are  now  taken  frequently,  and  the  melt  is  broken  up 
as  soon  as  it  becomes  pasty.  The  cover  is  quickly  drawn  up  and  the  contents  are  baled 
out  upon  sheet-iron  trays  by  means  of  copper  scoops.  The  melting  takes  thirty- six 
hours.  As  soon  as  the  melt  becomes  pasty  the  fire  is  only  kept  up  faintly,  as  the 
heat  of  the  pan  is  sufficient  to  complete  the  reaction.  Only  prolonged  experience 
enables  the  operator  to  judge  when  the  melting  should  be  stopped.  If  the  melt  is  too 
thin  the  yield  will  be  low ;  if  it  has  become  too  thick  it  is  a  hard  task  to  dig  it  out  of 
the  pan  with  chisels.  During  baling  out,  the  copper  scoops  are  frequently  plunged 
into  cold  water  to  prevent  the  melt  from  adhering.  The  workman  protects  himself 
during  baling  out  against  the  dense  aniline  vapours  by  a  sponge  moistened  with  acetic 
acid  and  fixed  over  the  mouth  and  nostrils.  The  operator  is  also  changed  every  two  or 
three  minutes.  The  melt  when  cold  is  broken  up  into  pieces  the  size  of  a  fist.  The 
average  weight  is  88'6  kilos.  The  fracture  of  the  melt  is  conchoidal,  it  is  brittle,  and 
has  a  golden  lustre.  The  distillate  is  collected  in  a  large  parting  funnel,  and  there  are 
added  to  it  100  kilos,  of  salt.  The  oil  then  rises  readily  to  the  surface;  the  solution 
is  drawn  off  and  diazotised  after  the  proportion  of  aniline  present  has  been  ascertained, 
precipitated  with  a  solution  of  naphthol  and  worked  up  for  naphthol  orange.  The 
stratum  of  oil  is  rectified  in  a  still  and  used  for  future  melts.  The  distillates  from  the 
red  oils  A  and  B  contain  respectively : 

A.  B. 

Aniline        .         .         .     29  per  cent.  ...         21  per  cent. 

Orthotoluidine    .         .71         ,,  ...         79        „ 
Paratoluidine                ,     —  — 


Sp.  gr.  at  18°     1-0076  1*0057 

The  distillates  may  be  worked  up  more  advantageously  for  safranine  (see  below). 
On  an  average  a  melt  yields  220  kilos,  of  distillate. 

The  melt  is  now  ground  up  wet  to  a  fine  mud,  for  which  two  hours  are  generally 
required.  The  mud  is  let  off  into  a  monte-jus  and  passed  through  a  filter-press. 
Whilst  the  filtrate  is  concentrated  in  an  iron  pan,  to  recover  the  arsenic  acid,  the  press- 
cakes  are  stirred  up  with  lukewarm  water  and  filtered  again.  The  filtrate  now 
obtained  is  used  in  grinding  up  the  next  melt.  As  a  matter  of  course  the  melt  is 
ground  up  in  small  lots  of  about  100  kilos,  each.  The  crude  melt  after  being  thus 
treated  is  a  greenish-yellow  powder,  which  is  twice  subjected  to  a  lixiviation  with 
boiling  water  in  the  extraction  pan  (Figs.  395  and  396).  Whilst  the  melt  was  formerly 
baled  in  open  vessels  by  means  of  steam,  and  afterwards  in  closed  horizontal  cylinders, 
which  allowed  of  extraction  at  a  slight  pressure,  upright  lixiviators  are  now  preferred. 

This  vessel  consists  of  a  cast-iron  foot-piece  with  an  opening  for  introducing  the 
pulverised  melt,  and  can  be  closed  with  the  lid  D  running  upon  rails.  On  the  semi- 
globular  bottom  of  this  foot-piece  there  are  three  inlets  for  steam,  e,  of  37  mm. 
diameter,  arranged  symmetrically  and  fed  from  the  common  steam  pipe,  d.  A  little 
higher  is  the  inlet  for  water,  w,  and  at  the  lowest  point  the  outflow,  a.  The  cover,  D, 
which  closes  the  circular  feeding-hole  is  secured  with  screws,  and  is  provided  Avith  a 
stuffing  box,  which  serves  for  the  axle  of  the  agitator,  R,  which  is  occasionally  moved 
by  hand.  Above  the  foot-piece  rises  the  upper  cylindrical  part  of  the  apparatus, 


SECT.    IV.] 


BENZOL  COLOUKS. 


533 


Fig.  395- 


Fig.  396. 


riveted  together  with  boiler  plates,  which  is  closed  above  with  a  slightly  arched  cover. 
At  about  three-quarter  height  of  the  entire  apparatus  is  a  small  escape-cock  which 
shows  the  height  to  which 
the  pan  is  filled  with  water. 
In  addition  there  is  a  mano- 
meter attached  to  the  cover, 
to  indicate  the  pressure  within. 
The  upper  portion  of  boiler 
plate  is  screwed  down  to  the 
foot-piece.  The  entire  appa- 
ratus, which  is  i  metre  in 
diameter  and  4^  metres  in 
height,  rests  by  means  of  its 
lower  hemispherical  part  upon 
a  solid  frame  of  wood.  At 
three-quarters  height  the  ap- 
paratus passes  through  a  second 
frame  to  prevent  vibration. 

For  continuous  working  two  such  extractors  are  conveniently  placed  side  by  side. 
It  is  convenient  to  divide  the  crude  melt  into  10  equal  parts.  Each  part — i.e.,  88'6  kilos. 
— is  ground  up  separately,  and  the  lixiviated  powder  is  placed  in  the  extractor.  The 
cover  is  closed,  and  water  is  run  in  till  it  runs  out  at  the  upper  cock.  This  cock  is 
then  closed  and  steam  is  turned  in.  The  quantity  of  liquid  is  about  3600  litres.  When 
the  water  boils  the  supply  of  steam  is  so  regulated  that  the  manometer  shows  i  \  to  2 
atmospheres.  After  four  hours  (altogether)  the  decoction  is  passed  through  the  filter- 
press,  and  the  filtrate  is  run  into  a  large  cistern.  The  residue  is  now  placed  in  the 
second  extraction  pan,  and  again  treated  with  3600  litres  in  the  same  manner.  This 
second  liquor  is  now  transferred  to  the  first  apparatus,  which  has  been  already  charged 
with  a  fresh  portion  of  melt,  so  that  the  fresh  melt  is  always  extracted  with  the  second 
extract  of  the  former  charge.  The  doubly  extracted  residue,  a  powder  resembling 
humus,  forms  a  part  of  the  poisonous,  useless  magenta  residues. 

The  colour  liquor  of  one  decoction  (about  3600  litres)  deposits  a  little  impurity  on 
standing  for  half-an-hour.  It  is  let  off  into  an  apparatus  placed  below,  and  whilst 
still  hot  is  stirred  up  with  200  kilos,  of  rock-salt.  The  colouring  matter  is  now- 
converted  into  a  hydrochlorate,  and  is  very  completely  deposited  owing  to  the  presence 
of  salt.  The  liquid  drawn  off  after  two  days  is  collected  in  a  large  cistern,  and  the 
colouring  matter  remaining  is  precipitated  from  time  to  time  by  means  of  a  little  milk 
of  lime ;  it  is  filtered  off  and  worked  up  separately.  The  lye  now  obtained,  containing 
much  arsenious  acid,  should  be  completely  precipitated  with  lime  to  remove  the  arsenic. 
This  is,  unfortunately,  often  not  done  at  all,  or  at  least  very  imperfectly,  so  that  the 
poisonous  waters  enter  the  rivers  and  occasion  extraordinary  pollution.  The  lime  to 
be  obtained  in  this  manner  is  of  considerable  bulk,  and  forms  the  second  and  larger 
portion  of  the  poisonous  residues. 

The  crude  magenta  after  being  salted  out  has  to  be  purified.  Along  with  several 
rosanilines — chrysaniline,  mauvaniline,  violaniline — it  contains  further  constituents  not 
yet  understood.  The  separation  of  these  ingredients  depends  on  a  systematic  fractional 
precipitation.  The  crude  magenta  from  two  extractions  (  =  \  of  a  melt)  is  dissolved  in 
a  wooden  vat  in  1000  litres  of  water  boiled  by  steam.  To  the  boiling  water  there  are 
added  gradually  40  litres  of  a  solution  obtained  by  dissolving  40  kilos,  soda-ash  in  100 
litres  water.  A  part  of  the  colouring  matter  separates  out  as  a  green  or  golden 
shining  resin  on  the  sides  of  the  vat  and  on  the  surface  of  the  liquid.  The  resin  is 
skimmed  off,  and  the  liquid  is  rapidly  poured  through  a  coarse  sieve  into  a  wooden  butt. 


534  CHEMICAL   TECHNOLOGY.  [SECT.  iv. 

To  the  filtrate  there  are  added  2  litres  hydrochloric  acid  to  prevent  the  separation  of 
chrysaniline,  and  to  delay  the  crystallisation  of  the  magenta.  There  is  laid  upon 
the  surface  of  the  liquid  a  cover  with  a  number  of  wooden  rods,  by  which  means  the 
cooling  takes  place  more  slowly.  When  the  lid  is  taken  off  after  the  lapse  of  two  days- 
it  is  found  covered  with  a  layer  of  fine  crystals.  The  lye  is  run  into  a  cistern,  and  the 
crystals  adhering  to  the  sides  and  the  bottom  are  allowed  to  drop  off.  These  crystals  are 
let  dry  first  in  the  air,  and  then  in  a  drying-room  at  40°.  In  this  manner  20  kilos,  of 
magenta  crystals  are  obtained,  while  about  4  kilos,  of  magenta  remain  in  the  mother 
liquor,  and  the  weight  of  the  resin  eliminated  is  15  to  1 6  kilos.  The  mother  liquor 
from  the  crystallisation  is  precipitated  with  soda-lye,  and  the  coloured  base  deposited 
as  a  brownish-red  mud  after  about  40  kilos,  (calculated  on  the  dry  matter)  have 
accumulated,  is  dissolved  in  hydrochloric  acid.  This  solution  is  treated  exactly  as  in 
the  purification  of  the  crude  magenta  liquor ;  i.e.,  about  ^  of  the  colouring  matter  is- 
separated  out  as  resin  by  the  addition  of  soda-lye ;  the  filtrate  on  cooling  yields  a  crop 
of  magenta  crystals.  In  this  mother  liquor  there  remains  very  much  chrysaniline 
along  with  a  smaller  portion  of  magenta.  By  precipitation  with  soda-lye,  filtering  and 
concentrating  the  base  with  acetic  acid,  we  obtain  cinnamon  brown. 

The  resin  separated  on  purifying  the  crude  magenta  (resin  I.)  is  dissolved  in  hydro- 
chloric acid.  On  boiling  the  acid  liquor  a  little  resin  separates  out,  chiefly  mauvaniline. 
By  the  cautious  addition  of  soda-solution  a  portion  of  colouring  matter  is  separated  out,, 
and  the  mother  liquor  (after  filtration  and  cooling)  yields  a  further  quantity  of 
magenta.  The  mother  liquor  from  this  crystallisation  is  mixed  with  the  resin  I. 
Resin  II.,  obtained  on  purifying  resin  I.,  is  dissolved  in  hydrochloric  acid,  and  the  acid' 
liquor  is  boiled,  when  some  mauvaniline  again  separates  out  and  is  removed.  The  hot 
solution  is  mixed  with  salt,  when  cerise  is  precipitated.  It  is  filtered,  and  the  coloured 
base,  after  washing,  is  neutralised  with  hydrochloric  acid  and  concentrated  by  steam  in 
iron  pans.  It  is  then  the  cerise  of  commerce. 

In  the  filtrate  from  the  precipitate  of  cerise  the  magenta  remaining  in  solution  is 
precipitated  by  soda-lye,  and  the  base  obtained  is  mixed  with  the  resin  II.  remaining 
from  resin  I.  The  more  or  less  complete  separation  of  the  bye-products  depends  on  the 
demands  of  the  market.  The  required  tones  of  magenta,  cerise,  cinnamon  brown, 
maroon,  &c.,  are  prepared  by  mixing  suitable  products.  Mauvaniline  (along  with 
violaniline)  is  an  almost  worthless  product,  and  is  very  seldom  made  soluble  by  treat- 
ment with  fuming  sulphuric  acid,  but  is  more  frequently  neglected. 

In  order  to  test  a  magenta  for  the  presence  of  chrysaniline  a  portion  is  dissolved  in. 
hot  water.  A  little  hydrochloric  acid  is  added  and  zinc  dust  in  small  portions  until 
the  red  colour  has  disappeared.  The  reduction  is  promoted  by  heat.  Magenta  free 
from  chrysaniline  dissolves  to  a  clear,  colourless  liquid,  whilst  the  presence  of 
chrysaniline  gives  a  more  or  less  distinct  yellowness. 

The  arsenic  process  is  said,  as  compared  with  the  nitrobenzol  process  to  have  the- 
advantage  that  the  quantity  of  bye-products  is  considerable  enough  to  render  it  more 
profitable.  In  the  meantime  the  nitrobenzol  process  yields  a  very  fine  maroon,  fully 
equal  to  that  obtained  by  the  arsenical  process.  Except  for  the  production  of  acid 
magenta,  that  obtained  according  to  the  above  described  process  is  only  suitable  for 
nferior  rosaniline  blues  of  a  reddish  cast.  Neither  cotton  blue  nor  Nicholson  blue 
can  be  obtained  from  it  in  a  satisfactory  manner. 

Coupler's  process  for  magentas,  which  has  been  carried  on  for  years  at  the  colour- 
works  at  Hoechst  on  the  Main,  at  the  Berlin  Joint  Stock  Aniline  Co.,  and  elsewhere, 
avoids  the  use  of  arsenic  acid,  and  is  founded  on  the  oxidising  action  of  nitrobenzol 
containing  nitrotoluol  upon  aniline  oil  in  presence  of  iron  and  hydrochloric  acid.  An 
enamelled  pan,  fitted  with  an  agitator  and  an  outflow  pipe,  is  charged  with  38  kilos, 
aniline  oil,  17  to  20  kilos,  nitrobenzol,  18  to  22  kilos,  hydrochloric  acid,  and  2  to  2^  kilos.. 


SECT,  iv.]  BENZOL   COLOURS.  555 

iron  turnings.  The  pan  is  heated  to  180°,  with  stirring,  for  four  to  five  hours.  The  crude 
melt,  scooped  out  upon  sheet-iron  trays  with  iron  ladles,  still  contains  25  per  cent,  of 
aniline.  It  is  dissolved  in  water,  the  rosaniline  is  separated  with  common  salt,  and 
the  unconverted  aniline  is  distilled  off  from  the  lye  after  the  addition  of  lime.  The 
formation  of  this  rosaniline  (Briining's  red,  Coupier  red,  nitrobenzol  red)  may  be 
represented  by  the  following  equation : 

2C7H7.NH2  +  C8H6.NO,  =  C20H19N3  +  2H20. 

Lange  observes  that  in  the  nitrobenzol  magenta  process  the  nitro  compounds  have 
merely  an  oxidising  action,  or  if  they  contain  methyl  groups  they  participate  in  the 
formation  of  rosaniline  in  so  far  only  as  they  furnish  the  atom  of  carbon  necessary  for 
the  production  of  carbinol. 

The  salts  of  rosaniline  have  mostly  in  reflected  light  the  green  metallic  lustre 
of  the  elytra  of  certain  beetles  (Cetoniadce,  <fec.),  whilst  by  transmitted  light  they 
appear  red.  The  hydrochlorate  was  formerly  called  fuchsine,  the  acetate  roseine,  and 
the  nitrate  azaleine.  The  salt  obtained  by  the  action  of  mercuric  nitrate  was  called 
rubine.  Their  solutions  in  water  have  the  splendid  shade  well  known  as  magenta.* 

Its  tinctorial  power  is  very  great ;  t  kilo,  of  magenta  suffices  for  200  kilos,  of  wool. 
Aniline  tannate  is  sparingly  soluble  in  water.f 

Rosaniline  is  the  basis  of  most  of  the  other  aniline  colours ;  thus  blue  and  violet 
colouring  matters  (alkylised  rosanilines)  may  be  produced  from  the  rosanilines  by 
partially  or  entirely  replacing  the  amidohydrogen  atoms  by  alcohol  radicles.  More 
recently,  however,  some  of  these  alkylised  rosanilines  are  preferably  obtained  by  intro- 
ducing the  alkyl  (e.g.,  methylaniline),  not  into  the  pre-formed  rosaniline,  but  into  the 
aniline  and  toluidine,  which  is  then  submitted  to  oxidation  for  obtaining  alkylised 
rosaniline. 

Acid  magenta,  Rubine  S,  or  acid  rubine,  consist  of  mixtures  of  the  sodium  or 
ammonium  salts  of  the  pararosaniline  and  rosaniline  trisulpho  acids  ;  according  to — 

(C6H3.NH,.S03Na  (C6H2.CH3.NH2.S03Na 

HO.CJC6H3.NH^S03Na  and  HO.c|C6H2.CH3.NH2.SO3Na 

C6H3.NH2.S03Na  tC6H2.CH3.NH2.S03Na 

It  is  obtained  by  heating  magenta  with  fuming  sulphuric  acid  to  168°  to  170°, 
pouring  into  much  water,  supersaturating  with  milk  of  lime,  and  treating  the  solution 
with  soda  after  removing  the  gypsum.  The  sodium  salt  obtained  on  evaporation  is 
readily  soluble  in  water,  and,  unlike  ordinary  magenta,  dyes  in  a  strongly  acid  bath. 

Aniline  Slue. — If  rosaniline  is  heated  with  about  10  parts  of  aniline  and  a  little 
benzoic  acid  (the  action  of  which  is  not  yet  understood)  to  the  boiling  point,  ammonia 
escapes,  and  the  excess  of  aniline  distils  over — 

C20H10N3  4-  3C6H5.NH2  =  C20H19(C6H5)3N3  +  3NH3. 

The  residue  is  neutralised  with  hydrochloric  acid;  triphenylrosaniline  hydro- 
chlorate  is  insoluble  in  water  (though  the  excess  of  aniline  dissolves  as  hydrochlorate), 
but  more  readily  soluble  in  spirit  (spirit  blues). 

If,  in  like  manner,  aniline  is  allowed  to  act  upon  a  mixture  of  pararosaniline  and 
rosaniline,  we  obtain  a  mixture  of  the  hydrochlorates,  sulphates  or  acetates  of  triphenyl- 
rosaniline and  triphenylpararosaniline  occurring  under  the  trade  names  of  aniline 
spirit  blue,  gentian  blue,  opal  blue,  and  light  blue — 

*  Magenta  is  soluble  in  acetic  acid,  in  alcohol,  in  glycerine,  and  in  solutions  of  alkaline 
bicarbonates.  By  acids  the  colour  is  turned  more  on  the  blue  side,  but  is  apt  to  be  dulled  and 
impoverished. 

t  Magenta,  like  many  other  coal-tar  colours,  is  apt  to  be  sophisticated  with  sugar  and  dextrine. 


536  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

(C6H4.NH.C6H5  (C6H3.CH3.NH.C6H5 

C  C6H4.NH.C6H5      and   C  C6H4.NH.C6H5 
(C6H4.N.C6H..HC1  IC6H4.N.C6H5.HC1 

To  render  aniline  blue  soluble  in  water  it  is  treated  with  concentrated  sulphuric 
acid.  The  mixture  of  sodium  salts,  of  triphenylrosaniline,  monosulpho  acid,  and 
triphenylpararosaniline  monosulpho  acid,  occurs  in  trade  under  the  names  of  Nicholson 
blue,  alkali  blue,  and  soluble  aniline  blue.  If  it  contains  also  disulpho  acids  we  have — 
water  blue,  China  blue,  and  marine  blue.  If  aniline  is  heated  to  250°  with  aniline 
hydrochlorate  we  obtain  diphenylamine  hydrochlorate  (C6H5)2NH.HC1.  The  diphenyla- 
mine  on  heating  with  oxalic  acid  to  i2o°-i3O°  yields  triphenylpararosaniline — 
3(C6H5)2NH  +  H,C204  =  C19H14(CeH5)3N3  +  CO  +  3NfO. 

The  hydrochlorate  is  sold  as  spirit-diphenylamine  blue,  or  Bavarian  blue,  and  is 
distinguished  from  aniline  blue  merely  by  the  absence  of  triphenylrosaniline.  When 
rendered  soluble  by  treatment  with  concentrated  sulphuric  acid  the  sodium  salts  are 
sold  as  alkali  blue  D,  and  Bavarian  blue  D  S  F. 

According  to  De  Laire  andGirard  (1866),  the  mixture  of  aniline  and  aniline  hydro- 
chlorate  is  heated  in  an  enamelled  cast-iron  autoclave  for  twenty-four  hours,  at  a 
pressure  of  3  to  4  atmospheres  and  a  temperature  of  250°.  From  time  to  time  the 
ammonia  collecting  in  the  autoclave  must  be  expelled  by  opening  a  cock,  as  otherwise 
the  reaction  might  be  reversed,  and  the  yield  of  diphenylamine  might  be  decreased. 
In  this  manner  the  yield  of  diphenylamine  is  50  per  cent,  of  the  weight  of  the  aniline 
used.  The  mass  taken  out  of  the  autoclave  is  treated  with  strong  hydrochloric  acid 
in  order  to  separate  the  unchanged  aniline  from  the  diphenylamine.  From  six  to  ten 
volumes  of  water  are  now  added,  which  occasions  a  dissociation  of  the  diphenylamine 
salt  into  base  and  acid.  The  base  liberated  collects  on  the  surface  of  the  liquid  as  an 
oily  layer,  which,  when  cold,  is  taken  off,  pressed,  and  distilled.  It  forms  a  solid, 
crystalline,  yellowish-white  mass,  which  melts  at  5o°-55°  and  distils  at  310°.  By 
sulphurising  the  diphenylamine  or  its  alkylised  products,  they  obtain  the  mono-  and 
disulpho-acids,  which,  after  treatment  with  oxidising  agents,  can  be  at  once  used  in 
dyeing  and  printing  for  the  production  of  blacks  and  violets. 

For  producing  alkylised  diphenylamine  various  methods  may  be  adopted — e.g., 
(a)  the  action  of  methyl-chloride  or  nitrate  at  a  temperature  below  100° ;  (b)  the  action 
of  methyl-aniline  upon  aniline  hydrochlorate ;  (c)  the  action  of  methyl-alcohol  upon 
anhydrous  diphenylamine  hydrochlorate ;  (d)  the  action  of  the  nascent  chlorides  of  the 
alcohol  radicles,  i.e.,  by  treating  diphenylamine  with  a  mixture  of  hydrochloric  acid  and 
methyl-alcohol,  when  the  most  important  of  these  bases,  methyl-diphenylamine  : 

(C6H5)2NH  +  C2H8C1  =  (C6H5)2CH3N.HC1, 

is  formed.  The  latter  base  is  obtained  by  heating  100  kilos,  diphenylamine,  68  kilos, 
hydrochloric  acid  of  sp.  gr.  1-2,  and  24  kilos,  methyl-alcohol,  in  an  enamelled  cast-iron 
autoclave  for  eight  to  ten  hours  in  the  oil  bath  at  200°  to  350°  and  bringing  the  mass  in 
contact  with  hot  caustic  soda-lye.  The  crude  base  separates  out  and  is  purified  by 
distillation.  It  boils  at  282°  to  286° ;  its  salts  are  decomposed  by  water.  If  heated  to 
110°  to  120°  along  with  oxalic  acid,  it  becomes  a  blue.  In  a  quite  analogous  manner 
the  bases  ethyl-,  amyl-,  and  benzyl-diphenylamine  may  be  obtained,  which  all  yield  blue 
colouring  matters  on  treatment  with  oxidising  agents. 

For  obtaining  diphenylamine  blue,  soluble  in  water,  one  part  of  one  of  the  sulpho- 
acids  of  diphenylamine  is  heated  in  an  autoclave  with  two  parts  of  oxalic  acid,  at  a 
temperature  not  exceeding  130°.  After  heating  from  eighteen  to  twenty  hours  the  mass 
is  let  cool,  treated  with  boiling  water,  saturated  with  ammonia,  filtered  ;  the  colouring 
matter  is  precipitated  with  sulphuric  acid,  washed  with  acidulated  water,  and  finally 
converted  into  the  salt  desired,  with  ammonia,  soda,  or  lime.  The  blue  solution  is 


SECT,  iv.]  BENZOL  COLOURS.  537 

evaporated  to  dryness  and  the  residue  is  pulverised.  For  silk  there  is  used  the  ammo- 
nium salt,  for  wool  the  sodium  salt,  and  for  cotton  the  calcium  salt. 

Aniline  Violet. — If  rosaline  is  heated  in  an  alcoholic  solution  with  methyl  chloride  or 
iodide,  or  ethyl  bromide,  we  obtain  the  methyl  and  ethyl  derivatives  of  rosaniline, 
the  hydrochlorates,  hydriodates,  or  acetates  of  which  are  known  as  Ilofmann's  violet, 
iodine  violet,  dahlia,  primula,  red  violet,  violet  7?.,  &c.  The  blue  violet  hydrochlorate  of 
triethylrosaniline  corresponds  to  the  formula — 

(C6H3.CH3.NH.C2H5 
C  {C.H4.NH.C,H. 

(C6H4.NH.C2H5C1 

Methyl  Violet  or  Paris  Violet  is  substantially  the  hydrochlorate  of  pentamethylpara- 
rosaniline — 

(C6H4.N(CH3), 
C   C6H4.N(CH3)2 

IC6H4.N(CH3)HC1 

and  is  formed  by  oxidising  dimethylaniline  with  copper  chloride,  which  is  first  mixed 
with  much  sodium  chloride,  then  with  dimethylanine  and  acetic  acid  and  dried  at  50°. 
The  bulk  of  the  sodium  chloride  is  removed  by  means  of  a  little  water,  the  residue  is 
removed  with  water,  the  copper  is  precipitated  by  hydrogen  sulphide,  the  colouring 
matter  is  precipitated  with  much  salt,  and  purified  by  re-crystallisation.  According  to 
the  statement  of  the  Baden  Aniline  Works,  methyl  violet  is  obtained  as  follows  :  Into 
100  kilos  of  dimethylaniline  1 8  or  20  kilos,  of  chlorocarbonic  oxide  are  introduced  at 
20°,  and  after  standing  for  twenty-four  hours,  50  more  kilos,  of  dimethylaniline  and  30 
kilos,  of  powdered  zinc  chloride.  Then,  whilst  constantly  stirring  at  40°  to  50°  chloro- 
carbonic oxide  is  introduced  until  there  is  an  increase  of  20  kilos,  in  weight.  The  reaction 
is  completed  by  heating  for  six  hours  to  50°.  From  the  melt  obtained  the  colouring  base 
is  extracted  in  the  usual  manner  by  supersaturation  with  soda  lye  and  distillation  with 
steam,  and  this  base  is  again  converted  into  a  sulphate.  From  the  hot  solution  of  the 
latter  the  finely  crystalline  hydrochlorate  of  methyl  violet  may  be  obtained  by  an 
addition  of  common  salt.  The  same  method  is  taken  in  obtaining  the  corresponding 
violet  colours  from  diethylaniline  and  methylethylaniline. 

A.  W.  Hofmann  gives  the  following  equations  for  the  formation  of  the  colouring 
matter  obtained  by  the  action  of  phosgene  upon  dimethyl  aniline — 

C6H6N(CH3)2  4  COC12  =  C6H4N(CH3)2COC1  +  HC1. 

C6H4N(CH3)2COC1  +  C6H5N(CH3)2  =  [C6H4N(CH3)2]2CO  +  HC1. 
[C6H4N(CH3)2]2CO  +  COC12          =  [C6H4N(CH3)2]2CC12  +  CO,. 
[C6H4N(CH3)2]2CC12  +  C6H5N(CH3)2  =  [C6H4N(CH3)2]3CC1  +  HCL 
The   hexamethylpararosaniline   is  sold  as  a  hydrochlorate  under  the  names  crystal 
violet,  or  violet  6B. 

Methyl  violet  is  soluble  in  water ;  it  dyes  silk,  wool,  and  cotton  prepared  with 
tannin  and  tartar  emetic. 

If  methyl  chloride  is  heated  in  an  alcoholic  solution  with  benzyl  chloride, 

C6H5.CH2C1, 

and  soda,  a  part  of  the  methyl  groups  are  replaced  by  benzyl  and  the  tone  of  the  colour 
is  turned  more  to  a  blue.  The  hydrochlorate  of  pentamethylbenzylpararosaniline  : 

C6H4.N(CH3)2 


C 


C6H4.N(CH3)2 


(C6H4.N.CH3.C6H5.CH2C1 
is  an  article  of  commerce,  under  the  names  Methyl  violet  6B,  or  Benzyl  violet. 

Aniline  Green. — The  chlormethylhexamethylpararosaniUne  hydrochlorate  is  now  very 
generally  preferred  to   the  chlormethylhexamethylrosaniline  hydrochlorate,  obtained 


538  CHEMICAL  TECHNOLOGY  [SECT.  iv. 

by  the  action  of  methyl  chloride  or  iodide  upon  rosaniline,  the  double  zinc  chlorides  of 
•which  are  met  with  under  the  names,  iodine-green,  night-green,  or  Metternich  green* 
The  double  zinc  chlorides  of  the  former  compound  are  sold  as  methyl  green,  Paris  green,, 
or  light  green.  The  compositions  of  both  are  shown  by  the  formula — 

(C6H4.N(CH3)2  (C6H3.CH3.N(CH3)2 

C  C6H4.N(CH3),.CH3C1  C  C6H4.N(CH3),CH3C1 

iC6H4.N(CH3)2Cl  +  ZnCl2  (C6H4.N(CH3)2C1  +  Zn012 

Methyl  green.  Iodine  green. 

Both  dissolve  in  water,  with  a  blueish-green  colour. 

The  double  zinc  chloride  of  bromethylhexamethylpararosaniline,  which  is  sold  as. 
ethyl  green,  is  obtained  by  the  action  of  bromethyl  upom  methyl  violet.  ^ 

The  bluish-green  sodium  salt  of  tetramethyldibenzylpseudorosaniline  disulpiio- 
acid  is  known  as  fast  green.  The  respective  compositions  of  the  two  coloxirs  are — 

(C6H4.N(CH3)2  (C6H4.N(CH3)2 

C  \  C6H4.N(CH3)2.C2H5Br  HO.C   C6H4.N(CH3)2 
tC6H4.N(CH3)2Cl  +  ZnCl2  (C6H4.N(CH2.C6H4.S03Na)2 

Ethyl  green.  Fast  green. 

Aniline  yellow,  along  with  some  other  colours  prepared  from  aniline,  is  discussed1 
among  the  azo-colours. 

Flavaniline,  obtained  by  heating  acetanilide  with  zinc  chloride,  is  110  longer  an  article 
of  commerce.  It  is  included — as  is  also  the  chrysaline  or  phosphine  obtained — as 
bye-products  of  the  manufacture  of  magenta,  among  the  quinoline  and  acridine 
colours. 

Aniline  Black  is  an  intense  aniline  green,  produced  by  the  slow  oxidation  of 
aniline.  It  is  almost  exclusively  produced  upon  the  fibre,  and  more  generally  in 
printing  than  in  dyeing,  in  the  strict  sense  of  the  word.  A  black  dye  which  can  be 
obtained  in  trade  and  can  be  conveniently  applied  both  in  dyeing  and  printing  does  not 
hitherto  exist.  The  formation  of  aniline  black,  however  obtained,  seems  to  take  place  as 
follows : — 

nC6H5.NH2  =  n(C6H5N)  +  nH2 
Aniline.  Aniline  black. 

According  to  R.  Kayser,  aniline  black  has  the  formula  C12H1002 ;  according  to 
Goppelsroder,  C24H20N4;  according  to  Metzki,  C30H25N5;  and  according  to  Liechti, 
C18H15N3.HC1. 

The  formation  of  aniline  black  by  the  action  of  oxidising  agents  upon  aniline  oil  is 
said  to  have  been  observed  by  Fritsche  as  early  as  1843.* 

As  oxidising  agents  for  obtaining  aniline  black  there  are  used  potassium  chlorate 
and  copper  chlorate,  ammonium  ferrocyanide,  potassium  chromate,  and  latterly,  above 
all  others,  ammonium  vanadate.  One  part  of  the  vanadium  preparation,  in  presence  of 
the  requisite  quantity  of  potassium  chlorate,  can  convert  1000  parts  of  aniline  hydro- 
chlorate  into  black.  The  use  of  aniline  black  is  confined  almost  exclusively  to  cotton 
printing  and  dyeing.  For  woollen  dyeing  it  would  be  requisite  to  bring  it 
into  a  soluble  state  after  the  manner  of  indigo,  which  has  not  hitherto  been  found 
practicable. 

Aniline  black  has  now  for  some  years  been  used  as  a  marking  ink  for  linen,  under 
the  name  jetoline. 

Along  with  magenta  there  figure,  as  representatives  of  the  different  classes  of 
triphenylmethan  colours, 

*  The  practical  discovery  of  the  colour  was  made  by  J.  Lightfoot  in  1863. 


SECT,  iv.]  BENZOL  COLOURS.  539 

Malachite  Green>  Rosolic  Acid,  and  Fluoresceine — • 

n.  (CJL.OH  /C6H3-OH 


0- 


C6H4.N(CH3)2  C  C6H4.OH  0 

(c6H4o 


o 


Malachite  green  Pararosolic  acid.  Fluoresceine. 

as  Hydrochlorate. 

Benzaldehyd  Green  or  Malachite  Green. — This  compound  was  at  first  obtained 
on  Dobner's  process  by  the  action  of  benzotrichloride  upon  dimethylaniline  and  zinc 
chloride,  but  it  is  now  prepared  universally  by  the  oxidation  of  the  tetramethyl- 
diamidotriphenylmethan  obtained  from  benzaldehyde  with  dimethylaniline. 

Oil  of  bitter  almonds,  or  benzaldehyde,  is  now  chiefly  obtained  by  introducing 
chlorine  into  toluol,  and  boiling  the  benzyl  chloride  thus  produced,  C6HS.CH2C1,  with 
copper  nitrate  and  water,  or  by  boiling  the  benzyl  chloride,  C6HS.CHC12  (obtained  on 
passing  chlorine  into  boiling  toluol),  along  with  milk  of  lime.  Benzotrichloride, 
C6H5.CC13,  is  obtained  by  the  prolonged  treatment  of  toluol  with  chlorine. 

Dimethylaniline  is  obtained  by  heating  aniline  and  soda-lye  to  100°  and  gradually 
introducing  chlormethyl,  the  pressure  not  being  allowed  to  rise  above  6  atmospheres — 

C6H5.NH2  +  2CH3C1  +  2NaOH  =  CGH5.N(CH3)2  +  2KaCl-H20. 
Or  aniline  is  heated  under  pressure  with  methyl  alcohol  and  hydrochloric  acid. 
According  to  O.  Miihlhauser,  there  are  placed  in  an  enamelled  cast-iron  autoclave 
60  kilos,  aniline  oil  (for  blues),  45  kilos,  wood  spirit,  and  finally  18  kilos,  hydrochloric 
acid  at  32°  Tw.  When  the  apparatus  is  charged,  the  entrance  is  tightly  closed,  and 
heat  is  applied  by  means  of  an  open  coke-fire. 

On  commencing  the  reaction  at  a  moderate  heat,  the  pressure  in  the  autoclave 
quickly  rises  to  25-28  atmospheres,  at  which  it  is  kept  for  four  to  five  hours.  At  the  end 
of  this  time  the  methylation  of  the  aniline  is  complete,  and  the  autoclave  may  be 
let  cool.  After  the  lapse  of  twelve  hours  the  apparatus  is  still  warm  and  the  pressure 
slight.  The  contents  are  brought  to  the  ordinary  pressure  of  the  atmosphere  by 
gradually  and  cautiously  raising  the  filling  cover,  when  a  current  of  methyl  chloride 
escapes.  The  cover  is  then  unscrewed,  and  in  its  place  a  pipe  is  introduced  for  the  oil 
to  be  forced  out.  This  pipe,  which  can  be  screwed  in  tightly,  and  which  reaches 
to  the  bottom  of  the  autoclave,  is  twofold,  and  allows  on  one  side  admission  for 
compressed  air,  and  on  the  other  an  exit  for  the  contents.  The  warm  liquid  mass 
is  forced  into  a  wooden  tank  lined  with  lead.  For  decomposing  the  hydrochlorate  and 
separating  the  oil,  a  milk  of  lime  is  added,  which  is  prepared  the  previous  day  from  the 
lime  of  20  kilos,  of  marble  ;  agitation  is  kept  up  during  its  introduction.  The  contents 
of  two  autoclaves  are  rendered  alkaline  in  this  manner,  run  into  the  still,  and  the 
cistern  is  washed  out  with  water.  The  still  is  closed,  and  the  oil  is  expelled  by 
heating  over  an  open  fire  and  the  introduction  of  steam.  After  heating  for  two  hours 
the  water  in  the  still  boils,  escapes  and  is  condensed  in  the  refrigerator  along  with  oils 
which  have  been  carried  over.  As  soon  as  the  distillation  of  water  begins,  a  current  of 
steam  is  allowed  to  enter,  and  the  distillation  with  the  aid  of  steam  is  kept  up  briskly. 
After  the  lapse  of  about  five  hours  the  distillation  is  complete  and  all  the  oil  has  passed 
over.  The  operation  is  then  brought  to  an  end  by  shutting  off  the  steam.  The  residue  in 
the  still  is  treated  as  waste ;  a  cock  at  the  bottom  allows  it  to  be  run  off  into  the  drain. 

For  the  separation  of  oil  and  water  a  peculiar  receiver  is  used — a  combination  of 
the  parting  funnel  and  the  Florentine  flask.  The  distillate,  which  enters  the  refri- 
gerator in  a  stream  of  the  thickness  of  a  finger,  passes  into  this  receiver,  and  is  separated 
there  into  an  upper  layer  of  oil  and  a  lower  stratum  of  water.  As  soon  as  the  level  of 
liquid  in  the  receiver  has  reached  the  height  of  the  outflow  opening,  the  water  is  run  off 


540  CHEMICAL   TECHNOLOGY.  [SECT.  iv. 

through  a  tube,  which  reaches  nearly  to  the  bottom  of  the  receiver.  In  this  manner  a 
preliminary  separation  of  the  bulk  of  the  water  from  the  oil  is  effected.  At  the  end  of 
the  distillation  a  complete  separation  of  oil  and  water  is  effected  by  opening  a  cock 
fixed  at  the  lowest  part  of  the  bottom.  The  oil  is  placed  in  an  iron  cylinder  along 
with  dry  salt  in  order  to  remove  the  last  traces  of  water. 

According  to  Miihlhauser,  the  manufacture  of  malachite  green  resolves  itself  into 
four  separate  stages — i.  The  production  of  a  pure,  dry  leuko-base ;  2.  The  oxidation  of 
this  base  into  green,  and  obtaining  it  in  a  solid  form;  3.  The  purification  of  the 
green  colouring  matter,  and  the  production  of  the  green  base ;  4.  The  production  of 
green  crystals.  To  these  processes  there  correspond  four  independent  systems  of 
apparatus  in  addition  to  an  apparatus  for  working  up  the  residues.  For  a  daily  out- 
put of  70  kilos,  there  are  required  : 

An  installation  for  obtaining  the  leuko-base,  consisting  of  three  cast-iron  double 
pans  ;  connection  of  the  outside  pan  to  the  water  and  steam  mains ;  connection  of  the 
cover,  fitted  with  a  man-hole  and  pressure-gauge,  with  the  air-piping  from  the  still, 
and  capable  of  being  heated  by  direct  and  indirect  steam,  as  also  a  worm  cooler,  and 
a  drying-pan  placed  beneath  the  still. 

A  system  of  vats  for  oxidising  the  leuko-base  and  obtaining  the  green  in  a  solid 
state,  consisting  of  an  elevated  vat  for  dissolving  the  leuko-base ;  three  oxidation  butts 
fitted  with  agitators ;  the  precipitating  vats  corresponding  to  these  three  oxidising  vats, 
and  placed  below  them,  with  box  filters  for  previous  and  subsequent  filtration. 

The  purifying  system  consists  of  a  horizontal  pan  provided  with  an  agitator,  and 
containing  3500  litres.  This  pan  has  an  elevated  dome  with  a  man-hole.  A  second 
opening  of  equal  size  is  situate  close  to  the  bottom,  and  serves  for  emptying  the  pan, 
which  has  a  slight  incline.  This  pan  is  in  connection  with  the  water  and  steam 
mains,  and  also  with  a  pressure-filter,  a  cast-iron  chest,  the  inside  bottom  of  which  can 
be  unscrewed.  This  chest  is  divided  into  two  compartments  by  a  strong  cotton  cloth 
in  such  a  manner  that  the  liquid  streaming  in  from  below  under  pressure  allows  only 
dissolved  substances  to  flow  into  the  second  compartment,  but  retains  the  solids.  The 
filtrate  escapes  through  a  side  aperture  in  the  chest,  and  flows  through  a  pipe  into  the 
precipitating  vats,  with  three  filter-chests  placed  below. 

The  system  of  crystallisation  consists  of  a  vat  for  dissolving  the  bases,  of  the 
capacity  of  2000  litres,  and  six  crystallising  vats,  each  of  the  same  size,  and  provided 
with  round  floating  covers  in  several  compartments. 

For  producing  the  leuko-base  there  are  placed  in  the  double  pan,  provided  with  an 
agitator,  100  kilos,  of  dimethylaniline  and  40  kilos,  of  benzaldehyde.  The  mass  is  kept 
in  agitation,  and  there  are  added  within  two  hours  40  kilos,  of  anhydrous  zinc  chloride 
in  powder.  The  pan  is  closed,  and  it  is  heated  to  60°  the  first  day,  to  80°  the  second, 
and  to  100°  on  the  third,  the  water  in  the  outside  kettle  being  brought  to  a  boil.  After 
thus  working  for  three  days  the  condensation  is  completed,  and  the  leukobase  can  be 
separated  from  the  excess  of  dimethylaniline.  A  pressure-pipe  is  placed  in  the  pan, 
and  the  contents,  yet  hot,  are  forced  into  the  still. 

The  mass  in  the  still  is  exposed  to  the  action  of  direct  steam,  which  carries  along 
with  it  the  oil ;  the  steam  and  oil  are  liquefied  in  the  refrigerator  and  collected  in  a 
receiver.  The  distillation  is  continued  until  clean  water  passes  over.  By  opening  the 
outlet-cock  in  the  vaulted  bottom,  the  contents  are  entirely  discharged  into  a  copper 
pan  placed  below,  and  there  allowed  to  cool.  The  liquid  solution  of  zinc  chloride  is 
separated  from  the  supernatant  solid  base  by  means  of  syphons,  washing  lastly  with 
cold  water.  The  solid  base  remaining  in  the  copper  pan  is  melted  by  admitting  steam 
into  the  outer  pan,  and  dried  by  agitation,  which  takes  about  twelve  hours.  The  dry 
liquid  base  is  placed  upon  zinc  plates  in  such  a  manner  that  every  plate  receives  a 
nett  weight  of  33  kilos. ;  any  residue  is  weighed  into  the  next  operation.  The  yield 


SECT,  iv.]  BENZOL   COLOURS.  54t 

from  100  parts  dimethylaniline,  40  benzaldehyde,  and  40  solid  zinc  chloride  is  about 
123  parts. 

In  order  to  remove  the  base  from  the  zinc  plates,  one  plate  with  its  33  kilos,  is 
placed  in  a  small  wooden  vat  holding  400  litres.  The  plate  is  laid  upside  down  upon 
a  steam-worm  in  the  vat  provided  with  many  apertures ;  steam  is  turned  on,  and  the 
base  is  melted  off  the  plate.  When  this  is  done  the  plate  is  removed  ;  about  200  litres 
water  are  run  into  the  vat  and  heated  to  a  boil,  so  that  the  base  melts.  To  the  boiling 
mixture  are  added  25  kilos,  hydrochloric  acid  at  32°  Tw.,  a  quantity  which  suffices  for 
complete  solution.  If,  on  pouring  a  sample  into  water,  there  still  remains  a  white 
milky  turbidity  of  basic  salt,  a  little  more  acid  is  added,  until  all  the  test  shows 
complete  solution — i.e.,  a  sample  poured  into  water  remains  clear,  and  all  the  leuco- 
base  is  converted  into  a  bi-acid  salt.  The  clear  solution  is  run  into  a  vat  placed 
below,  containing  1000  litres  water,  and  is  mixed  with  31  kilos,  of  acetic  acid  of 
40  per  cent.,  with  thorough  agitation.  For  obtaining  the  lead  peroxide  there  are  used 
67  kilos,  litharge,  125  kilos,  acetic  acid  at  40  per  cent.,  and  81  kilos,  chloride  of  lime. 
The  dark-brown  paste  produced  is  placed  in  a  cask,  and  made  up  to  a  nett  weight  of 
1 68  kilos,  by  the  addition  of  water.  The  whole  is  then  divided  into  three  small  tubs, 
so  that  in  each  tub  there  are  exactly  56  kilos,  of  paste,  corresponding  to  33  kilos,  of 
leucobase. 

For  producing  the  green  there  is  placed  in  each  of  the  vats  its  portion  of  peroxide 
paste,  which  is  thoroughly  mixed  up  in  five  to  ten  minutes  by  means  of  the  agitator. 
The  solution  is  then  a  deep  green. 

In  order  to  precipitate  the  paste  in  the  small  dissolving-vat  placed  above  the 
oxidation- vats,  72  kilos,  sodium  sulphate  are  dissolved  in  200  litres  of  water,  and  made 
up  to  a  volume  of  300  litres.  Immediately  after  the  oxidation  100  litres  of  the  solution 
of  sulphate  are  let  run  into  each  of  the  three  oxidising  vats  with  vigorous  stirring.  The 
sodium  sulphate  precipitates  all  the  lead  as  a  sulphate.  It  is  allowed  to  settle  for  twelve 
hours,  and  filtered  the  next  day  into  the  precipitating- vats  through  a  chest  lined  with  felt. 

For  precipitating  the  colouring  matter,  the  green  is  first  converted  into  the 
sparingly  soluble  double  zinc  salt.  As  this  double  zinc  chloride  is  sparingly  soluble 
even  in  a  dilute  solution  of  zinc  chloride,  it  is  mixed  with  an  excess  of  zinc  chloride,  and 
then  completely  salted  out  with  common  salt.  Into  each  vat  there  are  stirred  in,  first, 
20  kilos,  of  zinc  chloride,  and  the  double  zinc  salt  is  completely  salted  out  by  adding 
175  kilos,  of  common  salt,  which  is  also  stirred  in.  The  precipitation  is  complete  as  soon 
as  a  drop  of  the  liquid  applied  with  a  glass  rod  to  a  slip  of  filter-paper  no  longer  shows 
a  coloured  margin.  All  three  vats  are  treated  in  the  same  manner ;  allowed  to  stand  for 
twelve  hours,  and  finally  passed  through  a  chest-filter.  The  residue  is  drained,  and 
consists  of  a  moist  mixture  of  double  zinc  salt,  resin,  and  excess  of  salt. 

To  separate  the  double  zinc  salt  from  the  accompanying  matters  the  mass  is  stirred 
up  with  hot  water  in  a  large  horizontal  boiling-pan.  For  this  purpose  it  is  conveyed 
into  2400  litres  of  hot  water,  keeping  the  agitator  in  action,  boiled  for  ten  minutes,  and 
about  500  litres  of  cold  water  are  run  in  to  separate  out  the  resin,  which  at  the  high 
temperature  had  dissolved  along  with  the  green.  The  pan  is  closed  and  left  at  rest  for 
ten  minutes.  The  resin  has  in  the  meantime  been  chiefly  deposited  and  may  be  filtered 
off,  forcing  the  liquid  through  a  filter  press  by  means  of  compressed  air.  The  filtrate 
runs  into  a  wooden  vat,  where  it  is  let  cool  down  to  40°,  and  is  then  precipitated  by 
stirring  in  100  kilos,  ammonia. 

If  the  temperature  is  attended  to,  we  thus  reach  the  precipitation  of  the  base  in  a 
melted  state,  without  including  the  zinc  hydroxide,  which  is  completely  dissolved.  The 
)iquor  is  filtered  into  an  iron  cistern  and  passed  on  to  the  ammonia  still;  the  greyish- 
white  base  is  packed  in  bags  and  drained  in  the  centrifugal.  The  yield  of  moist  base 
is  82 £  kilos. 


542 


CHEMICAL  TECHNOLOGY. 


[SECT.  rr. 


Leuko- 
base. 

HC1  at  32° 
Tw. 

Acetic 
Acid  40 
per  cent. 

PbO 

Acetic 
Acid  40 
per  cent. 

Chloride 
of  lime. 

Salt 
cake. 

NaCl 

ZnClii 

Ammonia. 

Yield  of 
moist 
base. 

3><33 

3x25 

3X31 

67 

125 

81 

72 

3X175 

3X20 

I  GO 

84.0 

3><33 

3X25 

3X31 

67 

"5 

81 

72 

3X175 

3  x  20 

100 

85.0 

3><33 

3X25 

2x31 

67 

125 

81 

72 

3X175 

3x20 

IOO 

82.5 

Along  with  the  green  base  there  is  obtained  the  insoluble  residue  of  double  zinc 
chloride. 

For  crystallising  we  dissolve  in  a  wooden  vat  holding  2000  litres  120  kilos,  of  oxalic 
acid  in  1200  litres  of  water,  promoting  solution  by  heating  to  a  boil ;  100  kilos,  of  base 
are  then  added,  which  dissolves  in  the  oxalic  acid.  The  volume  of  the  liquid  is  made 
up  to  1800  litres,  and  it  is  filtered  into  a  tall,  slightly  conical  cask,  holding  2000  litres. 
Into  the  liquid,  which  has  a  temperature  of  80°,  there  are  stirred  30  kilos,  of  ammonia 
at  20  per  cent,  in  a  thin  stream,  and  the  surface  is  covered  with  boards  cut  to  fit, 
which  float  upon  the  liquid  and  are  adapted  to  the  circular  form  of  the  cask. 

The  separation  of  the  crystals  ensues,  chiefly  not  at  the  bottom,  but  on  the  sides 
and  on  the  lid.  The  crystallisation  is  broken  off  as  soon  as  the  temperature  within  the 
cask  has  fallen  to  18°.  If  it  were  allowed  to  cool  down  lower,  ammonium  oxalate  would 
separate  out  and  would  contaminate  the  green  in  a  very  unpleasant  manner.  In  order 
to  separate  the  crystals  from  the  mother  liquor  the  floating  boards  are  removed  and  a 
spigot  at  the  bottom  is  withdrawn.  The  crystals  are  left  in  a  felt  filter  through  which 
the  liquid  has  to  pass. 

The  crystals  are  first  taken  away  from  the  bottom,  and  those  on  the  sides  are  scraped 
down.  The  crystals  from  the  sides  and  the  cover  are  mixed  on  a  filter,  and  those  from 
the  bottom  are  kept  separate.  After  drainage  on  the  filters  the  crystals  are  packed  in 
woollen  bags  and  drained  in  centrifugals.  The  size  of  the  crystals  depends  on  the 
position  of  the  crystallising  vats,  and  the  thickness  of  the  wood-work.  The  vats  should 
be  set  in  places  free  from  agitations  or  shocks,  such  as  might  be  produced  from  steam 
engines,  pumps,  &c.,  and  must  be  on  the  firm  ground. 

The  thickness  of  the  wood  must  not  be  excessive.  If  such  is  the  case  the  crystals 
are  too  large  and  are  open  to  all  the  defects  of  large  crystals.  The  crystals  after  being 
whizzed  are  finally  uniformly  distributed  over  a  fine  sieve  to  prevent  them  from  ad- 
hering together,  and  are  dried  at  5o°-6o°  in  a  drying  stove.  The  yield  is  70  kilos. 

As  bye-products  are  obtained,  during  the  condensation,  the  oil  driven  off  and  a  lye 
containing  zinc  chloride ;  from  the  oxidation,  a  mixture  of  lead  sulphate  and  a  little 
colouring  matter ;  on  dissolving  the  crude  colouring  matter,  the  double  salt  of  zinc 
containing  resin  and  adhering  colouring  matter ;  on  precipitating  the  base  from  the 
solution  of  the  double  chloride,  a  lye  containing  ammonia ;  lastly,  from  the  crystallisation, 
a  mother  liquor  from  which  oxalic  acid  and  a  quantity  of  good  base  may  be  recovered. 

About  70  kilos,  of  "  driven-off  oil,"  the  yield  of  10  lots,  are  once  more  distilled  with 
direct  steam,  separated  from  water  in  a  cylindrical  pan,  and  dried  with  anhydrous 
sodium  chloride.  The  dimethylaniline  thus  obtained  is  used  in  a  fresh  condensation. 

The  solution  of  zinc  chloride  drawn  off  from  the  leuko-base  is  filtered,  and  after  it 
has  been  brought  up  to  50  per  cent.  ZnCl2  by  the  addition  of  solid  zinc  chloride,  it 
serves  for  salting  out  the  green. 

The  lead  residues  from  ten  lots  are  boiled  up  in  a  tub  with  2000  litres  of  water, 
allowed  to  settle  and  filtered  when  cold.  The  saline  matter  liquor  is  separated  by 
filtration.  The  double  salt  remaining  on  the  filter  is  worked  up  for  green  crystals  with 
a  succeeding  lot.  The  lead  sulphate,  after  again  boiling  up  with  water  to  which  a 
little  sulphuric  acid  has  been  added,  is  filtered  and  dried,  and  is  used  as  such. 


SECT,  iv  1  BENZOL  COLOURS.  543 

200  kilos,  of  moist  double  zinc  chloride  residues  are  stirred  into  2000  litres  of  boiling 
\vaier  and  mixed  with  20  kilos,  of  hydrochloric  acid.  After  boiling  for  30  minutes  it 
is  let  settle  and  filtered  into  a  vat  below.  From  the  filtrate  the  base  is  separated  out 
with  soda.  The  residue  in  the  boiling  vat,  consisting  of  resin  and  residues  of  salt,  is 
thrown  away.  The  base  separated  out  by  soda  is  worked  up  for  liquid  green  or  so-called 
'marine  Hue. 

The  lye  containing  ammonia  is  treated  for  ammonia. 

The  mother-liquor  separated  from  the  crystals  is  heated  to  80°  in  a  vat  and  mixed 
with  soda-lye  until  it  has  a  slight  alkaline  reaction.  The  green  base  separates  as  a 
dense  resin,  which  incloses  but  little  oxalates.  It  is  allowed  to  cool,  and  filtered.  'The 
filtrate  (sodium  oxalate)  is  mixed  with  calcium  chloride  and  worked  up  for  calcium 
oxalate,  which  is  filtered,  and  after  again  being  boiled  in  water,  and  being  passed 
through  the  filter  press,  it  goes  back  into  work  for  the  recovery  of  oxalic  acid.  The 
resinous  base  from  the  mother  liquor  is  boiled  out  with  water,  and  after  separation  from 
the  washing  water  it  is  converted  into  green  or  navy  blue. 

Production  of  Liquid  Colour. — The  base  from  the  mother  liquor,  or  that  from 
working  of  the  double  zinc  residues,  is  first  mixed  with  an  equal  weight  of  the  strongest 
hydrochloric  acid  and  heated  on  the  water  bath  in  an  enamelled  pan.  The  melt 
obtained  is  baled  into  water  at  50°,  with  stirring.  Resinous  products  separate  and  the 
.green  remains  in  solution.  After  standing  for  about  a  day  it  is  filtered  into  a  tub,  in 
which  the  base  is  precipated  by  ammonia  with  the  aid  of  heat.  The  base  thus  purified 
serves  for  the  production  of  colours. 

Liquid  Green. — 50  kilos,  of  the  base  just  mentioned  are  dissolved  in  40  kilos,  of 
hydrochloric  acid  and  150  litres  water,  allowed  to  cool,  and  filtered.  The  filtrate  is 
slightly  acidified,  if  necessary,  and  made  up  with  distilled  water  to  the  tone  of  a  green 
solution  obtained  with  20  grammes  crystal  green  in  80  grammes  water.  This  solution 
is  sold  as  liquid  green. 

For  so-called  "navy  blue"  50  kilos,  of  base  are  dissolved  in  40  kilos,  of  hydro- 
chloric acid  and  150  litres  of  water,  and  filtered  when  cold.  The  filtrate  is  again 
heated,  and  mixed  with  22^  kilos,  violet  36,  which  is  sprinkled  in  while  stirring,  and 
dissolved.  The  solution  is  made  up  with  distilled  water  to  250  litres  and  filtered  when 
cold.  It  is  sold  under  the  names  liquid  indigo  blue  (!),  navy  blue,  cotton  blue,  &c. 

Malachite  green  is  sold  as  oxalate,  2C23H24N2.3C2H204,  or  as  the  double  zinc 
chloride,  3C23H24N2.HC1  +  2  ZnCl2+  2  H2O,  by  the  names  malachite  green,  bitter  almond 
green,  Victoria  green,  fast  green  and  solid  green.  It  is  soluble  in  water  with  a  bluish- 
green  colour. 

Helvetia  green,  formed  by  sulphurising  malachite  green,  has  disappeared  from  the 
market. 

For  obtaining  brilliant  green,  emerald  green,  new  Victoria  green,  the  procedure  is  very 
similar  to  that  for  malachite  green.  60  kilos,  of  diethylaniline  are  heated  with  22 
kilos,  of  benzaldehyde  and  32  kilos,  of  dry  oxalic  acid.  The  leukobase  is  dissolved  in 
Tiydrochloric  acid,  acetic  acid  is  added,  and  it  is  oxidized  with  a  paste  of  lead  peroxide. 
After  throwing  down  the  lead  as  sulphate,  it  is  filtered,  and  the  green  is  obtained  from 
the  filtrate  in  the  form  of  a  zinc  double  salt.  It  is  extracted  with  ammonia  in  a  large 
boiling-pan,  and  from  this  solution  the  base  is  precipitated  with  ammonia.  Into  the 
enamelled  pan,  set  in  a  water  bath,  there  are  put  120  kilos,  sulphuric  acid  and  280 
litres  of  water,  and  100  kilos,  of  base  are  stirred  into  the  warm  mixture.  After  the 
base  is  entirely  dissolved  the  contents  of  the  pan  are  cooled  down  to  20°,  and  130  kilos, 
ammonia  are  let  run  in,  in  a  thin  stream  and  with  constant  stirring.  The  solution  i« 
heated  to  55°-6o°  until  there  is  a  slight  separation  of  green,  which  may  be  easily  seen  if 
a,  drop  is  placed  upon  a  piece  of  white  filter-paper.  As  soon  as  a  separation  appears 
it  is  allowed  to  settle  and  filtered  through  felt  into  a  second  pan,  in  which  the  filtrate  is 


544  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

rapidly  heated  to  85°-9O°.  The  colouring  matter  separates  out  in  crystals  of  a  metallic 
lustre.  They  are  placed  on  a  filter,  drained,  and  freed  from  mother  liquor  by  vfhhzirg 
in  the  centrifugal.  The  yield  is  94  kilos. 

The  colouring  matter  consists  of  the  tetraethyldiparaamidotriphenylcarbinol  sul- 
phate (rarely  the  oxalate) : 

(C6H5 

C  C6H4.N(C2H6)2 

(C6H4.N(C2H5).S04H 

The  hydrochlorate  of  tetramethyldiamidodichlorotriphenylcarbinol  is  sold  as 
Victoria  green  3B : 

(C6H3C12 
0  C6H4.N(CH,)f 

IC6H4.N(CH3)2C1 

All  these  colouring  matters  dye  silk,- wool,  and  cottons,  mordanted  with  tannin  and 
tartar-emetic,  a  green.  But  brilliant  green  has  a  yellower  and  Victoria  green  a  more 
blue  tone  than  malachite  green.  In  wool-dyeing  acid  green  is  chiefly  used. 

Acid  green  and  light  green  SF  is  the  sodium  salt  of  diethyldibenzyldiamidotriphenyl 
carbinoltrisulpho  acid  : 

(C6H4.S03Na 

HO.C  J  C6H4.KC2H5.CH2.C6H4.S03Na 
(C6H4.N.C2H5.CH,C6H4.S03Na 

According  to  Miihlhauser  the  formation  of  the  leuko-base  of  acid  green  is  effected  by 
the  condensation  of  i  mol.  benzaldehyde  and  2  mols.  ethylbenzylaniline  by  anhydrous 
oxalic  acid  according  to  the  equation  : 

H.      (H.C6H,KC2H,CH2.C6H5    _  ^  +      fo^^^OH..^ 

[H.C6H4.N.C2H5.CH2.C0H.  1  C^6H4.N.C,H5.CH,.C6H6 

By  sulphurising  the  leuko-base  thus  formed  with  fuming  sulphuric  acid  there 
is  obtained  a  mixture  of  the  di-  and  tri-sulpho  acids  of  diethyldibenzyltriphenyl- 
methan  : 

C37H38N2  +  2S04Ha  =  C37H36(S03H)2N2  +  2H2O 
C37H38Na  +  3S04H2  =  C37H35(S03H)3N2  +  3H20. 

The  oxidation  of  the  acid  effected  with  lead  peroxide  leads  to  a  green  colouring 
matter  according  to  the  equation  : 

C37H36(S03H),N2  +  PbO,  =  C37H34(S03)2PbN2  +  H20, 
which  is  converted  into  a  sodium  salt. 

For  producing  the  leuko-base  there  are  introduced  21  kilos,  benzaldehyde  and  80 
kilos,  benzylethylaniline  into  an  enamelled  double  pan  fitted  with  an  agitator  and 
connected  with  the  steam  and  water-pipes.  To  the  mixture,  which  is  kept  in  motion, 
there  are  added  34  kilos,  of  well-dried  and  finely  sifted  oxalic  acid.  This  addition  is 
made  in  successive  portions  within  an  hour.  When  the  mixture  is  complete  the  pan 
is  closed,  the  water  in  the  jacket  is  brought  to  60°,  a  temperature  which  is  maintained 
for  one  day.  The  two  following  days  the  heat  is  kept  at  80°,  and  on  the  fourth  day  it 
is  maintained  at  100°.  By  keeping  the  given  temperature  for  these  times,  and 
agitating  continually,  the  reaction  is  kept  up  very  regularly.  At  the  end  of  the 
fourth  day  the  leuko-base  is  obtained  as  a  soft  green  paste,  still  containing  benzoic  acid 
and  benzaldehyde.  The  cover  of  the  manhole  is  removed  and  the  hot  paste  is  neu- 
tralised by  agitation  with  soda-lye.  About  100  kilos,  of  lye  at  62°  Tw.  are  needed. 

The  man-hole  is  closed,  the  pressure-pipe  fixed  in  its  place,  and  the  contents  of  the 
pan  are  entirely  forced  over  into  the  still,  where  the  excess  of  benzaldehyde  is  com- 
pletely removed  from  the  leuko-base  by  distillation  in  a  current  of  steam.  When  this 


SECT,  iv.]  BENZOL   COLOURS.  545 

has  been  effected  the  still  is  closed  and  the  contents  are  heated  to  a  boil  with  indirect 
steam.  Direct  steam  is  then  turned  into  the  boiling  mass,  which  carries  with  it  the 
benzaldehyde  which  has  escaped  the  reaction.  The  distillation  is  kept  up  until  only 
clean  water  passes  over,  thus  showing  that  the  benzaldehyde  has  been  completely 
separated  from  the  base.  The  wide  cock  at  the  bottom  of  the  pan  allows  it  to  be 
emptied  into  a  double  pan  placed  below.  When  cold  the  faintly  alkaline  lye  is 
drawn  off  with  a  syphon  from  the  solidified  leuko-base,  which  is  then  again  washed 
with  water.  The  liquor  and  the  washings  are  worked  up  as  sodium  oxalate. 

The  base  remaining  in  the  copper  pan  is  melted  and  heated  for  about  a  day,  stirring 
until  it  is  completely  dry.  When  cold  the  base  is  broken  out  of  the  double  pan, 
and  divided  as  finely  as  possible  by  beating  with  a  wooden  mallet.  The  yield  is  93  kilos. 
The  condition  for  producing  a  good  base  is  pure  material — pure  benzaldehyde,  pure  benzol- 
ethyl  aniline,  and  perfectly  dry  oxalic  acid. 

For  sulphurising,  200  kilos,  of  a  20  per  cent,  fuming  sulphuric  acid  are  placed  in  a 
pan,  fitted  up  in  the  same  manner  as  for  obtaining  the  leuko-base.  There  are  then 
added,  with  constant  stirring,  50  kilos,  of  the  pulverised  leuko-base,  not  letting  the 
temperature  rise  above  45°,  which  is  effected  by  a  rapid  current  of  water  through  the 
jacket.  The  base  soon  dissolves  in  the  acid,  with  an  escape  of  sulphurous  and  carbonic 
acids.  After  the  introduction  of  the  leuko-base  the  pan  is  heated  to  8o°-85°,  neither 
higher  nor  lower. 

Specimens  taken  out  of  the  pan,  which  may  be  drawn  after  two  hours  of  action,  are 
covered  with  distilled  water  in  a  test-tube,  and  mixed  with  ammonia  in  excess,  and  show 
the  progress  and  the  end  of  the  sulphurising.  As  soon  as  such  a  specimen,  after  the 
addition  of  the  ammonia,  no  longer  appears  turbid,  it  is  tested  in  the  dye-house  against 
the  standard  sample,  and  the  process  is  stopped  or  continued  according  as  the  right  tone 
has  been  reached  or  not. 

The  perfectly  sulphurised  mass  is  let  cool,  and  the  next  day  it  is  forced  over  into  a 
vat  with  1000  litres  water.  To  separate  the  sulphuric  acid  it  is  mixed  with  milk  of 
lime — prepared  from  150  kilos,  of  lime — until  the  reaction  is  slightly  alkaline.  The  mass 
is  heated  with  direct  steam  to  the  boiling-point.  To  separate  out  the  gypsum  in  a 
crystalline  state,  about  500  litres  of  cold  water  are  added  with  agitation,  bringing  the 
temperature  to  6o°-65&.  The  whole  contents  are  let  off  into  the  montejus  and  filtered 
through  a  filter-press.  The  filtrate  is  run  into  a  large  iron  tank  containing  a  copper 
steam-worm.  The  cakes  remaining  in  the  press  are  thrown  each  time  into  the  lime-cask, 
and  after  all  the  residues  have  been  united  they  are  boiled  up  with  1000  litres  of  water, 
and  further  treated  as  above.  The  final  residue  is  thrown  away ;  the  filtrates,  united, 
are  evaporated  down  to  1200  litres,  and  filtered  through  an  open  filter  into  the  oxidation- 
vat  set  below,  where  the  liquid  is  cooled  to  i9°-2o°. 

For  obtaining  the  lead  peroxide  needful  for  oxidation  22  kilos,  of  litharge  are  dis- 
solved in  40  kilos,  of  acetic  acid  at  40  per  cent,  and  i  oo  litres  of  water  in  a  wooden  vat, 
with  agitation,  and  the  introduction  of  steam.  The  lead  acetate  thus  obtained  is  mixed 
with  a  finely  strained  paste  of  chloride  of  lime  (obtained  from  27  kilos,  chloride  of  lime 
and  54  litres  water)  until  all  the  lead  acetate  has  been  converted  into  peroxide.  The 
end  of  the  reaction  is  known  as  follows  : — A  drop  of  the  lead  solution  placed  with  a  glass 
rod  upon  a  slip  of  filter-paper  gives  a  brown  spot  of  peroxide  with  a  moist  colourless  spot 
around  it.  If  this  colourless  zone  is  turned  yellow  on  applying  to  it  a  drop  of  a  clear 
solution  of  chloride  of  lime,  more  chloride  of  lime  must  be  added. 

The  lead  peroxide  is  allowed  to  settle,  and  the  weak  acetic  solution  is  poured  through 
a  filter.  After  twice  boiling  up  in  water  and  letting  settle,  the  dark-brown  mud  is  placed 
on  a  filter ;  the  paste,  when  well  washed,  is  put  in  a  small  tared  tub,  and  the  whole  is 
made  up  with  water  to  a  net  weight  of  56  kilos. 

For  producing  acid  green  the  oxidation  is  conducted  below  20°,  the  agitator  is  set  in 

2    M 


546  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

rapid  action,  and  the  mass  is  acidified  with  10  kilos,  sulphuric  acid  at  158°  Tw.  The 
lead  peroxide  is  added  to  the  liquid,  which  is  in  rapid  motion.  The  colourless  solution 
becomes  a  deep  green,  acid  green  being  formed. 

After  stirring  for  ten  minutes,  all  the  lead  and  lime  are  removed  from  the  solution 
by  scattering  in  about  25  kilos,  of  soda.  The  addition  of  soda  must  cease  as  soon  as  a 
specimen,  after  nitration  and  dilution  with  water,  no  longer  gives  a  precipitate  on  the 
further  addition  of  soda.  It  is  then  heated  to  70°,  the  mass  is  run  off  into  the 
montejus  and  forced  through  a  filter-press  with  double  filter-cloths.  The  filtrate  is 
passed  into  an  iron  cistern  fitted  with  a  steam -worm.  The  green  solution  .is  concentrated 
to  about  600  litres  and  run  into  the  copper  stirring-pans  placed  below,  fitted  with 
mechanical  scrapers.  Here  it  is  evaporated  down  to  dryness,  and  the  residue  is  exposed 
for  two  to  three  days  on  zinc  plates  in  the  drying-room. 

The  dried  green  is  ground  in  a  ball-mill  (such  as  used  for  grinding  indigo),  and  is 
sent  out  as  a  dark  green  powder.  It  is  also  sold  in  a  liquid  state — liquid  acid  green — 
in  10  or  20  per  cent,  solutions.  The  yield  is  85^5  kilos. 

Resorcine,  C6H4(OH)j,  is  obtained  by  melting  sodium  benzoldisulphate  with  sodium 
hydrate. 

Into  a  double  pan  fitted  with  an  agitator  are  put  300  kilos,  sulphuric  acid  at  158° 
Tw.  and  60  kilos,  of  benzol  free  from  thiophene.  The  pan  is  then  connected  with  a  reflux- 
condenser.  The  reaction  is  set  up  by  constant  stirring,  supported  by  the  introduction 
of  steam  into  the  jacket,  so  that  the  tube  connecting  the  pan  and  the  condenser  is  but 
slightly  warm  to  the  hand.  The  vapours  of  benzol  are  liquified  and  flow  back.  After 
continuous  mixing  for  about  ten  hours  at  a  moderate  heat  the  reaction  is  completed  with 
the  formation  of  benzolmonosulpho  acid,  C6H5.SOj.OH.  This  acid,  dissolved  in  an 
excess  of  sulphuric  acid,  is  put  the  next  day  into  a  pan  fixed  in  an  oil-bath  (provided 
with  an  agitator  and  connected  with  a  leaden  ascending  condenser),  in  order  to  be 
converted  into  the  disulpho  acid.  For  this  purpose  the  mass  is  mixed  with  85  kilos,  of 
salt-cake,  ground  and  well  dried ;  the  agitator  is  set  in  motion,  and  the  oil-bath  is  heated 
to  240°.  After  heating  for  four  hours,  the  contents  of  the  pan  take  a  temperature  of 
225°.  This  heat  is  kept  up  for  about  eight  hours,  whilst  the  agitator  is  in  constant 
action.  During  the  first  half  of  the  time  benzol  distils  over  and  is  collected  in  a  re- 
ceiver, whilst  sulphurous  acid  escapes. 

The  next  day  the  contents  of  the  pan,  which  are  still  moderately  warm,  are  mixed 
with  1500  litres  of  water  in  a  wooden  vat  holding  3000  litres,  and  limed  out  with  milk 
of  lime  made  from  200  kilos,  of  lime,  and  passed  through  a  sieve.  The  boiling  faintly 
alkaline  mass  is  chilled  with  800  litres  of  cold  water  to  form  gypsum.  The  contents  of 
the  vat  are  run  off  into  a  montejus  and  forced  through  the  filter-press.  The  filtrate  is  led 
into  a  large  evaporating  trough.  The  press-cakes  are  again  boiled  up  with  about  1500 
litres  of  water,  and  separated  from  gypsum  after  the  vat  has  been  filled  with  water.  The 
combined  filtrates  are  concentrated  to  2000  litres,  and  the  solution  is  then  run  off  into 
the  conversion  tanks.  An  addition  of  6  to  10  kilos,  of  soda  is  sufficient  to  precipitate 
all  the  lime.  The  liquor  let  off  into  a  montejus  is  separated  from  calcium  carbonate 
by  means  of  the  filter-press.  The  filtrate  is  evaporated  in  two  stirring-pans  until  the 
scrapers  stop  from  the  toughness  of  the  mass.  The  moist  salt  is  put  in  flat  double 
pans  and  dried,  constantly  stirring  with  an  iron  rod,  to  a  powder,  which  is  then  ground 
and  sifted.  The  yield  is  200  kilos,  sodium  benzoldisulphate,  C6H4  (S03.Na)2.  The 
following  conspectus  shows  the  limit  values  for  so-called  "  return  oil,"  and  yield  in 
two  lots : — 

Sulphuric  acid:  Benzol.  Salt-cake.  Lime.  Soda,  Return  Oil  Yield, 

300          ...          60          ...          85          ....          200          ...          6'5          ...  14          ...  ISO 

300  ...  60  ...  85  ...  210  ...  9'0  ...  8  ...  200 

There  are  put  250  kilos,  solid  caustic  soda  into  an  open  melting-pan  over  an  open 


•SECT,  iv.]  BENZOL  COLOUES.  547 

fire,  provided  with  an  agitator,  and  to  effect  a  more  rapid  solution  there  are  added  10 
kilos,  of  water.  The  formation  of  a  scum  on  the  top  shows  that  the  caustic  is  not  hot 
•enough  to  take  up  the  salts  to  be  added  without  solidifying.  It  is  therefore  heated 
until  both  the  scum  and  the  crusts  adhering  to  the  sides  are  perfectly  liquified.  If  a 
piece  of  the  salt  thrown  in  melts  quickly  with  a  hissing  sound  the  temperature  is  high 
•enough.  The  agitator  is  set  in  motion,  and  in  a  short  time  125  kilos,  of  the  dry  salt 
are  thrown  in,  but  so  that  the  contents  do  not  boil  over,  which  is  regulated  by  stopping 
or  turning  the  agitator.  The  introduction  of  the  salt  takes  thirty  minutes.  The 
.mass  begins  to  froth  as  water  escapes ;  gradually  it  becomes  more  quiet,  turns  oily,  and 
retains  a  white  foam.  In  time  it  becomes  yellow,  and  then  brown,  and  spirts  violently. 
When  the  brown  mass  no  longer  works  it  is  ready,  and  the  hot  mass  is  baled  out  with 
iron  ladles  upon  iron  sheets,  where  it  cools.  The  process  may  be  explained  by  the 
following  equation — 

C6H4(S03Na)2  +  4NaOH  =  CGH4(ONa)2  +  2Na2S03  +  2H2O 

The  melt,  broken  up,  is  thrown  into  a  large  stone  trough  containing  500  litres  of 
•water.  9  to  10  carboys  of  strong  hydrochloric  acid  expel  all  the  sulphurous  acid,  and 
produce  a  moderately  acid  solution  of  resorcine.  So  much  acid  is  added  as  to  turn  a 
,piece  of  blue  litmus  paper  slightly  red. 

The  liquid,  run  off  into  an  iron  receiver  lined  with  lead,  is  pressed  over  by  opening  an 
air-cock  into  a  horizontal  mixing-pan  provided  with  an  agitator.  In  this  apparatus 
the  solution  containing  resorcine  is  extracted  four  times,  each  time  with  100  litres  of 
purified  amylic  alcohol.  The  solution  and  the  amylic  alcohol  are  mixed  for  half-an- 
•hour,  and  the  liquid  is  then  syphoned  into  the  elevated  pointed  cylinder.  After 
«ettling  for  an  hour  the  salt  solution  is  run  back  into  the  mixer,  and  the  deep  brown 
alcohol  charged  with  resorcine  is  let  into  the  amyl-cistern.  After  this  extraction  has 
<been  repeated  four  times  the  salt  solution  is  exhausted,  and  the  fourth  extract  is 
scarcely  coloured.  The  combined  extracts,  after  standing  for  twelve  hours  and 
separation  from  the  adhering  saline  solution,  are  run  off  into  the  still. 

The  amylic  solution  of  resorcine  is  heated  by  indirect  steam  to  about  100°.  As 
soon  as  this  temperature  is  reached  direct  steam  is  allowed  to  enter,  which  carries 
away  the  amylic  alcohol,  and  leaves  the  resorcine  behind  in  the  pan.  When  only  water 
issues  from  the  condenser  the  distillation  is  stopped,  and  the  solution  of  resorcine  is 
run  out  into  an  enamelled  iron  pan.  The  water  is  evaporated  off,  which  takes  twelve 
Ihours.  The  resorcine  has  now  to  be  purified. 

The  purification  is  effected  by  distillation  in  a  vacuum.  For  this  purpose  the  liquid 
•contents  of  the  double  pan  (about  30  kilos.)  are  baled  into  a  copper  pan  provided  with 
a  thermometer,  and  closed.  A  copper  Liebig's  condenser  connected  with  the  cover 
conveys  the  distillate  into  a  copper  receiver  with  an  exit  cock,  which  is  again  connected 
with  the  suction  pump.  At  first  some  water  and  phenol  pass  over  from  the  heated 
mass,  and  escape  on  opening  the  cock  of  the  receiver.  At  about  190°  the  cock  is 
closed,  and  the  pressure  of  the  air  is  reduced  to  630  millimetres.  On  raising  the  heat 
the  resorcine  begins  to  boil  and  passes  over  into  the  receiver.  Here  caution  is  needed 
on  account  of  a  possible  stoppage  of  the  cooler,  which,  however,  may  be  overcome  by 
letting  only  a  moderate  stream  of  water  into  the  cooling  tube,  or  interrupting  it  for  a 
time  entirely.  The  liquid  resorcine  collecting  in  the  receiver  is  run  in  known 
quantities  into  moulds  of  tinned  copper,  and  thus  the  commercial  product  is  obtained 
of  20  to  23  kilos,  of  pure  resorcine  from  125  kilos,  of  benzol  disulphate. 

Fluoresceine  Colouring  Matters. — The  halogenous  and  nitro-halogenous  derivations 
of  fluoresceine  are  colouring  matters  highly  valued  as  eosines  ('Ear,  morning  redness), 
.surpassing  all  other  colours  in  lustre  and  fire.  The  most  important  are : 

i.  Tet/rabrom  fliwresceine,  the  sodium  and  ammonium  salts  of  which  are  met  with  in 
trade  as  eosine,  eosine  B,  soluble  cosine,  &c.,  in  the  form  of  red  and  reddish-brown 


548  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

powders.  It  is  obtained  by  bromising  fluoresceirie  in  alcohol  or  in  water.  The  garnet- 
red  crystals  of  tetrabrom  fluoresceine  sodium  (Eosine  A  extra)  are  used  in  silk-dyeing, 
whilst  the  first-named  eosine  brands  serve  especially  also  in  colouring  paper  and  in  the 
manufacture  of  lakes. 

2.  Dibromfluoresceine  occurs  in  trade  as  a  sodium  salt,  more  or  less  mixed  with 
tetrabrom  fluoresceine  under  the  name  of  Eosine  orange. 

3.  Ethyltetrabromfluoresceine  is  obtained  as  a  potassium  salt  in  red  crystals  with  a 
green  surface  lustre.     It  is  known  by  the  trade  names  primrose,  spirit  eosine,  ethyl- 
eosine,  eosine  S.,  rose  J.  B.  a  1'alcool,  &c.     It  is  obtained  by  bromising  fluoresceine  in 
hot  alcohol,  when  alkylising  and  bromising  are  effected  simultaneously.     It  is  used  to 
some  extent  in  silk-dyeing. 

4.  Dibromdinitrofluoresceine  is   prepared  ou  the  large  scale  by  bromising  dinitro- 
fluoresceine  in  an  alcoholic  solution,  or  by  nitrising  tetrabrom  fluoresceine  in  glacial 
acetic  acid,  or  by  nitrising  bibromeosine  in  a  water  solution.     It  is  sold  under  the 
names:    eosine  scarlet,  eosine  B.N.,  safrosine,  lutecienne,  daphnine,  rose  des  Alpes, 
in  the  state  of  alkaline  salts.     The  sodium  and  potassium  salts  appear  black,  and  the 
Ammonium  salt  red.     These  salts  meet  with  but  slight  application  in  dyeing,  but  the 
ammonium  salt  and  the  neutral  sodium  salt,  which  when  evaporated  down  in  thin 
layers  has  a  greenish  colour,  are  exported  to  China  to  a  considerable  extent. 

5.  Tetraiodofluoresceine  is  obtained  by  iodising  fluoresceine  in  an  aqueous  solution. 
Its  alkaline  salts   are  of   a   brown  red,  but  the   ammonium   salt  is  of  a  light  brick 
red.      These  salts  are  used  in  silk  and  cotton  dyeing  and  paper-staining,  under  the 
names  erythrosine,  eosine  J,  pyrosirie  B,  iodeosine  B,  dianthine  B,  rose  B  a  I'eau, 
soluble  primrose,  eosine  bleudtre. 

6.  Di-iodo fluoresceine,  is  also  found  mixed  with  tetraiodofluoresceine  in  the  state  of 
an  alkaline  salt,  as  erythrosine  G,  dianthine  G,  iodeosine  G,  &c. 

(C6H3.OH  (C6HBr2.ONa  (C6HBr2.OC,H5 

c     o  I    o  Jo 

U  j  C6H3.OH  '   C6HBrrONa  J  |  CfiHBr,.OK 

lan.co.o  la,H,.co.o 


lC6H4.CO.O 

Fluoresceine.  Eosine.  Primrose. 


(C6HBr(N02).OK  fC6HL.ONa 

iJ     °  oJ     ° 

]C6HBr(N02).OK  U)C6HL.ONa 

lC^.CO.0  Ic.H.CO.O 


C6H2I.OK 

0 

C6HSI.OK 
IC6H4.CO.O 


Eosine  scarlet.  Erythrosine.  Erythrosine  G. 

Fluoresceine  is  obtained,  according  to  Miihlhauser,  by  melting  2  5  kilos,  of  resorcine 
in  a  pan  placed  in  an  oil  bath  at  160°,  and  stirring  in  17^  kilos,  of  phthalic  anhy- 
dride. The  reaction  begins  as  soon  as  the  liquid  has  been  heated  for  about  ninety 
minutes  to  180°.  During  the  reaction,  which  lasts  forty  minutes,  the  mass  must  not  be 
stirred,  as  it  would  otherwise  flow  over.  The  mass  thickens  to  a  paste,  and  it  is  then 
stirred  from  time  to  time  by  means  of  an  iron  rod  until  it  is  perfectly  dry,  which  is 
effected  in  twenty-four  to  thirty  hours'  heating  to  200°  to  205°.  The  end  of  the  reaction 
is  observed  by  the  brittleness  of  a  small  lump  of  fluoresceine  when  struck  with  the 
hammer. 

The  main  points  to  be  observed  in  melting  are  purs  materials  and  the  maintenance- 
of  a  temperature  of  180°  during  the  reaction.  If  the  mass  rises  during  the  reaction, 
and  there  is  danger  of  an  overflow,  the  temperature  is  reduced  by  blowing  in  air  with 
bellows.  The  yield  of  crude  fluoresceine  is  37^  kilos. 

The  crude  fluoresceine  is  dissolved  by  boiling  with  500  litres  of  water  and  50  kilos, 
of  soda-lye  at  62°  Tw.,  and  the  liquid  is  made  up  to  1000  litres.  After  filtration 
into  a  vat  fixed  below,  the  reddish-yellow  filtrate  is  precipitated  with  90  kilos,  of 


SECT,  iv.]  BENZOL   COLOURS.  549 

hydrochloric  acid.  The  fluoresceine  goes  down,  and  the  fluorescent  colour  liquor  is 
poured  off.  By  again  boiling  up  the  sediment  in  500  litres  of  water  we  obtain  a  red- 
dish yellow  turbid  liquid,  from  which  the  fluoresceine  is  generally  completely  pre- 
cipitated by  the  addition  of  a  little  hydrochloric  acid.  It  is  allowed  to  settle,  the  solution 
is  decanted  off,  all  the  fluoresceine  is  collected  upon  a  filter,  drained,  and  dried. 

The  drying  is  effected  in  shallow  enamelled  capsules,  the  flat  bottom  of  which  is 
about  80  square  centimetres ;  four  such  capsules  are  placed  on  a  water- bath,  and  are 
then  exposed  to  a  temperature  not  exceeding  98°.  At  this  temperature  the  moist 
fluoresceine,  which  has  been  spread  in  a  layer  of  about  5  millimetres  in  thickness, 
quickly  dries  to  a  fine  powder,  which  is  then  sifted.  The  yield  is  36  kilos. ; 

Resorcine.  Phthalic  Acid.  ZnCla.  Crude  Melt.  Lye,  6a°  Tw.        Hydrochloric  Acid. 

25  ...  17  ...  8  ...  45  ...  60  ...  loo 

For  obtaining  tetrabrom  fluoresceine  in  an  aqueous  solution,  60  kilos,  of  soda-lye  at 
62°  Tw.  are  mixed  in  a  jacketed  cast-iron  pan  with  150  litres  of  water.  Then,  whilst 
the  lye  is  being  stirred,  32  kilos,  of  bromine  are  run  in  direct  from  the  bottles  by  means 
of  a  syphon. 

Then  is  formed  a  mixture  of  NaBr,  NaBr08,  and  NaBrO ;  the  last  compound  is 
converted  into  NaBr  by  boiling  for  half  an  hour.  The  decomposition  of  the  sodium 
hypobromite  is  necessary,  as  otherwise  a  yellow  product  would  be  formed  on  decom- 
posing with  hydrochloric  acid. 

Meanwhile,  in  an  adjacent  steam-pan,  10  kilos,  of  fluoresceine  have  been  dissolved 
in  25  kilos,  lye  at  62°  Tw.  and  150  litres  of  water  by  boiling  for  thirty  minutes.  Both 
solutions  are  run  off  into  a  vat  as  soon  as  cold,  well  stirred  up,  and  precipitated  by 
the  immediate  addition  of  140  kilos,  crude  hydrochloric  acid,  with  thorough  agitation. 
Yellow  bromeosine  separates  out.  It  is  heated  to  boiling  by  direct  steam,  and  as  soon 
as  it  boils  the  vat  is  filled  up  with  water,  allowed  to  settle,  the  sediment  boiled  up 
twice  in  the  same  manner  with  fresh  water,  and  lastly  filtered.  The  eosic  acid,  thus 
entirely  freed  from  mineral  acids,  is  dried  upon  plates,  as  described  under  fluoresceine  • 
The  yield  of  tetrabromfluoresceine  is  30  kilos.  : 

Fluoresceine.  Soda-lye,  62°  Tw.  Bromine.  Soda-lye  at  62°  Tw.        Hydrochloric  Acid. 

16  ...  25  ...  32  ...  60  ...  140 

Two  such  lots — i.e.,  60  kilos. —  of  eosic  acid  are  made  soluble  by  means  of  alcoholic  soda 
in  order  to  obtain  eosine  B,  and  allowed  to  crystallise  from  the  solution. 

In  order  to  render  the  eosic  acid  soluble,  we  must  first  ascertain  by  a  trial  what 
quantity  of  soda  is  necessary  for  the  formation  of  the  neutral  eosine  salt.  For  this 
purpose  we  take  an  average  sample  of  50  grammes  eosic  acid,  mix  it  in  a  litre  flask 
with  175  grammes  of  alcohol  at  96°,  and  heat  to  boiling.  In  the  meantime  a  portion  of 
the  soda-lye,  to  be  used  on  the  large  scale  (i  part  sodium  hydroxide  and  2  parts  water 
=  72°  Tw.),  and  about  40  grammes,  are  placed  in  a  dropping-bottle. 

This  bottle  with  the  soda  weighs  (say)  134*7  grammes.  Soda  is  then  let  flow  in, 
drop  by  drop,  to  the  boiling  alcoholic  solution  of  eosine.  As  the  soda  is  added  there 
is  formed  the  red  acid  salt  of  eosine,  which  subsides.  This  sparingly  soluble  salt  serves 
as  an  indicator,  for  we  continue  dropping  in  the  soda,  keeping  up  a  moderate  heat 
and  shaking  the  flask,  until  the  acid  salt  dissolves,  passing  into  the  neutral  salt.  The 
addition  of  lye  must  cease  as  soon  as  the  last  granule  of  eosine  sodium  has  disappeared. 
The  liquid  appears  now  of  a  yellowish-red,  but  if  an  excess  of  soda  has  been  used  it 
looks  blackish-red.  Whether  the  right  quantity  of  soda  has  been  used  may  be  known 
not  merely  from  the  disappearance  of  the  acid  salt,  but  by  dipping  a  glass  rod  into  the 
solution  and  letting  it  dry  in  the  air.  If  it  is  then  dipped  into  distilled  water,  the 
adhering  eosine  will  dissolve  clear  if  sufficient  soda  has  been  added,  but  if  the  quantity 
has  been  deficient  there  is  formed  a  cloud  round  the  end  of  the  rod. 

A  correctly  neutralised  sample  when  dropped  into  a  glass  of  water  gives  a  yellowish- 


550  CHEMICAL  TECHNOLOGY.  [SECT,  iv, 

green  dichroism ;  a  solution  supersaturated  with  alkali  gives  a  dirty  green  colour  with 
a  brownish-green  dichroism.  If  the  eosine  solution  is  poured  into  a  capsule  the  margin 
should  look  yellowish-red  and  not  brown.  In  the  latter  case  too  much  alkali  has  been 
added.  If  the  contents  of  the  capsule  are  allowed  to  crystallise  overnight,  there  must 
be  no  acid  salt  at  the  bottom  of  the  cake.  On  weighing  the  dropping-flask  it  cauie 
to  1 14*46  grammes,  consequently  20*24  grammes  soda  had  been  used  to  saturate  50 
grammes  eosic  acid.  This  number  is  used  in  calculating  the  quantity  of  soda  to  be  em- 
ployed on  the  large  scale. 

Sixty  kilos,  of  eosic  acid  are  placed  in  a  copper  pan  on  the  water-bath,  and  210 
kilos,  of  alcohol  are  added — i.e.,  the  quantity  which  is  necessary  to  keep  in  solution  the 
salt  formed  on  neutralising  the  eosic  acid  with  soda.  For  this  purpose  there  are 
required  3^  times  the  quantity  of  alcohol  referred  to  the  weight  of  the  free  eosic 
acid.  It  is  convenient  to  put  the  alcohol  first  in  the  copper  pan,  and  then  to  stir  in 
the  eosine,  which  is  otherwise  apt  to  adhere  to  the  bottom  and  is  difficult  to  remove. 
The  water-bath  is  heated  to  boiling  and  the  contents  of  the  pan  to  60°.  When  this 
temperature  has  been  reached  we  run  in  (20^4  x  60)  :  50  =  24^  kilos,  soda-lye  during 
ten  minutes,  stirring  constantly.  The  free  acid  dissolves,  after  having  formed  the 
acid  saltj  The  solution  is  run  into  three  wooden  casks,  holding  each  120  litres.  On  the 
surface  of  the  liquid  there  are  laid  thick  wooden  lids,  which  dip  i  to  2  centimetres  into 
the  alcohol,  so  as  to  give  the  greatest  possible  space  for  crystallisation  and  at  the  same 
time  to  decrease  the  proportion  of  the  crystals  forming  at  the  bottom.  The  crystals- 
deposited  on  the  cover  and  the  sides  are  always  a  finer  and  better-looking  article  than 
those  attached  to  the  bottom. 

After  standing  two  or  three  clays  in  a  cool  place  the  crystallisation  is  complete.  The 
cover  is  raised,  the  mother  liquor  run  off,  and  the  crystals  from  the  cover  and  sides  are 
put  upon  the  filter,  as  are  those  also  from  the  bottom  separately.  Cakes  of  crystals 
are  detached  from  the  wood  with  a  knife.  The  crystals,  when  they  have  been  drained, 
are  dried  on  frames  at  60°  in  the  drying-room,  which  takes  three  days.  When  dry  the 
crystals  are  ground.  The  brownish-red  powder  is  sold  as  eosine  B : 

Eosine.  Alcohol.  Soda.  Eosine  B. 

60  ...  210  ...  24-5  ...  57-5 

The  mother  liquor  obtained  on  the  crystallisation  of  eosine  B  is  distilled,  and  yields 
alcohol  at  96  per  cent.,  the  colouring  matter  remaining  in  solution  being  disregarded. 

The  bromising  of  fluoresceine  in  an  alcoholic  solution  is  effected  in  three  enamelled 
pans.  Each  pan  is  charged  with  10  kilos,  fluoresceine  and  80  kilos,  of  alcohol  at  96°. 
The  bromising  is  effected  by  letting  24  of  bromine  flow  in  a  slow  stream  and  with 
constant  stirring  from  a  bottle  fitted  with  a  cock,  the  exit  pipe  of  which  plunges  a 
little  into  the  alcohol.  This  operation  lasts  fifteen  minutes ;  when  it  is  completed  the 
mixture  is  well  stirred  and  covered  up.  It  is  set  aside  four  days,  but  is  well  stirred  up 
three  times  each  day,  thus  effecting  a  complete  separation  of  the  eosic  acid.  In  bromising 
we  remark  that  when  half  the  bromine  has  been  added,  the  liquor,  which  was  at 
first  a  reddish-brown,  has  changed  to  a  blackish -bro wn ;  there  is  first  formed  the 
dibromide  of  fluoresceine,  which  is  readily  soluble  in  alcohol.  On  the  further  addition 
of  bromine  the  tetrabromide  is  deposited  as  a  brick-red  mass.  After  standing  for  four 
days  the  alcohol  is  drawn  off  with  a  syphon,  and  the  red.  deposit  is  twice  washed  with 
alcohol.  For  this  purpose  40  kilos,  of  alcohol  are  placed  in  each  pan ;  it  is  well  stirred 
up,  let  stand  for  one  day,  and  the  washing  alcohol  is  then  drawn  off.  A  second  washing 
is  executed  in  the  same  manner.  The  red  deposit  at  the  bottom  of  the  pan  is  collected 
upon  filters  of  felt,  drained,  and  pressed.  The  comminuted  press-cakes  are  dried  upon 
cotton  cloths  spread  out  on  frames  in  the  drying-room,  which  lasts  two  days.  The  yield, 
of  eosic  acid  is  50  kilos. 


Fluoresceine. 

AlcohoL 

30 

240 

Washing  Alcohol. 

Yield  of  Eosic  Acid. 

Soda. 

240 

50 

20 

SECT,  iv.]  BENZOL   COLOURS.  551 

The  conversion  of  tetrabromfluoresceine  into  eosine  A  extra  is  effected  by  crystalli- 
sation according  to  the  method  above  mentioned.  The  crystals  are  not  broken,  but 
merely  crushed  with  a  piece  of  wood  to  fragments  of  the  size  of  a  nut,  and  they  are 
despatched  in  this  state.  The  yield  is  50  kilos. 

Bromine. 
72 

Alcohol.  Eosine  A  extra. 

175  -  So 

For  obtaining  eosine  B  with  a  red  surface,  30  kilos,  of  tetrabrom  fluoresceine, 
obtained  by  the  alcohol  process  and  finely  sifted,  are  used.  The  eosine  is  made  soluble 
in  an  upright  wooden  box,  which  can  be  tightly  closed  with  a  door.  In  this  box  are 
inserted  thirty  frames,  arranged  like  drawers,  each  3  centimetres  in  height,  and  with 
linen  bottoms  of  6  square  metres  in  surface,  at  intervals  of  3  centimetres,  so  that  one 
frame  is  exactly  upon  the  other.  The  available  linen  surface  extended  in  the  box  is 
about  1 8  square  metres.  Upon  each  frame  there  is  spread  as  uniformly  as  possible 
about  i  kilo,  of  eosic  acid,  and  after  all  the  frames  have  been  inserted  the  box  is 
closed.  The  box  is  connected  with  an  apparatus  for  generating  ammonia,  consisting 
of  a  still  and  two  gas-desiccators.  The  ammonia  is  conducted  into  the  bottom  of  the 
box,  it  traverses  the  entire  layer  of  eosine  from  below  upwards,  and  is  very  eagerly 
absorbed  by  the  free  eosic  acid,  in  accordance  with  the  equation  : 
C2oH8Br405  +  2NH3  =  C2oH6Br4Os.(NH4)2. 

In  about  two  hours  all  the  eosic  acid  is  converted  into  the  neutral  ammonium  salt. 
If  a  fragment  taken  out  of  one  of  the  frames  dissolves  in  distilled  water  without 
turbidity,  the  process  is  broken  off.  The  slight  excess  of  ammonia  escapes  into  the 
chimney  through  an  iron  tube  fixed  above  the  box : 

Eosic  acid.  Sal-ammoniac.  Lime.  Eosine  B. 

30-0  .„  15-0  ...  30  31-8 

Utilisation  of  the  Residues. — The  alcohol  which  has  been  used  for  bromising  in  ono 
process  is  poured  into  an  enamelled  pan.  It  contains  free  eosic  acid,  resin,  hydrogen 
bromide,  and  a  little  bromethyl.  In  order  to  separate  the  eosine  from  the  alcohol,  water 
is  run  into  the  liquid  in  a  thin  stream  and  with  constant  agitation,  about  equal  to  one- 
third  of  the  volume  of  the  alcoholic  solution.  If  more  water  is  added,  the  resin  is  sepa- 
rated out  along  with  the  eosine,  which  has  to  be  avoided.  The  free  eosine  subsides  to  the 
bottom.  After  completely  settling,  the  watery  alcohol  is  drawn  off.  The  deposit  put  on 
the  filter  is  twice  washed  with  water.  If  on  the  second  washing  the  eosine  remains  sus- 
pended for  a  long  time,  it  is  a  sign  that  all  the  acid  is  washed  out,  for  in  acid  water  the 
subsidence  is  more  rapid  and  without  turbidity.  If  the  residue,  thus  filtered  and  freed 
from  acid,  is  sandy,  it  is,  after  draining,  put  through  the  filter-press  and  dried  ;  if  it  is 
resinous,  it  must  be  washed  with  alcohol  to  take  up  the  resin.  The  residuary  eosine 
thus  obtained  is  collected  until  about  60  kilos,  have  accumulated.  Such  residues  are 
then,  according  to  their  purity,  washed  once  or  twice  with  alcohol.  To  each  kilo,  of 
eosine  residues,  we  add  2  kilos,  of  alcohol.  The  eosine  in  washing  must  be  ground  into 
the  alcohol,  if  this  is  neglected  and  the  whole  mass  is  added  at  once,  it  clots  together 
and  is  very  difficult  to  wash. 

The  eosine  after  being  thus  washed  is  now  fairly  pure,  and  is  filtered,  pressed,  and 
dried.  By  crystallisation  it  is  made  to  yield  a  fine,  pure  colouring  matter.  The 
necessary  quantity  of  soda  for  solution  is  determined,  and  the  product  is  crystallised 
from  alcohol  as  described  above.  Many  impurities  pass  into  the  alcohol.  The  crystals 
are  dissolved  in  water,  precipitated  with  hydrochloric  acid,  filtered,  dried  and  re- 
crystallised,  and  then  generally  yield  a  product  equal  in  its  properties  to  eosine  B. 

On  working  up  the  alcoholic  bromine  lye  we  obtain  eosine  B,  dilute  bromising 


552  CHEMICAL   TECHNOLOGY.  [SECT.  iv. 

alcohol,  washing  alcohol,  and  mother  liquors  from  the  first  and  second  crystallisation. 
All  the  alcoholic  liquids  are  collected  and  redistilled. 

The  mother  liquors  obtained  from  the  crystallisation  of  "  Eosine  A  extra "  are 
separated  from  alcohol  in  the  distillatory  apparatus,  and  the  residue  is  dried.  Here 
also  about  60  kilos,  of  residues  are  allowed  to  accumulate,  dissolved  in  water,  and  the 
eosine  is  precipitated  with  hydrochloric  acid.  The  further  treatment  of  the  dried  eosic 
acid  is  effected  by  washing  and  recrystallisation  with  alcoholic  soda  in  the  manner 
described  above. 

The  subjoined  table  (p.  553)  collates  the  conversion  of  fluoresceine  to  eosine  and 
the  treatment  of  the  alcoholic  residues. 

For  the  production  of  dibromfluoresceine  10  kilos,  of  fluoresceine  are  suspended 
in  80  kilos,  of  alcohol  at  96°,  and  treated  with  12  kilos,  of  bromine  as  above  described. 
The  fluoresceine  passes  into  solution  with  the  formation  of  dibromide.  When  cold 
the  dibromfluoresceine  is  precipitated  with  100  litres  water  and  the  diluted  alcohol  is 
drawn  off.  The  dibromfluoresceine,  separated  out  as  a  resin,  after  washing  with  water, 
is  dissolved  in  a  cask  in  200  litres  of  water  and  20  kilos,  lye  at  62°  Tw.,ancl  when  cold 
it  is  precipitated  with  40  kilos,  of  hydrochloric  acid.  It  is  obtained  as  a  pulverulent 
precipitate,  which  is  freed  from  acid,  filtered,  and  dried.  The  yield  is  15-4  kilos. 

Eosine  Orange. — A  laboratory  experiment  shows  the  quantity  of  lye  necessary  for 
dissolving.  To  the  dibromeosine  suspended  in  150  litres  of  hot  distilled  water  there  is 
added  the  quantity  of  lye  determined  by  experiment,  and  the  mixture  is  evaporated  to 
a  paste.  It  is  then  completely  dried  on  sheet  metal  in  the  drying-room.  The  yield  is 
17  kilos. 

To  obtain  ethyltetrabromfluoresceine,  80  kilos,  of  alcohol  at  96°,  and  20  kilos,  of 
fluoresceine  are  placed  in  a  jacketed  and  enamelled  autoclave,  agitating  all  the  time. 
The  autoclave,  which  is  fitted  with  an  enamelled  mechanical  agitator  and  an  ascending 
leaden  cohobater,  is  closed  and  heated.  Steam  is  let  enter  the  jacket  until  the  alcohol 
boils.  Meantime,  13  kilos,  bromine  are  weighed  into  a  glass  bottle  provided  with  acock, 
and  the  bottle  is  placed  upon  the  elevated  refrigerating  tub.  When  the  alcohol  boils 
the  cock  of  the  bottle  is  opened  and  the  bromine  is  allowed  to  flow  down  through  a  glass 
tube  dipping  but  little  into  the  apparatus,  which  is  connected  with  the  outside  air 
merely  by  the  leaden  worm.  In  this  manner  four  bottles  of  bromine  of  13  kilos,  each 
are  successively  run  in  during  50  minutes.  The  autoclave  is  then  closed  as  tightly  as 
possible  and  heated  at  the  pressure  of  i  atmosphere  ;  the  steam  is  then  shut  off,  and  the 
mass  is  left  at  this  pressure  for  three  hours,  allowing  steam  to  enter  the  jacket  from 
time  to  time.  When  completely  cold  the  autoclave  is  opened  by  raising  the  lid.  The 
alcohol  is  drawn  off,  and  the  residue  at  the  bottom  is  placed  upon  an  asbestos  filter. 

The  eosine  thus  obtained  has  in  this  state  a  black,  a  greenish-black,  or  a  brown 
colour.  By  hot  bromising  we  obtain  a  mixture  consisting  chiefly  of  ethyltetrabrom- 
fluoresceine and  a  little  tetrabromfluoresceine.  A  bye-product  is  the  bromising  alcohol 
containing  ethyl  and  vinyl  bromide  which  is  used  for  eosine  B,  and  alcohol  at  96°. 

The  eosic  acid,  after  draining  on  the  asbestos  filter,  is  pressed  and  washed  with  100 
kilos,  of  spirit  in  an  enamelled  pan,  distributed  in  the  alcohol  with  a  wooden  stirrer, 
allowed  to  subside,  filtered,  and  pressed.  The  filtration  residue  is  again  washed  with 
about  100  litres  of  water.  The  moist,  brown,  eosine  mass  is  filtered,  pressed,  and  dried 
on  frames  in  the  drying- room.  The  yield  is  27  kilos,  of,  eosic  acid. 

Spirit  Eosine. — To  isolate  eosic  acid  and  to  render  it  alcoholic  it  is  crystallised  from 
an  alcoholic  solution  of  potassa.  The  eosine  soluble  in  water  remains  dissolved  in  the 
mother  liquor,  whilst  the  spirit-eosine  crystallises  from  the  36  per  cent,  alcohol. 

In  order  to  ascertain  the  quantity  of  potassa  lye  which  will  be  necessary  for  neutralis- 
ing the  acid,  50  grammes  of  eosic  acid  are  weighed  out,  suspended  in  a  glass  flask  in  a 
mixture  of  125  grammes  water  and  75  grammes  alcohol,  and  heated  to  boiling.  To 


SECT.   IV.] 


BENZOL  COLOURS. 


553 


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554  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

the  boiling  mass  is  added  lye  from  a  weighed  dropping-bottle  until  all  red  powder  has 
disappeared,  and  merely  minute  shining  green  crystals  are  to  be  seen  at  the  bottom  of 
the  flask.  From  the  number  of  grammes  of  potassa  lye  consumed  (i  part  KHO  and  2 
parts  H,0),  the  quantity  of  lye  is  calculated  which  will  be  required  for  neutralising  the 
entire  lot. 

For  converting  the  ethyl  eosic  acid  into  the  potassium  salt,  there  are  placed  in  an 
enamelled  and  jacketed  pan  (with  a  reflux  cooler),  z\  parts  water  and  i^  part  alcohol, 
calculated  for  the  weight  of  the  eosine  to  be  operated  upon.  The  eosine  is  stirred  into 
the  cold  alcohol  36  per  cent.,  the  pan  is  closed  and  heated  to  boiling.  To  the  boiling 
mass  there  is  allowed  to  enter  in  a  thin  stream  the  calculated  quantity  of  potassa- 
lye,  previously  heated  to  80°,  with  agitation,  which  is  continued  for  fifteen  minutes 
after  the  introduction  of  the  lye.  The  cold  apparatus  is  opened  after  the  lapse  of  three 
days  ;  the  mother  liquor  is  drawn  from  the  crystals ;  the  latter  are  placed  on  a  filter  and 
freed  by  pressure  from  the  mother  liquor ;  the  cakes  are  once  more  washed  in  hot  water, 
filtered,  pressed  again,  and  dried  on  enamelled  plates.  The  yield  is  25-3  kilos,  of  spirit 
eosine. 

In  working  up  the  residues,  the  bromising  alcohol  is  run  into  an  enamelled  pan, 
mixed  with  half  its  volume  of  cold  water,  which  is  caused  to  run  in  as  a  thin  stream  and 
with  agitation.  Tetrabromfluoresceine  separates  out  as  a  red  powder.  It  is  allowed  to 
subside,  the  eosine  is  washed  out  perfectly  with  water,  filtered,  pressed,  and  dried. 
The  further  process  is  conducted  as  in  the  case  of  the  residues  of  eosine  A,  by  washing 
with  alcohol,  and  twice  recrystallising  the  sodium  salt  from  alcohol. 

The  mother  liquor  separated  from  the  crystals  is  allowed  to  stand  about  eight  days, 
when  about  2  kilos,  of  crystals  separate  out,  which  are  worked  up  with  the  following  lot. 
The  mother  liquor  (now  drawn  off  for  the  second  time)  is  separated  from  alcohol  in  the 
still.  Moderately  pure  eosic  acid  may  be  obtained  by  precipitating  the  residues  from  this 
apparatus  (previously  dissolved  in  water)  with  hydrochloric  acid.  It  is  filtered,  washed, 
and  pressed,  the  cakes  are  dried,  and  can  then  be  worked  up  like  the  eosine  A 
residues. 

The  working  up  of  the  alkaline  and  acid  alcohols  by  distillation  depends  upon  their 
reaction.  Those  of  an  acid  character  (the  bromising  and  washing  alcohols)  are  neu- 
tralised with  milk  of  lime  in  a  montejus  lined  with  lead,  and  are  then  forced  into 
the  so-called  column  apparatus  and  rectified.  The  alkaline  or  neutral  alcohols,  those 
from  the  mother  liquors  and  those  which  have  been  merely  diluted  with  water  are 
rectified  per  se,  and  worked  up  for  alcohol  at  96°  or  97°.  The  residue  in  the  still, 
obtained  by  working  up  the  acid  alcohols,  is  let  off  into  an  autoclave,  and  when  suitably 
diluted  with  water  forced  through  a  filter-press.  The  filtrate  is  worked  up  for  bromine. 
The  contents  of  the  filter-press  and  the  impure  coloured  liquors  obtained  in  working  up 
the  alkaline  alcohols  go  to  waste. 

Dinitrodibromfluoresceine. — In  bromising  dinitrofluoresceine  in  an  alcoholic  solu- 
tion (nitro-bromising  of  fluoresceine  in  alcohol)  there  are  placed  in  five  enamelled  pans 
60  kilos,  of  alcohol  at  96°  with  7  kilos,  of  fine  fluoresceine,  keeping  up  agitation.  To 
the  fluoresceine,  which  is  kept  divided  by  agitation,  we  add  gradually  7  kilos,  nitric 
acid  at  72°  Tw.,  and  immediately  afterwards  7*25  kilos,  of  bromine,  which  is  drawn 
directly  out  of  the  bottles  by  means  of  a  syphon.  Dibromdinitrofluoresceine,  which  is 
sparingly  soluble  in  alcohol,  separates  out.  The  pans  are  allowed  to  stand  undisturbed 
to  the  next  day.  The  black  liquid  is  drawn  off,  and  the  precipitate  is  washed  once  with 
30  kilos,  of  alcohol.  The  precipitates  placed  on  the  filter,  after  draining,  are  boiled  up  in 
a  tub  with  water,  allowed  to  settle,  decanted,  and  this  treatment  is  repeated  until  the 
boiling  water  begins  to  be  faintly  coloured.  When  this  is  the  case  all  the  acid  is 
washed  away.  The  fine  paste  is  spread  out  in  a  thin  layer  on  enamelled  dishes  on  the 
water-bath  and  dried.  The  yield  of  sifted  produce  is  63  kilos. : 


SECT,  iv.]  BENZOL  COLOUES.  555 

Dibromdinitro- 
Fluoresceine.  Alcohol.  Nitric  acid.  Bromine.        Washing  alcohol..        ftuoresceiue.. 

35         -        300        ...        35        -      36-25        ...        150        ...        63-0 

For  nitrising  in  glacial  acetic  acid,  30  kilos,  of  bromeosine  are  introduced  into  an 
enamelled  pan  on  the  water-bath,  which,  according  as  a  more  or  less  fine  product  is 
desired,  is  taken  either  from  a  spirit-bromised  or  a  water-bromised  sort.  To  the  brom- 
eosine are  added  25  kilos,  of  glacial  acetic  acid,  and  the  whole  is  stirred  up  to  a  uniform 
paste,  with  which  4  kilos,  of  soda- saltpetre  are  incorporated  by  diligent  stirring.  The 
pan  is  then  covered  and  the  water-bath  is  raised  to  a  boil.  The  reaction  begins  about 
7o°-8o°,  whilst  small  quantities  of  nitrous  acid  and  a  little  glacial  acetic  acid  escape.  A 
uniform  temperature  is  kept  up  by  frequent  stirring.  After  heating  for  six  to  eight 
hours,  the  red  mass  has  turned  to  a  flesh  colour,  and  the  reaction  is  at  an  end.  The 
course  of  the  reaction  is  followed  by  sampling,  and  it  is  brought  to  an  end  when  a  sample 
dissolved  in  ammonia  and  compared  with  a  type-sample  produces  at  once  a  blue  colour 
upon  a  slip  of  filter-paper. 

The  mass,  after  cooling,  is  boiled  up  in  a  wooden  vat  with  500  litres  of  water. 
After  boiling  for  about  ten  minutes  it  is  allowed  to  settle  and  the  liquor  is  pressed  off. 
The  residue  at  the  bottom  is  deacidified  in  the  usual  manner.  The  fine  flesh-coloured 
paste  is  spread  in  thin  layers  upon  enamelled  capsules  and  dried.  Yield,  29^  kilos. 

For  nitrising  in  wateiy  solution,  10  kilos,  of  fluoresceine  are  dissolved  in  a  double 
pan  in  200  litres  of  water  and  13  kilos,  of  lye  at  62°  Tw.  In  an  adjoining  double  pan 
there  are  dissolved  12  kilos,  of  bromine  in  a  mixture  of  20  kilos,  of  lye  at  62°  Tw.  and 
50  kilos,  of  water.  This  liquor  is  used  for  decomposing  sodium  hypobromite.  When 
completely  cold,  the  fluoresceine  solution  and  the  bromine  solution  are  run  into  an 
enamelled  pan  set  in  a  water-bath,  and  are  further  mixed,  with  constant  stirring,  with 
60  kilos,  sulphuric  acid  at  72°  Tw.  Yellow  bromeosine  separates  out.  30  kilos,  of 
nitric  acid  at  72  Tw.  are  run  in,  stirring  constantly.  The  admixture  of  the  acids 
must  be  effected  with  refrigeration  ;  but  as  soon  as  all  the  ingredients  are  together  the 
water-bath  is  heated  to  boiling.  The  heating  lasts  five  to  six  hours,  with  occasional 
stirring.  The  reddish-yellow  eosine  is  then  converted  into  the  flesh-coloured  nitrobrom- 
eosine.  The  product,  mixed  with  water  in  a  cask  and  freed  from  acid  by  repeated 
decantations,  is  finally  filtered  and  dried  on  the  water-bath  in  thin  layers.  The  yield 
is  19^  kilos.: — Fluoresceine,  10  ;  soda.  13;  bromine,  12;  soda  at  62°  Tw.,  20;  sul- 
phuric acid  at  72°  Tw.,  60  ;  nitric  acid  at  72°  Tw.,  30. 

The  dibromdinitrofluoresceine  is  rendered  soluble  either  by  passing  over  it  gaseous 
ammonia  when  dried  and  finely  sifted,  or  as  above  described,  or  by  adding  a  solution 
of  potash  to  the  eosine  paste  stirred  up  in  hot  water.  The  first  method  yields  the 
ammonium  salt,  the  second  that  of  sodium,  and  the  third  that  of  potassium. 

The  ammonium  salt  of  nitrobromfluoresceine  is  produced  in  the  same  manner  as 
the  ammonium  salt  of  tetrabromfluoresceine,  namely,  by  conducting  dry  ammonia 
over  the  free  acid  in  an  ammonia-chest.  There  are  used  30  kilos,  eosic  acid  obtained 
by  either  of  the  two  first  methods  above  described.  The  yield  is  31*9  kilos.  As  very 
pure  products  are  obtained  by  bromising  in  alcohol  or  glacial  acetic  acid  it  is  recom- 
mended to  employ  here  the  ammonia  method. 

For  obtaining  the  sodium  salt,  30  kilos,  of  eosic  acid  are  diffused  in  200  litres  oi 
water  in  an  enamelled  double  pan,  and  heated  to  90°.  To  this  liquid,  which  is  kept 
uniform  by  agitation,  there  is  added  soda-lye,  which  is  run  in  from  a  vessel  with  a  cock 
The  addition  of  soda  is  stopped  before  complete  neutralisation.  This  incomplete 
saturation  is  in  order  to  separate  the  pure  eosine  from  the  impure  colouring  matters 
formed  during  nitrising,  which  would  ultimately  dissolve  in  the  soda  with  the  formation 
of  salts,  but  which  remain  undissolved  as  long  as  the  soda  added  is  insufficient.  The 
progress  of  the  solution  of  the  free  acids  is  observed  by  means  of  a  slip  of  filter-paper, 


S56  CHEMICAL   TECHNOLOGY.  [SECT.  iv. 

and  soda-lye  is  added,  until  a  drop  of  the  solution  taken  out  with  a  glass  rod  and  let 
fall  upon  a  slip  of  filter-paper  held  aslant  does  not  give  a  pure,  uniform  spot,  but 
shows  a  small  quantity  of  a  solid  powdery  residue  at  the  point  of  contact.  On  the 
quantity  of  this  residue  depends  the  purity  of  the  product.  The  saturation  may, 
however,  be  carried  rather  far.  The  deep-red  liquid,  containing  little  sediment,  is 
allowed  to  settle  in  a  tall  cask,  drawn  off  after  standing  for  two  days,  and  evaporated 
clown  in  a  drying-pan.  The  yield  is  29!  kilos,  of  scarlet. 

The  potassium  salt  is  obtained  with  potassium-lye  exactly  as  above  described.  The 
potash  must  be  cautiously  added  to  the  hot  cosine  liquid  in  small  portions.  The 
further  conduct  of  the  operation  and  the  testing  are  effected  as  with  the  sodium  salt. 
The  yield  is  30  kilos. 

Tetraiodofluoresceine.  Erythrosine  B. — The  iodising  of  the  fluoresceine  is  effected 
in  the  same  manner  as  the  bromising,  only  with  the  difference  that  no  mineral  acid, 
but  acetic  acid,  is  used  for  setting  up  the  reaction,  as  it  can  dissolve  iodine,  and  hence 
allows  it  to  react  in  a  finer  state  of  division. 

In  an  enamelled  double  pan  of  100  litres  capacity  there  are  dissolved  6  kilos. 
fluoresceine  in  a  hot  mixture  of  8  kilos,  soda-lye  at  62°  Tw.  and  60  litres  of  water.  In  a 
similar  pan  of  equal  size  there  are  dissolved  24  kilos,  of  iodine  (not  sublimed)  in  27  to  28 
kilos,  of  soda-lye  at  62°  Tw.  and  60  litres  of  water.  The  liquid,  which  is  at  first  brown, 
and  afterwards  colourless,  is  boiled,  and  is  then  run  off  into  a  wooden  vat  of  600  litres 
capacity  (set  in  a  low  place),  as  is  also  the  solution  of  fluoresceine.  After  the  mixture 
has  been  thoroughly  stirred  25  kilos,  of  glacial  acetic  acid  are  run  out  of  a  stone- 
ware vessel,  in  a  stream  of  about  the  thickness  of  a  finger,  into  the  alkaline  mixture, 
with  vigorous  stirring.  Fluoresceine  and  iodine  are  separated  out  in  a  state  of  the 
finest  division,  and  substitution  takes  place.  When  all  the  glacial  acetic  acid  has  been 
added  the  iodine  is  boiled,  neutralised  with  1 7  kilos,  of  lye,  and  a  mixture  of  2  5  litres 
water  and  25  kilos,  hydrochloric  acid  is  added  within  the  lapse  of  three  minutes.  The 
vat  is  then  filled  up  with  water,  boiled,  and  allowed  to  settle.  The  hot  iodine  solution 
is  separated  after  about  an  hour  from  the  red  precipitate  of  tetraiodo  fluoresceine  by 
decantation  into  a  wooden  vat.  The  deposit  is  placed  upon  an  alkaline  filter,  drained, 
returned  to  the  cask,  and  boiled  up  once  more  there  with  about  300  litres  of  water  and 
10  kilos,  hydrochloric  acid.  This  decantation  and  boiling  are  repeated  once  more,  but 
without  the  hydrochloric  acid.  The  free  iodeosic  acid  is  placed  on  a  filter,  allowed 
to  drain  thoroughly,  the  brick-red  paste  is  spread  out  thinly  upon  enamelled  drying 
capsules  placed  on  the  water-bath,  and  dried.  The  red  powder  is  then  sifted.  The 
yield  is  1 5  kilos. 

For  obtaining  the  ammonium  salt  the  sifted  iodeosine  is  placed  upon  frames  and 
exposed  to  the  action  of  ammonia  in  a  chest  as  above  described.  The  excess  of 
ammonia  is  cut  off  as  soon  as  a  sample  appears  completely  soluble.  The  yield  is  15-3 
kilos,  erythrosine  B. 

Bi-iodoftuoresceine.  Erythrosine  G. — The  less  iodised  product,  consisting  chiefly  of 
bi-iodo  fluoresceine,  is  obtained  if  we  use  only  16  kilos,  iodine  instead  of  24,  proceeding 
otherwise  exactly  as  above. 

Fluoresceine,  6  ;  lye,  8;  iodine,  16;  lye,  20;  acetic  acid,  20;  lye,  17;  hydrochloric 
acid  I.,  25  kilos.;  hydrochloric  acid  II.,  10  ;  yield,  12-9;  sal-ammoniac,  8;  CaO,  16; 
erythrosine  G,  13-2. 

By  methylating  the  eosine  the  potassium  salt  of  tetrabromfluoresceinemethylether 
is  obtained,  and  is  sold  as  erythrine,  spirit-eosine. 

Phloxine  P  is  the  potassium  salt  of  tetrabromdichlorfluoresceine,  which  is  obtained 
by  the  action  of  bromine  upon  dichlorfluoresceine.  By  methylating  phloxine  we  obtain 
cyanosine,  and  cyanosine  B  is  formed  by  ethylating  tetrabromtetrachlorfluoresceine, 
whilst  phloxine  T  is  produced  by  bromising  tetrachlorfluoresceine  in  an  alcoholic 


SECT,  iv.]  BENZOL   COLOURS.  557 

solution.     Ease  Bengale  is  formed  by  the  action  of  iodine  upon  dichlorfluoresceine,  and 
Rose  Bengale  B  by  iodising  tetrachlorfluoresceine,  e.g. : — 


C 


C.HBr..O.CH,  /CJHI..OK  ,C.HBr..OK 


o  0 jo  0!    o 

C6HBr2.OK  U   C6HI2.OK  V   C6HBr2.OK 


Cyanosine.  Rose  Bengale.  Rose  Bengale  B. 

Sesorcine  Blue,  Lacmoid,  is  formed  by  heating  resorcine  with  sodium  nitrite.  By 
the  action  of  nitrous  acid  upon  resorcine  there  is  produced  dinitroresorcine,  or  solid 
Green,  C6H4(N"02)2  or  C6H2(O.NOH)3,  which  dyes  a  green  on  tissues  mordanted  with 
iron. 

With  tetramethyldiamidobenzophenon  chloride  resorcine  gives  resorcine  violet,  which 
is  not  met  with  in  commerce. 

Auramines. — The  simplest  members  of  this  series  are  pure  yellow  colouring  matters, 
which  are  formed  from  the  tetra-alkylised  diamidobenzophenones  (or  their  haloid  deri- 
vatives) by  the  action  of  ammonia  upon  the  methan  residue.  From  these  dyes  there 
are  prepared  phenyl-,  tolyl-,  naphthyl-auramines  of  redder  or  browner  tones  by  heating 
with  aniline,  its  homologues  and  its  derivatives  (substituted  in  the  benzol  nucleus), 
naphthylamine,  &c.,  with  the  elimination  of  ammonia.  These  same  substituted 
auramines  are  obtained  by  the  immediate  action  of  the  amines  concerned  upon  the 
above-named  ketone  bases  and  their  haloid  derivatives.  If  tetramethyldiamidobenzo- 
phenone  and  tetraethyldiamidobenzophenone  are  used,  practically  useful  results  have 
been  obtained  hitherto  with  ammonia,  aniline,  para-  and  orthotoluidine,  metaxylidine 
and  phenylenediamine,  cumidine,  a  and  /3  naphthylamine. 

Free  ammonia  does  not  act  upon  the  ketone  bases,  but  upon  their  haloid  derivatives. 
If,  e.g.,  the  product  obtained  by  treating  tetramethyldiamidobenzophenone  with  phos- 
phorus chloride  in  presence  of  an  indifferent  solvent  is  mixed  with  concentrated 
ammonia,  with  good  refrigeration,  a  yellow  colour  at  once  appears,  and  after  some  time 
auramine  separates  out  in  a  crystalline  form.  More  advantageous  is  the  direct  action 
of  the  ketone  bases,  which,  on  heating  with  ammonium  chloride,  acetate,  tartrate, 
benzoate,  or  sulphocyanide,  especially  with  the  aid  of  zinc  chloride  or  other  dehydrating 
agents,  can  be  easily  converted  into  auramines. 

There  is  put  into  an  enamelled  pan  provided  with  an  oil  or  air  bath,  and  previously 
heated  to  about  200° —  e.g.,  an  intimate  mixture  of  25  kilos,  tetramethyldiamidobenzo- 
phenone (obtained  by  saturating  dimethylaniline  with  COC12) — 25  kilos,  sal-ammoniac, 
and  25  kilos,  zinc  chloride.  The  mixture  gradually  melts  down  and  takes  a  deep  yellow 
colour.  To  promote  the  fusion  of  the  mass  it  is  thoroughly  stirred  from  time  to 
time.  If  the  temperature  within  the  melt  is  about  150°  to  160°,  the  colouring  matter  is 
formed  in  from  three  to  five  hours.  The  end  of  the  reaction  is  recognised  when  a  sample 
of  the  melt  dissolves  almost  completely  in  hot  water.  The  cold,  solid  mass  is  broken  up, 
and  first  treated  with  cold  water  acidified  slightly  by  hydrochloric  acid,  so  as  to  remove 
the  bulk  of  the  excess  of  sal-ammoniac  and  zinc  chloride.  The  residue  is  then 
exhausted  with  hot  water,  and  the  extract,  previously  filtered  from  any  unattacked 
ketone  base,  is  precipitated  with  sodium  chloride.  The  crystalline  precipitate  can  then 
be  easily  rendered  perfectly  pure  by  re-crystallisation  from  water.  The  colouring 
matter  is  the  hydrochlorate  of  imidotetramethyldiamidodiphenylmethan — 

(C6H4.N(CH3)2 
C-NH  +  HSO. 

C6H4.N(CH3),HC1 

The  hydrochlorate,  sulphate,  and  acetate  are  relatively  easily  soluble  in  water,  less 
easily  the  double  zinc  chlorides,  whilst  the  hydriodic  and  hydrosulphocyanic  salts 


558  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

dissolve  with  difficulty,  or  scarcely  in  the  cold.  The  watery  and  alcoholic  solutions  are 
not  fluorescent.  On  the  addition  of  mineral  acids  there  is  at  first  no  change  ;  but  on 
prolonged  standing,  or  more  rapidly  when  heated,  there  then  occurs  decolorisation,  whilst 
the  ketone-base  is  re-formed  and  ammonia  is  split  off.  Alkaline  reducing  agents  —  e.g., 
sodium  amalgam  —  slowly  decolorise  the  alcoholic  solution  in  the  cold.  On  the  addition 
of  water  there  separates  out  a  colourless  crystalline  reduction  product.  The  acetic 
solution  is  scarcely  coloured,  but  on  heating  it  at  once  takes  a  deep  blue  colour.  This 
process  depends  on  splitting  up  the  reduction  product  into  ammonia  and  tetramethyl- 
diamidobenzhydrol.  On  heating  the  auramine  with  aniline  to  the  boiling-point  of  the 
latter,  ammonia  is  evolved,  and  the  mixture  contains  the  orange-yellow  dye  plienyl- 
auramine. 

Nitrosodimethylaniline,  C6H4.NO.N(CH3)2,  a  very  important  material  for  the 
preparation  of  many  colouring  matters,  is  obtained  by  dissolving  2  parts  dimethyl- 
aniline  in  5  parts  strong  hydrochloric  acid  and  10  parts  of  water,  and  adding  the 
required  quantity  of  sodium  nitrite.  Nitrosodimethylaniline  separates  out. 

This  salt  yields  with  metaphenylenediamine  the  hydrochlorate  of  dimethyl- 
diamidophenazine,  called  neutral  violet;  with  metatoluylenediamine  it  forms  the 
hydrochlorate  of  dimethyldiamidotoluphenazine,  neutral  red. 

Both  are  spoken  of  as  eurhodines. 

Indophenol, 

N(C6H4.N.(CH3)3, 
1CH0 


10 


is  formed  by  the  action  of  nitrosodimethylaniline  upon  a-naphthol,  or  by  the  oxidation 
of  amidomethylaniline  and  a-naphthol.     It  is  insoluble  in  water. 

New  Blue,  Naphthylenene  Blue  B,  Cotton  Blue  R,  Fast  Blue  for   Cotton,   the 
chloride  of  dimethylphenylammonium-/3-naphthoxazine, 


is  formed  from  nitrosodimethylaniline-/3-naphthol.  It  is  easily  soluble  in  water,  with 
a  violet-blue  colour. 

The  similar  colouring  matter,  Muscarine,  is  formed  from  nitrosodimethylaniline 
hydrochlorate  with  a-dioxynaphthaline,  and  with  a-naphthylamine  it  yields  Nile  Blue. 

Gallocyanine  (Solid  Violet],  the  chloride  of  dimethylphenylammoniumdioxyphene- 
oxazine  carbonic  acid,  is  formed  from  nitrosodomethylaniline  with  gallic  acid.  It  is 
insoluble  in  water,  whilst  the  colouring  matter,  Prune,  obtained  in  a  similar  manner 
from  gallic  methyl  ether,  is  easily  soluble. 

Methylene  Blue  is  the  hydrochlorate  or  zinc  double  chloride  of  tetrarnethylthionine. 
According  to  Caro,  dimethylaniline  is  converted  by  sodium  nitrite  into  nitrosodimethyl- 
aniline, reduced  by  hydrogen  sulphide  to  amidodimethylaniline,  which  is  finally 
oxidised  by  ferric  chloride.  Or  it  may  be  first  oxidised  and  then  treated  with  ferric 
chloride.  The  colouring  matter  is  precipitated  from  the  splendid  blue  solution  with 
common  salt  and  zinc  chloride.  Or  nitrosodimethylaniline  is  dissolved  in  sulphuric  acid, 
of  sp.  gr.  1-40,  converted  by  zinc  sulphide  into  the  leuko-base  of  methylene-blue,  which 
is  then  oxidised  (Ethylene  Blue}. 

Methylene  Blue  is  characterised  by  its  fine  blue  tone,  slightly  verging  on  green, 
and  its  fastness  against  soap  and  light.  It  dissolves  readily  in  water,  dyes  cotton  with- 
out a  mordant,  and  is  distinguished  from  aniline  blues  by  the  odour  of  dimethylaniline 
which  it  evolves  if  boiled  with  caustic  alkali. 

The  manufacture  of  methylene  blue  includes,  according  to  Miihlhausen  —  i,  the 
production  of  the  solution  of  nitrosodimethylaniline;  2.  the  sulphurising;  3,  the 
oxidation  ;  4,  the  precipitation  ;  and  lastly,  the  filtration. 

For  obtaining  the  solution  of  nitrosodimethylaniline  there  is  prepared  a  solution 


SECT,  iv.]  BENZOL  COLOURS.  559 

of  dimethylaniline  hydrochlorate  and  a  solution  of  sodium  nitrite.  Into  each  of  three 
vats  there  are  poured  1200  litres  of  water.  To  this  is  added  a  mixture,  previously 
prepared,  of  10  kilos,  dimethylaniline  and  i  carboy  of  hydrochloric  acid  at  30°  Tw., 
which  are  best  mixed  in  an  enamelled  vessel,  stirring  the  dimethylaniline  into  the 
hydrochloric  acid,  which  has  been  previously  diluted  with  about  50  litres  of  water. 

For  preparing  the  nitrite  solution  there  is  put  into  each  nitrite  vessel  correspond- 
ing to  the  three  colour  vats  6'6  kilos,  of  sodium  nitrite  (at  98  per  cent.)  and  about  150 
kilos,  of  water.  After  about  twelve  hours  the  cocks  of  the  nitrite  vessels  are  opened, 
and  the  solution  is  run  during  two  hours  through  a  leaden  funnel-tube,  which  reaches 
to  the  bottom  of  the  colour  vats.  The  temperature  of  the  solution  before  nitroising  is 
from  8°  to  9°,  but  afterwards  from  10°  to  12°.  In  summer  or  winter  the  temperature 
is  regulated  with  ice  or  steam.  Constant  agitation  is  kept  up  during  the  nitroising, 
and  afterwards  2  carboys  of  hydrochloric  acid  are  added  to  each  vat. 

The  object  of  the  sulphurising  is  to  expel  the  excess  of  nitrous  acid,  to  reduce  the 
nitroso-compound  to  an  amine,  and  to  saturate  the  liquid  with  hydrogen  sulphide. 
The  development  of  the  sulphuretted  hydrogen  is  effected  with  quite  fresh  moist  soda- 
mud  (i.e.,  vat- waste).  A  pail  filled  with  soda-mud  has  the  net  weight  of  35  kilos. 
The  contents  of  two  such  pails  suffice  to  expel  the  nitrous  acid  of  all  the  three  vats. 
Into  each  vat  there  is  put  by  means  of  a  shovel  ^  pailful.  A  yellowish-green  froth 
appears,  and  on  adding  another  J,  orange  vapours  of  nitrous  acid  are  expelled  by  the 
sulphuretted  hydrogen,  which  dissolves  in  the  water.  These  operations  require  constant 
stirring,  and  last  about  five  minutes.  The  liquid  then  smells  of  sulphuretted  hydrogen. 

Previous  to  reduction  we  then  add  to  each  vat  two  more  carboys  of  hydrochloric 
acid,  and  then  begin  to  introduce  the  vat- waste.  Each  vat  receives  at  intervals  of  i  J 
to  2  hours  four  or  five  pails  of  the  vat-waste.  On  adding  each  pail  (which  takes  about 
two  minutes)  the  agitator  is  set  in  action  in  order  to  distribute  the  mud  equally  at 
the  bottom  of  the  vats.  Caution  is  here  needed,  as  the  mass  easily  overflows,  which 
may  be  prevented  by  stopping  the  agitator  in  time.  After  the  mud  has  been  thrown 
in,  the  agitator  is  stopped,  so  that  the  development  of  the  sulphuretted  hydrogen 
may  proceed  quietly  and  slowly,  and  it  may  have  full  opportunity  for  dissolving,  but 
little  for  escaping.  The  reduction  is  generally  complete  by  the  introduction  of  the 
fourth  pail.  A  strip  of  filter-paper  dipped  in  the  liquid  should  no  longer  show  the 
characteristic  nitrose  margin.  As  the  liquid  remains  standing  over  night,  half  or  one 
pail  is  added  for  subsequent  development,  according  as  the  reduction  and  saturation 
have  made  more  or  less  progress. 

After  adding  the  soda-mud  the  solution  becomes  a  milky  white,  and  contains 
chiefly  amidodimethyline  hydrochlorate  and  small  quantities  of  a  sulphuretted  base, 
which  both  yield  the  blue  colouring  matter,  also  milk  of  sulphur  and  the  residue  of  the 
mud,  along  with  some  sulphide  not  attacked,  and  which  may  subsequently  cause  irre- 
gularities in  the  production  of  the  colouring  matter.  The  calcium  chloride  formed 
does  not  come  into  consideration. 

During  the  sulphurising  the  liquor  undergoes  a  series  of  changes  in  colour,  which 
prove  that  not  merely  diamine  but  colouring  matter  is  formed,  which  is  partly 
reduced  to  methylene  white,  and  partly  converted  into  methylene  red  by  being  more 
highly  sulphured.  The  following  table  shows  the  observations  made  during  such  a 
reduction : — 


56° 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


Number 
of  Pails. 

Heat  after 
adding 
Mud. 

Time. 

Reaction  on  Filter-paper. 

Appearance  of  Liquor. 

I* 

1  6° 

9.20  a.m. 

Pure  yellow 

Brownish-yellow 

10.15 

Yellow,  orange 

Black-green 

10.30 

Yellow,  orange,  red 

Black 

2 

174 

11.5 

Black-brown 

11.25 

Yellow,  red,  blue 

Black 

"•45 

Yellow,  red,  very  strong 

Deep  black 

3 

19 

12.0    noon 

Chocolate 

12.30  p.m. 

Yellow,  blue  and  red 

Blue 

4 

20 

1.50 

Very  blue 

5t 

21 

2.50 

Red 

4.0 

Colourless 

The  oxidation  is  effected  by  the  addition  of  ferric  chloride,  of  sp.  gr.  i'i6  to  1*17, 
which  corresponds  to  20-21  per  cent.  FeaCl6,  to  the  sulphured  liquid.  Ferric  chloride 
is  added  until  the  smell  of  sulphuretted  hydrogen  has  entirely  disappeared  and  a  slight 
excess  of  iron  chloride  is  present.  For  the  oxidation,  four  carboys  of  ferric  chloride, 
containing  each  70  kilos,  of  the  above-mentioned  sp.  gr.,  are  nearly  always  sufficient. 

Whether  enough  has  been  added  can  be  judged  at  once  by  the  eye.  The  oxidised 
liquor  must  appear  of  a  deep  blue ;  if  it  is  reddish-blue  the  oxidation  is  not  quite 
sufficient. 

It  sometimes  happens  that  the  oxidised  liquid,  after  standing  for  some  time,  again 
evolves  sulphuretted  hydrogen  ;  in  this  case  also  a  little  more  ferric  chloride  is  to  be 
added.  These  accidents  are  due  either  to  an  irregular  introduction  of  the  mud  or  to 
imperfect  stirring. 

The  tests  for  ascertaining  whether  a  vat  has  received  enough  ferric  chloride  are  the 
following  : — A  sample  precipitated  with  common  salt  and  a  little  zinc  chloride  is  placed 
upon  a  slip  of  filter-paper,  and  the  opposite  margin  is  touched  with  a  solution  of 
potassium  f errocyanide ;  if  a  faint  blue  spot  appears  where  the  two  liquids  meet, 
sufficient  ferric  chloride  has  been  added.  If,  on  the  contrary,  a  slip  of  filter-paper 
dipped  in  the  colour-liquor  becomes  darker  if  touched  with  ferric  chloride,  more  ferric 
chloride  must  be  added  to  the  bulk. 

"When  the  solutions  are  perfectly  oxidised,  the  colouring  matter  is  salted  out. 

For  precipitation  180  kilos,  of  rock-salt  are  stirred  into  each  vat,  and  as  this 
effects  only  a  partial  precipitation,  there  are  further  added  to  each  2  5  kilos,  zinc  chloride 
at  sp.  gr.  1-5. 

In  order  to  ascertain  whether  the  colouring  matter  is  completely  precipitated,  a  slip 
of  filter-paper  is  dipped  into  the  liquid  and  examined  by  reflected  light;  if  all  the 
colour  has  been  deposited  we  see  blue  flocks  on  a  red  ground.  If  the  ground  is 
blue  or  blueish-red,  more  salt  and  zinc  chloride  must  be  added.  As  soon  as  the  test 
indicates  complete  precipitation,  the  liquid  is  at  once  filtered  through  a  double  woollen 
filter  laid  over  a  tub. 

The  filtration  is  effected  with  constant  agitation,  and  takes  two  to  three  hours. 
The  crude  colour  is  on  the  filter,  and  the  red  liquid  is  caught  in  the  tub  below.  In 
the  upper  colour-vat  there  is  still  a  residue.  It  is  baled  into  a  wooden  trough  and 
elutriated  with  water  until  it  no  longer  gives  off  any  colour.  The  watery  extract  is 
placed  along  with  the  crude  colour  in  the  extraction  cask  ;  the  residue  is  thrown  away. 
The  crude  colour  is  turned  over  with  a  wooden  shovel  to  promote  drainage  and  is  then 
ready  for  extraction. 

The  crude  colour  consists  of  methylene  blue,  a  residue  of  mud,  sulphur,  and  dregs  of 
salt  tinged  with  blue. 


Initial  temperature,  14°. 


t  The  fifth  pail  was  not  entirely  added. 


SECT,  iv.]  BENZOL  COLOURS.  561 

The  red  filtrate  is  worked  up  for  a  zinc  colour ;  36  kilos,  of  zinc  powder  are  stirred 
up  to  a  paste  with  a  little  water,  to  each  vat  there  are  allowed,  therefore,  12  kilos, 
of  zinc.  The  paste  is  put  in  with  iron  spoons ;  a  spoonful  being  briskly  stirred  into 
each  vat  every  ten  minutes.  The  liquid  foams ;  streams  of  sulphuretted  hydrogen 
escape.  Zinc  is  thus  added  until  the  liquor  becomes  colourless.  There  is  now  added  to 
each  vat,  stirring  vigorously,  a  carboy,  equal  to  70  kilos,  ferric  chloride,  which  gives  a  deep 
blue  solution,  from  which  the  colouring  matter  is  at  once  deposited  on  account  of  the 
salt  and  zinc  chloride  present.  The  contents  of  the  vats,  after  being  well  stirred  up, 
are  filtered.  The  liquid  flows  away  and  a  zinc  colour  remains  on  the  filter. 

In  order  to  work  up  the  crude  colour,  the  dissolving  cask  is  filled  up  with  water 
and  heated  with  steam  to  24°.  Into  the  water,  which  is  mixed  with  18  kilos,  ferric 
chloride,  is  poured  the  crude  colour  from  six  vats ;  it  is  stirred  up  until  the  water  is  per- 
fectly saturated  with  colouring  matter  and  adhering  salts,  allowed  to  settle,  and  the 
better  to  clear  the  liquid  a  few  handfuls  of  salt  are  strewn  upon  the  surface  of  the 
solution.  After  twelve  hours'  rest  the  coloured  liquid  is  drawn  off  by  means  of  a 
syphon  into  another  tub  fixed  below.  On  filtering  the  solution  it  is  well  to  let  the  first 
turbid  portions  of  the  filtrate  run  upon  a  second  filter,  also  placed  over  the  lower  vat, 
and  as  soon  as  the  solution  is  clear  it  is  passed  through  another  filter.  The  filtrate  is 
now  completely  salted  out  with  200  kilos,  of  clean  salt  and  30  kilos,  zinc  chloride.  As 
soon  as  perfect  precipitation  has  been  effected  it  is  filtered  at  once  through  a  filter  below, 
passing  previously  through  a  fine  sieve  to  keep  back  any  coarse  particles  of  rock  salt.  The 
colouring  matter  is  then  well  drained. 

The  extraction-tub  is  then  again  filled  with  water,  heated  to  24°,  and  mixed  with  18 
kilos,  of  ferric  chloride.  The  residue  left  on  the  filter  is  stirred  in,  and  the  contents  are 
further  treated  as  in  extract  No.  i .  In  the  third  extraction  there  are  only  added 
9  kilos,  ferric  chloride,  proceeding  otherwise  as  before.  As  all  the  salts  are  dissolved 
out,  this  extract  yields  the  finest,  strongest,  and  purest  colour.  There  is,  especially  in 
this  colour,  no  more  methylene  red.  Sometimes  it  may  be  necessary  to  make  four 
extracts,  but  in  general  three  suffice.  The  residue  on  the  filter  and  in  the  cask  is 
placed  in  the  boiling  vat,  where  it  is  opened  up  with  hydrochloric  acid. 

The  boiling  vat  is  half  filled  with  water ;  the  contents,  well  stirred  up,  are  mixed  with 
15  kilos,  hydrochloric  acid  and  heated  to  boiling.  The  liquid,  deep  blue  at  first,  becomes 
pale  blue  and  even  colourless,  and  nitrous  acid  escapes.  As  soon  as  the  mass  boils,  30 
kilos,  of  ferric  chloride  are  added  and  filtered  at  once  into  a  tub  below.  The  purpose 
of  the  boiling  is  the  reduction  of  the  methylene  blue  attached  to  finely  divided  sulphur. 
The  filtrate  is  re-oxidised  within  the  lower  cask  with  8  kilos,  ferric  chloride,  and  then 
salted  out  with  150  kilos,  rock-salt  and  30  kilos,  solution  of  zinc  chloride.  If  the  residue 
in  the  boiling-vat  is  not  yet  entirely  opened  up  (rarely  the  case),  a  further  extraction 
is  made,  the  vat  being  only  one-quarter  filled  with  water. 

The  zinc  colour  from  the  six  additional  casks  is  placed  in  the  boiling-vat  and  there 
stirred  up  with  cold  water.  The  liquid  is  then  allowed  to  settle  for  twelve  hours  and 
filtered  into  a  tank  below.  The  filtrate  is  mixed  with  10  kilos,  ferric  chloride,  150  kilos, 
rock-salt,  30  kilos,  solution  of  zinc  chloride,  and  filtered.  The  residue  on  the  filter  is 
returned  to  the  vat.  The  vat  is  now  filled  one-quarter  with  water  and  heated  as  above, 
but  only  with  40  kilos,  salt  and  6  kilos,  solution  zinc  chloride.  The  second  extract  of 
zinc  colour  is  generally  omitted,  working  so  that  when  the  boiling  colour  from  the  raw 
colour  vat  arrives  in  the  boiling  tank  the  first  extract  of  the  zinc  colour  is  just 
finished. 

According  to  the  working  up  of  the  crude  colouring  matters  we  have  three  sorts 
of  extract :  pure  colour,  zinc  colour,  and  boiling  colour  on  the  filter.  After  each 
filtration  the  colour  on  the  filter  is  scraped  up  and  drained  in  a  pointed  woollen  bag 
filter;  when  the  last  saline  liquor  runs  off.  The  colours  then  are  mixed  in  a  cask, 

2    K 


562 


CHEMICAL   TECHNOLOGY. 


[SECT.  iv. 


and  for  mixing,  water  is  added  until  it  begins  to  dissolve  colour  also,  and  not- 
merely  salts — i.e.,  until  a  slip  of  paper  moistened  with  the  solution  is  coloured  faintly 
blue.  The  paste,  allowed  to  stand  for  some  hours,  is  passed  through  bag  niters, 
wrapped  in  strong  cotton  cloths  and  pressed  under  a  screw-press.  The  press  cakes  so 
obtained  are  dried  on  zinc  plates,  cut  up  with  wooden  spatulse,  and  dried  in  a  drying- 
room  at  60°. 

Instead  of  mixing  the  three  grades  of  colour,  they  may  all  be  worked  up  separately. 
The  pure  colour  is  then  the  finest  and  strongest,  and  the  boiling  colour  the  weakest.  If 
these  colours  are  mixed  up  with  water,  the  pure  colour  is  blue  and  the  zinc  colour  and 
boiling  colour  grey.  Similar  is  the  behaviour  of  the  pressed  and  dried  colours.  The 
yield  for  every  vat  is  5  to  6  kilos.  The  colour  when  ground  is  a  bronze  powder.  The 
following  table  gives  a  view  of  the  numbers  given  above  : — 


Oil. 

HC1 

NaNOg 

Na  or  N 
Waste. 

Fe2Cl& 

Rock 

Salt. 

ZnCl2 

»ine 
Powder. 

Sodium 
Chlo- 
ride. 

Yield. 

Crude  colour  . 
Pure  colour  A  I. 

30 

1050 

19-8 

500 

1050 
18 

540 

75 
30 

36 

2OO 

— 

AH.     . 

— 

— 

— 

— 

18 

— 

30 

— 

2OO 



A  III. 

— 

— 

— 

— 

9 

— 

3° 



2OO 



Boiling  colour  A  I. 

— 

15 

— 

— 

38 

— 

30 

— 

150 



Zinc  colour 

— 

— 

— 

10 

— 

30 



»5P 



Finished  product    . 

— 

— 

— 

— 

— 

— 

— 

36 

60 

2115 

39-6 

IOOO 

2193 

1  080 

300 

72 

900 

36 

The  Zinc  Sulphide  Process. — If  sulphuretted  hydrogen  is  passed  into  sulphuric 
acid  at  72°-98°  Tw.,  sulphur  separates  out  and  the  sulphuric  acid  is  reduced  to 
sulphurous  acid  :  H2S04  +  SH2  =  SO2  +  S  +  aH20. 

The  sulphurous  acid  again  is  at  once  decomposed  in  contact  with  H2S  with  further 
liberation  of  sulphur :  S02  +  2H2S  -  2H20  +  38. 

If  this  liberation  of  sulphur  takes  place  in  presence  of  nitrosodimethylaniline 
sulphate  it  is  converted  into  a  colourless  sulphur  base,  which,  when  oxidised,  yields  a 
blue  dye-stuff.  For  nitrising  the  following  plant  is  required:  3  enamelled  iron  pans, 
each  holding  400  litres,  fitted  with  agitators  and  cooling  jackets ;  3  sulphuring  pans, 
each  containing  1500  litres,  with  cooling  jackets;  escapes  for  sulphuretted  hydrogen 
gas ;  pressure  gauge  and  cover  fitted  with  a  man-hole  (the  agitator  and  the  pan  are  lined 
with  lead);  a  settling  beck  with  a  box-filter,  and  below  it  an  oxidation  vat;  finally,  a 
purifying  system  consisting  of  a  redissolving  vat  and  a  precipitating  tank  with  a  box; 
filter. 

The  materials  needed  are :  methylaniline,  sodium  chloride,  zinc  chloride,  of  qualities 
as  above  mentioned  ;  sulphuric  acid,  both  of  40°  and  of  130°  Tw. ;  the  former  is  obtained 
by  mixing  23  kilos,  sulphuric  acid  and  50  kilos,  water;  the  latter  from  150  kilos, 
sulphuric  acid  and  22^  kilos,  water.  The  zinc  sulphide  must  be  pure,  dry,  and  finely 
sifted. 

The  production  of  the  crude  colour  comprises:  i,  nitrising;  2,  sulphuring;  3, 
clearing ;  and  4,  oxidation. 

Into  each  nitroso-pan  there  are  stirred  10  kilos,  methyl-aniline  and  75  kilos,  of  the 
weak  sulphuric  acid ;  the  mixture  is  cooled  down  to  6°  to  8°  with  ice,  and  a  solution  of 
6\  kilos.  NaN02  in  30  kilos,  water  is  run  in  from  a  bottle  fitted  with  a  cock,  and' 
with  constant  agitation,  the  temperature  not  being  allowed  to  rise  above  12°.  When 
this  operation  is  at  an  end  the  mass  is  mixed  with  175  kilos,  of  the  stronger  sulphuric- 
acid,  keeping  the  temperature  at  12°.  The  contents  of  the  pans  charged  in  this 
manner  are  now  forced  up  by  means  of  compressed  air  into  the  sulphurising  pans. 


SECT,  iv.]  BENZOL  COLOUES.  563 

The  mass  is  sulphurised  by  introducing  dry  zinc  sulphide,  ground  to  an  impalpable 
powder,  in  lots  of  100  kilos.,  and  with  continual  stirring,  keeping  the  temperature  at  20° 
to  25°.  After  entering  the  zinc  sulphide  the  pan  is  closed,  and  the  contents  are  digested 
at  35°  to  40°,  until  the  reaction  is  completed.  This  is  indicated  by  the  decolorising 
of  the  solution,  which  has  been  in  succession  light  green,  blue,  dark  blue,  and  finally 
red.  All  the  contents  of  the  pans  are  forced  into  the  settling  beck,  which  holds  3000 
litres  of  water,  and  after  being  well  mixed  up  they  are  left  to  settle  for  twelve  hours. 
The  sulphur  is  then  filtered  off,  the  liquid  is  boiled  again  with  5  kilos,  of  sulphuric  acid 
and  1000  litres  water,  allowed  to  subside,  and  filtered.  The  united  filtrates  are  oxidised 
as  above  described  with  5  carboys  of  ferric  chloride,  the  colouring  matter  is  precipitated 
with  common  salt,  and  filtered. 

This  colour  is  purified  by  redissolving  and  treating  as  already  described.  The  blue 
produced  in  this  manner  has  a  considerably  higher  tinctorial  power  than  the  product 
obtained  by  the  former  process. 

Lauth's  Violet  (Thionine)  is  similar  in  composition  to  methylene  blue : 

C6H3.NH2  (C6H3.N(CH3)2 

1ST-      S  NJ     S 

C6H3.NH.HC1  (C6H3(CH3)C1 

Lauth's  violet.  Methylene  blue. 

It  is  obtained  by  oxidising  paraphenylondiamine  in  an  acid  solution  containing 
hydrogen  sulphide. 

Bernthsen  heats  10  parts  diphenylamine  with  4  parts  sulphur  in  a  cohobater  to 
250°  to  300°  for  two  hours,  or  until  the  end  of  the  reaction  is  indicated  by  cessation  of 
the  development  of  sulphuretted  hydrogen.  The  crude  thiodiphenylamine  is  purified  by 
distillation  and  repeatedly  recrystallising  from  alcohol  the  light-yellow  distillate  which 
solidifies  in  crystals.  For  nitrising  it  is  introduced  with  good  cooling  and  agitation  by 
degrees  into  5  parts  of  nitric  acid  at  72°  Tw.  The  pasty  mixture  is  then  put  in  much 
cold  water,  and  the  nitro-compound,  which  separates  out  as  a  light-yellow  powder,  is 
filtered  and  washed.  It  is  sparingly  soluble  in  alcohol  and  benzol,  more  readily  in 
glacial  acetic  acid.  Instead  of  free  nitric  acid  the  well-known  nitrising  mixtures  can 
be  used.  For  reducing  this  nitrised  thiodiphenylamine  the  usual  reducing  agents  may 
be  taken — e.g.,  stannous  chloride,  iron,  tin,  or  zinc,  with  hydrochloric  acid,  &c.  If 
tin  and  hydrochloric  acid  are  used,  the  mixture  proceeds  very  quickly  with  the  applica- 
tion of  heat,  the  nitro-compound  dissolves,  and  there  is  formed  a  colourless  solution, 
from  which,  after  tin  has  been  removed  by  H2S  or  zinc,  a  double  zinc  chloride  is  to  be 
obtained  by  evaporating  the  hydrochlorate  of  the  leuko-base.  This  leuko-base  is 
characterised  by  the  reaction  that  on  saturation  with  ammonia  it  is  on  contact  with, 
an  oxidising  agent  at  once  resolved  into  a  violet  colouring  matter. 

The  oxidation  of  the  above-mentioned  reduction-product  can  be  conveniently  effected' 
with  the  colourless  solution  freed  from  tin  by  means  of  zinc.  On  the  introduction  of 
ferric  chloride  in  slight  excess  there  appears  at  once  an  intense  violet  precipitation 
of  the  sulphuretted  colouring  matter,  which,  if  necessary,  can  be  completed  by  the 
addition  of  common  salt.  After  filtering  off  the  precipitate  it  may  be  further  puri- 
fied by  recrystallisation  from  boiling  water.  The  colour  may  also  be  obtained 
perfectly  pure,  and  in  the  form  of  fine  crystalline  needles,  if  the  concentrated  aqueous 
solution  is  precipitated  by  the  addition  of  hydrochloric  acid.  When  dry  the  colour- 
ing matter  is  a  green  crystalline  powder  of  a  metallic  lustre,  soluble  in  concentrated 
sulphuric  acid  with  a  green  colour,  which,  as  Avater  is  added,  becomes  first  blue  and 
then  violet.  The  colouring  base,  when  set  at  liberty  by  alkalies,  is  red,  and  dissolves 
in  ether  with  a  yellowish-red  colour.  If  heated  in  a  dry  state,  the  colour  is  decom- 
posed with  liberation  of  sulphuretted  hydrogen.  The  watery  solution  has  an  intense 
violet  colour,  and  is  quickly  decolorised  by  reducing  agents,  such  as  zinc-powder,  tin, 


564  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

and  hydrochloric  acid,  solution  of  hydrosulphite,  &c.  Oxidising  agents  quickly  restore 
the  colour.  The  dye-stuff  fixes  itself  directly  upon  animal  fibre,  and  is  peculiarly  suit- 
able for  dyeing  animalised  or  tanned  cottons. 

By  the  introduction  of  alcohol  radicles  into  the  molecule  there  are  formed  colouring 
matters  of  violet-blue  to  bluish-green  tones. 

Induline,  Nigrosine,  Azodiphenyl  Blue,  Violinaniline,  Couplers  Blue,  Fast  Blue, 
Printing  Blue,  Acetine  Blue  may  be  best  obtained  by  heating  amidoazobenzol  with 
aniline  hydrochlorate  : 

C6H5.NH,  +  C6H6.N.NC6H4.NHf  =  NH3  +  C18H15N3 
Aniline.  Amidoazobenzol.  Induline. 

Induline  is  converted  into  a  more  valuable  colouring  matter  if  it  is  again  treated 
with  aniline  salts  in  presence  of  aniline.  For  this  purpose  we  heat  in  an  enamelled 
cast-iron  pan  100  kilos,  induline  hydrochlorate  (azodiphenyl  blue),  45  kilos,  aniline  hydro- 
chlorate,  and  200  kilos,  of  aniline  to  1 60°  to  170°  for  twenty- four  hours.  The  thick  melt, 
when  cool,  is  mixed  with  500  litres  of  alcohol.  Fine  brass-coloured  crystals  of  the  new 
colouring  matter  separate  out,  which  are  collected  on  a  filter,  purified  by  washing  with 
alcohol,  and  dried.  To  effect  the  formation  of  induline  and  its  transformation  in  one  and 
the  same  operation,  we  mix  in  an  enamelled  pan  100  kilos,  diazoamidobenzol  with  130 
kilos,  of  aniline  hydrochlorate  and  300  kilos,  pure  aniline.  The  molecular  transforma- 
tion of  the  diazoamido  compound  is  effected  by  standing  for  twenty-four  hours,  or  more 
rapidly  by  heating  to  40°  or  50°,  and  it  is  then  heated  for  four  to  five  hours  to  1 10° .  The 
melt  is  now  of  a  deep  violet  colour,  and  still  contains  traces  of  amidoazobenzol.  It  is  ad- 
vantageous, though  not  strictly  necessary,  to  add  65  more  kilos,  of  aniline  hydrochlorate, 
and  then  to  heat  for  twenty-four  hours  to  160°  to  170°.  The  blue  thus  obtained  is  then 
converted  into  a  sulpho-aoid  by  heating  with  3  parts  sulphuric  acid  of  sp.  gr.  1-840  to 
110°  for  six  hours.  The  sulpho-acid  is  then  converted  into  the  sodium  salt  which 
forms  the  commercial  product.  This  new  colouring  matter,  C36H27N8HC1,  induline 
6B,  formed  from  induline  with  liberation  of  ammonia,  is  distinguished  from  the  well- 
known  colour  by  its  complete  insolubility  in  alcohol  and  its  pure  greenish-blue  tone, 
which  does  not  vary  in  artificial  light.  The  indulines  are  distinguished  by  fastness. 

Sajfranine  (Aniline  Hose)  is  a  mixture  of  tolusaffranines  and  phenotolusaffranines. 
The  colouring  matter,  which  dissolves  in  water  with  a  red  colour,  is  formed  by  the 
oxidation  of  i  mol.  each  of  aniline,  orthotoluidine,  and  paratoluylendiamine. 

Phenosaffranine,  H2N.C6H3.N2.C6H4.C6H4.NH2.C1  (Saffranine  B  extra),  is  formed 
by  oxidising  paraphenylendiamine  with  2  mols.  aniline.  It  forms  green  crystals, 
which  dissolve  in  water  with  a  red  colour. 

Neutral  Blue  is  formed  from  nitrosodimethylaniline  with  phenylnaphthylamine, 
and  Bale  Blue,  from  nitrosodimethylaniline  with  ditolylnaphthylendiamine. 

Girofle  is  obtained  from  nitrosodimethylaniline  hydrochlorate  and  a  mixture  of 
meta-  and  para-xylidine  hydrochlorate. 

Aurantia  (Imperial  Yellow),  the  ammonium  salt  of  hexanitrodiphenylamine, 

N[C6H2(N02)3]2.NH4, 
is  formed  on  treating  diphenylamine  with  nitric  acid. 

2.  Phenol  Colouring  Matters. — Phenol  serves  for  the  production  (besides  the  azo- 
dyes)  of  the  following  colours  : — 

Picric  Acid  (Trinitrophenol),  C6H2(N02)3OH,  is  formed  by  the  action  of  nitric  acid 
upon  phenol,  or  by  treating  crystallised  sodium  phenol  sulphonate  with  nitric  acid.  It 
crystallises  in  yellow  leaflets,  sparingly  soluble  in  cold  water,  but  readily  in  alcohol  and 
in  hot  water.  It  melts  at  122°,  and  deflagrates  if  rapidly  heated.  It  is  used  in  dyeing 
yellows,  and  in  the  form  of  a  picrate  with  aniline  green  (iodine  green),  and  with  indigo 
or  Prussian  blue  for  obtaining  green,  upon  silk  or  wool.* 

*  It  does  not  bear  soaping. 


SECT,  iv.]  PHENOL  COLOURS.  565 

It  has  happened  that  instead  of  the  free  acid  its  sodium  salt  has  been  sold  under  the 
names  of  picric  acid  and  aniline  yellow,  and  has  given  rise  to  very  serious  accidents  in 
consequence  of  its  explosive  character. 

In  France  large  quantities  of  picric  acid  are  regularly  made,  not  for  dyeing,  but 
for  producing  picrate  powder.  If  treated  with  potassium  cyanide,  picric  acid  yields 
isopurpuric  acid  (C8H5N506),  whilst  trinitrocresolic  acid  yields  cresylpurpuric  acid 
(C9H7!N"506),  the  potassium  and  ammonium  salts  of  which  are  known  as  garnet  brown. 
As  garnet  brown  explodes  with  great  violence  on  sh'ght  friction,  it  is  generally  sold  as 
a  paste.  To  prevent  the  paste  from  drying  up  it  is  mixed  with  a  little  glycerine.* 

Phenyl  Brown(Phenicine,Rotheine)  was  obtained  by  Roth  in  1865,  and  is  sometimes 
used  in  silk  and  woollen  dyeing.  It  is  formed  by  treating  phenol  with  a  mixture  of 
sulphuric  and  nitric  acids.  Phenyl  brown  is  an  amorphous  powder — a  mixture  of  two 
colouring  matters,  the  one  yellow  (according  to  Bolley  dinitrophenol,  C6H4(N02)20), 
and  a  blackish-brown  compound  allied  to  the  humoids.  Phenyl  brown  is  no  longer  met 
with  in  commerce. 

Flavaurine  (New  Yellow),  the  ammonium  salt  of  dinitrophenolparasulpho-acid, 
C6H8(NOa)2.S03NH4,  is  obtained  by  treating  niononitrophenolparasulpho-acid  with 
nitric  acid. 

Victoria  Yellow  (Saffron  substitute,  Victoria  Orange,  Aniline  Orange)  is  a  mixture  of 
the  potassium  and  ammonium  salts  of  dinitro-,  ortho-,  and  para-cresol, 

C6H2.CH3(N02)2OK, 

obtained  by  treating  ortho-  and  para-cresolsulpho-acid  or  diazotoluol  with  nitric  acid. 
It  has  been  recently  proved  that  this  dye-stuff  is  poisonous.  Hence  it  cannot  be  used 
for  colouring  articles  of  food,  &c.,  as  a  substitute  for  saffron. f 

(C6H4.OH) 

Aurine  C-jCJHLOHf  is  obtained  by  heating  i  part  phenol  with  0*5  part  sulphuric 
IC6H40     J 

acid  (at  sp.  gr.  i'S4)  and  o-6  to  0*7  part  oxalic  acid,  to  120°  to  130°.  The  yield  is  60 
to  70  per  cent.  It  may  also  be  produced  by  heating  a  mixture  of  i  mol.  phenol,  2 
mols.  cresol,  3  niols.  sulphuric  acid  and  pulverised  arsenic  acid  to  120°.  On  lixiviating 
the  mass  with  water,  aurine  remains  as  a  resinous  mass  of  a  metallic  green  colour, 
yielding  a  yellowish-red  powder.  Commercial  aurine,  also  called  rosolic  acid,  contains, 
besides  aurine,  oxidised  aurine,  methylaurine,  pseudorosolic  acid,  &c.  It  is  soluble  in 
water  and  insoluble  in  alcohol. 

Coralline  (Peonine,  Aurine  fi)  is  obtained  by  treating  aurine  with  ammonia,  and  is 
probably  rosaniline  rosolate. 

Azuline  (Azurine,  Rosolic  Blue]  impure  triphenylpararosaniline  hydrochlorate,  is 
obtained  by  heating  rosolic  acid  with  aniline. 

Here  also  belongs  the  substance  first  isolated  by  Reichenbach  from  beech  wood  tar 
under  the  name  of  pittacal.  It  is  now  found  to  consist  of  the  deep-blue  salts  of 
eupittonic  acid,  C25H2609  =  C19H8(O.CH3)603. 

Quinoline,  C9H7N,  a  constituent  of  coal-tar,  formerly  obtained  by  distilling 
cinchonine  with  sodium  hydrate,  is  now  obtained  from  phenol  synthetically.  Skraup 
heats  i -4  kilo,  of  ortho-,  meta-,  or  para-nitrophenol  with  2'i  kilos,  of  one  of  the  three 
amidophenoles,  6  kilos,  glycerine  at  sp.  gr.  1-26,  and  5  kilos,  sulphuric  acid  of  sp.  gr. 
1*845,  ^°  I3°°  ^°  r4°c-  When  the  reaction  is  complete,  the  volatile  impurities  are 
distilled  off  in  a  current  of  steam,  the  mass  is  neutralised  with  soda,  the  volatile 
orthoquinoline  is  distilled  off  in  a  current  of  steam,  and  the  other  compounds  are 
precipitated  with  soda. 

According  to  the  statement  of  the  works  formerly  Meister,  Lucius  and  Bruning, 

*  Garnet  brown  is  scarcely  ever  used  in  dyeing. 

t  In  England  saffron  is  rarely  used  as  a  colour  for  food,  except  in  Cornwall. 


566  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

the  orthonitrobenzylidenacetone  obtained  from  benzylidenacetone  by  nitrising  passes 
into  methylquinoline  or  quinaldine  on  treatment  with  reducing  agents  : — 
C6H4.N02.CH.CO.CH3  +  3H2  =  C6H4.C3H2.CH3.N  +  3H20. 

For  the  reduction  of  orthonitrobenzylidenacetone,  stannous  chloride  and  hydro- 
chloric acid  are  the  most  suitable.  For  20  parts  orthonitrobenzylidenacetone,  there  are 
used  75  parts  stannous  chloride  and  75  parts  hydrochloric  acid  (of  sp.  gr.  1*2)  diluted 
with  the  same  quantity  of  water.  The  formation  of  methylquinoline  is  effected  with  a 
strong  liberation  of  heat.  The  mass  is  then  mixed  with  hydrate  of  lime  in  excess,  and 
the  new  base  is  distilled  off  in  a  current  of  steam.  Methylquinoline,  which  may  be  used 
in  the  preparation  of  the  azo-dyes,  boils  about  240°,  and  yields  very  finely  crystalline 
salts.  It  is  also  formed  from  aniline  and  aldehyde : — 

C6H7N  +  2C2H4O  =  C10HtN  +  2H2O  +  Hs. 

According  to  Dobner  and  Miller  the  reaction  of  the  aldehydes  with  aniline  ensues 
always  on  the  same  principle  as  with  acetaldehyde,  2  mols.  aldehyde  reacting  with 
i  mol.  aniline  so  that  2  mols.  water  and  one  mol.  hydrogen  are  split  off. 

Acetaldehyde  .  .  2C2H40  +  C6H7N  =  C10H9N  +  2H20  +  H2 
Propionaldehyde  .  2C3H6O  +  C6H7N  =  C,,HISN  +  2H20  +  H2 
Normal  Butylaldehyde  2C4H80  +  C6H7N  =  C,4H17N  +  2H20  +  H3 
Isovaleraldehyde  .  2C6H100  •*.  C6H7N  =  C16H21N  +  2H20  +  H3 
(Enanthaldehyde  .  2C7H140  +  C6H7N  =  C20H29N  +  2H2O  +  H2 

The  most  important  quinoline  colours  are — 

Quinoline  Green,  the  hydrochlorate  of  tetramethyldiamidodiphenylquinolyl  carbinol 
obtained  from  quinoline  and  tetramethyldiamidobenzophenonchloride  is  not  now  an 
article  of  commerce. 

Quinoline  Blue,  Cyanine,  is  obtained  from  the  product  of  the  reaction  of  amyliodide, 
quinoline,  and  methylquinoline. 

Quinoline  Red  is  produced  if  benzotrichloride  is  heated  with  quinaldine  and 
isoquinoline  in  presence  of  zinc  chloride.  In  preparing  quinoline  red  from  benzotri- 
chloride and  the  quinoline  of  coal-tar,  not  more  than,  at  the  outside,  one  molecule  of 
quinoline  can  thus  be  converted  into  colouring  matters.  According  to  the  experiments 
of  A.  W.  Hof  mann  in  preparing  quinoline  red  the  simultaneous  presence  of  isoquinoline 
and  quinaldine  is  requisite.  If  a  mixture  of  i  moL  isoquinoline  and  i  mol.  quinaldine  is 
heated  in  presence  of  zinc  chloride  and  benzotrichloride  the  colour  is  formed  at  120°, 
and  the  yield  is  much  larger.  The  analysis  of  the  colouring  matter  leads  to  the  formula 
C26H1SN2C1,  the  exact  formula  which  might  be  expected  on  the  assumption  that  in 
its  formation  i  mol.  quinoline,  i  mol.  quinaldine,  and  i  mol.  benzotrichloride  are 
condensed,  whilst  2  mols.  hydrochloric  acid  are  split  off,  as  in  the  formation  of 
malachite  green. 

C8HUN      +       C8HUN      +       C7H5C13          =      CaTLKTS,Cl      +      2HC1 
Dimethylaniline.     Dimethylaniline.     Benzotrichloride.          Malachite  green. 

C,H7N     +     C10H9N     +     C7H5C13  =     C26H19N2C1     +     2HC1 

Chinolin.  Chinaldin.  Chinolinroth. 

( CH  C  H  N~i 
Quinoline  Yellow,  C ' In  jj  nr^f)}'*8  ^orme<^  on  heating  quinaldine  with  phthalic 

anhydride  and  zinc  chloride.  In  order  to  render  it  soluble  in  water  it  is  converted  into 
a  sulpho-acid  by  treatment  with  concentrated  sulphuric  acid,  and  this  again  is  trans- 
formed into  the  sodium  salt. 

Perhaps  as  important  as  the  quinoline  colouring  matters  are  the  quinoline  nostrums 
such  as  antipyrine  and  thalline.* 

*  Of  these  substances,  antipyrine  is  the  only  one  which  has  not  since  been  found  to  be 
injurious. 


SECT,  iv.]  NAPHTHALINE   COLOUES.  567 

Salicylic  Acid,  C6H4.OH.CO.OH,  formerly  obtained  from  oil  of  winter-green  and  other 
vegetable  matters,  is  now  produced  synthetically  from  phenol. 

According  to  Kolbe's  directions,  phenol  is  evaporated  to  dryness  with  the 
quantity  of  soda-lye  needed  to  form  phenol  sodium,  C6H5ONa  in  an  iron  retort 
and  heated  to  180°.  Carbon  dioxide  is  then  introduced  until  no  more  phenol  distils 
over  on  slowly  heating  at  from  226°  to  250° : 

2C6H5ONa  +  COS  =  CGH5OH  +  CGH4.ONa,COONa. 

The  sodium  salicylate  obtained  is  dissolved  in  water,  acidified  with  hydrochloric 
acid,  the  salicylic  acid  liberated  is  separated  from  the  lime  and  purified. 

According  to  the  works,  formerly  Hofmann  and  Schotensack,  phenol  and  soda- 
3ye  are  heated  in  a  double  pan  provided  with  an  agitator  in  proportion  of  3  to  4 
mols.  evaporated  to  dust-dryness,  phosgene  gas  is  introduced,  beginning  at  140°,  and 
the  temperature  is  gradually  raised  to  200°.  As  soon  as  the  phenol  is  distilled  off  to  go 
per  cent,  of  its  calculated  quantity  the  operation  is  stopped,  the  dusty  residue  of  basic 
sodium  salicylate  is  dissolved  in  water,  and  crude  salicylic  acid  is  precipitated  by  means 
of  carbonic  acid,  the  last  portion  of  phenol  having  first  been  driven  off  by  a  current  of 
steam  after  the  addition  of  i  mol.  hydrochloric  acid  to  i  mol.  salicylic  acid. 

At  Schering's  works,  50  kilos,  diphenyl-carbonate  and  54  kilos,  phenol-sodium  are 
heated  in  a  pan  provided  with  an  agitator  at  from  160°  to  1 70°  for  six  hours.     From  the 
product  the  salicylic  acid  is  separated  in  the  known  manner.     The  reaction  takes  place 
according  to  the  equation — 
OC6H5.CO.OC6H5  +  2C6H5ONa  =  C6H4.ONa.COO.Na  +  C6H.OC6H5  +  C6H5OH. 

Schroeder  finds  that  sodium  salicylate  is  formed  according  to  the  equation — 

C6HsONa  +  Na3C03  +  CO  =  C6H4.ONa.CO,Na  +  NaCHOs, 

if  carbon  monoxide  is  passed  over  a  mixture  of  sodium  phenylate  and  sodium  carbonate 
at  200°. 

Among  the  colours  obtained  from  salicylic  acid  the  most  important  are — 

Salicyl  Yellow,  the  mono-bromsalicylic  acid  or  its  sodium  salt, 

C6H,.Br.NOs.OH.COOH,  or  C6H,Br.NOs.ONa.COONa. 
This  compound,  like  Salicyl  Orange,  C6H.Br.(NOj).,ONa.COONa,  is  no  longer  in  use. 

Salicylic  acid  is  much  used  for  the  preservation  of  articles  of  food,  as  an  addition 
to  beer,  wine,  tfcc.,  it  is  generally  considered  objectionable.* 

3.  Naphthaline  Dye-stuffs. — Naphthaline,  C10HS,  forms  with  chlorine  addition  and 
substitution  products — e.g.  Naphthaline  tetrachlomde,  C10H8C14,  by  heating  naphthaline 
with  chlorine  gas,  which  is  converted  into  phthalic  acid  by  means  of  nitric  acid.  With 
naphthaline  there  arc  formed  only  substitution  products — e.g.,  C10H7Br.  Nitric  acid 
forms  in  the  first  place  a-nitroiiaphthalme,  C1(>HrN02,  which  is  converted  by  reducing 

/TVTTT     P*TT 

.agents  into  a-naphthylamine,  C10H7NH2,  or  C6H4 1  QJT  Q jj 

According  to  Witt,  naphthaline  used  for  the  production  of  a-naphthylamine  must 
have  the  following  properties  :  the  melting  point  must  be  exactly  79°,  the  boiling  point 
216°  to  217°.  A  little  cylinder  cast  of  the  product  to  be  tested,  exposed  to  the  free  air 
on  a  plate  of  glass,  should  entirely  evaporate  in  a  few  days  without  residue  and  remain 
white  to  the  last ;  i  gramme  of  the  naphthaline  heated  in  a  test-tube  with  pure  coii- 
-centrated  sulphuric  acid  at  from  170°  to  200°  must  not  colour  the  acid  red,  but  at 
the  outside  only  grey. 

The  agitator  used  in  nitrising  consists  of  four  to  six  wings  placed  obliquely  at  an 
angle  of  45°.  The  cast-iron  apparatus,  provided  with  a  cooling- jacket,  is  fitted  with  a 
lid  (left  out  in  Fig.  397),  the  one  half  of  which  may  be  thrown  open,  whilst  the  other 
has  a  wide  pipe  serving  for  the  escape  of  the  gases  formed.  The  lower  part  of  this 

*  Its  use  is  prohibited  in  France. 


568 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


Wasserzufluss 


Explanation  of  Terms. 
Wassennfluss    .     .     Entrance  for  water. 
Wasserobfluss     .     .     Escape  for  water. 


pipe  is  provided  with  a  steam  jacket,  so  that  any  naphthaline  which  congeals  in  the 
pipe  and  causes  an  obstruction  may  be  melted  out  from  time  to  time. 

The  agitator  is  set  in  slow  action  and  effects  a  gentle  but  complete  intermixture 

of  the  ingredients.     The  apparatus 

Fig-  397«  is  charged  with  2  50  kilos,  naphtha- 

line, 200  kilos,  nitric  acid  (72°  Tw.), 
and  200  kilos,  sulphuric  acid  (sp.  gr. 
1-84),  and  for  dilution  600  kilos,  of 
the  spent  acid  from  a  former  opera- 
tion. After  adding  the  acid  the 
agitator  is  put  in  action,  and  the 
introduction  of  the  finely  ground 
naphthaline  is  commenced.  The 
naphthaline  is  at  once  attacked 
by  the  acid,  the  temperature  rises, 
but  it  is  kept  from  45°  to  50°  by 
regulating  the  introduction  of  the 
material  and  by  letting  water  flow 
in  the  cooling-jacket.  At  this  tem- 
perature the  nitrising  proceeds 
quietly,  and  for  the  quantities  given 
it  is  completed  in  a  day.  The  con- 
tents are  then  run  out  at  a  cock  into  a  cistern  lined  with  lead.  On  cooling,  the 
naphthaline  is  deposited  on  the  surface  in  the  form  of  a  cake,  so  that  the  subnatant 
acid  may  be  kept  clear.  The  cake  of  nitro-naphthaline  is  freed  from  acid  by  boiling 
with  water  in  leaded  troughs,  and  finally  granulated  by  an  influx  of  cold  water 
with  continual  stirring. 

If  nitro-naphthaline  is  melted  or  the  water-bath  is  mixed  with  10  per  cent,  of 
cumol  or  solvent  naphtha,  we  obtain  an  oil  which  remains  fluid  for  a  long  time,  and 
can  be  filtered  and  dried  perfectly  by  means  of  calcium  chloride.  The  clear  mixture 
is  left  to  itself,  when  it  gradually  congeals  to  a  heap  of  very  fine  crystals.  If  the 
crystalline  cake  thus  obtained  is  placed  under  a  hydraulic  press  the  solvent  which 
had  been  added  flows  off  along  with  a  part  of  the  nitro-naphthaline,  and  may  be 
separated  by  distillation  in  a  current  of  steam,  and  recovered.  The  press  cake  consists 
of  fine  yellow  crystals  of  nitro-naphthaline,  which  readily  crumble  to  a  light  crystalline 
meal. 

The  reduction  of  nitro-naphthaline  is  effected  with  iron  and  hydrochloric  acid, 
exactly  as  in  the  preparation  of  aniline ;  600  kilos,  of  air-dried  naphthaline,  800  kilos. 
of  iron  borings,  and  40  kilos,  of  hydrochloric  acid  are  used.  The  iron  and  the  acid 
are  mixed  with  the  addition  of  some  water  and  heated,  and  soon  after  the  naphthaline 
is  added  in  portions  through  a  feeding-socket,  which  can  be.  closed  by  a  block  of  wood. 
The  agitator  is  kept  in  constant  motion.  The  reaction  is  rather  violent.  The  addition 
of  the  nitro-compound  must  be  so  regulated  that  the  entire  apparatus  is  warm  to  the 
touch,  corresponding  to  an  internal  heat  of  50°. 

When  the  addition  of  the  nitro-naphthaline  is  completed  the  apparatus  is  kept  in 
action  for  six  to  eight  hours,  the  right  temperature  being  maintained  by  admitting  steam 
through  the  hollow  shaft. 

Towards  the  end  of  the  process  samples  are  drawn  from  time  to  time  and  tested  for 
their  proportion  of  nitro-i  aphthaline  by  distillation  and  dissolving  the  distillate  in 
hydrochloric  acid. 

As  soon  as  the  reaction  is  complete,  milk  of  lime  is  added  (50  kilos,  are  sufficient 
for  the  quantities  above  given),  and  after  thorough  stirring  the  mass  is  removed 


SECT.    IV.] 


NAPHTHALINE   COLOURS. 


569 


from  the  apparatus.  Witt  assumes  that  the  ferrous  chloride  is  the  real  reducing 
agent,  and  that,  during  the  reduction,  it  is  converted  into  one  of  the  basic  chlorides, 
perhaps  Fe,C]4O.  In  this  case  the  reduction  would  be  expressed  by  the  equation 

24FeCl2  +  4C10H.NO,  +  4H50  -  i2Fe20140  +  4C10H7NH2. 

The  basic  chloride  formed  is  in  turn  attacked  by  the  excess  of  iron,  or  reduced  to 
ferrous  chloride,  which  exerts  a  new  or  reducing  action  upon  nitre-naphthaline — • 
i2Fe3Cl40  +  9Fe  -  sFe304  +  24FeCl2. 

For  the  distillation  of  naphthaline  there  are  used  the  so-called  stage-retorts 
(Figs.  398  and  399),  into  which  the  masses  to  be  sublimed  are  inserted  in  flat  sheet- 
iron  boxes.  The  retorts 

are  well  heated,  and  in  Fi%-  39& 

order   to   convey    away  "i? 

quickly  the  vapours  of    \v         MfiVi •• •»  •mmium  IB  i   mmaaan- •  ^  mm,     J 

naphthylamine  steam  is 
blown  in.  from  above, 
and  the  steam-pipe  can 
easily  be  superheated  by 
the  fire  gases.  The  cast- 
iron  cooling-pipes  con- 
nected with  the  retorts 
lie  in  troughs,  in  which 
the  condensing  water  is 
kept  at  60°,  so  that  the 
pipes  may  not  be  blocked 
up  by  solidifying  naph- 
thylamine. The  naph- 
thylamine mixed  with 
some  water  distils  over 
as  a  blackish  oil,  and 
solidifies  in  the  receivers 
to  a  crystalline  mass.  For  conversion 
into  the  commercial  product  it  may 
require  to  be  rectified. 

ft-Waphthylamine, 

|CH.C.NH2 
'ICH.CH    "' 

is  obtained  by  heating  10  kilos.  /3- 
naphthol,  4  kilos,  caustic  soda,  and  4 
kilos,  sal-ammoniac  in  an  autoclave  at 
from  150°  to  1 60°  for  60  to  70  hours, 
or  /3-naphthol  sodium  with  sal-ammo- 
niac. It  melts  at  112°  and  boils  at 
294°,  whilst  a-naphthylamine  melts  at 
50°  and  boils  at  300°. 

a-Amidoazonaphthaline, 
N.C10H6.NH2, 

is  produced  when  a    solution    of    13 
parts  a-naphthylamine  is  mixed  with 
a  solution  of  3  parts  potassium  nitrate  and  2  parts  caustic  potassa.     Amidoazonaph- 
thaline  separates  out. 

a-Naphthylamine  yields  with  concentrated  sulphuric  acid  a  mixture  of  two  amido- 
naplithaline-sulplw- acids,  which  are  converted  by  nitrous  acid  into  diazonaphthaline- 


Explanation  of  Terms. 
Abzug  der  Feuergase    .     .    Outlet  for  combustible  gases. 


Fig.  399- 


an. 


570  CHEMICAL   TECHNOLOGY.  [SECT.  iv. 

sulpho-acids,    C10H6.N2.S03.      With   fuming    sulphuric  acid    a-naphthylamine    yields 


, 

<i-na2}Jithylamine,  a-sulpho-acid,  or  naphthionic  acid  CGH4lp  ^rv  fr  PTT- 

Naphthaline  heated  with  concentrated  sulphuric  acid  gives  a  mixture  of  a-  and  /3- 
monosulpho-acid,  C10H.S03H.  The  lime  salt  of  ^-naphthaline  sulpho-acid  is  much  less 
soluble  than  that  of  a-naphthaline  sulpho-acid  ;  hence  the  acids  are  generally  separated 
as  lime  salts. 


O  OTT 

a-Naphthol,    C6H4  -^pW  pir      •  ,  is  formed  from  a-naphthylamine  and  nitrous  acid,  but 


is  most  commonly  prepared  by  melting  a-naphthaline  sulpho-acid  with  caustic  soda. 

f  '"FT  o  OTT  ) 
For  the  production  of  /3-naphthol,  C6H4/  pTr'pVr      r,  2  parts  of  caustic  soda  are 

melted  with  a  little  water  and  i  part  of  /3-sodium  naphthaline  sulphate  is  added,  the 
temperature  being  slowly  raised  to  300°,  The  melt  is  dissolved  in  water,  decomposed 
with  hydrochloric  acid,  and  the  /3-naphthol,  which  separates  out,  is  purified  by  dis- 
tillation. 

If  treated  with  sulphuric  acid  both  the  naphthols  yield  various  naphthol-sulpho- 
acids.  Of  special  importance  is  the  /3-n.aphtholmonosulpho-acid  (Bayer),  Schaffer's 
/3-naphtholmonosulpho-acid  S,  and  the  two  /3-naphtboldisulpho-acids,  E,  and  G. 

Phthalic  Acid,  CGH4.(COOH)2,  is  obtained  by  heating  i  part  naphthalinetetrachloride 
with  5  to  6  parts  of  nitric  acid.  Phthalic  anhydride,  C6H4(CO),0,  is  obtained  by  sub- 
limation. 

Naphthaline  Red  (Magdcda  Red,  Soudan  Red,  A/rvhthaline  Scarlet],  the  cliamido- 
naphthylnaphthazionium  chloride,  C30H21N4C1,  is  obtained  by  heating  a-amidoazonaphtha- 
line  with  a-naphthylamine. 

According  to  Witt,  23-1  kilos,  of  naphthylendiamine  hydrochlorate,  28-6  kilos,  of 
a-naphthylamine,  and  59^4  kilos,  of  amidoazonaphthaline  are  melted  together  and  heated 
at  from  130°  to  140°,  until  the  original  violet,  the  colour  of  the  mixture,  has  changed 
to  a  pure  red  and  no  longer  increases  in  intensity.* 

Martius's  Yellow  (Novhthol  Jelloio,  Manchester  Yellow)  is  ammonium-,  sodium-,  or 

calcium-salt  of  dinitro-a-naphthoi,  C6H4  j^^'^0* 

tc.isro2.CH. 

It  is  prepared  by  treating  a-napthylamine,  a-naphtholsulpho-acid,  or  naphthionic  acid 
with  nitric  acid. 

According  to  Wickelhaus  and  Darmstadter,  dinitronaphthol  is  obtained  by  sulphuris- 
ing naphthaline  ;  the  /3-acid,  which  is  formed  along  with  the  a-acid,  is  removed  as  a 
calcium  salt,  and  the  former  is  converted  into  a-naphthol  by  melting  with  caustic 
potassa,  C10H7S02OK  +  K.OH  =  C10H7.OH  +  K,S03,  and  then  nitrising  the  naphthol. 

Martius's  yellow  dyes  wool  and  silk  in  all  tones,  from  the  lightest  yellow  to  a  full 
gold,  without  a  mordant  ;  i  kilo,  of  the  dry  calcium  or  sodium  compound  is  sufficient 
to  dye  200  kilos,  of  wool  a  fine  yellow.  A  chief  property  of  the  Martius's  yellow  is  that 
it  bears  steaming,  whilst  picric  acid  is  volatilised  along  with  the  watery  vapours.  It  is 
often  used  for  modifying  red  and  gold-yellow  tar  colours. 

Naphthol  Yellow  S,  Acid  Yellow  /S,  the  sodium  salt  of  dinitro-a-naphtholsulpho  acid 
is  obtained  by  treating  a-naphtholtrisulpho-acid  with  nitric  acid. 

Brilliant  Yellow  is  the  sodium  salt  of  dinitro-a-naphtholmonosulpho-acid,  which  is 
formed  by  treating  a-naphtholdisulpho-acid  with  nitric  acid. 

Sun  Gold,  the  sodium  salt  of  tetranitro-a-naphthol,  C10H3(N02)4ON"a,  no  longer 
occurs  in  trade. 

*  It  is  more  permanent  than  magenta,  saffranine,  and  the  eosines,  and  is  characterised  by  its 
strong  fluorescence. 


SECT,  iv.]  ANTHRACENE   COLOURS.  571 

Naphthol  Green  B  is  the  ferrous-soda  compound  of  nitroso-/3-naphtholmono-sulpho- 

fS03Na203S] 
acid,  C10H5  JO  0 1 C10H5,  is  obtained  by  treating  the  /3-naphtholmonosulpho-acid  S. 

(NO  re  ON] 

•with  nitrous  acid. 

Phenanthrene  Red,  the  sodium  salt  of  a-naphthyl-a-sulpho-acid  osazonphenanthren- 
quinone,  CfiH4.CN.CH.C10H6.S03Na,  is  obtained  from  naphthylhydrazinsulpho-acid  and 
phenanthrenquinone.  The  azo-colours,  capable  of  being  obtained  from  naphthaline  and 
naphthol,  are  especially  numerous. 

4.  Anthracene  Colours.*  The  most  important  of  the  anthracene  compounds  are 
the  alizarines. 

Alizarine,  a-/3-dioxyanthraquinone,  CUH804  or  CGH4(CO)2C6H2(OH)2.  The  anthra- 
quinone obtained  according  to  the  original  process  of  Graebe  and  Liebermann  was  con- 
verted by  bromising  into  bibromanthraquinone,  C14H6Br02,  and  the  latter  again  was 
transformed  into  alizarine  potassium  (or  sodium)  by  heating  with  caustic  alkali  to  180°  to 
200°.  From  the  alizarine  potassium  the  alizarine  was  separated  by  hydrochloric  acid. 

C]4H6Br202  +  4KOH  =  C14H6K204  +  2BrK  +  2H20 

Bibrorn-Anthraquinone.  Alizarine  potassium. 

C14HGK204  +  2HC1  =  C14H804  +  2KC1 
Alizarine  potassium.  Alizarine. 

According  to  the  process  now  generally  in  use,  alizarine  is  obtained  from  anthra- 
quinone  by  treating  one  part  with  4  to  5  parts  sulphuric  acid  of  sp.  gr.  1-84  at  a  tem- 
perature of  from  270°  to  290°.  It  is  first  converted  into  aiithraquinonedisulpho  acid, 
C14HG02(HS03)2 ;  this  acid  is  neutralised  with  calcium  carbonate,  the  liquid  is  filtered 
off  from  the  gypsum,  and  sodium  carbonate  is  added  until  all  the  lime  is  precipitated. 
The  clear  liquid  is  evaporated  to  dryness,  and  the  saline  mass  obtained  is  converted 
into  alizarine  sodium  by  heating  with  caustic  soda  at  from  250°  to  270° ;  from  the  melt 
thus  obtained  the  alizarine  is  precipitated  with  acid. 

In  converting  sublimed  anthracene  into  anthraquinone  : 

_  C14H10  +  K2Cr207  +  4H2S04  =  CUH8O2  +  K2Cr2(S04)4  +  5H20: 
the  required  quantity  of  potassium  clichromate  is  first  ascertained  by  a  preliminary  ex- 
periment. The  proper  quantity  of  potassium  dichromate  is  placed  in  a  wooden  tank 
lined  with  lead  (fitted  with  an  agitator  and  holding  3  cubic  metres)  along  with  1500 
litres  of  water  which  are  heated  to  a  boil  by  admitting  steam,  the  steam  is  shut  off,  100 
kilos,  powdered  anthracene  are  gradually  added,  and  whilst  stirring  gently  for  nine 
hours  the  requisite  quantity  of  dilute  sulphuric  acid  (sp.  gr.  i'24)  is  run  in. 
When  the  reaction  is  at  an  end  the  solution  of  chrome  alum  is  drawn  off  in  order 
to  convert  the  chromic  oxide  (which  has  been  precipitated  by  lime)  into  chromate  again. 
The  anthraquinone  is  washed,  dried,  dissolved  in  sulphuric  acid  at  100°,  and  when  cold 
precipitated  by  the  addition  of  water. 

In  preparing  the  anthraquinone  sulpho-acids  ordinary  sulphuric  acid  was  used  at 
first.  But  in  order  to  convert  the  anthraquinone  into  a  sulpho-acid  it  was  necessary  to 
heat  to  a  very  high  temperature,  which  involved  much  loss.  At  present  it  is  found  pre- 
ferable to  use  sulphuric  acid  containing  a  proportion  of  sulphuric  anhydride.  The 
anthraquinone  is  mixed  with  the  calculated  quantity  of  sulphuric  acid  and  heated  to  a 
higher  or  lower  temperature  according  as  the  intention  is  to  produce  the  mono-  or  the 
disulpho-acid.  In  preparing  the  disulpho-acid,  all  the  anthraquinone  is  dissolved, 
heating  until  a  sample  if  poured  into  water  dissolves  completely,  whilst  in  preparing 
the  mono-acid  a  portion  of  the  anthraquinone  remained  undissolved.  As  far  back  as 
1871  it  was  known  that  only  the  sodium  anthraquinone  monosulpho-salt  yielded 

*  Compare  AuerbacKs  Anthracen,  edited  by  W.  Crookes,  F.R.S.    London  :  Longmans. 


572  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

pure  alizarine,  and  the  endeavour  then  was  to  obtain  as  pure  a  raonosulphate  as  possible 
for  obtaining  the  "  blue  cast."  In  the  sulphurising  process  it  was  not  practicable  to 
obtain  the  monosulpho-acid  directly,  and  the  makers  were  therefore  obliged  to  separate 
it  out  from  a  mixture  of  the  different  sulpho-acids.  The  sulpho-acid  obtained  at  a  high 
temperature  was  neutralised  with  lime,  and  the  calcium  salt  formed  was  converted  into 
sodium  salt  by  means  of  sodium  carbonate.  On  evaporating  down  the  solutions  of  these 
sodium  compounds,  white  crusts  were  soon  separated  out,  which,  on  fusion  with  alkali, 
gave  a  very  blue  alizarine  and  proved  to  be  the  anthraquinone  monosulpho-salt  of 
sodium.  This  fractional  crystallisation  required  much  time,  and  it  was  therefore  an  im- 
provement when  it  was  found  that  from  a  mixture  of  the  mono-  and  the  disulpho-acid 
the  former  could  be  precipitated  first  by  alkali.  It  became  necessary  merely  to  par- 
tially neutralise  the  acids  with  caustic  soda  in  order  to  obtain  a  precipitate  of  the  mono- 
sulpho-salt. This  salt  was  filtered  and  the  filtrate  was  worked  up  for  alizarine  of  a 
"  yellow  tone." 

In  melting  the  anthraquinone  sulpho-salts  with  caustic  soda  the  alkali  takes  the 
place  of  the  sulphuric  residue  in  anthraquinone,  and  there  is  formed  sodium  alizarate. 
Alizarine  is  formed  only  out  of  anthraquinone  sulpho-acid.  If  the  alkali  were  to  act 
upon  this  acid  in  such  manner  that  merely  the  sulphuric  residue  would  be  substituted 
by  NaOH,  a  compound  would  be  formed  containing  one  atom  oxygen  less  than  does 
alizarine:  C14H7.S03Na02  +  NaOH  =  C14H7Na0.02  +  NaHS03. 

This  compound  is  monoxyanthraquinone.  If  alkali  acts  upon  this  compound  again 
it  has  an  oxidising  action  ;  one  atom  hydrogen  is  replaced  by  hydroxyl,  hydrogen  escapes, 
and  alizarine  is  formed  :  C14H7(O.Na)02  +  NaOH  =  C14H6(NaO)2O2  +  H2. 

In  the  action  of  alkali  upon  disulpho-acids,  at  first  the  true  sulphuric  acid  residues 
are  replaced  by  hydroxyls  and  there  are  formed  compounds  isomeric  but  not 
identical  with  alizarine.  On  further  action  of  the  melting  alkali  one  more  atom 
hydrogen  is  replaced  by  hydroxyl,  and  there  are  formed  colouring  matters  containing 
more  oxygen  than  the  alizarine — i.e.,  the  purpurines. 

Under  certain  circumstances,  however,  alizarine  is  also  formed  from  the  disulpho- 
acid,  but  only  in  small  quantity.  To  prevent  the  reducing  action  of  the  hydrogen, 
substance  is  added  which  gives  off  oxygen  and  oxidises  the  nascent  hydrogen  to 
water.  The  most  suitable  substance  is  potassium  chlorate. 

The  melting  process  has  undergone  important  changes  and  has  reached  a 
degree  of  perfection  which  leaves  little  room  for  improvements.  The  yield  of  colouring 
matter  has  risen  from  30  or  40  to  95  to  98  per  cent,  of  the  amount  theoretically  possible. 

The  form  of  the  autoclaves  can  be  varied  at  pleasure,  but  the  plates  must  be  strong 
enough  to  bear  a  pressure  of  15  to  20  atmospheres,  and  the  arms  of  the  agitator  must 
pass  very  close  over  the  edge  of  the  vessel  so  as  to  prevent  the  melt  from  being 
deposited.  The  safety-valve  is  connected  with  a  covered  vessel,  so  that  if  it  is 
opened  the  melt  is  not  scattered  about.  Whether  heat  is  applied  in  an  oil-bath  or  an 
air-bath  is  indifferent,  but  the  latter  has  the  advantage  that  the  temperature  can 
be  better  regulated  and  that  there  is  no  risk  of  fire.  In  the  air-bath  the  tempera- 
ture can  be  kept  perfectly  constant  for  days,  and  the  entire  melt  may  be  finished  in 
thirty-six  to  forty-eight  hours.  The  autoclave  is  charged  with  concentrated  soda-lye, 
the  sodium  sulphate  and  the  potassium  chlorate  are  added,  the  autoclave  is  closed,  the 
agitator  set  in  motion,  and  the  contents  heated  to  180°  to  210°.  In  a  relatively 
short  time  the  operation  is  at  an  end ;  the  melt  is  forced  through  a  pipe  into  a  vessel  of 
water  by  means  of  the  pressure  in  the  autoclave.  By  boiling  the  violet  solution  of  the 
melt  in  water  and  decomposing  the  alkaline  solution  with  an  acid,  the  colouring  matters 
are  obtained  in  the  state  of  yellow  or  orange  flocks,  which  are  passed  through  filter- 
presses,  freed  by  means  of  water  from  sodium  chloride  or  sulphate,  and  finally  made 
up  into  pastes  of  any  required  strength  by  adding  the  calculated  quantity  of  water. 


SECT,  iv.]  ANTHRACENE   COLOURS.  573 

Alizarine  VI.,  or  alizarine  I.,  or  the  a-/3-dioxyanthraquinone,  forms  an  ochre  yellow 
paste.     Alizarine  GI .;  Alizarine  FA.  ;  Flavopurpurine,  oxyanthraflavic  acid, 


C14H805  or 

which  is  prepared  by  melting  a-anthraquinone  disulpho  acid  soda  with  caustic  soda 
and  potassium  chlorate,  as  well  as  Alizarine  G.D.,  or  Alizarine  R.F.  isopurpurine 
anthrapurpurine,  oxyiscanthraflavic  acid, 

C14H805  or 

are  obtained  in  the  same  manner  from  /9-anthraqunionesulpho  acid  sodium  form 
brownish-yellow  pastes  and  dye  red  shades  on  cotton  mordanted  with  alumina. 

Purpurine,  trioxyanthraquinone,  obtained  by  the  oxidation  of  alizarine,  is  CUH80.  or 
C6H4(CO)2C6H(OH)3. 

A  lizarine  Orange,  Alizarine  N,  /3-monontroalizarine  : 

iCO)          (OH 
C14H:NOfi  or  C6H  C6H  OH 

'CO)       [NO, 

was  first  used  by  Strobel,  who  formed  it  by  the  action  of  nitrous  vapours  upon  cotton 
pieces  previously  printed  with  alizarine.  Subsequently  the  Baden  Aniline  Company  have 
supplied  this  colour,  made  according  to  Caro's  patent.  It  is  obtained  by  exposing 
alizarine  spread  out  in  thin  layers  to  the  action  of  nitrous  vapours  in  closed 
chambers,  or  by  passing  nitrous  acid  into  a  solution  of  alizarine  in  nitro  benzol.  It 
crystallises  in  orange-red  leaflets  with  a  green  reflection,  and  melts  at  230°. 

Alizarine  Carmine  (Alizarine  WS),  the  sodium  salt  of  alizarine  monosulpho  acid, 
C14H704.SO3Na,  is  obtained  by  treating  alizarine  with  concentrated  sulphuric  acid. 

The  aluminium  salt  dyes  woollens  without  a  mordant,  as  do  also  some  other  salts. 
It  is  better,  however,  to  mordant  the  wool  and  dye  up  with  the  sodium  salt  along  with 
tartar.  In  this  manner  different  tones  of  colour  can  be  obtained  from  the  same  dye- 
ware  by  using  various  mordants.  The  scarlets,  of  course,  cannot  rival  those  obtained 
with  cochineal,  eosine,  &c.,  in  brightness,  and  are  also  not  cheaper,  in  spite  of  the  low 
price  of  artificial  alizarine,  but  they  surpass  all  others  in  their  resistance  to  light  and 
air.  Flannels  dyed  with  alizarine  carmine  come  up  bright  after  every  washing,  and 
are  not  discoloured  by  the  action  of  perspiration,  as  are  goods  dyed  with  cochineal. 
They  may  also  be  exposed  without  injury  to  their  beauty  to  the  sun  and  the  weather, 
an  advantage  not  shared  by  the  other  tar-colours.  When  resistance  to  light  is  essen- 
tial, as  for  carpets,  curtains,  army  cloths,  &c.,  this  colour  deserves  especial  attention. 

Alizarine  blue,  C17H8N04  or 

rOH 

OH 

N.CH 

CH.CH 

is  formed  on  heating  with  glycerine  and  sulphuric  acid — 

C14H704(N02)  +  C3H803  -  C17H9N04  +  3H20  +  Or 

Alizarine  blue  is  met  with  in  the  form  of  a  thin  brownish- violet  paste,  containing 
i  o  per  cent,  of  colour.  The  colour  is  almost  insoluble  in  water  ;  in  benzol  and  alcohol 
it  dissolves  with  difficulty  with  a  red  colour.  From  its  benzol  solution  alizarine  blue  is 
obtained  in  violet-blue  needles  of  a  metallic  lustre,  fusible  at  270°.  It  forms  a  red 
solution  with  concentrated  sulphuric  acid.  If  this  solution  is  heated  for  some  time 
and  then  diluted  with  water,  a  blueish  sediment  is  deposited  having  the  same  properties 
as  a  dye-ware  as  the  original  alizarine  blue.  The  colour  is  soluble  in  a  solution  of 
sodium  bisulphite.  The  alizarine  blue  S  thus  obtained  contains  to  one  mol.  blue,  two 
mols.  sodium  bisulphite — CnH9N04.  2NaHS03. 


574  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

In  dilute  alkalis  the  dye- ware  dissolves  with  a  blue  or  a  greenish-blue 
colour.  After  some  time,  especially  in  presence  of  an  excess  of  alkali,  it  is  re-depo- 
sited as  an  insoluble  salt.  "With  calcium,  strontium,  and  barium  salts,  and  with  those 
of  iron,  it  forms  greenish-blue  lakes ;  with  alumina  violet  blues ;  with  chromic  oxide 
violets,  and  with  tin  red  violets.  Alizarine  blue  may  be  reduced,  like  indigo,  in  an 
alkaline  solution.  With  zinc-powder,  hyposulphurous  acid,  or  grape-sugar,  there  is- 
formed  in  presence  of  alkali  a  yellowish-brown  solution,  from  which  the  colouring  matter 
on  exposure  to  the  air  is  precipitated  with  a  fine  blue  colour.  Unmordanted  tissues,  if 
steeped  in  an  alizarine  blue  vat  and  then  exposed  to  the  air,  are  dyed  a  good  blue.  The 
vat  itself  is  red,  with  a  blue  scum.  After  airing,  the  dyed  goods  are  taken  through  a 
cold  chloride  of  lime  bath  or  through  a  solution  of  potassium,  chromate  mixed  with 
lime.  Alizarine  blue  has  not  come  into  general  use  since  the  indulines  can  also  be  used 
in  the  form  of  a  vat. 

5.  Azo  dyes  contain  the  group  — N  =  N — .  If  they  contain  this  group  twice  they 
are  named  tetrazo  dyes.  They  are  mostly  yellow  to  orange,  more  rarely  red.  Among 
the  great  number  of  these  dye-stuffs  the  following  may  be  mentioned : — 

Aniline  Yellow  (Spirit  yellow),  amidoazobenzol  C12H12N3C1  or  C6H4{^»'?-??  }is 

'-.N.N.CgH.j ) 

formed  by  heating  diamidoazobenzol  with  aniline  hydrochlorate.     Steel  blue  crystals 
which  dissolve  in  water  with  a  yellow  colour  and  on  treatment  with  fuming  sulphuric- 
acid,  yield  sodium  amidoazobenzclclisulphate,  C12H9N3(S03Na)3. 

Acid  Yellow  or  Fast  Yellow. — Fast  yellow  R,  Acid  yellow  R,  Yellow  W,  the  sodium 
salt  of  amidoazotoluoldisulpho  acid,  C14H13ISr3(S03lS'a)2,  is  obtained  by  treating  amido- 
azotoluol  hydrochlorate  with  fuming  sulphuric  acid. 

Bismarck  Brown  (Phenylen  Brown,  Gold  Brown,  Aniline  Brown,  Leather  Brown 

Cinnamon  Brown,  C12H15N.C12  or  Ce^ljq-.N.C  H  tNH2'2HCI)'  is  obtained  when 
dinitrobenzol  is  amidised  with  tin  and  hydrochloric  acid  and  then  treated  with  solution 
of  sodium  nitrite.  The  diazo  compound  of  aniline,  if  conjugated  with  naphthol  or 
naphtholsulphuric  acid : — 

Soudan  I,  C6H5.N.KC10H6[/3]OH 


Tropaolin  oooo,  C6H5.KN.C10H5 
Cochineal  scarlet  G,  C6H5.N.N.C10H5  {  g 
Crocein  orange  :  Ponceau  G  B, 
Orange  G,  C6H5.N.N.C10I 

Ponceau  2  G,  C6H5.N.N.( 

Diamidoazobenzol  with  2  mols.  sodium  nitrite  can  be  converted  into  a  tetrazo  compound,, 
which  may  unite  with  2  mols.  naphthylaminesulpho  acid,  a-naphtholsulpho  acid,  or 
/3-naphtholdisulpho  acid  R,  to  form  azo  dyes,  which  are  valuable,  as  they  dye  unmor- 
danted  cotton  directly  in  a  soap-beck. 

^  For  instance,  2-12  kilos,  pure  diamidoazobenzol  are  dissolved  in  5  kilos,  hydrochloric 
acid  of  30°  Tw.  and  100  litres  water,  and  converted  into  the  tetrazo  compound  by  the 
addition  of  a  solution  of  1-38  kilo,  sodium  nitrite  in  20  litres  water.  The  latter  is  then 
run  into  a  solution  of  6|  kilos,  sodium  a-naphthylamine  sulphate  and  ij  kilo,  soda 
in  200  litres  of  water,  stirring  constantly.  After  standing  for  twelve  hours,  the  pro- 
duct of  the  reaction  is  dissolved  by  boiling  in  water ;  the  colour  is  salted  out,  pressed,, 
and  dried.  It  dyes  cotton  in  an  alkaline  soap-beck  a  reddish- violet.  If  in  the  above 


SECT,  iv.]  AZO   DYES.  575 

mentioned  instance  the  sodium  a-naphthylarnine  sulphate  is  substituted  by  5  kilos, 
sodium  a-naphtholmono  sulphate  there  is  formed  a  sparingly  soluble  dye-stuff,  which 
works  on  unmordantecl  cotton  with  a  violet  colour. 

Azo  dyes  form  the  diazo  compounds  of  cliamidodiphenyl  ketones,  CO(C6H4.lSrH2)2. 
According  to  Wichelhaus,  the  amicloketon  is  obtained  from,  the  salts  of  rosaniline  and' 
pararosaniline,  commonly  known  as  magenta,  by  simply  boiling  with  hydrochloric  acid. 
If  this  process  is  continued  for  some  days  in  a  cohobator,  replacing  the  acid  which  has 
evaporated,  there  are  obtained  from  100  parts  of  magenta  30  parts  amicloketon,  with, 
corresponding  quantities  of  aniline  or  toluidine.  The  rest  of  the  magenta  is  un- 
changed, and  may  be  again  applied  in  a  similar  manner. 

In  order  to  separate  the  amidoketone  from  the  mixture  the  solution  is  rendered' 
alkaline,  the  aniline  or  toluidine  is  driven  out  by  a  current  of  steam,  and  the  residual 
bases  are  dissolved  in  dilute  sulphuric  acid,  taking  care  that  the  solution  is  perfectly 
neutral.  On  evaporation  the  formation  of  a  crystalline  scum  shows  the  condition  in> 
which  the  sulphate  of  the  amidoketone  crystallises  out,  the  rosaniline  or  pararosaniline 
sulphate  remaining  in  solution. 

For  the  production  of  dye-stuffs,  we  may  either  use  the  amidoketon  itself,  forming 
the  tetrazo  compound  by  the  action  of  sodium  nitrite  upon  the  chloride  of  this  base 
(with  refrigeration),  and  bringing  this  then  in  contact  with  phenole  bases  or  their 
sulpho  acids.  The  combination  leads — if  we,  e.g.,  use  resorcine  and  afterwards  salt- 
out  with  sodium  chloride — to  a  dye-stuff  of  the  formula — 

CO(CBH4N2)2.(C6H3.(ONa)2)3. 

It  dyes  an  intense  yellow  on  unmordanted  cotton  in  a  neutral  watery  solution. 

By  combining  the  tetrazo  compound  of  the  amidoketon  with  the  sodium  salt  of  naph- 
thionic  acid,  a  dye-ware  is  produced  of  the  formula  CO.(C6H4N2)2(C10H5(NH2)S03N"a)2> 
which  dyes  unmordanted  cotton  red  in  a  watery  solution.  Phenol  and  its  homologues, 
dimethylaniline,  other  phenols,  and  aromatic  bases,  as  well  as  the  sulpho  acids  of  these 
compounds,  unite  to  form  dye-wares  with  the  above-mentioned  tetrazo  compound. 


Benzopurpurine  4  B  -j  /ar»3v    Ks    f°rme(l    from      orthotolidine 


ICH, 

and  2  mols.  naphthionic  acid.  According  to  the  Berlin  Joint-Stock  Aniline  Com- 
pany, the  tetrazo  compounds  of  tolidine  formed  by  the  alkaline  reduction  of  ortho- 
or  paranitrotolual,  or  a  mixture  of  both  (i.e.,  the  technical  nitrotoluol),  form,  with 
a-  and  /S^naphthylamine  and  their  mono-  and  disulpho  acids,  fine  dye-stuffs,  partly- 
soluble  in  spirit  and  partly  in  water,  which  dye  unmordanted  cottons  in  a  soap-beck  a. 
series  of  tones,  from  a  deep  yellowish-red  to  a  bluish-red,  and  are  distinguished  from 
the  corresponding  benzidine  colours  by  their  superior  fastness  against  light  and  acids. 

Whilst  the  red  dye-ware  known  by  the  name  Congo,  obtained  from  tetrazodiphenyl 
with  a-naphthionic  acid,  is  turned  brown  or  black  by  the  slightest  trace  of  acetic  acid,, 
the  corresponding  product  from  ditetrazoditolyl  is  not  nearly  so  sensitive  to  dilute  acids 
and  is  much  faster  towards  light. 

A  still  greater  difference  between  the  benzidine  and  the  tolidine  dye-wares  appears 
in  conjunction  with  /3-naphthylaminesulpho  acids,  whether  they  are  obtained  by  directly 
sulphurising  /3-naphthylamine  or  by  heating  Schaffer's  /3-naphtholsulpho  acid  with 
ammonia.  In  both  cases  tetrazodiphenyl  forms  with  them  colouring  matters,  which 
are  insoluble  even  in  boiling  water,  and  in  this  state  cannot  be  fixed  upon  cotton,  being 
therefore  technically  worthless.  On  the  other  hand,  tetrazoditolyl  forms  in  conjunc- 
tion with  these  sulpho  acids  dyes  soluble  in  water,  which  are  very  valuable  from  their 


576  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

fastness  against  strong  acetic  acid,  and  even  against  dilute  mineral  acids,  as  well  as  by 
their  brilliance. 

For  the  production  of  these  dye-stuffs,  aqueous  solutions  of  the  tetraditolyl  salts 
are  run  into  the  mono-  and  disulpho-acicls  of  a-  and  /3-naphthylamine,  finely  divided 
in  water,  and  the  free  mineral  acids  present  are  neutralised  by  salts  of  the  organic 
acids,  e.g.,  sodium  acetate.  The  spirit-dyes  thus  formed  are  converted  into  water- 
dyes  by  treatment  with  fuming  sulphuric  acid,  and  have  now  a  great  resemblance  to 
the  dyes  at  once  obtained  in  a  form  soluble  in  water.  For  instance,  150  kilos, 
of  toluidine  sulphate  (diamidoditolyl)  obtained  from  technical  nitrotoluol  are  finely 
divided  in  water,  mixed  with  50  kilos,  of  hydrochloric  acid  at  32°  Tw.  and  22*2 
kilos,  sodium  nitrite,  dissolved  in  10  litres  of  water,  are  slowly  run  into  the 
solution,  which  is  cooled  with  ice.  In  this  manner  is  formed  tetrazoditolyl  chloride. 
This  solution  is  then  added  to  an  aqueous  solution  of  58  kilos,  of  a-  and  j3-naphthyla- 
mine  hydrochlorate ;  the  free  mineral  acid  is  neutralised  with  sodium  acetate,  and  the 
mixture  is  allowed  to  stand  for  24  hours.  The  dark  brown — or  bright  red — precipitate 
is  filtered  off  and  dried,  previous  to  its  conversion  into  its  sulpho  acids.  Further,  50  kilos, 
of  the  dry  dye- ware,  soluble  in  spirit,  are  gradually  added,  at  15°,  to  150  kilos,  or 
fuming  sulphuric  acid  containing  20  per  cent,  anhydride,  with  constant  stirring,  and 
the  deep  blue  melt  obtained  is  allowed  to  stand  at  common  temperatures  until  the 
sulphurising  is  complete.  It  is  then  poured  into  water,  and  the  sulpho  acid  formed 
is  converted  into  its  soda-salt. 

According  to  another  procedure,  the  tetrazoditolyl  chloride  is  added  to  73  kilos.  01 
naphthionic  acid,  i.e.,  sparingly  soluble  a-naphthylaminesulpho  acid ;  the  free  mineral 
acid  is  saturated  by  the  addition  of  sodium  acetate,  and  the  mixture  is  allowed  to  stand 
for  several  days  with  frequent  stirring.  There  is  formed  a  reddish-brown  slimy  precipi- 
tate, which  is  converted  into  its  soda-salt  by  heating  and  neutralising  with  soda.  On 
cooling,  the  dye-stuff  is  deposited,  almost  quantitatively,  as  an  orange-red  powder,  which 
dyes  unmordanted  cottons  a  deep  bluish-red. 

A  scarlet  dye-ware,  fast  against  acids  and  more  beautiful  than  the  colours  above- 
named,  is  obtained  from  /3-naphthylaminesulpho  acid,  formed  by  heating  Schaffer's 
/3-naphtholsulpho  acid  with  ammonia.  After  an  excess  of  soda  has  been  added  to  the 
aqueous  solution  of  80  kilos,  of  sodium  /3-naphthylaminesulphate,  tetrazoditolylchloride 
is  run  into  it  slowly,  stirring  the  mixture  and  keeping  it  cool  with  ice.  There  is 
formed  a  brownish-red  precipitate,  which  redissolves  completely  after  standing  for 
twelve  hours.  If  brine  is  added  to  this  solution,  a  red  slimy  precipitate  is  obtained, 
which  becomes  crystalline  on  heating,  and  is  the  sodium  salt  of  the  above-named  dye- 
ware. 

Sodium  paranitrotolulsulphate  in  a  watery  solution,  if  heated  with  soda-lye,  be- 
comes, according  to  Leonhardt,  a  condensation  product,  soluble  in  water.  It  can  be 
used  as  a  yellow  on  woollens,  and  by  reduction  it  is  converted  into  an  amidosulpho 
acid ;  50  kilos,  of  sodium  paranitrotoluolsulpho  salt  are  dissolved  in  700  litres  of 
water  and  digested  with  30  kilos,  of  soda-lye  at  72°  Tw.  The  colour  of  the  liquid 
passes  to  an  intense  yellowish,  red.  The  condensation  product  formed  can  be  precipi- 
tated by  the  addition  of  brine. 

Either  the  boiling  liquid  is  mixed  with  zinc  powder  until  it  is  colourless,  filtered  whilst 
hot,  and  the  new  acid  is  precipitated  with  hydrochloric  acid,  or  it  is  strongly  acidified  and 
reduced  with  tin  or  stannous  chloride  until  a  specimen  of  the  liquid,  after  being  ren- 
dered alkaline,  shows  but  a  faint  colour.  In  either  case  the  acid  liberated  is  purified 
by  dissolving  in  soda  and  precipitation  with  acid,  and  forms  then  a  yellowish-white 
powder,  quite  insoluble  in  water.  The  barium  salt  may  be  obtained  in  shining  nacreous 
leaflets  by  precipitating  the  concentrated  aqueous  solution  with  common  salt. 

The  new  amidosulpho  acid  is  characterised  by  the  fact  that  its  sparingly  soluble 


SECT,  iv.]  AZO   COLOURING   MATTERS.  57  7 

diazo-derivative,  in  combination  with  aromatic  amines  and  phenoles  or  their  sulpha 
salts,  forms  with  the  carbon  acids  yellow,  red,  brown,  and  blue  dye-stuffs,  which  give 
fast  colours  on  vegetable  fibres  without  a  mordant.  Red  and  brown-red  colours  are 
thus  obtained  with  resorcine,  resorcylic  acid,  orcine,  methylaniline,  dimethylaniline, 
diphenylamine,  phenylendiamine,  /3-naphthylamine,  and  its  sulpho  acids,  a-naphthyl- 
aminesulpho  acid. 

20  kilos,  of  the  sodium  salt  of  the  new  acid  are  dissolved  in  soda  and  diazotised  with 
7  kilos,  nitrite  and  25  kilos,  hydrochloric  acid.  The  liquid  thus  obtained  is  added 
to  a  solution  of  15  kilos.  /3-naphthylamine  in  12  kilos,  hydrochloric  acid  and  500  litres 
water.  The  free  colouring  acid  separates  out  ;  it  is  filtered,  washed,  and  converted 
into  its  sodium  salt. 

Or  we  diazotise  20  kilos,  of  the  sodium  salt  of  the  amidosulpho  acid  into  the  above 
manner,  and  pour  the  solution  of  the  diazo  compound  to  a  solution  of  28  kilos,  of  the 
sodium  salt  of  the  /3-naphthylaniinesulpho  acid  (obtained  from  /3-naphthol-/3-sulpho 
acid),  to  which  the  necessary  quantity  of  sodium  acetate  has  been  added  to  saturate  the 
free  mineral  acid.  The  free  colouring  acid  is  salted  out,  washed,  and  converted  into  its 
sodium  salt. 

Or  we  diazotise  20  kilos,  of  the  acid  as  above,  and  pour  the  solution  into  a  solution 
of  19  kilos,  diphenylamine  in  30  litres  of  spirit.  After  standing  for  a  time,  the  free 
colouring  acid  separates  out  in  an  insoluble  state.  It  is  filtered,  washed,  and  converted 
into  its  soluble  sodium  salt. 

The  following  dyes  are  obtained  with  i  mol.  diamidostilbenedisulpho  acid  :  —  With 
2  mols.  phenol,  brilliant  yellow  ;  with  2  mols.  /3-naphthylamine,  Hessian  purple  N  ;  with 
2  mols.  naphthionic  acid,  Hessian  purple  P  ;  with  2  mols.  /3-naphthylaminemonosulpho 
acid,  Hessian  purple  D;  with  2  mols.  salicylic  acid,  Hessian  yellow;  with  i  mol. 
a-naphthylamine  and  i  mol.  /3-naphthol,  Hessian  violet.  By  ethylating  brilliant  yellow 
there  is  formed  Chrysophanine  : 


Brilliant  yellow.  Hessian  purple  N. 


fCHCeH 


6    3(KN.C6H4.OC2H5 
N.N.C6H4.00SH5 


KN.CJI 


(OH 


MCOONa 
rCOONa 


N  N  0  H 

3  1  OH 


3 


Chrysophenine.  Hessian  yellow. 

For  the  production  of  Croceine  scarlet  50  kilos,  of  amidoazobenzolmonosulpho  acid 
are  diazotised  with  hydrochloric  acid  and  sodium  nitrite.  The  diazobenzolsulphuric 
acid  is  introduced  into  a  solution  of  75  kilos.  /3-naphthol-a-sulpho  acid  in  500  litres 
water  and  140  kilos,  of  10  per  cent,  ammonia  : 


,SOPNH4  fONa 

H 


If  instead  of  the  sulpho  acid  free  amidoazobenzol  is  used,  the  colouring  matter  has  a 
yellower  tone.  The  homologues  of  amidoazobenzol  yield  bluish  red  dyes,  diazobenzol 
and  its  homologues  reddish  yellow  ones,  a-diazonaphthaline  a  blue-red  dye  and  /3- 
diazonaphthaline  a  brick-red  colouring  matter. 

Biebrich  scarlet  is  formed  by  the  action  of  diazoazobenzol  upon  /3-naphthol  ;  the 
commercial  product  consists  of  the  sodium  salts  of  the  mono-  and  di-sulpho  acid. 

2  o 


578  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

From  a-naphthylamine  and  naphthol  or  the  naphtholsulpho  acids  there   are  ob- 
tained :  — 

Soudan  brown,  C10H7[a]N.N.Cl0H6[a]OH 

Buffalo  rubine, 

New  coccine  E,  Cl0H7[a]N.y.Cl0H4    g     . 


scarlet  S.. 
1 


Fast  red  B,  Bordeaux  B,  C10H7[a]KN.C10H4 

Carmine  naphtha,  010H7[/3]N.N.C10H6[/3]OH 

_  /S03Na 
Orange  I.,  tropseolme  ooo  Nt.  i,  C6H4  j-^-  jq-  @  JT  r  -JQTT  is  obtained  from  sulphanilic 

and  acid  a-naphthol,  the  similarly  composed  Orange  II.,  tropceoline  ooo  No.  2,  chrys- 
aurine,  gold  orange  from  sulphanilic  acid,  and  /3-naphthol.  Orange  III.,  methyl  orange, 

tropceoline  D,  helianthine,   C6H4|_...  A.  ~          .        .  ,  is  obtained  from  sulphanilic  acid 

and  dimethylaniline. 

Double  brilliant  scarlet  G  is  obtained  from  the  diazo  compound  of  yS-naphthyl- 
amine-monosulpho  acid  and  ^-naphthol;  it  dyes  wool  a  yellowish  red  in  an  acid 
flot,  If  instead  of  /3-naphthol  there  is  used  a-naphtholmonosulpho  acid  we  obtain  double 

..G..H.R\ra-,^-r  -^  n   TT     ffalOH  i  •  i    j  t  -i  i.  '  -j  i_     i 

1    10    6  1  [P\N  .N.C10H6  \  [  -Ln  „    ,  which  dyes  wool  a  scarlet  in  an  acid  beck. 

i  I  ct  lOvJoJN  £l« 

1_    J  o  -* 

Woollen  black,    C6H.  j  AT  •    *  „  fS03Na         CH  )  . 

1  i]N.N.C6H3  J  >r  xr  rj  TJ  XTJT  |  C6H4,  a  blue-black  azo-dye  is  ob- 

tained by  combining  paratolyl-/3-naphthylamine  with  the  diazo  compound  of  azobenozol- 
disulpho  acid.  The  paratolyl-j8-naphthylamine  is  dissolved  in  20  parts  of  alcohol  and 
mixed  with  an  equivalent  quantity  of  hydrochloric  acid  at  31°  Tw.  An  equivalent 
amount  of  diazoazobenzoldisulpho  acid  is  introduced,  when  the  free  acid  of  the  dye- 
stuff  is  formed.  The  latter  is  salted  out  with  sodium  chloride,  filtered,  and  washed 
until  the  washings  run  off  colourless.  The  residue  is  then  taken  up  in  soda-lye,  the 
solution  is  filtered,  and  the  colouring  matter  is  salted  out,  when  it  separates  in  fine 
crystalline  leaflets.  It  is  filtered,  pressed,  and  dried.  In  an  acid  beck  it  dyes  woollens 
a  blue-black. 

Congo,  I  C6H4.N.N.C10H5  jgQ-5,-   L  is  one  of  the  numerous  benzidineazo  dyes.     It 

is  prepared  from  benzidine  and  naphthionic  acid,  and  is  by  no  means  permanent. 

(NHa 
(C6H4.N.KC6H3     {so^a 

Congo  G  It,  j  r  -,~~  ,,    is  a  red  colouring  matter  obtained  from 

lC6H4.N.N,3C10H6    H£ 


benzidine,  amidobenzolsulpho  acid,  and  naphthionsulphuric  acid. 

For  the  preparation  of  mixed  azo-dyes,  which  take  upon  unmordanted  vegetable 
fibre  at  once  in  a  soap  beck,  the  German  patent  40,954  gives  thirty  prescriptions,  of 
which  the  following  are  specimens  : — 

i.  In  order  to  convert  benzidine  into  the  chloride  of  the  tetrazo  compound  18-4 
kilos,  of  benzidine  are  dissolved  in  600  litres  water  which  contain  55  kilos,  hydrochloric 
acid  at  32°  and  diazotised  with  14  kilos,  of  sodium  nitrite.  The  solution  of  the  tetrazo 
compound,  made  up  to  1000  litres,  is  run,  with  thorough  agitation,  into  a  solution 
of  20  kilos,  of  sodium  meta-amidobenzol  sulphate  and  40  kilos,  sodium  acetate  made  up 


SECT,  iv.]  ORGANIC  COLOURING  MATTERS.  579 

to  500  litres.  After  acting  for  one  hour  the  formation  of  the  intermediate  pro- 
duct (an  orange-yellow  insoluble  precipitate)  is  completed.  It  is  then  introduced 
into  a  solution  of  35  kilos,  sodium  a-naphthylamine  sulphate  and  20  kilos,  soda  in 
500  litres  water.  After  thorough  stirring  it  is  let  stand  for  some  time,  boiled  up, 
filtered,  and  salted  out,  yielding  a  product  which  dyes  cotton  a  yellowish  red  in  a  soap 
beck. 

2.  If  the  intermediate  product  obtained  as  according  to  i    (from  tetrazodiphenyl 
and  meta-amidobenzolsulphuric  acid)  is  mixed,  instead  of  with  the  quantity  of  naphthi- 
onic  salt  above  given,  with  a  solution  of  26  kilos,  of  sodium  a-naphthol  monosulphate,  a 
colouring  matter  is  obtained  which  dyes  cotton  a  reddish  violet. 

3.  If,  instead  of  the  naphthionic  salt  in  i,  there  are  used  37  kilos,  sodium  ^-naphthol 
disulphate  (R  salt),  there  is  obtained  a  product  which  dyes  cotton  a  violet-red  in  an 
alkaline  soap  beck. 

4.  The   combination   of  tetrazodiphenyl  with  para-amidobenzolsulphuric  acid  is 
effected  similarly  to  that  with  the   isomeric   meta-amidobenzolsulpho   acid.     In   the 
preparation  of  the  intermediate  product  from  the  /3-acid  there  is  used  the  same  quantity 
of  benzidine,  hydrochloric  acid,  and  sodium  nitrite  for  producing  tetrazophenyl,  and  the 
latter  is  made  to  act  upon  a  solution  of  30  kilos,  sodium  para-amidobenzol  sulphate 
(sulphanilate).     The  intermediate  product  is  redder  than  that  from  the  isomeric  meta- 
amidobenzolsulpho  acid.      For  obtaining  the  dye  the  intermediate  product  is  made  to 
act  upon  a  solution  of  35  kilos,  sodium  /3-naphthylamine  sulphate  in  20  kilos,  soda  and 
500  litres  water.     The  product  dyes  a  brownish  orange. 

5.  If  the  intermediate  product  obtained  with  the  proportionate  quantities  given  in 
4  is  allowed  to  react  on  a  solution  of  14  kilos,  phenol  in  14  grammes    soda-lye  at 
72°  Tw.  and  20  kilos,  of  sodium  carbonate,  there  is  formed  a  yellow  dye. 

6.  A  yellow  dye  is  also  obtained  if  the  phenol  given  in  5  is  replaced  by  1 5  kilos, 
salicylic  acid. 

Other   Organic    Colouring   Matters. — Gallic  acid  is    used    for   obtaining   various 
colouring  matters,  such  as  gallocyanine,  galleine,  ceruleine,  and  galloflavine. 
fO.B,.OH.O 

TT  OH  O>  *s  ^orme(^  by  the  action  of  phthalic  anhydride 

lcX-c°-0 

upon  pyrogallol  in  the  same  manner  as  phthalic  anhydride  combines  with  resorcine 
to  form  fluoresceine. 

For  its  preparation  Baeyer  heats  one  part  phthalic  anhydride  with  two  parts  of 
pyrogallol  to  190°  to  200°  for  some  hours,  until  the  melt  becomes  thick.  The  cold 
melt  is  dissolved  in  alcohol,  precipitated  with  water,  and  the  separated  galleine  is  purified 
Toy  repeated  solution  and  precipitation.  In  practice  he  does  not  set  out  with  pyro- 
gallol, but  heats  a  mixture  of  gallic  acid  and  phthalic  anhydride  to  190°  to  200°.  At 
this  temperature  gallic  acid  is  resolved  into  pyrogallol  and  carbonic  acid ;  the  latter 
escapes  and  the  former  combines  with  phthalic  anhydride  to  form  galleine.  The 
-colouring  matter  is  also  known  as  alizarine  violet  or  anthracene  violet. 

Ceruleine,  C20Hg06,  is  obtained  by  dissolving  galleine  in  concentrated  sulphuric 
acid  and  heating  to  190°  to  200°.  Galleine  loses  i  molecule  water  and  yields  the  dye  in 
question,  which  is  also  known  as  alizarine  green  and  anthracene  green. 

Ceruleine  is  closely  connected  with  phenylanthracene,  and  passes  into  this  hydro- 
carbon if  distilled  over  zinc  powder.  Ceruleine  forms  when  dry  a  bluish-black 
shining  mass.  It  dissolves  with  difficulty  in  the  ordinary  solvents  with  a  dirty 
green  colour,  but  with  a  fine  green  colour  in  the  alkalies.  With  the  alkaline 
bisulphites  ceruleine  forms  double  compounds  soluble  in  water. 


580  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

Of  these  two  colours  ceruleine  is  by  far  the  more  important.  The  brownish-red 
shades  of  galleine  can  be  obtained  quite  as  easily,  though  finer  and  faster,  with  alizarine, 
but  the  rich  olive  tones  of  ceruleine  have  become  quite  indispensable  to  the  tissue- 
printer  from  their  fastness  against  light  and  soap,  as  well  as  by  the  ease  and 
certainty  of  their  application.  Both  galleine  and  ceruleine,  like  gallocyanine,  are  most 
readily  fixed  by  means  of  the  salts  of  chrome.  The  soluble  bisulphite  compound  of 
ceruleine  is  less  frequently  used  than  the  paste,  to  which  bisulphite  is  added,  thus 
producing  the  soluble  double  compound  in  the  printing  colour  itself. 

Gattqflavim,  C13H609,  is  formed  by  the  oxidation  of  gallic  acid  in  an  alkaline  solution 
by  means  of  atmospheric  air. 

The  Baden  Aniline  Company  dissolve  5  parts  gallic  acid  in  80  parts  alcohol  at 
96°  Tralles  and  100  parts  of  water.  The  solution  after  cooling  down  to  5°  to  10°  is 
slowly  mixed  with  17  parts  of  potassa-lye  at  49°  Tw.,  stirring  thoroughly,  and  is 
exposed  to  the  action  of  the  atmosphere  at  a  temperature  not  exceeding  10°.  For 
this  purpose  either  a  strong  current  of  air  is  passed  through  the  alkaline  solution, 
or  it  is  exposed  to  the  air  in  thin  layers,  a  constant  renewal  of  the  surface  being  effected 
by  means  of  suitable  apparatus.  The  progress  of  the  oxidation  is  recognised  by  the 
increasing  olive  or  greenish-brown  colour  and  by  the  deposition  of  a  crystalline  precipi- 
tate, the  potassium  salt  of  the  new  tinctorial  acid.  To  watch  the  operation  there  is 
taken  a  sample  from  time  to  time ;  it  is  filtered  and  the  filtrate  is  shaken  with 
air,  observing  if  after  a  time  there  appears  a  precipitate  of  the  potassium  salt  insoluble 
in  dilute  hydrochloric  acid.  If  no  further  separation  of  crystals  takes  place  the 
process  is  interrupted  to  prevent  a  further  oxidation  and  destruction  of  the  colouring 
matter  which  has  been  formed.  The  crystalline  paste  is  quickly  filtered,  pressed,  and 
dissolved  in  warm  water.  The  solution  is  slightly  supersaturated  at  about  50°  with 
hydrochloric  or  sulphuric  acid  and  boiled  until  the  colouring  matter  separates  out 
in  a  heap  of  shining  light  yellowish-green  crystals,  which  are  separated  from  the 
reddish-brown  solution  by  filtration.  After  washing  with  water  at  a  hand-heat  the 
product  is  ready  for  dyeing  or  printing. 

Styrogallol. — Cinnamic  and  gallic  acids  unite  in  presence  of  a  dehydrating  agent 
according  to  the  equation  : 

C6H6.CH :  CH.COOH  +  06H,(OH)8COOH  =  C16H10O5  +  2H,O. 

Under  the  same  conditions  tannin  (digallic  acid)  forms  the  same  condensation 
product. 

10  parts  (i  molecule)  cinnamic  acid  and  17  parts  of  gallic  acid  are  heated  for 
two  or  three  hours  to  55°  with  150  parts  of  concentrated  sulphuric  acid.  The  melt 
is  poured  into  an  excess  of  cold  water,  when  styrogallol  separates  as  a  pale  green 
powder,  consisting  of  microscopical  needles.  Like  nitroalizarine,  it  gives  with  mordants 
tones  ranging  from  yellow  to  blackish.  The  colours  bear  soaping.  Styrogallol  can 
be  converted  into  a  soluble  sulpho  acid  by  treatment  with  fuming  sulphuric  acid.  In 
this  state  it  dyes  wool  a  light  yellow. 

Tartrazine. — The  sodium  salt  of  disulphodiphenylhydrazindioxytartaric  acid  is 
obtained  by  the  action  of  phenylhydrazinmonosulpho  acid  from  diazoamidobenzol 
upon  dioxitartaric  acid. 

Ten  parts  of  sodium  dioxytartrate  are  diffused  in  30  parts  of  water  and  mixed 
with  35  parts  hydrochloric  acid  at  30°  Tw.  To  the  clear  solution  thus  obtained  there 
is  added  a  solution  of  12 '8  parts  phenylhydrazin  hydrochlorate  in  100  parts  of  water 
and  gently  heated.  A  yellow  voluminous  precipitate  is  formed,  and  after  standing 
twelve  hours  it  is  collected  on  a  filter  and  dried.  The  light  yellow  colouring  matter 
when  cold  is  filtered,  pressed,  and  dried ;  it  is  readily  soluble  in  water,  insoluble  in 
alcohol,  and  gives  a  pure  yellow,  fast  to  light  on  animal  fibres. 


SECT.   IV.] 


ORGANIC  COLOURING  MATTERS. 


In  a  corresponding  manner  isatine  yellow  is  obtained  by  the  action  of  phenylhydra- 
zinparasulpho  acid. 

Canarine  (persulphocyanogen),  C6N402H4S5,  is.form.ed  from  potassium  sulphocyanide 
by  oxidation. 

Three  kilos,  of  sulphocyanide  are  dissolved  in  6  litres  of  hot  water  in  an  earthen 
vessel;  300  grammes  potassium  chlorate  are  added  and  2^4  kilos,  hydrochloric  acid 
are  stirred  in.  The  mixture  is  gently  heated,  if  necessary,  until  the  reaction  which  sets 
in  after  a  few  minutes  has  almost  entirely  subsided.  The  vessel  is  then  set  in  cold 
water,  and  rz  kilo,  potassium  chlorate  and  3-6  kilos,  hydrochloric  acid  are  gradually 
added  in  small  lots.  The  temperature  of  the  mixture  must  be  kept  at  about  80°.  The 
orange -coloured  precipitate  formed  is  washed  by  decantation  three  times  with  hot  water, 
collected  011  a  linen  strainer,  washed  until  neutral,  and  dried. 

For  purification  this  crude  product  is  heated  to  solution  with  an  equal  weight  of 
potassium  hydrate  and  20  parts  of  distilled  water  until  dissolved.  The  dark-red  solution 
is  filtered  through  wool,  and  when  it  is  cooled  down  to  40°  it  is  mixed  with  20  parts 
ethyl  alcohol  at  90  per  cent.,  and  the  whole  is  set  aside  for  twenty-four  hours.  The 
reddish- orange,  granular  crystalline  precipitate  of  the  potash  compound  of  the  colouring 
matter  is  filtered,  pressed,  and  dried ;  the  filtrate,  after  the  alcohol  has  been  distilled 
off,  is  melted  down  for  potassium  ferrocyanide.  In  order  to  separate  the  colouring 
matter  from  the  potassium  compound  it  is  dissolved  in  10  parts  of  water  and  the  solu- 
tion is  mixed  with  hydrochloric  acid  enough  to  precipitate  the  colouring  matter ;  the 
brown  precipitate  formed  is  washed,  filtered,  and  dried. 

The  aqueous  solutions  of  canarine-alkaline  salts  dye  cotton,  without  mordants,  shades 
of  maize,  yellow,  and  orange.  The  colours  bear  soaping  and  light.  For  making  up 
the  dye  beck,  one  part  canarine,  one  part  potassium  hydrate,  and  400  parts  water  are 
heated  to  boiling,  and  one  part  curd  soap  is  added,  or  two  parts  canarine  potassium  are 
dissolved  in  400  parts  water  and  the  part  of  soap  is  added. 

Goppelsroeder  obtains  persulphocyanogen  by  the  electrolysis  of  an  aqueous  solution 
of  potassium  sulphocyanide  as  an  orange-yellow  deposit  at  the  positive  pole.  He  has 
also  formed  and  fixed  canarine  simultaneously  by  electrolysis  upon  vegetable  and  animal 
fibres. 

Murexide,  C8H4(NH4)N506,  has  been  already  mentioned. 

Lampblack  (soot)  is  obtained  by  the  imperfect  combustion  of  resin,  gas-tar,  oils,  &c. 
The  furnaces  consist  of  one  or  two  slightly  ascending  combustion  shafts,  A  (Fig.  400 
.and  401),  in  which  the  solids  to  be  burnt  are  thrown  in  in  front,  whilst  tar  and  oils  are 


Fig.  400. 


.  401. 


Explanation  of  Term. 
Schnitt  x-y        .         .        Section  x-y. 


passed  in  through  iron  pipes  from  the  vessels,  a.  The  smoke  fumes  pass  from  there 
into  the  first  massive  cooling  chamber,  £,  through  b  into  the  long  chamber,  C,  extend- 
ing above  it,  then  into  the  tower,  Z>,  divided  by  a  partition  into  two  perpendicular 


582  CHEMICAL  TECHNOLOGY.  [SECT.  iv. 

compartments,  and  finally  through  a  regulating  chimney  into  the  air  outside.  A  coarse 
cloth,  stretched  across  the  half  of  the  tower,  serves  to  keep  back  the  hist  residues  of 
soot. 

The  materials  are  ignited  every  Tuesday  morning,  and  the  combustion  is  kept  up 
until  Saturday  evening,  with  cessations  only  from  9  or  TO  P.M.  to  4  or  5  A.M.  On 
Sunday  the  furnaces  cool,  and  on  Monday  they  are  emptied.  From  100  parts  of  tar 
the  yield  of  lampblack  is  25  parts,  and  from  100  parts  of  dregs  of  resin  20  parts. 

Finer  blacks  are  obtained  by  burning  mineral  oils  in  lamps ;  the  flame  strikes  upon 
cold  surfaces,  on  which  the  liberated  carbon  is  deposited  as  lampblack. 

Lampblack  is  used  in  the  production  of  printing-inks,  Indian  inks,  and  as  an  admix- 
ture to  some  painters'  colours.* 

EXAMINATION  OF  COLOURING  MATTERS.! 

The  first  point  to  be  ascertained  is  whether  a  sample — be  it  a  dry  powder,  a  paste,  or  a 
liquid — is  a  unitary,  homogeneous  substance  or  a  mixture.  To  this  end,  Slater f  places  a 
drop  of  the  solution  upon  a  piece  of  filter-paper.  . 

If  the  colour  is  homogeneous,  the  spot  produced  will  be  alike  throughout.  If  the 
colour  is  a  mixture  there  are  seen  rings  of  different  colours. 

Goppelsroeder§  about  the  same  time  applied  the  same  principle  in  a  manner  which 
is  often  more  convenient.  He  suspends  slips  of  filter-paper  so  as  to  dip  into  the 
solution  of  the  dye-stuff.  If  we  have  to  do  with  a  mixture,  the  different  colours  will 
ascend  to  different  heights  on  the  slip,  forming  a  succession  of  bands. 

If  time  is  not  a  pressing  object,  a  portion  of  the  colour  may  be  dissolved,  and 
swatches  of  woollen  and  silken  tissues  may  be  dyed  successively  until  the  bath  is  ex- 
hausted, noting  the  order  of  the  swatches.  If  the  colour  is  homogeneous,  the  first  and 
the  last  swatch  will  display  exactly  the  same  tone,  but,  if  it  is  a  mixture,  a  difference 
will  be  observed,  some  one  of  the  ingredients  combining  more  readily  with  the  fibre 
than  the  others. 

In  the  case  of  the  azo  dyes,  we  may  utilise  their  property  of  dissolving  in 
sulphuric  acid  with  different  colours.  Pure,  clean,  concentrated  sulphuric  acid  is 
placed  in  a  white  porcelain  capsule  •  a  few  fine  granules  of  the  dye  are  sprinkled  upon 
the  acid,  and  the  tones  of  colour  which  they  produce  are  observed.  Mixtures  may 
thus  often  be  detected,  especially  as  the  reaction  is  very  sensitive. 

Besides  the  joint  presence  of  different  colours,  mineral  impurities  are  often  found, 
such  as  potassium  and  sodium  carbonates,  common  salt,  sodium  and  magnesium  sulphates, 
and  dextrine.  These  substances  are  not  always  due  to  intentional  fraud,  but  are  re- 
sidues of  matters  used  in  the  process  of  manufacture  and  not  fully  removed.  Common 
salt  is  found  in  almost  every  soluble  colouring  matter  which  is  not  capable  of  crystalli- 
sation. A  small  part  of  the  dye  is  ignited  and  chlorine  is  tested  for.  Sodium  sulphate 
is  chiefly  found  in  the  azo  dyes.  The  dye  is  dissolved  in  water,  salted  out  with  chemi- 
cally pure  sodium  chloride,  and  sulphuric  acid  is  sought  for  in  the  filtrate  in  the  ordinary 
manner.  Magnesium  sulphate  is  rarely  used  in  place  of  Glauber's  salt.  Alkaline  car- 
bonates may  be  used  in  case  of  the  phthaleines.  Dextrine  is  recognised  by  the  smell 
which  it  gives  off  on  dissolving  the  dye  in  water,  and  which  resembles  that  of  bugs.  Or 
the  colouring  matter  may  be  extracted  with  concentrated  alcohol,  which  leaves  dextrine- 
undissolved. 

*  On  the  coal-tar  colours  the  reader  may  compare  The  Chemistry  of  the  Coal-tar  Colours,  by 
Benedikt  and  Knecht.  London  :  G.  Bell  &  Sons. 

t  Section  added  by  the  Editor.  J  Manual  of  Colours  and  Dye-wares. 

§   Capittar  Analyse  und  Hire  Amcendungen  :  Mulhouse,  Wenz  &  Peters. 


SECT,  iv.]  EXAMINATION  OF  COLOURING  MATTERS.  583 

In  carrying  out  the  systematic  examination  of  colouring  matters,  we  mix  a  mode- 
rately concentrated  solution  of  the  dye  with  solution  of  tannin  (25  parts  tannin,  25 
sodium  acetate,  and  250  water).  An  excess  of  tannin  is  to  be  avoided  (since  the 
precipitate  is  often  soluble  in  excess),  and  the  liquid  is  then  heated,  as  certain  sul- 
phonised  derivatives  of  triphenylmethane  form  precipitates  which  redissolve  at  higher 
temperatures.  In  the  presence  of  a  basic  colouring  matter  the  filtrate  should  be  nearly 
colourless  after  the  addition  of  the  solution  of  tannin. 

We  reduce  the  basic  dye-wares  with  zinc-powder  and  hydrochloric  acid ;  after  filtra- 
tion, we  saturate  with  sodium  acetate,  since  an  excess  of  hydrochloric  acid  may  form 
acid  salts  from  the  basic  colours  after  re-oxidation,  having  different  colours  from  those 
of  the  neutral  salts.  In  reducing  Bismarck  brown  and  chrysoidine,  there  are  formed 
di-  and  tri-amines,  which  are  easily  oxidised  in  contact  with  the  air,  and  take  a  brownish- 
red  colour.  It  is  therefore  necessary,  especially  in  the  case  of  the  brown  and  the 
yellow  basic  colours,  to  compare  the  colour  of  the  reduced  and  the  re-oxidised  dye-stuff 
with  that  of  the  original  solution.  After  the  reduced  solution  has  been  dropped  upon 
filter-paper,  it  is  advantageous  to  assist  the  oxidation  by  heating  it  slightly  over  a 
flame.  Certain  dye-stuffs  become  oxidised  with  such  rapidity  that  the  original  colour 
reappears  during  filtration. 

Acid  Colouring  Matters. — The  reduction  of  the  non-fluorescent  yellow,  orange,  pon- 
ceau, and  claret  dye-wares  must  be  effected  with  great  caution.  It  is  best  to  reduce  with 
zinc  powder  and  hydrochloric  acid  and  neutralise  with  sodium  acetate,  since  the  nitro 
groups  which  may  be  present  in  the  sample  would  not  be  reduced  quickly  enough  if 
ammonia  or  acetic  acid  were  used.  It  is  prudent  to  compare  the  reduced  and  re- 
oxidised  solution  with  the  original  solution  of  the  colouring  matter,  since  in  the  reduc- 
tion of  the  nitro  or  azo  colours  there  are  formed  diamines  or  amido  phenoles,  which 
on  oxidation  produce  dirty-yellow  or  brown  tones.  To  this  section  (azo  dye- wares) 
belongs  likewise  erythrosine,  for  in  its  reduction  iodine  is  liberated  with  re-formation 
of  fluoresceine.  All  colours  not  mentioned  may  be  reduced  with  zinc  powder  and  acetic 
acid  or  ammonia.  In  the  reduction  of  the  acid  dyes  the  solution,  as  soon  as  the  zinc 
powder  has  been  added  to  it,  should  be  rendered  colourless,  or  should  at  most  have 
merely  a  faint  yellowish  or  reddish  tint.  The  nitrofluoresceine  derivatives  and  the 
azo  dyes  may  be  easily  recognised  if  they  are  burnt.  There  are  formed  upon  the  sheet 
platinum  "  Pharaoh's  serpents,"  especially  on  working  with  a  large  quantity — say  0*5 
gramme.  In  order  to  detect  the  nitro  groups  in  the  light-yellow  colouring  matters  it  is 
necessary,  before  ignition,  to  mix  them  (e.g.,  picric  acid)  with  a  little  soda. 

It  is  very  difficult  to  reduce  "  alizarine  S "  completely ;  it  is  placed  in  the  last 
column  of  Table  B.,  under  the  heading  "  The  colour  of  the  ammoniacal  solution  re- 
appears." But  if  the  reduction  is  carried  too  far  the  original  colour  does  not  re- 
appear. 

All  the  sulphonised  amido-azo  and  tetrazo  colouring  matters  are  almost  decolorised 
if  they  are  reduced  with  zinc-powder  and  ammonia,  without  heat.  After  filtration 
the  solution  is  a  pale  yellow,  and  if  it  is  poured  upon  filter-paper  and  heated  it  causes 
yellow  spots.  The  azo  colours  produce  no  spots,  or,  at  most,  show  a  dirty  brown. 
The  reactions  with  barium  or  calcium  chloride  must  be  tried  with  a  concentrated 
solution  of  the  colouring  matters.  As  sodium  sulphate  is  contained  in  most  azo 
colours,  turbidity  cannot  be  reckoned  as  a  reaction.  The  sulphuric  acid  test  must  be 
carried  out  as  directed  above. 


584 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


Artificial  Colours  Soluble  in  Water. 
The  aqueous  solution  is  mixed  with  solution  of  tannin. 

A.  There  is  formed  a  Precipitate. 
Basic  Colouring  Matters. 

The  aqueous  solution  is  reduced  with  zinc-powder  and  hydrochloric  acid,  neutralised, 
and  placed  upon  filter-paper. 


The  original  colour  returns. 

Original  colour 
does  not 
return. 

Bed. 

Yellow  and 
Orange. 

Green. 

Blue. 

Violet. 

Magenta 

Toluylen  red 
(Cassella) 
Safranine 

Phosphine 
Flavaniline 

Malachite 
green 
Brilliant  green 

Methyl  green 

Methylene 
blue 
New  blue 
(Cassella) 
Muscarine 
(Durand  and 
Huguenin) 

Methyl  violet 

Hofmann's 
violet 
Mauveine 

Amethyst  blue 
Crystal  violet 

Chrysoidine 
Bismarck  brown 
Auramine 

Victoria  blue 

B.  No  Precipitate  is  formed. 
Acid  Colours. 

The  aqueous  solution  is  reduced  with  zinc-powder  and  hydrochloric  acid  (or  with 
zinc-powder  and  ammonia). 


Solution  decolorised. 

The  colour  changes  to 
a  brownish  red.     The 
ammoniacal  solution 
takes  its  original 
colour  on  the  filter. 

Original  colour 
reappears. 

Original  colour  does  not 
reappear. 

Aqueous  solution  acidi- 
fied with  HC1  and  treated 
with  ether. 

Colouring  matters  heated  on 
platinum  foil. 

Ether  dissolves  the 
colour  and  the 
aqueous  solution 
is  nearly  colourless. 

Ether  re- 
mains colour- 
less. 

Deflagrates 
without 
coloured 
fumes. 

Burns  slowly  with 
coloured  vapours,  or  de- 
flagrates slightly  with 
coloured  fumes. 

Alizarine  S. 
Alizarine  blue  S. 
Ceruleine  S. 

Phthaleines. 

Sulphonised 
derivatives  o1 
Rosaniline. 

Nitro  colours 
(Nitro- 
phenoles). 

Heat  an  unmordanted 
swatch  of  cotton  with 
aqueous  solution. 

Dye  bears 
hot  soap. 

Dye  does 
not  bear  hot 
soap. 

Benzidine 
azo  dyes. 

sAzo  dyes. 

SECT.    IV.] 


EXAMINATION  OF  COLOURING  MATTERS. 


5»5 


Solid  or  Pasty  Colours,  Insoluble  in  Water. 
The  dye-wares  are  treated  with  water  and  a  few  drops  of  soda-lye  at  5  per  cent. 


The  dye-wares  dissolve. 

The  dye  does  not  dissolve. 

The  alkaline  solution  is  filtered,  zinc- 
powder  is  added,  heated,  and  put 
on  filter-paper. 

The  colouring  matters  are  heated  with  alcohol 
at  70  per  cent,  and  dissolve,  except  indigo. 

Colour  of  alkaline 
solution  returns. 

Colour  does  not  re- 
turn in  the  same  tone, 
or  original  colour  is 
not  changed. 

Alcoholic  solution  not 
fluorescent. 

Alcoholic  solution 
fluorescent. 

Soda-lye  at  33  per  cent,  is  added. 

Ceruleine. 
Galleine. 
Gallocyanine. 
Galloflavine. 

Canarine. 
Alizarine. 
Anthrapurpurine. 
Flavopurpurine. 
Nitroalizarine. 
Alizarine  brown. 
Alizarine  blue. 
Chrysamine. 
Solid  green. 
(Dinitroresorcine.  ) 

Colour 
changes  to 
red-brown. 

No  change 
of  colour. 

Fluoresence 
disappears. 

Fluoresence 
does  not 
disappear. 

Induline. 
Nigrosine. 
Rosaniline 
blue. 
Diphenyl- 
amine  blue. 

Indophenol. 

Magdala 
red. 

Primrose 
Cyanosine. 

Basic  Colouring  Matters. 

Reds  :  Watery  solution  bluish  red  :  yellow-brown  with 
HC1  and  strong  sulphuric  acid.  Sodium  acetate  restores 
original  colour.  Zinc-dust  decolorises  watery  solution  ; 
colour  does  not  return.  Strong  sulphuric  acid  dissolves  it 
with  a  yellow-brown.  Solid  colour  green,  of  metallic  lustre  Magenta,  Rubine. 

Solution  reddish  blue;  ammonia  throws  down  flocks 
which  dissolve  in  ether  with  greenish-yellow  fluorescence. 
HC1  turns  it  blue ;  sulphuric  acid,  brownish  green ;  on 
addition  of  water,  colour  turns  blue,  violet,  and  lastly  red 

Alcohol  added  to  the  original  colour  gives  orange 
fluorescence.  Zinc-powder  decolorises  solution.  Colour 
returns  on  exposure  to  air.  Sulphuric  acid  makes  it  green  ; 
on  dilution  with  water,  passes  to  blue,  violet  and  red 

Yellows:  Easily  soluble  in  water.  With  alkalies,  a 
yellow  flocky  precipitate  (brown  if  impure)  ;  soluble  in  ether 
with  fine  yellow  colour  and  strong  green  fluorescence 

With  alkalies,  yellowish- white  milky  precipitate  ;  soluble 
in  ether  without  colour,  and  splendid  blue  fluorescence  . 

Greens  :  Easily  soluble  in  water  with  strong  green 
colour.  Alkalies  give  a  rose-coloured  or  grey  precipitate ; 
acids  turn  it  yellow.  Sulphuric  acid,  yellow ;  green  on 
dilution  with  H2O  .  .  .  .  .  .  .' 

Soluble  in  water  with  a  more  yellowish-green  colour  ; 
ammonia  gives  no  precipitate,  or  a  very  slight  one.  Solu- 
tion of  colour  in  sulphuric  acid  does  not  turn  green  as 
quickly  when  diluted  with  water  as  does  malachite  green  . 

Soluble  in  water  with  a  blue  or  greenjsh-blue  colour. 
With  acids,  yellow.  Alkalies  discharge,  but  give  no  preci- 
pitate ;  swatch  dyed  with  this  colour  turns  violet  at  100°. 
Sulphuric  acid,  yellow ;  on  dilution,  green 

Violets :  Easily  soluble  in  water.     Alkalies  give  a  violet 


Neutral  Red. 

Safranine. 

Phosphine  (ChrysaniUne). 

Flavaniline. 

Malachite  Green. 
Brilliant  Green. 
Methyl  Green. 


586 


CHEMICAL   TECHNOLOGY, 


[SECT.  iv. 


brown  solution  precipitate,  sulphuric  acid  a  yellow,  on 
dilution  with  water  violet  blue  ..... 

Sparingly  soluble  in  cold  water ;  HC1  turns  solution  blue ; 
alkalies  throw  down  brown  flocks  ;  sulphuric  acid  turns  it 
a  dirty  violet  .,  ...  ,  .  .  .  '•••.- 

Not  very  soluble  in  water ;  alkalies  give  a  violet  precipi- 
tate, sulphuric  acid  turns  colour  to  grey ;  on  slow  dilution 
with  water  turns  sky-blue,  violet- blue,  and  reddish  violet  . 

Soluble  in  water  with  red-violet  colour.  Carmine-red 
fluorescence  on  adding  alcohol.  Sulphuric  acid,  fine  green, 
on  dilution  becoming  blue  and  then  violet 

Soluble  in  water  with  very  pure  tone ;  HC1  turns  it 
orange  ;  soda-lye,  a  violet-brown  precipitate.  Strong  sul- 
phuric acid,  an  orange  colour,  which  does -not  disappear  on 
adding  10  parts  of  water.  Base  dissolves  in  ether  with  a 
yellow  colour  ........ 

Blues  :  Easily  soluble  in  water ;  HC1  gives  the  solution 
a  greenish  cast.  Strong  soda-lye,  a  violet-black  precipitate. 
The  colour  contains  zinc.  A  7  per  cent,  solution  of  chloride 
of  lime  destroys  the  colour  only  after  the  lapse  of  some 
hours.  Sulphuric  acid  gives  a  grass-green 

The  watery  solution  is  bluish  violet.  Strong  sulphuric 
acid  gives  a  green  colour  which  turns  blue  and  violet  on 
dilution.  Soda-lye  gives  a  black-brown  precipitate.  On  re- 
duction with  Zn  and  acetic  acid,  appears  first  a  green  colour. 
Colouring  matter  a  fine  powder  which  causes  sneezing 

There  has  latterly  been  sold  as  "  bleu  nouveau  "  a  dye 
the  solution  of  which  is  violet  when  hot  but  green  when 
cold.  Alkalies  give  a  red-brown  precipitate  ;  HC1  a  slight 
blue  precipitate.  Sulphuric  acid  gives  a  violet-red  colour, 
turning  violet  on  dilution ;  probably  a  mixture. 

Sparingly  soluble  in  cold  water,  with  a  violet  colour. 
Tannin  gives  an  indigo-blue  precipitate.  Sulphuric  acid 
dissolves  it  bluish  green,  blue  on  dilution  and  then  violet ; 
then  is  formed  a  precipitate,  soluble  in  much  water ;  soda- 
lye  gives  a  red-brown  precipitate  ..... 

Soluble,  with  a  yellow  colour.  Alkalies  give  a  white 
milky  precipitate.  Precipitate  soluble  in  ether  without 
fluorescence.  The  yellow  solution  of  the  dye  gradually 
loses  its  colour;  if  boiled  with  dilute  sulphuric  acid  it 
becomes  colourless.  A  transient  yellow  colour  on  reduc- 
tion with  zinc-powder  and  acetic  acid  .... 

Dyes  wool  orange-yellow  ;  watery  solution  of  the  dye 
congeals  (not  always)  to  a  blood-red  gelatinous  mass. 
Sulphuric  acid  dissolves  it  with  a  brown-yellow 

Dyes  wool  a  brown-orange ;  sulphuric  acid,  a  brown ; 
does  not  gelatinise  on  cooling  .  ..... 

Moderately  soiuble  in  water.  Yellow  brown  with  acids ; 
alkalies  give  a  brown-red  precipitate ;  zinc  and  acetic  acid 
decolorise  solution  permanently.  Sulphuric  acid  gives  a 
red-brown,  turning  green-blue  on  dilution 


Methyl  FioZei(Hofmann's). 
Neutral  Violet. 
Mauveine  (Rosolane). 
Amethyst  (Giroflee). 

Crystal  Violet. 
Methylene  Blue. 
New  Blue  B  and  D. 


Muscarine(Dur8iiid  &  Co.) 


Auramine. 


Chrysoidine. 

Vesuvine  (Bismarck 
brown). 


Victoria  Blue. 


SECT.   IV.] 


EXAMINATION  OF  COLOURING  MATTERS. 


Acid  Colouring  Matters.     Phthaleines. 

The  aqueous  solution  is  pure  red  with  a  yellowish-green 
fluorescence,  becoming  stronger  the  more  the  solution  is 
diluted.  Acids  throw  down  orange  flocks,  soluble  in 
ether  with  a  yellow  colour.  Strong  sulphuric  acid  dissolves 
it  with  a  yellow  colour ;  on  heating  the  solution,  white 
fumes  of  hydrobromic  acid  escape.  With  the  addition  of 
manganese  peroxide,  an  escape  of  bromine 

Watery  solution  more  bluish  than  that  of  eosine,  and 
but  slightly  fluorescent.  Acids  give  a  yellow-brown  pre- 
cipitation, which  dissolves  in  ether  with  a  yellow  colour. 
Dissolves  in  strong  sulphuric  acid  with  a  golden  yellow ;  on 
heating,  the  same  phenomena  as  with  eosine.  Ammoniacal 
solution  reduced  with  zinc-powder  quickly  recovers  its 
colour  in  the  air.  If  heated  on  platinum  foil,  brisk  com- 
bustion with  formation  of  "  Pharaoh's  serpents  "  . 

Watery  solution  bluish  red  with  slight  greenish 
fluorescence.  With  HC1,  a  flesh-coloured  precipitate  which 
dissolves  in  ether  with  a  brownish-yellow  colour.  Sulphuric 
acid  changes  the  colour  to  a  golden  yellow,  and  on  heating 
this  solution  hydrogen  bromide  escapes,  or  free  Br  on 
addition  of  MnO2  ....... 

The  watery  solution  is  dark  bluish  red,  not  fluorescent. 
HC1  gives  a  scarlet  precipitate,  soluble  in  ether  with  an 
orange-yellow  colour.  The  reduced  solution  is  but  little 
oxidised  in  the  air.  Dissolves  in  sulphuric  acid  with  an 
orange,  and,  on  heating,  iodine  deposits  on  the  sides  of  the 
vessel  .  .  .  .  .  .  .  .  . 

Solution  brownish  yellow  with  strong  green  fluorescence 
which  disappears  on  adding  HC1  with  formation  of  a  yellow 
precipitate  .  .  .  .  .  .  *  . 

Solution  eosine  red.  HC1  gives  a  yellow  precipitate. 
Strong  sulphuric  acid  gives  a  yellow  precipitate  from  which 
neither  iodine  nor  bromine  is  separated.  The  watery 
solution  smells  of  phenol  .  . 


Eosine. 


Safrosine  Scarlet. 


Phloxine. 


Bengal  Rose. 


Uranine,  Chrysoline, 


Coralline,  Aurine. 


Sulphonised  Rosaniline  Derivatives. 

The  watery  solution  is  bluish  red,  colour  disappears 
on  heating  with  soda-lye  and  reappears  on  adding  acetic 
acid.  Sulphuric  acid  turns  it  yellow,  red  on  dilution  .  Acid  Magenta. 

Easily  soluble  in  water  with  slight  greenish  colour.  On 
the  addition  of  a  little  acid  the  colour  darkens,  but  turns  » 

yellow  with  acid  in  excess.     Alkalies  discharge  the  colour     Helvetia  Green. 

Alkalies  discharge  almost  entirely.  Wool  takes  up  the 
colour  from  an  ammoniacal  solution.  The  dyed  wool  turns 
deep  blue  if  washed  in  dilute  acid  .....  Nicholson  Blue. 

Easily  soluble  in  water.  Wool  dyes  only  in  an 
acidified  solution.  Alkalies  do  not  precipitate  the  aqueous 
solution.  Commonly  sold  in  the  state  of  fragments  of  a 
metallic  lustre  ...  .  .  China  Blue. 


588 


CHEMICAL  TECHNOLOGY. 


[SECT 


IV. 


Watery  solution  violet.  Ammonia  discharges  it  com- 
pletely without  giving  a  precipitate.  Sulphuric  acid  turns 
it  orange  ;  on  dilution  with  water,  turns  green,  blue,  and 
at  last  violet  .  .  . 

Soluble  in  water  with  a  colour  varying  from  blue-grey 
to  red-grey.  HOI  gives  a  reddish  blue.  Alkalies,  red  or 
violet.  Dilute  nitric  acid,  no  change  even  on  heating 

Nitro  Colouring  Matters. 

Soluble  with  greenish-yellow  colour ;  solution  tastes 
bitter.  Alkalies  turn  it  a  dark  yellow  ;  no  precipitate  on 
adding  a  yellow  to  this  solution.  Colouring  matter  deflag- 
rates only  if  mixed  with  soda  .  ....  .  . 

Dissolves  with  gold-yellow  colour.  HC1  gives  a  yellowish- 
white  precipitate  solution  in  ether  .  .... 

Soluble  with  gold-yellow  colour.  HC1  gives  no  precipi- 
tate. It  does  not  colour  ether  ..... 

Concentrated  aqueous  solution  red ;  yellow  if  dilute ; 
sulphuric  acid  gives  no  coloration.  Acids  turn  it 
yellowish  milky ;  excess  of  alkalies,  a  dark-red  precipitate. 
Generally  sold  as  an  ammonium  salt  .... 

Benzidine-Azo  Colouring  Matters. 

Watery  solutions  red ;  trace  of  HC1  turns  it  blue. 
Strong  sulphuric  acid  turns  it  a  slate-blue,  and  there  is  no 
change  on  diluting  with  water  ..... 

Watery  solution  orange  red.  Strong  sulphuric  acid  or 
HC1  gives  a  brown  precipitate  in  a  concentrated  solution  ; 
brown  solution  on  diluting  ...  ... 

Soluble  with  blue-violet  colour ;  with  alkalies,  a  red 
solution.  Strong  sulphuric  acid  gives  it  a  violet  colour. 
HC1  a  violet  precipitate  in  strong  solution 

Solution  blue-red.  HC1  and  sulphuric  acid,  an  orange 
precipitate.  Iodine  sublimes  on  heating  this  colour 

Azo  Colours.     Yellow-Orange. 

Sulphuric  acid  gives  a  yellow  colour,  turning  to  brown- 
red  and  then  to  orange  on  dilution.  Watery  solution 
yellow.  Barium  chloride  gives  a  precipitate,  but  not  cal- 
cium chloride  ......... 

Sulphuric  acid  turns  it  violet,  red- violet  on  dilution  with 
immediate  formation  of  a  slate-green  precipitate.  Watery 
solution  yellow ;  colouring  matter  separates  out  in  crystals 
on  cooling.  Barium  and  calcium  chlorides  produce  precipi- 
tates  

Watery  solution  orange  ;  turns  violet  with  HC1.  The 
reduced  ammoniacal  solution  is  yellow.  Sulphuric  acid 
turns  it  violet-red,  changing  to  magenta-red  on  dilution. 
Sparingly  soluble  precipitate  with  barium  chloride  ;  no  pre- 
cipitate with  calcium  chloride  ..... 


Acid  Violet. 


Induline,  Nigrosine. 


Picric  Acid. 


Martins  Yellow. 


Naphthol  Yellow 


Aurantia. 


Congo  Red. 


Benzo  Purpurine 


Azo  Blue. 


Erythrosine. 


Fast  Yellow. 


Diphenylamine  Yellow* 


Azqflavine. 


SECT.    IV.] 


EXAMINATION   OF    COLOURING   MATTERS. 


589 


Sulphuric  acid  colours  it  yellow,  carmine-red  on  dilution. 
Watery  solution  yellow.  Colour  crystallises  out  on  cooling 
in  yellow  scales.  Dilute  acids  precipitate  red-violet  scales  Methyl  Orange. 

Sulphuric  acid  changes  colour  to  a  bluish  green,  passing 
on  dilution  into  a  violet  and  depositing  a  slate-blue  pre- 
cipitate. Watery  solution  yellow ;  colouring  matter  crystal- 
lises out  on  cooling.  Barium  chloride  gives  a  yellow  pre- 
cipitate which  crystallises  out  from  the  dilute  solution  in 
the  form  of  scales  .  .  .  . 

Sulphuric  acid  turns  it  a  yellow-green,  which  on  dilution 
becomes  violet  with  a  grey  precipitate.  Watery  solution 
yellow ;  colouring  matter  crystallises  out  on  cooling.Calcium 
chloride  gives  an  orange  precipitate,  which  on  heating  turns 
red  and  crystallises  ........ 

Sulphuric  acid  gives  a  carmine  colour,  which  turns 
yellow  on  dilution.  Watery  solution  is  yellow  and  often 
turbid.  With  an  alcoholic  solution  of  soda  the  colour  is 
red  to  violet.  "  Pharaoh's  serpents  "  are  formed  on  ignition 

Sulphuric  acid  turns  it  deep  orange ;  no  change  on 
dilution.  Watery  solution  is  orange.  With  calcium 
chloride,  a  finely  crystalline  salt  .  ... 

Sulphuric  acid  dissolves  it  orange-brown  ;  no  change 
on  dilution.  Watery  solution  yellow ;  on  adding  a  trace  of 
HC1  the  original  solution  crystallises  out  in  yellow  scales. 
If  more  hydrochloric  acid  is  added  the  crystals  appear  as 
grey  needles  ......... 

Sulphuric  acid,  a  carmine  solution  ;  on  dilution,  an 
orange  precipitate.  Watery  solution  red-orange.  Calcium 
chloride  gives  a  yellow  precipitate,  which  crystallises  in  red 
needles  on  adding  an  excess  of  boiling  water.  Barium 
chloride  yields  a  sparingly  soluble  crystalline  precipitate  . 

Dissolves  violet  in  sulphuric  acid ;  on  dilution,  brown 
precipitate  and  orange  solution.  Watery  solution  orange- 
red,  and  carmine-red  on  adding  soda-lye  .  .  ... 

Watery  solution  orange.  Hot  solution  deposits  a  yellow 
precipitate  on  cooling.  Sulphuric  acid  dissolves  it  yellow. 
Barium  chloride  gives  a  gold-yellow  precipitate.  Calcium 
chloride,  no  reaction  ...  ... 

Dissolves  of  a  dirty  violet  in  sulphuric  acid,  passing  into 
magenta-red  on  dilution.  Watery  solution  orange.  Barium 
chloride  gives  a  sparingly  soluble  precipitate  . 

Bordeaux  Reds. 

The  strong  hot  watery  solution  becomes  gelatinous  on 
cooling.  Acids  precipitate  red-brown  flocks.  Sulphuric 
acid  dissolves  it  with  a  green,  which  on  dilution  becomes 
violet-blue  and  deposits  after  some  time  a  dirty-brown 
precipitate  . Biebrich  Scarlet. 

Calcium  chloride  throws  down  a  red  flocky  precipitate 
which  on  boiling  becomes  crystalline  and  brown-red. 


Yellow  N  (Poirrier), 

Luteoline. 

Oitronine  (Curcumine). 
Orange  G, 

Tropaoline  0. 
Orange  II. 


Orange  I.  (Tropceoline 
000.) 


Tartrazine. 


Metanile  Yettow. 


59° 


CHEMICAL  TECHNOLOGY. 


[SECT.  iv. 


Sulphuric  acid  changes  the  colour  to  an  indigo-blue,  which 
on  dilution  becomes  first  violet  and  then  red.  The  re- 
duced ammonical  solution  of  the  colouring  matter  turns 
yellow  in  the  air  .  . 

The  hot  aqueous  solution  gelatinises  on  cooling  and 
forms  bronzy  crystals.  Dissolves  with  a  violet  colour  in 
sulphuric  acid ;  a  brown  precipitate  on  adding  water 

The  hot  concentrated  aqueous  solution  of  the  colouring 
matter  on  admixture  with  manganese  sulphate  deposits, 
on  cooling,  long  silky  crystals  of  the  manganese  salt. 
Sulphuric  acid  produces  a  blue  colour ;  wool  is  dyed  a 
scarlet-red.  The  ammoniacal  solution  if  reduced  no  longer 
becomes  yellow  on  filter-paper  .  .  .  . 

Watery  solution  a  fine  red ;  cosine  red  in  sulphuric 
acid.  Barium  chloride  gives  an  almost  insoluble  precipi- 
tate ;  calcium  chloride  gives  a  precipitate  gradually 

Watery  solution  a  fine  red.  Ammonia  turns  it  a  red- 
brown  ;  sulphuric  acid,  a  magenta-red,  turning  to  a  pure 
red  on  dilution.  Barium  chloride  gives  a  brown  precipitate, 
soluble  with  difficulty.  Calcium  chloride  gradually  gives  a 
red  precipitate  .  .  .  .  .  .  . ...  . 

Solution  dark  brownish  red,  as  also  the  dyed  wool. 
Sulphuric  acid  dissolves  it  violet,  red  on  dilution.  The 
strong  watery  solution  on  the  addition  of  a  few  drops  of 
strong  soda-lye  deposits  the  sodium  salt  in  the  form  of 
brown  shining  scales  ,  .  .  .  .  . 

Watery  solution  red  to  claret ;  barium  chloride  gives 
a  sparingly  soluble  precipitate ;  that  with  calcium  chloride 
is  easily  soluble  of  a  brown-red  colour.  Sulphuric  acid 
•dissolves  it  indigo-blue,  red  on  dilution  .... 

The  reactions  are  the  same  as  those  of  croceine  scarlet. 
The  watery  solution  mixed  with  ammonia  gives  a  dark 
violet-red  colour.  The  ammoniacal  solution  when  reduced 
is  re-oxidised  again  to  a  yellow  on  filter-paper  . 

Anthracene  Derivatives. 

The  watery  solution  is  brownish  yellow.  With  HC1, 
pure  yellow;  the  ammoniacal  solution,  magenta-red ;  soda-lye 
gives  a  violet  colour  in  the  strong  solution  of  the  colouring 
matter;  red  precipitate  with  calcium  chloride;  dissolves 
of  a  golden  yellow  in  sulphuric  acid ;  becomes  straw  colour 
on  solution.  Eeduced  with  difficulty  .... 

Watery  solution  olive-brown,  ammoniacal  solution 
green.  Brown-red  solution,  obtained  by  reduction  with 
zinc  and  ammonia ;  is  very  quickly  oxidised  in  the  air,  with 
formation  of  a  green  precipitate  .... 

Watery  solution  a  brownish-red,  becoming  green  with 
soda-lye,  and  greenish  blue  with  ammonia  ;  HC1  gives  an 
orange-yellow  solution.  The  solution  reduced  with 
ammonia  and  zinc  becomes  a  brown-red  and  is  easily 
•oxidised  in  the  air.  The  watery  solution  must  be  prepared 
cold 


Croceine  Scarlet. 


Xylidine  Ponceau. 


Croceine  Scarlet  JJB. 
Ponceau  R,  $R  and  G. 

Coccine,  Coccinine. 

Rocceline. 

Bordeaux  G  and  R. 
Ponceau  S. 


Alizarine  S. 


Coeruleine  S. 


Alizarine  Blue  S. 


SECT.   IV.] 


EXAMINATION   OF   COLOURING   MATTERS. 


Colouring  Matters  Insoluble  in  Water. 
i.  Solution  in  soda-lye  is  violet  ;  in  sulphuric  acid,  blue. 


The  colour  takes  on  tissues  mordanted  with  tannin.  Met 
with  as  a  paste  or  a  powder  .  ... 

Solution  in  strong  soda-lye,  indigo-blue ;  violet-red  on 
dilution  ;  in  sulphuric  acid  orange.  Met  with  as  a  paste 

Soluble  in  soda-lye  with  a  green  colour  ;  in  sulphuric 
acid,  the  same.  Met  with  as  a  paste  .  .  .  .  . 

Soluble  in  soda-lye  with  a  dirty  yellow ;  reduces  very 
badly.  Soluble  in  sulphuric  acid  with  a  yellow  colour. 
Met  with  as  a  straw-colour  paste  ..... 

2.  Insoluble  in  sulphuric  acid;  dissolves  in  soda-lye 
with  a  yellow  colour.     Dyes  unmordanted  cotton  a  fast 
yellow  in  a  soap-bath.     An  orange  powder 

Soluble  in  soda- lye  with  a  violet-blue  colour;  the 
alkaline  solution  mixed  with  a  little  zinc-powder  turns  red 
without  heating ;  the  paste  is  orange  .... 

Solution  in  soda-lye  a  magenta-red.  Reaction  and 
appearance  like  alizarine.  The  above  three  colouring 
matters  occur  mixed,  forming  the  different  brands  of 
commercial  alizarine  ....... 

Solution  in  soda-lye  orange  ;  in  sulphuric  acid, 
magenta-red,  giving  a  brown  precipitate  on  dilution. 
Dyes  cotton  at  once  and  forms  yellowish,  brown  paste 

Solution  in  soda-lye  is  red  ;  if  reduced  with  zinc-powder 
it  produces  deep  indigo-blue  spots  on  filter-paper.  Forms 
a  yellow  paste  *  '  . 

Solution  in  soda- lye  orange-brown ;  if  reduced,  produces 
on  filter-paper  dark,  dirty-brown  spots.  Dissolves  in 
sulphuric  acid  with  a  brownish  red  .  .  . 

Soluble  with  difficulty  in  soda-lye  with  a  green  colour  ; 
the  reduced  solution  produces  deep-blue  spots  on  filter- 
paper  ;  a  deep-blue  paste  .  .  .  .  . 

3.  The  alcoholic  solution  is  blue-grey  or  red-grey.     A 
small  quantity  of  the  dry  substance  heated  with  a  5  per 
cent,  soda-lye  and  then  extracted  with  benzene  yields  a 
colourless  or   slightly  yellowish  solution  having  a  deep 
reddish-brown  fluorescence       ...... 

Alcoholic  solution  deep  blue,  greenish  on  adding  HC1 ; 
turns  brown  with  soda-lye.  No  fluorescence  with  benzol. 
Dissolves  reddish  brown  in  sulphuric  acid 

4.  Alcoholic  solution  turns  brown-red  if  mixed  with  HOI. 

5.  Alcoholic  solution  bluish  red  with  intense,  splendid 
vermilion  fluorescence 

6.  Bluish  red  alcoholic  solution,  with  greenish-yellow 
fluorescence,  disappearing  on  addition  of  HOI.  Colour  turns 
yellow      .......... 

Blue-red  alcoholic  solution  has  a  brick-red  fluorescence, 
disappearing  on  adding  HC1.  Colour  turns  orange  . 

7.  Pulverised  substance,  insoluble  in  alcohol;  reduced 
with  zinc  and  ammonia,  gives  a  yellow  liquid,  which  produces 
spots  on  filter-paper  .  ..... 


Gallocya-nine. 


Galleine. 


Ceruleine. 


Galloflavine. 


Canarine. 


Alizarine. 


Anthra- 
purine. 


and     Flavo-pier- 


Chrysamine. 


Nitro-alizarine. 


Alizarine  Maroon. 


Alizarine  Blue. 


Induline,  Nigrosine. 


Diphenylamine  Blue. 
Indophenol. 

Magdala  Red. 


Primrose. 


Cyanosine. 


Indigo . 


SECTION    V. 
GLASS,   EARTHENWARE,   CEMENT  AND   MORTAR. 


GLASS  MANUFACTURE. 

THE  manufacture  of  glass  is  exceedingly  ancient.  As  the  Temple  of  Belus  in  Egypt, 
the  age  of  which  is  estimated  at  12,000  years,  was  constructed  of  bricks  covered  with 
a  glaze,  the  production  of  glass  cannot  be  very  much  less  ancient.  The  composition 
of  certain  specimens  of  glass  from  Autun,  traceable  to  the  second  century  is,  according 
to  Peligot : 


SiO2  .... 

667 

...    66-0     ... 

67-4 

...     70-9     ., 

.     69-4     ., 

•     69-4 

CaO   .... 

5-8 

...      7-2     ... 

27 

...      7-9     -, 

6-4     .. 

,.      7'i 

A12OS,  Fe203,  Mn2O,    . 

2-8 

...      3-0     ... 

5'4 

...      4'5     •• 

.       2-9     ., 

,.      2-8 

Na20,  K,0 

247 

...     23-8      .. 

24-5 

...     167     .. 

.     21-3     . 

..     207 

Composition  of  Glass. — If  we  leave  out  of  consideration  the  glasses  soluble  in  water 
and  varying  in  composition  between  R20.2Si02  and  R20.4Si02,  glass  may  be  regarded 
as  a  mixture  of  silicates  obtained  by  fusion,  liquid  at  high  temperatures,  becoming 
pasty  as  it  cools,  and  finally  congealing  to  a  hard,  amorphous,  and  generally 
transparent  mass.  The  condition  is  that,  besides  the  compounds  of  silica  (in  part  re- 
placeable by  boric  acid)  with  potassium  or  sodium,  there  must  be  simultaneously  present 
silicates  of  metals  of  the  calcium,  magnesium,  or  iron  group,  in  order  to  render  the 
alkaline  silicate  as  far  as  possible  capable  of  resisting  atmospheric  and  chemical 
influences.  As  the  lime  and  lead  silicates  are  chiefly  selected  to  this  end,  with  other 
metals  in  case  of  coloured  glass,  we  can  distinguish  mainly  the  following  groups : — 

(i)  Alkaline  silicates  or  soluble  glass  ;  (2)  Soda-lime  silicates  or  soda  glass ;  (3)  potash 
lime  silicates  or  potash  glass ;  (4)  Alkali-lead  silicates  or  lead  glass  ;  (5)  coloured  glass. 

If  we  take  the  constituents  of  glass  as  anhydrides,  the  simplest  formula  for  soda- 
glass  is  £cNa20.2/Ca0.2;SiOj ;  in  potash  glass  Na  is  replaced  by  K,  and  in  lead  glass 
Pb  is  substituted  for  Ca. 

Dumas  was  of  opinion  that  glass  has  quite  as  definite  a  composition  as  certain 
minerals,  or  is  at  least  a  mixture  of  definite  silicates ;  the  glasses  which  he  examined 
gave  the  proportion  of  saturation  Na2O.Ca0.4SiO2.  This  formula  would  indicate  for 
soda  glasses  the  composition  Si02  67*0  per  cent.,  Na20  iy'3  per  cent.,  and  CaO  15*7  per 
cent. ;  for  potash  glasses  6i'6  per  cent.  Si02,  24-1  per  cent.  K20,  and  14*3  per  cent.  CaO, 
If  we  compare  the  composition  of  good  glasses  met  with  in  commerce  we  find  that  the 
latter  contain  much  more  silica.  But  since  Berthier  has  shown  that  an  increase  of  silica 
renders  glass  less  fusible  and  harder,  whilst  lime  gives  it  the  power  of  resisting  certain 
chemical  influences,  Benrath  regards  as  "  glass  "  also  silicates  whose  saturation  answers 
to  the  general  formula  R0.2Si02.  He  points  out  that  the  most  favourable  composition 
for  all  purposes  of  the  glass  manufacture — excepting  optical  glasses — falls  between  the 
boundaries  Na2O.Ca0.6SiO2  and  5Na20.7Ca0.36SiO,,  where,  of  course,  Na  may  be 
replaced  by  K  and  Ca  by  Pb.  Hence  would  follow  the  subjoined  compositions  : — 


SECT.    V.] 


GLASS  MANUFACTURE. 


593 




SiO, 

Na-jO. 

K,0. 

CaO. 

PbO. 

K,O.CaO.6Si02    . 

70-6 

— 

18-4 

II'O 

_ 

Na.2O.Ca0.6SiO2  . 

75-3 

13-0 

— 

117 



EgO.PbO.6SiO.,    . 

— 

I3-9 

32-9 

5K2O.7Ca0.36Si02 

71-5 

— 

15-6 

12*9 

SNajO.  7CaO.  36SiO2 

75-5 

10-8 

137 



5K20.7Pb0.36SiO2 

51-6 

— 

11  '2 

37'2 

Composition  of  Soda  Glass. 




Si02. 

Na2O. 

K20. 

CaO. 

MgO. 

Pe203. 

A1,0S. 

MnO. 

Sb08. 

Window  glass,  Saarbruck  . 

71-27 

12-50 

— 

H'lS 

— 

1-44 

-^  _ 

—  ' 

— 

O'2I 

„            „      Witten 

72-25 

13-02 

— 

13-40 



v~ 

1-23 

— 

O'I2 

„            „      Stollberg   . 

72-42 

12-71 

— 

13-81 

— 

0-93 

— 

0*14 

Flask,  from  Stender,  Hanover  . 

7379 

I3-94 

0-60 

8-61 

O'I2 

0-68 

0-58 

0*32 

— 

Mirror  glass,  Miinsterbusch 

72-31 

11-42 

— 

14-96 

— 

0.81 

— 

- 

Window  glass,  from     „ 

72-80 

12-30 

— 

14-10 



073 





Combustion-tube,  Warm-  ) 
brunn,  Quilitz  &  Co.    j 

74-06 

11-46 

3-92 

971 

— 

0-98 

— 

— 

White    medicine   bottles,  | 
Rhenish  Works 

72-07 

18-45 

— 

8-96 

— 

o-54 

— 

— 

White  vessel,  from  Zwiesel 

78-39 

13-91 

— 

7-10 

— 

O'2I    |    O.24 

0-15 

— 

Cast  mirror  glass,  Dorpat  . 

74  'OS 

10-95 

— 

12-96 

— 

I-87 



— 

Beaker  glass,  St.  Petersburg 

74-66 

10-36 

4'32 

9T3 

— 

078 

— 

— 

Russian  semi-white  vessel  glass 

74-00 

17.44 

7-35 

— 

O'2I 

0'2O 

0-8o 

— 

»              »                    ii          • 

69-99 

17-96 

— 

9-90 

— 

0-39 

I'll 

0-65 

— 

Venetian  window  glass 

68-60 

8-10 

6-90 

11-90 

2*IO 

I'20 

0-30 

— 

— 

White  glass,  Bagneaux,  Nemours 

72-00 

17-00 

— 

6-40 

— 

I'lO 

2  '60 

— 

— 

French  medicine  bottles   . 

62-00 

16-40 

— 

15-60 

2  -2O 

O-7O 

2-40 

— 

— 

French  crown   glass,) 
for  lighthouses       ) 

72-10 

I2-OO 

— 

1570 

— 

trace 

trace 

— 

— 

English  mirror  glass,  St.  Helens 

77-36 

13-06 

3-02 

5-3I 

— 

0-92 

trace 

— 

— 

Do.,  Thames  Co.,  London  . 

78-69 

11-63 

i'34 

6'io 

— 

trace 

2-68 

— 

— 

Do.,  London  &  Manchester  Co.  . 

77-91 

12-36 

173 

4-85 

— 

^  „ 

3-60 

trace 

— 

Window  glass,  Charleroi,  ) 
Belgium                      j 

74-82 

13-01 

— 

ll'2l 

— 

i 
1-03 

— 

trace 

American  pressed  glass     . 

75-00 

18-62 

— 

5-i8 

0-52 

0-19 

O'll 

0-38 

— 

Potash  Glass. 


^ift 

Kn 

Port 

MffO 

Al.,0, 

MnO 

White  glass,  Venice     . 

68-60 

6-90 

8-10 

11*00 

2'IO 

0-20 

I  '20 

O'lO 

„            Bohemia 

7170 

12-70 

2-50 

10*30 

— 

0-30 

0*40 

O'20 

Bohemian  tubing         . 

74-40 

18-50 

— 

7-20 

— 

— 

O*IO 

— 

»            i)              • 

73-I3 

11-49 

3-07 

10-43 

O-26 

0-13 

0-30 

0-46 

it            »»              • 

7f60 

ii-oo 

10*00 

2-30 

3-90 

2*20 

0'20 

„        mirror 

67-70 

21  'GO 

— 

9-90 

— 

— 

1*40 

— 

„        average  glass 

76-00 

I5-OO 

— 

8-00 

— 

— 

1*00 

— 

Wine  glass,  Nortjo,  Finland        .        . 

74-37 

I2-7I 

3-42 

9*02 

— 

O 

•71 

— 

62*29 

21*12 

6*78 

6-;o 



3 

•25 

•Mi 

Russian  beer  glass        .... 

73'90 

12-55 

6*90 

5-65 

— 

0 

•90 



2    P 


594 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


Si02. 

K2O. 

Na20. 

CaO. 

PbO. 

FeoO, 

Al  0 

MnO. 

r  e»V3. 

2    3- 

Crystal  glass,  Boneche 

56-00 

6-60 

— 

— 

34-40 

_^_ 

I'OO 



„          from  London  for) 
chemical  apparatus}  * 

59-20 

9-00 

— 

— 

28-20 

0-40 

.  —  •" 

I'O 

„         from  Newcastle        . 

5IHO 

9-40 

— 

— 

37-40 

2'OO 

— 

„          from  Baccarat          . 

5I-IO 

7'6o 

170 

— 

38-30 

I-30 

— 

French  lamp  glass       .         .        . 

48-10 

12-50 

— 

o'6o 

38-00 

0-50 

— 

— 

Flint  glass,  Guinaud    .         .         . 

42-50 

11-70 

— 

0-50 

43-50 

— 

i.8J 

As205 

trace 

„          Waldsteien,  Vienna  . 

75-24 

12-51 

— 

1-48 

10-48 

trace 

trace 

— 

French  pressed  glass   . 

50-18 

IJ'62 

— 

— 

38-11 

trace 

0-14 

trace 

English      „          „       . 

61-27 

7-07 

7'55 

1-05 

22-36 

— 

0-86 

— 

Schott  made  a  number   of  experiments,  giving  glasses  of    the    following    com- 
positions : — 


- 

I. 

II. 

ill. 

IV. 

V. 

VI. 

VII. 

VIII. 

MoL 

p.c. 

Mol. 

p.c. 

Mol. 

p.c. 

Mol. 

p.c. 

Mol. 

p.c. 

Mol. 

p.c. 

Mol. 

p.c. 

Mol. 

p.c. 

Si02      . 

2 

5°  '4 

3 

60-4 

4 

67-0 

5 

71-8 

6 

75'3 

3 

50-0 

4 

S7'i 

5 

62-4 

CaO      . 

I 

23.6 

i 

18-8 

I 

15-6 

i 

13-4 

I 

117 

i 

l.S-6 

i 

i.V.S 

I 

12-6 

Na20     . 

I 

26-0 

i 

20-8 

I 

I7-4 

i 

14-8 

I 

13-0 

2 

34  '4 

2 

29-6 

2 

26-0 

The  glass  I.  was  completely  devitrefied  on  slow  cooling ;  II.  chiefly,  and  III.  (which 
answers  to  the  formula  of  Dumas)  but  little ;  IV.,  which  corresponds  to  the  formula 
Na8O.CaO.5SiOr  was  very  good.  Sample  V.  could  be  melted  only  with  great  difficulty; 
VI.  was  half  devitrified  ;  VII.  and  VIII.  were  apparently  good,  but  would  have  been 
too  little  resistant.  Schott  believes  that  no  single  unitary  formula  can  be  proposed 
for  all  glasses  in  common  use.  Window  glass  may  answer  to  the  above  formula, 
Na2O.CaO.5SiO, ;  mirror  glass  must  contain  more  silica,  but  less  lime;  and  glass  for 
vessels,  bottles,  &c.,  more  lime. 

R.  Weber  gives  the  following  analyses  of  good  glasses  : — 


8i02. 

Alj,Os. 

CaO. 

MgO. 

PbO. 

K2O. 

Na.,0. 

In  all. 

Si02-CaO-Na2O. 

71-23 

170 

16-39 

O'20 

— 



1078 

IOO-30 

4-0-1-0-60 

71-03 

2-98 

15-62 

0-15 

— 

— 

10-76 

100-54 

4-2-1-0-60 

71-92 

0-85 

I3-65 

0-16 

— 

— 

13-42 

lOO'OO 

4-8-1-0-88 

73-35 

073 

11-91 

071 

— 

— 

13-12 

loo-oo 

5-3-1-0-90 

72-68 

I  -06 

12-76 

0*26 

— 

— 

13-24 

100  -OO 

5-2-1-0-90 

72-66 

0-95 

15-20 

0-25 

— 

— 

10-94 

lOO'OO 

4-4-1-0-60 

70-58 

I  -01 

16-07 

0-80 

— 

— 

1177 

99-23 

3-8-I-O-6O 

74-58 

•23 

S'57 

0-14 

0'34 

17-90 

— 

99-76 

I2-5-I-2-00 

75-81 

•oi 

7-38 

O'lO 

— 

11-39 

4-84 

100-53 

9-6-1-1-50 

72-13 

•41 

11-51 

— 

— 

5'66 

10*06 

10077 

5'8-J-I-OO 

75-23 

•12 

8  'oo 

0-03 

— 

6-38 

8-84 

1  00  '60 

8-8-I-I-50 

70-07 

•02 

12-13 

0-32 

— 

I5-03 

2-00 

100-57 

5-2-I-0-85 

5370 

•12 

0*17 

— 

37-02 

7-36 

O7O 

100-07 

5-3-I-0-50 

5370 

•07 

o'59 

— 

34-9I 

9'12 

0-30 

99-69 

5-3-1-0-60 

52-41 

0-96 

077 

— 

35-24 

10-37 

0'08 

99-83 

5-1-1-0-64 

45-24 

0-82 

0-36 

— 

47-06 

6-80 

— 

100-28 

3-5-1-0-33 

Glass  when  in  a  state  of  full  fusion  dissolves  metals  (gold,  copper,  silver,  lead),  oxides 
(SnO,,  Cr203,  A1203,  Fe3O4,  Mn304,SiO,,  CaO),  and  salts  (calcium  phosphate,  aluminium 
fluoride,  sodium  sulphate),  and  if  quickly  cooled  forms  a  homogeneous,  amorphous  mass. 
If  cooled  slowly  a  part  of  the  dissolved  matter  separates  out  either  in  crystals  or  in  an 
amorphous  state.  Even  the  excess  of  alkali  seems  to  be  merely  in  a  state  of  solution. 
Glass  melted  with  alkali  corresponds  to  the  same  saturation  ;  it  dissolves  at  high 
temperatures  up  to  84  per  cent,  of  silica  in  excess,  which  on  slow  cooling  separates  out 


SECT.  T  J  GLASS   MANUFACTURE.  595 

Calcium  in  glass  can  be  substituted  by  a  series  of  other  elements.  Thus  on  melting 
together — 

I.  IL 

Sand         ....     250  ...  250 

Sodium  carbonate    .        .     100  ...  100 

Magnesia ....       50  ...  50 

Calcium  carbonate   .        .     —  ...  60 

Pelouze  obtained  the  following  glasses : 

SiO2  »       .        .        .  68-9  ...  657 

Na.,0  ....  16-2  ...  15-0 

MgO  ....  14-9  ...  12-0 

CaO  ....  ...  7'3 

Specific  gravity      .       2-47  ...  2-54 

These  glasses  are  very  fusible  and  readily  become  devitrified,  especially  II. 

Whilst  compounds  of  barium  and  strontium  have  often  been  added  to  mixtures  for 

glass,  Benrath  has  shown  that  apparently  the  alkali  can  be  replaced  by  baryta,  as  the 

following  analyses  of  three  specimens  of  glass  show,  of  which  III.  had  been  prepared  at 

St.  Gobin,  according  to  Peligot : — 

i.  n.  in. 

SiO2         .        .        .    44-93  ...  54-69  ...  46-5 

CaO          .        .        .      6-61  ...  17-06  ...  6-3 

BaO          .        .         .     44-98  ...  24-51  ...  47-2 

Al203.Fe2Os       .        .3-48  374 

But  these  glasses,  scarcely  corresponding  to  the  saturation  R0.2Si02,  are  rapidly  attacked 
even  by  dilute  mineral  acids,  and  are  consequently  quite  useless.  The  following  glass, 
(I.)  was  good ;  its  composition  approximates  to  the  equivalent  proportion  : 

Na2O.CaO.BaO.9SiOg. 

I.  n. 

Si02 65-14  ...  74-19 

Nap                    .        .         .  9-37  ...  17-02 

CaO            ....  5-29  ...  2-88 

PbO ...  0-86 

BaO 17-18  ...  5-16 

Al2Ot.Fe2Os         .        .         .  2-57  ...  0-58 

S03             ....  0-45  ...  0-28 

II.  is  the  analysis  of  a  good  English  compressed  glass,  of  the  sp.  gr.  2-524.  A 
good  barium  lead  glass  is  made  at  Mastricht  with  witherite,  corresponding  to  the 
formula  4K20.2Ba0.3Ca0.3Pb0.36SiO,,  and  is  mentioned  by  Benrath  in  support  of 
his  formula. 

We  may  notice  the  attempts  of  Lamy  to  introduce  thallium  into  glass.  From 
300  parts  sand,  400  thallium  carbonate  and  100  parts  potassium  carbonate  or  300 
sand,  200  red  lead,  and  335  thallium  carbonate,  he  obtained  an  easily  fusible,  quite 
homogeneous  glass  of  sp.  gr.  4.235,  and  with  an  index  of  refraction  for  the  yellow  ray  of 
1*71 ;  finally  he  succeeded  in  obtaining  a  glass  of  sp.  gr.  5*625  and  a  refractive  index  of 
1-965. 

On  the  other  hand,  calcium  may  be  in  part  replaced  by  zinc ;  a  very  good  glass  for 
optical  purposes  by  Maes,  of  Clichy,  has  the  following  composition : — 

Alkali  and 

Si02.  ZnO.  PbO.        Fejj03  and  A1Z0S.  CaO.  As.  Boric  acid. 

56-61       ...       I3'5o      ...      4'io      ...      0-40      ...      070      ...      trace      ...      24-69 

Bottle  glass,  prepared  from  very  impure  materials,  can  only  approximately 
correspond  to  the  normal  formula,  on  account  of  its  high  percentage  of  ferric  oxide  and 


596 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


alumina,  as  it  appears  from  the  composition  of  good  bottles.  If  the  proportion  of 
alumina,  lime,  and  alkali  exceeds  a  certain  limit  the  glass  becomes  less  capable  of  resist- 
ing water  and  acids,  and  is  consequently  useless.  The  following  analyses  of  bottles 
which  have  proved  bad  in  practice  show  that  the  proportion  of  the  ingredients  of 
glass  cannot  be  made  to  vary  very  widely : — 

Analysis  of  Bottles. 


Si02. 

Na2O. 

K20. 

CaO. 

MsrO 

rip  o 

Al  O 

MnO. 

SO.. 

••^Wi 

*  e2u3- 

Ai2*-'3' 

Good  wine  bottles,  Souvigny     . 

6o'00 

3'IO 

— 

22-30 



4'OO 

8-00 

I  '20 



„              „        St.  Etienne  . 

60*40 

3-20 

BaO 
0-90 

20-70 

0-60 

3^0 

10-40 

— 

— 

„              „        Epinac 

59-60 

3-20 

— 

18-00 

7-00 

4-40 

6-80 

o'40 

PA 

0-40 

Good  Champagne  bottle    . 

58-40 

9-90 

I  -80 

1  8  -60 

— 

8-90 

2'IO 

— 

— 

Bottle  glass,  Follembray   . 

61-35 

2'8o 

2'OI 

24-66 

— 

5'5I 

3-67 

— 

— 

„           Montplaisir   . 

66*04 

2-83 

2-82 

22-88 

— 

278 

2-65 

— 

— 

French  bottle,  attacked  by  wine 

52-40 

— 

4-40 

32-10 

— 

6  -00 

S'lO 

— 

— 

English  do.,  do.          ... 

49-00 

7-25 

2'OO 

2475 

2'OO 

lO'OO 

4-10 

trace 

— 

Good  English  wine  bottle  . 

59-00 

lO'OO 

I-70 

19-90 

0-50 

7-00 

i  -20 

— 

— 

Do.  at  Paris  Exhibition      . 

53-25 

4-25 



25-5° 

2-OO 

i 

;-o 

_ 

Swedish  bottle,  ineted  with) 
fluor-spar                        J 

55-20 

6-99 

2-85 

15-40 

I  -08 

3-6o 

•>. 

II'OO 

279 

^ 

F 
1-75 

Bottle  from  Siemens,  Dresden  . 

63-91 

7-05 

— 

14-52 

— 

•  ^^-  

13-97 

o-55 

Water  bottle,  bad 

69-55 

13-61 

O'4I 

15-09 

0-42 

o-33 

0-42 

— 

Do.,  attacked  by  water 

70-12 

13-01 

0-42 

14-94 

0-38 

o-39 

X—  •» 

0-37 

-s 

— 

— 

Do.,  corroded    .        .                 . 

72-63 

14-86 



9-92 



1 

2 

07 



trace 

Dull  window  pane     .                 . 

69-37 

2I'II 

— 

7^4 

— 

I 

55 

— 

0*40 

Opaque  glass 

73^4 

I6-54 



7-85 

— 

I 

59 

— 

0-38 

Opalescent  mirror  glass 

7370 

I7-I8 

— 

6-53 

— 

I 

89 

— 

070 

Spotty  window  glass 

66-47 

5-6i 

18-79 

5'6o 

— 

3 

10 

— 

— 

Lime-Alumina  Glass. — Pelouze  has  attempted  the  production  of  an  alumina-glass 
without  arriving  at  results  of  importance.  Korschelt  recommends  the  production  of  a 
white  glass  from  alumina,  silica,  and  lime.  As  raw  materials  he  takes  the  kaolin  of 
Meissen  (consisting  of  77  per  cent,  silica,  18  per  cent,  alumina,  and  5  per  cent,  water) 
along  with  a  calc-spar  free  from  iron  burnt  lime.  Quartz  is  added  only  if  the  kaolin 
does  not  contain  sufficient  silica.  The  mixture  is  regulated  so  that  it  consists  of  55-67 
silica,  10-18  alumina,  and  15-35  lime.  A  mixture  of  100  parts  Meissen  kaolin  and  41 
parts  burnt  lime  would,  e.g.,  contain  55-2  per  cent,  silica,  14-2  alumina,  and  30*6  per 
cent.  lime.  The  lime  of  the  mixture  can  be  partially  or  entirely  substituted  by  baryta 
or  magnesia.  Magnesia  makes  the  mixture  less  fusible  but  permits  of  the  use  of 
magnesian  limestones,  dolomite,  &c. 

Phosphatic  Glass,  obtained  from  fused  calcium  phosphate,  is  recommended  for  vessels 
which  have  to  come  in  contact  with  hydrogen  fluoride. 

Solubility  of  Glass. — Whilst  Boyle  (1664)  and  Margraf  were  of  opinion  that 
earth  could  be  produced  from  pure  water  by  continued  distillation,  Kunkel  (1744) 
and  Scheele  and  Lavoisier  (1770)  were  aware  that  glass  is  more  or  less  dissolved 
by  water.  Glasses  rich  in  alkali  become  damp  on  exposure  to  the  air,  gradually  lose 
their  lustre,  become  semi-transparent,  and  have  sometimes  an  iridescent  surface. 
The  same  phenomena  occur  if  glass  has  been  placed  for  a  long  time  in  water  or 
moist  earth:  the  water  extracts  the  alkalies,  the  surface  loses  its  compactness  and 
exfoliates.  According  to  Hausmann,  a  glass  thus  decomposed  had  the  following  com- 
position : — 


SECT,  v.]  GLASS  MANUFACTURE.  597 

SiO*  A1203.          CaO.  MgO.          FeO.  Na20.  K,O.  Hj.0. 

Undecomposed  part  59-2     ...    5-6     ...     7*0    ...     1*0    ...    2*5     ...     217     ...     3*0    ...      

Decomposed  surface  48-8    ...     3-4    ...  11-3     ...    6*8     ...  11-3     ...      ...      ...     iy* 

The  decomposition  by  water  increases  rapidly  with  the  rise  of  temperature.  Griffith 
found  that  on  slow  ebullition  water  extracted  from  flint  glass  7  per  cent. ;  the  solution 
contained  no  lead. 

According  to  Pelouze  two  samples  of  glass  of  the  following  compositions : — 

L  II. 

SiO,       .       .     .  .       .    72-1  ...  77-3 

CaO        ....     15-5  ...  6*4 

Na/)       ....     12-4  ...  16-3 

when  powdered  and  boiled  in  water,  lost,  I.,  10  per  cent.;  and  II.,  32  per  cent.  The 
solution  contained  basic  silicate  and  always  a  little  sulphate.  Powdered  glass  on 
exposure  to  the  air  slowly  absorbs  carbon  dioxide  and  at  once  exerts  an  alkaline 
reaction  with  litmus  paper.  Benrath  digested  16  parts  powdered  glass  for  three  days 
and  obtained  in  the  solution  0*193  parts  of  the  following  composition : — 

Si02.  CaO.  Na.jO.  A1ZO3.  SOS.  Ca2. 

Glass  used     .     76*27      ...      6*09      ...       16*38      ...      0*63      ...      trace 
Kesidue          .     28*43      •••  •••      47'39      •••       —        •••        O'i8          ...    24*00 

Here  a  strongly  basic  alkaline  silicate  had  been  extracted.  When  Daubree  treated 
glass  with  superheated  steam  under  pressure  it  was  completely  resolved  into  silica, 
Wollastonite  (CaSi03),  and  alkaline  silicate. 

Emmerling  shows  that  the  loss  of  weight  of  a  glass  vessel  by  the  action  of  liquids 
depends  on  the  time  of  boiling,  the  size  of  the  surface  wetted,  its  condition,  the 
composition  and  the  concentration  of  the  solution.  The  speed  of  evaporation  is  not 
essential.  The  composition  of  the  glasses  examined  was — 

a.                        &.  c.  d. 

Si02  .  .  .  73*79  ...  72*69  ...  74*14  ...  79*57 

A120$  .  .  0*58  ...  0*63  ...  1*15  ...  0*35 

Fe20,  .  .  0*68  ...  0*97  ...  0*68  ...  0*24 

MnO .  .  .  0*32  ...  0-54  ...  0*49 

CaO   .  .  .  8*61  ...          9*20  ...  6*94  ...  7*18 

MgO  .  .  .  0*12  ...          0*34  ...  0*24  ...  0*18 

Na,O  .  .  13-94  ...  12*83  ...  15*07  ...  3*45 

K^O    .  .  .  0-60  ...          1*77  ...  0*60  ...  8*04 


98-64  98-97  99*31  99*01 

In  experiments  with  glass  flasks  containing  600  to  700  c.c.  of  the  first  sort  of  glass, 
using  400  c.c.  of  the  liquid  in  question  and  replacing  the  water  lost  by  evaporation, 
there  was  found  on  boiling  with  pure  water  in  the  first  hour  a  decrease  of  weight 
of  3*9  milligrammes;  in  the  second,  2*7  milligrammes,  and  during  the  following  twenty- 
eight  hours  losses  of  2*5  to  1*5  milligramme.  Hydrochloric  acid  at  1 1  per  cent,  dissolved 
in  the  first  hour  4-2  and  5*3  milligrammes ;  in  the  following  only  0*9.  Hydrochloric  acid 
of  0*2  to  3  per  cent,  dissolved  scarcely  anything.  The  action  increases  thus  both  with 
greater  dilution  and  with  greater  concentration  ;  0*008  per  cent,  nitric  acid  counteracts 
the  solvent  power  of  water ;  i  per  cent,  dissolved  3  milligrammes.  Sulphuric  acid  from 
0*25  to  25  per  cent,  dissolves  hourly  about  3*8  milligrammes,  and  i  per  cent,  oxalic 
acid  dissolves  o'i  and  0*2  milligramme.  Alkaline  liquids  attack  glass  especially 
readily. 

From  these  researches  it  appears  that  in  accurate  work  no  new  glass  vessels  should 
be  used,  that  liquids  should  be  boiled  in  them  for  as  short  a  time  as  possible.  Alkaline 
solutions,  even  if  dilute,  should  not  be  heated  in  glass  vessels. 


598  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

Kreusler  calls  attention  to  analytical  errors  which  may  be  occasioned  by  the 
alkaline  reaction  of  glass.  In  order  to  determine  the  behaviour  of  different  sorts  of 
glass  with  water,  glass  tubes  were  fixed  in  the  necks  of  small  boiling-flasks  containing 
about  50  c.c.  of  water  in  such  a  manner  that  on  boiling  they  might  act  as  reflux 
condensers.  The  contents  of  the  flasks  were  then  titrated  and  the  result  calculated  for 
nitrogen  (in  determinations  of  ammonia),  and  in  caustic  alkali.  For  1000  square 
centimetres  of  surface  attacked  the  result  was  hourly,  if  calculated  for  the  first 
two  to  three  hours  : 

Thuringian  glass,  I .     24/0 

,,      2  . 3-2 

Bohemian  combustion  tube 0*3 

Fusible  potash  glass 0*5 

calculated  in  milligrammes  nitrogen.  On  the  basis  of  the  entire  duration  of  the 
experiment  the  loss  was  reduced  in  the  first  two  cases  respectively  to  9-5  and  2*04 
milligrammes  nitrogen.  With  the  other  two  kinds  of  glass  the  result  was  not  altered. 
According  to  the  experiments  of  Stass,  glasses  rich  in  silica  and  free  from  alumina 
stand  best.  A  glass  of  the  following  composition  totally  resisted  the  attacks  of  acids 
and  dilute  alkalies : — 

Si04.  KS0.  NU..O.  CaO. 

77-o  ...  77  ...  5'°  io*3 

Weber  and  Wiebe  show  that  glass  intended  for  the  manufacture  of  thermometers 
should  contain  as  alkali  only  soda,  or  only  potash.  To  test  the  resistance  of  glass 
Weber  exposes  the  articles  to  the  fumes  of  hydrochloric  acid.  Good  glasses  when 
dried  should  show  no  coating. 

Devitrification. — As  far  back  as  1727  Reaumur  observed  that  glass  exposed  for 
some  time  to  a  temperature  at  which  it  softens  but  does  not  melt  becomes  dull,  opaque, 
and  of  a  milky  white.  Opinions  still  differ  on  the  cause  of  this  phenomenon.  Dumas 
and  Peligot  hold  that  definite  silicates  crystallise  out  of  the  glass,  leaving  the  rest  as  a 
kind  of  mother  liquor.  Glasses  rich  in  silica  are  most  easily  devitrified. 

Coloured  Glasses. — Combustion  tubes  used  in  organic  analysis  sometimes  take  a 
fine  red  colour.  If  glass  is  coated  with  a  mixture  of  copper  oxide  and  some  adhesive 
matter,  and  ignited,  it  takes  up  copper,  but  remains  colourless.  On  heating  in  hydrogen 
or  any  other  reducing  glass  it  becomes  a  fine  red.  More  beautiful  is  the  "  copper 
ruby  "  obtained  by  fusion.  If  glass  is  melted  with  i  per  cent,  copper  oxide,  on  adding 
2  per  cent,  of  tin  or  i|  per  cent,  forge-scales,  there  is  obtained  a  glass  which  is  colour- 
less or  merely  greenish,  but  if  it  is  heated  to  the  point  of  softening  it  suddenly  takes 
an  intense  red,  the  well-known  colour  of  old  church  windows.  Copper  ruby  contains 
0*42  to  o'66  of  metallic  copper.  If  the  proportion  is  increased  glass  takes  up  6-75 
per  cent,  copper  as  a  maximum  and  then  becomes  opaque. 

Hematinon. — This  is  a  glass  resembling  that  found  in  the  Pompeiian  excavations, 
and  mentioned  by  Pliny.  It  posesses  a  beautiful  red  colour,  between  that  of  vermilion 
and  of  minium,  is  opaque,  harder  than  ordinary  glass,  bears  a  high  polish,  and  has 
a  sp.  gr.  =  3-5.  The  colour  is  lost  by  melting,  and  by  no  addition  can  be  recovered. 
The  glass  contains  no  tin  or  cupreous  oxide  as  a  colouring  matter.  Von  Pettenkofer 
assimilated  to  this  glass  by  melting  together  silica,  lime,  burnt  magnesia,  litharge 
soda,  copper-hammerings,  and  smithy  scales.  A  part  of  the  silica  in  the  mixture  is 
decomposed  by  means  of  boric  acid,  and  a  mass  is  obtained  which,  when  ground  and 
polished,  exhibits  a  dark  red  colour  of  great  beauty.  Pettenkofer  gave  to  this  glass 
the  term  astralite,  from  the  beautiful  shotte- colour  of  blue  or  dichromatic  tint  shim- 
mering throughout  the  mass. 

By  a  somewhat  similar  process  we  obtain  Aventurine. 

Aventurine  Glass. — Aventurine  or  avanturin  glass  was  formerly  made  only  in  the 


SECT,  v.]  GLASS  MANUFACTURE.  599 

Island  of  Murano,  near  Venice,  but  is  now  prepared  throughout  Germany,  Italy, 
Austria,  and  France.  It  is  a  brown  glass  mass  in  which  crystalline  spangles  of  metallic 
copper  according  to  Wohler  (of  cuprous  oxide  according  to  Von  Pettenkofer)  appear 
dispersed.  Fremy  and  Clemandot  have  produced  a  glass  similar  to  aventurine  glass, 
and  which  consisted  of  300  parts  glass,  40  parts  cuprous  oxide,  and  80  parts 
copper  scale.  The  Bavarian  and  Bohemian  glass  houses  produce  an  aventurine  glass 
rivalling  the  original.  Von  Pettenkofer  has  prepared  aventurine  glass  direct  from  hema- 
tinon  by  mixing  sufficient  iron-filings  with  the  molten  mass  to  reduce  about  half  the 
copper  contained.  Pettenkofer  surmises,  and  with  good  reason,  that  aventurine  glass 
is  a  mixture  of  green  cuprous  oxide  glass  with  red  crystals  of  cuprous  silicate,  these 
complementary  colours  giving  the  brown  tint.  This  glass  is  also  well  imitated  by 
melting  a  mixture  of  equal  parts  of  ferrous  and  cuprous  oxides  with  a  glass  mass. 
The  cuprous  oxide  appears  after  a  long  annealing  as  a  separate  crystalline  red 
combination,  while  the  ferrous  oxide  is  lost  in  the  green  colour  it  imparts  to  the  glass. 
Pelouze  found  that  by  freely  adding  potassium  chromate  to  the  glass  materials 
spangles  of  chromium  oxide  were  separated.  He  termed  this  glass  chrome-aventurine ; 
it  has  been  employed  by  A.  Wachter  in  the  glazing  of  porcelain. 

The  production  of  gold  ruby  glass  was  known  to  Neri  (1612)  but  it  was  first  brought 
under  full  control  by  Kunckel.  According  to  the  researches  of  Miiller  and  Knapp, 
glass  dissolves  only  a  small  proportion  of  metallic  gold  ;  20  milligrammes  of  gold  are 
sufficient  to  give  a  uniformly  fine  colour  to  i  kilo,  of  lead  glass ;  other  glasses  are  less 
readily  treated.  If  the  glass  is  cooled  quickly,  the  metallic  gold  is  like  copper  in  a 
colourless  state,  and  on  reheating  changes  into  the  coloured  variety. 

Glass  with  a  mixture  of  fine  silver  oxide  or  silver  chloride,  coated  over  with 
clay  and  water  and  heated  in  a  muffle,  takes  a  fine  yellow  colour.  According  to 
Bontemps  this  sometimes  takes  place  in  the  cold.  Metallic  silver  dissolves  in  glass, 
which  takes  yellow  or  orange  shades.  From  8  to  92  milligrammes  metallic  silver  ore, 
metallic  lead,  and  antimony  oxide  do  not  impart  any  colour  to  glass. 

Ferric  oxide,  known  commercially  as  blood-stone,  ochre,  or  red  chalk,  is  also  used  to 
impart  a  red  colour.  Yellow  and  topaz-yellow  are  obtained  by  means  of  potassium 
antimoniate  or  glass  of  antimony,  silver  chloride,  silver  borate,  and  by  silver  sulphide. 
Uranium  oxide  imparts  a  green-yellow.  Blue  is  obtained  from  cobalt  oxide,  more 
seldom  by  means  of  copper  oxide.  Green  results  from  the  addition  of  chromium 
oxide,  copper  oxide,  and  ferrous  oxide.  Violet  is  obtained  from  manganese  oxide 
(braunite)  and  saltpetre  ;  black,  from  a  mixture  of  ferrous  oxide,  copper  oxide,  braunite, 
and  cobaltous  oxide.  A  beautiful  black  results  from  iridium  sesquioxide. 

Alkaline  poly  sulphides  turn  glass  a  fine  red.  Glass  coloured  yellow  with  sulphur  is 
especially  adapted  for  windows,  glass  shades,  &c.,  for  protecting  sensitive  objects  from 
light.  Pelouze  considers  that  the  reason  why  many  glasses  turn  yellow  on  prolonged 
exposure  to  light  is  that  sulphates  present  are  reduced  to  sulphides.  He  observes  that 
selenium  gives  glass  an  orange-red  colour.  Uranium  gives  glass  a  green  or  a  yellow 
colour.  It  is,  like  sulphur,  often  used  where  the  chemically  active  rays  of  light  are  to 
be  excluded.  Reference  is  made  to  the  fluorescent  properties  of  light-green  uranium 
glass.  As  fluorescent  substances  convert  the  chemical  light-waves  into  the  luminous,  it 
is  very  probable  that  the  utility  of  uranium  glass  depends  not  upon  the  optical  characters 
of  yellow  colours,  but  upon  their  transforming  power. 

Venetian  mosaic  glasses  have  been  examined  by  H.  Schwartz.  Their  composition 
was — 


6oo 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


A 

a 

, 

Jl 

g 

"a 

o 

3 

1 

0 

t 

I 

0 

p 

£ 

1 

fi 

i 

i 

1 

« 

& 

E 
o 

m 

' 

3 
P< 

6"° 

Si02 

Sb205 

5174 
7-9I 

48-80 
13-47 

46-95 
1-42 

52-68 

62-48 

58-00 
S'47 

29-20 
4-00 

57'20 
3-55 

52-08 
3-I5 

52^0 

52-20 

As20. 

9-96 

7-84 

— 

2-33 

i;95 

0-66 

4^9 

2-35 

0-56 

PbO 

I9-94 

9-99 

18-98 

16-52 

9-86 

674 

5'95 

9'53 

4-04 

5  '37 

Cu2O 

— 

— 

— 

— 

— 

— 

— 

2-25 

O'22 



— 

CuO 

— 

— 

— 

— 

— 

— 

— 

(2-51) 

— 

O'lO 

0-31 

CoO 

— 

— 

— 

— 

O'2O 

— 

— 

0-51 

0-09 

0-15 

0-36 

Fe,0, 

0-70 

0-70 

0-63 

0-30 

I'49 

0-60 

2-02 

0-90 

0-76 

I  -60 

1-55 

MnO 

0-42 

— 

— 

— 

— 

— 

— 

4'49 

— 

— 

— 

Mn20, 

— 

— 

0-15 

0-15 

— 

trace 

2-91 

(5-02) 

5-28 

11-50 

1  1  '45 

CaO 

4-42 

11-85 

3-80 

4-50 

2-99 

5-20 

1-50 

7-64 

7-61 

7-30 

MgO 

0-91 

1-45 

1-40 

0-81 

— 

0-38 

0-36 

I-J2 

0-86 

0-86 

1-98 

Ka.,0 

2-26 

9-99 

IOT5 

7-85 

9-96 

1-41 

5-26 

9'59 

1-41 

4-90 

Na.0 

I2-83 

13-12 

5-43 

4-69 

1375 

9-29 

9-39 

8-57 

11-89 

8-54 

Au 

— 

— 

trace 

— 

— 

O'lO 

— 



— 

Bo20a  and  loss 

— 

— 

1-29 

2-40 

— 

i-93 

— 

— 

— 

— 

— 

101-13 

100-52 

lOO'OO 

lOO'OO 

98-82 

lOO'OO 

90-90 

98-92 

99-39 

99-17 

100-41 

Physical  Properties  of  Glass. — Glass  is  so  completely  impervious  that  according  to 
Quincke  no  ponderable  quantities  of  carbon  dioxide  or  of  hydrogen  escape  through  it 
even  in  17  years  and  at  pressures  ranging  from  40  to  126  atmospheres.  The  sp. 
gr.  of  alkali  lime-glasses  varies  from  2-4  to  2-6;  that  of  alkali-lead  glasses  from  3-0 
to  3'8,  and  that  of  thallium  glasses  may  reach  5-625.  The  sp.  gr.  is  increased  by 
cooling.  Thus,  according  to  Eiche  flint  glass  after  cooling  has  a  sp.  gr.  of  3-610. 
The  linear  expansion  of  glass  on  heating  from  o°  to  100°  is  0-0007  to  0-0009. 

The  power  of  glass  to  refract  light  seems  to  decrease  where  the  proportion  of  silica 
and  alumina  is  high,  and  to  increase  very  considerably  with  a  rising  percentage  of  lead. 

Glass  is  a  bad  conductor  of  heat  and  electricity,  though  glasses  which  are  rich  in 
alkali,  and  consequently  hygroscopic,  are  not  good  insulators.  A  glass  from  Glasgow, 
distinguished  for  its  insulating  power,  has  the  following  composition : — 

Si02.  K20.  Na2O.  PbO.  CaO.  MgO.  Fes03. 

58-45      ...      9-24      ...      374      ...      28-02       ...      ox>6      ...      0-05       ...      0-47 

In  consequence  of  its  low  conductivity  for  heat,  glass  breaks  readily  if  suddenly 
cooled  or  heated,  especially  if  it  has  been  imperfectly  annealed.  If  too  suddenly 
cooled  the  external  layers  contract  whilst  the  internal  mass  is  still  hot  and  soft,  so 
that  on  further  refrigeration  a  tension  occurs  which  shatters  the  glass  on  the  slightest 
contact,  and  sometimes  apparently  even  without  any  external  cause.  This  is  the  case 
with  the  so-called  glass  tears  and  with  Bolognese  phials,  small  flasks  which  have  been 
cooled  rapidly  and  which  burst  if  scratched  with  a  grain  of  sand. 

Glass  is  flexible  only  in  fine  threads,  so  that  it  can  even  be  felted.  In  larger  pieces 
it  is  always  brittle.  The  statement  that  glass  becomes  flexible  by  prolonged  burial  in 
the  earth  and  resumes  its  brittleness  on  exposure  to  the  air  seems  incredible.  Glass 
is  tolerably  resistant  to  steady  pressure.  Glass  tubes  bear  an  internal  pressure  of  120 
kilos,  per  square  centimetre.  The  resistance  of  glass  globes  is  somewhat  less. 
According  to  other  experiments  the  crushing  strain  of  flint-glass  is  1700  kilos,  and 
the  resistance  to  rupture  180  kilos;  that  of  bottle-glass  is  200  kilos.  A  small  glass 
of  i  millimetre  thickness  of  glass  resisted,  according  to  Cailletet,  an  external  pressure 
of  460  atmospheres,  but  burst  with  an  internal  pressure  of  140  atmospheres. 

Raw  Materials  used  in  Glass  Making. — These  are : — i.  Silica,  viz.,  quartz,  for  very 
pure  glass ;  for  other  kinds  sand  of  varying  quality,  or  pulverised  flint  stones.  For  very 
pure  glass  the  silica  ought  to  be  free,  or  very  nearly  so,  from  iron ;  in  some  cases  the 


SECT,  v.]  GLASS   MANUFACTURE.  601 

ferric  oxide  adhering  to  the  quartz  or  mixed  with  the  sand  is  removed  by  hydro- 
chloric acid;  while  the  sand  is  always  first  ignited,  and  in  some  instances  previously 
washed,  to  remove  clay,  marl,  humus,  &c.  Ordinary  glass  is  made  with  coarser 
materials ;  the  sand  is  not  required  to  be  so  pure,  as  when  it  contains  lime,  chalk,  or 
clay,  it  renders  the  mass  more  fusible. 

2.  Boric  acid  is  sometimes  used  as  a  substitute  for  a  portion  of  the  silica.     It 
increases  the  fusibility  of  the  glass,  imparts  to  it  a  high  polish,  and  prevents  devitrifi- 
cation.    It  is  employed  as  borax  or  as  boro-calcite,  a  native  boric  acid. 

3.  Potassa  and  soda  are  used  in  a  variety  of  forms,  the  former  chiefly  as  potash 
(potassium  carbonate),  or  partly  lixiviated  wood-ash. 

Not  so  large  a  quantity  of  soda  is  required  as  of  potash;  10  parts  of  sodium 
carbonate  correspond  to  13  parts  of  potassium  carbonate.  Recently  the  soda  has  been 
used  in  the  form  of  Glauber's  salt ;  in  this  case,  so  much  carbon  is  added  to  the  siliceous 
earth  and  Glauber's  salt  as  will  reduce  the  sulphuric  acid  of  fehe  sodium  sulphate  to 
sulphurous  acid,  and  the  carbon  to  carbon  monoxide.  The  silicic  acid  then  easily 
decomposes  the  sulphurous  acid  of  the  sulphite.  To  100  parts  of  Glauber's  salt 
(anhydrous)  8  to  9  parts  of  coal  are  measured.  An  excess  of  carbon  is  detrimental, 
as  a  large  quantity  of  sodium  sulphide  is  formed,  which  imparts  a  brown  tint  to 
the  glass. 

4.  The  lime  used  in  glass-manufacture  must  be  free  from  iron.     It  is  generally 
employed  as  marble  or  chalk,  either  raw  or  burnt.     To  100  parts  by  weight  of  sand, 
20  parts  by  weight  of  lime  are  added.     In  the  Bohemian  manufacture  the  lime  is 
employed  as  neutral  calcium  silicate,  Wollastonite,  Si03Ca.     Instead  of  lime,  strontia 
and  baryta  can  be  used,  the  former  as  strontianite  (SrCo3),  the  latter  as  witherite 
(BaC03).     Fluor-spar  (CaFl2)  and  sodium  aluminate  were  at  one  time  used  in  making 
milky  or  semi-opaque  glass. 

5.  Lead  oxide  is  employed   in  most  cases   in  the  form  of   minium  or  peroxide, 
giving  up  some  of  its  oxygen  to  form  a  lower  oxide,  and  purifying  the  glass.     The 
lead  gives  the  glass  a  higher  specific  gravity,  greater  brittleness,  transparency,  and 
polish.     It  must  be  free  from  copper  and  tin  oxides,  the  former  imparting  a  green 
colour,  and  the  latter  an  opacity  to  the  glass.     White-lead  is  as  efficacious  as  red-lead, 
provided  no  heavy -spar  be  present. 

6.  Zinc  oxide  is  always  added  as  zinc- white.    When  the  colour  is  not  of  importance, 
zinc-blende  with  sand  and  Glauber's  salts  may  be  used. 

7.  Bismuth  oxide  is  only  added  in  small  quantities  in  the  preparation  of  glass  for 
optical  instruments.     Bismuth  may  be  employed  either  as  oxide  or  nitrate. 

The  natural  silicates  are  only  employed  alone  in  the  manufacture  of  bottle-glass; 
some  of  the  preceding  additions  are  requisite  in  clear  glass  manufacture. 

Bleaching. — Coloured  glass  as  it  occurs  in  the  first  processes  of  manufacture  may  have 
the  colour  disguised  by  mechanical  mixture  with  white  glass,  or  the  colour  may  be 
discharged  by  chemical  agents.  Such  agents  are  usually — braunite,  arsenious  acid, 
saltpetre,  and  minium  or  red-lead. 

i.  Braunite  Mn02,  has  long  been  used  as  material  for  glass-clearing.  This  oxide 
of  manganese  is,  however,  used  only  in  small  quantities ;  too  much  imparts  a  violet  or 
amethyst-red  colour  to  the  glass ;  while  an  excessive  amount  renders  the  glass  dark- 
coloured  and  opaque.  The  violet-coloured  glass  is  generally  prepared  with  manganese 
silicate  by  the  addition  of  braunite  to  colourless  glass.  The  action  of  braunite  in 
clearing  glass  or  rendering  it  colourless  has  been  variously  explained.  It  may  be 
considered  that  there  arises  in  the  molten  glass  the  colours  complementary  to  white, 
that  is,  the  green  from  iron  silicate  and  the  violet  from  manganese  silicate.  This 
view  is  supported  by  the  experiments  of  Kb'rner,  who  obtained  a  colourless  glass 
from  a  mixture  of  red  and  violet  glasses;  and  further  by  those  of  Luckow,  who 


602 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


obtained  a  colourless  glass  by  the  melting  together  of  a  glass  strongly  tinted  red 
by  manganous  oxide  with  copper  oxide.  The  glass-blowers  of  the  Bavarian  Forest 
assert  that  a  rose-red  quartz  there  found  is  equalled  by  no  other  quartz  in  the 
production  of  the  best  crystal  or  clear  glass.  Von  Fuchs  says  that  this  quartz 
contains  i  to  1*5  per  cent,  of  titanium  oxide,  which,  similarly  to  Braunite,  effects 
the  chromatic  neutralisation.  Kohn  employs  for  this  purpose  nickel  or  antimony 
oxide.  Zinc  oxide  has  lately  been  employed  to  remove  or  mask  the  green  colour  of  glass, 
also  imparting  a  higher  polish.  2.  Arsenious  acid  effects  the  removal  of  colour  by 
chemical  means  only  from  glass  containing  carbon  or  iron  silicate  :  in  glass  containing 
carbon — 

Arsenious  acid,  As203 

Carbon  30 

in  glass  containing  ferrous  oxide : — 
Ferrous  oxide,  6FeO 
Arsenious  acid,  As203 


give 


give 


j     Arsenic,  As2, 
(Carbon  monoxide,  3CO; 

( Ferric  oxide,  3FesO3, 


(Arsenic,  As2. 

The  arsenious  acid  is  reduced  by  the  carbon  and  ferrous  oxide  at  a  dull  red  heat, 
while  the  arsenic  is  volatilised. 

3.  Saltpetre  is  added  chiefly  as  Chili-saltpetre  or  sodium  nitrate.     In  the  manu- 
facture of  lead-glass  (flint-glass)  lead  nitrate  is  substituted  for  the  sodium  nitrate. 
Barium   nitrate   has  recently   been  employed  to  discharge   the  colour  of  glass;   its 
action  is  similar  to  that  of  arsenious  acid. 

4.  That   minium   serves   to   render    glass    colourless    has    already    been    noted. 
Chambland  states  that  glass  may  be  whitened  by  forcing  through  it  while  molten  a 
stream  of  air. 

Utilisation  of  Refuse  Glass. — The  materials  of  glass  manufacture  are  never  melted 
alone,  but  always  with  nearly  the  third  part  of  prepared  or  finished  glass.  For  this 
purpose,  pieces  of  broken  glass,  flaw  glass,  the  hearth  droppings,  and  the  glass  remain- 
ing adherent  to  the  blowers'  pipes  may  be  utilised — serving  a  purpose  in  the  manufac- 
ture of  glass  similar  to  the  rags  in  paper-making.  Thus  there  is  only  a  very  small  loss 
of  materials.  At  each  re-melting,  however,  a  portion  of  the  alkali  of  the  fragmentary 
glass  is  volatilised,  and  must  be  replaced  by  the  addition  of  an  alkaline  salt. 

A  proportion  of  old  broken  glass,  known  in  the  trade  as  "  cullet,"  is  added  to  tfie 
materials  for  glass-making,  sometimes  to  the  extent  of  one-third. 

Melting  Vessels. — The  vessels  in  which  the  glass  is  melted  are  placed  immediately  upon 
Fig.  402.  Fig.  403.  Fig.  404. 


Fig.  405. 


the  hearth,  and  are  made  of  difficultly-fusible  clay  and  powdered  old  broken  melting-pots. 
They  are  usually  0-6  metre  in  height,  the  walls  being  9  to  12  centimetres  thick.     They 


SECT.   V.] 


GLASS   MANUFACTURE. 


603 


are  dried  in  a  temperature  of  12°  to  15°,  and  then  placed  in  a  chamber  heated  to  30°  to 
40°.  After  remaining  about  a  month,  the  vessel  is  put  into  the  tempering  or  annealing 
oven,  heated  to  50° ;  it  is  next  removed  to  the  ordinary  melting-oven,  and  gradually 
heated  to  the  melting-point  of  glass,  at  which  it  remains  for  three  to  four  hours.  When 
a  new  pot  is  first  used  for  glass-melting,  the  alkaline  constituents  of  the  glass  act  upon 
the  clay,  forming  a  rich  clay  glaze  or  glass,  which,  if  allowed  to  mix  with  the  ordinary 
glass,  would  be  highly  detrimental.  Consequently  broken  glass  and  refuse  are  first 
melted  in  the  vessel,  and  the  glaze  imparted,  termed  technically  the  lining,  is  a  sufficient 
protection  to  the  glass  in  after-practice.  The  shape  of  the  melting  vessels  varies.  For 
melting  with  wood  or  gas  the  conical  form,  Fig.  402,  is  employed.  When  coal  is  used 
as  fuel,  the  vessel  takes  the  covered  form,  Fig.  403.  Fig.  404  represents  a  rather 
peculiar  form ;  the  glass  coristi tuents  are  melted  in  A,  the  clear  molten  glass  passing  by 
the  aperture  in  the  central  wall  into  B.  The  glass  in  B  is  thus  always  free  from  glass-gall 
or  impurities,  which  remain  behind  in  A.  In  the  manufacture  of  looking-glasses,  large 
quadrangular  vessels,  Fig.  405,  are  employed  for  refining  purposes. 

The  Glass-furnace. — The  glass-ovens  are  respectively: — i.  The  melting-oven.  2. 
The  tempering-  or  annealing-ovens,  used  in  the  after-manufacture.  The  melting-oven 
can  only  be  made  of  fire-proof  clay.  It  is  built  of  a  mixture  of  white  clay  and  burnt 
clay  of  the  same  kind.  Ordinary  mortar  and  cements  are  useless  for  this  purpose,  on 
account  of  their  fusibility;  therefore  the  same  clay  as  is  used  for  building  is  also 
used  for  binding.  The  oven  must  be  built  on  dry  ground ;  if  built  on  damp  ground 
it  is  difficult  to  maintain  the  lower  parts  at  a  constant  heat,  requiring  a  larger  supply 
of  fuel.  The  arch  is  closed  with  a  single  piece  of  fire-proof  clay,  weighing  800  to 
1000  cwts.  After  building,  the  oven  is  dried  for  four  to  six  months  at  a  temperature 

Fig.  406. 


of  12°  to  15°.  A  low  fire  is  then  lighted,  and  the  temperature  gradually  increased  for 
about  a  month  until  the  oven  is  fit  for  actual  work.  The  arch  is  further  covered 
with  massive  backstones,  and  these  again  are  covered  to  a  thickness  of  5  to  6  inches 
with  a  lime-mortar.  When  much  in  use,  and  if  not  built  of  very  good  clay,  an  oven  will 
not  remain  in  working  order  for  longer  than  i^  to  if  year  ;  but  if  fire-clay  is  used,  and 
only  easily-fusible  lead-glass  is  manufactured,  the  oven  may  last  for  four  to  five  years. 
The  oven  contains  six  or  eight  to  ten  melting-pots,  which  must  all  be  raised  to  the 
same  temperature.  Further,  the  melting-pot  is  placed  over  half  the  fire-room.  The 
annexed  woodcut,  Fig.  406,  is  a  ground  plan  of  a  complete  oven.  Fig.  407  is  a  sec- 


604 


CHEMICAL  TECHNOLOGY. 


[SECT,  v 


tion  showing  the  melting-ovens  and  work-holes ;  Fig.  408  a  vertical  section  through 
the  length  of  the  oven  ;  Fig.  409  a  vertical  section  of  the  breadth.  In  the  ground 
plan,  Fig.  406,  o  o  is  the  flue ;  c  c  c  are  the  melting-pots ;  n  n,  pots  containing  glass 
in  another  stage  of  preparation ;  d  d  d,  the  work-holes  ;  b  b,  the  banks  ;  i  i,  warm- 
Fig.  407. 


ing  and  cooling  ovens ;  h  h,  tempering  ovens ;  e  e,  the  breast-walls ;  ff,  the  splint 
walls ;  1 1  are  small  hearths  to  increase  the  heat  in  the  tempering-oven  when 
repaired.  In  Fig.  407  I  is  the  flue ;  y  y  are  blocks  of  stone  bearing  the  wooden 
frame-work,  z  z,  on  which  the  wood  used  as  fuel  is  placed  to  dry.  Fig.  408  shows 
the  bank,  ff,  on  which  the  melting-pots,  h  h  h,  stand ;  over  these  pots  are  the  work- 


holes  ;  n  n  are  the  side  chambers.  In  Fig.  409,  b  b  is  the  key-stone ;  c  d  are  the  banks ; 
g  the  flue,  although  in  most  glass-ovens  there  are  no  flues.  The  flame  from  the  fuel 
burning  in  both  grates,  m  m,  Fig.  408,  after  heating  the  melting-oven,  passes  by  the 
tempering-rooms,  and  finally  to  the  chimney-stalk. 

Siemens'  gas-oven  has  lately  found  extensive  use.  At  the  Paris  International 
Exhibition  of  1867  this  oven  obtained  the  gold  medal.  It  consists  of  two  parts,  the 
generator,  Fig.  410,  and  the  melting-oven,  Fig.  411.  These  parts  are  separate,  and 
can  be  30  or  more  metres  from  each  other,  being  connected  by  a  large  gas-pipe.  The 
fuel,  brown  coal,  turf,  stone  coal,  or  wood,  is  placed  in  a  generator  at  A,  Fig.  410, 
and  falls  on  the  sloping  grid,  0.  The  gas,  a  mixture  of  carbonic  oxide  and  nitrogen, 
ascends  at  a  temperature  of  150°  to  200°,  and  flows  out  of  the  generator  by  a  large 


SECT.    V.J 


GLASS  MANUFACTURE. 


605 


pipe,  F,  4  to  5  metres  in  height,  and  is  conveyed  thence  by  a  horizontal  pipe  to  the 
melting  oven.  The  upper  chambers  of  the  melting-oven  are  similar  to  those  of  the 
usual  ovens.  P  P  are  the  melting-pots.  The  gas  first  passes  into  the  first  system 


Fig.  409. 


of  regenerators,  the  stones  of 
which  are  raised  to  a  red 
heat,  and  passes  thence  to 
the  melting-room,  where  it 
meets  with  air  heated  in  like 
manner.  The  products  of 
combustion  then  pass  to  the 
second  regenerating  system, 
the  stones  of  which  are  cold 
until  heated  by  the  passing 
gases.  The  waste  gas  is  finally 
conducted  to  the  chimney- 
stalk.  When  stone-coal  is 
used  in  the  generator,  lead- 
glass  may  be  melted  in  the 
oven  in  open  vessels  without 
reduction.  The  saving  of  fuel 
in  comparison  with  the  old 
system  is  about  30  to  50 
per  cent. 

For  manufacturing  bot- 
tles, &c.,  on  the  large  scale, 
the  continuous  glass-melting 
tank  of  Siemens  (Figs.  74 
to  76,  pp.  67,  68)  has  proved 
satisfactory.  The  mixture, 
as  it  is  introduced  at  c, 
sinks  to  the  bottom  as  it 
melts,  and  thereby  drives 
upwards  another  portion  of 
glass,  which  has  become 
stiffer  by  cooling  at  the 
bottom  and  in  consequence 
specifically  lighter.  This 
portion,  again,  after  being 
exposed  for  a  time  to  the 
heat  of  the  surface  and 
thoroughly  fused,  becomes 
specifically  heavier  than 
the  subjacent  masses,  and 
must  consequently  descend. 
This  behaviour  of  the  glass, 
determined  by  the  differ- 
ences in  specific  gravity, 
in  conjunction  with  the  hy- 
drostatic pressure  exerted 

by  the  glass-makers  standing  on  the  stage,  M,  occasions  an  undulatory  movement  of 
the  glass  towards  the  work-places  in  the  direction  of  the  arrows.  This  ascending 
and  descending  movement  and  continuous  progress  cause  the  glass  to  be  thoroughly 


Fig.  411. 
Section  I.-II. 


6o6 


CHEMICAL  TECHNOLOGY. 


melted  through,  so  that  the  particles  of  glass  are  thoroughly  purified  if  they  come  to 
be  worked.  As  the  floating  fenders  dip  rather  deep  into  the  mass,  the  glass  must 
sink  almost  to  the  bottom,  and  consequently  devitrification  is  avoided.  The  generator- 
gases  and  the  air  issue  separately  through  the  channels,  y  and  I,  the  flame  strikes  across 
through  the  furnace,  the  products  of  combustion  escape  through  the  opposite  channels 
to  the  heat  accumulators,  R,  and  arrive  in  the  chimney  through  the  channels,  x.  By 
this  arrangement  of  the  channels,  g  and  I,  the  glass  in  the  free  space  of  the  tank  before 
the  fenders  receives  the  greatest  heat. 

The  tank-furnaces,  Figs.  410  and  411,  which  F.  Siemens  uses  in  the  glass-works 
at  Neusattel-Ellbogen,  approximate  to  the  ordinary  glass-furnace  for  melting-pots, 
as  it  can  be  used  for  the  most  different  kinds  of  glass.  The  tank  is  divided  into 
four  compartments  by  bridges  placed  crossways.  The  raw  materials,  introduced 
separately,  are  mixed  at  G,  and  from  here  passed  into  the  furnace  through  the 
apertures,  n.  The  regenerators,  JR,  forming  the  base  of  the  furnace,  2  metres 
broad  and  2^75  long  (between  which  is  the  access- vault,  T),  are  connected  by  the 
channels,  s,  with  the  lateral  channels,  &\  from  which  gas  and  air  arrive  into  the  furnace 
through  the  channels,  g  and  L  The  round  tank  is  divided  into  four  compartments 
for  four  different  kinds  of  glass,  by  the  bridges,  z,  which  intersect  each  other  at  right 
angles. 

The  refrigerations  of  these  bridges  run  into  the  common  ventilating  chimney,  V, 
which  is  carried  through  the  vault  of  the  furnace.  Its  lower  part  is  divided  by  an 
iron  cross,  about  i  metre  high,  in  such  a  manner  that  the  ventilation  of  each  bridge  is 
kept  apart  from  the  others  to  above  the  level  of  the  glass.  This  is  to  prevent  mutual 

Fig.  412. 

Section  A.  B. 


<£... 


•  v  •"i"-1:^-'^^:^'^--: .^ 


Explanation  of  Term. 
Einlegtbiikne        ....     Introductory  Stage. 

disturbance  in  the  aeration  of  the  several  bridges.  Thes  bottom  and  the  side  walls  of 
the  tank  are  provided  with  air -refrigerators,  e,  which  open  into  the  four  small  chimneys, 
f,  in  such  a  manner  that,  in  case  of  accident,  one  compartment  may  not  affect  the 
others.  The  air-channels  of  the  bridges  are  separated  by  large  stones  of  correspond- 
ing shape,  which  rest  upon  a  number  of  small  pillars. 

Before  each  of  the  28  work-places,  a,  there  floats  in  the  half -melted  mass  a  refining- 
boat,  which  renders  continuous  working  possible.     Every  working  place  is  occupied  by 


SECT.    V.] 


GLASS  MANUFACTURE. 


607 


a  workman  and  an  assistant,  so  that  the  work  is  carried  on  in  twenty  working  hours 
daily  in  two  1 2-hour  shifts.  Each  work-place  produces  hourly  50  bottles. 

Latterly,  F.  Siemens  proceeds  on  the  supposition  that  large  spaces  are  necessary 
for  producing  a  great  heat.  Hence  he  has  built  a  tank-furnace  which,  as  shown  in 
Figs.  412-414,  has  a  very  lofty  vault. 

The  furnace  of  Boetius  is  most  widely  used  in  Germany  next  to  that  of  Siemens. 

Glass-melting. — At  the  temperature  of  a  glass  furnace,  1200°  to  1250°,  the  melted 
glass  is  a  thin  liquid,  like  a  thick  solution  of  sugar.  This  condition  is  very  important 
for  the  purification  of  the  glass,  since  all  substances  which  cannot  dissolve  in  the  mass 
separate  out,  either  on  the  surface  or  at  the  bottom.  In  this  state,  further,  glass  can 
be  cast.  At  a  red  heat  glass  becomes  very  extensible  and  flexible,  conditions  on  which 
the  mechanical  treatment  of  glass  depends.  Two  pieces  of  red-hot  glass  can  be  made 
to  unite  by  being  simply  pressed  together.  In  spinning  glass  the  material  is  brought 
to  its  utmost  degree  of  extensibility,  so  that  it  can  be  manipulated  upon  a  wheel. 
The  glass  thread  of  Brunfaut's,  at  Vienna,  which  is  now  used  for  producing  wadding, 
feathers,  veils,  nets,  &e.,  has,  according  to  the  measurements  of  Fr.  Kick,  a  diameter  of 
o'oo6  to  o'oi2  millimetre.  It  is,  therefore,  rather  finer  than  the  single  cocoon  thread. 

Not  until  the  furnace  has  reached  its  highest  temperature  is  the  cullet  and  then  the 
mixture  put  into  the  crucibles,  an  operation  performed  in  three  or  four  lots. 

Fig.  413- 

Section  C.  D. 


Melting  the  Glass  Material. — When  the  temperature  of  the  melting-oven  has  reached 
the  required  degree,  the  material  first  frits  together  and  is  then  melted.  The  oven 
must  be  heated  equably  throughout  At  the  melting-point  the  siliceous  earth  combines 
with  the  potash,  soda,  lime,  alumina,  lead  oxide,  &c.,  to  form  glass.  The  substances 
not  taken  up  form  a  scum,  known  as  glass-gall,  upon  the  molten  glass,  which  is  removed 
by  the  aid  of  iron  shovels.  This  scum  is  generally  composed  of  sodium  sulphate  and 
chlorides  of  the  alkalies.  The  progress  of  the  melting  process  is  from  time  to  time 
ascertained  by  removing  a  sample  of  the  glass  by  the  help  of  an  iron  rod  terminating  in 
a  flat  disc — in  fact,  a  large  flat  spoon. 

Clear-melting. — When  the  mass  is  well  molten  it  is  "cleared" — that  is,  maintained 
for  some  time  at  such  a  temperature  that  the  glass  remains  in  a  thinly  fluid  condition. 
During  this  period  the  uncombined  substances  settle  to  the  bottom  of  the  melting  vessel, 
the  air-bubbles  disappear,  and  the  glass-gall  still  remaining  is  volatilised  or  separated. 
At  the  commencement  of  the  melting  the  disengagement  of  the  gases  from  the  molten 


6o8 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


mass  causes  an  advantageous  agitation,  by  which  the  several  constituents  of  unequal 
specific  weight  and  different  composition  become  well  mixed.  After  the  disengagement 
of  the  gases  the  lower  part  of  the  melting  vessel  is  at  a  lower  temperature  than 
the  upper  part  ;  consequently  the  molten  glass  is  well  stirred  with  the  iron  ladles  or 


Fig.  414. 
Section  E.  F. 


"  poles."  Lastly,  a  piece  of  either  arsenious  acid,  damp  wood,  raw  turnip,  or  any 
other  water  -containing  substance,  is  introduced  to  the  bottom  of  the  vessel  on  an 
iron  rod,  the  end  in  view  being  the  violent  agitation  of  the  molten  glass  by  the  steam 
evolved. 

If  the  mixture  consists  of  soda,  calcium  carbonate  and  silica,  the  process  is  — 


NaC0 


=  Na2Ca(Si03)2  +  2C02. 


But  if  salt-cake  is  employed  — 

2Na2S04  +  C  +  2SiO2  =  2Na2Si03  +  C02+  2S02. 

In  the  course  of  melting  the  sodium  silicate  is  transformed  with  the  calcium  carbonate 
and  the  silica  as  follows  :—  Na;!SiO3  +  CaC03  +  Si02  =  Na2Ca(Si03)2  +  C03. 

Cold-stoking.  —  After  the  completion  of  the  clearing  follows  the  cold-stoking  —  that  is, 
the  lowering  the  temperature  of  the  oven  till  the  glass  attains  a  tough  fluid  consistency 
requisite  before  it  can  be  blown.  The  glass  remains  at  this  temperature,  700°  to  800° 
C.,  during  the  rest  of  the  manufacture. 

The  length  of  the  several  processes  is  as  follows  :  — 


Melting 
Clearing 
Blowing 


10  to  12  hours. 
4  to    6     „ 

IO  tO  12       ,. 


so  that  five  to  six  meltings  can  be  effected  in  a  week. 

Defects  in  Glass. — It   is  extremely  difficult  to  prepare  glass  perfectly  free  from 
blemish.     The   principal   defects   are — streaking,  threading,   running  unequally,   or 


SECT,  v.]  GLASS  MANUFACTURE.  609, 

dropping,  stoning,  blistering,  and  knotting.  Streaking  follows  from  heating  the  glass 
unequally,  another  consequence  of  which  is  the  threading  or  the  formation  of  the  strise, 
by  glazing,  into  coloured  threads,  generally  green.  By  dropping  is  understood  the 
lumps  or  globules  formed  in  the  glass  by  the  glazing  of  the  clay  cover  of  the  melting 
vessel,  and  its  combination  with  the  volatilised  alkalies,  the  crude  glass  thus  formed  on 
the  cover  dropping  into  the  molten  glass  contained  in  the  vessel.  Blistering  is  a  common 
result  of  the  imperfect  clearing  of  the  glass  from  air  bubbles.  Lastly,  knotting,  another 
common  defect,  results  from  uncombined  grains  of  sand  taken  up  in  the  glass ;  the 
small  particles  of  the  oven  and  melting  vessel  detached  during  the  melting  similarly 
giving  rise  to  stoning.  Other  defects,  such  as  the  imperfect  combination  of  the  mate- 
rials, arising  from  carelessness  or  inability  of  the  workman,  need  not  here  be  noticed. 

Various  Kinds  of  Glass. — Glass  is  divided  according  to  its  composition  or  method 
of  manufacture  into  — 

I.  Glass  free  from  Lead. 

A.  Plate  glass,      a.  Window  glass : — 

a.  Boiled  glass. 
/3.  Crown  glass. 
b.  Plate  glass  : — 

a.  Blown  plate  glass. 
/3.  Cast  plate  glass. 

B.  Bottle  glass. 

a.  Ordinary  bottle  glass. 

b.  Medicine  and  perfumery  glass. 

c.  Glass  for  goblets,  drinking  glasses.  &c. 

d.  Water  pipes  and  gas  tubes. 

e.  Retort  glass. 

C.  Pressed  or  stamped  glass. 

D.  Water  glass. 

II.  Glass  containing  Lead  (Flint  Glass). 

A.  Crystal  glass. 

B.  Glass  for  optical  purposes. 

C.  Enamel. 

D.  Strass. 

III.  Coloured  and  Stained  Glass. 

Plate  and  Window  Glass. — Glass  melted  in  muffles  or  vessels  is  manufactured  as- 
plate  glass  or  as  crown  glass.  Plate  glass,  as  its  name  implies,  is  formed  in  large  or 
small  plates ;  window  glass  is  generally  either  ordinary  bottle  glass  or  a  finer  glass  of  a 
whiter  colour.  Recently,  thick  has  taken  the  place  of  thin  glass  for  windows,  but  the 
colour  is  hereby  considerably  increased.  That  window  glass  should  be  prepared  cheaply 
is  an  essential  point ;  consequently  crude  materials  are  employed — crude  potash  and 
soda,  wood  ash,  salt  cake,  ordinary  sand,  and  broken  glass  from  the  warehouses, 
&c.  Plate  or  window  glass  is  generally  composed  of  100  parts  sand,  30  to  40  parts 
crude  calcined  soda,  30  to  40  parts  calcium  carbonate.  Instead  of  the  soda  may 
be  substituted  an  equivalent  quantity  of  salt  cake.  Benrath  (1869)  found  in 
several  kinds  of  plate  glass  the  following  constituents : — 

Silicic  acid          .        .        .  7071  ..  71*56  ...  73'ii 

Soda i3'35  •••  I2'97  •••  13*00 

Lime 13-58  ...  13-27  ...  13-24 

Alumina  and  ferric  oxide    .        .  1*92  ...  1*29  ...  0*83 

99-56  ...  99'O9  •••          100-18 

2  Q 


6io 


CHEMICAL   TECHNOLOGY. 


[SECT.  v. 


Tools. — The  tools  ordinarily  used  by  the  glassblower  in  the  preparation  of  plate  and 
crown  glass  are  the  following  : — 

The  pipe  or  blow-tube,  Fig.  415,  is  an  iron  pipe  1*5  to  i-8  metre  in  length,  3 
to  5  centimetres  thick,  and  i  centimetre  interior  diameter,  a  is  the  mouth-piece,  made 


Fig.  415. 


3ig.  416. 


fig.  417. 


Fig.  418. 


Fig.  4 1 9. 


so  as  to  turn  easily  between  the  lips,  c  is  a  hollow  handle  from  0-3  to  0-5  metre  in 
length.  6  is  the  part  attached  to  the  glass. 

The  handle  or  hand  irons  are  rods  i  to  i  "3  metre  in  length,  used  to  transport 
the  hot  vessels,  &c.  The  marbel,  Figs.  416  and  417,  is  a  piece  of  wood  with  semi- 
globular  indentations,  which  serve  as  matrices  for  the  glass  to  be  taken  up  on  the 
blower's  pipe.  The  whip,  Fig.  41 8,  is  a  block  of  wood,  hollowed  so  as  to  form  a  long  neck 
to  the  soft  semi-molten  glass ;  it  is  also  used  to  remove  the  glass  from  the  pipe. 
Fig.  419  is  the  shears  used  for  trimming  the  molten  glass,  and  to  cut  openings  during 
the  blowing  of  various  articles. 

Window  glass  is  manufactured  as  crown  glass  or  as  rolled  glass. 

Crown  Glass. — Crown  glass  is  the  oldest  kind  of  window  glass.  It  is  formed  in  the 
manufacture  as  a  disc  of  glass,  generally  of  about  6  inches  in  radius  from  the  periphery 
to  the  centre  knot  left  by  the  glassblower's  pipe,  technically  termed  the  bull's-eye. 
The  largest  discs  are  scarcely  64  to  66  inches,  from  which  a  square  plate  of  22  inches 
only  can  be  cut,  the  bull's-eye  interfering  with  the  cutting  of  a  larger  size.  In  the 
preparation  of  this  glass  three  workmen  are  employed  ;  the  first  takes  so  much  molten 
glass  on  the  end  of  a  pipe  as  will  serve  for  a  single  disc,  and  passes  pipe  and  glass  to  the 
second  workman,  the  blower.  He  blows  the  glass  into  a  large  globe  or  ball,  which, 
when  finished,  he  hands  to  a  third  workman,  the  finisher,  who  opens  the  globe  and 
forms  the  sheet  or  pane.  The  labour  is  divided  in  detail  in  the  following  manner  :— 
The  first  workman  receives  the  warm  pipe,  thrusts  it  into  the  vessel  of  molten  glass,  and 
turns  it  steadily  round  until  he  has  collected  upon  the  end  a  knob  of  glass  of  sufficient 
size.  The  weight  of  this  knob  is  generally  10  to  14  Ibs.  The  first  workman  by  means 
of  the  marbel  imparts  somewhat  of  a  spherical  form  to  the  solid  glass  ball,  which  is 
now  taken  in  hand  by  the  blower,  who  by  turning  and  shifting  the  glass  about,  at  the 
same  time  blowing  through  the  tube,  perfects  the  hollow  spheroid.  The  glass  has  by 
this  time  cooled  considerably,  and  with  the  pipe  is  therefore  returned  to  the  oven,  the 
tube  of  the  pipe  being  fastened  in  a  fork  or  hook  in  the  ceiling  of  the  oven.  As  the 
globe  of  glass  is  gradually  heated  the  weight  of  the  rod  causes  it  to  flatten  out,  and  it  is 
removed  by  the  finisher  as  a  disc  of  nearly  molten  glass.  He  places  the  tube  in  the 
cavity  of  the  whip,  and  by  a  series  of  dexterous  movements  perfects  the  shape,  enlarges 
the  disc  if  required,  or  in  some  cases  makes  a  larger  disc  by  removing  the  partially 


:SECT.    V.] 


GLASS   MANUFACTURE. 


611 


flattened  sphere  from  the  oven,  opening  the  bottom  with  a  maul  or  iron  rod,  and  causing 
the  glass  to  take  the  form  of  a  disc  by  means  of  the  centrifugal  force  resulting  from 
a  rapid  rotary  motion  of  the  rod.  Finally,  the  discs  are  separated  from  the  pipe  by  the 
help  of  a  drop  of  cold  water,  and  are  next  placed  in  an  annealing  oven,  to  the  number 
of  150  to  200,  to  cool.  The  finished  plates  are  cut  to  the  required  size  ;  the  centres  or 
bull's-eyes  serve  for  the  making  of  strass  and  for  other  purposes. 

Sheet  Glass,  or  Cylinder  Glass. — Rolled  or  sheet  glass  is  made  by  cutting  a  glass 
cylinder  or  roll  throughout  its  length,  and  beating  or  rolling  it  out  flat  on  a  table.  It 
is  for  this  reason  termed  sheet  glass.  Usually  this  sheet  glass  is  used  for  ground  glass, 
and  is  further  separated  into  ordinary  sheet  or  roll  glass  and  fine  sheet  glass,  the  latter 
having  larger  dimensions. 

The  preparation  of  sheet  glass  is  one  of  the  most  difficult  processes  of  glass  manu- 
facture ;  it  may  be  considered  as  consisting  of  two  operations — 

1 .  The  blowing  of  the  roll,  or  cylinder ;  and 

2.  The  flattening. 

After  the  molten  glass  has  cleared,  and  attained  the  barely  fluid  consistency  before 
mentioned,  the  workman  inserts  his  pipe  into  the  mass,  and  by  turning  manages  to 
accumulate  on  it  a  globe  of 
glass,  during  the  time  blowing 
into  the  tube  to  keep  it  clear 
of  the  molten  glass.  The 
glass  now  takes  the  form  «, 
Fig.  420.  By  continued  mani- 
pulation in  the  marbel,  and 
by  blowing,  the  enlarged  forms, 
b  and  c,  and  finally  d,  are 
obtained.  The  glass  has  by 
this  time  cooled,  and  is  taken 
to  the  oven  to  be  re-heated. 
When  this  is  effected,  the  work- 
man, by  means  of  his  tools, 
by  a  continued  rotation  of 
glass,  and  by  blowing,  brings 
the  globe  to  the  shape  repre- 
sented by  /.  He  then  opens 
out  the  bottom  of  this  form 
with  a  maul-stick,  and  obtains 
the  cylinder  e,  which  is  sepa- 
rated from  the  pipe  by  drop- 
ping a  little  cold  water  upon 
the  neck,  o,  joining  the  two. 
The  removal  of  this  neck  is 
next  effected  by  means  of  a 
red-hot  iron  rod,  which  also 
serves  to  open  the  cylinder 
throughout  its  length  as  shown 
by  A. 

After  a  great  number  of  these  cylinders  have  been  blown,  the  operation  being 
generally  continued  for  three  days,  the  opening  into  plates  is  commenced.  The  cylinders 
are  placed  in  an  oven  termed  the  plate-oven,  shown  in  ground  plan  in  Fig.  421,  con- 
sisting of  two  chambers,  one  the  heating  room,  C,  and  the  other  the  tempering  or 


612 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


annealing  room,  D.  in  the  passage  B,  the  heated  glass  rolls  or  cylinders,  a  a  a,  are 
suspended  upon  two  iron  rods,  where  they  are  maintained  at  a  certain  heat.  The  most 
important  part  of  the  plate-oven  is  the  platten,  C,  made  of  a  well-rammed  fire-clay. 
A  similar  plate,  D,  is  placed  in  the  annealing  room.  When  sufficiently  heated,  the 
cylinders  are  brought  to  the  flattening  table,  c,  Fig.  422,  where  they  are  speedily  opened 

Fig.  421. 


Fig.  422. 


out  m  the  manner  shown  in  the  woodcut.  A  workman  stationed  at  d,  Fig.  421,  receives 
the  Hat  panes  of  glass,  and  leans  them  against  the  iron  bars,  s  s,  in  the  annealing  room, 
whence;  having  gradually  cooled  during  four  or  five  days,  tney  are  removed  to  be  sorted 
and  packed. 

Plate  Glass. — Plate  glass  is  either  blown  or  cast.  The  manufacture  is  very  similar 
to  that  of  table  glass  just  described.  The  materials  are  in  great  part  the  same  as  those 
employed  in  the  manufacture  of  fine  white  glass.  This  branch  of  glass  manufacture  is 
most  strikingly  illustrative  of  the  rapid  growth  of  the  industry  during  the  last  ten  or 
twenty  years.  Formerly  plate  glass  was  esteemed  an  article  of  luxury,  whereas  now 
it  is  that  most  generally  used  for  workshop  windows,  carriages,  showrooms,  &c.,  and 
for  windows  of  private  residences.  It  far  surpasses  in  transparency  and  elegance  the 
small  panes  formerly  used.  By  the  Glass  Jury  of  the  International  Exhibition  of 
Paris  of  1867,  it  was  surmised  that  before  ten  years  had  elapsed  plate  glass  would  be 
that  most  generally  in  the  market.  The  blowing  of  plate  glass  is  effected  with  the 
same  tools  as  the  blowing  of  table  glass ;  and  the  cylinder  is  obtained  in  a  similar 
manner.  The  lump  of  glass  taken  by  the  blower  on  his  pipe  from  the  melting  vessel 
weighs  about  45  Ibs.,  from  which  a  plate  of  1-5  metre  in  length  and  i  to  n  metre 
breadth  by  i  to  n  centimetre  thickness  is  obtained.  But  the  chief  method  of 
making  plate  glass  is  by  casting.  Cast  plate  glass  is  always  made  from  pure  materials, 
•and  may  be  considered  as  a  sodium-calcium  glass  free  from  lead.  Potassium-calcium 
glass  is  far  more  expensive,  being  almost  a  colourless  glass.  In  England,  Belgium, 
and  Germany  the  raw  materials  used  in  manufacturing  cast  plate  glass  are — sand, 
limestone,  and  soda,  or  salt  cake. 

Benrath  (1869)  found  in  English  (a)  and  in  German  (£)  plate  glass:— 


Silica         . 

Soda 

Lime          .... 
Alumina  and  oxide  of  iron 


Sp.  gi. 


76-300 

16-550 

6-500 

0-650 

1 00 -000 

2-448 


78750 

13-000 
6-500 
1-750 

lOO'OOO 

2-456 


SECT,  v.]  GLASS  MANUFACTURE.  613 

The  following  description  of  casting  the  plates  is  mainly  founded  upon  the  method 
pursued  at  St.  Gobain  and  Ravenhead.  The  manufacture  is  included  in — 

1.  The  melting  and  clearing. 

2.  The  casting  and  cooling. 

3.  The  polishing  ;  including — 
a.  The  rough  polishing. 

/3.  The  fine  polishing. 

y.   Finishing. 

The  Melting  and  Clearing. — The  melting  and  clearing  vessels  are  of  very  different 
form  and  size.  The  first  is  a  conical  vessel  surmounted  by  a  cupola  having  three 
apertures,  making  an  angle  of  120°  with  each  other.  The  clearing  pans  are  small, 
wide,  and  low  vessels.  These  vessels  are  never  in  the  same  oven.  After  the  materials 
are  melted,  which  is  effected  in  sixteen  to  eighteen  hours,  the  molten  mass  is  poured  into 
the  clearing  vessels.  The  impurities  are  then  removed  with  a  large  copper  ladle,  this 
process  occupying  about  six  hours.  During  the  clearing  the  excess  of  soda  is  volatilised. 
When  the  glass  is  sufficiently  cleared  the  casting  commences.  The  vessel  containing 
the  molten  glass  is  taken  up  by  a  crane  and  swung  to  the  casting  table,  this  table 
or  mould  being  on  a  level  with  the 

cooling  or  annealing  oven.    The  casting  Fig.  423. 

table  consists  of  a  large  polished  metal 
plate,  Fig.  423,  in  the  French  works  of 
copper  or  bronze,  4  metres  long,  2*25 
metres  wide,  and  1 1  to  1 8  centimetres 
thick.  The  plate  at  St.  Gobain  weighs 
55,000  Ibs.  and  cost  100,000  francs 
{^4000).  In  England  the  plates  are 
of  cast-iron,  25  centimetres  thick,  5 
metres  in  length,  and  2 '8  metres  wide. 
In  order  that  the  glass  plate  shall  be 
of  equal  thickness,  a  bronze  or  cast- 
iron  roller  passes  over  the  surface  on 
guides  of  the  thickness  required.  The 
metal  plate  is  first  warmed  to  prevent 
the  sudden  cooling  of  the  glass.  The  operation  of  casting  includes— 

a.  The  conveyance  of  the  pan  to  the  table. 

b.  The  cleansing  of  the  plate  and  the  pan. 

c.  The  casting  and  conveyance  of  the  plate  to  the  annealing  room. 

The  cooling  room  has  two  fire-places  and  three  glass  tables.  The  temperature  is  at 
first  that  of  the  glass  plate  introduced.  So  soon  as  three  plates  are  placed  in  the  oven, 
all  the  openings  are  closed,  and  the  glass  left  for  a  day  to  cool.  The  cooled  glass 
plate  is  taken  out  of  the  annealing  oven  to  the  cutting  room,  laid  on  a  cloth-covered 
table,  and  cut  to  size  with  a  diamond. 

Polishing.  —  The  glass  plate  is  cut  into  tablets.  The  under  side  of  the  plate,  where 
it  has  been  in  contact  with  the  table,  is  smooth,  while  the  upper  surface  is  wavy,  and 
requires  to  be  polished.  This  is  effected  by  fastening  the  plate  or  tablet  to  a  bench 
with  plaster-of-Paris,  and  grinding  the  upper  surface  smooth  with  some  sharp  powder ; 
or  another  plate  is  caused  by  machinery  to  move  above  the  former  in  such  a  manner 
that  the  surfaces  of  both  are  ground  smooth.  The  ground  plates  are  then  removed 
to  the  polishing  table,  where  a  similar  process  is  gone  through,  but  with  a  finer 
powder.  Finally,  when  placed  upon  the  finishing  table,  only  the  finest  powder  and 
leathern  pads  are  employed.  By  grinding  and  polishing,  the  glass  sometimes  loses  half 


614  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

its  weight  in  thickness.  Suppose  a  plate-glass  manufactory  to  produce  400,000  square 
feet  of  glass  annually,  there  will  be  with  this  amount  of  glass,  weighing  about  16,000 
cwts.,  a  loss  of  8000  cwts.,  corresponding  to  2700  cwts.  of  calcined  soda,  and  a  money 
value  of  more  than  ^1000. 

/Silvering. — After  polishing,  each  glass  tablet  intended  to  make  a  looking-glass  is 
silvered,  or,  more  correctly,  coated  on  one  side  with  an  amalgam  of  tin.  In  the 
preparation  of  this  amalgam  tinfoil  is  used,  but  it  must  be  beaten  from  the  finest  tin, 
and  possess  a  surface  similar  to  that  of  polished  silver.  The  art  of  silvering  is  simple, 
and  merely  requires  dexterity.  The  glass  plate  having  been  thoroughly  cleansed  from 
all  grease  and  dirt  with  putty  powder  and  wood  ash,  the  workman  proceeds  to  lay  a 
sheet  of  tinfoil  smoothly  upon  the  table,  carefully  pressing  out  with  a  cloth  dabber  all 
wrinkles  and  places  likely  to  form  air  bubbles.  He  spreads  over  it  a  quantity  of 
mercury,  taking  care  that  all  parts  are  equally  covered,  and  then  the  glass  plate  is 
pushed  gently  on  to  the  surface,  commencing  at  one  edge.  A  glass  plate  of  30  to  40 
square  feet  requires  150  to  200  Ibs.  of  mercury,  although  the  amalgam  is  not  so 
thick  as  a  sheet  of  the  finest  paper.  The  glass  is  allowed  to  remain  for  twenty-four 
hours.  It  is  then  removed  to  a  wooden  incline  similar  to  a  reading  desk  to  allow  of 
the  excess  of  mercury  draining  off.  As  the  amalgam  gradually  sets,  the  incline  is 
increased  till  finally  the  plate  reaches  the  perpendicular,  when  the  process  is  finished, 
and  the  mirror  removed  to  the  store  room. 

Silvering  by  Precipitation. — The  former  method  of  coating  the  glass  with  tin- 
amalgam  obtains  its  name  of  silvering  by  analogy  only :  the  true  process  of  silvering  i& 
the  following,  patented  in  1844  by  Mr.  Drayton: — 32  grammes  of  silver  nitrate  are 
dissolved  in  64  grammes  of  water  and  16  grammes  of  liquid  ammonia,  adding  to  the 
filtered  solution  108  grammes  of  spirits  of  wine  of  0*842  sp.  gr.,  and  20  to  30  drops  of  oil 
of  cassia.  Call  this  fluid  No.  i.  Another  fluid  (No.  2)  is  prepared  by  mixing  i  volume 
of  oil  of  cloves  with  3  volumes  of  spirits  of  wine.  The  workman  places  the  glass  plate 
upon  a  table,  carefully  levels  it,  and  floods  it  to  a  depth  of  0*5  to  i  centimetre  with 
fluid  No.  i .  He  then  precipitates  the  silver  by  adding  6  to  1 2  drops  at  a  time  of  fluid 
No.  2  until  the  whole  of  the  surface  is  covered.  For  every  square  foot  of  glass  9  deci- 
grammes of  silver  nitrate  are  required.  Liebig  recommends  an  ammoniacal  solution 
of  fused  silver  nitrate  to  which  450  c.c.  of  soda-lye  of  1*035  sp.  gr.  are  added. 
The  precipitate  thrown  down  is  dissolved  by  means  of  ammonia,  the  volume  being 
increased  to  1450  c.c.,  and  by  water  to  1500  c.c.  This  fluid  is  mixed  shortly  before 
application  with  one-sixth  to  one-eighth  of  its  volume  of  solution  of  sugar  of  milk, 
containing  10  parts  by  weight  to  i  of  sugar  of  milk.  The  glass  is  flooded  with  this 
fluid  to  about  half  an  inch  in  depth ;  reduction  soon  sets  in,  and  the  glass  becomes 
thickly  coated,  i  square  metre  of  glass  plate  requires  2*210  grammes  of  silver.  The 
plate  is  then  dried,  cleaned,  and  polished.  Lowe  employs  silver  nitrate,  starch-sugar, 
and  potash  •  A.  Martin,  silver  nitrate,  ammonia,  and  tartaric  acid. 

Platinising. — According  to  the  researches  of  Dode,  platinum  may  be  used  for  coat- 
ing plate-glass.  In  France,  Creswell  and  Tavernier  have  already  brought  platinised 
mirrors  before  the  public.  Hitherto  platinum  had  been  used  in  ornamenting  porcelain, 
and  the  glass  plates  are  prepared  in  a  similar  manner,  the  metal  being  burnt  in,  as  it 
is  termed.  The  platinum  is  precipitated  from  its  chloride  by  oil  of  lavender,  the 
chloride  being  spread  equally  over  the  glass  with  a  fine-haired  paint-brush.  The 
plate  is  then  placed  in  a  muffle.  Cheapness  is  a  prominent  feature  of  this  process ; 
as  by  it  all  faulty  glasses  can  be  very  easily  repaired,  those  by  the  old  methods  being 
thrown  aside  as  useless.  In  Paris  the  lids  of  boxes  and  fancy  articles  are  largely 
manufactured  from  platinised  glass. 

For  gilding  glass  there  is  employed  a  dilute  solution  of  sodium  aurate,  which  is 
reduced  by  means  of  a  saturated  solution  of  ethylene  in  alcohol. 


SECT.    V.] 


GLASS   MANUFACTURE. 


Bottle  Glass. — Bottle  glass  includes  all  kinds  of  glass  made  into  vessels  for  holding 
fluids.  It  is  made  from  common  green  glass,  from  fine  white  glass,  and  from  crystal 
glass.  Medicine  bottles,  &c.,  are  made  from  common  green  glass ;  tumblers,  or  drinking 
glasses,  from  fine  white  glass ;  and  crystal  glass  is  employed  for  the  same  articles,  but 
selling  at  a  higher  price. 

The  materials  for  ordinary  bottle  glass  are  sand,  potash  or  soda,  basalt,  &c.  For 
medicine  glass  the  materials  must  be  free  from  iron,  and  still  purer  for  articles  of 
white  glass.  In  the  manufacture  of  bottle  glass  no  considerable  amount  of  care  is 
required,  the  desiderata  being  strength  and  sufficient  resistance  to  the  action  of 
ordinary  acids.  The  processes  of  melting  and  annealing  are  conducted  in  the  ordinary 
manner.  The  analyses  of  several  glasses  gave  the  following  results  : — 


Silicic  acid 

Potash 

Soda 

Lime          .         . 

Alumina     . 

Iron  oxide          ; 

Manganese  oxide 


7471 

1574 
877 
0'43) 
0-14  [ 

0'2I  ) 
lOO'OO 

2-47 


74-66 

4-32 

1 1 -01 

9-I3 


lOO'OO 

2-48 


75  "94 


1 00 'GO 

2-47 


74-37 
12-48 

3 '42 
9-02 

071 


lOO'OO 

2-30 


74-26 

14-06 

8-60 

2-52 

0-38 

0-18 


100 -oo 
2-40 


The  details  of  the  several  processes  of  bottle  glass  manufacture  are,  after  the 
making  of  the  rough  shape  out  of  the  tough  fluid  glass,  so  various  that  only  single 
examples  can  be  given.  We  will  select  the  ordinary  wine  bottle.  The  glass  blower, 
taking  some  molten  glass  on  his  pipe,  turns  and  moulds  it  into  the  shape  of  a,  Fig.  424. 
By  continued  blowing  the  enlarged  form,  b,  is  obtained;  this  form,  still  more  enlarged, 
as  at  c,  is  placed  in  the  mould,  d.  The  workman  now  blows  sharply  into  the  incipient 
bottle,  the  glass  filling  out  the  mould  and  producing  the  sharp  curve  of  the  shoulder  of 
the  wine  bottle.  The  rod  or  puntili,  e,  is  now  introduced,  and  a  firm  footing  given  by 
pressing  in  the  bottom  of  the  bottle.  While  the  blower  prepares  a  new  bottle,  the 
assistant  places  that  already  formed  in  the  annealing  oven.  In  the  making  of  flasks 

Fig.  425- 


Fig.  426. 


and  retorts  the  flask  tongs,  Fig.  425,  are  employed,  the  neck  being  allowed  to  remain 
straight,  as  at  a,  Fig.  426,  to  form  a  flask,  or  bent,  as  at  b,  to  make  a  retort.  The 
manufacture  of  a  beaker  will  be  readily  understood  from  Figs.  427  and  428,  A,  Bt  C, 
being  the  method  of  producing  a  globular  body,  and  a,  6,  c,  a  beaker  with  nearly  per- 
pendicular sides.  Glass-tubing  is  drawn  out  as  shown  at  Fig.  429.  Glass  rods  are 
similarly  made,  but  without  blowing. 


6i6 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 

Pressed  and  Cast  Glass. — Pressed  or  cast  glass  comprises  the  many  cheap  glass 
ornaments,  and  indeed,  ornamental  glass-work  of  all  kinds,  now  so  general.  The  tall, 
narrow-mouthed  chimney  ornaments  are  thus  made  by  being  blown  into  engraved  brass 
moulds,  instead  of  into  plain  moulds  as  in  the  case  of  the  bottle.  Cup-shaped  articles 


Fig.  428. 


Fig.  428. 


Fig.  429. 


are  made  with  molten  glass  pressed  between  a  concave  and  convex  surface,  the  surplus 
glass  escaping  at  some  point  purposely  arranged.  As  a  rule,  the  objects  taken  from 
the  moulds  require  but  little  polishing. 

Hardened  Glass. — The  invention  of  hardened  glass  by  De  la  Bastie  (1875)  excited 
a  greater  sensation  than  do  most  novelties,  but  the  sanguine  hopes  entertained  of  its 
usefulness  have  not  been  fulfilled.  The  process  consists  essentially  in  a  rapid,  uniform 
cooling  of  the  glass  when  in  a  soft  state  after  it  has  been  already  blown  or  otherwise 
shaped.  By  this  means  it  acquires  such  a  physical  character  that  it  withstands  blows  or 
other  external  attacks  better  than  ordinary  glass  which  has  been  cooled  slowly  in  the 
usual  manner.  Besides  the  oil-baths  used  by  De  la  Bastie  must  be  noticed  the 
process  of  hardening  with  cold,  solid  objects,  e.g.,  plates  of  clay,  proposed  by  Fr.  Siemens. 

The  glasses  to  be  hardened,  after  they  have  been  heated  to  softness,  are  subjected  to 
a  sudden  chill,  which  may  be  effected  by  very  various  means.  In  consequence  of  the 
rapid  cessation  of  the  state  of  softness  there  sets  in  a  state  of  molecular  tension  to 
which  the  hardened  glass  is  indebted  for  its  peculiar  properties.  The  glass  to  be 
hardened  must  be  well  melted  and  clarified,  and  should  contain  neither  unmelted 
quartz  grains  nor  glass  gall.  Articles  of  badly  clarified,  streaky  glass  generally  burst 
in  the  hardening  bath.  The  external  form  and  the  thickness  of  the  vessels  have  a 
great  influence  upon  the  results.  Vessels  with  thick  sides  have  to  be  hardened  in  very 
thick  baths,  and  the  chilling  must  not  be  too  sudden.  The  temperature  which  must 
be  given  to  the  objects  is  that  at  which  the  glass  softens,  and  they  are  plunged  into 
the  bath  either  directly  after  being  blown  or  after  being  re-heated.  At  the  first 
introduction  of  the  process  it  was  supposed  that  the  chemical  composition  of  the 
hardening  bath  was  a  point  of  importance,  only  certain  oils  and  fats  being  suitable  and 
elementary  substances  being  excluded.  It  was  soon  found  that  the  physical  properties 
only  of  the  hardening  baths  were  of  importance.  One  and  the  same  quality  of  glass 
can  be  tempered  equally  well  in  different  baths,  but  the  temperature  must  be  higher 
or  lower  according  to  their  conductivity.  Baths  which  conduct  heat  well  require  a 
higher  temperature  than  those  which  have  a  low  conductive  power,  if  the  chilling 
effect  is  to  be  alike  in  both.  The  first  group  of  substances  selected  for  tempering 
baths  comprise  liquids  and  solids  which  are  liquefied  at  the  required  temperature,  e.g.. 


SECT,  v.]  GLASS   MANUFACTUKE.  617 

mixtures  of  fats,  oils,  glycerine,  paraffine,  hydrocarbons,  saline  solutions,  and  easily 
fusible  alloys.  Pure  water  is  excluded.  Glasses  which  have  been  hardened  in  an  oil 
bath  at  70°  burst  if  plunged  into  water  of  the  same  temperature.  Baths  composed  of 
fats  have  proved  most  satisfactory,  the  better,  in  general,  the  longer  they  have  been  in  use. 

The  objections  to  fat  baths  are  their  costliness,  their  combustibility  and  the  fact  that 
their  temperature  is  continually  raised  by  the  introduction  of  hot  objects. 

In  the  case  of  solid  bodies  the  hardening  is  effected  simultaneously  with  shaping. 
In  liquid  baths  the  softened  objects,  especially  plates,  lose  their  shape  more  or  less. 
For  the  goodness  of  hard  glass  it  is  important  that  both  the  heating  and  the  chilling 
are  effected  with  the  utmost  possible  rapidity.  It  is  also  important  that  the  glass 
should  be  heated  to  the  highest  point  at  which  it  can  be  lifted  out  of  the  furnace. 

A  hardened  glass  plate  of  16  centimetres  in  length,  12  centimetres  in  breadth,  and 
5  millimetres  in  thickness  bore  the  fall  of  a  weight  of  200  grammes  from  the  height  of 
4  metres.  A  similar  plate  of  common  glass  was  broken  by  a  weight  of  100  grammes 
falling  a  height  of  30  to  40  centimetres.  Hardened  glass  also  bears  pressure  to  about 
four  times  the  extent  of  common  glass.  But  the  same  tension  which  gives  to  hardened 
glass  its  elasticity  and  solidity  is  the  cause  of  explosive  disruptions  if  suddenly  liberated 
at  any  one  point.  Articles  which  are  exposed  to  shocks  or  blows  on  their  sides  or 
corners  should  not  be  hardened — e.g.,  plates,  beakers,  capsules,  &c.  A  hardened  glass 
plate  which  bears  the  fall  of  considerable  weights  if  struck  in  the  middle  breaks  easily 
by  a  blow  on  its  edges,  especially  from  a  narrow  instrument.  In  common  glass  only  a 
few  splinters  may  be  broken  off,  so  that  the  vessel  may  still  be  fit  for  use,  whilst 
hardened  glass  is  completely  shattered.  Hence  the  process  cannot  be  recommended 
for  bottles,  drinking  glasses,  &c. :  whilst  window  panes  or  plates,  which  are  mostly  ex- 
posed to  blows  on  the  surface,  where  they  are  most  resistant,  are  much  better  fitted 
for  hardening.  The  great  objection  to  hardened  glass  is  that  there  is  no  means  of 
distinguishing  good  from  bad  articles  until  they  come  into  actual  use.  Hence  the 
original  confidence  of  the  public  has  been  succeeded  by  justifiable  distrust.  For 
laboratory  apparatus  hardened  glass  is  quite  unfit,  and  for  domestic  purposes  it  is  at 
least  very  doubtful.  Hence  it  has  almost  entirely  disappeared  from  commerce. 

Soluble  Glass,  Water  Glass. — By  water  glass  is  understood  a  soluble  alkaline  silicate. 
Its  preparation  is  effected  by  melting  sand  with  much  alkali,  the  result  being  a  fluid 
substance,  first  observed  by  "Van  Helmont  in  1640. 

It  was  made  by  Glauber  in  1648  from  potash  and  silica,  and  by  him  termed  fluid 
silica.  Von  Fuchs,  in  1825,  obtained  what  is  now  known  as  water  glass  by  treating 
silicic  acid  with  an  alkali,  the  result  being  soluble  in  water,  but  not  affected  by  atmo- 
spheric changes. 

The  various  kinds  of  water  glass  are  known  as — 

Potash  water  glass. 
Soda  ,, 

Double         „ 
Fixing  „ 

Potash  water  glass  is  obtained  by  the  melting  together  of  pulverised  quartz  or 
purified  quartz  sand  45  parts,  potash  30  parts,  powdered  wood  charcoal  3  parts,  the 
molten  mass  being  dissolved  by  means  of  boiling  in  water.  The  solution  contains 
much  potassium  sulphide,  which  is  removed  by  boiling  with  copper  oxide.  The 
addition  of  carbon  assists  in  reducing  part  of  the  carbonic  acid  to  carbonic  oxide, 
which  disappears  during  the  melting.  Soda  water  glass  is  prepared  with  pulverised 
quartz  5  parts,  calcined  soda  23  parts,  carbon  3  parts ;  or,  according  to  Buchner, 
with  pulverised  quartz  100  parts,  calcined  Glauber's  salts  60  parts,  and  carbon  15  to 
20  parts.  Double  water  glass  (potash  and  soda  water  glass)  is  prepared,  according  to 
Doebereiner,  by  melting  together  quartz  powder  152  parts,  calcined  soda  54  parts, 


618  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

potash  70  parts  ;  according  to  Yon  Fuchs,  from  pulverised  quartz  100  parts,  purified 
potash  28  parts,  calcined  soda  22  parts,  powdered  wood  charcoal  6  parts.  It  is 
further  obtained  by  melting  potassium  and  sodium  tartrate, 

4H406    +    4H20, 

with  quartz  ;  from  equal  molecules  of  potassium  and  sodium  nitrate  and  quartz  ;  from 
purified  tartar  and  sodium  nitrate  and  quartz.  It  is  more  fusible  than  the  foregoing. 
For  technical  purposes  a  mixture  of — 

3  volumes  of  concentrated  potash  water  glass  solution, 
2  „  „  soda  „  „ 

is  employed.  By  the  name  of  fixing  water  glass,  Yon  Fuchs  designates  a  mixture  of 
silica  well  saturated  with  potash  water  glass  and  a  sodium  silicate,  obtained  by  melting 
together  3  parts  of  calcined  soda  with  2  parts  of  pulverised  quartz.  It  is  used  to  fix 
or  render  the  colours  permanent  in  stereochromy. 

The  kind  known  commercially  as  prepared  water  glass  is  obtained  by  boiling  the 
powdered  water  glass  with  water ;  and  the  solution,  as  found  in  the  market,  is  known 
as  of  33°  and  66°,  the  difference  being  that  the  first  100  parts  by  weight  contain  33 
parts  by  weight  of  solid  water  glass  and  67  parts  by  weight  of  water.  It  therefore 
follows  that  in  solutions  of  40°  and  66°,  the  water  is  proportioned  as  60  and  34  parts 
respectively.  Acids,  with  the  exception  of  carbonic  acid,  decompose  water  glass  solu- 
tions, separating  the  silica  as  a  gelatinous  substance ;  it  should,  therefore,  be  kept  in 
vessels  well  protected  from  volatile  acids. 

Water  glass  is  an  important  product  in  industry.  It  is  used  to  render  wood,  linen, 
and  paper  non-inflammable.  The  water  glass  of  33°  is  first  mixed  with  double 
its  weight  of  rain-water,  and  is  then  treated  with  some  fire-proof  colouring 
matter,  as  clay,  chalk,  fluor-spar,  felspar,  &c.  The  material  to  be  rendered  unin- 
flammable is  painted  with  the  solution,  and  again  with  another  coat  after  the  first  has 
remained  twenty-four  hours  to  dry.  Wood  is  thus  preserved  from  being  worm- 
eaten,  from  incrustation  of  fungi,  &c.  Another  industrial  application  of  water 
glass  is  as  a  cement ;  in  this  it  is  equal  to  glue,  and,  indeed,  is  known  as  "  mineral 
glue."  Chalk  mixed  with  water  glass  forms  a  very  compact  mass,  drying  as  hard  as 
marble;  no  chemical  change  is  hereby  effected;  there  is  no  conversion  to  calcium 
silicate  or  potassium  carbonate ;  the  hardening  is  entirely  the  result  of  adhesion. 
Calcium  phosphate  treated  with  water  glass  acts  similarly.  Zinc-white  and  magnesia 
lose  none  of  their  useful  properties  when  mixed  with  water  glass.  Another  im- 
portant application  of  water  glass  is  in  the  painting  of  stone  and  concrete  walls, 
and  in  the  preparation  of  artificial  stone.  The  latter,  first  made  by  Ransome,  is 
daily  meeting  with  more  extended  application  in  England,  India,  and  America.  It 
is  prepared  by  mixing  sand  with  sodium  silicate  to  a  plastic  mass,  which  is  pressed 
into  the  required  shape,  and  then  placed  in  a  solution  of  calcium  chloride.  By 
this  means  calcium  silicate  is  formed,  and  cements  the  grains  of  sand  together,  while 
the  sodium  chloride  is  removed  by  repeated  washings.  As  cement  for  stone,  glass, 
and  porcelain,  water  glass  is  especially  useful.  It  is  also  employed  in  the  preparation 
of  xyloplastic  casts,  made  of  wood  rendered  pulpy  by  treatment  with  hydrochloric  acid, 
and  afterwards  impregnated  with  water  glass. 

Stereochromy. — An  interesting  and  important  application  of  water  glass  is  in  the  new 
art  of  mural  and  monumental  painting,  termed  by  Yon  Fuchs  Stereochromy  (a-repeos, 
solid,  and  xPwMa>  colour).  In  this  method  of  painting  the  water  glass  forms  the 
foundation  or  binding  material  of  the  colour.  There  is  first  to  be  considered  the 
mortar  or  cement  ground  upon  which  the  painting  is  to  be  executed.  This  ground 
has  to  receive  an  under-  and  an  over-ground.  It  is  essential,  of  course,  that  the 
fundamental  groundwork  should  be  of  a  stone  or  cement  possessing  every  requisite 


SECT,  v.]  GLASS   MANUFACTURE.  619 

for  durability.  The  next,  or  under-ground,  is  made  with  lime-mortar,  and  is  allowed 
to  remain  for  some  time  to  harden.  When  well  dried,  the  water  glass  solution 
is  applied,  and  allowed  to  soak  well  into  the  interstices  of  the  mortar.  After  the 
under-ground  has  been  thus  prepared,  the  over-ground,  or  that  to  receive  the  painting, 
is  laid  on.  This  consists  of  similar  constituents  to  the  under-ground,  with  the 
exception  that  a  good  sharp  sand  is  used,  and  the  mixture  treated  with  a  thin  lye 
of  calcium  carbonate.  This  over-ground  of  fine  cement  being  nicely  levelled,  and 
having  dried,  it  is  thoroughly  impregnated  with  water  glass.  When  this  is  dry,  the 
painting  is  executed  in  water-colours.  Nothing  further  is  necessary  than  to  fix  these 
colours,  which  is  effected  by  a  treatment  with  a  fixing  water  glass.  The  colours 
employed  are : — Zinc-white,  chrome-green,  chrome-oxide,  cobalt-green,  chrome-red 
(basic  lead  chromate),  zinc-yellow,  iron  oxide,  cadmium  sulphide,  ultramarine, 
ochre,  &c.  Vermilion  is  not  employed,  as  it  changes  colour  in  fixing,  turning  to  a 
brown.  Cobalt-ultramarine,  on  the  contrary,  brightens  on  the  application  of  the  fixing 
solution,  and  is,  therefore,  a  very  effective  colour.  As  a  decorative  art  stereochromy 
will  doubtless  attain  great  importance,  the  paintings  being  unaffected  by  rain,  smoke,  or 
change  of  temperature. 

Crystal  Glass. — Crystal  glass  includes  all  potash  glass  containing  lead.  Crystal 
glass  was  first  prepared  in  England.  There  are  a  few  difficulties  in  manufacturing  this 
glass.  The  smoke  from  an  anthracite  coal  fire  is  injurious  to  the  pure  colour  of  the 
glass,  so  that  the  melting-pot  is  provided  with  a  cover ;  but  this  addition  has  the  dis- 
advantage that  the  temperature  necessary  to  melt  the  glass  cannot  easily  be  ascertained. 
A  larger  proportion  of  alkali  must  therefore  be  added,  which  deteriorates  the 
quality  of  the  glass,  rendering  it  liable  to  after-change.  To  prevent  this  as  much  as 
possible,  lead  oxide  is  used  to  make  the  glass  more  easily  fusible,  and  by  this  means  a 
beautifully  clear,  transparent  glass  results.  The  following  table  will  give  some  idea  of 
the  proportions  of  the  materials  : — 

Sand 300 

Potash        .        .        .        .        »..'*.        .  too 

Broken  glass «         .         .  300 

Minium .        .        ...  200 

Arsenious  acid 0-60 

Manganese  sesquioxide 0*45 

The  following  mixture  is  used  in  the  glass  houses  of  Edinburgh  and  Leith  : — 

Sand 300 

Potash 100 

Minium 150 

Lead-glaze 50 

and  a  small  quantity  of  manganese  sesquioxide  (braunite)  or  arsenious  acid. 

To  render  the  glass  fluid,  saltpetre  is  sometimes  added,  but  in  moderate  quantities. 
Dumas  recommends  sand  300,  minium  200,  dry  potash  95  to  100.  On  the  supposition 
that  there  is  no  loss  during  melting,  the  mixtures  contain  : — 

Silica 57-4  57 

Lead  oxide  36*3  ...  36 

Potash 6-3  ...  7 


The  whole  melting  process  is  concluded  in  twelve  to  sixteen  hours.  The  glass  is 
treated  in  a  manner  similar  to  that  already  described,  but  is  more  easily  worked. 
Benrath  (a)  and  Faraday  (/3)  found  crystal  glass  by  analysis  to  consist  of :— 


620  CHEMICAL   TECHNOLOGY.  [SECT.  v. 

j8. 

Silicic  acid SO'iS          ...        51 '93 

Oxide  of  lead 38-11          ...        33'28 

Potash ii*6i          ...         i3'67 

Alumina,  &c. 0^04 


99  '94          •••         98-88 
According  to  Benrath,  normal  crystal  glass  has  the  formula   K10Pb7Si36084  (i.e., 


Polishing.  —  Crystal  glass  is  either  cast  in  brass  moulds  or  is  ground.  Its  hardness 
admits  of  its  taking  a  better  polish  than  other  glasses.  The  grinding  wheel  is  of 
cast-iron  ;  above  the  periphery  is  fixed  a  vessel  containing  water  and  fine  washed  sand, 
which  constantly  drops  upon  the  wheel,  assisting  in  the  cutting.  The  polishing  wheel  is 
of  wood,  well  served  with  pumice-powder  and  water. 

Optical  Glass.  —  The  preparation  of  good  optical  glass,  especially  of  large  dimensions, 
is  a  matter  of  much  difficulty.  Transparency,  hardness,  a  high  refractive  power  with 
perfect  achromatism  are  all  required,  and  must  be  obtained  at  the  outlay  of  any  amount 
of  labour.  The  glass  must  also  be  entirely  homogeneous,  else  the  light  is  not  refracted 
regularly;  threads  and  streaks  (striae)  are  the  results  of  inequality,  and  it  naturally 
follows  that,  if  these  appear  to  the  unassisted  eye,  they  will  seriously  affect  delicate 
observations  when  high  magnifying  powers  are  used,  as  in  telescopes  and  microscopes. 
It  is  an  error,  however,  to  suppose  that  these  irregularities  arise  from  impurities  ;  they 
are  rather  due  to  interruptions  in  heating  and  cooling,  or  to  unequally  heating  and 
cooling  during  manufacture.  This  must  especially  be  evident  in  the  case  of  waviness  or 
an  undulating  structure  of  the  glass.  Crown  glass,  free  from  lead,  is  not  so  liable 
to  faults  as  flint  glass  ;  both  these  are  employed  for  optical  purposes. 

The  Rev.  Mr.  Harcourt's  experimental  researches  as  to  the  best  optical  glass,  com- 
municated to  the  British  Association,  at  the  recent  meeting  at  Edinburgh,  by  Professor 
Stokes,  show  fully  what  has  been  accomplished  in  preparing  glass  of  this  order. 
Mr.  Harcourt's  researches  were  chiefly  carried  on  with  phosphates,  combined  in  many 
<jases  with  fluorides,  and  sometimes  with  tungstates,  molybdates,  and  titanates,  owing 
to  the  difficult  fusibility  and  pasty  consistency  of  silicate  glasses.  The  experiments 
included  glasses  containing  potassium,  sodium,  lithium,  barium,  strontium,  calcium, 
aluminium,  manganese,  magnesium,  zinc,  cadmium,  lead,  tin,  nickel,  chromium,  lead, 
thallium,  bismuth,  antimony,  tungsten,  molybdenum,  titanium,  vanadium,  phosphorus, 
fluorine,  boron,  and  sulphur.  The  molybdic  glasses  first  prepared  were  of  a  somewhat 
deep  colour,  deteriorating  with  age  ;  but  at  length  molybdic  glass  was  obtained  free 
from  colour,  and  permanent.  Titanic  acid  gave  results  much  superior  to  those  obtained 
with  molybdic.  Glass  made  with  lead  terborate  agreed  in  dispersive  power  with 
flint  glass  ;  while  a  prism  of  this  glass  extends  the  red  and  blue  ends  of  the  spectrum 
equally  with  a  prism  of  one  part  by  volume  of  flint  glass  with  two  of  crown  glass.  Not- 
withstanding the  great  difficulties  arising  from  striae,  Mr.  Harcourt  finally  succeeded  in 
preparing  discs  of  lead  terborate  and  of  titanic  glass,  3  inches  in  diameter,  almost 
homogeneous. 

It  is  well  known  that  flint  and  crown  glass  form  an  achromatic  combination.  Hint 
glass  is  very  easily  rendered  fluid,  conducing  to  the  formation  of  striae.  A  variation  of 
the  proportions  of  the  constituent  materials,  though  not  producing  effects  visible  to  the 
eye  alone,  will  strongly  striate  the  glass,  rendering  it  unfit  for  optical  purposes.  The 
constituents  must  be  equally  distributed  throughout,  and  this  is  a  great  difficulty.  The 
oxide  of  lead,  being  of  so  much  greater  weight,  sinks  to  the  bottom,  while  the  lighter 
•constituents  float  at  the  upper  part  of  the  melting  vessel.  Usually  this  is  so  much  the 
case  that  glasses  of  different  specific  gravities  are  obtained  from  the  upper  and  lower 
parts  of  the  melting-pot. 


SECT.    V.] 


GLASS   MANUFACTURE 


621 

Bontemps  manufactures  flint  glass  in  the  following  manner  -—A  glass  mass  is  pre- 
pared of — 

White  sand     .  .        .  ....   ,  IOO  kilos. 

Minium  .         .         .         .  Io6 

Potassium  carbonate       .....  4, 

and  placed  over  an  anthracite  or  stone-coal  fire  in  a  small  melting  oven  shown  in  Fig. 
430  in  vertical,  and  in  Fig.  431  in  horizontal  section.     The  oven  contains  only  one 


Fig.  430. 


Fig.  431. 


covered  melting  vessel,  B,  standing  on  the  bank,  A 
a  a  are  the  grate  bars  ;  c  an  iron  rake,  enclosed  in 
a  fire-clay  cylinder,  d,  and  resting  upon  the  roller, 
/.  After  about  fourteen  hours  the  mass  becomes 
equally  fluid  ;  and  a  red-hot  rake  is  introduced  into 
the  vessel,  by  which  the  several  layers  of  material 
are  intimately  mixed.  In  about  five  minutes  the 
mass  is  sufficiently  stirred  ;  the  iron  rod  is  then 
removed,  the  clay  cy Under  remaining.  This  stir- 
ring is  effected  several  times  without  removing  the  clay  cylinder ;  and  the  glass  is  then 
ready  for  blowing  or  casting.  But  for  optical  purposes  it  is,  after  the  removal  of  the 
clay  cylinder,  allowed  to  cool  gradually  during  eight  days  in  an  annealing  oven.  The 
most  perfect  pieces  of  glass  are  then  cut  from  the  interior  of  the  mass.  According  to 
Dumas's  analysis  of  a  sample  obtained  from  Guinand,  flint  glass  consists  of — 


Silica         .         .         .         .         . '       .  '   " . . 

Lead  oxide 

Lime . 

Potash      

Alumina,  iron  oxide,  and  manganese  protoxide 


42'S 
43'5 

o'S 
117 

1-8 


lOO'O 


The  second  kind  of  optical  glass,  crown  glass  free  from  lead,  contains,  according 
to  Bontemps: — Sand,  120;  potash,  35;  soda,  20;  chalk,  15;  and  arsenious  acid, 
i  part. 

The  best  optical  glass  now  known  is  that  used  by  Zeiss  of  Jena  for  the  object-glasses 
of  his  microscopes. 

Strass. — The  imitation  of  precious  stones  is  an  interesting  feature  of  glass  manu- 
facture, and  in  Egypt  and  Greece  it  was  an  art  that  attained  to  great  perfection.  All 
precious  stones,  with  the  solitary  exception  of  the  opal,  can  be  imitated  artificially.  The 
chief  constituent  of  these  artificial  gems  is  strass,  or,  as  it  was  termed  by  Fontanier, 
Mayence  base ;  and  in  France  artificial  gems  are  mostly  known  as  Pierres  de  Strass.  This 
base  is  colourless,  and  may  be  considered  as  a  borosilicate  of  the  alkalies  containing 
lead  oxide,  this  being  in  larger  proportion  than  in  flint  glass. 

Donault-Wieland  found  colourless  strass  by  analysis  to  consist  of  : — 


622  CHEMICAL   TECHNOLOGY.  [SECT. 

Silica .  38-1 

Alumina i'o 

Lead  oxide •  53'o 

Potash 7 -9 

Borax 


traces 

Arsenious  acidj 


This  analysis  gives  the  formula  (3K20,6Si02)  4  3(3PbO,6Si02). 

The  various  gems  are  imitated  by  the  addition  of  colouring  oxides,  the  whole  of  the 
materials  being  ground  to  a  fine  powder,  intimately  mixed,  and  melted  at  a  strong  heat. 
The  imitation  of  the  topaz  is  obtained  by  taking — strass,  1000;  antimony,  40;  and 
Cassius's  purple,  i  part.  The  topaz  can  also  be  imitated  with — strass,  1000 ;  iron 
oxide,  i  part.  The  imitation  ruby  is  obtained  with  i  part  of  the  topaz  paste 
and  8  parts  of  strass,  the  whole  being  melted  together  for  thirty  hours.  A  ruby  of 
less  beauty  is  obtained  with — strass,  1000 ;  manganese  dioxide,  5  parts.  A  good  emerald 
can  be  prepared  from — strass,  1000  ;  copper  oxide,  8;  chromium  oxide,  o-2  part.  The 
sapphire  is  obtained  from — strass,  1000  ;  pure  cobalt  oxide,  15  parts.  The  amethyst  from 
— strass,  1000;  manganese  dioxide,  8;  cobalt  oxide,  5;  Cassius's  purple,  0-2.  The 
beryl  or  aqua,  marina  is  imitated  by — strass,  1000  ;  glass  of  antimony,  7  ;  cobalt  oxide, 
0*4.  The  carbuncle  by — strass,  1000  ;  glass  of  antimony,  500 ;  purple  of  Cassius,  4; 
manganese  dioxide,  4  parts.  Sufficient  attention  has  not  been  paid  to  the  mode  in 
which  the  colouring  is  effected  by  the  metallic  oxides  ;  nor  have  experiments  been  tried 
with  any  definite  result  as  to  the  employment  of  tungstic  acid,  molybdic  acid,  titanic 
acid,  chromic  acid,  and  chromic  oxide,  &c. 

Genuine  rubies  and  sapphires,  crystals  of  alumina  with  all  the  characteristics — 
chemical  and  optical — of  the  natural  stones  have  now  been  obtained  artificially,  though 
of  small  size.* 

Coloured  Glass  and  Glass  Staining. — Coloured  glass  may  be  considered  in  two  classes 
— that  coloured  as  a  whole,  and  that  only  partially  coloured.  The  latter  is  prepared 
with  such  metallic  oxides  as  will  impart  to  the  glass  very  intense  colour ;  for  instance, 
cuprous  oxide,  cobalt,  gold,  and  manganese  oxides.  This  kind  of  glass  is  termed  super- 
fine, and  is  prepared  in  the  following  manner : — Two  melting  vessels  are  placed  in  the 
oven ;  one  contains  a  lead  glass,  the  other  the  coloured  glass.  We  will  take  as  an 
example  glass  coloured  red  with  cuprous  oxide,  which  if  further  oxidised  imparts  a 
green  colour  to  the  glass.  The  glass  blower  dips  his  pipe  first  into  the  red  glass ;  and 
collects  a  sufficient  quantity  to  blow ;  then  he  dips  this  into  the  white  glass,  and  pro- 
ceeds to  form  a  cylinder  or  roll,  as  in  the  making  of  table  glass.  Superfine  glass  is 
known  as  "  outside  "  and  "  double,"  or  "  double  layer."  In  the  first  case  the  workman 
takes  a  lump  of  white  glass  upon  his  pipe  and  covers  it  with  the  coloured  glass ;  or, 
in  the  second  case,  he  takes  up  only  a  small  quantity  of  white  glass,  then  sufficient  of 
the  coloured  glass,  and  again  more  white  glass.  Red  glass  may  be  obtained  with  either 
Cassius's  purple,  cuprous  oxide,  or  iron  oxide  as  the  colouring  ingredient.  Cassius's 
purple  is  used  chiefly  for  ruby-red  glass.  It  was  long  thought  that  ruby-coloured 
glass  could  not  be  obtained  with  any  other  preparation  than  Cassius's  purple,  but 
twenty-five  years  ago  Fuss  showed  that  gold  chloride  was  effectual.  If  glass  con- 
taining salts  of  gold  or  cuprous  oxide  is  cooled  suddenly,  the  colour  disappears ; 
then  if  again  gently  warmed,  not  quite  to  softness,  the  colour  suddenly  reappears 
in  full  splendour.  This  phenomenon  occurs  equally  in  atmospheres  of  oxygen, 
hydrogen,  and  carbonic  acid.  In  the  preparation  of  cuprous  oxide  glass,  lead  glass 
'is  taken  as  a  basis,  to  which  3  per  cent,  of  the  cuprous  oxide  is  added.  The 

*  In  the  artificial  sapphire  the  blue  colour  has  been  obtained,  in  the  absence  of  cobalt,  by  a 
compound  of  chromium  not  yet  examined. 


SECT,  v.]  GLASS   MANUFACTURE.  623 

drawback  to  the  employment  of  the  protoxide  is  the  readiness  with  which  it  becomes 
oxide,  thus  imparting  a  green  colour  to  the  glass.  To  prevent  this  change,  iron  filings, 
rust,  or  tartar  is  added,  or  the  glass  is  stirred  with  green  wood.  Copper  glass,  as 
has  just  been  said,  is  colourless  on  cooling,  regaining  its  colour  during  the  process  of 
annealing.  Iron  oxide,  known  commercially  as  blood-stone,  ochre,  or  red  chalk,  is 
also  used  to  impart  a  red  colour.  Yellow  and  topaz-yellow  are  obtained  by 
means  of  potassium  antimoniate  or  glass  of  antimony,  silver  chloride,  borate,  and 
sulphide.  Uranium  oxide  imparts  a  green-yellow.  Blue  is  obtained  from  cobalt 
oxide,  more  seldom  by  means  of  copper  oxide.  Green  results  from  the  addition  of 
chrome-oxide,  copper  oxide,  and  ferrous  oxide.  "Violet  is  obtained  from  manganese 
oxide  (braunite)  and  saltpetre ;  black,  from  a  mixture  of  ferrous  oxide,  copper 
oxide,  braunite,  and  cobalt  oxide.  A  beautiful  black  results  from  iridium  sesqui- 
oxide. 

For  the  production  of  Satin  Glass,  vessels  blown  of  coloured  glass  are  further  blown 
within  a  metal  mould  so  as  to  display  in  a  kind  of  relief  depressed  stripes,  rows  of 
small  depressions.  Then  comes  a  layer  of  colourless  crystal  glass  above  the  coloured 
glass.  It  attaches  itself  to  the  smooth,  level  parts,  but  it  does  not  penetrate  into  the 
depressions,  which  remain  filled  with  air.  When  the  vessel  is  completed,  fitted  with 
handles,  feet,  &c.,  and  has  been  cooled  down,  the  outer  surface  receives  a  matt  polish 
which  gives  it  a  satin-like  appearance.  The  favourite  colours  for  this  style  are  reseda 
green,  heliotrope  violet,  garnet  red,  and  jonquil  yellow. 

Painting  on  Glass. — The  delineation  of  figures  and  scriptural  events  in  coloured 
glass  dates  from  a  very  remote  period.  At  first  the  work  was  merely  mosaic,  pieces  of 
coloured  glass  being  inserted  in  leaden  framework.  Glass  painting  was  known  in 
Germany  in  the  Middle  Ages,  and  soon  extended  throughout  Europe.  In  the  thirteenth 
century,  when  Gothic  architecture  became  prevalent,  glass  painting  also  became  more 
general,  as  until  then  the  heavy,  round-arched  windows  were  too  small  to  admit  of 
ornament.  But  it  was  not  until  the  fifteenth  century  that  the  heavy  outlined  figures  were 
discarded  for  the  more  mingled  colours  of  heraldic  device,  as  seen  in  the  churches  of 
Sebaldus  and  Lorenz,  of  Nuremburg,  in  the  productions  of  the  celebrated  Hirschvogel 
family.  This  style  lasted  till  the  sixteenth  century,  when  the  glassmaker  tried  the  effect 
of  pigments  upon  glass.  Since  that  time  the  art  has  gradually  developed,  the  improve- 
ment at  first  being  most  manifest  in  France  and  the  Netherlands. 

The  nature  of  glass  painting  or  staining  is  in  principle  the  following : — When 
coloured  glass,  rendered  easily  fusible  by  the  metallic  oxide  it  contains,  is  finely  pulver- 
ised, and  laid  upon  a  plain  glass  surface  and  heated,  it  forms  a  skin,  or  "  flash,"  as  it  is 
termed,  this  skin  or  layer  of  glass  being  said  to  be  "  flashed  on."  It  is  evident  that 
very  brilliant  effects  may  thus  be  obtained.  The  near  surface  of  the  glass  receives  the 
strong  shades  and  colours,  the  other  or  distant  surface  the  lighter  tints.  White  was 
not  employed  in  the  older  glass  paintings,  but  is  now  used  in  the  flesh-tints,  pure  white 
effects,  &e.  Tin  oxide  and  potassium  antimoniate  yield  a  good  white.  For  yellow, 
Naples-yellow,  or  antimony-yellow,  or  a  mixture  of  the  iron,  tin,  and  antimony  oxides, 
or  of  antimonic  acid  and  iron  oxide,  of  silver  and  antimony  sulphides,  or  silver 
chloride  is  used ;  for  red,  iron  oxide,  purple  of  Cassius,  and  a  mixture  of  gold  oxide, 
tin  oxide,  and  silver  chloride ;  for  the  brown,  manganese  oxide,  yellow  ochre,  umber, 
and  iron  chromate ;  for  black,  iridium,  platinum,  cobalt,  and  manganese  oxides ;  for 
blue,  cobalt  oxide,  or  potassium-cobalt  nitrate;  for  green,  chromium  and  copper 
oxides.  Two  kinds  of  colours  are  distinguished,  the  hard  and  the  soft.  The  soft 
are  called  varnish  colours,  are  very  easily  melted,  forming  a  kind  of  glaze  upon  the 
glass.  These  colours  are  placed  upon  the  outer  surface.  The  hard  or  decided  tints  are 
semi-opaque,  and  are  placed  upon  the  inner  surface  of  the  glass.  The  binding  fluid 
or  vehicle  is  a  mixture  of  silica,  minium,  and  borax,  with  which  the  colour,  being  pre- 


624  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

viously  ground  to  a  fine  powder,  is  intimately  mixed.  This  mixture  is  painted  on  the- 
glass  with  a  pencil,  and  the  glass  plate  is  afterwards  fired  in  a  muffle.  Volatile  oils  have 
recently  been  employed  as  vehicles — viz.,  oil  of  turpentine,  lavender,  bergamot,  and 
cloves.  The  burning-in,  or  firing,  the  colours  was  formerly  effected  by  placing  the 
glass  tablet  with  dried  and  pulverised  lime  in  an  iron  pan  raised  to  a  red  heat.  But 
recently  the  muffle  oven  has  been  employed.  The  bottom  of  the  muffle  is  covered  to  a 
depth  of  one  inch  with  dry  powdered  lime,  upon  which  the  plate  of  glass  is  laid,  and 
again  a  layer  of  lime.  The  oven  is  then  raised  equally  to  a  dark-red  heat.  After  six 
to  seven  hours  the  fire  is  gradually  withdrawn,  and  the  oven  allowed  to  cool.  The  glass 
is  taken  out,  cleansed  with  warm  water,  and  dried. 

Enamel,  Bone  Glass,  Alabaster  Glass. — By  enamel  is  understood  in  glass  manufac- 
ture a  coloured  or  colourless  glass  mass  rendered  opaque  by  the  addition  of  oxide  of  tin. 
It  was  formerly  prepared  in  the  following  manner  : — An  alloy  of  15  to  1 8  parts  tin  and 
100  parts  lead  was  oxidised  by  heat  in  a  stream  of  air,  the  oxide  pulverised  and  washed. 
The  mixture  of  the  oxides  was  then  fritted  with  the  glass.  An  enamel-like  appearance 
is  imparted  to  glass  by  arsenious  acid,  silver  chloride,  calcium  phosphate,  cryolite, 
fluor-spar,  sodium  aluminate,  and  precipitated  barium  sulphate.  Bone  glass,  so  called, 
is  a  milk-white,  semi-opaque  glass,  containing  calcium  phosphate  in  the  shape  of 
white  bone-ash,  sombrerite,  or  phosphorite.  It  is  employed  for  lamp  globes  and  shades, 
thermometer  scales,  &c.  It  is  made  by  adding  to  white  glass  about  10  to  20  per  cent. 
of  white  bone-ash,  or  a  corresponding  quantity  of  mineral  phosphate.  After  melting, 
the  glass  is  generally  clear  and  transparent,  becoming  milk-white  and  opaque  during  the 
process  of  blowing.  The  colour  is  finally  developed  during  annealing. 

A  glass  resembling  bone  glass,  but  opaque  and  of  as  uperior  lustre,  is  the  alabaster  or 
opal  glass,  sometimes  known  as  rice  glass.  It  is  merely  a  preliminary  stage  in  the 
formation  of  glass,  very  rich  in  silica  and  imperfectly  fused.  Its  opacity  is  derived  from 
undissolved  particles.  The  same  mixture  is  used  for  alabaster  glass  as  for  crystal  glass ; 
as  soon  as  it  is  melted  it  is  baled  out  and  chilled.  When  the  next  lot  is  melted  the 
chilled  mass  is  put  upon  it  and  worked  up  together  at  the  lowest  possible  temperature. 
The  undissolved  particles  of  the  melt  which  cause  the  turbidity  should  be  only  micro 
scopic,  and  be  neither  distinctly  perceptible  grains  nor  bubbles.  This  is  the  great  diffi- 
culty in  the  manufacture  of  alabaster  glass,  since  the  impurities  as  a  rule  do  not  dis- 
appear until  the  mass  has  been  thoroughly  melted  and  clarified.  Alabaster  glass  is 
identical  with  Reaumur's  procelain. 

Cryolite  Glass  (hot  cast  porcelain)  is  obtained,  according  to  Williams,  by  melting  a 
mixture  of — 

Silica        .' 67-19 

Cryolite 23-84 

Zinc  oxide        .  8-97 

An  Austrian  cryolite  glass,  according  to  Weinreb,  contained — 

Silica 78-00 

Alumina 3-12 

Ferric  oxide trace 

Manganous  oxide trace 

Lime 3-87 

Soda 9-46 

Potassa   ..........  4-35 

Fluorine .        -377 

Ice  Glass. — Ice  glass  is  made  by  plunging  the  mass  of  glass  attached  to  the  end 
of  the  blower's  pipe,  still  at  a  glowing  red  heat,  into  hot  water,  in  which  the 
glass  is  opened  and  blown  out.  It  then  resembles  a  mass  of  thawed  ice,  with  a 
beautifully  pellucid  appearance.  It  is  also  known  as  crackle  glass  ;  in  France,  as 


SECT,  v.]  GLASS   MANUFACTURE.  625 

verre  craquele.     Agate   glass  is   obtained   by  melting   together  the   waste   pieces  of 
coloured  glass. 

Hematinone  and  Aventurine  have  already  been  described. 

Muslin  Glass  is  plate  glass  ornamented  with  designs  in  dead  white.  One  method 
of  producing  this  effect  consists  in  flashing  over  the  surface  a  thin  layer  of  plumbiferous 
crystal  glass.  The  other  method  depends  on  coating  the  glass  with  a  coating  of  enamel. 
The  mixture  of  the  Belgian  enamel  is  100  parts  sand,  no  red  lead,  no  parts  of  cullet 
(from  crystal  glass),  35  borax  (anhydrous),  and  25  parts  tin  oxide. 

Glass  relief. — Glass  relief  is  obtained  by  enclosing  a  body  of  well-burnt  unglazed 
white  clay,  moulded  to  the  required  form  between  layers  of  lead-glass,  the  result  being 
similar  in  appearance  to  an  article  in  matted  silver.  Gold  matte  is  imitated  by  employing 
a  yellow  glass.  This  branch  of  their  art  has  been  known  to  the  Bohemian  glass 
manufacturers  for  upwards  of  eighty  years. 

Iridescent  Glass. — Since  1872  articles  of  glass  have  been  made  with  rainbow  coloured 
iridescence.  Such  glass  was  first  obtained  by  Brianchon  by  coating  the  objects  (i.e,, 
paper-weights,  &c.,)  with  a  flux  of  auriferous  bismuth  oxide,  so  thin  that  it  is  almost  imper- 
ceptible by  transmitted  light,  but  in  reflected  light  shows  the  colours  of  the  spectrum. 
Whether  the  observation  of  Fremy  and  Clemandot  that  glass  can  be  made  iridescent  by 
treatment  with  hydrochloric  acid  under  pressure  can  be  applied  in  practice  is  still 
undecided. 

Filligree  or  Reticulated  Glass. — By  fibre  or  filligree  glass  is  understood  that  kind  of 
glass  work  formed  of  variously  coloured  or  white  opaque  glass  threads,  these  threads 
being  sometimes  as  fine  as  a  single  hair.  They  are  generally  drawn  from  tubes  or 
sticks  of  glass  of  various  colours,  heated  to  redness,  and  formed  into  sticks,  tubes,  or 
spirals.  Two  of  these  tubes  are  taken,  placed  together,  and  blown  out  into  a  vessel 
of  the  required  form,which  is  characterised  by  the  conformation  of  the  glass  threads  in 
the  stick.  From  the  spiral  network  thus  formed  this  kind  of  glass  is  sometimes  termed 
reticulated. 

Millifiore  Work. — Millifiore  work  is  a  peculiar  form  of  mosaic  glass  work,  in  prepa- 
ration similar  to  that  of  Petinet  glass.  Small  filligree  canes  of  different  coloured  glass 
are  placed  side  by  side  to  form  a  thick  cord  or  column,  the  cross  section  of  which  appears 
of  a  particoloured  grain.  These  cords  or  columns  can  be  twisted  to  almost  any  required 
form,  or  when  heated  and  drawn  out  the  glass  threads  of  various  colours  of  which  it  is 
composed  form  a  single  thread  of  very  varied  hue  and  great  beauty.  These  threads 
again  can  be  worked  into  ornaments,  or  formed  into  lumps  or  balls.  The  best  kind  of 
millifiore  work  are  the  paper-weights,  often  sold  at  fancy  bazaars  as  Bohemian  glass 
weights — these  are  merely  lumps  or  rolls  of  the  many  coloured  glass  thread  placed 
together,  heated,  and  finally  coated  with  a  film  of  clear  white  glass  by  being  for  a  few 
moments  held  in  the  white  glass  melting-pot. 

Glass  Pearls. — There  are  two  kinds  of  artificial  or  glass  pearls,  namely,  solid  or 
massive  pearls  and  blown  pearls.  The  first  are  known  as  Venetian  pearls,  and  those  made 
in  Venice  are  preferred,  the  export  from  this  city  in  1868  representing  a  money  value 
of  7,755,000  francs.  The  manufacture  is  chiefly  carried  on  in  the  Island  of  Murano. 
The  pearls  are  made  from  small  glass  tubes,  either  white  or  coloured.  Oxide  of  tin  is 
employed  in  the  preparation  as  well  as  the  various  metallic  oxides  for  imparting  the 
desired  colours. 

Solid  Pearls. — The  glass  tubes  are  cut  into  small  pieces  or  cylinders.  The  sharp 
edges  of  these  cylinders  are  removed  by  placing  them  in  an  iron  vessel  brought  to 
a  red  heat,  the  beads  being  constantly  stirred  with  an  iron  spoon.  Previous  to  this 
operation  the  interior  or  hollows  of  the  beads  are  filled  with  powdered  charcoal. 
They  are  then  well  washed,  dried,  and  packed.  By  another  mode  of  preparation, 
the  pieces  of  glass  tubing  are  placed  in  a  revolving  vessel  similar  to  a  coffee  roaster. 

2  B 


626  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

The  finished  pearls  are  generally  strung,  the  charcoal  being  placed  in  the  interior  or 
tube  to  prevent  its  closing. 

Blown  Pearls. — The  preparation  of  blown  pearls  is  quite  a  distinct  manufacture. 
They  resemble  the  real  pearl  in  form,  colour,  and  surface.  Jaquin,  a  French 
paternoster  or  rosary  maker,  in  the  year  1656,  remarked  that  when  whitings  (Cyprinus 
alburnua,  ablettes)  were  washed  with  water,  a  residue  remained  consisting  of  a  beautiful 
pearly  substance.  This  was  the  foundation  of  the  manufacture  of  the  artificial  pearl. 
Jaquin  scaled  the  fish,  mixed  the  scales  with  water,  and  obtained  the  celebrated 
"  Oriented  pearl-essence,"  or  "  Essence  d'Orient,"  a  substance  identical  with  Guanin. 
A  small  bead  of  gypsum  or  other  hardening  paste  is  coated  with  this  mixture,  dried, 
and  dipped  into  molten  glass,  a  thin  film  of  which  adheres. 

The  pearl  is  sometimes  round,  sometimes  pear-shaped,  or  flat.  Another  method  of 
preparing  the  pearls  is  by  means  of  beads  blown  from  glass  tubes  of  various  thicknesses. 
These  beads  or  small  bulbs  are  then  filled  with  pearl  essence.  To  prepare  this  essence, 
say  a  quantity  of  120  grammes,  4000  fish  are  necessary ;  thus  a  pound  of  pearl  essence 
requires  from  18,000  to  20,000  fish  for  its  preparation.  The  scales  are  allowed  to  stand 
about  an  hour  in  water  to  permit  the  slimy  matter  adhering  to  them  to  settle ;  they 
are  rubbed  down  in  a  mortar  with  fresh  water,  and  strained  through  a  linen  cloth. 
Thus  prepared  the  paste  is  ready  for  insertion  in  the  glass  beads,  a  little  ammonia 
being  added  to  prevent  decay. 

Into  the  red  pearls,  which  are  to  imitate  coral,  and  into  the  yellow  ones  there  are 
blown  suitable  colours  ground  up  with  gum  arabic,  and  into  the  marcasite  or  mirror 
pearls  there  is  introduced  an  easily  fusible  metallic  alloy. 

According  to  Heckert  (Pefcersdorf )  a  pearl  mosaic  with  perforated  pearls  is  made  by 
executing  the  pearl  mosaic  in  the  first  place  as  a  kind  of  embroidery ;  the  front  of  the 
pearls  is  then  attached  by  means  of  cement  or  enamel  to  the  objects  to  be  decorated. 
If  a  cement  is  used  the  tissue  and  the  threads  of  the  embroidery  are  burnt  away  after 
it  has  hardened.  If  enamel  is  used  it  is  melted  together  with  the  pearls.  The  effect 
is  very  fine. 

Glass  Etching. — Etching  in  glass  was  discovered  in  1670  by  Schwankhardt.  If 
powdered  fluor-spar  is  covered  with  strong  sulphuric  acid,  hydrofluoric  acid  is  given  off 
on  the  application  of  heat,  which  acts  upon  the  silica  of  the  glass  so  as  to  form  silicon 
fluoride,  which  escapes,  and  water.  At  the  parts  acted  upon  the  other  constituents  of 
the  glass  remain  as  a  loose  powder,  which  can  easily  be  removed.  The  idea  of  etching 
upon  glass  plate  designs  suitable  for  printing  came  from  Hann,  of  Warsaw  (1829). 
More  recently,  Bottger  and  Bromeis,  with  Auer,  of  Vienna,  have  improved  the  pro- 
cesses. The  etching-ground  used  for  engraving  on  metallic  surfaces  would  not  in  this 
case  give  favourable  results.  Pul  recommends  a  molten  mixture  of  i  part  asphalt  and 
i  part  colophonium,  with  as  much  oil  of  turpentine  as  will  bring  the  mass  to  the 
consistency  of  a  syrup.  Etched  glass  plates  have  been  used  by  B&ttger  and  Bromeis 
to  print  from  instead  of  steel  and  copper.  In  the  press  the  glass  plate  is  backed  by  a 
cast-iron  plate.  The  process,  however,  has  not  been  practically  successful ;  it  is  better 
suited  to  the  production  of  bank-notes,  &c.,  than  engravings,  the  resulting  etchings 
being  hard  in  tone.  But  for  purposes  of  decoration,  etched  glass  is  largely  used.  By 
the  method  of  Tessie  du  Motay  and  Marechal  of  Metz,  a  bath  is  made  of  250  grammes 
of  hydrofluoride  or  fluoride  of  potassium,  i  litre  of  water,  and  250  grammes  of  ordinary 
hydrochloric  acid.  Kessler  employs  a  solution  of  fluoride  of  ammonium. 

Etching  for  decorative  purposes  is  likewise  effected  with  hydrofluoric  acid. 
According  to  Tessie  du  Motay,  the  acid  is  best  produced  in  a  bath  of  250  grammes 
double  hydrogen  potassium  fluoride,  i  litre  water,  and  250  grammes  ordinary  hydro- 
chloric acid.  For  matte  etching  and  writing  on  glass,  Kessler  recommends  a  solution  of 
ammonium  fluoride,  which  is  found  serviceable  for  marking  bottles,  cylinders,  tubes,  &c. 


SECT.  v.J  GLASS   MANUFACTURE.  627 

For  matte  etching  on  glass  Reinitzer  uses  solutions  of  acid  alkaline  fluorides.  In 
order  that  the  matte  may  come  up  in  different  tones,  where  it  is  desired  to  obtain  the 
darkest  possible  tone  by  reflected  light,  the  practice  in  the  National  Glass  Painting  and 
Etching  Establishment  at  Budapest  is  to  etch  the  same  spot  twice  in  succession.  A 
single  etching  gives  a  lighter  tone,  and  for  still  lighter  tones  the  surface  which  has  been 
etched  is  cleared,  once  to  nine  times,  with  dilute  liquid  hydrofluoric  acid.  In  this 
manner  they  obtain  at  Budapest  eleven  gradations.  If  such  an  etched  plate  is 
examined  under  a  moderate  microscopic  power,  we  see  a  very  uniform  arrangement  of 
depressions  and  elevations  of  a  crystalline  form.  At  the  margin  of  the  matte  surface 
these  crystals  are  more  thinly  scattered 

and  better  developed,  so  that  their  form  FiS-  432- 

can  be  distinctly  recognised.  Fig.  432 
shows  the  margin  of  such  an  etching 
from  the  Budapest  establishment  mag- 
nified 450  diameters.  The  predominant 
crystals  are  hexagonal,  and  quite  agree 
with  those  of  sodium  silicofluoride. 
Besides  there  are  long  crystals,  very 
similar  to  those  of  calcium  silicofluoride. 
That  the  crystalline  figures  are  elevated 
we  may  readily  learn  by  the  phenomena 
apparent  on  raising  or  lowering  the 
tube  of  the  microscope.  It  may  be  seen 
still  more  plainly  if  we  rub  the  matte 
plate  over  with  indian  ink  and  then 
wipe  it  superficially  with  elder  pith. 
All  the  parts  between  the  crystals  will 

then  appear  dark  under  the  microscope,  while  the  crystals  themselves  are  colourless. 
If  a  plate  of  potash  glass  is  etched  matte  there  will  appear  the  tesseral  crystals  of  potas- 
sium silicofluoride,  and  in  this  manner  potash  and  soda  glasses  might  be  respectively 
distinguished. 

The  etchings  are  the  most  delicate  in  presence  of  potassium  salts.  If  ammonium 
salts  are  used  the  solution  should  be  saturated ;  less  concentrated  for  sodium  salts  and 
more  dilute  for  potassium  salts.  In  all  processes  for  rapid  etching  ammonium  fluoride 
is  in  use,  and  we  may  easily  see  that  a  concentrated  solution  of  ammonium  fluoride, 
acidified  with  hydrofluoric  acid,  produces  a  fine  matte  in  a  few  seconds. 

As  regards  the  proportions  of  the  ingredients  in  the  mixing  baths,  we  can  lay  down 
definite  formula  only  if  the  glass  is  identical  in  composition.  In  practice  it  is  sufficient 
to  set  out  with  an  approximate  formula  for  glass — e.g.,  R2Si3O7,  when  R  is  a  monova- 
lent  metal.  The  reaction  then  ensues  according  to  the  equation : 

R2Si307  +  4F2HNa  +  loFH  =  SiF6R2  +  2SiF6Na2  +  6H2O. 

Hence  it  appears  that  for  the  complete  utilisation  of  the  sodium  fluoride  there  must 
be  present  a  considerable  quantity  of  free  hydrofluoric  acid.  But  as  this  hydro- 
fluoric acid  may  easily  prove  injurious,  it  is  better  to  use  some  other  acid  to  saturate 
the  bases. 

Acetic  acid  is  the  most  suitable,  as  it  does  not  decompose  the  acid  fluorides  and 
liberate  hydrofluoric  acid.     The  process  then  takes  place  according  to  the  equation  : 
R2Si307  +  9F2HNa  +  5C2H4O2  =  SiF6R2  +  2SiF6Na2  +  5C2H302Na  +  7H20. 

We  see  that  free  hydrofluoric  can  never  occur  in  this  process,  and  further,  that 
the  solubility  of  the  silico  fluoride  is  diminished  by  the  sodium  acetate  which  is  formed. 
From  the  last  equation  we  see  that  the  proportion  of  sodium  fluoride  to  acetic  acid  is 
93  :  5°>  °r  approximately  9:5.  On  the  basis  of  the  second  reaction  we  should  have 


628  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

the  following  composition  :  30  parts  hydrofluoric  acid  (50  percent.),  17  sodium  acetate 
and  soda-ash,  9  or  23-4  soda  crystals. 

Matte  etching  with  gaseous  hydrofluoric  acid  yields  very  unequal  results.  It  is  unfit 
for  surfaces,  and  can  serve  only  for  line-drawings. 

Sand-Blast  Machine. — C.  Tilghman,  in  working  glass,  uses  a  current  of  sand  pro- 
jected forcibly  against  the  surface  of  the  object  to  be  etched.  The  sand  derives  its 
velocity  from  air  or  steam.  Whilst  brittle  bodies  are  attacked  by  the  current  of  sand, 
elastic  bodies  are  able  to  resist  it,  and  hence  stencil-plates  of  caoutchouc  can  be 
applied  to  the  object.  The  parts  left  uncovered  are  ground  by  the  sand,  thus  forming 
a  design. 

EARTHENWAEE  OR  CERAMIC  MANUFACTURE. 

Weathering. — In  consequence  of  the  reactions  between  the  solid  crust  of  the  earth 
and  the  atmosphere  the  masses  of  rock  are  gradually  destroyed  and  broken  up.  The 
causes  of  this  weathering  are  partly  mechanical,  partly  chemical.  Among  the  former 
are  changes  of  temperature,  especially  frost,  the  mechanical  power  of  falling  water 
(rain,  streams,  &c.)  ;  the  chemical  includes  the  action  of  atmospheric  oxygen,  of  carbonic 
acid,  and  of  water. 

The  water  absorbed  by  rocks  becomes,  in  consequence  of  the  formation  of  ice  during 
the  cold  season,  a  powerful  agent  for  the  disaggregation  of  the  superficial  strata.  Of 
more  importance  are  the  chemical  changes  in  rocks ;  oxygen  converts  sulphides  into 
sulphates  and  ferrous  into  ferric  compounds.  Water  forms,  with  numerous  substances, 
hydrates  and  silicates,  with  an  accompanying  increase  of  volume,  and  converts 
anhydrite  into  gypsum.  By  the  prolonged  action  of  water  even  the  more  permanent 
minerals,  such  as  felspar,  are  decomposed  and  their  ingredients  are  rendered  soluble. 
Carbonic  acid  in  watery  solution  dissolves  the  carbonates  present  in  rocks  (iron-spar, 
limestone,  dolomite,  &c.)  and  phosphates  (apatite,  phosphorite).* 

The  final  result  of  weathering  is  always  mechanical  comminution  and  chemical 
decomposition  in  such  a  manner  that  a  portion  of  the  constituents  is  dissolved  in 
water.  The  residue  either  remains  in  heaps  at  the  place  where  it  was  formed,  or  it  is 
conveyed  away  and  subjected  to  a  process  of  elutriation  by  the  action  of  water,  the 
coarser  and  heavier  matter  being  separated  from  the  finer  and  lighter. 

Clays  and  their  Application.  Felspar. — To  the  most  important  alumina  combinations 
found  native  belongs  felspar.  This  mineral  is  one  of  the  chief  members  of  the  class 

containing  gneiss,  granite,  and  porphyry.    Potash-felspar,  j?,^  |08,  with  65-4  parts  of 

silica,  1 8  alumina,  and  16*6  potash,  is  also  known  as  orthoclase  or  adularia;  when 
sodium  takes  the  place  of  potassium,  the  felspar  albite  is  formed.  According  to 
Mitscherlich  some  felspars  contain  0*4  to  2*25  per  cent  of  barium.  When  felspar  is 
under  the  influence  of  water  and  carbonic  acid  with  changes  of  temperature,  it  loses  its 
potassium  silicate,  which  being  washed  out,  the  potash  is  taken  up  by  plants,  and  will 
perhaps  account  for  some  portion  of  the  potash  always  present  in  their  ash ;  some  of 
the  silicate  is  acted  upon  by  carbonic  acid,  by  which  the  silicic  acid  is  separated  and 
soluble  potassium  carbonate  formed.  In  following  this  decomposition  to  a  conclusion, 
we  may  surmise  that  the  silicic  acid  thus  set  free  becomes  a  constituent  of  the  opal  and 
chalcedony  spar.  All  clays  are  essentially  aluminium  silicate  ;  and,  in  many  instances, 
as  in  Devonshire  and  Cornwall,  the  change  from  felspar  of  the  fine  white  granite  to 
clay  by  disintegration  is  very  perceptible.  By  washing  this  clay  to  free  it  from  quartz 
and  mica  a  fine  white  clay  is  obtained,  known  as  kaolin  or  porcelain  clay.  Again,  by 

*  Biological  agents  take  a  part  in  the  work  which  is  not  yet  fully  recognised  ;  lichens  secrete 
oxalic  acid  and  corrode  the  rocks  upon  which  they  grow,  and  microscopic  plants  exert  a  more 
varied  and  profound  influence. 


SECT,  v.]          EARTHENWARE   OR  CERAMIC   MANUFACTURE. 

washing  with  potash  lye,  whereby  the  free  silica  is  taken  up,  there  is  obtained,  in  most 
cases,  a  fine  plastic  mass,  consisting  of  i  mol.  of  alumina,  i  mol.  of  silica,  and  2  mols. 
of  water.     The  quantity  of  free  silicic  acid  varies  between  i  and  14  per  cent. 
The  weathering  of  the  felspar  may  be  formulated  thus — 

i  mol.  felspar,  Si308KAl,  or 

gives,  under  the  influence  of  water, 

i  mol.  porcelain  clay,  2SiO4HAl,  and 

i     „     acid  potassium  silicate, 

the  latter  forming  a  soluble  combination  similar  to  water-glass.  Porcelain  clay  occurs 
in  the  following  localities: — i.  Bavaria:  Aschaffenburg,  Stollberg,  Diendorf,  Obereds- 
dorf .  2.  Prussia :  Mori  and  Trotha,  near  Halle  (material  for  Berlin  porcelain  manu- 
facture— decomposed  or  disintegrated  porphyry).  3.  Saxony:  near  Schneeberg  and 
Misnia.  The  first  is  a  weathered  granite ;  the  latter,  porphyry.  4.  Eastern  Hungary ; 
Brenditz  in  Moravia;  near  Carlsbad,  Bohemia;  Primdorf  in  Hungary.  5.  France; 
St.  Yrieux,  near  Limoges.  6.  England  :  St.  Austell,  in  Cornwall.  Weathered  granite : 
a  mixture  of  orthoclase  and  quartz.  It  is  found  chiefly  on  Tregoning  Hill,  near  Hel- 
ston.  7.  China.  It  naturally  follows  that  the  clay  should  contain  foreign  substances; 
and  it  is  from  the  quality  and  quantity  of  these  substances  that  the  several  varieties  of 
clay  are  obtained,  of  course  with  due  reference  to  the  chief  constituents — silicic  acid 
and  alumina.  The  purer  clays  contain  generally  the  following  foreign  substances : — 
Sand,  partly  as  quartz  sand,  as  potassium  silicate,  and  partly  as  particles  or  fragments 
of  undecomposed  minerals ;  baryta  combinations ;  magnesium  carbonate ;  calcium 
carbonate ;  ferric  oxide ;  sulphur  pyrites ;  and  organic  matter. 

In  the  examination  of  clays,  Seger  treats  the  sample  with  concentrated  sulphuric 
acid.  The  clayey  matter  is  decomposed,  while  quartz  and  felspar  remain  untouched. 
The  kaolins  named  below  have  the  following  composition :  — 


B 

B  . 

a  . 

- 

a 

a  • 

B  . 

•3  „ 

fj 

.§! 

5s 

•§43 

*l 

*l 

53* 

Components. 

.g-S 

"3  ° 

SB 

§2 

IN 

II 

|| 

M 

M 

W 

M 

MM 

M* 

£ 

88-26 

87-41 

QO*2Q 

96-55 

74*09 

78-5I 

6377 

54-92 

3-08 

6'4O 

4-08 

17*21 

20*QO 

8-66 

6'IQ 

5*63 

j.jr 

870 

O'W 

O"73 

21-56 

Composition  of  the  Clay  — 

Silica 

45-36 

4476 

45-98 

45-36 

45*63 

45-00 

45-30 

4?  "40 

Alumina  . 

39-58 

39-65 

3971 

38-08 

39-32 

37-15 

37-35 

0*92 

0*72 

0-73 

I'I3 

0-88 

°75 

I'29 

1-07 

Magnesia 

0'2O 

0-34 

0-45 

0-66 

0-28 

0-78 

073 

Potassa    . 

O'2I 

O'O2 

0-99 

1-24 

1-84 

o'53 

2  'O2 

2  '57 

Water       . 

I4-O2 

14-07 

13-28 

I3-32 

I3-32 

14-20 

I3-U 

1274 

Technical  Qualities  of  Clays, — For  the  technical  application  of  the  clays  the  im- 
portant qualities  are  colour,  plasticity,  and  hardening  well  under  heat. 

Colour. — Naturally  clays  are  white,  yellow,  blue,  or  green.  Pure  clay  is  white ; 
coloured  clays  are  the  result  of  several  admixtures.  White  clay  contains  but  a  small 
quantity  of  ferrous  oxide,  and  becomes  after  burning  yellow  or  red ;  these  colours  origi- 
nating from  the  organic  substances  disappear  on  their  being  volatilised  after  many 
firings.  The  coloured  clays  change  their  colour  during  firing,  becoming  red  or  red- 
yellow.  Fine  clays  are  prepared  only  from  those  becoming  white  by  continued 
burning. 

Plasticity. — The  clay  should  absorb  water  readily,  forming  a  tenacious  mass,  capable 
of  taking  sharp  and  clear  impressions.  It  is  evident  that  the  plasticity  of  the  clays 


630 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


depends  in  a  great  measure  on  their  composition.  Sand  is  the  constituent  most 
prejudicial  to  plasticity,  lime  less  so,  and  oxide  of  iron  least  of  all.  Clay  pos- 
sessing a  high  degree  of  plasticity  is  said  to  be  fat  or  long,  and  when  in  the  opposite 
condition  lean,  thin,  or  short.  All  shrunk  clays,  that  is,  all  clays  decreased  in  volume 
by  burning,  are  said  to  be  either  drawn  or  burst.  The  amount  of  shrinkage  depends 
of  course  upon  the  quantity  of  water  the  clay  contains ;  the  same  kind  of  clay  does 
not  always  exhibit  the  same  shrinkage.  Fat  clays  shrink  more  than  short  clays. 
The  diminution  in  surface  by  shrinkage  varies  between  14  and  31  per  cent,  the 
capacity  or  solid  contents  between  20  and  43  per  cent.  Clay  may  be  burnt  so  hard 
as  to  give  sparks  when  struck  with  steel ;  but  its  property  to  form  a  plastic  mass 
with  water  is  then  wholly  lost.  Pure  clay  (aluminium  silicate)  is  by  itself  infusible, 
but  by  mixture  with  lime,  ferric  oxide,  and  other  bases,  it  becomes  more  or  less  easily 
fusible.  According  to  the  experiments  of  E.  Bichters  (1868)  the  refractory  qualities 
of  clay  are  least  influenced  by  magnesia,  more  so  by  lime,  still  more  by  oxide  of  iron, 
and  most  by  potash.  Fusible  clay  obviously  is  not  adapted  to  the  manufacture  of 
porcelain  or  such  ware  as  is  likely  to  be  exposed  to  a  high  temperature.  A  fusible  and 
a  refractory  clay,  when  heated  together,  combine  into  a  mass  that  does  not  cleave  to  the 
tongue.  By  the  manufacture  of  clay  ware,  then,  is  understood  the  binding  of  certain 
clays  together  by  means  of  a  suitable  flux. 

Kinds  of  Clay. — The  clays  employed  in  ceramic  manufacture  are — 

1.  Refractory  clays;  as  porcelain  and  plastic  clays. 

2.  Fusible  clays ;  as  potter's  clay. 

3.  Limey  clays  ;  as  marl,  loam. 

4.  Ochre  clays ;  as  ruddle,  ochre. 

Of  these  porcelain  clay  is  the  most  important ;  it  is  of  various  colours,  very  tena- 
cious, plastic  to  a  high  degree,  burns  white,  and  is  not  fusible  in  a  porcelain-oven  fire. 
It  is  ordinarily  found  in  the  tertiary  formation,  almost  always  accompanied  by  other 
kinds  of  clay,  by  quartz-sand,  and  by  brown  coal.  For  practical  purposes  it  is 
important  to  know  that  clays  of  the  same  strata  and  of  the  same  pit  often  differ 
largely  in  their  refractory  property.  This  knowledge  is  not  only  the  result  of  experi- 
ence, but  of  a  lengthy  series  of  experiments  made  by  C.  Bischof ,  Otto,  and  Th.  Bichters. 
The  strata  near  Klingenberg-on-the-Maine,  at  Coblenz,  Cologne,  Laiitersheim,  and 
Vallendar-on-the-Rhine,  Weisbach  in  Baden,  Bunzlau  in  Silesia,  Schwarzenfeld  near 
Schwandorf,  and  Kemnath  in  Bavaria,  in  the  province  of  Hessen,  in  Saxony,  in 
Belgium,  near  Dreux  in  France,  and  Devonshire  and  Stourbridge  in  this  country,  are 
all  celebrated  for  this  clay. 

As  plastic  clays  may  be  mentioned  the  white  clays  of  Ebernhahn  (i),  Baumbach  (2), 
Bendorf  (3),  Lammersbach  (4),  and  Hohr  (5),  all  from  the  so-called  Kannenbackerland, 
Germany ;  as  well  as  a  lean  (6)  and  a  fat  (7)  white  clay  of  French  origin. 


Constituents. 

i. 

2. 

3- 

4- 

5- 

6. 

7- 

Clay  substance       .... 

Quartz    . 

3y  71 

54  73 

44  03 

71  54 

Feldspar  residues  

^4  °3 

4"7C 

57  X5 

31  42 

41  77 

52  77 

25  97 

Components  of  Clay  substance— 
Silica  . 

/J 

3° 

J4 

o5 

3-5° 

2  49 

Alumina 

47  44 

47  44 

47  39 

47  45 

•ti'StS 

45  '99 

~Q.~O 

4575 

Ferric  oxide 

37  2I 

T  •&% 

35  74 

36  40 

37  0° 

30  oo 

3577 

Lime 

1  o9 

i  94 

i  52 

i  41 

2  44 

2  94 

Magnesia    . 

^•cc 

Potassa 

0  73 

o  79 

i  -^r- 

0-51 

o  71 

A    -<~lS 

1-19 

Loss  on  ignition 

6  47 

4  22 

3  o5 

3  '9° 

2-36 

1-24 

y  °y 

9  52 

9  92 

13  70 

SECT,  v.]           EARTHENWARE   OR  CERAMIC   MANUFACTURE.  631 

The  chemical  composition  does  not  enable  us.  to  judge  of  the  sharply-marked 
differences  in  the  degree  of  plasticity,  which  is  very  low  in  kaolins  even  when  the 
proportion  of  pure,  hydrated  aluminium  silicate  is  high.  Hence  the  property  of 
plasticity  does  not  belong  to  any  peculiar  chemical  compound,  but  seems  to  fluctuate  in 
clays  of  similar  chemical  composition,  according  to  degree  of  mechanical  subdivision 
and  to  the  molecular  arrangement.  Possibly  the  degree  of  plasticity  may  be  determined 
by  the  structure  of  the  rocks  from  which  the  clay  has  originated. 

The  following  analyses  show  the  composition  of  certain  fire-clays  (refractory 
clays) : — 

i.  2.  3-  4.  5- 

Silica   .        .  .  47-50  ...  4579  ...  53-00  ...  63-30  ...  55-50 

Alumina       .  .  34-37  ...  28*10  ...  27-00  ...  23-30  ...  2775 

Lime    .        .  .  0-50  ...  2-00  ...  1*25  ...  073  ....  0*67 

Magnesia     .  .  i-oo  ...  ...  —  ...  —  ...  075 

Ferric  oxide  .  1-24  ...  6-55  ...  175  ...  1-80  ...  2-01 

Water.        »  .    .  i-oo  ...  16-50  .„  —  ...  10-30  ...  10-53 

i.  Almerode  in  Kurhessen  (crucible).  2.  Schildorf  near  Passau  (graphite  crucible). 
3.  Einberg  near  Coburg  (porcelain  capsule).  4.  Stourbridge.  5.  Newcastle  (fire- 
brick). 

The  composition  of  the  Stourbridge  fire-clay  will  be  seen  from  the  following 
analyses  by  Sir  F.  A.  Abel,  F.R.S.,  Chemist  to  the  War  Department : — 

Sample.  Silica.  Alumina.  Ferric  oxide.        Alkalies,  Waste,  Ac. 

1  .         .         .  66-47  •••  26-26  ...  6*63  ...  0-64 

2  ...  65-65  ...  26-59  ...  571  ...  2*05 

3  •  65-50  ...  27-35  ».  5'40  ...  175 

4  .        .         .  67.00  ...  25-80  ...  4-90  ...  2-30 

5  .        .  63-42  ...  31-20  ...  470  ...,  ,  o-68 

6  ...  65-08  ...  27-39  .-  3'98  ...  3'SS 

7  ...  65-21  27-82  ...  3-41  3-56 

8  .        .        .58-48  3578  ...  3-02  2-72 

9  ...  63-40  ...  3170  ...  3-00  ...  1-90 

The  sample  No.  9  containing  only  such  a  small  quantity  of  iron,  is  much  superior 
to  No.  i,  whose  refractory  properties  may  be  doubted.  The  clay  is  dug  from  pits 
varying  from  120  to  570  feet  in  depth.  It  is  generally  found  below  three  workable 
conl  measures,  between  marl  or  rock  and  an  inferior  clay.  The  seam  averages  3  feet 
in  thickness,  and  never  exceeds  5  feet,  while  the  middle  of  the  seam  contains  the  clay 
selected  for  crucibles,  &c.  Pot-clay  or  crucible-clay  only  occurs  in  small  quantities,  and 
costs  at  the  pit-mouth  553.  a  ton,  ordinary  fire-clay  only  realising  los.  a  ton. 

Potter's  Clay. — Ordinary  potter's  clay  also  possesses  most  of  the  properties  of  plastic 
clay;  many  varieties  form  with  water  a  similarly  tenacious  mass.  But  potter's  clay  is 
highly  coloured,  retaining  the  colour  after  burning.  It  effervesces  on  the  application 
of  hydrochloric  acid  and  forms  the  transition  to  marl.  It  follows  from  its  containing 
large  proportions  of  lime  and  oxide  of  iron  that  it  is  fusible,  and  melts  according  to 
the  quantity  of  these  constituents  at  a  higher  or  lower  temperature  into  a  dark  coloured, 
slag-like  mass.  It  is  found  in  the  last  formation,  or  entirely  on  the  surface  of  the 
earth,  and  sometimes  in  the  tertiary  formation.  It  contains  among  other  foreign 
substances  organic  matter,  iron  and  other  pyrites,  gypsum,  &c. 

fullers  Earth  is  a  soft,  friable  mass,  formed  by  the  weathering  of  diorite.  In 
water  it  falls  to  a  powder,  not  forming  a  plastic  pulp.  It  is  used  for  removing  grease- 
spots  from  paper,  &c.,  and  was  formerly  employed  in  fulling  cloth,  whence  its  name. 
It  is  also  used  in  paper-making,  and  as  an  addition  to  ultramarine.  It  contains 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


a  small  proportion  of  alkali,  but  its  detergent  action  depends  on  its  mechanical 
texture.* 

Marl. — Marl  is  a  mechanical  mixture  of  clay  and  calcium  carbonate,  containing 
sand  (sand-marl)  and  other  constituents;  that  containing  lime  is  called  lime-marl; 
that  clay,  clay-marl.  In  water  it  falls  to  powder,  and  forms  a  non-adhesive,  pasty 
mass.  With  acids  it  effervesces,  whereby  more  than  half  the  weight  is  lost.  It  melts 
easily.  It  is  found  in  the  lias  and  chalk  formation.  Its  chief  application  is  to  the 
improvement  of  land. 

Loam,. — Loam  may  be  considered  as  the  result  of  the  mixture  of  clay  with  sand. 
It  is  a  clay  more  or  less  mixed  with  quartz-sand  and  iron-ochre,  also  with  lime,  when  it 
assumes  a  yellow  or  brown  colour,  changing  on  burning  to  a  red.  It  forms  with  water 
a  slightly  plastic  mass,  and  is  not  very  refractory.  It  is  found  always  on  the  surface 
of  the  earth,  and  known  as  common  clay,  employed  in  the  manufacture  of  bricks,  coarse 
pottery,  &c.f 

Two  brick-clays,  belonging  to  the  cretaceous  formation,  near  Hanover,  had  the 
following  composition  when  dried  at  120° — 


Stocken. 

Lindener  Hill. 

Total. 

Insoluble  in  H2S04. 

Total. 

Insoluble  in  HaSO4. 

Si02 
A120S 

54  '01 
27-98 

18-81 
0-68 

59-91 
17-96 

37'i7 
1-79 

Fe20, 

2'IO 

trace 

1-09 

trace 

CaO 

2-85 

— 

8-21 

trace 

MgO 

0-65 

— 

0-41 

— 

Alkalies 

0-68 

— 

0-41 

— 

C02 

1-94 

— 

6-02 

— 

SO, 
H,0 

0-56 
9-03 

= 

0-46 
5'64 

— 

99-80 

19-69 

lOO'II 

39-30 

If,  according  to  Seger's  proposal,  we  consider  the  part  soluble  in  sulphuric  acid  as 
the  true  clay  substance,  and  consider  that  for  each  i  part  alumina  3-51  silica  belong  to 
the  felspar,  we  have  the  composition — 


Components. 

Stocken. 

Lindener  Hill. 

Quartz     

16*42 

•zo'QO 

3  '27 

8'4O 

80-31 

u  iyj 
DO  "7O 

Components  of  Actual  Clay  — 
Si02     

AvS-j 

37  "21 

Al,03    
Fe,O.   . 

33  '99 

2  '6  1 

26-46 
1*77 

CaO     
MgO    

3-55 
0*80 

1  3  '43 
0*67 

Alkalies       
CO,      . 

0-84 

0-67 

Q'8? 

SO.      . 

0*70 

O'73 

H,O      . 

ii  "26 

Q'23 

As  further  calcium  carbonate  and  sulphate  do  not  belong  to  the  true  clay,  and  as 
the  former  has  an  influence  on  the  burning,  they  are  to  be  mentioned  separately  : — 

*  It  is  found  near  Beigate  (Connonger's  Farm),  in  Surrey ;  near  Maidstone,  in  Kent ;  Woburn, 
in  Bedfordshire ;  Old  Town,  near  Bath ;  and  in  the  north-east  of  Ireland. 

f  In  horticultural  works  the  word  loam  is  used  in  a  totally  different  sense  to  signify  the  mass 
resulting  from  the  decomposition  of  grass  sods,  pared  off  from  the  ground  and  laid  up  in  heaps. 


SECT,  v.]          EARTHENWARE  OR  CERAMIC   MANUFACTURE. 


Components. 

Stocken. 

Lindener  Hill. 

Quartz 

16-42 

30-90 

Felspar  remains 

3'27 

8-40 

Calcium  carbonate  . 

4-45 

14-10 

„       sulphate    . 

0'95 

0-82 

Actual  clay 

74-9I 

46-78 

Components  of  Actual  Clc 

w— 

SiO2      . 

. 

46-96 

48-83 

ALjOg    . 

. 

36-42 

34-81 

Fe20t  . 

. 

2-80 

2'37 

MgO    . 

. 

0-87 

0-89 

Alkalies 

. 

0-91 

0-89 

H,0     . 

12-04 

I2'2I 

Certain  clays  contain  also  manganese,  cobalt,  barium,  titanium,  vanadium,  moly- 
bdenum, gold,  and  cerium. 

Behaviour  of  Clays  in  Working. — Clays  lose  their  water  partly  on  drying,  when  they 
undergo  a  linear  shrinkage  of  11-5  per  cent.,  and  partly  at  a  higher  temperature. 
On  losing  this  water  of  hydration  at  a  red  heat  clay  loses  permanently  its  plasticity 
and  forms  a  stony,  very  porous,  and  friable  mass.  At  higher  temperatures: it  becomes 
denser,  harder,  sonorous,  but  still  has  an  earthy  fracture.  The  silica  expels  the  car- 
bonic acid,  chlorine,  and  sulphuric  acid,  forming  silicates  with  the  alkalies,  lime, 
magnesia,  and  ferric  oxide.  These  silicates  form  with  the  aluminium  silicate  double 
silicates,  which  are  easily  fusible.  The  clay  sinters  more  and  more,  and  finally  melts. 
Though  the  specific  gravity  of  the  clayey  substance  rises  at  a  dull  red  heat  from  2-47 
to  2*70,  and  then  falls  at  a  white  heat  to  2-48,  the  density  of  the  entire  bricks  increases 
with  the  rise  of  temperature  by  the  loss  of  the  pores.  According  to  Karmarsch,  newly 
moulded  bricks  of  262  millimetres  long,  130  broad,  and  51  millimetres  thick,  shrink 
per  cent. : — 


Length. 

Breadth. 

Thickness. 

On  drying       
,,    drying  and  slight  burning        . 
„   burning  to  clinkers  . 

7-25 
8-50 

"75 

1075 
13-00 
23-00 

975 
1475 
1975 

Aron  observed  a  linear  shrinkage  of  from  0-3  to  4*1  per  cent,  at  redness,  and  of  12  to 
8  per  cent,  at  whiteness.  The  less  the  bricks  shrink  the  coarser  the  grains  of  sand 
which  they  contain. 

Experiments  by  Daube  show  how  much  the  porosity  and  the  resistance  of  bricks 
moulded  from  the  same  clay  depend  on  the  temperature.  The  results  are  given  in  the 
following  table : — 


Slightly 

Medium 

Hard 

burnt. 

burnt. 

burnt. 

Moisture  taken  up  on  dipping  in  water,  per  cent.  .  . 

16-2 
18-0 

16-5 
19-3 

16-4 
19*0 

1-6 
2-6 

O'7 

0*2 

0*15 

0*09 

8-5 

8-0 

7  '4 

2-5 

Do.  in  nitric  acid  
Increase  of  weight  in  sulphuric  acid  by  formation  of  CaSO4 

S'o 

1*2 

4'9 

I'2 

4-0 
0-9 

0-6 
0-8 

After  treatment  with  HC1  the  light-  and  medium-burnt  bricks  had  strong  fissures ; 
those  hard  burnt  only  fine  fissures,  and  the  clinkers  none  at  all. 

The  presence  of  calcium  carbonate  in  fragments  or  coarse  grains  is  very  injurious 
in  fire-clays.  According  to  Seger  clays  are,  indeed,  used  containing  as  much  as 


634  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

30  per  cent,  of  calcium  carbonate,  but  such  clays,  especially  if  lightly  burnt,  have  a 
great  tendency  to  weather.  This  explains  why  the  clays  which  burn  red  and  which 
contain  little  or  no  calcium  carbonate  are  preferred  for  roofing  tiles,  whilst  the 
calcareous  clays  which  burn  yellow  have  been  found  quite  useless.  Calcareous  clays 
are,  indeed,  easier  to  work,  but  as  they  lose  in  burning  not  merely  water  but  carbon 
dioxide,  they  yield  porous  bricks.  The  temperature  at  which  the  pores  are  closed  and 
a  dense,  porcelain-like  mass  is  produced,  lies  very  near  to  that  at  which  the  mass  melts 
to  a  slag,  and  great  experience  is  necessary  to  prevent  the  bricks  from  slagging. 
Hence,  in  burning  such  clays  it  is  necessary  to  avoid  a  strong  heat.  The  bricks  in 
consequence  retain  their  porosity  and  absorb  water  eagerly.  A  really  weather-proof 
brick  cannot  be  obtained  from  clays  which  contain  upwards  of  10  to  15  percent,  calcium 
carbonate. 

Changes  of  Colour  in  Burning. — Considerable  importance  often  attaches  to  the 
property  of  calcium  carbonate  to  give  a  yellow  or  yellowish-green  colour  on  burning  to 
the  common  ferruginous  clays.  Whilst  pure  clay  burns  white  it  is  turned  a  red  by 
ferric  oxide,  the  darker  as  the  heat  applied  is  stronger.  If  the  heat  is  still  raised 
the  colour  becomes  greenish,  and  finally  black,  according  to  Kemole,  by  the  partial 
formation  of  ferrous  oxide.  If  the  ferruginous  clay  contains  at  the  same  time  calcium 
carbonate  it  will  be  red,  if  slightly  burnt,  flesh-coloured,  whitish  to  dark  yellow  at 
incipient  sintering,  owing  to  the  formation  of  a  yellowish  basic  silicate  of  lime  and 
ferric  oxide,  and  green  to  black  on  full  nitrification.  According  to  Seger  this  yellow 
colour  appears  distinctly  if  to  every  per  cent,  of  ferric  oxide  the  clay  contains  at  least 
3  to  3 £  per  cent,  calcium  carbonate.  The  yellow  colour  appears  at  a  lower  temperature 
and  is  lighter  the  more  the  proportion  of  calcium  carbonate  exceeds  this  minimum, 
appearing  at  a  higher  temperature  and  verging  more  upon  a  yellowish-red  or  yellowish- 
brown  on  approaching  the  proportion  above  given.  If  the  amount  of  lime  is  still 
lower  it  merely  reduces  the  red  without  producing  a  yellow. 

Efflorescences. — After  a  time  bricks,  especially  if  lightly  burnt,  often  show  whitish, 
yellow,  green,  and  even  black  eruptions.  White  eruptions  generally  consist  of  magne- 
sium, calcium,  and  sodium  sulphates,  sodium  chloride  or  bicarbonate,  which  are  either 
present  in  the  clay  or  have  been  introduced  by  the  water,  the  mortar,  or  the  cement. 

Green  eruptions  upon  light-coloured  bricks  in  moist  places  consist  chiefly  of  algae, 
or  they  may  be  due  to  the  presence  of  chrome.  Facing-bricks  made  of  the  lignitic 
clays  near  Wittenberg,  displayed,  sometimes  on  their  entire  surfaces,  sometimes  only 
in  spots,  especially  at  the  corners,  a  very  intense  golden-yellow  colour,  which  if 
examined  with  a  lens  was  found  to  consist  of  mammillary  protuberances,  in  part  of  a 
bright  grass-green  or  yellowish-green.  Some  such  bricks  contained  o'i  6  per  cent,  of 
soluble  salts,  consisting  of  : 


Potassa 19-82 

Soda 3-17 

Lime  ......       3*24 

Magnesia 3*34 

Alumina  and  ferric  oxide    .         .       077 
Vanadic  acid       .        .        .        .29-43 


Molybdic  acid  .  .  ;  .  1-12 
Sulphuric  acid  .  .  .  .15-70 
Silica  ......  2-07 

Chlorine 2-63 

Water 18-25 

Insoluble  matter          .        .         .       0-46 


These  coloured  eruptions  consisted,  therefore,  chiefly  of  potassium  vanadate,  the 
yellow  colour  of  which  is  partially  modified  to  green  and  blue  by  molybdic  acid. 
Reducing  combustion  gases  and  high  temperatures  make  the  vanadium  compounds 
insoluble. 

Black  spots  are  due  chiefly  to  fungi,  which  attach  themselves  where  calcium  car- 
bonate and  sulphate  effloresce  out  of  the  brickwork. 

In  addition  to  the  composition  of  the  clay  and  the  temperature  of  the  kilns,  the 
nature  of  the  combustion  gases  has  an  influence  upon  the  colour  of  the  bricks. 


SECT,  v.]  EARTHENWARE  OR  CERAMIC  MANUFACTURE.  635 

Seger  showed  that  the  dark-red  colour  of  the  surface  of  yellow  bricks  is  occasioned 
by  the  absorption  of  sulphuric  acid  from  the  sulphur  of  the  fuel.  The  moisture 
precipitated  from  the  combustion-gases  of  the  Berlin  Porcelain  Works  contained  per 
litre : 

Wood  furnace.  Gas  furnace. 

Hydrochloric  acid 39  ...                114 

Sulphuric  acid 153  ...                384 

Phosphoric  acid 73 

Ferric  oxide  and  alumina 8  ...                  17 

Lime II  ...                  39 

Magnesia 8  ...                  18 

Potassa)  _                                     37 
Soda      )     '                                                                                                               106 

Ammonium  chloride  .......  —  ...                  47 

At  higher  temperatures,  and  on  exposure  to  the  action  of  reducing  gases,  the  sul- 
phuric acid  is  expelled  and  the  normal  colour  restored.  A  yellow  brick  which  had 
been  ignited  to  redness  was  uniformly  yellow  within,  but  was  dark-red  on  those  parts 
of  the  surface  which  had  been  most  exposed  to  the  combustion-gases.  The  red  colour 
had  only  penetrated  into  the  brick  to  the  depth  of  2  to  3  millimetres.  A  comparative 
analysis  of  the  red  (I.)  and  the  yellow  (II.)  parts  showed : 

i.  n. 

Silica 53-96  57-55 

Alumina .         .        .     10-29  •••  11-98 

Ferric  oxide        .         .        .        .  .        .         .       6-25  ...  10-05 

Magnesia .        .         .176  ...  1-51 

Lime  .        .         . 16*70  ...  17*85 

Sulphuric  acid ino  ...  o-88 

Some  red  colorations  seem  to  be  due  to  volatile  compounds  of  iron. 

The  action  of  the  other  constituents  of  the  combustion-gases  upon  the  colour  of 
clays  has  been  examined  by  Seger. 

Clays  containing  iron  and  lime,  and  burning  yellow  if  the  combustion-gases  con- 
tain an  excess  of  oxygen,  are  turned  at  a  red  heat  a  dirty  red  colour,  then  flesh  colour,  and 
at  full  redness  yellow  with  a  brownish  cast.  Reducing -gases  (hydrogen,  hydrocarbons, 
carbon-moncxides)  effect  a  blackening  which,  on  access  of  air,  gives  place  to  redness. 
After  a  preceding  reduction,  the  colours  produced  by  the  action  of  oxygen  are  lighter, 
and  incline  more  to  a  whitish  or  yellowish-green  than  if  there  had  been  no  previous 
reduction.  An  occasionally  reducing  flame  in  the  furnace  contributes  to  develop  the 
light  colour  of  the  calcareous  clays.  Ferruginous  clays  free  from  lime  turn  to  a  pure 
red  in  an  excess  of  oxygen,  this  the  more  decidedly  the  higher  the  temperature. 
Reducing-gases  change  this  red  colour  to  a  velvet  black  by  the  reduction  of  the  ferric 
oxide  to  ferrous  oxide  and  metallic  iron.  If  such  black  bricks  are  ignited  in  the  air 
the  red  colour  returns,  but  not  so  finely  as  with  an  exclusively  oxidising  flame,  so  that 
here  to  obtain  pure  colours  the  action  of  reducing-gases  must  be  avoided.  Clays  free 
from  lime  and  poor  in  iron,  and  turning  white  or  yellow,  are  also  blackened  by  the 
action  of  reducing-gases.  The  clay  of  Greppin,  on  exposure  to  pure  hydrogen,  after 
ignition  to  dull  redness,  became  a  light  ash  grey,  and  contained  1*69  per  cent,  ferric 
oxide  and  i-oi  per  cent,  ferrous  oxide,  after  prolonged  heating  to  bright  redness  it 
was  a  dark  ash  grey,  and  contained  r8i  per  cent,  ferric  oxide  and  0-34  metallic  iron. 
This  grey  colour  very  quickly  disappears  again  on  the  admission  of  air,  but  the  original 
colours  return,  only  in  a  much  fainter  degree.  The  flesh  colour  which  characterises  the 
lower  temperatures  is  converted  into  a  whitish  yellow,  whilst  at  stronger  heats  there 
appears  a  pure  yellow.  Clays  poor  in  iron,  which  burn  white  in  an  excess  of  oxygen,  are 
turned  light  grey  by  reducing-gases,  and  on  ignition  in  the  air  they  become  white  again. 

Infusibility, — C.  Bischof  and  Seger  have  made  comprehensive  experiments  on  the 


636 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


influence  of  the  composition  of  a  clay  upon  its  behaviour  at  high  temperatures. 
Bischof  holds  that  the  fusion  of  clays  consists  in  the  formation  of  double  silicates  and 
aluminium  silicates  on  the  one  hand,  and  a  silicate  on  the  other  which  may  have  for 
its  base  either  magnesia,  lime  or  iron,  potassa  or  soda.  Pure  aluminium  silicate  is 
infusible  in  our  ordinary  fires,  especially  if  it  contains  alumina  in  excess.  If  one  of 
the  above-mentioned  bases  is  present,  its  fusibility  increases  with  the  quantity  of  the 
base.  If  we  calculate  from  the  complete  analysis  of  a  clay  how  much  alumina  comes  to 
one  equivalent  of  fluxing  agent,  and  how  much  silica  comes  to  one  equivalent  alumina, 
the  quotient  obtained  by  dividing  the  latter  value  by  the  former  will  be  proportional  to 
the  infusibility.  On  the  other  hand,  Seger  maintains  that  if  it  were  possible  to  infer 
the  fusibility  of  a  clay  from  its  composition,  this  could  be  practicable  only  if  it  could  be 
brought  into  a  chemically  homogeneous  mass. 

For  the  experimental  determination  of  the  behaviour  of  a  clay  under  heat,  specimens 
must  be  ignited.  For  this  purpose  Seger  recommends  the 
Deville  furnace,  Fig.  433.  In  it  there  is  laid  a  thick  wrought- 
iron  plate  B,  beneath  the  hollow  fire-clay  cylinder  A ,  which  is 
surrounded  with  a  sheet-iron  screen.  The  cylinder,  1 1  centi- 
metres in  width  and  20  centimetres  in  height,  is  continued  by 
a  fire-clay  cap  C,  likewise  enclosed  in  iron.  The  plate  B  is 
perforated  in  three  concentric  rings,  with  apertures  of  5  to  6 
millimetres  in  width,  a.  In  the  middle  is  a  large  hole,  b,  of 
30  millimetres  in  width.  The  lower  part  of  the  sheet-iron 
screen  is  closed  below  with  a  round  iron  plate,  D,  which  can 
be  luted  on  air-tight  with  clay.  The  air  forced  in  through 
the  pipe,  c,  enters  the  fire-box  through  the  holes,  a  a,  whilst 
the  wider  aperture,  6,  serves  to  receive  the  support  of  the 
crucible,  which  for  this  purpose  has  a  plug-like  elongation 

below,  fitting  into  b.  The  same  aperture  serves  to  clean  out  the  furnace  after  use. 
On  the  support  stands  a  crucible  of  40  millimetres  outside  diameter  and  45  millimetres 
height,  also  centred  with  a  small  plug  at  the  bottom.  This  crucible  receives  the 
samples  of  clays  to  be  tested,  together  with  the  normal  clays,  made  up  in  the  form 
of  small  tetrahedral  or  prismatic  pieces.  The  crucible,  its  support,  and  the  cylinder 
are  all  made  of  a  mixture  of  equal  parts  of  Zettlitz  kaolin  and  Neuroda  slaty  clay.  Along 
with  the  cones  a  piece  of  platinum  wire  is  placed  in  the  crucible.  Some  burning  charcoal 
is  placed  in  the  furnace  and  retort-graphite  from  the  gasworks,  which  is  preferable  to 
coke  on  account  of  its  small  yield  of  ashes.  Air  is  forced  in  at  c  until  the  melting- 
point  of  platinum  is  reached.  The  appearances  presented  by  the  clays  are  then 
examined,  and  their  position  with  respect  to  the  normal  samples  is  determined. 

As  a  scale,  Bischof  uses  a  series  of  neutral  clays,  the  slatey  clay  of  Saarau,  the  kaolin 
of  Zettlitz,  the  clays  of  Stroud-Maiseroul,  Mulheim,  Griinstadt,  Oberkaufungen,  and 
Niederpleis.  A  further  normal  point  is  the  fusion  of  platinum  to  boiling.  The  standard 
clays  of  the  quality  used  by  Bischof  cannot  be  obtained  by  purchase.  The  fusion  of. 
platinum  gives  no  certain  indication,  for  platinum,  like  iron,  can  under  certain  circum- 
stances absorb  carbon  from  the  combustion-gases  and  thus  alter  its  melting-point. 
Seger,  on  the  other  hand,  has  prepared  tetrahedra  of  definite  composition,  which  are 
to  be  obtained  at  any  time  from  the  Royal  Porcelain  Works  at  Charlottenburg. 

The  Production  of  Earthenware. — The  assertion  of  the  Chinese  that  they  had 
invented  porcelain  3000  years  ago  is  scarcely  accurate.  It  is  first  mentioned  in  the 
ninth  century  under  the  name  Yao.  A  century  later  they  learnt  the  use  of  a  blue  colour 
underneath  the  glaze.  This  improvement  appeared  of  such  importance  that  porcelain 
so  adorned  was  reserved  for  the  exclusive  use  of  the  Emperor.  No  one  was  allowed  to 
buy  such  porcelain  articles,  or  even  to  look  at  them  !  In  the  thirteenth  century 


SECT,  v.]          EARTHENWARE   OR  CERAMIC   MANUFACTURE.  637 

porcelain  vessels  were  first  decorated  with  turquoise,  yellow,  and  violet,  on  coloured 
grounds,  and  even  with  painted  designs.  Under  the  Emperor  Ching-hoa  (1465-1488) 
a  method  was  discovered  of  decorating  glazed  porcelain  vessels  with  coloured  designs, 
often  with  splendid  paintings,  in  which  a  green  colour  predominated.  In  the  fifteenth 
period,  down  to  1726,  a  purple-red  pigment  was  introduced.  But  towards  the  end  of 
this  period  the  keramic  art  of  China  began  to  decline.  Their  material  is  still,  however, 
excellent  in  quality,  though  the  Japanese  have  outstripped  them  in  the  decoration  of 
their  earthenware.  Satsuma,  especially,  produces  splendid  vases. 

Classification  of  Earthenware. — Clay  ware  is  generally  separated  into  dense  and 
porous  ware.  The  dense  ware  is  so  strongly  heated  that  half  its  mass  is  lost ;  its 
fracture  is  glazed  and  conchoidal ;  it  is  translucent  and  compact,  being  impenetrable  to 
water ;  and  it  gives  a  spark  when  struck  with  steel.  Porous  clay  ware  is,  in  the  mass, 
not  glazed,  its  fracture  open  and  earthy ;  and,  when  not  superficially  glazed,  water  freely 
percolates  through  it.  It  also  clings  to  the  tongue.  The  burnt  mass,  whether  dense  or 
porous  ware,  either  remains  rough  or  is  glazed. 

The  following  are  the  essential  varieties  of  clay  ware : — 

I.  Dense  Clay  Ware, — A.  Hard  porcelain.     The  mass  equal  throughout ;  not  in- 
dented with  a  knife  ;  fine-grained,  translucent,  sonorous,  and  white.     Fracture,  fine- 
grained, and  conchoidal.     Sp.  gr.  =  2 '07  to  2-49.     It  may  be  considered  as  composed 
of  two  substances — namely,  a  natural  clay  or  true  kaolin,  infusible,  and  preserving 
its  whiteness  imder  a  strong  heat ;  and  a  flux  consisting  of  silica  and  lime,  or  felspar 
with  or  without  gypsum,  chalk,  and  quartz.     The  glazing  is  essentially  due  to  this  flux, 
and  not  to  lead  or  tin  oxide.     It  is  characteristic  of  the  manufacture  of  hard  porce- 
lain that  the  burnings  are  concluded  in  one  operation. 

B.  Soft  or  tender  porcelain.     The  mass  more  easily  fluid  than  hard  porcelain.  Two- 
kinds  are  known : — 

a.  French  porcelain,  a  glass-like  mass,  essentially  a  potassuim-aluminium  silicate, 
prepared  with  the  addition  of  clay,  therefore  erroneously  termed  a  clay  ware,  and 
containing  lead  similarly  to  crystal  glass. 

ft.  English  soft  porcelain.  The  mass  similar  to  kaolin,  plastic,  remaining  white 
when  burnt  (pipe-clay).  It  is  made  with  a  vitreous  grit,  consisting  of  gypsum,  Cornish 
stone  (weathered  pegmatite),  bone-ash  (essentially  calcium  phosphate),  in  very  varied 
proportions.  The  glaze  is  obtained  by  pulverised  Cornish  stone,  chalk,  powdered  fire- 
clay, and  borax,  mostly  with,  seldom  without,  the  addition  of  lead  oxide.  The  glazing, 
is  a  second  process. 

C.  Statue  porcelain,  or  biscuit  ware : — 
a.  Genuine  and  unglazed  porcelain. 

ft.  Parisian  porcelain,  or  parian.  Unglazed  statue  porcelain  is  similar  to  English 
porcelain. 

y.  Carrara,  less  translucent  than  parian,  and  sometimes  of  a  whiter  colour. 

D.  Stone  ware.     Dense,  sonorous,  fine-grained,  homogeneous,  only  slightly,  if  at  all, 
translucent,  white  or  coloured. 

a.  Glazed  porcelain  stoneware.  Plastic,  remaining  white  after  burning,  slightly 
refractory  with  the  addition  of  kaolin  and  fire-clay ;  a  felspar  as  flux  ;  the  glaze  con- 
tains borax  and  lead  oxide. 

ft.  White  or  coloured  unglazed  stoneware.     Wedgwood  ware. 

y.  Common  stoneware  (salt-glazed).  No  fluxing  material  is  employed,  but  the 
firing  is  increased.  Glazed  with  siliceous  soda-alum. 

II.  Porous  Clay  Ware. — A.  Fine   Fayence  with   transparent  glaze.      The  body 
earthy,  clinging  to  the  tongue,  non-transparent,  sometimes  sonorous ;  the  glaze  con- 
taining lead,  borax,  felspar,  &c. 

B.  Fayence,  with  non-transparent  glaze.     The  body  of  a  yellow  burnt  potter's  clay 


638  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

or  clay-marl,  with  non-transparent  white  or  coloured  glaze  or  enamel,  containing  tin. 
To  this  class  belongs  majolica,  delft  ware,  &c. 

C.  Ordinary  potter's  ware.     The  body  of  ordinary  potter's  clay,  or  clay-marl,  red, 
coloured,  soft,  and  porous.     Mostly  glazed  with  lead,  the  glaze  being  always  non-trans- 
parent.    According  to  the  colour  of  the  glaze,  the  ware  is  distinguished  as  white  and 
brown. 

D.  Plate,  terra-cotta,  fire-clay  ware,  tubes,  ornaments,  vases,  &c.  The  body  earthy  ; 
mostly  more  or  less  unequal ;  always    coloured,  porous,   easily  fluid,   and    slightly 
sonorous.     Is  not  usually  glazed. 

I.  Hard  Porcelain. — Grinding  and  Mixing  the  Material. — Hard  porcelain  is  composed 
of  a  mixture  of  colourless  porcelain  clays  with  felspar  as  a  flux,  which  sometimes  is  com- 
posed of  quartz,  chalk,  or  gypsum.  The  porcelain  clay,  in  itself  infusible,  and  becoming 
in  the  fire  only  an  earthy,  opaque  mass,  when  intimately  mixed  with  the  flux  material, 
melts  easily  at  a  higher  temperature  than  that  of  the  glass  oven.  The  materials  of 
porcelain  manufacture  are  not  found  native  in  such  a  condition  that  they  may  at 
once  be  employed ;  they  must  be  ground  to  a  fine  powder,  and  this  washed  to  separate 
the  foreign  substances.  Pure  kaolin,  however,  is  not  utilisable  in  porcelain  manufac- 
ture, as  it  becomes  much  decreased  in  volume  on  the  application  of  heat.  It  is  there- 
fore mixed  with  fine  washed  quartz  sand,  although  this  addition  somewhat  impairs  the 
plasticity.  This  mass  on  treatment  with  fire  would  be  porous,  and  felspar  is  added 
to  close  the  pores  and  to  form  a  binding  glass.  The  proportions  in  Berlin 
porcelain,  according  to  G.  Kolbe(i863),  are66'6  parts  silica,  28*0  parts  clay,  0*70  part 
ferrous  oxide,  o'6  part  magnesia,  and  0*3  part  lime. 

Proportions  of  the  material  as  employed  at — a.  Nymphenburg ;  /3.  Vienna ; 
y.  Meissen : — 

a.  Kaolin  from  Passau 65 

Sand  therewith .....4 

Quartz         •'-.  J  X.     .V-    li*  *"• 2I 

Gypsum         * 5 

Broken  biscuit  ware 5 

b.  Kaolin  from  Zedlitz 34 

Kaolin  from  Passau 25 

Kaolin  from  Unghvar 6 

Quartz 14 

Felspar 6 

Broken  ware 3 

e.  Kaolin  from  Aue 18 

Kaolin  from  Sosa 18 

Kaolin  from  Seilitz       . 36 

Felspar          .        .        .     '  .        .        . 26 

Broken  ware 2 

The  mixture  of  the  materials  in  the  required  proportion  takes  place  in  large  vats, 
whence  the  thin  pulp  is  pumped  and  forced  through  sieves  into  another  vessel. 

Drying  the  Mass. — After  the  water  is  removed  from  the  sediment  at  the  bottom  of 
the  vat  or  tank,  the  clay  appears  as  a  slime,  which  has  to  be  dried  to  the  required  con- 
sistency. The  drying  or  evaporation  of  the  water  is  effected  in  wide  wooden  tanks 
exposed  to  a  strong  current  of  air.  This  is  a  very  general  method  of  drying  the  mass, 
but  can  only  be  employed  during  the  summer  months  on  account  of  the  dampness  of 
our  climate.  It  is  not,  therefore,  sufficiently  extensive  for  large  manufacturers,  and 
consequently  other  means  of  drying  are  resorted  to — usually  by  means  of  absorption, 
the  mass  being  laid  on  a  porous  layer  of  burnt  lime,  gypsum,  &c.  Drying  by  means  of 
gypsum  is  expensive,  as  it  soon  becomes  hardened,  and  has  to  be  removed.  The  mass 
can  also  be  dried  by  means  of  air  pressure,  being  in  this  case  placed  in  flat  porous  boxes, 


SECT,  v.]        EARTHENWARE   OR   CERAMIC   MANUFACTURE.  639 

under  which  a  vacuum  chamber  is  situated.  Talbot's  apparatus  is  formed  on  this  prin- 
ciple. In  Grouvelle  and  Honore's  system  of  drying,  the  water  is  first  partially  removed, 
by  means  of  draining  over  gypsum,  and  the  mass  is  then  put  into  firm  hempen  sacks, 
which  are  subjected  to  pressure  in  a  screw  or  lever  press.  Pressed  clay  has  greater 
plasticity  than  that  dried  by  artificial  heat ;  but  the  method  is  expensive,  as  the  sacks 
soon  require  replenishing,  being  speedily  worn  out  by  the  constant  pressure. 

Kneading  the  Dried  Mass. — When  the  mass  is  dried  by  pressure  or  by  absorption, 
the  water  in  all  cases  is  not  equally  expelled,  and  there  are  also  air-bubbles  which  must 
be  removed.  This  is  done  by  kneading  and  treading  the  mass  with  the  feet  and  hands, 
and  by  this  means  also  the  plasticity  of  the  mass  is  improved.  Another  method  of 
improving  the  plasticity  is  by  allowing  the  moist  clay  to  stand  till  it  becomes  putrid. 
Stagnant  water  is  often  employed.  Brongniart  explained  the  action  of  this  rotting,  as 
it  is  termed,  to  be  that  gases  were  formed  in  the  body  of  the  clay,  and  that  by  the  con- 
tinuous movement  caused  in  their  endeavour  to  escape,  the  finest  particles  of  the 
materials  were  intimately  mixed.  Salvetat  gives  the  following  hypothesis  : — By  the 
rotting  there  is  formed  in  the  mass  a  large  quantity  of  sulphuretted  hydrogen  gas. 
This  gas  effects  the  reduction  of  the  alkaline  sulphides  to  calcium  sulphides  under 
the  influence  of  the  organic  substances,  the  calcium  sulphide  being  set  free,  a  similar 
action  taking  place  with  the  carbonic  acid  in  contact  with  the  air.  The  bleaching  of 
the  mass  on  exposure  to  the  air  is  due  to  the  oxidation  of  the  black  iron  sulphide 
to  iron  sulphate,  which  is  removed  by  washing.  The  decomposition  of  the  felspar 
constituents  may  also  ensue  from  the  long-continued  action  of  the  water.  Ac- 
cording to  E.  von  Sommaruga,  of  Vienna,  the  existing  sulphates  are  decomposed  by 
the  air  into  sulphuretted  hydrogen  and  carbonates,  and  these  being  removed  with  the 
water,  the  refractory  nature  of  the  clay  is  improved. 

The  Moulding. — The  kneading  and  rotting  accomplished,  the  porcelain  mass  is  taken 
to  another  room  to  be  moulded.  This  is  effected  either  on  a  potter's  wheel  or  in  a  mould. 
The  Potter's  Wheel. — The  potter's  wheel  consists  of  a  vertical  iron  axis,  on  which  a 
horizontal  solid  wheel  is  fixed,  and  caused  to  revolve  by  the  feet  or  by  steam-power, 
the  motion  in  the  latter  case  being  regulated  by  the  feet.  A  lump  of  clay  is  laid 
upon  the  wheel,  the  thumb  being  placed  in  the  centre  of  the  lump  and  pressed  down- 
wards ;  a  hollow  is  thus  formed,  which  is  widened,  or  the  walls  continued  vertically 
according  to  the  shape  of  the  vessel  to  be  made.  The  constant  revolution  of  the  wheel 
easily  allows  the  moulder  to  obtain  a  perfectly  cylindrical  form.  By  thus  humouring 
the  clay,  elongating  the  vessel,  again  depressing  it,  widening  it,  and  by  continued 
manipulation  in  this  manner,  the  most  exquisite  shapes  are  produced.  To  form  the 
ridges  or  sharp  edges  of  the  vessel  a  small  piece  of  iron,  a  strip  of  horn  or  wood, 
termed  a  bridge,  is  used.  The  perfectly  formed  vessel  is  cut  away  from  the  wheel  by 
.a  piece  of  brass  wire. 

Moulding  in  Plaster  of  Paris  Forms. — A  mould  is  first  taken  from  the  pattern  or 
original  object,  which  may  be  of  clay,  wax,  gypsum,  or  metal.  The  moulding  is 
performed  with  dry  material,  with  clay  of  the  consistency  of  dough,  or  with  fluid  clay. 
The  moulds  must  possess  a  certain  amount  of  elasticity,  and  be  porous  in  order  to 
absorb  the  moisture  expressed.  For  these  reasons  plaster  of  Paris  is  generally  used. 
The  mould  is  taken  from  the  original  article  in  parts,  which  are  trimmed  to  fit  together 
accurately ;  into  each  part  is  then  pressed  sufficient  clay  to  fill  the  indentations  of  the 
pattern,  more  clay  being  added  till  a  proper  thickness  is  obtained.  The  parts  are  then 
fitted  together,  and  the  moulds  left  for  some  time.  This  method  of  moulding  is  some- 
times called  presswork,  and  is  adapted  to  all  kinds  of  pottery  not  of  circular  form. 
Plates,  cups,  and  dishes  are  also  made  in  a  similar  manner.  A  leaf  of  clay  is  rolled 
out  and  pressed  between  flat  moulds.  Sometimes,  instead  of  rolling,  the  clay  is  beaten 
•out  with  a  wooden  hammer  covered  with  leather. 


640  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

Casting. — Moulding  porcelain  articles  out  of  thin  pulpy  clay  is  one  of  the  most 
ingenious  arts  of  the  potter.  The  fluid  clay  is  poured  into  porous  moulds,  which 
absorb  a  portion  of  the  water,  thereby  reducing  the  pulp  to  a  certain  consistency. 
The  interior  pulp  remaining  fluid  is  now  poured  out,  and  the  cast  or  coating  of  clay 
adhering  to  the  mould  allowed  to  harden.  When  sufficiently  hard  the  vessel  is  taken 
to  the  lathe  to  be  finished,  or  if  not  of  circular  form,  to  the  finishing  room,  where  with 
sharp  tools  any  required  pattern  is  cut,  or  handles,  spouts,  &c.,  which  have  been  made 
in  separate  moulds,  attached. 

Preparation  of  Porcelain  Articles  without  Moulds. — The  finest  porcelain  is  finished 
by  hand,  as  machinery  or  moulds  could  not  give  sufficient  sharpness  to  the  beautiful 
flowers  and  figures  sculptured  on  vases,  &c.  The  flowers,  &c.,  are  first  prepared  in 
moulds,  are  then  attached  to  the  body  of  the  article,  and  finally  are  finished  off  with 
edged  tools.  The  stalks  of  the  flowers  are  sometimes  formed  on  wire ;  and  the  leaf  in 
first  roughly  constructed  in  the  palm  of  the  hand,  the  furrowing  and  veining  being 
done  afterwards.  The  texture  of  drapery  is  imitated  by  means  of  a  piece  of  tulle, 
which  is  laid  on  the  clay,  and  allowed  to  dry.  During  the  burning  the  tulle  is  con- 
sumed, leaving  the  pattern  on  the  porcelain. 

Drying  the  Porcelain. — After  the  porcelain  ware  is  formed  it  is  dried  for  some 
time  at  the  ordinary  temperature.  This  is  continued  till  the  clay  contains  no  moisture, 
that  is,  until  its  weight  is  tolerably  constant.  During  this  drying  the  clay  is  said  to 
be  in  the  green  state,  and  possesses  a  greater  tenacity  than  it  has  in  any  of  the  former 
processes. 

Glazing. — Only  very  few  articles  of  porcelain  ware,  generally  statues  or  figures, 
remain  unglazed ;  these  are  termed  biscuit  ware.  All  other  articles  are  glazed.  The 
glazings  employed  are  of  four  kinds : — (i)  Earth  or  clay  glazings  are  transparent,  and 
formed  by  melted  silica,  alumina,  and  alkalies;  they  easily  become  fluid,  and  melt 
about  the  temperature  at  which  the  vessels  are  baked.  This  kind  of  glazing  is  used 
for  hard  porcelain.  (2)  Lead  glazes  are  transparent  glazes  containing  lead ;  most  of 
these  melt  at  the  temperature  at  which  the  articles  are  burnt.  (3)  Enamel  glazes  are 
partly  white,  partly  coloured  opaque  glasses  containing  tin  oxide  besides  lead  oxide. 
This  kind  of  glaze  is  easily  melted,  and  serves  to  cover  the  unequal  colour  of  the  under 
mass.  (4)  Lustres  are  mostly  earth  and  alkali  glazes.  This  class  includes  the 
ordinary  salt-glazed  ware,  as  well  as  glazes  containing  metallic  oxides  used  to  imitate 
gold  and  silver  surfaces  for  ornament  merely. 

Porcelain  Glaze. — We  will  here,  however,  concern  ourselves  only  with  porcelain 
glaze.  It  is  necessary  that  this  glaze  should  melt  readily  at  the  temperature  at  which 
the  article  is  fired  ;  that  it  should  be  colourless  and  opaque ;  that  it  should  fire 
sufficiently  hard  to  withstand  pressure,  grinding,  and  ordinary  cutting.  The  glaze  is 
added  to  the  porcelain  mass  with  a  flux,  so  that  the  melting  may  be  readily  effected. 
At  Meissen  the  glaze  used  contains  — 

Quartz        .        . 37-0 

Kaolin  from  Seilitz            37-0 

Lime  from  Pirna 17-5 

Broken  porcelain 8 -5 


In  the  Berlin  porcelain  manufacture  the  following  glaze  is  employed : — 

Kaolin,  from  Morle,  near  Halle 31 

Quartz-sand 43 

Gypsum ...  14 

Broken  porcelain      . .  12 

100 


SECT,    v.]         EARTHENWARE   OR  CERAMIC   MANUFACTURE.  641 

Applying  the  Glaze. — The  glaze  can  be  put  on  in  four  ways: — (i)  By  immersion. 
(2)  By  dusting.  (3)  By  watering.  (4)  By  volatilisation.  The  glaze  is  either  mixed 
with  the  ingredients,  or  applied  superficially  by  one  of  the  preceding  methods. 

Immersion. — Glazing  by  immersion  is  employed  in  the  case  of  porcelain,  the  finer 
fayence  ware,  and  sometimes  for  stoneware.  It  requires  some  degree  of  porosity  in 
order  that  the  glazing  paste  may  be  absorbed.  The  glazing  materials  are  mixed  with 
water  to  form  a  thin  pulp.  The  articles  previous  to  their  immersion  are  slightly  baked 
to  prevent  the  clay  being  softened  and  running  fluid  in  contact  with  the  water  of  the 
glaze.  The  articles  are  dipped  into  the  glaze,  which  they  readily  absorb,  a  coating  or 
thin  layer  of  glaze  remaining  on  their  surface  when  they  are  removed  from  the  bath. 
The  glaze  is  removed  from  the  bottom  of  the  article  immediately  in  contact  with  the 
substance  on  which  it  stands  to  prevent  its  sticking. 

Dusting. — Glazing  by  dusting  is  a  surface  method,  and  only  used  for  costly  ware. 
The  freshly  formed  and  still  damp  ware  is  dusted  with  lead  glaze  or  minium,  a  layer 
being  left  on  the  surface.  The  powders  employed  chiefly  contain  lead  oxide,  which 
combines  with  the  silica  and  alumina  of  the  clay  mass  during  the  firing  to  form  a  glaze. 
Recently  finely  pulverised  zinc  blende  and  Glauber's  salt  have  been  employed. 

Watering. — Watering  is  a  method  of  glazing  employed  for  non-porous  articles,  such 
as  English  porcelain,  ordinary  pottery  ware,  and  some  kinds  of  fayence  ware.  Glaze 
of  the  proper  consistence  is  poured  over  the  articles,  the  interior  sometimes  being  left 
covered  with  a  white  glaze,  while  the  outside  is  again  coated  with  a  coloured  glaze,  as 
is  seen  in  common  brown-ware. 

By  Volatilisation  or  Smearing. — Glazing  by  volatilisation  is  effected  by  conveying 
into  the  oven  a  salt  or  metallic  vapour  which  shall  form  with  the  silica  of  the  mass  an 
efficient  glaze.  The  most  general  method  is  applied  to  ware  not  requiring  to  be  baked 
in  fire-clay  vessels.  Common  salt  is  placed  in  the  oven  with  green  wood  for  fuel  to 
form  an  aqueous  smoke.  This,  the  salt,  heated  to  redness,  receives,  and  is  decom- 
posed into  hydrochloric  acid  and  soda,  the  vapours  of  which  fill  the  oven.  The  inside 
and  the  outside  of  the  vessel  submitted  to  this  process  are  thus  simultaneously  glazed. 
Fine  stoneware  baked  in  fire-clay  vessels  may  be  glazed  by  the  ignition  of  a  mixture 
of  potash,  plumbago,  and  common  salt.  During  the  baking  or  firing  lead  chloride  is 
formed,  which  combines  with  the  silica  of  the  clay  to  form  a  thin  glass.  This  method 
of  glazing  is  in  England  termed  salting,  boric  acid  being  employed. 

Lustres  and  Flowing  Colours. — A  method  of  glazing  by  volatilisation,  known  as 
glazing  with  flowing  colours,  is  employed  for  porcelain.  It  essentially  consists  in  the 
ignition  of  a  mixture  of  calcium  chloride,  lead  chloride,  and  clay,  placed  in  a  small 
vessel  in  the  firing  capsule  or  firing  chamber,  and  to  which  some  metallic  oxide  is 
added,  as  cobalt  oxide.  The  oxide  is  converted  into  chloride,  and  combines  with  the 
constituents  of  the  article. 

The  Capsule,  or  Sagger. — Porcelain  ware  and  superfine  earthenware  are  not  exposed, 
while  burning,  to  the  free  action  of  the  flame,  as  various  impurities,  such  as  ashes  and 
smoke,  would  deteriorate  the  beauty.  They  are  therefore  enclosed  in  fire-clay  vessels, 
termed  in  France  gazettes,  in  Germany  Jcapseln,  and  in  England  saggers.  These 
saggers  are  manufactured  of  the  best  fire-clay,  with  which  is  mixed  a  cement  made 
from  broken  saggers.  First  into  each  sagger  is  put  a  perfectly  true  disc  of  the  same 
material,  and  upon  this  the  porcelain  ware  is  placed,  three  knobs  or  small  props  pro- 
jecting from  the  disc,  and  keeping  the  article  from  contact  with  a  large  surface  to 
which  the  glaze  would  cause  it  to  adhere. 

The  Porcelain  Kiln. — Fig.  434  is  a  vertical  section  of  the  porcelain  kiln,  Fig.  435 
the  elevation.  The  kiln  is  essentially  a  reverberatory  furnace  with  three  stages  and 
five  fire-rooms  supplied  with  wood  fires.  The  kiln  may  be  considered  as  a  tall  cylinder, 
surmounted  by  a  cone,  in  the  apex  of  which  is  the  chimney  opening,  the  flat  vaults  by 

2  s 


642 


CHEMICAL  TECHNOLOGY. 


[SECT. 


v. 


which  it  is  divided  being  pierced  to  allow  of  communication.  Both  the  stages  L  and  L' 
serve  for  the  "strong  firing"  of  porcelain.  The  upper  stage,  L",  termed  variously  the 
howell,  crown,  or  cowl,  serves  for  the  "  raw  burning."  At  the  bottom  of  both  the  lower 
stages  are  built  the  fire-places,  f,  leading  by  g  into  the  kiln.  G  is  the  ash-pit,  T  the 
opening  to  the  ash-pit  closed  during  the  burning ;  o  is  an  opening  through  which  fuel 
is  introduced  ;  c  c  are  the  openings,  admitting  of  the  circulation  of  the  hot  gases.  P  is 


Fig.  434- 


Fig.  435- 


the  door  by  which  the  kiln  is  entered.  The  kilns  are  gradually  heated  first  to 
a  glowing  heat  and  then  to  a  strong  red  heat.  At  this  stage  the  openings  are  closed, 
and  the  kiln  raised  to  a  stronger  heat,  at  which  it  is  allowed  to  remain  for  a  short 
time.  This  intense  burning  lasts  about  seventeen  to  eighteen  hours ;  the  kiln  is  then 
opened,  and  allowed  to  cool  gradually  for  from  three  to  four  days. 

Emptying  the  Kiln  and  Sorting  the  Ware, — After  the  kiln  is  cooled,  the  saggers 
containing  the  ware  are  removed,  and  the  ware  taken  out.  It  is  then  separated  into 
four  kinds : — (a)  Superfine,  containing  no  blemish  ware;  (b)  Medium,  the  ware  slightly 
inferior  in  glaze,  &c. ;  (c)  The  chipped  and  imperfectly  glazed  ware  ;  (d)  Waste,  or  ware 
so  distorted  or  cracked  as  to  be  useless. 

Faulty  Ware. — The  chief  faults  are : — Cracking  from  the  porcelain  not  being 
sufficiently  plastic,  from  drying  unequally,  and  from  unequal  heating.  Partial  fusing 
from  a  too  strong  heat.  A«ir-bubbles  causing  lumps  to  appear  on  the  surface  of  the 
ware  through  the  expansion  of  the  air  by  heat.  Spotting,  from  fragments  of  the 
sagger  fusing  and  falling  in  upon  the  ware.  Yellow- colouring,  from  smoke  having 
entered  the  sagger.  The  chief  faults  in  the  glaze  are : — Blowing,  the  result  of  the 
development  of  gas  by  the  reaction  of  the  constituents  of  the  glaze  upon  each  other  ; 
also  resulting  from  too  strong  a  firing.  Shelling,  or  the  exfoliating  of  the  glaze. 


SECT,  v.]          EARTHENWARE   OR   CERAMIC   MANUFACTURE. 


643 


Porcelain  Painting. — Porcelain  painting  is  really  a  branch  of  glass  painting,  the 
colours  being  glass  colours,  which  when  burnt  in  become  durable  and  bright.  The 
colours  employed,  technically  termed  muffle  colours,  are — 

Iron  oxide,  for  red,  brown,  violet,  yellow,  and  sepia. 

Chromium  oxide,  for  green. 

Cobalt  oxide  and  potassium-cobalt-nitrite,  for  blue  and  black. 

Uranium  oxide,  for  orange  and  black. 

Manganese  oxide,  for  violet,  brown,  and  black. 

Iridium  oxide,  for  black. 

Titanium  oxide,  for  yellow. 

Antimony  oxide,  for  yellow. 

Copper  oxide  (and  cuprous  oxide),  for  green  and  red. 

Iron  chromate,  for  brown. 

Lead  ,,         for  yellow. 

Barium      ,,         for  yellow. 

Silver  chloride,  for  red. 

Platinum.   ,,       for  platinising. 

Purple  of  Cassius,  for  purple  and  rose-red. 

These  colour's  are  mixed  with  a  fluxing  material,  so  that  by  the  melting  a  silicate  or 
borate  may  be  formed,  yielding  a  good  glaze.  Therefore  the  cobalt  oxide .  and  the 
copper  oxide  must  first  be  mixed  with  silicic  acid  and  boric  acid,  oxide  of  antimony 
with  lead  oxide,  &c.,  to  form  a  blue,  green,  or  yellow  colour,  because  there  are  few 
metallic  oxides  yielding  these  colours  that  are  not  affected  injuriously  by  heat  or  are  by 
themselves  sufficiently  easily  fluid.  The  burning  in  of  the  colours  is  effected  in  a 
muffle,  Fig.  436,  the  opening  o  serving  as  a  communnication  with  the  interior,  by 
which  the  degree  of  heat  may  be 
ascertained ;  the  opening  m  serves 
for  the  escape  of  the  vapours  of  the 
essential  oils  (oil  of  turpentine,  oil 
of  lavender,  <tec.),  with  which  the 
•enamel  colours  are  sometimes  ground 
up.  Fig.  437  shows  the  method  of 
heating  the  muffle.  The  heating  is 
commenced  at  a  low  temperature 
and  is  gradually  increased  to  a  red 
heat.  From  time  to  time  the  muffle 
is  opened  till  the  colours  begin  to 
disappear ;  then  the  muffle  is  care- 
fully closed,  raised  to  a  blight  red 
heat,  and  finally  allowed  to  cool  as 
slowly  as  possible. 

Ornamenting  the  Porcelain. — The  gold  employed  for  decorating  the  porcelain  is 
dissolved  in  aqua  regia,  and  precipitated  with  either  iron  sulphate,  bismuth  nitrate, 
or  by  means  of  oxalic  acid.  In  its  application  the  gold  must  be  intimately  mixed 
with  a  flux,  generally  mercurous  nitrate.  Shell  gold  is  employed,  also  gold-beaters' 
refuse.  The  article  to  be  gilt  must  be  thoroughly  freed  from  grease,  else  the  gold 
will  not  adhere.  The  gold  powder,  finely  ground  up  with  sugar  or  honey,  or  some 
such  soluble  substance,  is  applied  with  a  pencil  brush.  The  burning  in  is  effected  in  a 
muffle.  The  gold  is  not  melted  during  the  burning,  but  becomes  firmly  set  upon 
the  article  by  means  of  the  flux.  After  burning  the  gold  does  not  at  once  appear  bright, 
but  requires  burnishing  with  an  agate  tooL 

Bright  Gilding,— Bright  gilding  differs  from  the  foregoing  in  requiring  no  after 


437- 


Fig.  436. 


644  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

polishing  or  burnishing.  It  is  effected  by  burning  in  a  mixture  of  gold  sulphide  or 
fulminating  gold  in  balsam  of  sulphur.  When  an  article  is  gilded  with  precipitated 
metallic  gold  or  a  bright  gold  preparation,  the  gilding  is  secure  from  injury  by  handling 
or  scratching  with  the  finger-nail,  &c. 

Silvering  and  Platinising. — Silvering  and  platinising  are  usually  only  in  slight 
requisition.  Metallic  silver  is  thrown  down  from  its  solution  by  means  of  copper  or 
zinc  ;  the  platinum  is  precipitated  from  its  neutral  chloride  by  means  of  boiling  with 
potash  and  sugar.  The  tarnishing  of  silver  on  porcelain  by  sulphuretted  hydrogen 
may,  according  to  Rousseau,  be  prevented  by  placing,  before  burning,  a  thin  layer  of 
gold  upon  the  part  silvered ;  the  result  then  is  a  white  layer  of  gold-silver.  The 
silver  and  platinum  are  mixed  with  basic  bismuth  nitrate,  painted  on  and  burnt  in,  and 
afterwards  burnished. 

Lithophanie. — Transparent  porcelain  is  used  in  the  art  of  lithophanie,  or  making 
transparencies.  A  thin  and  unglazed  porcelain  plate  is  pressed  into  a  flat  gypsum 
mould  bearing  the  pattern  in  high  relief.  The  figures  by  transmitted  light  appear  in 
delicately  rounded  tones  of  light  and  shade.  The  applications  of  this  art  to  the 
manufacture  of  lamp  shades,  window  ornaments,  &c.,  are  too  well  known  to  need  remark 
here. 

Very  similar  to  lithophanies  are  the  articles  of  porcelain  and  fayence  now  pro- 
duced under  the  names  Email  ombrant,  or  Email  de  Rubelles,  or  lithoponies.  They  are, 
however,  as  regards  the  pressing,  the  very  opposite  to  lithophanies,  since  in  Email 
ombrant  the  darkest  parts  must  be  most  depressed  and  therefore  the  thinnest,  and  the 
picture  is  seen  not  by  transmitted  but  by  reflected  light.  In  these  objects  depressions 
are  produced  by  means  of  moulds,  and  are  then  filled  up  with  a  semi-transparent  and 
coloured  mass  of  glaze,  when  the  deepest  parts  take  up  thicker  strata  of  glazing,  and 
appear  darker  than  the  more  elevated  parts. 

II.  Tender  Porcelain. — French  Fritte  Porcelain. — Tender  or  fritte  porcelain  is  dis- 
tinguished in  commerce  as  of  two  manufactures,  French  and  English.  The  French 
manufacture,  in  1695,  was  first  carried  on  at  St.  Cloud,  near  Paris,  by  Morin,  who 
employed  a  glassy  mass,  without  the  addition  of  kaolin,  but  containing  lead,  somewhat 
similar  to  crystal  glass.  It  can,  therefore,  hardly  be  considered  a  porcelain,  strictly 
so  called,  until  melted  with  lime  and  alumina.  Thus  fritte  porcelain  is  composed  of — 
(i)  A  glass  mass  or  fritte,  obtained  from  silica  and  alkalies.  (2)  Marl,  as  a  clay  con- 
stituent ;  chalk,  as  a  lime  constituent.  The  proportions  of  these  constituents  are — 

Fritte 75-75 

Marl 17        ...          8 

Chalk 8         ...         17 

The  fritte  is  mixed  with  the  chalk  and  marl  to  form  a  thin  pulp,  which  is  allowed 
to  remain  for  a  month  to  dry,  and  then  again  pulverised.  When  required  quickly, 
plasticity  is  obtained  by  adding  soap-  or  lime-water.  Fritte  porcelain  is  burnt  in  saggers, 
generally  before  glazing.  During  the  burning  this  kind  of  porcelain  softens  more  than 
the  hard,  and  requires  supporting  on  every  side.  It  is  for  this  reason  generally  baked 
in  fire-clay  moulds.  The  ordinary  oven  is  employed.  The  glaze  for  tender  porcelain 
is  a  kind  of  crystal  glass  containing  lead.  This  glaze  is  poured  over  the  articles,  as 
they  are  non-absorbent  on  immersion.  French  porcelain  is  similar  to  cryolite  glass  or 
hot-cast  porcelain.  ^ 

English  Fritte  Porcelain. — English  tender  porcelain  consists  of  a  plastic  clay,  so- 
called  china  clay  or  Cornish  stone,  a  weathered  pegmatite,  with  fire-clay  and  bone-ash. 
The  addition  of  the  latter  is  due  to  Mr.  Spade,  in  1802  ;  recently  calcium  phosphate, 
as  apatite,  phosphorite,  staffelite,  or  sombrerite,  has  been  substituted.  The  glaze 
is  composed  of  Cornish  stone,  chalk,  fire-brick,  borax,  and  lead  oxide.  The  article 
must  be  baked  before  glazing,  as  the  glaze  is  so  much  more  easily  fusible  than 


SECT,  v.]         EARTHENWARE   OR  CERAMIC   MANUFACTURE.  645 

the  body  of  the  article ;  and  in  this  second  firing  lies  the  difference  between  the 
manufacture  of  tender  and  of  hard  porcelain.  In  hard  porcelain  the  melting-point  of 
the  glaze  and  the  body  are  the  same.  English  porcelain  is  far  less  solid  and  more 
liable  to  crack  than  the  hard  ;  upon  the  other  hand,  English  porcelain  is  the  more 
plastic,  and  can  be  produced  at  a  lower  temperature  in  saggers  of  inferior  fire- 
resisting  qualities,  consequently  at  a  less  expense.  The  burning  takes  place  in  a  stage 
oven  with  anthracite  coals,  the  articles  being  placed  in  saggers.  The  glaze  is  applied 
by  immersion.  Recently  boric  acid  has  been  largely  employed  in  glazing  English 
porcelain. 

Parian  and  Carrara. — Parian  is  an  unglazed  statue-porcelain,  similar  to  English 
porcelain,  but  more  difficultly  fusible,  containing  less  flux  and  more  silica.  The  colour 
is  a  very  slight  yellow ;  the  surface  is  wax-like.  Parian  was  first  prepared  by  Cope- 
land,  in  1848,  although  the  idea  was  not  new,  as  before  this  time  Kiihn,  of  Meissen, 
had  prepared  statues  and  medallions  of  porcelain  in  imitation  of  marble.  The  compo- 
sition of  Parian  is  very  variable;  some  on  being  tested  yield  calcium  phosphate, 
others  barium  silicate,  and  again  some  contain  only  kaolin  and  felspar. 

Carrara,  so  named  in  imitation  of  the  marble  produced  from  Carrara  in  Tuscany, 
is  intermediate  to  Parian  and  stoneware,  is  less  transparent  than  Parian,  and  sometimes 
whiter  in  colour. 

III.  Stoneware. — Stoneware  differs  entirely  from  porcelain.  It  is  dense,  sonorous, 
fine-grained ;  does  not  cling  to  the  tongue ;  it  is  semi-fused  and  opaque.  Even  fine 
white  stoneware  is  different  from  porcelain  in  transparency,  being  entirely  opaque, 
although  in  some  other  respects  similar.  Stoneware  is  distinguished — 

1.  As  porcelain  glazed. 

2.  As  Avhite  or  coloured  unglazed. 

3.  As  common  stoneware,  salt-glazed. 

The  fine  white  stoneware  is  made  from  a  plastic  clay,  burning  white,  and  not  very 
refractory.  To  the  clay  is  added  kaolin  and  fire-clay  with  a  felspar  mineral,  generally 
Cornish  stone,  as  a  flux.  The  glaze  contains  lead  oxide  and  borax,  and  is  transparent. 
The  flux  is  used,  in  the  making  of  stoneware,  much  more  freely  than  in  porcelain,  in 
the  proportion  of  more  than  half  the  weight  of  the  mass.  It  follows  that  stoneware  can 
be  burnt  at  a  lower  temperature  than  porcelain.  The  articles  are  fashioned  out  of  the 
plastic  clay  in  the  same  manner  as  porcelain.  Fine  stoneware  is  used  as  a  cheap  sub- 
stitute for  porcelain,  it  being  much  more  easily  burnt. 

White  or  coloured  unglazed  stoneware,  or  Wedgwood  ware,  is  made  from  a  plastic 
slightly  refractory  clay,  kaolin,  fire-clay,  and  Cornish  stone,  the  latter  in  the  proportion 
•of  half  the  weight  of  the  whole.  It  is  more  easily  fusible  than  porcelain,  requiring  a 
lower  temperature  in  burning.  The  coloured  stoneware  is  of  the  same  composition  as 
the  white,  the  colouring  being  only  superficial.  Frequently  other  coloured  clays  are 
used  for  ornaments  in  relief.  Coloured  Wedgwood  ware  is  known  as  Egyptian, 
bamboo,  fine  salt  ware,  fine  biscuit,  &c. 

Common  stoneware  differs  from  the  preceding  in  containing  no  flux,  the  clay  being 
semi-fused  by  the  continued  action  of  the  fire.  To  the  clay  is  added  fine  sand,  or 
pulverised  fragments  of  stoneware.  Chemical  and  pharmaceutical  utensils,  acid 
tanks,  &c.,  are  made  of  this  ware,  it  being  strong  and  durable.  The  colour  is 
generally  grey. 

Stoneware  Ovens. — The  ovens  for  burning  stoneware  are  so  constructed  that  the 
articles  can  either  lie  down  or  be  placed  vertically.  Fig.  438  is  the  vertical  section  of 
such  an  oven  through  the  line  AB  in  Fig.  439.  Fig.  440  is  a  section  through  the 
line  CD  seen  from  B.  Fig.  441  is  a  section  through  CD  seen  from  A.  Fig.  439  is 
the  plan  on  the  line  EF,  Fig.  438.  a  a  is  the  arch  or  vault  of  the  oven,  built  of 
clay  ;  J,  the  vessel-chamber  ;  c,  the  fire-room  ;  d,  the  fire-bars ;  e,  the  stoke-hole  ;  ft 


646 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


the  ash-pit ;  y,  an  air-draught ;  i  i,  a  pierced  wall ;  k,  a  pierced  back- wall,  through 
which  the  flame  and  hot  gases  escape  into  o,  serving  as  a  flue.     Anthracite  is  used  as 

Fig.  438 


Fig.  439- 


Fig.  440. 


Fig.  441. 


fuel.  Another  form  of  oven  in  which  mineral-water  bottles  are  burnt  is  shown  in 
Fig.  442.  It  is  constructed  on  an  easy  slope  ;  at  the  lowest  part  is  the  fire-room,  A. 
In  the  middle  of  the  burning-room  is  the  pierced  wall,  C,  technically  termed  the 


SECT,  v.]          EARTHENWARE   OR   CERAMIC   MANUFACTURE.  647 

window,  through  which  the  hot  gases  and  flame  escape  into  D.  The  vault  and  walls, 
B  and  E,  are  of  broken  earthenware,  bound  with  mortar.  A  chimney  is  unnecessary, 
the  gases  escaping  through  the  pierced  wall,  E,  into  the  air.  The  burning  usually  takes 
about  eight  days.  The  high  temperature  at  which  common  stoneware  is  burnt,  and 
the  nature  of  its  components,  render  glazing  unnecessary ;  but  generally  a  gkze  is 
obtained  with  the  help  of  common  salt 

placed  in  the  oven  during  burning.    After        *S-  442- 

the  placing  of  the  salt  the  openings  of  the 
oven  are  closed  for  some  time,  and  then 
a  second  quantity  of  salt  is  introduced. 
The  silica,  with  the  assistance  of  the 
steam,  decomposes  the  salt  into  hydro- 
chloric acid  and  soda,  with  which  it  com- 
bines. Thus  there  is  formed  on  the  surface 
of  the  ware  a  glaze  of  sodium  and  alu- 
minium silicate.  The  salt  will  take  up  more  than  50  per  cent,  silica,  according  to 
Leykauf's  experiments;  therefore,  the  more  silica  the  better  glaze.  An  oven  of 
moderate  size  will  require  80  to  100  Ibs.  of  salt ;  the  purity  of  the  salt  is  not  a 
subject  of  much  consideration.  The  glaze  is  colourless,  and  the  vessel  appears  the 
colour  of  the  clay.  Stoneware  that  is  unequally  coloured,  one  part  brown,  the  other 
grey,  has  been  brought  to  that  state  by  escape  of  hydrocarbons  into  the  burning-room. 

Lacquered  Ware. —  Lacquered  ware,  known  as  Terralite  and  Siderolite  ware,  is 
manufactured  in  Northern  Bohemia  by  the  firm  of  Villeroy  &  Boch,  of  Mettlach,  and  is 
an  intermediate  ware  to  fine  and  common  stoneware.  It  has  no  glaze,  but  a  strong 
surface  colour  of  varnish  or  lacquer.  Candlesticks,  bowls,  flower-vases,  jugs,  flower- 
pots, baskets,  butter-dishes,  fruit-dishes,  &c.,  are  formed  from  this  ware,  and  baked  in 
saggers  in  the  usual  manner.  Great  care  and  attention  are  required  in  burning 
the  ware.  The  colour  or  bronze  is  mixed  with  varnish,  thinned  with  turpentine  or 
linseed-oil,  and  applied  with  a  pencil.  The  ware  is  then  placed  in  a  slow  oven ;  the 
ethereal  oils  volatilise,  and  the  bronze  colour  becomes  fixed  to  the  surface  of  the  ware. 

IV.  Fayence. — Fayence  ware  (English  fine  stoneware)  derives  its  name  from 
the  town  of  Faenza,  in  Central  Italy,  where  the  ware  was  skilfully  made.  In 
the  ninth  century  the  Spanish  Moors  manufactured  fayence  in  the  Island  of  Majorca, 
whence  the  present  majolica,  the  slight  alteration  in  the  manner  of  spelling  being 
accounted  for  by  Dante,  in  his  "  Tra  isola  di  Capri  e  Majolica"  on  the  ground  that 
the  older  Tuscan  writers  spell  the  name  of  the  island  "  Majolica."  The  industry 
developed  from  the  thirteenth  to  the  fifteenth  century  ;  from  that  to  the  seventeenth 
it  culminated,  and  then  commenced  to  decline.  In  the  middle  of  the  sixteenth  century 
Bernard  Palissy  introduced  the  ware  known  as  Palissy-fayence  into  France.  Palissy's 
celebrated  pieces  rustiques  consist  of  ware  ornamented  with  fish,  fruit,  vegetables,  &c., 
naturally  coloured  in  enamel.  The  body  of  porous  fayence  ware  is  earthy,  and 
clings  to  the  tongue.  It  is  opaque,  with  more  or  less  plasticity,  and  little  or  no 
sonorosity.  It  consists  generally  of  plastic  clay,  or  a  mixture  of  this  with  common 
potter's  clay.  It  differs  from  clay  ware  in  the  employment  of  finer  material,  mani- 
pulated with  greater  care.  Fine  white  fayence  is  distinct  from  common  enamelled 
fayence.  Fine  fayence  (semi-porcelain)  consists  of  a  plastic  clay  with  pulverised 
quartz  or  fire-bricks,  with  kaolin  or  pegmatite  and  felspar  minerals.  It  remains 
white  after  burning,  and  is  coated  with  a  transparent  glaze.  The  fayence  wares  of 
different  countries  differ  greatly  ;  some  are  easily  fusible,  others  again  are  burnt  at  a 
high  temperature.  The  composition  of  the  glaze  is  therefore  very  varied.  Common 
lime  fayence  is  a  mixure  of  potter's  or  plastic  clay,  marl  (clay  with  calcium  carbonate), 
or  quartz  and  quartz-sand.  It  is  characterised  by  containing  15  to  25  per  cent,  of 


648  CHEMICAL   TECHNOLOGY.  [SECT.  v. 

lime,  which,  at  the  low  temperature  at  which  common  fayence  is  burnt,  only  loses  a 
portion  of  its  carbonic  acid.  The  common  fayence  ware  is  thus  easily  distinguished 
from  other  wares  by  its  property  of  effervescing  when  an  acid  is  poured  into  a  vessel 
made  of  this  ware.  Its  fracture  is  earthy  ;  the  colour,  consequent  upon  its  containing 
2  to  4  per  cent,  of  iron  oxide,  is  a  decided  yellow,  so  that  an  opaque  glaze  is  employed. 
The  glaze  or  enamel  contains  usually  tin  and  lead  oxides,  alkalies,  and  quartz. 
The  more  iron  oxide  and  lime  contained  in  the  mass,  the  lower  the  temperature 
required  for  burning.  Fayence,  like  porcelain,  is  twice  burnt,  first  without,  and  secondly 
with,  the  glaze.  It  is  burnt  in  saggers ;  the  ware  is  placed  in  the  saggers,  and  these 
are  piled  one  upon  the  other  in  the  furnace,  with  a  layer  of  fat  clay  between  each  pair 
The  articles  stand  in  the  saggers  upon  small  tripods,  in  order  to  expose  as  small  a  con- 
tact surface  as  possible.  The  hard -burnt  ware  has  next  to  be  glazed.  A  thin  pulp 
with  water  is  made  of  the  materials  of  the  glaze  placed  in  a  cistern  into  which  the 
articles  are  dipped.  The  glaze  usually  consists  of  felspar  (Cornish  stone),  fire-clay, 
heavy  spar,  sand,  borax  and  boric  acid,  crystal  glass,  soda  and  sodium  nitrate,  white- 
lead,  minium,  and  smalt.  The  composition  of  this  glaze  is  ordinarily  very  complicated, 
but  the  essential  constituents  are  silica,  boric  acid,  alumina,  lead  oxide,  and  alkali. 
Recently  the  Peruvian  mineral,  so-called  tiza  (sodium  and  calcium  borate),  has  been  em- 
ployed. The  addition  of  lead  serves  to  render  the  glaze  easily  fusible,  while  the  felspar 
imparts  the  softness  characteristic  of  a  lead-alkali  glaze. 

Ornamenting  Fayence. — Fayence  is  ornamented  by — i.  Painting;  2.  Casting; 
3.  Printing ;  4.  Lustring.  Painting  is  usually  done  with  the  brush,  partly  under,  and 
partly  upon,  the  glaze.  The  glazing  oven  not  attaining  so  high  a  temperature  as  the 
porcelain  oven,  the  colours  are  not  affected  by  the  heat.  The  colours  used  are 
chromium,  cobalt,  iron,  antimony  oxides,  &c.  The  rose-  and  purple-red  colours  are 
obtained  from  gold  preparations.  The  pink  colour,  carnation  pink,  was  discovered 
in  this  country,  and  is  a  stannic  chromate.  To  make  this  colour — 

Stannic  acid 100 

Chalk 34 

Potassium  chromate  ..........  3-4 

Silica 5 

Alumina i 

are  well  mixed  and  allowed  to  stand  for  some  hours  in  a  strong  heat.  The  mass 
appears  as  a  dirty  rose- red  colour,  attaining  its  full  brilliancy  when  washed  with 
water  acidulated  with  hydrochloric  acid.  The  casting  consists  in  the  fayence  vessel 
receiving  a  surface  layer  of  coloured  clay  in  any  required  part,  independently  of  the 
colours  of  the  mass.  These  coloured  clays  or  clay-washes  are  made  of  the  ordinary 
fat  clays  d  metallic  oxides.  The  printing  is  accomplished  with  the  aid  of  thin 
tissue-paper,  upon  which  the  pattern  is  first  printed  from  a  copper  plate,  and  after- 
wards transferred  to  the  ware.  For  black,  a  mixture  of  forge-scale,  manganese, 
and  cobalt  oxide  or  chrome-black  is  employed ;  for  blue,  cobalt  oxide  mixed  with, 
for  bright  blue,  fire-brick,  and  for  less  intense  colours,  heavy-spar,  both  of  course 
being  pulverised.  This  mixture  is  burnt,  the  frit  ground,  and  mixed  with  a  flux 
of  equal  parts  of  flint-glass  and  fire-clay.  Copper  plates,  in  which  the  pattern  is 
deeply  cut,  are  charged  with  colour  mixed  with  linseed-oil ;  a  transfer  is  then  taken 
on  the  fine  "  pottery  tissue"  paper,  and  laid  on  the  ware.  By  means  of  a  rubber 
the  colour  is  caused  to  leave  the  paper,  which  has  been  previously  moistened  with 
water,  and  adhere  to  the  ware.  The  paper  is  then  washed  off,  and  the  article  taken 
to  the  kiln. 

Flowing  Colours,—  Flowing  colours  are  nmch  employed  in  ornamenting  fayence. 
The  common  fayence  or  delft  ware  is  coloured  blue  in  this  manner  by  means  of  cobalt 
oxide  mixed  with  the  glaze.  When  the  vessels  are  taken  to  the  burning-kiln,  a 


SECT,  v.]          EARTHENWARE   OR   CERAMIC   MANUFACTURE.  649 

mixture  of  calcium  chloride,  lead  chloride,  and  clay  is  also  introduced  on  a  small 
plate.  The  cobalt  oxide  is  converted  into  a  chloride  by  combining  with  the 
volatilised  materials,  and  in  turn  combines  with  components  of  the  material  of  the 
vessel.  By  this  means  the  articles  obtain  an  apparent  transparency  somewhat  similar 
to  that  characteristic  of  porcelain. 

Lustres. — Some  kinds  of  ware  have  a  second  coating — a  metallic  lustre  or  glaze — 
given  to  them  after  burning.  Gold  Lustre  :  The  different  kinds  of  gold  lustre  are 
very  similar  and  need  not  be  detailed.  They  are  essentially  composed  of  fulminating 
gold  and  balsam  of  sulphur,  the  latter  prepared  by  heating  linseed-oil  and  sulphur 
together.  Platinum  Lustre :  This  is  obtained  by  mixing  anhydrous  platinum  chloride 
with  lavender-oil  or  balsam  of  sulphur;  also  by  the  well-known  precipitation  of 
platinum  with  sal-ammoniac.  Silver  Lustre  is  either  a  yellow  lustre  or  a  cantharidine 
lustre,  so  called  from  its  similarity  in  appearance  to  the  wing-cases  of  the  Spanish  fly 
(Cantharis  vesicatoria).  Salvetat  believes  that  silver  chloride  may  be  employed  as  a 
yellow  lustre,  similarly  to  gold  preparations.  The  cantharidine  lustre  is  generally  a 
yellow  lustre,  the  difference  being  that  it  is  only  used  for  white  grounds,  while  the 
former  is  employed  for  blue  grounds,  on  which  it  appears  slightly  tinged  with  green. 
Copper  lustre  is  both  red  and  yellow ;  it  is  used  for  Spanish  fayence  and  majolica 
wares.  It  is  chiefly  formed  by  a  copper  silicate.  Lead  oxide,  or  lead  lustre,  is  merely 
a  lead  glaze.  Silver  chloride,  mixed  with  lead  lustre,  is  reduced,  the  result  being  a 
deposit  of  a  gold-yellow  or  a  silver-white  colour,  according  to  the  proportion  of  silver. 

Etruscan  Vases. — The  vases  of  the  old  Romans  were  a  kind  of  fayence  ware,  con- 
taining iron,  and  formed  of  a  clay  decomposed  by  quartz,  only  slightly  burnt,  some- 
times unglazed,  sometimes  coated  with  an  easily  fusible  glaze.  These  vases  and 
articles  are  celebrated  more  for  their  beauty  of  form  than  for  any  peculiarity  in  com- 
position, which  is  very  analogous  to  the  well-known  delf  ware  of  which  our  table- 
services  are  made. 

Clay  Pipes. — In  the  manufacture  of  clay  pipes  there  is  employed  the  beautifully 
white  pipe-clay,  containing  neither  iron,  nor  sand,  nor  carbonate  of  lime.  The  clay,  if 
pure,  always  burns  white  :  but  occasionally,  when  a  yellow  colour  appears,  the  clay  is 
burned  for  a  longer  time,  whereby  the  iron  oxide  colouring  the  clay  is  removed. 
The  pipes  are  formed  in  a  mould  similar  in  shape  to  the  pipe.  A  roll  of  clay  is  taken, 
and  carefully  spread  out  to  the  length  of  the  pipe.  The  mould  is  constructed  in  two 
parts,  hinged  together  like  a  meerschaum  pipe-case,  and  is  generally  of  iron.  The 
roll  of  clay  is  placed  on  the  lower  half  of  the  mould,  and  the  upper  half  is  then  pressed 
or  screwed  down.  A  wire  is  then  pushed  up  the  entire  length  of  the  stem.  The  pipe 
is  then  taken  out  of  the  mould,  and  set  aside  to  dry.  It  is  afterwards  taken  to  the 
oven,  where  about  a  gross  of  pipes  are  introduced  into  each  sagger.  The  saggers  are 
long  clay  tubes.  Sometimes  the  pipes  are  burnt  without  saggers.  To  prevent  the 
pipe  adhering  to  the  lips  on  account  of  the  porosity  of  the  clay,  the  end  put  to  the 
mouth  is  rubbed  with  a  mixture  of  soap,  wax,  and  lime-water. 

Water  Coolers. — The  Spanish  water-cooling  vessels,  or  alcarrazas,  are  made  of  a 
porous,  unglazed  earthenware.  The  constant  evaporation  of  the  water  exuding  to  the 
outer  surface  of  the  vessel  causes  the  water  to  be  kept  cool  in  the  hottest  climates. 
The  vessels  are  only  slightly  burnt.  According  to  Sallior,  water  can  be  cooled  15°  in 
an  alcarraza,  while  Sevres  ware  only  permits  of  the  cooling  of  its  contents  in  a 
similar  manner  some  2°  or  3°.  These  vessels  are  known  in  France  as  hydrocera/mes. 
In  this  country  Egyptian  wine  and  butter  coolers  are  very  common,  while  in  Egypt, 
Spain,  Turkey,  the  Indies,  and  Americas  they  are  really  necessaries.  In  Bengal  these 
coolers  are  made  from  the  mud  of  the  Ganges.  In  the  Levant  they  are  termed  baldaques  ; 
in  Syria  and  Egypt  collies  or  giillies,  while  in  many  places  they  are  also  known  as 
gargoulettes. 


650  CHEMICAL   TECHNOLOGY.  [SECT.  v. 

V.  Common  Pottery. — To  distinguish  between  the  different  kinds  of  this  ware 
is  extremely  difficult.  The  manufacture  is  entirely  distinct  from  the  preceding. 
For  the  so-called  white  pottery,  used  for  culinary  purposes,  ordinary  potter's  clay  is 
employed,  and  for  brown  ware  a  moderately  refractory  clay.  The  natural  clays  are,  as 
a  rule,  too  fat  to  be  used  without  the  addition  of  some  other  material,  generally  sand ; 
besides  sand,  fire-brick,  chalk,  charmotte,  and  anthracite  coal-ash  are  employed.  The 
vessels  are  formed  upon  a  potter's  wheel,  air-dried,  and  then  glazed.  The  employment 
of  a  lead  glaze  was  but  a  short  time  ago  unknown  in  the  glazing  of  this  kind  of  ware. 
Ordinarily  the  mass  is  white  or  yellow,  sometimes  brown-red ;  the  glaze  being 
transparent,  the  colour  of  the  body  or  mass  is  always  visible.  Partly  because  the 
ware  is  very  easily  fusible,  and  partly  because  a  low  heat  is  used  in  the  burning,  the 
glaze  must  also  be  very  easily  fusible.  For  this  reason  a  lead  glaze,  forming  an 
aluminium  and  lead  glass  is  very  applicable,  and  is  employed  mixed  with  loam  (clay 
and  sand).  The  materials  are  ground  and  very  intimately  mixed  in  a  hand-mill.  The 
lead  used  is  generally  a  lead-glance.  During  the  burning  the  lead-glance  is  roasted, 
and  the  sulphur  is  driven  off  as  sulphurous  acid.  The  lead  oxide  combines  with 
the  silica  and  alumina  of  the  loam,  or  mixture  of  sand  and  clay,  to  form  aluminium 
and  lead  silicate. 

The  glazing  of  the  air-dried  ware  can  be  performed  in  three  ways :  either  by 
immersion,  by  sprinkling,  or  by  dusting.  By  immersion  the  workman's  hands  come 
into  contact  with  the  lead-containing  glaze,  with  detriment  both  to  his  health  and  the 
adhering  of  the  glaze  if  his  hands  should  be  greasy.  This  method  is  not  therefore 
often  employed.  Sprinkling  is  generally  adopted.  In  dusting,  the  ware  is  first  im- 
mersed in  a  pulp  of  fat  clay,  and  then,  while  still  damp,  dusted  with  the  finely 
pulverised  glaze.  The  danger  of  this  process  is  the  inhaling  of  the  fine  particles  of 
glaze  floating  in  the  air  of  the  work-room.  When  the  lead  oxide  is  properly  pro- 
portioned to  the  silica  of  the  clay  or  loam,  the  resulting  lead-glass  is  not  affected  by 
ordinary  organic  acids.  But  if  the  lead  oxide  is  not  well  combined  with  the  silica, 
it  will  be  dissolved  by  boiling  vinegar.  The  experiments  of  Buchner,  A.  Vogel, 
Erlenmeyer,  and  others  have  shown  that  the  insolubility  of  lead-glaze  is  not  so  great 
as  has  been  supposed,  very  dilute  vinegar  in  some  cases  being  sufficient  to  effect  a 
solution.  The  use  of  vessels  thus  glazed  may  therefore  have  no  little  influence  upon 
the  health  of  a  family,  and  it  becomes  necessary  to  consider  if  there  is  not  some  sub- 
stitute. All  injury  likely  to  accrue  from  the  use  of  this  glaze  would  be  removed  if 
the  potter  would  but  reburn  imperfect  ware,  or  employ  ovens  of  the  best  construc- 
tion ;  but  this  is  not  always  the  case.  Recently  the  preparation  of  a  glaze  free  from 
lead  has  been  attempted,  by  employing  water-glass,  or  a  mixture  therewith  of  calcium 
borate. 

Burning. — The  glazed  vessels  are  next  taken  to  the  oven.  This  is  generally  a 
reverberatory  furnace,  2%  to  2f  metres  in  height,  and  7  to  10  metres  in  length.  At 
one  end  is  the  fire-grate,  and  at  the  other  the  chimney.  The  vessels  are  burnt  with- 
out saggers,  and  are  exposed  to  the  full  influence  of  the  flame.  The  fire  is  at  first 
kept  low  for  eleven  to  twelve  hours,  and  then  maintained  strongly  for  four  to  five 
hours.  The  vessels  can  be  removed  from  the  oven  about  eighteen  to  twenty-four 
hours  after  being  burnt. 

VI.  Brick  and  Tile  Making. — The  bricks  of  modern  times  are  very  distinct  from 
the  unburnt,  air-dried  clay  lumps ;  although  these  are  still  in  use  in  some  districts. 

Terra-cotta. — The  term  terra-cotta  ware  generally  includes  the  burnt,  unglazed 
yellow  or  red  clay  ware,  and  also  tiles,  employed  in  building  and  architectural  orna- 
mentation. The  preparation  of  this  ware  is  almost  entirely  mechanical,  and  does  not 
call  for  any  further  elucidation  in  this  work  than  will  be  found  in  the  following  pages 
descriptive  of  the  class  of  manufacture  to  which  it  belongs. 


SECT,  v.]         EARTHENWARE   OR   CERAMIC   MANUFACTURE.  651 

Brick  Material. — Various  clays  are  used  in  brick-making.  Usually  those  only  are 
selected  that  will  form  a  brick  capable  of  bearing  a  considerable  strain.  In  the  burning 
a  test-brick  is  employed,  which  is  removed  from  time  to  time  to  see  the  progress  of  the 
fire,  to  prevent  the  over-burning  of  the  bricks,  or  the  lowering  of  the  fire  till  the 
bricks  are  sufficiently  burnt ;  but  this  brick  must  not  be  confounded  with  another 
test-brick  for  the  following  purpose.  A  brick  is  made  of  any  new  clay  to  be  tested. 
and  is  set  apart  in  an  active  kiln,  being  burnt  at  the  same  temperature  as  the  bricks  of 
this  kiln  afterwards  sent  into  the  trade.  By  the  qualities  of  this  test-brick  the  nature 
and  worth  of  the  new  clay  is  judged.  A  batch  of  bricks  should  be  composed  of  clays 
that  may  all  be  burnt  at  the  same  temperature,  else  very  unequal  results  will  follow ; 
some  bricks  will  be  under-burnt  and  some  over-burnt,  while  only  those  bricks  to  the 
clay  of  which  the  temperature  is  adapted  will  be  of  use  commercially.  A  brick-clay 
containing  much  calcium  carbonate  can  be  burnt  at  a  very  low  temperature,  and  in- 
deed bricks  so  composed  are  very  solid,  and  have  great  durability.  Brick-clays  often 
contain  felspar,  mica,  ferric  hydrate,  and  phosphate,  besides  organic  matter.  When 
these  are  not  in  large  quantities  their  presence  is  not  detrimental.  Mica  and  felspar 
with  iron  oxide  act  as  fluxes,  and  in  moderate  quantities  are  useful  rather  than  per- 
nicious. Flint  stones,  large  pieces  of  calcium  carbonate  and  gypsum,  interfere  with 
the  easy  utilisation  of  brick-clays.  Sulphur  pyrites  render  clays  unsuited  to  the 
manufacture  of  bricks,  as  the  iron  sulphide  remaining  in  the  brick  after  burning 
oxidises  in  the  air  to  sulphate,  which  in  a  short  time  weathers  out  and  renders 
the  brick  brittle.  In  the  Netherlands,  in  the  Thames  near  London,  on  the  banks 
of  the  Ganges  and  Nile,  in  the  muds  of  rivers,  and  in  nearly  all  clays  exposed 
to  the  ebb  and  flow  of  water,  is  found  an  admirable  material  for  brick-making.  Since 
1852  a  mixture  of  lime,  river-sand,  and  water  has  been  extensively  used  as  a  brick 
material,  and  for  other  building  purposes. 

Preparation  of  the  Clays. — The  excavating  of  the  clay  for  making  bricks  is  carried 
on  in  the  summer  or  spring.  The  clay  is  placed  in  not  too  high  a  layer,  and  allowed  to 
weather.  It  is  very  advantageous  if,  during  the  weathering,  a  frost  sets  in.  The 
clay  is  allowed  to  remain  thus  exposed  to  atmospheric  influence  until  it  becomes  boggy 
or  marshy.  In  this  condition  it  is  brought  to  a  tank  dug  in  the  ground,  4  metres  long, 
2  metres  broad,  and  1*3  metre  in  depth,  where  it  is  mixed  with  about  as  much  water 
as  will  stand  to  a  height  of  6  centimetres  in  the  tank.  So  soon  as  the  clay  is  thoroughly 
saturated  it  is  treadled — that  is,  the  brick-maker  fastens  boards  or  wooden  shoes  to 
his  feet,  and  carefully  treads  over  the  clay,  picking  out  all  the  flints,  &c.,  which  resist 
the  passage  of  his  foot  to  the  bottom  of  the  layer.  This  process  is  repeated  two  or  three 
times.  Sand  is  then  added  to  the  clay.  If  the  clay  is  fat  the  mixture  is  proceeded 
with  ;  but  if  it  is  a  poor  clay  it  is  advantageous  to  wash  out  a  portion  of  the  sand. 
This  may  be  effected  in  two  ways.  The  ground-tank  just  described  may  be  flooded 
with  water,  and  the  sand  allowed  to  settle  to  the  bottom  ;  or  the  mixed  sand  and  clay 
is  placed  in  a  large  wooden  tub,  with  a  hole  in  the  side  near  the  bottom  stopped  with 
a  plug.  When  the  water  has  thoroughly  impregnated  the  clay  it  is  let  off,  carrying 
part  of  the  sand  with  it.  Or  the  clay  is  stirred  with  the  water  to  a  thin  pulp,  and 
allowed  to  run  out  of  the  wooden  cistern  into  a  ground-tank,  where,  with  the  water, 
the  sand  settles  to  the  bottom.  London  clay,  being  mostly  alluvial,  has  to  be  very 
carefully  treated  to  free  it  from  flint  stones,  &c. ;  it  is  afterwards  mixed  with  ash  or 
sand. 

The  "  treading "  of  the  clay  is  at  the  present  time  performed  in  mills,  termed 
"  pug"  mills  and  "washers."  At  the  International  Exhibition  (1871)  several  machines 
were  exhibited  for  performing  the  whole  process  of  brick-making  continuously.  Among 
these  was  the  three-process  brick-making  machine  of  Messrs.  Clayton,  Son,  &  Hewlett, 
of  the  Atlas  Works,  and  combining  at  one  operation  crushing,  pugging,  and  brick- 


652  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

making.  The  rough  clay  is  thrown  into  the  hopper  of  the  machine ;  in  this  hopper 
revolves  a  shaft,  upon  which  are  keyed  several  small  knives  to  cut  up  the  clay  pre- 
viously to  its  being  crushed.  It  next  passes  through  a  pair  of  crushing  rollers,  and  these 
effectually  reduce  any  stones  or  hard  lumps  of  clay  which  may  enter.  The  clay,  thus 
partially  prepared,  next  passes  into  a  horizontal  pugging  or  mixing  cylinder  situated 
beneath,  where  it  is  mixed  by  the  pug-knives  fixed  upon  the  central  shaft.  The  knives 
force  the  clay  towards  the  further  end  of  the  cylinder,  where  it  is  received  by  rollers 
and  forced  through  the  dies,  forming  a  smooth  bar  of  clay  of  the  width  and  depth  of  a 
brick.  This  bar  is  cut  into  the  required  lengths  by  wires.  The  machine  is  capable  of 
producing  20,000  to  30,000  bricks  per  diem,  and  is,  perhaps,  the  best  of  its  class. 
Mr.  Rawden  has  constructed  a  machine  in  which  no  rollers  or  crushers  are  employed, 
the  clay  being  turned  out  as  wet  and  as  soft  as  in  hand-moulding.  One  horse-power  will 
pug  the  clay  and  mould  from  12,000  to  15,000  bricks  per  day.  It  consists  of  a  square 
pug-mill,  through  which  runs  a  vertical  shaft  bearing  pug-knives.  On  the  top  of  this 
shaft,  above  its  bearing,  is  attached  the  horse-pole,  which  gives  motion  to  the  whole 
machine.  Upon  the  lower  end  of  the  shaft,  which  passes  through  the  bottom  of  the 
pug-mill,  is  a  wheel  having  two  cams,  on  which  two  rocking-arms  work.  One  arm 
presses  the  soft  clay  through  a  grating  into  a  six-brick  sanded  mould,  and  the  other 
arm  is  connected  to  a  slide  for  pushing  the  empty  sanded  moulds  under  the  grate,  the 
empty  mould  at  the  same  time  pushing  the  full  one  out.  Among  the  best  continental 
machines  are  those  of  Henschel  of  Cassel,  and  of  Karrens. 

The  moulding  of  bricks  and  tiles  is  effected  partly  by  hand,  but  chiefly  by  machinery. 
The  burning  is  effected  either  in  kilns  or  in  specially  constructed  furnaces.  They  are 
either  open  or  closed,  or  arranged  for  continuous  work,  and  burn  either  wood,  peat, 
lignite,  coal,  or  gas. 

The  brick  furnaces  with  unintermittent  action  are  coming  more  into  use.  The  first 
step  in  this  direction  was  the  furnace  of  Hoffmann  and  Licht.  It  consists  of  a  circular 
channel,  which  is  accessible  from  without  in  its  various  parts,  and  closed  at  as  many 
parts,  against  a  central  chimney.  Hoffmann's  ring  furnace  is  usually  a  smooth 
building,  3-4  metres  in  height,  and  flat  above.  The  chimney  rises  generally  in  the 
middle  of  the  masonry,  but  it  may  be  placed  externally.  The  whole  is  covered  with  a 
slight  roof  for  protection  against  the  weather.  The  furnace  itself  may  be  round,  oval, 
oblong,  three-  or  four-sided,  or  even  of  horse-shoe  shape. 

The  space  for  burning  is  a  vaulted  continuous  channel,  returning  into  itself.  This 
endless  channel  has  in  its  top  a  number  of  openings,  equally  distributed,  the  heating- 
holes.  There  are  also  a  number  of  doorways,  which  pass  through  the  outer  wall.  In 
the  inner  and  hinder  wall  of  the  burning  space  there  are  an  equal  number  of  smoke- 
flues.  A  movable  partition,  filling  up  the  entire  cross-section  of  the  burning  space,  can 
be  introduced  into  the  endless  channel,  so  that  at  its  right  hand  in  front  there  is  always 
a  doorway,  and  at  its  left,  behind,  a  smoke-flue.  Latterly,  instead  of  this,  iron 
slide-paper  has  been  used,  which  is  torn  by  means  of  a  cord  when  the  fire  is  to 
advance  into  a  chamber.  All  the  outer  doors  and  flues  can  be  closed  so  tightly  that, 
if  one  of  them  is  opened,  the  others  may  be  considered  as  non-existent. 

The  smoke-flues  open  into  the  smoke-chamber,  which  is  a  connecting  link  between 
the  burning  space  and  the  chimney,  and  may  either  lie  on  the  horizontal  plane  of  the 
burning-space  by  which  it  is  surrounded  and  protected,  or  it  can  be  placed  below, 
above,  or  outside  the  furnace. 

Of  the  following  figures,  445  shows  a  vertical  section  ;  446  in  its  upper  half  a  view 
from  above,  and  in  its  lower  half  the  ground  plan  of  a  circular  ring  furnace,  in  which  the 
movable  partition  is  introduced  from  above  through  slits  in  the  vault  of  the  furnace ; 
443  is  a  small  ground  plan  ;  444  shows  the  manner  in  which  the  smoke-flues  are  closed 
air-tight.  If  we  suppose  the  section  of  the  furnace  closed  at  one  point  by  the  intro- 


SECT,  v.]          EARTHENWARE   OR   CERAMIC    MANUFACTURE. 


65S 


duction  of  this  movable  partition ;  if  we  suppose  this  entrance  doorway  and  the 
adjoining  smoke-flue  opened,  but  all  the  other  entrance  doorways  of  the  outer  wall  and 
all  the  other  smoke  exits  of  the  back  wall  are  closed,  the  air  passes  through  the  open 
door  into  the  burning  spaces,  traverses  it  through  its  entire  length,  as  far  as  the  other 
side  of  the  movable  partition,  passes  here  through  the  open  flue  to  the  smoke-chamber,, 
and  thence  to  the  chimney. 

Fig.  444. 


Fig.  443. 


Explanation  of  Terms. 


Schieber 

Raiichsammler 

Ofencanal 


Slide. 

Smoke-collector. 

Kiln-channel. 


Raiichsammler  Smoke-collector. 

Glocke  Bell. 
Fuchs  ockr  Rauch- 

canal  Smoke-cUaunel. 


Fig.  445- 


When  the  bricks  which  are  nearest  the  open  outer  door  are  cooled  down  in  such  a 
manner  that  they  are  fit  for  removal,  their  place  is  taken  by  fresh,  unburnt  bricks. 
The  closure  of  the  furnace  is  then  effected  at  the  next  door  on  the  right  hand,  and 
behind  the  raw  bricks  which  have  just  been  put  in.  This  door  is  then  opened  and  the 
former  one  is  closed ;  in  like  manner  the  next  flue  is  opened  and  the  former  one  closed, 
and  the  fire  is  advanced  forwards  by  the  length  of  the  compartment.  By  continually 
repeating  this  process  the  fire  makes  the  entire  circuit  of  the  furnace.  Burnt  bricks 
are  simultaneously  taken  out  and  raw  ones  put  in  without  interruption.  If  we  pass 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


round  the  furnace,  setting  out  from  the  movable  partition  in  the  opposite  direction  to 
the  advancing  combustion -gases,  we  have  the  furnace-channel  on  our  light.  We  first 

pass  bricks   which   have    only 

Fig.  446.  just  been  put  in  and  are  there- 

fore still  cool ;  then  to  others 
which  are  gradually  warmer  and 
warmer,  until  in  the  middle 
of  the  circuit  we  meet  the 
full  fire.  Beyond  that  point 
we  meet  with  bricks  which  are 
still  strongly  heated  and  then 
successively  with  such  as  are 
cooler  and  cooler,  and  at  the 
first  open  door  we  find  such  as 
are  quite  cold  and  are  being 
carted  away.  At  the  next 
open  doors  the  men  are  en- 
gaged in  charging  the  furnace 
with  raw  (technically  green) 
bricks. 

According  to  the  author's 
experiments  the  charge  for  the 
fourteen  chambers  of  a  ring 
furnace  requires  seven  to  eight 
days  for  thorough  burning. 
The  highest  temperature  was 
I057°?  whilst  the  gases  escaped 
at  1 08  °  and  172°.  The  diagram, 

Fig-  447>  shows  the  rise  and  fall  of  the  temperature.  The  proportion  of  carbon  dioxide 
in  the  gases  taken  at  the  bottom  is  essentially  larger  than  under  the  vault,  and  carbon 
monoxide  is  found  only  when  the  gases  are  taken  direct  from  the  coals  introduced.  In 

Fig.  447. 


Explanation  of  Terms. 


Jtauchsammler 
Ofencanal 


Smoke-  collector. 
Kiln-chaimei. 


Einfftxen                                  Dorro^^mcj^                                 Breynen                               iMkuhten,                        ^aszittm 

'•0               tO              9^        '     8                1                 6                £ 

nTTTiji  IHiHIII'lllllllliiiililDll  III  Illlttttttltttttt^^^ 

COO  :::::::::::  :::::::::;:---  -     j, 

x      '  -*                5     ^        r  2                1                14               /«  N  ''       «" 

Miii![inilllMllll!in!M!llt!tlllllMMlllllMllllMMI'lilli!!llllll 

144444444  144  1  1          HI     HI    ilrrnt  fn  1  1  1  1  1  1  II  1  1  1  1  1  [1  1  1  1  11 

|||i§j||(fjPpp||||^^ 

3. 


Explanation  of  Terms. 


Einsetzen 
V or  war  men 
Brennen 


Putting  in. 
Preliminary  heating. 
Burning. 


AbMhlen 
Auaziehen 
Tag 


S. 


Cooling  off. 
Taking'  out. 
Day. 


ring-furnaces  a  reducing  fire  can  scarcely  occur  even 'transiently,  thus  obviating  the 
discoloration  produced  by  sulphuretted  coal.  But,  generally,  facing-bricks  of  a  good 
colour  are  more  difficult  to  produce  in  ring-furnaces  than  in  common  furnaces.  The 
quantity  of  coal  consumed  depends  on  the  quality  of  the  clay.  From  242  to  360  bricks 


SECT.  v.J          EARTHENWARE    OR    CERAMIC    MANUFACTURE. 


655 


take  T  cubic  metre  of  furnace  space.     Ring-furnaces  may  be   used  for  brick-making 
either  on  the  small  or  the  large  scale. 

Bock  has  recently  devised  a  channel  furnace  in  which  the  green  bricks,  &c.,  are 
brought  on  trucks,  meeting  the  furnace-gases  up  to  the  fire,  where  they  are  fully  burnt, 
and  as  they  pass  onwards  they  give  off  their  heat  to  the  furnace-gases.  The  propulsion 
of  the  trucks  often  involves  difficulties. 

Fig.  448. 


Gas-firing. — In  Escherich's  ring-furnace  the  gas  produced  in  the  generators,  G, 
issues  from  the  flues,  v,  into  the  pipes,  d,  built  of  hollow  stones,  and  issues  from 
numerous  lateral  openings  5  to  20  millimetres  in  width,  where  it  forms  flames  of  3  to 
20  centimetres  in  length,  at  right  angles  to  the  direction  of  the  draught  (Figs.  448  and 
449).  By  this  distribution  of  the  gas  the  bricks  themselves  are  not  touched  by  the 
flame,  and  the  composition  of  the  gases  in  the  entire  cross-section  of  the  burning 
channel  is  uniform,  so  that  the  production  of  pure  colours  is  relatively  easy.  If  a 
reducing  flame  is  required  the  access  of  air  is  moderated  by  means  of  the  smoke-valve. 


Fig.  449. 


SchnittHI. 


Section  I. -II. 


As  the  entrance  of  the  gas  and  the  exit  of  the  smoke  are  remote  from  each  other,  it  is 
possible  to  use  the  ring-channel  simultaneously  for  gas  and  smoke,  by  connecting  the 
alternating  trap  on  the  one  hand  with  the  generators,  G,  and  on  the  other  with  the 
chimney,  E.  The  tar  deposited  from  the  gas  collects  in  the  receivers,  T.  Numerous 
cross-channels,  w,  connect  the  ring-channel  with  the  furnace-chambers.  The  burning 
channel  is  itself  divided  into  four  compartments  by  the  three  bells,  V,  the  first  of 
which  is  in  direct  connection  with  the  chambers  i  to  4,  the  second  with  chambers 
5  to  8,  and  the  third  with  chambers  13  to  1 6.  By  raising  and  lowering  the  bells  the 


656 


CHEMICAL   TECHNOLOGY. 


[SECT.  v. 


connections  between  i  and  2,  i  and  3,  4  and  3,  &c.,  can  be  opened  or  closed  at  pleasure. 
By  a  suitable  placing  of  the  alternating  apparatus  each  division  of  the  ring-channel 
can  be  connected  either  with  the  generator  or  the  chimney.  The  same  flues  and  bells 
which  effect  the  introduction  and  distribution  of  the  gas  in  the  various  chambers  serve 
to  carry  off  the  smoke.  Lastly  must  be  mentioned  the  smoke  flue,  /S,  and  the  view- 
holes,  s,  introduced  between  every  two  rows  of  pipes. 

Mendheim,  of  Munich  (German  patent  22,086),  effects  a  uniform  distribution  of 
temperature  by  causing  the  generator-gas  of  each  chamber  to  enter  the  channel  b 
through  the  valves  (Figs.  450-452),  a,  and  to  pass  from  here  by  means  of  the  branch 


Fig.  450. 
achrifff.  .VI; 


Fig.  451. 


D 

3(2 

0 

Dy.   p 

D 

a 

D 

n      , 

3 

D 

a 

n 

a 

a       ad  n    D 

da 

a 

ah 

ML 

n 

8    c<z 

n 

a 

=^ 


Section  VI. 


Section  I. 


flues  c,  underneath  the  sole  of  the  furnace.  Here  a  part  of  it  passes  through  the 
openings  d,  into  the  space  filled  with  bricks,  after  heated  air  has  passed  beneath  the 
sole  from  the  flues  z,  and  has  formed  flame,  which  then  streams  from  below  upwards  ; 
another  part  of  the  gas  arises  behind  the  fire-bridges.  Here  the  gas  comes  together 
with  the  hot  air  issuing  from  the  flues  z,  in  order  to  be  conducted  through  the  charge 


Fig.  452. 


Section  II.  Section  III.  Section  IV. 

from  above  downwards.  The  entire  escape  of  the  flame  from  the  heated  chamber  takes 
place  through  the  openings  h,  so  that  both  the  fire  coming  from  the  fire-bridges  and 
that  from  the  sole  of  the  furnace  pass  unitedly  through  h,  and  the  channels  i,  v,  w,  and 
the  plate-valve,  e,  into  the  channel  /,  of  the  next  chamber  and  its  ramifications,  z. 
This  furnace  is  found  to  work  well. 

Kilns. — If  peat  or  wood  is  used  as  fuel  the  bricks  to  be  burnt  are  piled  up  in  a  heap 
much  in  the  same  manner  as  they  would  be  placed  in  a  furnace  ;  several  fire-flues  are 
left  in  the  mass,  and  the  entire  mound,  which  may  contain  50,000  bricks,  is  covered 
with  a  thin  coating  of  clay  and  protected  on  the  windward  side  with  movable  screens 


SECT,  v.]          EARTHENWARE  OR  CERAMIC  MANUFACTURE.  657 

of  straw.  The  fire  is  inserted  in  the  flues  which  have  been  left ;  the  gases  sweep  through 
the  mass  of  bricks  and  escape  at  the  top.  If  coal  is  used  as  fuel  the  flues  are  made 
narrower  than  for  peat.  Upon  every  layer  of  bricks  is  laid  a  stratum  of  small  coal, 
then  another  layer  of  bricks,  then  more  coal,  &c.  The  kiln  is  covered  with  clay,  in 
which  air-holes  are  left  to  regulate  the  burning.  The  coal  placed  in  the  flues  is  kindled, 
and  the  fire  gradually  extends  through  the  kiln. 

Clinkers  are  bricks  burnt  until  they  are  half  vitrified. 

Roofing-tiles. — For  tiles  a  better  clay  is  required  than  that  for  bricks,  and  it  must 
be  more  carefully  prepared.  Tiles  are  generally  burnt  along  with  bricks,  occupying 
the  upper  portion  of  the  kilns.  If  it  is  desired  to  produce  tiles  of  a  grey  cast,  twigs  of 
alder,  with  their  leaves  green  and  moist,  are  placed  in  the  kiln  at  its  greatest  heat, 
and  the  air-holes  are  closed.  The  smoke  thus  produced  deposits  carbon  in  the  porous 
tiles,  and  perhaps  reduces  part  of  the  iron  to  the  ferroso-ferric  state. 

Flooring-tiles. — The  manufacture  of  flooring-tiles  agrees  mainly  with  that  of 
roofing-tiles.  They  are  four-  or  six-sided,  and  are  used  for  paving  kitchens,  fore- 
courts, cellars,  &c.* 

Ballast  consists  of  clay  or  arable  soil  not  moulded  into  any  definite  forms,  but  lightly 
burnt  in  the  state  of  irregular  fragments.  The  fuel  is  partly  coal  of  the  worst  sort 
obtainable,  and  partly  the  contents  of  the  dust-bins,  i.e.,  a  mixture  of  cinders  with  very 
promiscuous  animal  and  vegetable  matter.  The  smell  given  off  is  most  disgusting,  as 
the  process  is  little  more  than  a  semi-destructive  distillation.  This  ballast  is  used  for 
making  poor  roads,  garden  walks,  &c.,  and  it  is  converted  into  an  inferior  sort  of  brick 
by  grinding  to  powder,  mixing  with  water,  and  moulding  under  powerful  pressure.  The 
use  of  such  bricks  is  one  cause  of  the  very  perishable  character  of  the  houses  run  up  by 
building  speculators. 

An  important  point  for  determining  the  value  of  bricks,  at  least  in  extreme  climates, 
is  their  resistance  to  frost.  A  clay  gave  at  different  temperatures  : 

Porosity.  Disruptive  Force. 

Per  cent.  Kilos,  per  square  centimetre. 

700°                          ...                          H'23  ...  16-5 

800                           ...                           IO'56  ...  22-4 

850                           ...                           IO'22  ...  25'2 

900                                                           9-53  ...  30-5 

960                        ...                        8-i6  ...  44-2 

1050                        ...                        2-n  ...  59-5 

Some  samples  which  had  been  burnt  at  800°  to  850°  were  frost-proof,  whilst 
facing-bricks  of  the  same  material,  and  burnt  at  the  same  heat,  were  destroyed  when  they 
had  taken  up  moisture  and  were  then  exposed  to  frost.  Bricks  with  a  porous  surface 
seem  to  resist  better  than  such  as  have  a  very  compact  and  especially  a  glazed  surface. 
According  to  Braun,  a  brick  is  frost-proof  if  its  cohesive  force  per  square  centimetre  is 
greater  than  the  expansive  force  which  the  water  absorbed  by  i  •  square  centimetre 
exerts  in  freezing.  It  would  be  desirable  to  saturate  a  brick  thoroughly  with  water  and 
then  to  expose  it  repeatedly  to  a  temperature  of  —  15°. 

The  so-called  light  bricks,  which  float  upon  water,  were  known  to  antiquity.  These 
bricks  are  mentioned  by  Posidonius  and  Strabo,  whilst  Yitruvius  and  the  elder  Pliny 
speak  of  them  as  very  important.  The  infusorial  earth  (Kieselguhr)  obtained  at 
Oberohe,  in  Hanover,  is  at  present  often  used  for  the  production  of  such  bricks. 
Kieselguhr  is  also  found  in  Skye  and  other  islands  on  the  west  coast  of  Scotland. 

Fire-bricks. — These  bricks  (known  in  Germany  as  Scharmotte-bricks  and  in 
France  as  Chamottes)  are  used  in  the  erection  of  fire-places,  furnaces,  flues,  &c.,  where 

*  These  flooring-tiles,  called  in  Germany  "  Fleissen,"  must  not  be  confounded  with  the  glazed 
and  coloured  tiles  used  by  the  ancient  Komans,  and  now  revived  as  a  material  for  hearths  and  for 
paving  churches,  entrance-halls,  &c. 

2    T 


658 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


common  bricks  would  melt.  They  are  made  of  a  clay  rich  in  silica  and  alumina,  but 
as  far  as  possible  free  from  lime,  alkali,  and  ferrous  oxide.  To  increase  its  infusibility 
and  secure  it  from  shrinkage  and  cracking,  it  is  mixed  with  clay  which  has  been 
already  burnt,  sand,  coke,  graphite,  &c.  In  the  manufacture  of  fire-bricks  it  must  be 
considered  that  there  are  two  agencies  which  imperil  their  duration — a  high  temperature 
in  itself,  and  then  the  simultaneous  attack  of  matter  which  may  act  as  a  flux,  such  as  flue- 
dust,  alkaline  vapours,  melting  alkalies,  and  metallic  oxides.  In  addition,  fire-bricks  must 
resist  great  alternations  of  temperature  and  be  firm  enough  to  bear  a  strong  pressure. 

Particular  notice  must  be  taken  of  the  action  of  slags,  &c.,  upon  the  resistance  of 
clays  to  fire.  Basic  slags  attack  quartz-stones,  whilst  acid  slags  have  no  such  action. 
Coke  burnt  in  generators  yielded  11*9  per  cent,  of  ash  of  the  following  composition  : 


Ai 

ih. 

Soluble  in 
Water. 

Total. 

Slag. 

SiO,          
ALO. 

— 

47  '9  1 

2O  "1  7 

62-95 
2<C'23 

Fe'CL 

I2"l6 

FeO          

•3-T2 

MnsO.       ..... 
MnO          

— 

0-38 

O'28 

CaO          .... 

MgO         .         . 
Na.,0         

O'24 
O'4I 
O'2O 

I-4I 
I  '22 
2  '6O 

O'46 
0-92 
0-82 

K,6           
SO,            

0-26 
0-84 

3  '34 

O-82 

3-5I 

P.O. 

O'CC 

Fe             .... 

o'o9 

FeS          

0*04 

i'95 

lOO'OI 

99-97 

The  watery  extract  is  a  basic  mixture  of  sulphates  ;  the  residual  silicate  corresponds 
with  the  formula  2RSiOs.5Al2SisO7.2SiO,. 

The  analysis  of  the  difficultly  fusible  blackish  slag  flowing  off  leads  to  the  formula 
2B,Si03.3AljSi309.2SiO,.  It  contains  no  globules  of  metallic  iron.  Hence  in  the 
generator  a  part  of  the  iron  from  the  ash  has  been  reduced  to  metal,  the  calcium  and 
magnesium  sulphates  have  been  volatilised  or  dissipated,  and  the  alkalies  have  been  con- 
verted into  slags.  The  Scharmotte  bricks,  containing  88*9  per  cent,  of  silica,  were  but 
slightly  attacked  by  this  acid  slag. 

The  worst  enemies  of  basic  bricks  are  the  oxides  of  iron,  whence,  in  using  the  earthy 
bases  for  fire-bricks,  the  utmost  possible  freedom  from  iron  should  be  aimed  at ;  silicic 
and  phosphoric  acids  and  manganese  oxides  are  not  so  destructive. 

From  the  fire-proof  mass  there  are  made  not  alone  bricks,  but  linings  for  furnaces 
in  circular  segments,  plates,  saggers  for  porcelain,  stone-ware  muffles  for  burning  in 
the  colours  for  porcelain  vessels,  and  apparatus  for  chemical  works,  dye-houses,  and 
paper  manufactories  (chlorine  stills),  capsules,  dehydrating  plates,  cocks,  gas-retorts,  <fec. 
Some  analyses  of  fire-bricks  gave  the  following  results  : — 




i 

3 

3 

4 

5 

Silica    .... 

00.  T 

CO..., 

Alumina        .... 

so  43 

09  3 

77  *> 

Lime     .... 

5 

29  5 

Magnesia 

0*66 

3  4° 

•«n 

Ferric  oxide  .... 

2-88 

fi'T 

Potassa 

T  'O2 

5° 

3 

Soda      

u  Ol 

lOO-SS 

99  -9 

100-23 

ioo-8 

997 

SECT,  v.]  MORTARS,  ETC.  659 

No.  i  was  clay  from  Dowlais;  2,  bricks  from  copper  furnaces  in  Wales;  3,  in 
Pembroke;  4,  for  blast-furnaces ;  5,  for  reverberatories. 

The  Dinas  bricks  made  from  the  Dinas  rock  in  the  Yale  of  Neath  in  Glamorgan, 
consist  of  almost  pure  quartz  sand  and  i  per  cent,  of  lime.  They  bear  the  highest 
temperatures  occurring  in  metallurgical  work  without  melting  or  shrinking  too  much, 
and  are,  hence,  invaluable  for  steel  furnaces,  all  kinds  of  reverberatories,  glass  ovens, 
porcelain  ovens,  &c.  Yery  similar  is  ganister,  a  compact,  siliceous  stone,  which, 
when  ground  and  mixed  with  clay,  serves  for  lining  Bessemer  converters,  puddling 
furnaces,  &c. 

Wasum  shows  that  good  bricks  may  be  obtained  at  a  white  heat  from  dolomite  and 
limestone,  but  not  from  magnesite.  The  addition  of  5  per  cent,  of  clay  yields  better 
bricks  without  rendering  them  much  less  fire-proof.  The  higher  the  temperature  at 
which  the  bricks  are  burnt  the  more  durable  they  become.  In  the  construction  of 
furnaces  for  burning  such  bricks  it  is  important  to  arrange  the  flues  so  that 
the  temperature  may  be  equal  throughout.  Dolomite  and  limestone  bricks,  if 
not  too  much  contaminated  with  matters  which  increase  fusibility,  shrink  at  the 
strongest  white  heat  only  about  2*4  per  cent. ;  bricks  made  of  strongly  burnt  magnesia 
shrink  only  4  per  cent.  All  substances  which  decrease  the  resistance  of  basic  bricks  to 
fire  increase  their  shrinkage.  Bricks  of  limestone  and  dolomite  are  equally  attacked 
by  the  slags  formed  in  iron-smelting,  while  magnesia  bricks  are  more  resistant.  The 
best  material  for  basic  bricks  is  magnesia  burnt  at  the  utmost  white  heat. 

Clay  pipes  may  serve  either  for  water-mains  or  for  drain-pipes.  Both  are  made 
by  means  of  a  mould  and  stamp. 

Crucibles. — For  crucibles  it  is  necessary  that  materials  shall  be  used  that  will  with- 
stand the  highest  temperature.  Good  crucibles  do  not  crack  on  being  rapidly  cooled, 
and  they  must  also  withstand  the  action  of  the  fluxes  that  may  result  from  the  smelting 
of  metals.  The  most  common  crucibles  are  the  Hessian,  the  graphite  or  plumbago,  and 
the  English.  The  Hessian  crucible  is  made  of  i  part  clay  (of  71  parts  silica,  25  parts 
alumina,  and  4  oxide  of  iron)  and  one-half  to  one-third  the  weight  of  quartz  sand. 
They  are  refractory,  remain  unaltered  by  variations  in  temperature,  but  are  unsuited  to 
some  chemical  operations  on  account  of  coarseness  of  grain  and  porosity.  If  containing 
too  large  a  proportion  of  silica,  they  become  perforated  by  lead  oxide,  alkalies,  &c. 
Graphite  or  plumbago  crucibles  are  made  from  i  part  of  refractory  clay  and  3  to  4 
parts  graphite.  The  Patent  Plumbago  Crucible  Company,  of  Battersea,  as  well  as  the 
Nuremberg  manufacturers,  employ  Ceylon  graphite  and  fire-clay.  Graphite  crucibles 
will  bear  the  highest  temperature,  and  they  can  be  made  to  almost  any  required  size. 
English  crucibles  are  made  from  2  parts  of  Stourbridge  clay  and  i  part  of  coke.  Crucibles 
containing  coke  exert  a  reducing  action  when  heated  in  contact  with  metallic  oxides,  and 
are  therefore  unfitted  to  the  smelting  of  metals.  Recently  lime  and  chalk  crucibles  have 
been  employed  for  this  purpose.  Caron  has  used  magnesia  crucibles  in  the  smelting  of 
iron  and  steel.  Gaudin  employs  an  equal  mixture  of  bauxite  or  cryolite  and  magnesia. 
Yery  similar  are  the  bauxite  crucibles  of  Audouin. 

MORTARS,  ETO. 

The  substances  used  for  the  production  of  mortars  are  either  sufficiently  comminuted 
by  the  action  of  water  (lime),  or  they  are  ground  up  by  mechanical  means.  They  are 
divided  into — 

A.  Such  as  set  only  in  the  air. 

1 .  Gypsum  must  be  mechanically  pulverised,  and  sets  by  combining  with  water. 

2.  Lime   when   moistened    with   water   crumbles  to   a   powdery   hydroxide,  and 
hardens  with  sand  by  the  formation  of  a  silicate  (ordinary  mortar). 

B.  Such  as  set  either  in  the  air  or  under  water  (hydraulic  cements). 


660  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

3.  Hydraulic  Limes,  obtained  by  burning  limestones  containing  more  or  less  clay 
and  silica,  and  fall  to  powder  on  slacking  with  water. 

4.  Roman  Cements,  formed  from  clayey  calcareous  marls  by  burning  below  the  limit 
of  sintering.     They  do  not  slack  when  moistened  with  water,  but  have  to  be  pulverised 
mechanically. 

5.  Portland  Cements  are  obtained  from  calcareous  marls,  or  from  artificial  mix- 
tures of  lime  and  clay  heated  to  sintering  and  then  grinding  to  a  fine  powder.    They 
contain  to  i  part  of  SiO,,  A12O3, Fe203,  r8  to  2-2  of  lime,  and  their  specific  gravity  w 

above  3. 

6.  Hydraulic  admixtures  are  natural  or  artificial  substances  which  do  not  harden 
alone,  but  only  in  conjunction  with  caustic  lime,  e.g.,  puzzuolane,  blast-furnace  slags, 
and  trass  obtained  from  volcanic  tufa. 

7.  Puzzuolane  Cements  are  obtained  by  a  very  intimate  mixture  of  pulverulent  cal- 
cium hydroxide  with  trass,  &c. 

8.  Mixed  Cements,  made  by  adding  other  matters  to  prepared  cements. 

Gypsum. — Gypsum  is  a  hydrated  catcium  sulphate  of  the  formula  CaS04  +  2H80. 
100  parts  contain — 

Lime       .        .        .        32*56 

Sulphur        .        .         1 8 -60) 

-  Sulphuric  acid        .        46x1 
Oxygen         .         .         27-91! 

Water      .        .         .         20-93 


It  belongs  to  the  commonly  occurring  class  of  minerals,  and  is  found  alone  or  with 
anhydrite  (karsenite,  CaS04)  in  strata  chiefly  of  the  tertiary  formation.  The  following 
kinds  are  distinguished  : — (i)  Gypsum  spar,  foliated  gypsum,  glass  stone,  isinglass  stone, 
or  selenite,  possessing  a  very  perfect  cleavage,  and  allowing  fine  laminae  to  be  sepa- 
rated ;  (2)  Fibrous  gypsum,  or  satin  spar ;  (3)  Froth-stone,  a  scaly  crystalline  gypsum ; 
(4)  Granular  gypsum,  or  alabaster,  of  coarse  or  fine-grained  texture ;  (5)  Gypsum  stone, 
plaster  stone,  or  heavy  stone,  a  laminated  gypsum ;  (6)  Earthy  gypsum,  or  plaster 
earth. 

Nature  of  Gypsum. — Gypsum  is  soluble  in  445  parts  of  water  at  14°  C.,  and  in  420 
parts  at  2O'5°  C. ;  the  solubility  is  increased  by  the  addition  of  sal-ammoniac.  Its  be- 
haviour under  the  influence  of  heat  is  important.  Graham  states  that  gypsum  placed 
in  a  vacuum  over  sulphuric  acid,  and  heated  to  100°  C.,  loses  its  water,  forming  the  com- 
bination CaS04  +  H2O,  with  12-8  per  cent,  water.  According  to  Zeidler,  the  statement 
that  this  combination  does  not  harden  with  water  is  incorrect.  By  heating  to  90°  for 
some  time  15  per  cent,  of  the  water  may  be  expelled ;  at  170°,  according  to  the  experi- 
ments of  Zeidler,  all  the  water  will  be  given  off.  But  of  more  importance  are  the  ex- 
periments not  carried  on  in  vacua.  In  the  air  gypsum  begins  to  lose  its  water  at  100°, 
and  the  loss  is  not  complete  under  132°.  Gypsum  from  which  all  the  water  has  been 
removed  is  termed  burnt  gypsum,  or  spar-lime ;  it  has  the  property  of  re-forming  with 
water  the  same  hydrate,  thus  becoming  hardened.  Advantage  is  taken  of  this  property 
in  the  application  of  gypsum  as  a  mortar.  According  to  Zeidler,  gypsum  as  technically 
employed  in  stucco-work,  &c.,  is  not  anhydrous,  but  contains  5-27  per  cent,  water.  If 
gypsum  is  "  over  burnt,"  that  is,  heated  above  204",  it  loses  the  property  of  hardening 
with  water,  probably  owing  to  the  fact  of  its  being  converted  into  anhydrite,  which 
does  not  re-combine  with  water. 

The  water  of  crystallisation  of  the  gypsum  is  saline,  and  consequently  can  be  re- 
moved by  the  addition  of  salts  ;  this  probably  accounts  for  the  hardening  of  unburnt 
gypsum  when  treated  with  a  dilute  solution  of  potassium  sulphate  or  carbonate, 
&c.  The  hardening  in  this  follows  more  quickly  than  with  burnt  gypsum  and  pure 
water.  With  potassium  sulphate  a  double  salt  is  formed  according  to  the  formula 


SECT.   V.] 


MORTARS,  ETC. 


661 


K,S04  +  CaS04  +  H20  ;  gypsum  and  potassium  bitartrate  give  rise  to  tartar  and  crys- 
talline gypsum.  Potassium  chlorate  and  nitrate,  as  well  as  sodium  salts,  do  not  effect 
the  hardening  of  powdered  gypsum.  Gypsum  thus  hardened,  if  re-powdered  and  again 
treated  with  potassium  sulphate  or  carbonate  solution,  hardens  once  more.  Technical 
use  is  made  of  this  property  in  re-hardening  old  or  in  hardening  gypsum  not  sufficiently 
burnt,  by  employing  instead  of  water  a  solution  of  potassium  carbonate. 

The  Burning  of  Gypsum. — Gypsum  is  burnt  to  effect  the  removal  of  the  water. 
Lately  many  improvements  have  been  made  in  the  methods  of  burning,  it  having  been 
found  that  the  good  qualities  of  the  gypsum  mainly  depend  upon  the  preparation.  There 
is,  however,  a  choice  in  the  stone  to  be  burnt,  the  heavier  and  denser  varieties  of  gypsum 
yielding  the  best  commercial  article. 

Payen,  by  experimenting  with  large  quantities  of  gypsum,  obtained  the  following 
results : — (a)  The  lowest  temperature  at  which  gypsum  can  be  burnt  \vith  advan- 
tage is  80°  C.,  a  long  time  even  then  being  required.  (6)  A  temperature  of  110°  to 
120°  yields  the  best  technical  preparation,  (c)  In  order  that  the  burning  may  take 
place  equally,  the  gypsum  should  be  first  reduced  to  powder  or  small  pieces.  The  aim, 
of  course,  is  in  all  cases  to  obtain  a  small  homogeneous  product  rather  than  a  large 
quantity  unequally  burnt.  Small  quantities  of  gypsum  may  be  burnt  in  an  iron  vessel 
over  a  coal  fire ;  the  operation  should  be  continued  till  no  aqueous  vapour  is  condensed 
on  a  cold  glass  plate. 

Kilns,  or  Burning  Ovens. — In  large  quantities  gypsum  is  burnt  in  an  oven  or  kiln, 
the  one  necessary  precaution  being  to  avoid  arranging  the  layers  of  gypsum  with  such 
fuel  as  will  reduce  the  gypsum  to  calcium  sulphide  (CaS04  +  40  =  CaS  +  4CO). 

A  very  simple  and  very  general  construction  of  kiln  is  shown  in  Fig.  453.  It  con- 
sists of  walls  of  strong  masonry,  A,  spanned  by  a  flat  arch,  ventilated  at  a  a  a.  In  this 
room  is  placed  the  gypsum  only,  the  fire  being  lighted  in  a  series  of  small  chambers  in 
the  lower  part  of  the  room :  brushwood  is  the  best  fuel.  &  is  a  door,  through  which  the 
material  is  introduced.  The  oven  (Fig.  454)  used  by  M.  Scan°gatty  is  very  similar. 


The  inner  room  is  divided  unequally  by  an  arch,  P,  about  one  foot  from  the  floor  ;  into 
the  upper  part  the  gypsum  is  introduced  through  the  door,  G.  The  under  part  or  fire- 
room  is  in  connection  with  a  flue,  E,  of  a  furnace,  A  A,  the  flames  from  which,  driven 
by  the  draught  from  the  gallery,  (7,  are  carried  through  X  to  play  upon  the  arch,  P,  the 
hot  air  and  gases  passing  through  c  c  c  into  the  upper  room.  The  aqueous  vapour 
escapes  through  H. 


662 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


Lately  Dumesnil's  oven,  shown  in  plan  at  Fig.  455,  and  in  section  Fig.  456,  has  been 
much  employed.  It  somewhat  resembles  Scanegatty's  oven  in  construction,  and 
consists  of  an  under  fire-room  and  an  upper  room  or  oven,  in  which  the  gypsum  is 
burnt.  The  fire-room  contains  an  ash-pit,  A,  with  a  door,  B,  a  grate  or  grid,  C,  and  the 
hearth,  D.  A  draught,  H,  assists  the  combustion.  The  hot  air  and  gases  pass  by  the 
flues,  E,  to  the  chamber,  F.  The  walls  of  the  oven,  J,  K,  L,  are  of  solid  masonry.  I  is 
a  vault,  furnished  with  a  staircase,  g  h,  to  facilitate  access  to  the  furnace.  P,  the 
chimney,  is  of  iron  plate,  with  a  clack,  Q,  which  can  be  regulated  by  the  chain  U  U. 
O  O  are  ventilating  pipes.  In  the  wall  of  the  burning-room  are  two  openings  —  one,  M, 
through  which  admittance  to  the  interior  is  gained  to  place  the  lower  layers  of 
gypsum  ;  the  other,  N,  for  the  upper  layers  of  gypsum  :  both  are  closed  by  doors  of  iron 
plate.  An  equal  heat  is  necessary  in  the  burning-room,  and  is  maintained  by  the 
peculiar  arrangement  of  the  chamber  F.  This  chamber,  closed  at  the  top  by  the  cap, 


Fig.  456. 


Fig.  455- 


G,  is  provided  with  twelve  openings,  each  07  metre  high,  the  chamber  itself  being 
i  metre  in  diameter.  The  channels  thus  commenced  by  the  openings  in  F  are  continued 
to  the  walls  of  the  room  by  the  arrangement  of  large  blocks  of  gypsum.  The  layers 
of  gypsum,  R,  S,  T,  are  placed  crosswise  alternately  with  intermediate  layers,  so  as  to 
facilitate  the  draught  in  every  possible  way.  The  firing  is  continued  gently  for  four 
hours,  then  strengthened  for  eight  hours,  when  all  the  openings  are  closed,  and  5  to 
6  cubic  metres  of  coarse  gypsum  powder  spread  equally  over  the  top  of  the  burning 
gypsum.  By  this  means  the  quantity  of  burnt  gypsum  is  increased  without  a  further 
expenditure  of  fuel.  After  standing  twelve  hours  in  the  oven  to  cool  the  whole 
contents  are  removed. 

Grinding  the  Gypsum. — After  the  burning  the  gypsum  is  to  a  certain  extent  in 
powder,  but  if  not  sufficiently  even  it  has  to  be  ground.  The  usual  modes  of  grinding  are 
in  a  stamp  or  roller  mill.  After  grinding,  the  gypsum  is  sifted,  and  placed  in  some 
position  where  damp  cannot  affect  it.  Sometimes  the  grinding  and  sifting  are 
conducted  in  one  apparatus ;  generally  the  mill  and  sieves  are  separate. 

Uses  of  Gypsum. — Gypsum  is  employed  industrially  in  very  many  ways.  It  is 
sometimes  used  unburnt  in  building ;  it  is  then  difficult  to  manipulate  with  water,  but 
becomes  plastic  by  continued  moistening.  The  heavy  and  strong  fine-grained  gypsum, 
especially  the  white  powdered  gypsum,  is  used  in  building  for  decorative  purposes. 
From  the  alabaster  of  Voltena,  Florence  vases  of  great  beauty  were  fabricated  ;  the 
same  material  is  used  for  making  Roman  pearls.  The  clear  varieties  of  gypsum  are 
used  in  the  manufacture  of  cheap  jewellery,  being  ground  and  polished.  The  fibrous 
gypsum  is  sometimes  used  for  writing  sand,  as  a  substitute  for  pounce,  &c.  Fine 


SECT,  v.]  MORTARS,  ETC.  663 

gypsum  powder  is  an  ingredient  of  porcelain  manufacture.  Unburnt  gypsum  finds, 
further  application  in  the  conversion  of  ammonium  carbonate  into  sulphate.  Gypsum 
contains  46-5  per  cent,  sulphuric  acid  and  i8'6  per  cent,  sulphur.  It  is  largely 
employed  in  agriculture  as  a  manure,  both  burnt  and  unburnt.  It  is  generally 
agreed  that  the  favourable  action  of  the  gypsum  upon  vegetation  is  due  to  the 
absorbed  ammonia  which  is  again  yielded  up. 

Putridity  gives  rise  to  the  formation  of  carbonic  acid,  which  combines  with  the 
lime  of  the  gypsum,  leaving  calcium  carbonate  and  ammonium  sulphate.  This  explana- 
tion of  the  efficacy  of  gypsum-manuring,  as  it  is  termed,  is,  however,  insufficient. 
The  investigations  of  Mayer  have  shown  that  in  clayey  soils  the  iron  oxide,  &c., 
affords  larger  and  better  combinations  with  ammonia  than  gypsum.  The  quantity 
of  gypsum  used  is  generally  about  5  cwts.  to  the  acre,  containing  and  realising  at  the 
most  2 '7  cwts.  of  ammonium  carbonate.  Mayer's  researches,  however,  show  that  in 
an  acre  of 

Field  land        .        .        .        227  cwts. 

Chalky  soil       .        .         .         158     „ 

of  ammonia  were  contained.  According  to  Liebig's  late  researches  (1863)  it  appears 
that  the  gypsum  gives  up  to  the  earth  a  portion  of  its  lime  in  exchange  for  magnesia 
and  potash.  But  it  must  be  borne  in  mind  that  pulverised  gypsum,  as  well  as 
unburnt  gypsum,  when  brought  into  contact  with  a  solution  of  potash,  sets  into  a 
difficultly  soluble  mass.  We  must,  then,  wait  for  an  adequate  theory  until  the  several 
reactions  have  been  more  closely  studied.* 

Gypsum  Casts. — The  employment  of  gypsum  in  casting,  and  in  all  cases  where 
impressions  are  required,  is  very  extensive.  A  thin  paste  of  i  part  gypsum  and  2^ 
parts  water  is  made :  this  paste  hardens  by  standing,  forming  CaS04  +  2H2O.  The 
hardening  of  good,  well-burnt  gypsum  is  effected  in  one  or  two  minutes,  and  more 
quickly  in  a  moderate  heat.  Models  are  made  in  this  substance  for  galvano-plastic 
purposes,  for  metallic  castings,  and  for  ground  works  in  porcelain  manufacture.  The 
object  from  which  the  cast  is  to  be  taken  is  first  well  oiled,  to  prevent  the  adhesion  of 
the  gypsum.  Where  greater  hardness  is  required  a  small  quantity  of  lime  is  added ; 
this  addition  gives  a  very  marble-like  appearance,  and  the  mixture  is  much  employed 
in  architecture,  being  then  known  as  gypsum-marble  or  stucco.  The  gypsum  is 
generally  mixed  with  lime-water,  to  which  sometimes  a  solution  of  zinc  sulphate  is 
added.  After  drying,  the  surface  is  rubbed  down  with  pumice-stone,  coloured  to 
represent  marble  and  polished  with  Tripoli  and  olive-oil.  Artificial  scaliogla  work  is 
largely  composed  of  gypsum.  Gypsum  is  also  much  employed  in  the  manufacture  of 
paper. 

Hardening  of  Gypsum. — There  are  several  methods  of  hardening  gypsum.  One  of 
the  oldest  consists  in  mixing  the  burnt  gypsum  with  lime-water  or  a  solution  of  gum- 
arabic.  Another,  yielding  very  good  results,  is  to  mix  the  gypsum  with  a  solution  of 
20  ounces  of  alum  in  6  pounds  of  water ;  this  plaster  hardens  completely  in  fifteen 
to  thirty  minutes,  and  is  largely  used  under  the  name  of  marble  cement.  Parian  cement 
is  gypsum  hardened  by  means  of  borax,  i  part  of  borax  being  dissolved  in  9  parts  of 
water,  and  the  gypsum  treated  with  the  solution.  Still  better  results  are  obtained  by 
the  addition  to  this  solution  of  i  part  of  cream  of  tartar. 

The  hardening  of  gypsum  with  a  water-glass  solution  is  found  difficult,  and  no 
better  results  are  obtained  than  with  ordinsny  gypsum.  Fissot  obtains  artificial  stone 
from  gypsum  by  burning  and  immersion  in  water,  fii-st  for  half  a  minute,  after  which 

*  The  use  of  gypsum  in  manures  has  proved  less  satisfactory  in  Britain  than  on  the  Continent. 
It  plays-  no  small  part  in  the  sophistication  of  articles  of  consumption,  such  as  flour,  wines,  sweet- 
meats, &c.  Its  chief  locality  in  Britain  is  in  the  neighbourhood  of  Newark-upon-Trent. 


664  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

it  is  exposed  to  the  air,  and  again  for  two  to  three  minutes,  when  the  block  appears 
as  a  hardened  stone.  It  would  seem  from  this  method  that  the  augmentation  in 
hardness  is  due  to  a  new  crystallisation.  Hardened  gypsum,  treated  with  stearic  acid 
or  with  paraffine,  and  polished,  much  resembles  meerschaum :  the  resemblance  may 
be  increased  by  a  colouring  solution  of  gamboge  and  dragon's  blood,  to  impart  a  faint 
red-yellow  tint.  The  cheap  artificial  meerschaum  pipes  are  manufactured  by  this 
method. 

Scott's  "  gypsum  cement "  or  "  selinitic  mortar "  was  made  by  the  action  of  the 
fumes  of  burning  sulphur  upon  ignited  lime.  Schott  has  since  pointed  out  that  it  can 
be  more  simply  obtained  by  igniting  quicklime  with  burnt  calcium  sulphate. 

Tripolite  is  merely  gypsum  with  impurities  of  sand,  calcium,  and  magnesium 
carbonate,  and  burnt  with  o'i  of  its  weight  of  coal  or  coke. 

Lime. — Lime,  calcium  oxide  (CaO  =  56),  in  its  combination  with  carbonic  acid  as 
calcium  carbonate  (CaC03),  is  a  substance  of  very  frequent  occurrence.  It  is  a  con- 
stituent of  bone,  of  the  shells  of  the  mollusca,  and  is  found  most  extensively  in  the 
mineral  kingdom  as  marble,  limestone,  coral,  Iceland  spar,  arragonite,  chalk,  &c.  Its 
technical  applications  are  as  marble  in  building,  in  the  manufacture  of  artificial  mineral 
waters,  as  Iceland  spar  for  optical  purposes,  as  chalk  in  colours  and  drawing  materials, 
in  the  manufacture  of  soda,  in  the  preparation  of  hydraulic  mortars,  building  and 
plastering  materials,  &c.  Limestone,  Alpen  lime,  lias  lime,  Jura  lime,  &c.,  is,  when 
mixed  with  clay,  iron,  and  other  metallic  oxides,  used  as  a  colour.  Lithographic  stone 
is  a  yellow-white  limestone,  employed,  as  its  name  implies,  in  lithography.  Chalk  or 
earthy  calcium  carbonate  occurs  in  strata  in  North  Germany,  Denmark,  France,  and 
England.  To  this  class  belongs  marl-limestone,  distinguished  by  containing  clay. 
With  sodium  carbonate,  calcium  carbonate  forms  Gay-Lussite  (CaC03  +  Na2C03) ;  with 
barium  carbonate,  baryto-calcite  (BaC03  +  BaC03)  ;  and  with  magnesium  carbonate, 
bitter-spar  or  dolomite  (CaC03  +  3MgC03),  the  latter  occurring  with  3  mols.  of 
magnesium  carbonate  to  i  mol.  of  lime. 

Properties. — Calcium  carbonate  is  not  soluble  in  pure  water  ;  but  if  the  water  should 
hold  carbonic  acid  in  solution,  bicarbonate  is  formed.  When  this  solution,  by  means 
of  evaporation,  loses  half  its  carbonic  acid,  an  insoluble  carbonate  is  formed.  In  this 
manner  are  naturally  formed  stalactites  and  stalagmites.  The  deposit  of  calc-sinter  upon 
objects  deposited  in  caverns,  in  limestone-rock,  &c.,  is  thus  explained.  When  calcium 
carbonate  is  ignited  to  whiteness  in  a  porcelain  crucible,  the  carbonic  acid  is  disengaged, 
and  there  remains  calcium  oxide  (CaO)  or  caustic  lime.  TOO  parts  of  calcium  car- 
bonate yield  56  parts  of  burnt  lime.  The  volume  of  the  lime  undergoes  no  diminution 
by  burning.  Burnt  lime  is  the  form  under  which  lime  most  commonly  appears  in  the 
market.  Calcium  carbonate,  heated  in  a  closed  porcelain  tube,  melts,  and  forms  a  crys- 
talline mass,  a  carbonate,  afterwards  unalterable. 

Lime-Burning. — The  burning  of  lime  is  effected — 

In  kilns, 

In  field-ovens,  and 
In  lime- ovens. 

Lime-burning  in  kilns  is  accomplished  in  the  following  manner  : — The  limestone, 
unless  it  has  previously  been  broken  into  small  pieces,  is  heaped  up  into  cairns  similar 
to  the  heaps  of  wood  to  be  converted  into  charcoal.  The  kiln  is  then  covered  with  earth 
or  turf,  and  the  fire  so  placed  that  the  larger  pieces  of  lime  in  the  interior  of  the  heap 
are  burnt.  The  regulating  of  the  draught,  the  kindling,  the  covering,  and  the  cooling 
are  on  the  same  principle  as  that  followed  by  the  charcoal-burner  in  the  conversion  of 
wood  into  charcoal  by  combustion.  According  to  P.  Loss,  a  kiln  of  this  kind,  4-5  metres 
in  height,  contains  35-5  cubic  metres  of  lime  as  well  as  2'6  cubic  metres  of  lime-dust. 
In  the  field-ovens  the  burning  is  similarly  conducted,  but  sometimes  on  a  larger  scale, 


SECT.    V.] 


MORTARS,  ETC. 


665 


the  kilns  being  always  temporary.  It  is  easy  to  see  that  the  burning  in  this  manner 
is  only  of  slight  technical  importance  ;  besides  the  great  waste,  only  a  small  quantity 
could  be  produced  at  an  operation.  Therefore,  permanent  ovens  are  employed.  These 
are  divided  into — 

a.  Those  kilns  in  which  the  burning  is  interrupted,  or  occasionally  employed  (the 

occasional  kiln). 

b.  Those  kilns  in  which  the  burning  is  continuous  (the  continuous  kiln). 

In  the  occasional  kiln,  after  the  burning  is  finished,  the  kiln  is  cooled,  and  the  lime 
then  removed.  In  the  continuous  kiln,  on  the  contrary,  the  calcination  is  continuous, 
the  kiln  never  being  allowed  to  cool.  It  is  so  constructed  that  the  burnt  lime  can 
be  removed  and  fresh  limestone  introduced,  without  in  the  least  interrupting  the 
process.  The  continuous  kiln  has  many  recommendations — among  them  that  of  effecting 
a  saving  in  fuel.  In  a  small  way,  where,  as  a  rule,  burning  cannot  be  constantly  carried 
on,  the  small  occasional  kiln  is  of  course  to  be  preferred. 

Occasional  or  Periodic  Kilns. — The  occasional  or  periodic  kiln  with  interrupted  burn- 
ings sometimes  have,  and  sometimes  have  not,  a  grated  furnace.  Figs.  457  and  458 


Fig.  458. 


Fig-  457- 


show  two  lime-kilns  of  the  ordinary  construction  without  grated  furnaces.  They  are 
built  either  on  the  slope  of  a  hill  or  on  the  slope  of  the  limestone  quarry  itself.  As  a  rule, 
the  kilns  are  built  near  one  another,  so  that  one  wall  serves  for  two  kilns.  The  height 
of  the  vault  varies  from  1-3  to  r6  metre,  and  it  is  generally  built  of  the  largest  lime- 
stones, while  the  smaller  stones  and  lime-dust  are  placed  in  the  interior  of  the  kiln. 
Through  the  furnace  doors,  easily  combustible  fuel,  such  as  brushwood,  light  timber, 
shavings,  &c.,  is  introduced.  The  mass  becomes  gradually  heated,  the  larger  stones 
crack  and  break  up,  and  the  whole  mass  sinks  together.  As  the  firing  is  increased  the 
lime  becomes  of  a  brighter  colour  and  the  flames  free  from  smoke.  As  soon  as  the  lime 
immediately  under  the  stones  on  the  top  of  the  kiln  is  at  a  white  heat  the  burning 
is  complete.  The  mass  by  this  time  will  have  sunk  one-sixth.  A  burning  generally 
occupies  thirty-six  to  forty-eight  hours.  An  occasional  kiln  with  a  grated  furnace 
effects  a  quicker  and  more  complete  combustion  of  the  fuel ;  but  they  are  open  to  the 
objection  that  the  consumption  is  greater.  On  the  other  hand,  the  kilns  without  a  grated 
furnace  are  less  perfectly  heated.  A  kiln  much  used  in  Hanover  is  shown  in  Fig.  459, 
and  in  plan  in  Fig.  460 ;  Fig.  461  shows  the  under  part  of  the  kiln  in  vertical  section. 
The  lower  room  serves  for  the  calcination  of  the  lime  ;  over  this  is  a  vaulted  chamber 
3-12  metre  in  diameter  and  u  feet  in  height,  e  e  e  e,  Figs.  460  and  461,  are  four 
stoke-holes  for  the  introduction  of  fuel,  stone-coal,  brown-coal,  breeze,  &c.  B  is  the 
approach  by  which  the  limestone  is  introduced  into  the  furnace;  d  the  door  by  which 
entrance  is  obtained  to  remove  the  burnt  lime.  Both  these  openings  are  closed  during 


666 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


the  actual  burning,  a  is  an  approach  to  the  "  upper  jacket,"  as  the  upper  chamber  ia 
termed.  This  opening  is  necessary  as  a  draught  to  assist  the  flame  and  hot  gases  in 
their  escape  from  the  top  of  the  kiln  ;  it  also  causes  a  more  intense  flame  in  other  parts 
of  the  kiln.  Figs.  460  and  461  show  how  the  limestone  is  kept  clear  of  the  hearths. 

A  piece  of  wood  is  placed  ver- 

Fig.  459.  tically  in  the   centre  of   the 

I  oven  to  direct  the  flames  up- 

wards when  the  fire  is  lighted. 
During  the  first  six  hours  the 
fire  is  weak  ;  then  a  stronger 
fire  is  obtained  until  the  yellow 
lime-flames  spring  from  the 
openings  in  the  vault,  and  the 
oven  is  in  a  clear  glow. 

The  Continuous  Kilns. — 
The  construction  of  the  kilns 
for  continuous  burning  is  some- 
what different  to  that  of  the 
preceding.  They  are  of  two 
kinds.  In  one  the  fuel  and 
the  Jimestone  are  placed  in 
alternate  layers ;  in  the  other 

kind,  the  fuel  and  the  limestone  are  not  in  contact,  there  being  furnaces  for  the 
former  and  separate  chambers  for  the  latter.  In  either,  fresh  limestone  is  added  in 
proportion  as  the  burnt  stone  is  removed  from  the  bottom  of  the  kiln. 

Fig.  460. 


Fig.  461. 


At  Rudersdorf,  near  Berlin,  a  very  efficient  kiln  is  employed,  shown  in  section  in 
Fig.  462.  The  lining  wall  of  the  shaft,  d,  is  built  of  fire-brick;  the  counter  wall,  e,  is 
separated  from  the  lining  wall  by  a  chamber  filled  with  ashes,  building  refuse,  &c. 
The  outer  wall,  B  J3,  is  not  an  essential  portion  of  the  kiln  ;  it  serves  merely  as  a  jacket 
for  the  retention  of  the  heat,  while  the  galleries,  H  and  F,  can  be  used  as  drying-rooms 
for  wood,  fuel,  &c.  During  the  process,  the  under  part,  B,  of  the  shaft  is  filled  with 
prepared  lime,  which  is  removed  by  the  draught-hole,  a,  in  the  sole  of  the  shaft.  For 
the  purpose  of  hastening  the  descent  of  the  burnt  lime,  the  sides  of  the  lower  part 


SECT,  v.]  MORTARS,  ETC.  667 

of  the  shaft  are  sloped  towards  the  draught-holes.  The  shaft  is  usually  14*123  metrea 
in  height.  About  4  metres  above  the  sole  of  tha  shaft  is  situated  the  fire-room,  h. 
Three  to  five  fire-rooms  are  in  action  in  a  single  shaft.  The  fuel  is  wood  or  turf,  i  is 
the  ash-pit,  whence  the  ashes  fall  into  E.  The  flame  enters  the  shaft  through  the 
opening,  6,  at  the  end  of  the  fire-room.  The  freshly  burnt  lime  is  received  in  F.  K  K 
is  a  draught  gallery  communicating  with  H.  The  kilns  are  locally  known  as  three-, 
four-,  or  five-fired  kilns,  according  to  the  number  of  fire-rooms.  Should  the  kiln  not 
have  been  in  use  for  some  time,  the  firing  is  commenced  by  adding  fuel,  such  as  wood, 
turf,  &c.,  to  the  limestone  in  the  shaft.  When  the  shaft  is  thoroughly  warmed  and  a 
good  draught  obtained,  lime  only  is  introduced  into  the  shaft.  The  shaft  is  entirely 
filled  with  limestone,  and  sometimes  the  limestone  accumulates  upon  the  mouth  or  top 
of  the  kiln  to  a  height  of  1-3  metre. 

Kilns  far  Burning  Lime  and  Bricks. — When  the  locality  is  favourable,  the  kilns 
are  arranged  to  burn  both  lime  and  bricks  at  the  same  time.  The  annular' kiln  of 
Hoffmann  and  Licht,  described  under  Brick-making,  is  the  most  suitable  for  this  double 
purpose. 

Properties  of  Lime. — The  quality  of  the  burnt  lime  is  greatly  influenced  by  the 
constitution  of  the  limestone  burnt.  When  the  limestone  consists  chiefly  of  pure 
carbonate  of  lime,  the  resulting  lime  is  what  «is  termed  a  "  fat "  lime.  On  the  other 
hand,  if  the  limestone  is  of  similar  composition  to  dolomite  (Ca003  +  MgC03),  containing 
magnesia,  the  resulting  lime  forms  a  short,  thin  "  milk  "  with  water,  and  istermed  "  poor." 
With  10  per  cent,  of  magnesia  the  lime  is  noticeably  poor,  and  with  25  to  30  per  cent, 
almost  useless.  The  lime  on  being  taken  from  the  kiln  is  by  no  means  found  to  be 
burnt  equally.  Some  pieces  that  have  almost  escaped  the  fire  are  merely  superficially 
burnt,  and  contain  a  kernel  of  unburnt  limestone.  Other  pieces  exposed  to  the  full 
heat  of  the  kiln  are  ' '  over-burnt."  The  "  over-burning  "  of  the  lime  is  either  due  to 
the  forming  of  "  half-burnt  "  lime  (CaC03  +  CaH202)  by  a  strong  and  sudden  ignition  ; 
or  by  means  of  the  high  temperature  the  small  quantity  of  silica  and  alumina  contained 
in  the  limestone  become  sintered  over  the  surface,  and  the  lime  is  thus  prevented  by  a 
coating  of  silicate  from  combining  with  the  water  to  form  a  cream. 

Slacking  Lime. — Burnt  lime  moistened  with  water  slacks  with  great  violence,  100 
parts  by  weight  of  lime  requiring  only  32  parts  water,  or  3  vols.  of  lime  to  i  vol. 
water,  to  obtain  by  the  combination  a  temperature  of  150°.  The  result  of  the  slacking 
is  a  soft,  white  powder,  lime-meal  or  powdered  lime,  hydrated  calcium  oxide  (CaH2Oj), 
which  in  volume  exceeds  three  times  that  of  the  lime  slaked.  If  less  water  is 
added  than  is  requisite  for  the  formation  of  the  hydrate,  a  sandy  powder  is  obtained 
of  little  value  technically.  It  is  therefore  very  disadvantageous  to  place  lime  in 
baskets  in  damp  situations.  For  technical  application  to  building  purposes,  after  the 
lime  has  been  slaked  with  one-third  of  its  weight  of  water,  an  equal  quantity  of  water 
is  added  to  the  mass  to  form  a  thin  cream.  Slaked  lime  retains  its  water  of  forma- 
tion with  such  obstinacy  that  at  a  temperature  of  250°  to  300°  no  loss  of  weight 
occurs.  The  hydrate  forms  a  thin  cream  with  water,  and  from  this  cream  by  further  dilu- 
tion lime-water  or  milk  of  lime  is  obtained.  If  the  lime-water  be  filtered,  there  results 
a  saturated  solution  of  hydrate  of  lime,  containing  i  part  hydrate  to  778  parts  water. 

The  temperature  required  for  burning  lime  has  been  determined  by  Le  Chatelier. 
The  tension  of  dissociation  of  calcium  carbonate  is — 

Temperature.  Pressure,  millimetres. 

547°  ...  27 

625  ...  56 

740  ...  255 

810  ...  678 

812  ...  763 

865  ...  1333 


668  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

Although  the  dissociation  temperature  at  812°  is  equal  to  the  pressure  of  the  atmo- 
sphere, a  heat  of  925°  is  needed  for  the  complete  expulsion  of  the  carbon  dioxide. 

Mortar. — Mortar  is  a  mixture  of  sand  with  cream  of  lime,  used  in  building  as  a 
binding  material.  The  ordinary  mortar  sets  or  hardens  only  in  the  air ;  hydraulic  mortar 
sets  under  water. 

A.  Common  Mortar. — When  slaked  lime  is  exposed  to  the  atmosphere  it  absorbs 
carbonic  acid,  and  the  mass  becomes  much  shrunken  and  cracked.     The  carbonate 
thus  formed,  on  becoming  perfectly  dry,  attains  the  hardness  of  marble.     Such  a 
material,  with  certain  modifications,  is  consequently  admirably  adapted  as  a  cement 
to  bind  together  bricks,  blocks  of  stone,  &c.,  in  building.     But  as  the  contraction  or 
shrinkage  would  give  rise  to  great  unevenness  in  the  construction  of  walls,  it  becomes 
necessary  to  add  sand  or  some  similar  substance  to  the  lime-cream.     This  addition  gives 
a  body  to  the  mortar,  which  combines  with  the  bricks  into  one  coherent  mass.   Common 
mortar  is  ordinarily  made  with  slaked  lime,  an  intimate  mixture  with  sand  and  water 
being  formed.     Angular  or  sharp  sand  is  preferred  to  smooth,  round  sand,  as  making 
a  more  tenacious  mortar.     Round-grained  sand  yields  a  very  brittle  mortar.     The 
proportion  of  sand  to  the  lime  is  a  matter  immediately  affecting  the  quality  and  hard- 
ness of  the  mortar.     In  practice,  i  cubic  metre  of  stiff  lime-cream  requires  3  to  4  cubic 
metres  of  sand ;  but  poor  lime  containing  magnesia  will  only  admit  of  i  to  2\  cubic 
metres  of  sand.     When  mortar  is  employed  in  brick -laying,  the  surface  of  the  brick  is 
moistened,  the  mortar  laid  between  each  brick,  and  left  to  dry.     When  dry  it  is  often 
harder  than  the  brick  itself.* 

Hardening  of  Mortar. — Mortar  sets  or  hardens  very  quickly.  After  a  day  it  will 
attain  a  firmness  that  will  last  for  centuries.  The  drying  out  of  the  water  from  the 
mortar  is  not  the  sole  cause  of  its  hardening,  as  may  be  very  easily  ascertained  by 
drying  the  mortar  in  a  water-bath  or  over  the  spirit-lamp  ;  the  result  is  not  a  stone- 
like,  but  a  friable,  non-coherent  mess.  Fuchs  accounts  for  the  hardening  of  mortar  by 
supposing  the  formation  of  a  basic  calcium  carbonate  (CaC03  +  CaH8O2),  a  combination 
which  has  not  been  known  to  suffer  conversion  into  ordinary  carbonate  of  lime  (CaC08). 
Recent  researches  have  shown  this  supposition  to  be  erroneous,  as  it  does  not  agree 
with  the  results  of  analyses,  which  have  yielded  a  quantity  of  carbonic  acid  incom- 
patible with  the  existence  of  a  neutral  carbonate ;  20  and  even  70  per  cent,  of  carbonic 
acid  have  been  found.  The  experiments  of  Alexander  Petzholdt,  A.  von  Schrotter, 
and  others  have  proved  that  there  is  an  increase  of  soluble  silica.  The  conversion 
of  quartz -sand  into  soluble  silica  under  the  influence  of  hydrate  of  lime  is  not,  how- 
ever, a  reaction  at  all  explanatory  of  the  hardening  of  mortar,  as  washed  chalk  instead 
of  silica  forms  an  equally  hard  mass.  W,  Wolters  gives  the  formation  of  silicate  of 
lime  as  accounting  for  the  hardening  of  mortar.  It  is  not  seldom  in  the  analysis  of 
old  mortar  from  the  interior  of  walls  that  caustic  alkalies  are  found. 

B.  Hydraulic  Mortar. — Limestone  containing  more  than  10  per  cent,  silica  possesses, 
when  burnt  and  made  into  a  mortar,  the  peculiar  property  of  hardening  under  water. 
Lime  burnt  from  such  limestone  is  termed  hydraulic  lime,  and  the  mortar  hydraulic 
mortar. 

When  unburnt,  hydraulic  lime  is  a  mixture  of  calcium  carbonate  with  silica  or  a 
silicate,  generally  aluminium  silicate,  the  latter  being  insoluble  in  hydrochloric  acid. 
During  the  burning,  the  hydraulic  lime  suffers  a  change  similar  to  that  taking  place 
when  a  silicate  insoluble  in  acid  is  precipitated,  during  the  application  of  heat,  with  an 

*  The  durability  of  the  old  Roman  masonry  was  in  a  great  degree  owing  to  the  fact  that  they 
slacked  their  lime  in  small  quantities  as  it  was  needed,  mixed  it  with  clean,  sharp  sand,  and  used 
it  whilst  still  warm.  The  wretched  character  of  the  work  done  by  modern  building  speculators  is 
owing,  on  the  contrary,  to  the  fact  that  they  slack  a  large  quantity  at  once  of  the  worst  lime  pro- 
curable, and  let  it  lie  sometimes  for  weeks  before  use.  Instead  of  sand  they  sometimes  take 
sifted  garden  and  field  soil,  containing  abundance  of  decaying  organic  matter. 


SECT,  v.]  MORTAKS,   ETC.  669 

alkaline  carbonate.  After  burning,  the  lime  is  to  a  great  extent  soluble  in  hydrochloric 
acid,  and  has  lost  some  of  its  carbonic  acid.  Yon  Fuchs,  Feichtinger,  Harms,  Heldt, 
W.  Michaelis,  and  A.  von  Kripp's  experiments  have  proved  that  the  silica  of 
hydraulic  lime  is  precipitated  in  a  gelatinous  condition,  and  that  constituents  such  as 
alumina  and  iron  oxide  are  of  influence  only  when,  under  ignition,  they  have  formed  a 
chemical  combination  with  the  silica. 
Hydraulic  mortars  are  made — 

1.  With  a  thin  cream  of  lime  and  water  to  which  sand  is  added ;  or  with 

2.  A  mixture  of  ordinary  air-mortar  with  water  and  cement. 

During  the  slacking  of  the  hydraulic  lime  water  is  absorbed,  but  without  any  con- 
siderable evolution  of  heat  or  increase  in  volume.  Hydraulic  mortar  is  employed  in  the 
same  manner  as  ordinary  mortar — the  lime-cream  must  be  freshly  made,  and  the  brick 
or  masonry  work  moistened.  The  mortar  should  be  placed  thickly  between  each  layer 
of  bricks,  in  order  to  afford  a  good  firm  bed  and  allow  for  shrinkage. 

Hydraulic  limes  form  a  transition  from  ordinary  lime  to  Roman  cement. 

Roman  cement  is  obtained  by  burning  calcareous  clays  above  a  sintering-heat  and 
grinding  the  product.  The  powder,  which  is  usually  of  a  reddish  brown,  yields  a 
hydraulic  mortar  which  sets  more  rapidly  than  Portland  cement,  but  does  not  attain 
the  same  firmness  if  magnesia  is  present. 

Michaelis  found  by  the  analysis  of  various  Roman  cements — 

I.  2.  3.  4. 

Lime      .  .  58-38  ...  55-50  ...  47-83  ...  58-88 

Magnesia  .  5*00  ...  173  ...  24*26  ...  2-25 

Silicic  acid  .  28-83  •••  25*00  ...  5-80  ...  23-66 

Alumina  .  6-40  ...  6-96  ...  1-50  ...  7-24 

Iron  oxide  .  4-80  ...  9-63  ...  20*80  ...  7-97 

The  analyses  are  from  cements  free  from  water  and  carbonic  acid.  No.  i  is  Roman 
cement  from  Riidersdorf  limestone  ;  2.  From  limestone  from  the  Isle  of  Sheppy,  yellow- 
brown  in  colour,  coarse,  and  hard ;  3.  From  limestone  forming  the  under  bed  of  the 
lead  ores  at  Tarnowitz,  of  a  blue-grey  colour,  firm,  and  of  a  crystalline  appearance ;  4. 
From  Hausbergen  limestone. 

Portland  cement,  the  best  of  all  the  mortars,  is  distinguished  by  the  high  tempera- 
ture, reaching  white  heat,  used  in  its  preparation. 

Portland  cement,  so  named  from  the  resemblance  it  bears  when  set  to  Portland 
stone,  is  a  scaly  crystalline  powder  of  grey  colour,  and  was  first  prepared  by  Mr.  Joseph 
Aspdin,  of  Leeds,  in  1824.  According  to  his  letters  patent,  he  prepared  his  cement 
in  the  following  manner : — A  large  quantity  of  limestone  was  taken  and  pulverised  • 
or  the  dust  or  pulverised  limestone  used  to  mend  the  roads  was  employed.  This 
material  was  dried  and  burnt  in  a  lime-kiln.  An  equal  quantity  by  weight  of  clay 
was  added  to  the  burnt  lime,  and  thoroughly  kneaded  with  water  to  a  plastic  mass. 
This  was  afterwards  dried,  broken  in  pieces,  and  burnt  in  a  lime-kiln  to  remove  all 
the  carbonic  acid.  The  mass,  thus  transformed  to  a  fine  powder,  is  ready  for  the 
market.  It  is  known  in  commerce  as  a  grey,  or  green-grey,  sandy  powder. 
But  Pasley  must  be  considered  the  true  founder  of  artificial  cement  manufacture  in 
England.  He,  in  1826,  obtained  a  cement  by  the  burning  of  river  mud  from  the 
Medway,  impregnated  with  the  salts  from  sea-water,  with  limestone  or  chalk.  The 
mud  from  the  Medway  is  probably  the  best  adapted  for  the  manufacture  of  Portland 
cement,  on  account  of  the  sodium  salts  it  contains ;  and  from  this  supposition  there  seems 
good  ground  for  Pettenkofer's  recommendation  that  various  marls,  burnt  after  lixivia- 
tion  with  a  solution  of  common  salt,  should  be  tried.  At  the  present  time  the  mud  from 
the  mouths  and  delta  formations  of  several  large  rivers  is  employed  in  the  preparation 
of  this  cement. 


670 


CHEMICAL  TECHNOLOGY. 


[SECT.  v. 


The  manufacture  of  Portland  cements  usually  follows  this  mode.  The  raw  mate- 
rials, limestone  and  clay  or  mud  in  equal  quantities,  are  intimately  mixed,  the  mixture 
dried  in  the  air,  and  then  burnt  in  a  shaft-oven.  The  shaft-oven  is  generally  14  to  30 
metres  in  height,  with  a  width  of  2-3  to  4  metres.  At  a  height  of  i  to  1-3  metre 
from  the  ground  is  a  strong  grating,  through  which  the  lumps  of  limestone  mostly 
fall,  those  remaining  being  afterwards  broken  by  the  heat.  The  oven  is  so  arranged 
that  a  layer  of  fuel  and  a  layer  of  cement  stone  alternate.  Coke  is  generally  chosen 
as  fuel,  being  found  by  experience  best  adapted  for  the  purpose.  After  the  mass 
has  been  submitted  to  a  red  heat  for  one  hour,  it  assumes  a  yellow-brown  colour,  and 
at  a  higher  temperature  becomes  a  dark  brown.  Gradually  the  lime  becomes 
causticised,  and  enters  more  and  more  into  chemical  combination  with  the  silicates. 
At  a  white  heat  the  mass  becomes  grey  in  colour,  with  a  streak  here  and  there  of 
green.  If  during  the  operation  these  colours  are  shown  at  the  several  stages,  the 
resulting  cement  will  be  good  and  set  hard.  If  the  heating  is  continued,  the  cement 
will  assume  a  blue-grey  colour,  and  become  quite  useless.  If  removed  at  the  first 
stage  the  mass  yields  a  yellow-brown  light  powder ;  at  the  second,  a  grey  sharp 
powder,  tinged  with  green.  Beyond  this  stage  the  powder  is  blue-grey,  or  grey- white, 
clear  and  sharp,  and  very  similar  to  glass-powder.  The  more  lime  the  mixture  con- 
tains, or,  it  might  be  said,  the  more  basic  the  mixture,  the  more  durable  is  the  cement, 
and  the  less  it  falls  to  pieces  in  burning.  A  mixture  in  which  clay  predominates  is 
always  more  or  less  a  weaker  cement,  falling  to  pieces  readily,  or,  technically,  not 
binding  well.  According  to  Michaelis,  the  addition  of  lime  or  alkalies  prevents  the 
cement  separating,  and  renders  it  more  binding  ;  but  in  practice  this  addition  would 
not  be  sufficiently  economical.  The  more  intimately  the  clay  and  lime  are  mixed, 
the  larger  the  amount  of  lime  that  may  be  incorporated.  From  the  moment  of 
stiffening  till  the  final  hardening,  the  cement,  if  set  in  the  air,  experiences  no 

change ;  but  if  in  water,  there  is  at  first  a  small  loss 
of  the  more  soluble  constituents — the  alkalies. 

Portland  cement  mixed  with  water  to  a  paste 
stiffens  in  a  few  minutes,  and  after  the  lapse  of  a 
day  sets  tolerably  hard.  After  a  month  the  cement 
sets  into  a  substance  so  hard  and  firm  that  it  emits 
a  sound  when  struck  by  a  hard  body.  It  is  ad- 
mirably adapted,  when  mixed  with  sand  or  gypsutn, 
for  being  cast  into  various  architectural  ornaments, 
and,  indeed,  has  from  this  property  been  termed 
artificial  stone.  Lately  Griineberg  has  made  crys- 
tallising vessels  of  this  cement,  and  Posch  employs 
it  in  constructing  reservoirs  for  hot  fluids. 

Portland  cement  is  considered  by  military  en- 
gineers the  best  material  to  oppose  to  the  projectiles 
used  in  modern  warfare. 

It  has  been  very  successfully  burnt  in  the  stage- 
furnace  of  Dietzsch  (Fig.  463).  The  raw  materials, 
artificially  dried,  are  introduced  through  a  hopper, 
E,  into  the  preliminary  warming-chamber,  A.  It 
slips  down  over  the  arched  connecting-shoot,  B,  and 
is  shovelled  from  the  working-door,  F,  into  the 
melting-space,  C.  Any  clinkers  which  have  become  welded  to  the  sides  of  the  furnace 
are  removed  through  the  opening,  G,  so  that  they  fall  into  the  cooling-room,  D.  100 
parts  of  cement  require  in  this  furnace  only  9  to  19  parts  of  coal,  as  against  6-23  parts 
in  a  ring-furnace,  and  20  to  28  parts  in  a  shaft-furnace. 


Fig-  463- 


SECT.    V.] 


MORTARS,  ETC. 


671 


These  varying  statements  may  be  in  part  explained  by  the  difference  in  the  fuel 
and  by  the  more  or  less  careful  superintendence  of  the  work.  If,  e.g.,  Meyer  found 
in  the  combustion -gases  of  a  ring-furnace  only  3-2  to  7-6  per  cent,  carbon  dioxide,  as 
against  2  to  11-9  per  cent,  in  the  gases  of  the  stage-furnace  (where  we  have  also  to 
take  into  account  that  a  considerable  part  is  derived  from  the  decomposition  of  the 
lime  in  the  raw  material),  this  proves  that  there  is  a  great  waste  of  fuel.  If  only  half  as 
much  carbonic  acid  were  introduced,  we  should  have  a  much  greater  heat,  more  rapid 
burning,  and  less  loss  of  heat  at  the  chimney.  These  differences  seem  in  part  to  be  ex- 
plained by  the  different  nature  of  the  mass  itself.  At  least  Dietzsch  observed  that  in 
his  furnace  two  masses  used  15-9  to  19  kilos,  of  coal  and  a  third  only  9.  As  the 
chemical  processes  in  burning  (decomposition  of  OaCOs  into  CaO  +  C02,  formation  of 
silicates  and  aluminates)  do  not  explain  so  great  a  difference,  the  reason  probably  is 
that  one  mass  requires  a  higher  temperature  than  the  other,  and  that  for  its  produc- 
tion— especially  if  the  supply  of  air  is  unsuitable — a  disproportionate  quantity  of  coal 
is  needed. 

M.  W.  Michaelis  gives  the  following  analyses  of  Portland  cements,  the  samples 
being  free  from  water  and  carbonic  acid  : — 


g 

g 

9- 

Lime    . 
Silicic  acid 
Alumina 
Iron  oxide 
Magnesia 
Potash  

59-06 
24-07 
6-92 

3-4I 
0-82 
O'73  1 

62-81 
23-22 
5-27 

2'OO 
I-I4 

6I-9I 
24-I9 
7'66 
2'54 
I-I5 
fo'77 

60-33 
25-98 
7-04 
2-46 
0-23 
O'Q4. 

61-64 
23-00 
6-17 
2-13 

6174 
25-63 
6-17 

o-45 
2-24 
0*60 

55^ 
22^2 

8-00 
5-46 
077 

T'TS 

57-83 
23-81 

9-38 
S-22 

i-35 

O'CQ 

55-28 
22-86 

9-03 

6-14 
1-64 

0*77 

0-871 

1-27 

1  n'/ift 

O"3O 

0*40 

I  '7O 

O*7T 

Calcium  sulphate          . 
Clay  I 

2-85 
I  "4.7 

I-30 
2't.A 

I  "32 

I'52 

I  "O4 

i'53 

1-28 

1-64 

T'I2 

i-75 

2  '27 

I'll 

3-20 
i'o8 

Sand]    ' 

No.  i  is  Portland  cement  from  White  &  Brothers,  analysed  by  Michaelis.  No.  2 
is  Stettin  cement,  analysed  by  Michaelis.  Nos.  3  and  4  are  Wildauer  cements.  No. 
5,  known  as  Star  cement,  and  No.  6,  another  Stettin  cement,  by  the  same  analyst. 
No.  7,  English  cement,  and  No.  8,  cement  from  works  near  Bonn,  were  both  analysed 
by  Hopfgartner.  No.  9  is  a  strong  and  porous  cement,  analysed  by  Feichtinger. 

Boehme  gives  the  analysis  of  ten  samples,  which  are  of  little  value,  as  they  do  not 
give  the  locality  or  the  name  of  the  maker. 

Hardening  of  Hydraulic  Mortars. — The  hardening  of  hydraulic  mortars  has  often 
been  the  subject  of  investigation.  Two  views  may  be  taken :  first,  the  mere  setting, 
the  congealing  of  the  mass  from  a  fluid  state  to  a  moderate  degree  of  hardness ;  and 
then  the  hardening  to  a  stony  state.  The  knowledge  we  possess  of  the  setting  of  these 
mortars  is  chiefly  due  to  the  experiments  of  Yon  Fuchs,  Von  Pettenkofer,  Winkler, 
Feichtinger,  Heldt,  Lieven,  Schulat-Schenko,  Ad.  Remete,  Heereen,  W.  Michaelis,  and 
Von  Schoenaich-Carolath.  The  cements  when  thus  considered  are  best  divided  in  two 
classes  : — The  first  class,  of  which  Roman  cement  is  the  type,  embraces  the  mixture  of 
caustic  lime  with  puzzuolane,  pulverised  tile,  and  brick,  and  such  hydraulic  mortar  as 
is  obtained  by  burning  hydraulic  lime  and  marl.  All  the  cements  contain  caustic  lime 
unacted  upon.  The  second  class  comprehends  Portland  cements,  containing  no  fresh 
caustic  lime.  M.  Von  Fuchs  has  explained  the  chemical  actions  taking  place  during 
the  hardening  of  Roman  cements  as  being  principally  the  combination  of  the  lime  with 
silicic  acid,  the  combination  giving  rise  to  the  peculiar  property  of  hydraulic  mortars. 
He  draws  this  conclusion  partly  from  the  fact  that  from  all  hydraulic  mortars  the 
silica  can  be  thrown  down  as  an  insoluble  gelatinous  mass  by  the  action  of 
carbonic  acid. 

A  similar  gelatinous  mass  results  from  the  combination  of  silicic  acid  and  lime. 


672  CHEMICAL  TECHNOLOGY.  [SECT.  v. 

Silicates  do  not  yield  gelatinous  silica  when  treated  with  hydrochloric  acid  alone,  but 
attain  this  property  when  subjected  for  a  length  of  time  to  the  influence  of  lime  under 
water  ;  the  water  also  dissolves  out  the  alkalies.  Kuhlmann,  who  has  long  been  employed 
in  the  study  of  the  chemistry  of  hydraulic  cements  and  artificial  stones,  states  that 
lime  can  be  rendered  hydraulic  by  the  intimate  mixture  of  10  to  12  per  cent,  of  an 
alkaline  silicate,  or  by  treatment  with  a  water-glass  solution.  Collecting  the  results  of 
these  experiments,  the  setting  of  Roman  cements  appears  due  to  the  combination  of 
acid  silicates  or  silica  with  burnt  lime,  forming  a  hydrated  calcium  silicate  intermixed 
with  the  alumina  and  iron  oxide. 

The  hardening  of  Portland  cements  has  been  investigated  by  Winkler  and  Feich- 
tinger.  According  to  the  former,  the  chemical  action,  which  is  effected  under  the  co- 
operation of  the  water,  consists  in  the  separation  of  the  silicates  into  free  lime  and 
combinations  between  the  silica  and  the  calcium,  the  alumina  and  the  calcium.  The 
separated  lime  combines  with  the  carbonic  acid  in  the  air  to  form  calcium  carbonate. 
The  hardened  Portland  cement  contains  the  same  combinations  as  hardened  Roman 
cement ;  these  combinations  are  formed,  however,  under  the  influence  of  water  on  opposed 
conditions.  From  the  results  of  Winkler's  experiments,  it  would  appear  that  the  silicic 
acid  in  the  Portland  cements  can  be  replaced  by  alumina  and  iron  oxide.  Alumina 
does  not  affect  the  hardness,  but  may  lessen  the  capability  of  the  cement  to  withstand 
the  action  of  carbonic  acid.  During  the  hardening  the  influence  of  the  water  separates 
the  lime,  till  finally  the  combinations  Ca3Si309  and  CaAl2O4  remain,  the  latter  being 
gradually  decomposed  by  carbonic  acid,  remaining,  however,  as  long  as  there  is  any 
hydrate  of  lime  in  the  cement.  G.  Feichtinger  maintains  a  theory  differing  from  that 
of  Winkler.  His  experiments  lead  him  to  the  opinion  that  in  all  hydraulic  mortars 
the  hardening  depends  upon  the  chemical  combination  between  lime  and  the  silica,  and 
between  lime  and  the  silicates  contained  in  the  cement.  In  all  hydraulic  cements  free 
lime  is  contained ;  and  upon  this  fact  we  may  base  the  following  experiments.  When 
Portland  cement  is  brought  to  a  paste  with  a  concentrated  solution  of  ammonium 
carbonate,  and  stirred  for  a  long  time,  no  hardening  is  traced,  the  greater  part  of  the  lime 
forming  calcium  carbonate.  Then  let  the  excess  of  ammonium  carbonate  be  washed 
away,  the  cement  dried,  and  made  into  a  mortar  with  pure  water.  This  mortar  will 
not  harden  unless  some  calcium  hydroxide  be  added,  when  it  hardens  similarly  to  fresh 
mortar.  The  same  result  may  be  obtained  by  substituting  a  stream  of  carbonic  acid 
gas  for  the  ammonium  carbonate ;  by  this  means  27  per  cent,  of  calcium  carbonate  may 
be  obtained.  Consequently  the  views  of  Winkler  must  be  regarded  as  the  most  correct. 
These  experiments  also  show  that  in  Portland  cements  silicates  or  free  silica  are  con- 
tained; that,  further,  free  lime  does  and  must  exist.  Portland  cement  will  not  take  a 
glaze,  and  can  only  be  so  far  affected  by  burning  as  to  cause  the  sintering  of  the  clay 
contained  in  the  cement. 

Erdmenger  ascribes  the  setting  of  cement  chiefly  to  the  formation  of  a  crystalline 
lime  hydrate.  This  hypothesis  agrees  ill  with  the  experiments  of  Ostwald,  who  found 
the  composition  of  three  cements  from  Riga  (I.  to  III.)  and  two  from  Stettin  (IV.  and 
V.)  to  be  as  follows  : — 

I.  ii.  in.  iv.  v. 

CaO  .  .  .  72-10  ...  65-42  ...  61-92  ...  65-05  ...  60-52 

MgO  .  .  .          3-27  ...  3-89  ...  4-03  ...  3-04  ...  3-02 

A120S  .  .          6-66  ...  7-52  ...  7-97  ...  8-09  ...  7-57 

FeA  .  .          1-99  ...  2-15  ...  2-71  ...  3-25  ...  4-48 

Si°2   •  •  •  10-38  '••  1476  ...  16-75  —  1 7'°4  •••  20'72 

Alkalies  .  .          0*85  ...  o-86  ...  1-25  ...  0-92  ...  ro2 

SO,    .  .  .          0-42  ...  0-52  ...  0-42  ...  0-30  ...  0-37 

CO,    .  .  .          1-64  ...  2-19  ...  2-42  ...  0-83  ...  0-52 

C                                  0-36  ...  0-50  ...  0-47  ...  0-67  ...  0-53 

H«O    .  .  .          2-56  ...  2-32  ...  2-24  ...  ro6  ...  1-22 


SECT,  v.]  MORTARS,  ETC.  673.. 

In  connection  with  these  analyses,  Ostwald  determined  the  heat  of  setting : 

Time.                                   I.                         II.                        III.  IV.                         V. 

2  hours  .        .        20-53°  ...  20-47°  •••  9'94°  --•  34'Oi°  ...         7-53° 

6     „                           37'05  -.  29-57  ...  12-23  •••  35'46  ...  10-09 

I  day  ..        .        41-35  ...  3978  ...  15-32  ...  38-39  ...  18-79 

4  days  .        .        46-16  ...         —  ...  29-72  ...  ...         

5  ,,  •  47'*7       -          —        ...       32-10       ... 

6  „  •  57'96      —      44'34      —      33'56      —         —        ...         — 

7  „  •  65-63      ...       51-55       ...      40-26      ... 

Thus  the  development  of  heat  was  at  first  very  rapid  ;  after  six  hours  more  than 
half  the  total  heat  has  been  liberated.  Afterwards  the  liberation  of  heat  becomes 
slower  and  slower,  and  after  thirty  days  it  is  as  good  as  imperceptible.  We  must  note 
the  striking  increase  of  the  liberation  of  heat  on  the  fifth,  sixth,  and  seventh  day.  At 
this  time  there  evidently  begins  a  new  epoch  in  the  chemical  process  of  hardening,  which 
involves  a  renewed  development  of  heat.  The  more  quickly  a  cement  sets,  the  greater 
is  its  "  setting-heat."  According  to  Berthelot  i  gramme  lime  in  slacking  evolves  268 
heat-units.  If  we  calculate  from  the  analyses  how  much  free  lime  is  contained  in  the 
cements,  the  existing  carbonic  acid  being  assumed  as  combining  first  with  the  alkalies 
and  then  with  the  lime,  and  the  water  being  supposed  to  combine  with  the  lime  to  a 
hydrate,  we  may  determine  what  quantity  of  heat  would  be  developed  by  the  action  of 
the  water  if  the  lime  were  free  and  became  hydrated.  The  calculation  is  carried  out 
in  the  following  table : — 

I.  II.  III.  IV.  V. 

Hydration  heat  of  lime     .      i68-8     ...     150*0    ...     136-6     ...     162-4     •••     *55'4 
Setting  heat  of  cement     .        70-2     ...      66'2     ...      45-4     ...       52-8     ...      42-3 

The  specimens  IV.  and  V.  have  not  been  examined  to  the  end,  but  they  have  plainly 
already  given  off  the  chief  portion  of  their  combining  heat,  which  is  in  all  cases  much 
smaller  than  the  hydration  heat  of  the  lime  regarded  as  uncombined.  Hence,  the 
assumption  that  no  chemical  interaction  takes  place  between  the  lime  and  the  clay 
during  the  formation  of  Portland  cement  is  not  tenable.  On  the  contrary,  there  occurs 
a  very  important  reaction,  during  which  a  quantity  of  heat  is  set  free.  The  so-called 
physical  theory  of  the  formation  of  cement  must  be  considered  as  refuted,  and  the 
chemical  theory  alone  must  be  accepted  as  in  harmony  with  facts.  The  objection  might 
of  course  be  raised  that  chemical  processes  take  place  during  the  setting,  to  which 
the  difference  observed  might  be  ascribed.  But  such  processes,  like  the  formation  of 
zeolitic  silicates,  aluminium  hydrates,  &c.,  all  evolve  heat  and  therefore  tend  to  lessen 
the  difference.  That  such  difference  is  still  so  great  proves  the  importance  of  the 
chemical  processes  during  burning. 

Le  Ohatelier  ascribes  the  most  important  part  in  the  setting  of  hydraulic  mortars 
to  the  crystallisation  of  dissolved  matters  of  the  combination  CaO.Si02.3H2O  (the 
composition  of  which  is  deduced,  not  from  analyses,  but  from  the  crystalline  compound, 
BaO.Si02.6H2O),  which  is  resolved  by  water  into  free  lime  and  an  acid  silicate,  2Si02.CaO, 
and  by  carbon  dioxide  and  water  into  silica  and  a  calcium  carbonate.  But  the  former 
decomposition  ceases  when  the  water  contains  0*052  gramme  lime  per  litre.  The 
formation  of  this  silicate  during  the  setting  ensues  either  by  the  union  of  the  two  con- 
stituents or  by  the  decomposition  of  silicates  richer  in  lime,  or  perhaps  by  the  mere 
hydration  of  the  anhydrous  compound.  The  above-named  combinations  of  lime  with 
ferric  oxide  or  alumina,  which  can  exist  in  water  in  presence  of  an  excess  of  lime,  are 
decomposed  by  an  excess  of  water  ;  but  the  decomposition  ceases  with  a  proportion  of 
lime  of  0-225  gramme  or  of  o-6  gramme  per  litre  at  15°.  Ferric  oxide  and  alumina 
are  essential  in  burning,  for  the  better  combination  of  the  lime  with  the  silica. 

Further  experiments  are  necessary  for  the  full  elucidation  of  the  question. 

Testing  Cement. — In  examining  cements  it  is  necessary  to  have  in  view  the  mixture 

2    U 


674  CHEMICAL   TECHNOLOGY.  [SECT.  v. 

of  cement  with  ground  slags,  now  unfortunately  in  extensive  practice.  According 
to  Fresenius.  a  genuine  cement  should  show  (a)  a  specific  gravity  of  at  least  3*125, 
certainly  not  less  than  3'!  ;  (b)  a  loss  on  ignition  of  between  0-34  and  2*59  per  cent.,  cer- 
tainly not  higher;  (c)an  alkalinity  in  the  watery  solution  of  o'5  gramme,  corresponding 
to  4 — 6-35  c.c.  of  decinormal  acid  ;  (d)  a  consumption  of  normal  acid  on  the  direct  treat- 
ment of  i  gramme  ground  cement  between  i8'8o  and  21-67  c.c.,  certainly  not  much 
lower;  (e)  a  consumption  of  permanganate  solution  by  i  gramme  cement  equal  to 
between  079  and  2*80  milligrammes  potassium  permanganate,  not  more. 

Hydraulic  Admixtures. — Trass  or  tarass  is  a  kind  of  trachytic  tufa  found  in  con- 
siderable quantities  in  the  Brohl-  and  Nettethall,  near  Andernach.*  It  contains 
magnetic  iron  in  small  quantities,  and  also  titanic  iron. 

Soluble  in  Insoluble  in 

Hydrochloric  Acid.  Hydrochloric  Acid. 

Silica       .        .        .        .  11-50  37'44 

Lime        ....  3-16  ...  2-25 

Magnesia         .         .        .  2*15  ...  0*27 

Potash     .        .        .  0-29  ...  0-08 

Soda        .        .        ,        .  •       2-44  ...  ri2 

Alumina.       -.        .        .  1770  ...  1^25 

Iron  oxide        .        .        .  ii'ij  ...  075 

Water      ....  7-65 


56-86  ... 

This  cement  has  been  employed  for  300  years  as  a  hydraulic  mortar,  and  is  one  of 
the  most  important  of  its  class. 

Puzzolana  is  another  tertiary  earth,  occurring  chiefly  at  Puzzuoli,  near  Naples,  as 
a  loose,  grey,  or  yellow-brown  mass,  of  partly  a  fine-grained  and  partly  an  earthy 
iracture.  It  contains  in  100  parts: — 

Silicic  acid 44 '5 

Alumina iS'o 

Lime 848 

Magnesia 47 

Iron  oxide 12  x> 

Potash ) 

Soda ) 

Water 9-2 

997 

The  oxide  of  iron  contains  small  quantities  of  titanium.  More  lime  must  be 
added  to  form  a  hydraulic  mortar.  The  masonry  of  the  light-room  of  the  Eddystone 
Lighthouse  is  cemented  with  a  hydraulic  mortar  formed  from  equal  parts  of  pulverised 
puzzolana  and  slaked  lime. 

Santorin  derives  its  name  from  the  Greek  island  of  Santorin,  where  it  was  first 
found.  It  is,  similarly  to  trass,  a  volcanic  formation,  and,  according  to  G.  Feichtinger 
(1870),  consists  of  a  mixture  of  cement  and  sand,  the  latter  containing  large  quantities 
of  pumice-stone.  It  is  not  largely  employed  as  a  cement,  on  account  of  the  difficulty 
of  separating  the  true  cement  from  the  accompanying  sand. 

Puzzolane  Cements. — Under  this  name,  or  that  of  Victoria  "  cement,"  there  are 
sold  mixtures  of  finely  ground  slag  and  of  lime  slacked  to  a  powder.  This  mixture,  if 
kept  sufficiently  moist,  sets  slowly  and  becomes  moderately  hard.  Frost  has  a  destructive 
action  upon  recent  slag  cement  structures,  so  that  they  are  not  admissible  below  o°.  For 
the  first  fortnight  such  structures  should  be  kept  uniformly  moist.  It  is  better  suited 
for  constructions  under  water.  A  further  bad  property  of  slag  cements  is  their 
tendency  to  crack,  which  can  be  combated  only  by  grinding  the  slags  less  finely.  A 
*  It  is  also  found  at  Ardwick,  near  Manchester. — ^EDITOR.] 


SECT,  v.]  MORTARS,  ETC.  675 

pure  slag  cement  cannot  oppose  any  satisfactory  resistance  to  external  mechanical 
action.  In  all  probability  it  will  not  acquire  importance  for  constructions  in  the  air 
which  are  exposed  to  wear  and  tear.  Its  low  initial  hardness — which  it  shares  with 
all  puzzolanes,  natural  or  artificial — is  another  defect. 

Concrete. — The  mention  of  concrete,  so  largely  used  in  England,  where  a  good 
weathering  mortar  is  required,  must  be  included  in  that  of  cements.  Concrete  is  a 
mixture  of  ordinary  mortar  with  stones,  grit,  broken  brick,  tiles,  &c.  To  the  concrete 
is  generally  added  lime,  and  then  the  whole  mixed  with  two  or  three  times  the 
quantity  of  fine  sand.  Pasely  tells  us  that  a  better  product  may  be  obtained  with  i 
part  of  freshly  burnt  lime,  in  pieces  not  larger  than  the  fist,  3^  parts  of  sharp  river- 
sand,  and  i -5  part  of  water,  the  whole  being  well  mixed.  The  bricklayer  prefers  to 
mix  the  dry  materials  and  then  add  water,  the  concrete  in  this  manner  taking  a  longer 
time  to  harden,  and  admitting  of  greater  care  being  taken  to  fill  all  interstices.  The 
several  uses  of  concrete  are  too  well  known  to  need  mention.  The  employment  of  un- 
slaked lime  in  the  preparation  of  concrete  was  first  introduced  by  Mr.  Smirke,  of 
London,  to  whom  also  its  employment  as  a  foundation  to  brickwork  is  mainly  due. 

Mixed  Cements. — We  have  already  mentioned  that  for  some  years  a  number  of 
manufacturers  and  dealers  have  begun  adding  ground  slags  to  the  finished  cement, 
under  pretence  of  improving  it.  A  good  Portland  cement  cannot  be  improved  by  such 
additions.  The  admixture  of  slag  with  Portland  cement,  like  that  of  heavy  spar  and 
gypsum  to  painters'  colours,  is  therefore  a  fraud  on  the  purchaser,  and  consequently  to 
be  condemned. 


SECTION  VI. 
ARTICLES    OF    FOOD    AND    CONSUMPTION. 


STARCH  AND  DEXTRINE. 

THE  starch  granule  is  an  organised  tissue,  consisting  essentially  of  starch  with  water, 
a  little  sugar,  dextrine,  &c.  Its  composition  corresponds  to  the  formula  C6H10O5,  or, 
according  to  Mylius,  C24H40020,  or  according  to  Nageli,  C36H62031.  According  to  Dafert, 
starch  consists  of  bodies  which  are  not  mutually  homogeneous  (starch-cellulose,  granu- 
lose,  dextrine),  a  little  sugar,  proteine  compounds,  amides,  fat,  and  ash.  He  therefore 
considers  it  idle  to  discuss  the  formula  of  starch,  since  it  is  a  mere  mixture. 

The  starch  granule  consists  of  numerous  layers,  which  generally  contain  the 
more  water  the  further  we  proceed  inwards.  The  innermost  part  is  generally  a 
hollow,  filled  with  air,  around  which  the  layers  seem  to  be  arranged.  As  a  rule,  the 
thickest  parts  of  all  the  layers  are  turned  in  the  same  direction.  If  they  are  equally 
thick  in  all  directions,  the  granules  are  globular ;  if  they  are  thicker  in  the  equatorial 
zone,  the  granule  has  a  lenticular  shape.  On  microscopic  examination  the  limits  of  the 
layers  appear  as  lines,  more  or  less  distinct,  running  round  the  central  cavity.  Its 
specific  gravity  =  i'53-  Iodine  water  colours  starch  blue,  and  the  starch  iodide  formed 
has,  according  to  Bondonneau,  the  formula  (C6H10O5)3I,  or  according  to  Mylius, 

(c24H40o20i)4m. 

Payen  gives  the  largest  dimension  of  the  granules  as  o'ooi  millimetre;  from  his 
researches  we  gain  also  the  following  examples  : — 


Starch  granules  from  hard  potatoes 

ordinary  potatoes 
Maranta  indica 
beans    . 
sago  palm 
Iceland  moss 
peas 

wheat    .        . 
Indian  corn    . 


185 
140 
140 

74 
70 
67 
5° 
So 
So 


Fig.  464  shows,  according  to  Schleiden,  granules  of  potato  starch,  and  Fig.  465  of 
wheat  starch.  The  potato  has  a  larger  granule,  and  sometimes  gives  a  finer  powder 
than  wheat. 

Nature  of  Starch. — Ordinary  starch  contains  in  its  dry  state  nearly  18  per  cent, 
water,  and  in  this  state  has  a  tendency  to  form  itself  into  globules  ;  it  has  been  proved 
that,  exposed  to  a  damp  atmosphere,  it  absorbs  33*5  per  cent,  water.  Starch  is  insoluble 
in  cold  water,  alcohol,  ether,  and  oil.  At  a  temperature  of  160°  starch  yields  dextrine. 
Starch  mixed  with  twelve  to  fifteen  times  its  quantity  of  warm  water  at  a  temperature 
of  55°  varies  little  in  substance  ;  at  a  temperature  of  55°  to  58°  it  begins  to  change,  the 
higher  temperature  making  the  fluid  thicker.  Lippmann  says  that  potato  starch  is 
affected  at  62*5°,  wheat  starch  at  67-5°.  When  boiled  the  granules  burst  and  form 


SECT.    VI.] 


STARCH   AND   DEXTRINE. 


677 


.a  gelatinous  mass,  which,  largely  diluted  with  water,  can  be  made  of  a  consistence  to  be 
filtered  through  paper,  and,  when  allowed  to  cool,  sets  in  a  jelly.  A  stiffer  paste, 
according  to  J.  Wiesner  (1868),  is  made  from  Indian  corn  than  from  the  potato  or 


Fig.  464. 


Fig.  465. 


•wheat.  The  longer  the  starch  is  boiled  the  stiffer  the  paste  becomes,  i  part  of  starch 
separating  in  50  parts  water,  and,  upon  cooling,  setting  into  paste  of  a  blue  or  violet 
hue. 

Alkalies  and  dilute  acids,  with  lime,  tend  to  re-form  the  granules ;  when  boiled 
with  2  per  mille  of  oxalic  acid,  starch  loses  its  consistence,  becoming  thin,  and 
changing  into  a  soluble  substance  called  dextrine.  Starch  treated  with  almost 
any  dilute  acid,  or  with  diastase  obtained  from  an  infusion  of  malt,  at  the  proper 
temperature  is  converted  into  dextrine,  forming  a  liquid  which  after  a  few  hours; 
standing  can  be  made  into  sugar.  Starch  is  soluble  in  the  cold  in  concentrated 
nitric  acid  ;  water  dropped  into  this  solution  precipitates  the  granules  as  an  explosive 
combination.  Under  the  name  of  xylodine,  or  white  gunpowder,  this  combination  has 
lately  been  employed  for  pyrotechnical  experiments.  By  boiling  starch  with  con- 
centrated nitric  acid,  a  formation  of  oxalic  acid  is  obtained,  evolving  nitrous 
vapours.  Starch  paste,  upon  exposure  to  the  atmosphere,  becomes  sour,  forming 
lactic  acid. 

In  the  determination  of  starch  in  raw  materials,  it  must  be  considered  that  for  the 
textile  arts  and  for  domestic  uses  only  the  actual  starch  must  be  considered,  and 
sugar,  if  present,  must  be  estimated  separately.  For  brewery  purposes  the  sugar  is 
determined  along  with  the  starch.  For  the  spirit  manufacture  it  must  be  remembered 
that  the  sugar  present  is  destroyed  by  the  high  pressure,  whilst  other  substances  are 
converted  into  carbohydrates  capable  of  fermentation. 

For  the  two  former  purposes,  according  to  Reinke,  3  grammes  of  the  sample, 
ground  as  finely  as  possible,  are  heated  to  boiling  with  50  c.c.  of  water,  cooled  down  to 
62*5°,  and  mixed  with  0^05  gramme  of  diastase  prepared  according  to  Lintner.  Saccha- 
rification  is  allowed  to  proceed  for  an  hour  at  the  same  temperature.  The  mixture 
is  then  diluted  with  water,  cooled,  and  made  up  to  250  c.c.  200  c.c.  are  then  inverted 
with  15  c.c.  hydrochloric  acid  (of  sp.  gr.  i'i25)  at  a  boiling  heat  for  two  and  a  half 
hours  in  an  Erlenmeyer  flask  with  a  reflux  condenser,  almost  entirely  neutralised 
with  soda-lye,  made  up  to  500  c.c.,  and  25  c.c.  are  taken  for  reduction  with  Fehling's 
solution.  The  dextrose  is  calculated  from  the  reduced  copper  according  to  Allihn's 
tables,  i  oo  dextrose  =  90  starch. 

For  distillery  purposes  3  grammes  of  the  finely  ground  sample  are  stirred  up  with 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


25  c.c.  of  lactic  acid  at  i  per  cent,  and  30  c.c.  of  water  heated  for  two  and  a  half  hours  in 
Soxhlet's  autoclave  at  a  pressure  of  3^  atmospheres,  then  mixed  with  50  c.c.  hot  water, 
when  cold  made  up  to  250  c.c.,  and  filtered  ;  200  c.c.  of  the  nitrate  are  inverted  as  above 
and  used  for  the  determination  of  dextrose. 

Sources  of  Starch. — But  few  vegetables  yield  starch  in  large  quantities  ;  the  potato 
yields  20  per  cent. ;  wheat,  55  to  65  per  cent. ;  rice,  70  to  73  per  cent. ;  and  the  roots  of 
Jatropha  Manihot  and  Maranta  arundinacea,  palm  pith,  and  the  Canna  coccinea,  similar 
quantities.  In  Germany  starch  is  prepared  only  from  potatoes,  rice,  and  wheat,  the 
latter  yielding  a  greater  quantity  of  gum,  and  potato  starch  being  thinner  and  not  so 
gelatinous. 

Starch  from  Potatoes. — Potatoes  form  an  important  material  in  the  manufacture 
of  starch ;  their  constitution  is  as  follows  : — 


Water  . 
Albumen 
Fatty  matter 
Cellulose 
Salts  . 
Starch  . 


Newly  dug 
Potatoes. 


2-3 

0'2 

0'4 

I'O 

21  'O 


Potatoes 
dried  at  100° 


9-6 
0-8 
17 
4'i 
83-8 


They  contain  28  per  cent,  dry  substance,  or  23  per  cent,  insoluble  substance,  and 
7  7  per  cent.  sap.  The  starch  found  in  potatoes  is  of  cellular  construction ;  the  cell 
walls  require  breaking  up  to  fit  it  for  manufacture.  Fig.  466  shows,  according  to 
Schleiden,  a  fine  specimen  of  a  healthy  potato  under  the  microscope.  On  the  outside  of 
the  potato  a  layer  of  flat,  pressed,  brown  cells  are  found,  sometimes  appearing  in  a 
patch,  a,  forming  the  outer  skin  of  the  potato,  and  covering  the  cells,  b,  which  some- 


Fig.  467. 


times  contain  a  finer  grain,  but  mostly  a  clear  fluid.  These  cells  become  wider  as 
they  near  the  interior  of  the  potato.  The  series  of  cells  c  enclose  the  inner  cells,  d, 
the  pith  of  the  potato.  When  the  potato  is  dried,  the  cells  separate  from  each  other, 
as  in  Fig.  467,  a  specimen  of  a  mealy  potato.  The  starch  granules  swell  in  each 
cell,  the  cells  uniting  in  reticulated  streaks. 

The  process  of  manufacturing  starch  consists  in — 

i .  Triturating  the  fresh  potato. 

2    Washing  the  starch  granules  from  the  pulp. 

3.  Purifying  and  drying  the  starch. 


SECT,  vi.]  STARCH  AND  DEXTRINE.  679- 

The  potatoes  are  placed  in  a  grinding  cylinder,  which  formerly  consisted  of  wood, 
with  iron  plate  rollers  placed  half-way  in  water  to  cleanse  the  pulverised  potato  pulp. 
Of  late  grinding  cylinders  with  saw-teeth  are  used  (Thierry's  machine).  The  saw- 
blades  have  short  teeth,  lacerating  the  cells  to  obtain  the  starch  granules,  which  mere 
gentle  washing  and  grinding  would  not  effect ;  the  cylinder  revolves  600  to  700  times 
a  minute.  One  cylinder,  with  knives  0*50  metre  in  length  and  saw-blades  of  0*40  metre, 
can  grind  fourteen  to  fifteen  batches  in  an  hour  to  a  pulp,  which  is  afterwards  sub- 
mitted to  the  process  of  washing.  A  cylindrical  metal  sieve  is  generally  used  for 
separating  the  starch  granules  from  the  potato  pulp ;  it  contains  a  pair  of  brushes 
slowly  rotating,  whilst  water  is  supplied  to  the  sieve  to  wash  the  pulp,  which  is  ground 
to  a  consistence  that  will  admit  of  its  readily  flowing  off,  in  order  that  fresh  pulp  may 
be  received  on  the  sieve.  The  starch  granules  are  suspended  in  the  water  strained  off, 
and  finally  settle  to  the  bottom  as  a  soft  white  powder.  Laine's  uninterrupted  cleans- 
ing sieve  is  now  generally  used ;  it  consists  of  a  series  of  wire-work  frames  placed  over 
a  trough.  The  potato  pulp  flows  from  the  grinding  cylinder  to  a  space  under  the 
cleansing  sieve,  from  thence  over  two  gratings,  where  the  pulp  is  cleansed  by  a  stream 
of  water  playing  all  over  it,  the  granules  settling  down  at  the  bottom  of  the  trough. 
The  granules  are  then  crushed  between  steel  rollers  to  separate  the  starch  from  the 
fibre.  80  to  100  cwts.  potatoes  can  be  thus  prepared  in  a  day.  From  the  above 
method  of  preparing  starch  from  the  potato  we  gain  the  general  principles  of  such 
operations.  The  structure  of  the  potato  is  shown  to  be  partly  chemical,  partly 
mechanical,  and  by  destroying  the  latter  we  gain  starch,  which  is  separated  after  the 
potato  pulp  has  been  standing  eight  days,  when  it  becomes  a  white  pasty  mass  contain- 
ing starch.  This  is  placed  in  a  coarse  sieve,  which  retains  a  greater  part  of  the*  fibre, 
another  finer  hair  sieve  being  used  to  receive  the  starch  and  finer  fibre,  separated  from 
each  other  by  means  of  a  cleansing  apparatus,  which  washes  the  fibre  away,  leaving  the 
starch  granules  and  sugar  behind. 

Drying  the  Potato  Starch. — The  result  of  the  washing  is  a  milk-like  fluid,  which 
settles  at  the  bottom  of  the  trough  as  starch ;  it  is  then  mixed  with  fresh  water  and 
allowed  to  solidify  into  a  hard  substance,  which  is  cut  into  pieces,  poured  upon  a  linen 
cloth,  placed  on  a  hurdle,  with  a  plaster-of -Paris  vessel,  or  a  vessel  containing  gypsum, 
underneath,  to  dry  the  starch.  After  being  filtered  and  left  to  stand  for  twenty-four 
hours,  the  starch  dries  to  the  thickness  of  2  decimetres  upon  the  gypsum.  Of  late  the 
water  has  been  removed  by  a  centrifugal  machine.  The  moist  starch  contains  33  per 
cent,  water,  and  is  called  fresh  starch.  The  average  temperature  of  the  drying-rooms 
is  not  over  60°.  When  the  starch  is  dried  it  is  broken  into  pieces  by  iron  rollers.  The 
stalk  or  whole  starch  is  made  by  boiling  to  a  thick  paste,  which  is  forced  by  machinery 
through  a  small  opening  into  a  trough,  where  it  dries  in  a  kind  of  mould. 

Preparation  of  Wheat  Starch. — According  to  M.  O.  Dempwolf  (1869),  the  un- 
prepared wheat  contains : 

Water         .        .        .        .        .        .  10-51 

Ash 1-50 

Gum 14-35 

Starch 65-40 

Fatty  and  woody  fibre       .        .        .  8-24 


From  the  constituent  parts  of  wheat  it  is  seen  that — 


Starch 

Gum 

Husk 


>•  are  insoluble  in  water. 


Salts 

Albumen 

Dextrine 


h  are  soluble. 


68o 


CHEMICAL   TECHNOLOGY. 


[SECT.  vi. 


The  first  three  are  insoluble,  the  gum,  however,  being  gradually  dissolved  by  the 
lactic  acid  developed  from  the  seed,  while  the  starch  and  husk  remain  unattacked. 
There  are  two  methods  of  preparing  wheat  starch — viz. : 

A.  By  fermentation  (old  method)  of  the — 

a.  Ungroundj 
,    n   f      ,       [  Wheat. 
ft.  Ground      J 

B.  New  mode  of  treatment  without  fermentation. 
The  old  method  consists  of  the  following  operations : — 

1 .  Fermenting  the  wheat. 

2.  Washing  the  starch  from  the  mass. 

3.  Washing  and  cleansing  the  starch. 

4.  Drying  the  starch. 

The  whole  wheat  is  soaked  in  water  until  soft.  The  seed  is  separated  from  the 
husk  either  by  treading  in  sacks  in  a  flat  tub  of  water,  or  by  being  placed  under 
rollers,  and  the  pulp  thinned  with  water  .to  a  milky  fluid,  in  which  a  greater  part  of 
the  starch  and  gum  are  found.  After  standing  a  day  this  fluid  turns  acid ;  a  part  of 
the  gum  becomes  dissolved  by  the  action  of  the  lactic  and  acetic  acids,  and  is  taken  away 
and  replaced  by  fresh  water,  the  same  process  being  gone  through  until  the  fermenta- 
tion ceases,  when  the  starch  is  washed  with  water  and  dried.  In  the  fermenting  tub 
it  forms  with  the  water  a  thin,  sour  pulp.  The  time  varies  according  to  the  tempera- 
ture ;  all  the  gum  is  not  separated  until  about  twelve  to  thirty  days.  The  sour 
water  contains  acetic  acid,  lactic  acid,  butyric  acid,  succinic  acid,  ammoniacal  salts,  and 
the  mineral  constituents  of  the  wheat.  The  mass  is  then  placed  in  a  sack  and  trodden, 
the  milky  fluid  being  allowed  to  escape,  leaving  the  husk  and  refuse  gum  behind.  The 
milky  fluid  containing  starch  is  strained  through  a  fine  hair  sieve  and  washed  with 
water.  Another  method  is  that  of  placing  the  milky  fluid  in  a  tub  and  allowing  it 
to  settle.  The  first  layer  of  the  sediment  is  fine  starch,  next  a  mixture  of  starch,  husk, 
and  gum,  the  last  layer  containing  but  little  starch.  In  the  preparation  a  little 
ultramarine  blue  is  added  during  the  cleansing  process.  Of  late  the  centrifugal 
machine  has  been  used  for  the  purpose  of  drying  the  starch. 

Preparing  Wheat  Starch  without  Fermenting. — According  to  E.  Martin's  treatment, 
wheat  flour  is  mixed  with  water  to  a  paste,  100  parts  flour  to  40  parts  water;  the 
paste  remains  half  to  two  hours  to  affect  the  gum,  and  is  then  washed  in  a  fine  wire 
sieve  placed  over  a  tub.  The  starch  is  found  at  the  bottom  of  the  tub  mixed  with 
water,  and  is  placed  in  a  warm  spot  to  ferment  slightly.  It  is  dried  in  a  mass,  and 
goes  through  similar  processes  to  the  other  starch,  being  made  into  stalk  and  powder 
starch,  and  sold  in  packets. 

TOO  parts  of  wheat  flour  yield  25  per  cent,  of  gum  (gluten,  gluten  granule),  with  33 
per  cent,  of  water ;  the  fresh  gluten  is  mixed  with  a  double  weight  of  flour,  the  paste 
rolled  into  long  strips,  and  ground  into  granules  which  become  dry  at  30°  to  40°,  and 
are  afterwards  sifted.  The  consumption  of  this  granular  gum  is  extensive,  it  being 
employed  for  food  (with  ordinary  flour  as  macaroni),  art  purposes,  and  manufactures. 

Constituents  and  Uses  of  Commercial  Starch. — According  to  M.  J.  Wolff,  the 
constituents  of  commercial  starch  are  as  follows : — 


3- 

4- 

5- 

Water       .... 
Gum          .... 
Fibre 
Ash   .... 

I7-83 
0-48 

15-38 

0-50 

O«M 

14-52 

O'lO 

1-44 

o'O3 

17-44 

traces 

I  '20 

14-20 

1-84 
3-77 

rvCC 

17-49 
4-96 
2-47 

I  -2O 

Staxch       .... 

81-48 

u  3J 

83-59 

83-91 

8I-32 

79-63 

7379 

lOO'OO 

lOO'OO 

lOO'OO 

100  '00 

lOO'OO 

lOC'OO 

SECT.    VI.] 


STARCH  AND   DEXTRINE, 


68 1 


No.  i  was  the  finest  white  patent  starch  in  stalks,  of  a  bright  and  crystalline  appear- 
ance, made  from  pure  potato  starch  ;  No.  2,  the  finest  blue  patent  starch,  potato  starch 
coloured  with  ultramarine ;  No.  3,  pure  wheat  powder;  No.  4,  fine  wheat  starch  in  pieces ; 
No.  5,  medium  fine  wheat  starch  in  yellowish- white  pieces ;  No.  6,  ordinary  wheat  starch 
in  greyish-yellow  coarse  pieces,  that  upon  microscopic  examination  appear  as  a  mixture  of 
potato  and  wheat  starch.  Starch  is  used  for  stiffening  domestic  articles  in  washing,  for 
stiffening  paper,  and  extensively  in  the  linen  and  cotton  manufacture,  in  gum,  syrups, 
sago,  vermicelli,  &c.  It  is  also  a  basis  from  which  we  can  obtain  sugar.  Potato  starch 
is  preferred  for  domestic  washing,  but  where  great  stiffness  is  requisite,  wheat  starch 
is  used,  as  in  book-binding,  &c.  In  wheat  starch,  the  paste  is  formed  of  closely  united 
gelatinous  particles,  which  are  more  widely  disseminated  in  potato  starch,  the  latter 
being  transparent  and  more  suitable  for  stiffening  fine  linen,  ironing  smoother,  and 
not  sticking.  Wheat  starch  will  keep  fresh  upon  exposure  to  the  atmosphere  longer 
than  potato  starch,  the  latter  turning  sour  after  a  day's  standing. 

According  to  C.  Wiesner  (1868),  maize  starch  possesses  the  highest,  wheat  the  next, 
and  potato  starch  the   most   inferior  stiffening   qualities.       Maize    and   wheat  are 
considered  the  best  for  forming  a  smooth,  equal  paste.     Sugar  can  be  prepared  from 
starch  by  means  of  the  active  principle  of  malt — diastase.     From  this  sugar,  again, 
brandy  and  spirits  can  be  distilled.     According  to  the  researches  of  Liidersdorff : 
100  pounds  of  potato  starch  need  2 5 '5  pounds  of  dry  malt,  and 
100         „          wheat       „  „     90*5         „  „ 

to  effect  the  full  conversion  of  the  starch  into  sugar. 

Rice  Starch,  Maize  Starch,  Chestnut  Starch,  Cassava  Starch,  Arrowroot. — Rice 
starch  is  largely  manufactured  in  England,  France,  and  Belgium.  To  extract  the  gum, 
rice  is  placed  in  a  bath  of  weak  soda  solution — 287  grammes  of  caustic  soda  to  the  hecto- 
litre. After  standing  twenty-four  hours,  the  rice  grain  becomes  softened,  and  is  then 
washed,  ground  between  rollers  or  millstones,  and  placed  on  a  sieve  with  brushes  to 
retain  the  husk  or  bran.  The  water  strained  off  contains  the  starch,  which  is  washed, 
dried,  and  manufactured  into  the  form  required.  The  gum-containing  alkaline  lye  being 
neutralised  with  sulphuric  acid  is  fit  for  inferior  uses.  J.  &  J.  Colman's  rice  starch 
manufacture  employs  1000  workpeople,  and  the  result  of  their  manipulation  is  used  as 
the  customary  washing  starch,  the  stiffer  and  brighter  starch  for  ball  dresses,  window 
hangings,  and  for  the  size  in  paper  manufacture. 

Rice  Starch. — Mack  treats  rice  in  a  steeping-vat  with  double  sides  (Fig.  468). 
Atmospheric  air  rushes  in  from  all  sides 
in  such  quantities  that  the  mass  is  kept  in 
a  state  of  motion  like  ebullition.  The 
rice  is  heaped  up  on  the  perforated  false 
bottom,  p,  whilst  the  space,  B,  under  the 
false  bottom,  and  the  free  space  above  the 
rice  are  filled  with  the  dilute  soda-lye. 
The  air  is  introduced  under  pressure 
through  the  tube,  r,  into  the  receptacle, 
jR.  from  which  it  passes  through  many 
narrow  pipes,  t,  into  the  space,  jB,  and 
then  through  the  false  bottom,  p,  into  the 
rice.  The  floor,  a,  is  raised  towards  the 
centre,  so  that  the  liquid  can  be  let  off 
afterwards  through  the  cock,  h,  when  the  rice  is  left  half  dry  on  the  floor,  p. 

Maize  Starch. — Maize  is  softened,  ground,  pressed,  ground  again,  and  finally  treated 
with  caustic  alkalies.  This  treatment  is  important,  as  it  is  necessary  to  remove  oil, 
mineral  matter,  and  the  nitrogenous  compounds  which  enclose  the  starch.  Rice  starch  is 


r±: 


682 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


separated  into  three  qualities  by  a  process  of  elutriatioii,  which  contain,  according  to 
Archbold  : 

I.  u.                           in. 

98-5  ...           92-88  ...           90-33 
2-38                          4-25 

0-3  ...              0-60  ...              0-65 

1-2  ...              4-14  ...              477 


Starch  . 

Gluten  and  cellulose 

Ash 

Water  . 


Fig.  470. 


According  to  Tschirch,  maize  flour  contains  starch  granules  of  two  distinct  forms 

more  or  less  angu- 
lar, almost  isodia- 
metric,  and  poly- 
hedral granules 
often  adhering  to- 
gether in  groups 
of  nearly  the  same 
size  (Fig.  469) ; 
and  rounded 
grains,  varying 
much  more  in  size 
(Fig.  469,  m). 

The    starch 
granules    of    rice 
are  almost  exclu- 
sively angular  (tri-, 
quadra-,  pent-,  or 
hexangular). 
Large   or   conglo- 
merated masses  are  often  found  (Fig. 
470).     There  are  found  in  rice  flour, 
though  less  commonly  in  starch,  frag- 
ments of  such  conglomerates  (Fig.  47 1 ). 
The  sharpness  of  the  angles  is  the  most 
prominent  characteristic  of  rice  starch. 
According    to    Tschirch,    the    largest 
granules  do  not  exceed  8-5  micromillim., 
and  the  smallest  have  a  size  of  4*5  to 
6  micromillim. 

In  France  the  horse-chestnut  is  used 
for  the  manufacture  of  starch.  Chest- 
nuts produce  a  starch  possessing  the 
evenness  of  potato  starch  with  the 

stiflhess  of  wheat  starch.     100  parts  of  the  fresh  bitter  chestnut  give  19  to  20  per 
cent,  dry  starch. 

Arrowroot  is  obtained  from  the  Maranta  arundinacea  and  M.  indica,  cultivated 
in  the  West  Indies ;  it  is  very  like  potato  starch,  and  is  prepared  in  a  similar 
manner.  Cassava  starch  is  made  from  the  root  of  Jatropha  Manihot,  or  Manihot 
utittissima,  and  M.  aipin,  largely  cultivated  in  South  America,  the  West  Indies,  and 
the  Brazils. 

Cassava  is  used  as  an  article  of  consumption  both  in  Europe  and  the  Tropics.  The 
root  of  the  manioc  is  thoroughly  purified  from  its  poisonous  juice,  being  coarsely  ground 
to  allow  the  sap  to  escape,  and  roasted  in  an  earthenware  vessel,  the  cassava  forming 
into  granules  on  the  sides  of  the  vessel  (Cassava  sago,  or  Tapioka),  the  prussic  acid 


SECT.   VI.] 


STARCH   AND    DEXTRINE. 


683 


contained  in  the  root  becoming  volatilised.  From  arrowroot  and  the  analogous  roots 
containing  a  poisonous  juice,  arrowroot  derives  its  name,  having  been  used  by  the 
Indians  as  a  poison  for  the  tips  of  their  arrows.  Its  components,  according  to  Benzon, 
in  100  parts,  are: — Volatile 

oil,  0-07  part ;  starch,  26  parts,  Fig  ^lt 

89  per  cent,  of  the  starch  being 
obtained  in  a  powder,  while 
the  remainder  is  extracted 
from  the  parenchyma  by  boil- 
ing water ;  albumen,  1-58  part ; 
gum,  o'6  part ;  calcium  chlor- 
ide, 0*25  ;  insoluble  fibrin,  6 
parts;  and  water,  65-5  parts. 
It  is  known  in  commerce  in 
several  varieties — viz.,  Port- 
land arrowroot,  Arum  vulgare  ; 
East  India  arrowroot,  Curcuma 
angustifolia  ;  Brazilian  arrow- 
root, Jatropha  Manihot ;  Eng- 
lish arrowroot,  from  the  starch 
of  the  potato  ;  Tahiti  arrow- 
root, Tacca  oceanica. 

Sago. — Sago  is  made  from  the  soft  central  portion  of  the  stem  of  the  palm,  Sagus 
Rumphii.  According  to  J.  Wiesner,  the  Guadaloupe  sago  is  prepared  from  Raphia 
farinifera,  and  an  East  Indian  variety  from  Caryota  urens.  The  stem  is  torn  to  fila- 
ments and  elutriated  on  a  sieve  with  water.  The  starch  obtained  is  then  washed,  dried, 
and  sifted  into  a  copper  plate,  where  it  remains  a  hard  granular  substance.  A  greater 
part  of  the  common  sago  is  manufactured  from  potato  starch,  coloured  with  oxide  of  iron 
or  burnt  sugar. 

Dextrine. — Dextrine,  gommeline,  moist  gum,  starch  gum,  or  Alsace  gum,  isomeric 
with  gum  arabic,  and  expressed  by  the  formula  C6H10O5,  is  formed  by  boiling  starch 
with  a  small  quantity  of  almost  any  dilute  acid,  which  thins  its  consistence,  and  con- 
verts it  into  a  soluble  substance  similar  to  gum  arabic.  It  is  soluble  in  cold  water, 
insoluble  in  absolute  alcohol,  but  slightly  soluble  in  weak  spirits  of  wine.  Dextrine 
derives  its  name  from  dexter,  the  right,  from  the  action  of  this  substance  on  polarised 
light,  twisting  the  plane  of  polarisation  towards  the  right  hand.  Dextrine  in  grape 
sugar  is  converted  into  dextrose  by  the  action  of  dilute  acids.  Dextrine  solution  does 
not  ferment  with  yeast ;  but  a  little  yeast  mixed  with  a  large  quantity  of  gelatinous 
starch,  at  a  temperature  of  160°,  quickly  liquefies  it,  dextrine  being  produced,  the 
greater  part  of  which,  if  allowed  to  stand,  becomes  converted  into  grape  sugar.  From 
this  decomposed  dextrine  a  cheap  and  largely  employed  substitute  for  gum  arabic  is 
obtained.  The  components  of  this  decomposed  dextrine,  according  to  the  analyses  of 
R.  Forster  (1868),  are: 


i. 

2. 

3- 

4- 

5- 

6. 

Dextrine. 

Opaque 
Starch. 

Dark 
Dextrine. 

Gommeline. 

Old 
Dextrine. 

Bright 
Starch. 

Dextrine   .... 

72-45 

70-43 

63-60 

59-71 

49-78 

5  '34 

Sugar        .... 
Insoluble  substances 

877 
13'H 

1-92 
19-97 

7-67 
I4-50 

576 
20-64 

1-42 
30-80 

0-24 
86-47 

Water        .... 

5-64 

7'68 

14-23 

13-89 

18-00 

7-95 

lOO'OO 

lOO'OO 

lOO'OO 

lOO'OO 

100.00 

lOO'OO 

684  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

Potato  starch  is  preferable  to  wheat  starch  for  the  manufacture  of  this  material,  not 
only  on  account  of  its  cheapness,  but  for  its  greater  purity  at  an  equivalent  price. 
Dextrine  is  prepared  by — 

a.  Gently  roasting. 

b.  Carefully  treating  with  nitric  acid. 

c.  Boiling  with  dilute  sulphuric  acid. 

d.  Treating  with  malt  extract  (diastase). 

Preparing  dextrine  by  means  of  gentle  heat  is  an  easy  operation.  The  starch  is 
roasted  until  it  becomes  brown-yellow  in  colour,  in  a  large  copper  or  iron  plate 
cylinder,  similar  to  a  coffee- drum,  situated  on  one  side  of  the  oven.  Dextrine  is 
formed  at  a  temperature  of  225°  to  260°.  According  to  Heuze,  the  following  is  a 
better  method : — 2  kilos,  of  nitric  acid,  of  i  "4  specific  gravity,  with  300  litres  of  water, 
are  mixed  with  1000  kilos.  (=20  cwts.)  of  starch,  and  boiled  to  form  a  mass,  which, 
when  exposed  to  the  air,  becomes  dry.  It  is  sometimes  effected  at  80°,  but  it  becomes 
a  paste  at  100°  to  110°.  The  starch  changes  into  dextrine  in  an  hour  or  an  hour  and 
a  half  at  the  most ;  it  is  white  and  soluble  in  water.  Sulphuric,  hydrochloric,  and 
acetic  acids  will  produce  dextrine  ;  and  by  the  addition  of  water  to  dextrine,  dextrine 
syrup,  or  gum  syrup,  is  obtained. 

Dr.  Vogel  gives  a  simple  experiment  to  illustrate  the  action  of  dilute  sulphuric 
acid  upon  starch.  Nearly  all  kinds  of  writing-paper  are  so  very  largely  sized  with 
starch,  that  if  figures  or  letters  are  traced  on  the  paper  with  very  dilute  sulphuric 
acid,  and  then  dried,  the  application  of  iodine  in  a  dilute  solution  will  impart  a  blue 
tinge  to  that  portion  of  the  paper  not  affected  by  the  acid,  the  characters  remaining  white. 

Dextrine  is  extensively  used  instead  of  gum  arabic  in  printing  wall-papers,  for 
stiffening  and  glazing  cards  and  paper,  for  lip-glue,  surgical  purposes,  wines,  and  in  the 
fine  arts  it  is  applied  in  many  ways. 

SUGAR. 

Those  carbohydrates  which  are  comprised  under  the  name  of  sugar  are  divided  into 
two  great  groups  :  those  which,  disregarding  crystalline  water,  have  the  composition 
C6H1206 ;  and  those  which  correspond  to  the  formula  C12H22OU. 

I.  The  former  group  includes,  chiefly,  dextrose  (which,  when  it  occurs  naturally, 
should  be  known  as  grape  sugar,  starch  sugar,  &c.),  levulose  (fruit  sugar),  arabinose, 
cerasinose,   lactose  (galactose),  sorbine,  eucalyne,  inosite,  dambose,  mannitose,    and 
others. 

II.  To  the  group  C12H22On there  belong  saccharose  (cane  sugar  and  beet  sugar),  treha- 
lose  (mycose),  melezitose,  melitose  (raffinose),  maltose,  galactose  (or  lactose,  milk  sugar). 

The  sugars  of  the  latter  group,  on  treatment  with  dilute  acids,  undergo  inversion, 
i.e.,  take  up  the  elements  of  water,  and  are  converted  to  equal  quantities  of  sugars  of 
Oroup  I.,  one  of  which  is  always  dextrose : 

C12H220U     +     H20     =   CGH1206    +   C6H1206 

Saccharose   +    water   =  dextrose    +    levulose. 

Trehalose      +       „       =         „          +   dextrose. 

Melitose       +       „        =         „          +   eucalyn. 

Maltose        +       „        =         „          +    dextrose. 

Galactose      +       „        =         „        ^+   lactose. 

The  sugars  of  technical  importance  are  dextrose,  inverted  sugar  (dextrose  and 
levulose),  maltose,  and  saccharose. 

Grape  Sugar. — Grape  sugar  (potato  sugar,  starch  sugar,  glucose,  or  dextrose)  is  a 
sugar  crystallisable  with  difficulty,  occurring  in  a  non-crystallised  state  as  levulose  or 
chylariose  (yv\apiov,  syrup)  in  many  sweet  fruits,  in  the  vegetable  kingdom,  and  it 


SECT,  vi.]  <  SUGAK.  685. 

forms  the  solid  crystalline  portion  of  honey.     It  may  be  obtained  by  any  of  the  follow- 
ing processes  : — 

a.  By  the  conversion  of  starch,  dextrine,  cane  sugar,  or  some  gums,  by  means  of 

dilute  acids  or  diastase. 

b.  By  treating  cellulose  and  similar  vegetable  matter  with  dilute  acids. 

c.  By  decomposing  organic  substances,    such    as    amygdalin,  salicin,  ploridzin, 

populin,  quercitrin,  gallo-tannic  acid,  &c.,  which  by  treatment  with  dilute- 
acids  or  synaptase  (emulsin)  are   separated   into   grape   sugar  and   other 
substances. 
Grape  sugar  is  found  in  the  various  fruits  in  the  following  quantities  :  * — 


Per  cent. 

I'Vf 

Apricot 

I  -80 

Plum 

2'12 

Raspberry 

4-00 

Blackberry      . 

4-44 

Strawberry 

573 

Bilberry 

.        .        .        578 

Currant 

6-10 

Plum  (sweet)  . 

...       .        6-26 

Gooseberry 

•        •         7T5 

Cranberry 

7  '45  (according  to  Fresenius) 

Pear 

8  -02  to  10-8  (E.  Wolff) 

Apple 

8-37  (Freserius) 

7-28  to  8-04  (E.  Wolff) 

Sour  cherry 

.       ..        .        877 

Mulberry 

9-19 

Sweet  cherry  . 

.       1079 

Grape 

.       14-93 

Grape  sugar,  C6H1206H20,  crystallises  from  its  aqueous  solution  in  granular,  hemi- 
spherical, warty  masses.  It  is  less  easily  soluble  in  water  than  cane  sugar,  and  requires 
1 1  of  its  own  weight  of  cold  water,  while  in  boiling  water  it  is  soluble  in  all  propor- 
tions, forming  a  syrup  possessing  but  poor  sweetening  qualities.  There  are  required 
z\  times  more  grape  sugar  than  cane  sugar  to  sweeten  the  same  volume  of  water.  At 
120°  grape  sugar  loses  its  water,  and  has  the  formula  C6H12O6.  At  140°  it  is  converted1 
into  caramel.  Heated  with  caustic  alkalies,  melassic  acid  is  formed,  together  with 
humus-like  substances.  Treated  with  sulphuric  acid,  grape  sugar  forms  sulpho-saccharic 
acid  ;  and  with  common  salt,  a  soluble  compound  of  sweetish  saline  taste.  With  caustic 
potash  in  excess,  a  grape-sugar  solution,  when  heated  to  the  boiling-point,  reduces  the 
hydrate  of  copper  oxide  to  suboxide,  silver  oxide  to  metallic  silver,  and  gold  chloride  to 
metallic  gold.  A  mixture  of  potassium  ferricyanide  and  potash  with  the  aid  of  heat 
decomposes  grape  sugar,  and  discharges  the  original  yellow  colour  of  the  fluid.  Under 
the  influence  of  a  ferment  grape  sugar  suffers  many  changes,  the  product  varying  with 
the  ferment  and  method  of  treatment  employed.  Beer  yeast  decomposes  grape  sugar 
into  alcohol  and  carbonic  acid. 

100  kilos,  of  grape  sugar  give  : 

Alcohol      .....        51 'it 
Carbonic  acid     .         .        .        .        48^89 

There  are  also  found,  under  certain  conditions  of  temperature  and  concentration, 
the  homologues  of  alcohol — viz.,  propylic  alcohol,  butylic  alcohol,  and  amylic  alcohol ; 
and  under  all  conditions  glycerine  and  small  quantities  of  succinic  and  lactic  acids. 
When  fermentation  is  effected  in  the  presence  of  alkaline  reagents,  lactic  acid  is 

*  The  sweetness  of  a  fruit  does  not  depend  simply  on  the  quantity  of  sugar.     The  proportion 
and  the  kind  of  acid,  and  the  presence  or  absence  of  gum,  have  to  be  considered. — [EDITOR.  ] 


686  CHEMICAL   TECHNOLOGY.  [SECT.  vi. 

formed  without  any  disengagement  of  gas.  Ordinarily  the  formation  of  lactic  acid  is 
merely  a  stage  in  the  process  of  conversion,  the  lactic  acid  decomposing  into  butyric 
and  acetic  acids,  with  development  of  hydrogen.  Under  certain  conditions  mannite 
may  be  prepared  from  grape  sugar ;  several  other  gum-like  substances  may  also  be 
obtained.  If  to  a  grape-sugar  solution  a  small  quantity  of  caseine  and  calcium  carbon- 
ate be  added,  and  the  mixture  submitted  to  a  temperature  of  90°,  calcium  butyrate 
will  be  thrown  down  after  fermentation,  carbonic  and  hydrogen  gases  being  continu- 
ously evolved. 

Preparation  of  Grape  Sugar. — Grape  sugar  may  be  prepared  from — 

a.  Grapes. 

b.  Starch. 

c.  Wood  and  similar  vegetable  substances. 

When  grape  sugar  is  prepared  from  the  grape,  the  juice  of  the  Avhite  grape  is 
preferred,  and  set  aside  to  clear.  The  cleared  must  is  heated  to  the  boiling-point 
with  pieces  of  marble,  chalk  (not  with  burnt  lime),  or  witherite  (barium  carbonate), 
to  neutralise  a  portion  of  the  tartaric  acid.  It  is  then  allowed  to  stand  for  twenty- 
four  hours,  and  during  this  time  the  insoluble  salts  of  lime  are  deposited.  The  must 
is  now  cleared  with  ox  blood,  in  the  proportion  of  2  to  3  litres  of  blood  to  100  litres 
•of  must,  and  next  evaporated  to  41°  Tw.  After  remaining  a  short  time  in  a  tub  to 
clear,  the  impurities  are  removed,  and  the  must  again  evaporated — this  time  to  57°  Tw. 
By  these  means  a  syrup  is  produced,  from  which  the  grape  sugar  can  be  immediately 
obtained.  The  syrup  is  concentrated  by  boiling,  and  run  into  crystallising  vessels, 
where  after  three  to  four  weeks  the  sugar  crystallises  out ;  it  is  separated  from  the 
non-crystallised  chylariose  in  a  centrifugal  machine.  For  experimental  purposes  the 
crystals  may  be  separated  by  placing  the  concentrated  syrup  on  a  heated  porcelain  or 
.glass  plate. 

1000  parts  by  weight  of  grapes  give  : 

Must       ....  800 

Syrup      ....  200 

Raw  grape  sugar     .         .  140 

Pure  grape  sugar     .         .  60-70 

The  preparation  of  grape  sugar  from  starch  is  an  important  branch  of  the  sugar- 
'boiler's  art.  Dilute  sulphuric  acid  and  the  f  ecula  of  potato  starch  are  the  active  agents. 
The  principal  processes  are  the  following : — 

a.  The  Soiling  of  the  Starch-meal  with  Dilute  Sulphuric  Acid  is  effected  on  a  small 
scale  in  leaden  pans,  but  in  an  extensive  preparation  iron  pans  are  employed.  The 
-requisite  quantity  of  water  is  first  heated  to  the  boiling-point,  and  to  this  is  added  the 
sulphuric  acid  diluted  with  3  parts  by  weight  of  water.  The  starch  is  also  previously 
brought,  by  the  addition  of  water,  to  a  milky  consistency.  The  liquids  so  prepared 
are  mixed,  and  the  boiling  continued  until  all  the  starch  is  converted  into  sugar.  An 
intermediate  stage,  not  usually  noticed  by  the  manufacturer,  is  the  conversion  of  the 
starch  into  dextrine,  which  in  its  turn  suffers  conversion  into  grape  sugar.  The  entire 
conversion  of  the  dextrine  into  grape  sugar  cannot  be  ascertained  with  certainty  by 
the  iodine  test,  as  sometimes  a  purple-red  tint  is  produced,  while  in  others  there  is  no 
change.  The  most  reliable  test  is  that  with  alcohol,  founded  on  the  known  insolu- 
bility of  dextrine  in  an  alcoholic  menstruum.  To  i  part  of  the  solution  to  be  tested 
there  are  added  6  parts  of  absolute  alcohol :  if  no  precipitate  is  thrown  down  there  is 
no  dextrine  remaining,  and  the  conversion  has  been  entire.  The  proportions  of  the 
materials  are  generally  to  100  kilos,  of  starch-meal — 2  kilos,  of  ordinary  sulphuric  acid 
of  130°  Tw.  and  300  to  400  litres  of  water. 

The  conversion  of  the  starch  into  grape  sugar  is  hastened  by  the  addition  of  a  small 
quantity  of  nitric  acid. 


SECT,  vi.]  SUGAR.  687 

b.  The  /Separation  of  the  Sulphuric  Acid  from  the  Sugar  Solution  is  a  most  important 
operation,  for  the  colour,  purity,  and  flavour  all  depend  upon  success  in  this  stage 
of  the  process.     The  acid  is  neutralised  by  baryta  or  by  lime,  with  either  of  which 
it  forms   a  precipitate,  deposited  at   the  bottom  of   the   neutralisation   vessels,  and 
leaving   a   clear   supernatant   syrup.     The   baryta   can    be    employed  as    carbonate 
(witherite),  and  is   without   doubt    the   better    neutralising    agent,  barium  sulphate 
being  very  insoluble.     Lime,  although  ordinarily  used,  forms  with  the  sulphuric  acid 
a  sulphate  (gypsum)  that  is  not  perfectly  insoluble  in  water.     It  can  be  employed 
either  as  marble,  chalk,   or  caustic  lime.     The  neutralisation   is   completed  in  the 
boiling-pan  while  the  sugar  solution    is  still  hot.     For  every  kilo,  of  sulphuric  acid 
so  much  pulverised  marble  is  required  as  the  varying  strength  of  the  acid  may  demand. 
After  the  addition  of  the  marble  powder,  and  when  the  effervescence  has  subsided,  the 
liquid  must  be  tested  with  litmus-paper,  or,  better,  with  tincture  of  litmus ;  if  the 
sugar  solution  be  neutralised  when  at  41°  Tw.  density,  the  following  evaporation  will 
concentrate  even  the  smallest  quantity  of  sulphuric  acid  which  may  have  remained, 
and  render  another  neutralisation  necessary.     To  ensure  perfect  neutralisation  it  is 
useful  to  add  an  excess  of  barium  carbonate  in  the  proportion  of  250  to  500  grammes 
to  every  10  kilos,  of  sulphuric  acid. 

c.  Evaporating  and  Purifying  the  Sugar  Solution. — This  part  of  the  process  is 
accomplished  first  in  a  copper  pan  over  a  slow  fire,  or,  better,  by  heating  with  steam. 
The  impurities  separate  and  are  absorbed  in  the  scum,  which  is  removed  by  means  of 
ladles.  The  evaporation  is  continued  until  the  syrup  marks  21°  to  2 3°  Tw.,  when  it  is  passed 
through  a  filter,  generally  of  animal  charcoal.     It  is  then  removed  to  a  large  reservoir, 
and,  if  a  granular  sugar  be  desired,  evaporated  to  71°  to  73°  Tw.  in  flat  pans,  from  which 
it  is  taken  to  be  placed  in  the  crystallising  vessels.     These  vessels  are  provided  at  the 
bottom  with  twelve  to  twenty-four  holes,  into  which  wooden  plugs  are  fitted,  by  re- 
moving which,  when  the  sugar  has  crystallised,  the  molasses  are  removed.    The  crystals 
are  dried,  sifted,  and  either  pressed  into  sugar-loaf  forms  or  packed  in  casks.     The 
crystallisation  is  effected  in  eight  to  ten  days. 

The  manufacture  of  grape  sugar  from  wood  and  similar  vegetable  substances  is  only 
of  value  in  relation  to  the  production  of  spirits,  and  recently  as  a  bye-process  of  the 
manufacture  of  paper  from  wood. 

Composition  of  Starch  Sugar. — The  composition  of  starch  sugar  as  it  occurs  in 
commerce  is  very  varied.  During  inferior  seasons  the  marketable  starch  sugar  may 
contain  50  per  cent,  sugar,  32*5  per  cent,  foreign  substances,  and  17-5  per  cent,  water. 
G.  Schwaendler  found  by  the  analysis  of  various  samples  of  the  year's  (1870)  sugar  the 
following  percentages : 

I.  2.  3-  4-  5- 

Grape  sugar      .         .  67*5  ...  64*0  ...  67*2  ...  75'8  ...  62*2 

Dextrine   .         .         .  g~o  ...  17-4  ...  9-1  ...  9-0  ...  8'8 

Water        .         .         .  19-5  ...  11-5  ...  20-0  ...  13-1  ...  24-6 

Foreign  substances  .  4-0  ...  7-1  ...  37  ...  2*1  ...  4*4 


lOO'O  ...          lOO'O  ...          lOO'O  ...          lOO'O  ...          lOO'O 

Uses  of  Grape  Sugar. — The  sugar  prepared  from  starch,  in  addition  to  the  sugar 
yielded  really  by  the  grape,  is  largely  employed  in  wine  making  and  in  the  brewing  of 
beer.  In  the  latter  case  the  grape  sugar  is  prepared  by  means  of  diastase.  That  its 
use  is  extensive  may  be  gathered  from  the  fact  that  to  3  cwt.  of  malt  i  cwt.  of  potato 
sugar  is  employed.  It  is  also  employed  instead  of  honey  in  confectionery,  for  colour- 
ing liquors  and  vinegars  brown,  in  rum  and  cognac,  beer  and  wines.  In  the  latter 
cases  it  is  known  as  sucre-couleur,  being  then  a  grape  sugar  that  has  been  re- 
melted,  sometimes  with  the  addition  of  sodium  carbonate  or  caustic  soda  to  deepen  the 
colour. 


688 


CHEMICAL   TECHNOLOGY. 


[SECT.  vi. 


Grape  sugar  made  from  maize  in  America  is  used  in  the  manufacture  of  spurious 
honey.* 

Steiner  examined  four  kinds  of  starch  sugar ;  Wagner  analysed  a  French  crystal 
syrup  (V.)  and  a  solid  grape  sugar  (VI.) : 




I. 

H. 

III. 

IV. 

V. 

VI. 

Water       .... 
Ash  

1  5  '50 
0*30 

6-00 
2-50 

1  3  '30 
0-40 

7  -60 

I  -10 

12-15 

I5-I8 

Dextrose  . 
Maltose     . 
Dextrine   . 
Carbohydrates 
Proteines  . 
Acid  =  SOS 

45  '40 
28-00 
9-30 
1-50 
traces 
0-08 

26-50 
40-30 
15-90 
7-00 
i  -80 
0-03 

76-00 
S'oo 

5-30 

O'2O 
O-05 

42-60 
39-80 
8-90 

64 

21 

64-66 
18-22 

Sample  I.,  from  a  German  factory,  is  white  and  soft ;  the  other  samples  are  from 
English  factories,  No.  II.  being  obtained  by  treating  maize  with  sulphuric  acid  under 
high  pressure,  and  is  tough  like  IV. ;  III.  is  solid. 

Neubauer  examined  in  1875  a  number  of  German  starch  sugars,  and  found  on  an 

average : 

Fermentable  sugar   .        .        .        .  61-08 

Non -fermentable  matter  .        .        .  20-54 

Ash,  chiefly  gypsum          .        .         .  0*34 

Water 18-04 

Sieben,  in  1884,  found  the  following  composition  of  syrupy  starch  sugar : — 


Dextrose 

Maltose 

Dextrine 

Water 

Ash 


21-70 
15-80 
41-96 

2O-IO 

0-30 


German  starch  sugars  are  generally  obtained  from  potato  starch. 
The  product  obtained  in  the  United  States  from  maize  starch  treated  with  sul- 
phuric acid  (rarely  oxalic  acid)  has  the  following  composition  : — 


Dextrose 

Maltose 

Dextrine 

Water 

Ash 


Syrup. 

34-30  to  42'8o 
o-oo  ,,  19-30 

29-80  „  45-30 

14-20   ,,    22'6O 

0-32  „     ix>6 


Solid  Sugar. 
72-00  to  73  -40 

O.OO  „     3-60 

4-20  „     9-10 
14-00  „    17-60 

o'34  „    0-75 


Inverted  sugar  has  been  latterly  used  to  some  extent  in  the  manufacture  of  cham- 
pagne, in  Gallicising  wines,  in  confectionery,  &c.  It  is  obtained  by  inverting  solutions 
of  cane  sugar  with  carbon  dioxide.  It  is  a  mixture  (or  a  compound)  of  dextrose  and 
levulose. 

Maltose. — The  sugar  obtained  by  the  reaction  of  extract  of  malt  upon  starch 
paste  forms  a  mass  consisting  of  fine  crystalline  needles,  soluble  in  water,  of  a  faintly 
sweetish  taste,  and  convertible  into  dextrose  by  boiling  with  dilute  sulphuric  or  hydro- 
chloric acid.  In  a  solution  of  neutral  copper  acetate,  acidulated  with  acetic  acid, 
dextrose  reduces  red  cuprous  oxide  on  heating,  whilst  maltose  does  not.  Maltose  is 
directly  and  completely  fermentable  without  previous  conversion  into  dextrose. 

According  to  Schulze,  100  parts  of  anhydrous  maltose  have  the  same  reductive 
power  as  66-67  parts  dextrose.  The  air-dry  substance  contains  5  per  cent,  crystalline 
water.  Its  composition  corresponds  to  the  formula  C12H22On.H20.  If  dried  at  10° 


*  It  would  be  well  if  the  name  grape  sugar  were  reserved  exclusively  for  the  natural  product, 
and  if  the  factitious  varieties  were  known  as  starch  sugar. — [EDITOE.] 


SECT,  vi.]  SUGAR.  689 

in  a  current  of  air,  it  has  the  same  composition  as  cane  sugar.     According  to  Meissl, 
the  specific  rotatory  power  of  maltose  becomes  smaller  with  increasing  concentration 
and  rising  temperature,  and,  as  seen  by  the  sodium  light,  in  a  solution  containing 
P  per  cent,  of  anhydrous  maltose  at  T°,  it  may  be  expressed  by 
[a]D  =  i4°'375  ~  0-01837?  -  0-095!. 

The  rotatory  power  of  freshly  prepared  solutions  is  less  by  15  or  20  per  cent,  than 
that  of  such  as  have  stood  for  some  time.  It  melts  below  100°.  Anhydrous  dextrose 
crystallises  in  the  form  of  needles  and  columns,  which  melt  at  146°. 

According  to  Soxhlet,  for  obtaining  maltose  2  kilos,  of  potato  starch  are  made  into 
paste  with  9  litres  water  on  the  water-bath.  After  the  paste  has  cooled  down  to  60°  to 
65°,  an  infusion  of  120  to  140  grammes  of  air-dried  malt,  prepared  at  40°,  is  stirred  into 
the  paste,  and  is  kept  at  that  temperature  for  an  hour.  It  is  then  heated  to  a  boil, 
and  filtered  whilst  hot,  and  evaporated  to  a  syrup  in  flat  dishes.  This  syrup  is  then 
repeatedly  boiled  by  portions  with  alcohol  at  90  per  cent.  After  a  portion  has 
thus  been  extracted  once  or  twice,  it  is  lixiviated  with  absolute  alcohol.  The 
matter  thus  obtained  is  evaporated  to  a  syrup,  and  let  stand  -in  thin  layers  to 
crystallise. 

Dubrunfaut  attempted  to  produce  maltose  for  breweries,  distilleries,  &c.,  by  sacchari- 
fying maize,  potatoes,  &c.,  with  extract  of  malt.  The  patent  was  sold  for  ^10,000, 
but  it  has  not  proved  successful  in  practice. 

Cane  Sugar  (saccharose)  is  found  in  the  sugar-cane,  in  maize,  in  the  sap  of  several 
species  of  maple  and  of  the  birch,  in  the  beet,  the  carrot,  in  madder-root,  in  pumpkins, 
melons,  bananas,  pineapples,  and  in  several  species  of  palm. 

The  Sugar-came. — The  sugar-cane,  Saccharum  qfficinarum,  is  a  plant  of  the  grass 
tribe ;  its  stalk  is  round,  knotted,  and  hollow,  and  the  exterior  of  a  greenish  yellow 
or  blue,  with  sometimes  violet  streaks.  It  grows  from  2-6  to  6-6  metres  high,  and  from 
4  to  6  centimetres  in  thickness ;  the  interior  is  cellular.  The  leaves  grow  to  a  length 
of  i'6  to  2  metres,  and  are  ribbed.  The  plant  is  grown  from  seed,  and  also  cultivated 
from  cuttings. 

A  hectare  of  land  yields  raw  sugar : — 

By  15  Months'  Cultivation.  In  i  Year. 

From  Martinique    .        .        .        2500  kilos.  ...  2000  kilos. 

„     Guadaloupe  .        .        .        3000     „  ...  2400    „ 

„     Mauritius       .        .        .        5000      „  ...  4000    „ 

„     Brazil    ....         7500      „  ...  6000    „ 

Components  of  the  Sugar-cane. — The  sugar-cane  yields  the  largest  amount  of  sugar, 
generally  90  per  cent,  juice,  containing,  according  to  Peligot,  18  to  20  parts  crystallised 
sugar.  The  components  of  sugar-cane,  according  to  the  analyses  of  Peligot,  Dupuy,  and 
leery,  are  as  follows : — Martinique  (a) ;  Guadaloupe  (b) ;  Mauritius  (c). 

(«)  (&)  («) 

P<§ligot.  Dupuy.  leery. 

Sugar        .        .        .        18-0  ...  17 '8  .„  20*0 

Water       .        .        .        72'!  ...  72-0  ...  69-0 

Cellulose  ...         9-9  ...  9'8  ...  io-o 

Salts                                   —  ...  0-4  ...  0-7—1-2 

From  1 8  per  cent,  sugar  found  in  the  sugar-cane,  as  a  rule  not  more  than  8  per  cent, 
crystallised  sugar  can  be  realised.  The  loss  may  be  accounted  for  thus : — 90  per  cent, 
juice  is  expressed  from  the  cane,  from  which  only  about  50  to  60  per  cent,  can  be 
clarified  from  the  straw,  &c. ;  a  fifth  part  is  exhausted  by  refining ;  and  finally  two-thirds 
of  the  sugar  is  obtained  by  boiling,  while  the  rest  goes  to  the  molasses.  The  18  per 
cent,  sugar  may  be  realised  in  the  following  manner  : — 

2    X 


690 


CHEMICAL  TECHNOLOGY. 


[SECT,  vi. 


In  the  refuse  sometimes  remains 
By  skimming  .... 
In  the  molasses 
As  raw  sugar  .... 


6'o  per  cent. 


6-5        „ 
18-0        „ 

Preparing  the  Raw  Sugar  from  the  Sugar-cane.  —  The  preparation  of  raw  sugar 
from  the  sugar-cane  consists  in  first  expressing,  and  then  cleansing  and  boiling  the 
juice. 

1.  Expressing  the  Juice.  —  The  sugar-canes  are  crushed  in  a  press  consisting  of  three 
hollow  cast-iron  rollers,  a  b  c,  Fig.  472,  placed  horizontally  in  a  cast-iron  frame.     By 
means  of  the  screws,  i  i,  the  approximate  distance  of  the  rollers  is  adjusted.     One 

roller  is  half  as  large 

Fig.  472.  as   the    others,    and 

is  moved  by  three 
cogged  wheels  fitted 
on  to  the  axis  of  the 
rollers.  The  sugar- 
canes  are  transferred 
from  the  slate  gutter, 
d  d,  to  the  rollers, 
a  c,  which  press  them 
a  little,  and  from 
thence  they  are  car- 
ried over  the  arched 
plate,  n,  to  the  roll- 
ers, c  b.  The  pressed 
sugar-canes  fall  over 
the  gutter,  f,  the 

expressed  juice  collecting  in  g  g,  and  running  off  through  h.     The  middle  roller  is 
termed  the  king  roller  ;  the  side  cylinders  are  individually  the  side  roller  and  macasse. 
Latterly  the  diffusion-process  has  been  introduced  in  the  cane-sugar  works,  to  the 
great  improvement  of  the  yield.* 

2.  Refining  and  Boiling  the  Juice.  —  The  expressed  juice  is  removed  to  the  boiling 
house,  which  is  fitted  with  five  iron  or  copper  vessels.     To  15,000  litres  of  expressed 
juice  5  to  9  litres  of  milk  of  lime  are  added.     The  lime  neutralises  the  malic  and 
other  vegetable  acids,  and  upon  boiling  forms,  with  the  albumen  and  the  other  con- 
stituents of  the  juice,  a  thick  green  scum,  which  being  removed  the  juice  is  allowed 
to  remain  in  two  of  the  pans  to  evaporate.     A  fresh  scum  is  formed  on  the  first  pan, 
which  returns  after  a  second  or  third  time  of  removal.     A  juice  as  it  issues  from 
the  press  is  received  into  the  first  pan,  in  which,  by  slow  boiling,  it  becomes  a  thick 
froth,  changing  by  rapid  boiling  to  a  clear  colourless  fluid  ;  in  the  third  and  fourth 
pans  the  liquid  becomes  gradually  purer,  until  in  the  fifth  it  crystallises.     The  finger 
is  dipped  into  the  boiled  juice  to  test  its  consistence,   and  by  the  length  of  the 
pendant  drop,  which  ought  to  be  about  3  centimetres,  the  thickness  is  ascertained. 
The  boiled  juice  is  placed  in  a  large  open  wooden  vessel  of  about   16  centimetres 
capacity,  and  termed  the  cooler,  where,  after  standing  twenty-four  hours,  the  sugar 
crystallises,  the  cooler  being  provided  with  a  double  perforated  bottom  to  allow  the 
molasses  to  escape,  leaving  the  crystals  behind.     After  standing  five  or  six  weeks,  the 
molasses  dries  into  a  mass  commonly  known  as  moist,  raw,  or  Muscovado  sugar. 
The  molasses  passes  into  a  cistern  placed  underneath  the  cooler,  capable  of  con- 

*  If  the  further  improvements  devised  by  Prof.  Galloway  are  introduced,  the  sugar-cane  need 
fear  no  competition  in  a  fair  market. 


SECT,  vi.]  SUGAR.  691 

taining  15,000  to  20,000  litres  of  juice,  and  after  standing  fourteen  days  is  ready  for 
the  market.  In  the  French  and  English  colonies  sugar  is  exported  in  chests  covered 
with  fire-clay  under  the  name  of  chest  or  tub  sugar. 

Varieties  of  Sugar.  —  European  commerce  deals  with  the  following  kinds  of  raw 
sugar  :  — 

1.  West  Indian  —  Cuba,  San  Domingo  or  Haiti,  Jamaica,  Porto  Rico,  Martinique, 
Guadaloupe,  St.  Oroix,  St.  Thomas,  Havanna. 

2.  American  —  Rio  Janeiro,  Bahia,  Surinam,  Pernambuco. 

3.  East  Indian  —  Java,  Manilla,  Bengal,  Mauritius,  Bourbon,  Cochin  China,  Siam, 
Canton. 

Of  late  there  has  been  a  distinction  between  sugar  cultivated  by  slave  and  that  by 
free  labour  :  the  latter  comes  from  Jamaica,  Barbadoes,  Demerara,  Antigua,  Trinidad, 
Dominica  ;  the  former  from  Cuba,  Havanna,  Brazil,  St.  Croix,  and  Porto  Rico. 

The  mode  of  manufacture  varies  according  to  the  nature  of  the  foreign  substances 
that  always  form  part  of  the  constituents  of  sugar,  such  as  water,  fibre,  gluten,  sand 
or  earth,  soluble  mineral  salts,  acetic  and  other  acids,  all  of  which  must  be  destroyed 
before  the  sugar  can  be  refined.  According  to  Renner  we  have  in  the  following  sugars 
from  :  — 

Java.                               Havanna.  Surinam.  In  Sugar  Candy. 

Kaw  sugar          .        .        98*6—  83*1  ...  97*0  —  87*3  ...  92*3  —  85-4  ...        99-6 

Slime  sugar        .        .          5-5  —  0*3  ...          37  —  0*9  ...  4*4  —  i'6  ...          o'i 

Water        .        .        .          6'i  —  0*3  ...          3-5  —  0-9  ...  6-3—  3-6  ...          0-2 

Ash    ....          2'i  —  0*2  ...          i  '4  —  O'O  ...  2'o  —  i  '2  ...          o'i 


Molasses.  —  The  production  of  molasses  is  due  to  the  long-continued  heating  of  the 
cane  juice,  but  the  quality  varies  according  to  the  nature  and  culture  of  the  sugar- 
canes,  the  heat  of  the  season,  &c.  By  chemical  treatment  molasses  appears  as  a  con- 
centrated watery  solution  of  crystallised  sugar,  slime  sugar,  with  a  small  admixture 
of  caramel  and  mineral  salts.  It  is  a  dull  red-brown  sweet  fluid  used  principally  in  the 
colonies  for  the  manufacture  of  rum  ;  it  is  soon  converted  to  spirit,  and  then  quickly 
becomes  acetated.  Renner  gives  the  constituents  of  molasses  as  :  — 

Raw  sugar   .....  32*97  •••  4°°36 

Slime  sugar          ....  4*30  ...  7*38 

Water           .....  1371  ...  16*25 

Ash      ......  3-35  ...  378 

Caramel,  gum,  &c.         .        .         .  45  '65  ...  32'22 

Refining  the  Sugar.  —  Sugar  refining  consists  in  — 

1.  Dissolving  and  Refining.  —  The  raw  sugar  is  dissolved  in  water,  and  during  the 
process  of  evaporation  the  apparatus  is  connected  by  a  gutter  to  a  reservoir,  into  which 
the  sugar  flows.     It  is  then  submitted  to  a  straining  apparatus,  which  retains  the 
several  impurities.     The  refined  fluid  is  then  heated  in  a  copper  pan,  termed  the 
melting  pan,  the  water  adding  30  per  cent,  to  the  weight  of  the  sugar,  and  is  after- 
wards placed  in  the  refining  pan,  a  vessel  constructed  with  a  double  bottom.     For  the 
purpose  of  clearing,  a  mixture  of  albumen  is  added  in  the  shape  of  serum  of  blood,  or 
white  of  egg,  with  lime-water  and  sulphuric  acid,  an  addition  afterwards  being  made  of 
3  to  4  per  cent,  animal  charcoal  and  \  to  2  per  cent,  blood,  and  the  whole  heated  to 
the  boiling-point.     The  albumen  coagulates  and  forms  a  fibrous  scum,  containing  aU 
the  impurities. 

2.  Taylor's  filtering  apparatus  is  now  much  used  for  filtering  the  sugar,  charcoal 
being  employed  as  the  purifying  agent. 

3.  The  boiling  of  the  clear  sugar  in  pans  placed  over  a  vacuum  apparatus  resembles 


699 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


the  previous  boiling,  with  the  exception  that  the  fluid  is  rendered  purer,  10  to  12  per 
cent,  water  remaining. 

4.  Cooling  and  Crystallising. — When  the  sugar  begins  to  crystallise  on  the  surface  of 
the  vacuum  pan,  generally  at  80°,  the  temperature  is  lowered  to  about  50°,  as  too  great 
heat  at  this  stage  of  the  process  exercises  an  injurious  effect  upon  the  sugar,  which  now 
forms  an  amorphous  mass,  and  is  drained,  washed  with  clean  syrup,  and  prepared  for 
ordinary  loaf  sugar.     Sugar- candy  is  the  result  of  slow  crystallisation,  the  crystals  by 
this  means  acquiring  a  larger  size  and  more  regular  form. 

5.  The  shaping  of  the  crystallised  mass  into  the  form  of  a  sugar-loaf  is  accomplished 
by  evaporating  the  sugar  and  placing  it  in  earthen  conical  moulds  to  solidify  at  a 
temperature  of  25°  to  30°.     After  standing  ten  minutes  the  sugar  sets  into  form. 

6.  Drying  the  Sugar. — After  standing  twelve   hours   a   green-coloured  syrup  is 
obtained  from  the  crystalline  mass,  which  is  removed,  and  the  crystals  submitted  to  a 
centrifugal  process  of  drying,  then  placed  in  a  drying-stove  at  a  temperature  of  25°, 
which  is  gradually  increased  to  50°.     By  thus  refining  the  raw  sugar,  the  ordinary 
loaf  sugar  is  obtained. 

Beet  Sugar. — Most  of  the  sugar  consumed  on  the  European  continent  is  obtained 
from  a  species  of  beet. 

Species  of  Beet. — The  vegetable  known  as  beet-root  is  a  lai'ge  fleshy  root  of  a  plant 
of  the  species  Beta  maritima,  largely  cultivated  in  France,  Belgium,  Germany,  and 
Portugal  for  the  production  of  sugar.  There  are  several  varieties  of  the  two  species, 
the  white  beet  being  preferred  on  account  of  its  yielding  more  sugar,  and  also  for  its 
purity  of  colour,  the  red  beet  being  chiefly  cultivated  for  culinary  purposes.  There 
is  also  the  field  beet,  commonly  known  as  the  mangold  wurzel,  which  was  first  used 
as  provender  for  cattle  about  the  end  of  the  last  century.  The  sugar  beet  has,  in 
course  of  cultivation,  been  improved  by  many  new  methods  of  manuring,  &c.,  until  it 
yields  13  and  sometimes  14  per  cent,  of  sugar.  In  Germany  the  following  varieties 
of  beets  are  principally  cultivated : — 

i .  Quedlinburg  beet,  a  slender  rose-coloured  root,  and  very  sweet ;  it  is  matured 
fourteen  days  before  any  other  kind.  2.  Silesian  beet  is  pear-shaped,  with  bright 
green  ribbed  leaves :  it  is  known  as  the  green-ribbed  beet,  and  does  not  produce  so 
much  sugar  as  the  former.  3.  Siberian  beet  is  pear-shaped,  with  white-green  ribbed 
leaves,  and  is  known  as  the  white-ribbed  beet.  It  does  not  yield  so  well  as  the 
Silesian  beet,  although  of  a  greater  weight.  4.  The  French,  or  Belgian  beet, 
has  small  leaves  and  a  slender  and  spiral  root,  yielding  sugar.  5.  The  Imperial 
beet  is  slender  and  pear-shaped,  yielding  much  sugar.  The  king  beet  is  a  biennial : 
in  the  first  year  the  root  is  merely  developed,  in  the  second  it  bears  seed. 

The  following  is  a  list  of  the  countries  where  the  beet  is  cultivated  for  sugar : — 


In 

According  to  — 

Beets 
gathered 
in  ewts. 

The  Manufacture 
of  Suitable  Beets 
in  cwts. 

Into  Sugar 
in  pounds. 

Krause 
Burger 
Neumann 
Liidersdorff 
Thaer 
Stolzel 

Dumas 
Boussingault 

104—145 
169—193 
112—145 
146 
1  80 
I2O—l6o 

/I93 
(124 
149 

88—123 
143—164 
95—123 
I24 

153  ^ 
102—136 

168 
105 
127 

770  —  1084 
1256  —  1560 
836—1160 
1088 
1336 
896—1196 

1476" 
924 
1116 

Prussia      

Baden        

France  :  — 
Northern  Departments) 
Other                 „             } 
France       

In  general  140  to  160  cwts.  are  cultivated,  cut,  and  cleaned  per  acre,  there  being 
4  Magdeburg  acres  to  i  hectare,  which  usually  yield  sufficient  roots  for  three  days' 
work. 


SECT.   VI.] 


SUGAR. 


11-3 
0-8 

i '5 
OT 


37 


Chemical  Constituents  of  the  Beet. — The  flesh  of  the  beet  consists  of  a  quantity  of 
small  cells  containing  a  clear,  colourless  fluid.  The  constituents  of  the  sugar-beet, 
according  to  chemical  analyses,  are — 

Water .         .        827 

Sugar       .         .        . 

Cellulose 

Albumen,  caseine,  and  other  bodies 

Fatty  matter  .... 

Organic  substances,  citric  acid,  pectin  and  pectic1 
acid,  asparagin,  aspartic  acid,  and  betain,  a  sub- 
stance having,  according  to  M.  Scheibler,  the 
formula  C15H33N3O(i 

Organic  salts,  calcium,  potassium,  and  sodium,  oxal- 
ate  and  pectate   .         .         .         . 

Inorganic  salts,  potassium  nitrate  and   sulphate, 
calcium  and  magnesium  phosphate     .         .         .  / 

Near  Magdeburg,  where  the  beet  is  extensively  cultivated,  the  general  results 
give— 

The  greatest  sugar  production,  as  13 '3  per  cent. 
That  from  inferior  beets,  as          .9-2        ,, 
The  average  beet  yielding     .         .11*2        „ 

The  components  of  the  beet  vary  according  to  the  time  of  the  year;  at  some 
periods  it  contains  more  water  than  at  others,  from  82  to  84  per  cent,  being  the 
average.  In  the  autumn  it  does  not  contain  slime  sugar ;  in  February  and  March  the 
components  intermingle,  and  some  decrease  nearly  2  per  cent.,  as  shown  by  the  following 
analyses : — 

October. 
3 -49  per  cent. 
82-06 


Woody  fibre  and  pectin 

Water  . 

Sugar    . 

Slime  sugar  .         .    «*i<vj 

Mineral  salts          .         .    •-  ••£ 

Organic  acid  and  extractives 


o'oo 

075 
1-30 


February. 

2*52  per  cent. 
84*36        „ 
io'6o        «, 

0-65        „ 

0-63 

1-24 


lOO'OO 


\2\  cwts.  of  beet  yield  on  an  average  i  cwt.  of  raw  sugar. 

Saccharimetry. — For  obtaining  an  average  sample  a  piece  is  either  dug  out  or  rasped 
out  from  each  root.     The 
rasping  machine  of  Bothmer  **B!  473- 

consists  of  a  double  case,  A 
(Figs.  473,  474,  and  475), 
screwed  to  a  block  and  en- 
closing the  rasping  disc,  C. 
The  roof-shaped  friction- 
surfaces  of  this  disc  are 
fitted  with  a  rasp  lift,  and 
their  outer  edge  is  toothed 
like  a  saw.  The  disc  fixed 
on  the  axle,  D,  makes  1000 
revolutions  per  minute,  and 
can  turn  either  to  the  right 
or  to  the  left.  The  beets,  JR, 
are  thrust  through  the 

opening,  E,  by  means  of  a  wooden  handle,  H,  shown  in  section  in  Fig.  474.     It  is 
provided  with  four  iron  points,  s,  to  hold  fast  the  beets,  which  are  then  pressed  against 


$94 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


Fig.  476. 


the  rasper,  which  cuts  them  up  lengthwise  and  tears  them  to  a  pulp.  This  pulp  falls 
into  a  collecting-box,  J,  set  below.  The  pulp  thus  obtained  is  covered  with  alcohol, 
which  is  then  filtered  off,  or  it  is  lixiviated  in  an  extraction  apparatus. 

Stockbridge  recommends  a  lixiviation  apparatus,  the  cylinder  of  which,  A  (Fig.  476), 
is  a  glass  tube  somewhat  contracted  below,  32  centimetres  long  and  36  centimetres 
wide.  Through  its  lower  aperture,  closed  with  a  caoutchouc  stopper,  there  passes  a 
tube,  B,  ground  off  obliquely,  28  centimetres  long  and  o'8  wide,  connecting  the  ex- 
traction cylinder  with  the  flask,  E,  containing  250  c.c.,  and  traversing  its  caoutchouc 
plug.  The  annular  space  between  the  tube,  B,  and  the  cylinder,  A,  is  intended  to 

receive  the  beet-pulp,  and  holds  about  100  c.c.  The 
tube,  B,  has  an  aperture,  a,  just  above  the  caoutchouc 
plug,  and  round  it  at  this  point  is  wrapped  a  piece 
of  wire  gauze,  so  that  when  there  is  liquid  in  the 
pulp  it  can  run  off  clear  and  without  difficulty  into  the 
flask.  The  upper  end  of  the  cylinder  is  closed  with  a 
caoutchouc  stopper,  through  which  passes  the  pipe  of  the 
reflux  condenser,  c.  When  the  contents  of  the  flask 
are  boiled,  the  vapours  pass  through  the  ascending 
tube,  B,  into  the  cylinder,  A,  and  the  contents  are  heated 
almost  to  the  boiling-point  of  alcohol,  whilst  the  alcohol 
is  partly  liquefied,  saturates  the  beet-paste,  and  returns 
partly  through  the  aperture,  a,  into  the  flask,  E.  The 
alcoholic  vapour  condensed  in  A  passes  into  the  cooler, 
C,  where  it  is  liquefied,  and  drops  back  into  the  ap- 
paratus. In  order  to  effect  a  sudden  and  complete 
saturation  of  the  beet-pulp,  the  apparatus,  D  and  F,  is 
secured  to  the  lower  end  of  the  cooling  tube  by  means 
of  a  caoutchouc  stopper.  This  apparatus  is  a  tube,  2  '5 
centimetres  wide  and  7*5  centimetres  long,  closed  below, 
and  having  above  two  holes,  ft,  through  which  the  vapours 
arrive  in  the  cooling  tube.  The -alcohol  liquefied  in  the 
cooler  is  thus  not  permitted  to  drop  upon  the  contents 
of  the  extractor,  A,  but  it  is  compelled  to  collect  in  D. 
Through  the  bottom  of  D  there  passes  a  tube,  c,  bent 
above  like  a  syphon  nearly  to  the  bottom  of  the  vessel, 
whereby,  as  soon  as  alcohol  enough  to  cover  the  bend  of 
the  tube  has  collected  in  the  vessel,  the  syphon  begins  to 
work,  and  all  the  alcohol  which  has  collected  is  poured 
upon  the  beet-pulp.  Thus  the  entire  surface  is  covered  ; 
the  saccharine  juice  is  rapidly  displaced,  and  flows  through 
the  wire-gauze  and  the  hole  in  the  inner  tube  into  the 
flask.  This  process  repeats  itself  hourly,  from  twelve  to 
thirty  times,  according  to  the  intensity  of  the  heat. 

For  the  determination  of  the  sugar,  about  80  grammes  of  beet-pulp  are  placed  in 
the  extraction  tube  by  means  of  the  funnel,  g  ;  about  140  c.c.  of  alcohol  at  95  per  cent. 
are  poured  into  the  flask,  the  sand-bath  is  heated,  and  the  pulp  is  satisfactorily  lixiviated 
in  about  an  hour  and  a  half.  The  flask,  which  contains  the  total  sugar  of  the  sample,  is  re- 
moved from  the  extractor ;  its  contents  are  placed  in  a  200  c.c.  flask,  rinsed  with  alcohol, 
and  5  per  cent,  basic  lead  acetate  is  added.  The  flask  is  now  filled  with  95  per  cent,  alcohol 
up  to  the  mark ;  the  liquid  is  filtered  and  polarised  in  the  ordinary  manner. 

Extraction  of  Sugar  from  the  Root. — The  preparation  of  sugar  from  the  beet  consists 
in  the  following  operations  : — 


SECT,  vi.]  SUGAR. 

1.  Washing  and  cleansing  the  beet. 

2.  Separating  the  juice  from  the  root. 

a.   The  root  is  ground  to  a  pulp  and  subjected  to  hydraulic  pressure. 

ft.  The  juice  is  extracted  from  the  pulp  by  means  of  a  centrifugal  machine. 

y.  According  to  Schiitzenbach,  after  maceration  the  juice  is  separated  from 

the  pulp  by  water. 
8.  The  root  is  cut  into  thin  slices  and  placed  in  a  vessel  (diffusion  apparatus). 

with  water  at  a  certain  temperature. 

3.  Refining  the  juice  with  lime,  and  removing  the  lime  with  carbonic  acid. 

4.  Filtering  the  juice  through  charcoal. 

5.  Boiling  the  refined  juice  for  crystallisation. 

6.  The  manufacture  of  raw  and  refined  sugar. 

a.   Raw  or  moist  sugar. 
/3.  Refined  or  loaf  sugar. 

1.  Washing  and  Cleansing  the  Beet. — The  beet  when  newly  dug  requires  washing 
and  cleansing,  which  takes  10  and  sometimes  20  per  cent,  from  the  weight  of  the  root. 
Champonnois's  washing  machine  is,  perhaps,  the  most  successful.     It  consists  of  re- 
volving drums  of  open  iron-  or  wood -work,  placed  in  a  trough  supplied  with  water,  the 
drums  making  8  to  40  revolutions  in  a  minute.     The  beets,  cleansed  from  all  impuri- 
ties, and  washed,  are  cut  and  submitted  to  elutriation  on  a  sieve.  From  1000  to  1 200  cwts. 
beets  can  be  prepared  per  day  of  twenty  hours  with  2 -horse  power ;  the  length  of  the 
washing-drum  being  from  3-1  to  4  metres  with  a  diameter  of  i  metre,  the  drum  making 
from  30  to  40  revolutions  per  minute. 

2.  Separating  the  Juice  from  the  Root. — There  are  two  methods  of  effecting  this  : 
the  first  by  grinding  the  root  to  a  pulp,  and  then  removing  the  juice  by — 

a.    Pressing. 

/3.  Centrifugal  force. 

y.   Maceration. 

The  sugar  in  the  beet-root  is  contained  in  the  cells,  which  are  easily  opened,  but 
require  a  moderate  pressure  to  extract  the  juice  containing  the  sugar.  A  hand- 
grinding  machine  is  sometimes  found  sufficient  for  this  purpose;  but  Thierry's 
crushing  machine,  shown  in  the  following  illustration  (Fig.  477),  is  generally  used. 

Fig.  477. 


The  grinding  cylinder  (Fig.  478)  is  0-5  to  o-6  metre  in  length,  and  o'8  to  ro  metre 
in  diameter,  the  periphery  being  set  with  250  saw-blades,  i  (Fig.  477)  is  a  funnel 
to  admit  water ;  i  the  trough  into  which  the  roots  are  placed  ;  m  the  cistern  to 


696 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


receive  the  pulp.  The  motive  power  gears  with  a  and  s ;  and  the  motion  of  the 
axis  of  a  is  by  means  of  the  pinion,  6,  communicated  to  the  eccentric,  d,  and  friction 

roller,  e,  thence  by  the  arm,  g,  and  con- 
Fig.  478.  necting-rod,  h,  to  the  plunger,  f,  which 

presses  the  roots  against  the  edges  of  the 
saw-blades  concealed  by  the  case,  u,  the 
pressure  being  regulated  by  the  weight, 
k.  The  cylinder  revolves  1000  to  1200 
times  a  minute,  reducing  from  800  to 
1000  cwts.  of  beets  to  pulp  in  twenty 
hours.  The  water  from  t  is  necessary, 
that  the  pulp  may  be  ground  to  a  finer 
consistence. 

The  juice  is  obtained  by  pressing  the 

pulp  by  means  of  a  stone  or  iron  roller  through  a  series  of  linen  cloths.  But  in 
the  French  manufactories  the  hydraulic  or  Bramah  press  is  most  generally  adopted. 
The  pulp  is  placed  in  sacks  or  bags  between  iron  plates,  and  subjected  to  a  pressure  of 
500  to  600  Ibs.  The  expressed  juice  flows  from  the  bed-plate  into  a  pipe,  which  con- 
ducts it  to  a  receptacle.  100  cwts.  of  beet,  with  a  pressed  residue  of  18  per  cent.,  yield 
82  per  cent,  good  juice. 

The  production  of  juice  from  the  pulp  by  pressure  is  effected  either  by  the 
hydraulic  press,  the  roller  press,  or  the  filter  press.  But  pressure,  the  centrifugal 
process,  and  maceration  have  been  almost  entirely  superseded  in  Germany  by  diffusion, 
which  is  a  modification  of  maceration  depending  upon  dialysis. 

The  roots  are  cut  up  into  slices  of  about  i  millimetre  in  thickness,  and  digested  with 
pure  water  at  50°  in  closed  iron  cylinders.  The  sugary  juice  passes  through  the  walls 
of  the  cells  and  mixes  with  the  water,  whilst  water  enters  the  cells,  and  certain  non- 
saccharine  substances  remain  behind.  Hence  the  sugary  solution  is  tolerably  pure. 

The  vessels  used  for  diffusion  are  mostly  upright  iron  cylinders,  with  flat  or  arched 
bottoms,  having  a  large  opening,  capable  of  being  tightly  closed,  for  receiving 

Fig.  479. 


the  slices.  A  number  of  such  diffusers  connected  together  is  called  a  battery.  In 
order  to  keep  the  contents  at  the  required  temperature  of  50°,  there  is  in  each 
diffuser  a  copper  worm  lying  at  the  bottom  heated  by  steam.  The  vessels  are  con- 


SECT,  vi.]  SUGAR.  697 

nected  in  such  a  manner  by  means  of  pipes  that  the  same  portion  of  liquid  can  be 
driven  through  the  entire  battery.  The  driving  power  is  the  hydrostatic  pressure  of  a 
cistern  placed  6  to  9  metres  high. 

A  diffusion-battery,  with  10  vessels  and  juice-heaters,  is  shown  in  ground  plan, 

Fig.  480. 


Fig.  481. 


Fig.  479;  in  longitudinal  section,  Fig.  480;  and  in  cross  section,  Fig.  481.  From 
the  bottom  of  each  diffuser,  /  to  X,  passes  the  outflow  pipe  5,  and  opens  into  the  lower 
part  of  the  juice-heater,  where  it  is  divided  into  the  seven  heating-pipes.  At  the 
head-end  of  each  juice- 
heater  is  a  tube,  bent  at 
right  angles,  the  overflower, 
a,  Fig.  481,  which  connects 
the  juice-heater  with  the 
next  following  diffuser.  At 
the  bend  the  overflower  has 
a  horizontal  valve,  /.  The 
form  of  the  overflower  ap- 
pears from  the  ground  plan, 
Fig.  479.  Its  entrance  into 
the  neck  of  the  diffusers  is 
shown  in  Fig.  481. 

The  connection  of  the 
opposite  vessels,  V  and  F7, 
as  well  as  X  and  7,  is 
effected  so  that  the  juice- 
heater  is  to  the  right  of  the 
diffuser,  V.  The  overflow 
pipe  branching  off  from  this 
is  considerably  prolonged, 
and  makes  three  bends  at 

right  angles  before  it  opens  into  the  vessel  VI.  The  valve,  7,  of  the  overflower  lies 
exactly  in  front  of  diffuser  VI.  In  the  same  manner  X  is  connected  with  7.  The 
juice-heater  stands  on  the  right  of  X ;  the  prolonged  overflow  pipe  makes  three 
knee-shaped  bends  before  it  enters  the  neck  of  diffuser  7.  The  valve  of  the  diffuser 


698  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

lies  straight  before  the  neck  of  I.  Close  below  the  overflow-pipe  is  the  water-pipe,  6,  and 
the  pipe  leading  to  the  purifying  pans,  both  in  the  same  plane.  To  render  both  visible 
in  Fig.  480,  the  water-pipe  is  drawn  as  if  broken  away  in  some  places.  The  water- 
piping  lies  nearest  the  diffusers  ;  it  begins  at  /,  and  arrives  there  from  an  elevated 
cistern.  It  passes  along  the  diffusers  /  to  V,  turns  round,  passes  along  VI  to  X,  and 
ends  at  diffuser  X.  The  purifying  pan-pipe  begins  near  the  juice-heater  of  vessel  /, 
passes  from  7  to  V,  turns  round,  goes  from  VI  to  X,  and  is  here  prolonged  to  the 
purifying  pan  by  a  piece  not  shown  in  the  drawing.  The  water-main  has  in  front  of 
every  diffuser  an  upright  valve,  II,  by  means  of  which  it  is  possible  to  establish  or 
interrupt  the  connection  with  each  diffuser.  To  effect  the  connection,  a  short  piece  of 
piping  branches  off  from  the  main  and  passes  into  the  limb  of  the  knee-shaped  over- 
flower,  which  enters  the  diffusion  vessel. 

In  a  similar  manner,  the  piping  to  the  purifying  pans  is  connected  with  each  vessel, 
but  with  the  difference  that,  while  these  are  connected  with  the  lower  part  of  the  diffusers, 
the  water-main  is  connected  with  the  upper  part,  as  the  movement  of  the  juices  has  to 
take  place  in  such  a  manner  that  the  water  enters  above  and  displaces  the  juice  below, 
causes  it  to  pass  through  the  next  juice-heater,  and  passes  it  then  either  to  the  next 
following  vessel  or  to  the  purifying  pan. 

For  carrying  off  the  water  from  the  slicings,  there  are  used  the  two  pipes,  d  (Fig. 
479),  at  the  front  of  the  juice-heaters.  One  of  these  lies  in  front  of  /  to  V,  beginning 
at  I  and  ending  near  V,  in  an  open  channel,  df.  The  second  pipe  begins  near  X  and 
ends  near  VI,  in  the  same  channel  (Figs.  480  and  481).  The  pipes  for  the  slicing 
water  are  connected  with  the  lower  end  of  the  juice-heaters  by  short  pipes,  which  can 
be  closed  tightly  by  the  valves  4.  The  juice-heaters  are  heated  by  the  steam  which 
enters  their  jackets  from  above  at  7. 

The  upper  man-holes  of  the  diffusers  are  easily  accessible  from  the  platform,  e,  which 
runs  along  both  series ;  a  second,  supported  by  the  cross-beams,  f,  is  between  the  two 
series  of  diffusers  rather  lower  than  e,  so  as  to  give  access  to  the  valves  i,  2,  3.  A 
third,  g,  is  fixed  below  the  valves  4.  From  here  the  exhausted  slicings  are  removed 
by  a  mechanical  arrangement.  For  this  purpose  there  is  in  the  middle  a  sunk  channel, 
h,  at  the  bottom  of  which  an  endless  web  moves  in  the  direction  of  the  arrows.  It  is 
wrapped  round  the  tension  rollers,  i  i',  of  which  i  is  put  in  motion  by  a  driving  band 
at  the  side.  The  slicings  drawn  out  of  the  man-holes  fall  at  first  upon  the  platform,  g, 
and  are  swept  into  the  channel,  h,  where  they  are  carried  along  by  the  endless  web, 
and  on  arriving  at  the  roller,  i,  they  fall  upon  a  movement,  I,  in  order  to  be  taken  up 
by  the  little  boxes,  n,  and  conveyed  further. 

Diffusion  apparatus  in  which  the  slicings  are  carried  along  continuously  to  meet  the 
water  or  the  juice  have  not  yet  met  with  approval. 

The  advantages  of  the  diffusion  process  are  : — (i)  The  production  of  a  purer  juice, 
more  easily  worked  ;  (2)  a  better  cattle  food  ;  (3)  diffusion  allows  of  a  more  complete 
extraction  of  the  sugar  than  any  other  method  ;  (4)  considerable  economy  of  mechani- 
cal power;  (5)  the  press-cloths  are  dispensed  with  ;  (6)  labour  is  economised ;  (7)  the 
juice  is  more  concentrated ;  (8)  the  cost  of  the  installation  is  much  reduced. 

Composition  and  Treatment  of  the  Juice. — The  juice,  after  being  expressed  from  the 
pulp,  if  allowed  to  remain  exposed  to  the  action  of  the  air,  throws  down  a  dark  flaky 
precipitate.  The  more  free  acids  the  juice  contains  the  lighter  will  be  the  colour  of  the 
precipitate,  and  the  juice  will  appear  of  a  brown-red.  The  juice  is  not  only  a  solution 
of  sugar,  but  contains  the  soluble  constituents  of  the  beet,  in  which  nitrogenous  and 
mineral  substances  are  very  prominent.  Sugar  under  fermentation  forms  lactic  acid 
and  other  products ;  but  it  is  separated  from  all  the  impurities  and  refined  into 
crystals.  The  usual  method  of  refining  is  to  boil  the  juice  rapidly  in  copper  refining 
vessels  constructed  with  double  bottoms.  The  rapid  boiling  separates  the  coagulated 


SECT.   VI,] 


SUGAR. 


699 


juice,  whilst  the  free  acid  is  neutralised  by  the  introduction  of  dilute  milk  of  lime. 
The  lime  also  serves  to  separate  the  nitrogenous  substances  of  the  juice,  and  enters 
into  a  combination  with  a  small  portion  of  the  sugar,  forming  a  sugar-lime  or 
calcium  saccharate.  Lime,  too,  throws  down  from  their  salts  iron  protoxide  and 
magnesia,  while  potash  and  soda  are  set  free.  The  quantity  of  lime  added  depends 
upon  the  condition  of  the  root.  As  a  rule,  to  100  Ibs.  of  juice  i  to  2  Ibs.  of  lime  are 
added,  or  to  2  cwts.  of  roots  i  Ib.  of  lime.  The  insoluble  combinations  of  lime  are  sepa- 
rated from  the  juice  as  a  slime  by  filtering  in  a  filtering-press. 

3.  De-liming  or  Saturating  the  Juice  with  Carbonic  Acid. — The  clear  juice  is  by  no 
means  a  pure  sugar  solution,  but  contains  besides  free  sugar,  sugar-lime,  free  potash, 
and  soda,  sometimes  ammonia,  and  a  small  quantity  of  nitrogenous  organic  substances, 
decomposed  by  the  free  alkalies,  ammonia  being  largely  developed  by  their  evapora- 
tion. The  juice  also  contains  various  organic  acids  (as  aspartic  acid)  and  alkaline  salts 
(as  potassium  sulphate  and  nitrate).  The  decomposition  of  the  sugar-lime  effects  the 
removal  of  the  extraneous  substances  from  the  juice.  The  physical  method  of  puri- 
fying the  juice  is  by  filtering  it  through  animal  charcoal,  while  the  chemical  method 
is  effected  by  means  of  carbonic  acid.  The  use  of  carbonic  acid  was  first  recom- 
mended by  Barruel,  of  Paris,  in  1811,  and  later  by  Kuhlmann,  Schatten,  and 
Michaelis.  The  latter  obtained  the  gas  from  the  action  of  sulphuric  acid  upon  chalk, 
or,  better,  upon  magnesite ;  the  former  employed  the  gas  resulting  from  the  combus- 
tion of  charcoal  or  coke.  Lately,  Ozouf  has  prepared  carbonic  gas  by  heating  sodium 
bi-carbonate.  In  the  German  manufactories  the  decomposition  of  the  sugar-lime 
is  effected  in  a  Kleeberger's  pan  (Fig.  482).  This  apparatus  consists  of  a  cast-iron 
cistern,  Bt  to  contain  the  juice.  The  carbonic  acid,  having  been  washed  in  pure 


Fig.  482. 


Fig.  483. 


water,  is  admitted  by  the  pipe,  m,  which  dips  nearly  to  the  bottom  of  the  vessel,  B, 
and  is  divided  internally  by  a  partition  for  the  better  dissemination  of  the  gas.  The 
unabsorbed  gas  collects  in  B  over  the  juice,  whence  it  passes  through  the  opening,  p, 
into  the  upper  chamber,  A.  When  the  juice  sinks  through  p  into  B,  the^gas  there 
collected  passes  through  A  into  w,  and  is  thence  re-conducted  to  the  reservoir.  When 
the  juice  is  sufficiently  cleared,  the  carbonic  acid  cock,  o,  is  turned  off,  and  the  juice 
allowed  to  flow  into  a  reservoir  through  q,  where  the  carbonate  of  lime  settles.  The 
clear  juice  is  then  fit  for  crystallisation.  The  man-hole,  e,  is  provided  for  the  cleansing 
of  the  apparatus  from  separated  calcium  carbonate.  The  juice  to  be  de-limed  is  supplied 
to  the  cistern,  B,  by  means  of  the  pipe,  s,  and  the  gutter,  t. 

Other  Methods  of  De-liming  the  Juice.— Instead  of  employing  carbonic  acid  or 
animal  charcoal,  the  lime  of  the  sugar-lime  may  be  removed  by  the  addition  of  a  sub- 
stance or  an  acid,  which  forms  with  it  an  insoluble  body,  but  does  not  affect  the  sugar. 


700 


CHEMICAL  TECHNOLOGY. 


[SECT,  vi 


Oxalic  acid  is  suitable  for  this  purpose,  calcium  oxalate  being  insoluble  in  the  sugar 
solution,  but  the  acid  is  very  expensive,  and,  besides,  the  precipitate  is  too  fine,  passing 
through  the  filter.  Phosphoric  acid  is  used  for  the  purpose,  calcium  phosphate  separat- 
ing into  flakes,  which  can  be  easily  removed  by  filtering  through  a  thin  layer  of  char- 
coal. Any  free  phosphoric  acid  is  converted  into  ammonium  phosphate,  neutralising 
the  alkali,  while  the  excess  of  ammonia  is  volatilised  on  the  application  of  heat  to 
the  juice.  Oleic,  stearic,  and  hydrated  silicic  acids,  and  casein,  similarly  throw  down 
precipitates.  Acar  uses  pectic  acid,  which  forms  with  the  lime  an  insoluble  pectate. 
Morgenstern  has  found  a  magnesium  sulphate  prepared  from  the  Stassfurt  kieserite 
successful  in  removing  part  of  the  impurities  as  well  as  a  portion  of  the  colouring 
matter.  Frickenhaus  tried  hydrofluoric  acid.  In  1811,  Proust  recommended  calcium 
sulphite  ;  and  in  1829  Dubrunfaut  took  out  a  patent  for  the  employment  of  sulphur- 
ous acid.  Melsens,  of  Brussels,  in  1849,  employed  hyposulphurous  acid,  which  at 
100°  separates  the  lime  and  most  of  the  protein  substances,  and  disguises  for  a  time 
the  colouring  matter;  the  colour,  however,  returns  on  exposure  to  air,  and  remains 
permanent. 

Purifying  with  Baryta. — About  fifteen  years  ago,  Dubrunfaut  and  De  Massy 
patented  a  method  of  purifying  the  juice  by  means  of  caustic  baryta,  which  forms  with 
cane  sugar  at  the  boiling-point  the  insoluble  saccharate,  C12H22On.BaO ;  in  practice, 
sufficient  caustic  baryta  is  added  to  throw  down  all  the  sugar.  The  sugar-baryta  is 
thus  separated  from  the  supernatant  fluid,  in  which  all  the  foreign  substances  remain 
suspended  ;  and  is  next  treated  with  carbonic  acid  to  form  barium  carbonate  and  set 
the  sugar  free.  The  solution  is  then  filtered  and  some  gypsum  added,  which  gives  rise 
to  the  double  decomposition  of  the  barium  carbonate  into  sulphate,  and  of  the  gypsum 
into  calcium  carbonate. 

The  purification  of  the  juices  by  means  of  electricity  does  not  seem  to  have  a 
future. 

Filtration  through  Animal  Charcoal. — The  purpose  of  filtration  is  to  remove  a  part  of 
the  non-saccharine  constituents  of  the  juice.  Bone-black  was  first  introduced  into  the 

beet-sugar  manufacture  by  Derosne  in 
1812.  Subsequently,  Schatten  ob- 
served that  it  removed,  not  merely 
colouring  matters,  but  lime  and  salts 

Dumont's  filter. — Pajot  des 
Charmes  employed  animal  charcoal  in 
1822,  but  Dumont  was  perhaps  the 
first  to  make  its  use  successful  by 
means  of  a  filter  still  bearing  his  name, 
shown  in  vertical  section  in  Fig.  484 
and  in  plan  in  Fig.  485.  The  juice  is 
supplied  to  the  filter,  .4,  from  the  cistern, 
D,  the  supply  being  regulated  by  the 
ball-cock,  d  e.  The  pieces  of  charcoal 
in  A  rest  upon  the  sieve,  b  b,  the  per- 
colating juice  being  received  into  the 
cistern,  and  removed  by  the  tap,  o. 
C  is  a  man-hole  for  the  cleansing  of  the 
apparatus. 

Instead  of  this  filter  there  have 
been  lately  used  sheet-iron  cylinders, 

5  or  6  metres  in  height,  filled  with  granulated  bone-black.  When  its  purifying  power 
is  exhausted  it  is  lixiviated  with  pure  water,  so  as  to  recover  the  sugar. 


Fig.  484. 


SECT.  VI.] 


SUGAR 


701 


To  revivify  spent  charcoal  it  is  covered  with  warm  water  and  allowed  to  ferment, 
washed,  and  ignited  with  exclusion  of  air. 

In  Fichet's  furnace  the  gas-fire,  with  the  coal-shaft,  a  (Figs.  485  and  486),  and 


Fig.  485. 


Fig.  486. 


grating,  b,  is  supplied  with  fuel  from  above.  The  gene- 
rator gases  pass  through  the  channel  d  into  the  channel 
E,  with  numerous  burner  slits  in  its  top,  which  can  be 
enlarged  or  contracted  by  means  of  a  common  slide; 
the  slide  is  formed  of  a  plate  of  fire-stone,  the  position 
of  which  regulates  the  access  of  the  combustion  gases 
in  the  entire  length  of  the  channel  E.  When  this  has 
been  once  arranged  there  is  nothing  more  to  be  done 

but  to  keep  up  the  same  heat.  The  air  serving  for  combustion  enters  at  G,  but  is  pre- 
viously warmed  at  the  tubes,  J,  which  are  surrounded  for  this  purpose  with  an 
iron  screen,  S.  It  effects  the  greatest  development  of  heat  at  F ;  therefore  here  small 
especial  protective  walls  are  constructed  for  the  lateral  ignition  spaces.  The  fire  gases 
do  not  pass  in  a  straight  current  to  the  chimney,  but  the  draughts  are  so  arranged  that 
the  action  upon  the  charcoal  takes  place  in  several  distinct  spaces,  called  zones.  The 
charcoal  passes  through  the  grating,  R,  then  through  the  drying  zone,  D,  then  through  the 
preparatory  zone,  JS,  then  through  the  ignition  zone,  A,  and  lastly  through  the  cooling 
zone,  (7.  The  combustion  gases  go  upwards  in  the  middle  and  give  off  their  heat  laterally 
to  the  walls  or  screen  of  the  ignition-room,  are  then  turned  downwards  by  the  cover,  Q, 
and  pass,  as  shown  by  the  arrows,  up  again  through  K  and  H,  and  through  the 
internal  ignition  spaces  formed  of  inverted  funnels  placed  one  over  the  other,  carry  with 
them  the  ignition  products  issuing  from  the  intervals  of  the  funnels,  and  pass  then  down- 
wards to  the  space  J3,  where  they  give  a  preliminary  warming  to  the  charcoal  intended 
for  ultimate  ignition,  and  escape  finally  by  the  chimney,  0.  It  is  easily  seen  that  the 
combustion  gases,  on  their  arrival  in  the  zone,  B,  have  already  given  off  a  great  part  of 
their  heat,  and  that  the  temperature  in  B  will  be  lower  than  in  A ,  so  that  the  heat  is  well 


702  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

utilised  and  the  coal  is  heated  by  degrees.  Above  B  is  the  drying  zone,  D,  which  forms 
the  upper  part  of  the  column,  and  where  the  charcoal  is  kept  loose  by  the  inverted  chan- 
nels by  which  it  is  traversed,  whilst  the  air  which  rises  through  S  and  M  and  is  heated 
to  60°  to  70°,  passes  through  these  hollow  spaces,  D,  and  dries  the  charcoal.  This  is  then 
piled  up  upon  the  grate,  R,  in  heaps  of  2  metres  and  upwards  in  height,  and  falls 
slowly  into  the  space  beneath  as  it  is  drawn  away  below.  The  ignition  columns  are 
formed  of  funnels  placed  upon  each  other  and  held  in  their  places  by  supports  and 
bolts.  The  charcoal  is  now  between  the  slanting  sides  of  these  funnels  and  the  wall,  H, 
and  forms  around  each  a  free  inclined  plane,  whilst  it  is  heated  in  a  thin  layer  from 
within  and  without,  and  gives  off  on  its  surface  its  gases  to  the  passing  fire  gases.  As 
often  as  charcoal  is  drawn  away  below,  it  falls  downwards  in  the  entire  column, 
when  the  grains  roll  over  each  other,  renewing  the  free  surface  and  promoting  the 
escape  of  gases.  The  cooling  tubes,  J,  have  ribbed  or  undulated  surfaces,  which  pro- 
mote the  escape  of  heat  to  the  air  passing  upwards.  The  hot  air  passes  partly  through 
G  to  the  burner,  partly  ascends  through  M,  effects  the  desiccation  in  D,  and  escapes 
through  a  pipe  which  surrounds  the  chimney,  0,  so  that  its  heat  serves  to  increase  the 
draught.  Suitable  slides  allow  of  a  right  distribution  of  the  ascending  current.  The 
removal  of  the  charcoal  below  is  effected  by  a  box,  holding  about  13  litres  and  closed 
by  slides  moved  by  levers.  Each  movement  of  the  levers  delivers  13  litres  of  charcoal 
into  the  truck  below  and  fills  the  box  for  the  next  delivery.  The  workman  has  merely 
every  twenty  minutes  to  pull  the  levers  at  each  column  and  to  push  away  the  truck  which 
receives  the  carbon  from  three  or  four  columns.  As  the  heating  seldom  requires  addi- 
tional fuel,  the  manual  labour  is  reduced  to  a  very  small  quantity,  and  the  correct  igni- 
tion, which  is  regulated  by  the  burner-register,  is  quite  independent  of  the  workman. 
The  right  temperature  cannot  be  exceeded,  and  a  delay  in  emptying  has  no  bad  con- 
sequences, since  then  the  charcoal  merely  remains  rather  longer  at  a  dull  red  heat, 
which  occasions  no  injury.  If  two  or  three  lots  are  withdrawn  rapidly  in  succession  it 
is  of  no  consequence.  If  the  work  is  partly  at  a  stand  the  register  in  the  two  flues 
at  E  is  closed  to  one-tenth,  so  that  the  heat  in  the  furnace  is  kept  up  without  any 
important  consumption  of  fuel. 

Sulphurous  acid  is  often  used  for  saturation,  in  order  to  be  able  to  substitute  filter- 
presses  or  gravel  filters  for  the  more  expensive  animal  charcoal  filters.  Possibly  animal 
charcoal  may  be  ultimately  dispensed  with  in  obtaining  raw  sugars. 

From  the  thin  juice  the  water  is  withdrawn  after  filtration  by  two  processes,  known 
as  evaporation  and  boiling  down.  The  work  differs  according  to  the  intended  product, 
and  is  in  this  respect  divided  into  three  kinds — 

(1)  Haw  sugar  work ; 

(2)  Refinery  work,  which  is  the  yield  of  a  refined  product  from  the  raw  sugar ; 

(3)  Melis  work,  which  is  a  combination  of  (i)  and  (2),  and  aims  at  yielding  a  sugar 
fit  for  consumption  directly  from  beet- juice. 

Evaporation  Pans. — The  pans  generally  in  use  for  evaporating  the  juice  to  crystallisa- 
tion are  made  sufficiently  strong  to  withstand  high  steam  and  atmospheric  pressure. 
The  processes  of  evaporation  are — 

I.  Under  the  usual  air-pressure  : 

a.  In  pans  suspended  over  an  open  fire ; 

b.  With  high  steam  pressure  ; 

c.  By  hot  air. 

II.  By  diminished  air-pressure  or  vacuum  pans,  the  vacuum  being  produced : 

a.  By  the  air-pump ; 

b.  On  the  principle  of  the  Torricelli  vacuum ; 

c.  By  means  of  steam  and  condensation ; 

d.  By  combining  the  methods  a  and  b. 


CECT.    Vi.j 


SUGAR. 


703 


The  pans  are  constructed  to  prevent  the  boiling  over  of  the  juice.  One  of  the  bad 
effects  of  an  open  fire  is  the  danger  of  over-heating,  or  burning  as  it  is  called,  which 
deteriorates  the  quality  of  the  sugar  solution  in  various  ways,  forming  caramel. 

Evaporation  in  open  pans  has  been  entirely  abandoned  in  Germany.  The  evapora- 
tion apparatus  devised  by  Robert  and  Tischbein  has  introduced  a  new  principle  into  the 
chemical  arts,  which  comes  widely  into  play  where  evaporation  is  necessary.  The 
steam  occasioned  by  evaporation  in  the  first  pan  was  led  into  a  second,  where  it  also 
raised  the  temperature.  This  was  called  the  "  double  effect "  system,  or,  where  three 
vessels  were  used  in  connection,  the  "  triple  effect." 

Vacuum  Pans. — An  improved  evaporation  apparatus  was  invented  by  Howard,  in 
1812,  in  which  the  juice  was  placed  in  chambers  of  rarefied  air,  or  vacuum  pans. 
The  lowest  boiling  point  of  the  clear  juice  in  the  vacuum  pans  is  46'!°  C. ;  the  usual 

Fig.  487. 


temperature  at  which  the  sugar  is  boiled  is  65-5°  to  71-1°  C. ;  at  a  higher  temperature 
the  juice  loses  its  power  of  crystallisation,  and  forms  caramel.  The  vacuum  may  be 
considered  as  two  distinct  apparatus: — (i)  The  boiling  pan;  (2)  the  apparatus  for 
exhausting  the  air  and  condensing  the  steam  from  the  juice. 

In  France,  Derosne's  apparatus  is  extensively  used;  but  that  which  we  shall 
describe  meets  with  general  approval  in  Germany,  and  has  the  advantages  of  being 
simpler  in  construction  and  less  costly  to  work.  Fig.  487  is  a  perspective  view,  and 
Fig.  488  a  section  of  this  form  of  evaporating  pan.  The  boiling  pan,  £,  consists  of 
two  air-tight  hemispheres,  surrounded  by  a  funnel  connected  by  the  tube,  I,  with  the 
cendenser,  A.  The  apparatus  is  supplied  with  steam  by  r  s,  the  steam  circulating  in 
the  boiling  pan  by  means  of  the  pipes,  g  (Fig.  488).  By  opening  the  lever  valves,/, 


7°4 


CHEMICAL  TECHNOLOGY. 


[SECT.  TI. 


the  juice  can  be  run  by  means  of  the  pipe,  o,  into  the  pan,  p.  When  the  pan,  after 
continued  boiling,  requires  to  be  re-filled,  the  pipes,  I  and  w,  are  connected  to  an  air- 
pump.  The  manometer,  h,  shows  the  state  of  the  air-pressure,  which  can  be  regulated 
by  opening  the  pipes  connected  to  the  vacuum  chamber.  By  means  of  the  gauge- 
cylinder,  G,  the  quantity  of  syrup  in  the  boiling  pan  can  be  ascertained,  the  gauge- 
cylinder  being  connected  to  the  boiling  pan  by  the  pipes,  a  and  i,  and  the  height 
read  off  from  the  gauge-tube,  n.  For  the  purpose  of  ascertaining  its  consistency, 
the  syrup  can  be  removed  from  the  gauge-cylinder  by  means  of  either  of  the  three 
pipes,  bed.  By  u  steam  can  be  admitted  to  the  boiling  pan  and  condenser,  e  is 
generally  of  stout  glass,  through  which  the  state  of  the  juice  can  be  observed,  g  is 
the  grease-cock,  butter  or  Sostman's  parafiine  being  generally  used  to  prevent  the 
adhesion  of  the  scum  to  the  working  parts  of  the  pan,  the  taps,  &c.  f  is  the  man-hole. 
The  condenser  consists  of  the  jacket,  B,  arranged  to  prevent  the  mixing  of  the  juice 
with  the  water  used  for  condensation,  x  is  the  gauge.  The  pipe,  m,  conveying  water 
to  the  condenser,  terminates  in  a  rose,  z  is  a  thermometer,  showing  the  interior 
temperature  of  the  boiling  pan. 

Fig.  488. 


The  air-pump  being  set  in  operation,  the  tube,  c,  is  opened,  and  the  gauge-cylinder 
filled  by  the  juice  rising  from  q.  By  closing  m  and  opening  z,  the  juice  is  admitted 
to  the  boiling  pan.  When  this  is  half  full,  the  steam  pipe,  s,  is  opened,  the  steam 
quickly  heating  the  contents  of  the  pan  to  the  boiling-point.  The  condenser  is  then 
placed  in  working ;  by  opening  the  pipe  I,  the  steam  of  the  juice  passes  into  the  con- 
denser, where  it  is  speedily  condensed,  passing  with  the  water  through  /3.  Trappe's 
arrangement  is  sometimes  found  useful  in  working  the  Torricelli  vacuum.  The  con- 
denser is  10*6  to  ii  metres  above  the  pan  ;  from  it  reaches  a  pipe  to  a  water  reservoir 
beneath,  the  height  of  the  water  in  this  pipe  indicating  the  degree  of  rarefaction  in 
the  pan. 

The  construction  of  vacuum  apparatus  has  been  lately  much  improved. 

In  the  apparatus  of  Wellner  and  Jelinek,  with  horizontal  heating  pipes,  the  bottom 
(Figs.  489  and  490)  is  formed  by  two  sides  converging  obliquely.  In  order  to  open 
and  shut  the  evacuation  valves,  c,  at  pleasure,  they  should  be  connected  with  the 
arrangement  shown  in  the  drawing.  This  consists  of  an  angle-lever,  f}  turning  on  the 
bolt,  fy  With  one  of  its  arms,  fv  the  valve,  c,  is  connected  in  such  a  manner  that 


SECT. 


VI.] 


SUGAR. 


705 


it  can  turn  on  d,  whilst  the  second  arm,y"2,  leans  against  the  lower  end  of  a  projection 
of  the  sledge,  g.  The  sledge  slides  in  a  smaller  tail-shaped  groove,  h,  of  the  guiding- 
piece,  i,  and  can  be  raised  or  lowered  by  turning  the  screw,  j.  If  the  screw  is  raised 
the  valve  opens  in  consequence  of  its  weight  and  the  pressure  of  the  liquid,  so  that  the 
contents  can  flow  out.  By  screwing  down  g,  the  lever,  f,  is  turned,  and  the  valve  is 
shut.  The  figure  represents  for  every  valve,  c,  a  special  screw,  j,  with  its  accompany- 
ing sliding-piece,  g. 
But  the  arrangement 
can  be  so  made  that, 
instead  of  the  bolt, 
f3,  a  shaft  is  intro- 
duced, having  as 
many  arms,  fv  as 
there  are  valves,  and 
which  can  be  turned 
by  a  single  arm,  /2. 
The  heating  steam 
circulates  from  the 
boxes,  k,  through  the 
vertical  tubes,  I. 
There  is  also  a  longi- 
tudinal channel  in 
the  bottom,  capable 
of  being  heated.  As 
a  sign  of  the  sufficient 
concentration  of  the 
boiled  juice  several 
tests  are  in  use.  The 
determination  of  the  specific 
gravity  is  not  decisive.  We 
may  say  in  general  that  the 
boiling  down  may  be  carried 
from  7 2° to  76°  Tw.  (taken  hot). 
Among  the  empirical  tests 
may  be  mentioned  the  thread 
test.  A  drop  of  the  liquid  is 
taken  up  between  the  thumb 
and  the  forefinger,  and  the 
concentration  is  judged  by 
the  length  to  which  a  thread 
can  be  drawn  out  and  the 
manner  in  which  it  breaks. 
If  the  juice  is  not  sufficiently 
boiled  the  thread  soon  breaks. 
On  further  evaporation,  it  can 
be  drawn  out  as  far  as  the 
separation  of  the  fingers  will 
allow.  If  the  thread  tears 

about  mid-length,  and  the  upper  part  contracts  into  the  shape  of  a  hook,  it  is 
considered  that  the  concentration  is  sufficient.  This  is  the  "  hook  test."  The 
"  blow  test "  consists  in  taking  a  little  of  the  boiling  liquid  in  a  flat  scum-spoon, 
and  blowing  against  it,  when  bubbles  are  formed  on  the  far  side,  the  size  and  irides- 

2    Y 


Fig.  490. 


706 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


cence  of  which  show  what  degree  of  concentration  has  been  reached.  In  inferior 
liquids,  crystallisation  takes  place,  not  in  the  cooler,  but  in  the  vacuum-pan. 

If  the  liquid  is  boiled  "  blank,"  it  is  a  hot  saturated  solution  of  saccharose.  If 
boiled  "  to  crystal,"  it  is  a  mixture  of  crystals  of  saccharose  with  the  saturated  solution. 
There  are,  besides,  the  same  non-saccharose  matters  as  in  the  thick  juice.  The  water 
ranges  from  6  to  14  per  cent.,  and  the  sugar  from  68  to  90.  The  mass  may  then  be 
treated  either  for  raw  sugar  or  for  consumption  sugar  (so  called). 

If  the  mass  has  been  boiled  blank,  the  crystallisation  must  be  managed  so  as  to 
•give  the  largest  yield  of  well-developed  crystals.  Coarse  crystals  can  be  more  rapidly 
and  thoroughly  freed  from  treacle  than  the  smaller  crystals,  and  give  the  product  a 
better  appearance.  The  more  concentrated  the  solution,  and  the  more  rapidly  it  has 
been  cooled,  the  smaller  are  the  crystals.  In  order  that  the  crystallisation  may  pro- 
ceed slowly,  the  room  where  the  crystallisers  are  set  (the  filling-room)  is  heated  to 
3o°-35°.  The  crystallisers  hold  from  i  to  20  hectolitres.  Beneath  the  spout  through 
which  the  mass  passes  from  the  vacuum  -to  the  filling -room  there  is  a  flat  dish,  the  so- 
called  cooler,  in  which  it  is  allowed  to  remain  until  it  has  grown  tough  from  the  forma- 
tion of  crystals.  It  is  then  poured  into  the  crystallising  vessels  or  forms. 

If  the  mass  has  been  boiled  "to  crystal,"  the  mass  is  filled  direct  from  the  vacuum 
into  the  forms  at  a  temperature  of  5O°-6o°. 

When  the  crystallisation  is  finished,  the  next  step  is  to  separate  the  crystals  (first 
product)  from  the  syrup.  This  is  generally  effected  in  a  centrifugal.  The  most  im- 
portant part  of  the  instrument  is  a  drum,  open  above  (a,  Fig.  491),  of  a  fine  metallic 

tissue,  strengthened  externally  by  iron  bands. 
It  is  made  to  revolve  in  a  cast-iron  frame,  b, 
at  a  speed  of  1000  to  1500  rotations  per  minute. 
To  this  end  the  iron  axle,  e,  contains  at  its  upper 
end  a  conical  friction  wheel,  c,  covered  with 
leather,  and  turned  by  another  conical  wheel,  d. 
The  inner  part  of  the  drum  is  contracted  by  a 
sheet-iron  cone,  g,  by  which  the  sugar  to  be 
dried  is  brought  more  to  the  margin  of  the 
drum,  and  room  is  obtained  for  three  heavy 
pieces,  which  serve  to  maintain  the  equilibrium 
of  the  drum  in  its  rapid  rotation.  According 
to  the  nature  of  the  mass,  from  30  to  50  kilos. 
are  put  into  the  centrifugal ;  the  mass  rises  up 
on  the  sides,  and  the  syrup  issues  through  the 
meshes  of  the  wire  gauze,  whilst  dry  sugar 
remains  behind. 

The  syrup  remaining  from  the  coarse  sugar 
is  boiled  in  the  vacuum  pan,  and  worked  up 
to  a  filling  mass,  from  which  a  second  product 

and  a  syrup  from  the  second  product  are  obtained.  The  latter,  on  repeated  boiling,  yields 
a  third  product,  and  the  syrup  of  the  latter  again  yields  a  fourth  product,  and,  as  a  final 
residue,  treacle.  The  second  product  is  mostly  sold  mixed  with  the  first.  The  third 
and  fourth  are  thrown  into  the  thick  juice  to  improve  its  quality. 

Consumption  Sugar. — Raw  sugar  from  the  beet,  known  as  consumption  sugar,  is 
distinguished  from  that  of  the  caiie  by  containing  substances  of  a  disagreeable  smell  and 
taste.* 

*  It  must  be  remarked  that  even  the  most  carefully  refined  beet  sugars  possess  a  remnant  of 
this  taste,  which  can  be  detected  by  experienced  sugar  buyers,  and  much  more  readily  by  bees, 
which  reject  beet  sugar  if  cane  sugar  is  at  hand.  It  may  be  added  that  raw  beet  sugar  is  some- 


vi.]  SUGAR.  707 

"Consumption  sugar"  is  met  with  in  commerce  in  three  forms — (i)  As  crystal 
sugar  (something  like  the  form  in  which  cane  sugar  was  produced  by  Finzel's  process) ; 
•(2)  as  juice-melis  (with  its  modifications,  cube  sugar  and  pile) ;  and  (3)  as  farin.  The 
iirst  kind  consists  of  distinct,  isolated  crystals ;  melis  is  a  heap  of  agglomerated  crystals, 
which  either  takes  the  form  of  the  crystallising  vessels,  or  is  broken  into  lumps  or  into 
fragments  as  pile ;  farin  is  sugar  ground  to  a  fine  meal,  the  crystalline  appearance  being 
intentionally  destroyed. 

For  the  production  of  crystal  sugar  the  clear  liquor  is  boiled  slowly  and  continu- 
ously in  the  vacuum  pans,  with  a  reduction  of  temperature  towards  the  end,  so  as  to 
produce  distinct  crystals.  The  contents  of  the  vacuum  pan  are  washed  into  the  centri- 
fugal with  syrup.  Some  of  the  syrup  adheres  to  the  crystals  after  whizzing,  and  has 
to  be  removed  by  washing  the  crystals,  the  so-called  "  covering." 

"  Covering"  is  resorted  to  in  obtaining  all  the  finer  sorts  of  raw  sugar,  and  is  either 
water  covering,  syrup  covering,  steam  covering,  or  steam-vapour  covering.  Water  cover- 
ing is  effected  by  spirting  water  into  the  revolving  drum,  which  dilutes  and  washes  away 
the  syrup,  but  involves  a  considerable  loss  of  sugar,  and  has  therefore  been  mostly  given 
up.  Washing  the  crystals  with  a  clear,  saturated  solution  of  sugar  is  in  very  general  use, 
both  in  the  centrifugal  and  in  the  moulds.  The  liquid  thrown  out  is  added  to  the  thick 
juice.  Steam  washing  is  effected  by  admitting  steam  at  a  low  tension,  which  condenses 
to  drops,  and  acts  in  the  same  manner  as  water.  The  steam-vapour  covering  consists  in 
admitting  into  the  drum  a  mixture  of  steam  and  air  cooled  down  to  50°. 

Melis  is  the  commonest  kind  of  consumption  sugar,  and  is  obtained  either  directly 
from  the  juice  or  by  adding  sugar  to  the  concentrated  syrup.  The  quality  of  the  melis 
depends  upon  the  proportion  and  the  purity  of  the  sugar  thrown  in.  If  much  is  added, 
and  if  sufficient  animal  charcoal  is  used,  it  cannot  be  sharply  distinguished  from  refined 
sugar.  As  it  retains  a  slight  yellowish  tone,  it  is  got  up  with  ultramarine,  which 
masks  the  natural  tone  and  gives  the  product  a  bluish-white  reflection. 

The  forms  or  moulds  hold  from  1 5  to  1 7  kilos,  of  filling  weight,  and  yield  loaves  of  from 
10  to  12  kilos,  in  weight.  These  moulds  are  of  sheet-iron,  lined  with  enamel.  The  point 
after  filling  is  turned  downwards,  and  a  tube  is  attached,  through  which  the  syrup  runs  off. 
Melis  is  sold  as  cube  sugar  and  as  pile.  To  produce  the  former  the  mass  is  run 
into  plates  and  converted  into  cakes  of  equal  size.  Pile  is  a  coarse  melis,  produced  in 
Austria  for  the  Italian  market. 

Farin  is  a  ground  consumption  sugar,  made  up  of  products  which  would  be 
unsaleable  in  their  original  form. 

Sugar-candy. — The  large,  hard  crystals  formed  during  the  various  stages  of  sugar 
•manufacture  are  known  as  sugar-candy.  The  commercial  article  is  generally  obtained 
from  cane  sugar,  the  crystals  of  beet-root  sugar  being  too  long  and  flat.  The  amount 
•of  sugar-candy  made  from  beet  sugar  does  not  exceed  20  per  cent,  of  the  entire  produc- 
tion. The  sugar  selected  for  candy  is  mixed  with  3  to  4  per  cent,  of  animal  charcoal, 
then  cleared  with  white  of  egg,  and  filtered.  It  is  next  boiled  in  a  copper  or 
enamelled-iron  pan  over  an  open  fire,  whence  it  is  conveyed  to  a  crystallising  vessel, 
the  sides  of  which  are  perforated  with  a  series  of  holes,  in  eight  or  ten  concentric  rings, 
the  distance  between  each  hole  laterally  being  less  than  that  between  each  ring. 
Through  these  holes  the  candy  crystallises,  the  size  of  the  holes  being  adjusted 
to  the  consistency  of  the  boiled  sugar  by  means  of  a  paste  made  of  fine  clay, 
ashes,  and  ox  blood.  The  temperature  of  the  drying-room  is  maintained  at  75°  for  six 
days,  when  it  is  reduced  to  45°  or  50°,  and  in  eight  to  ten  days  the  crystallisation  is 
complete.  During  the  crystallisation  the  candy  must  not  be  moved  or  shaken,  or  the 

times  coloured  with  a  coal-tar  yellow  dye,  and  is  then  exported  to  England  for  sale  as  "  Demerara." 
This  is  done  with  the  double  purpose  of  obtaining  an  illicit  profit,  and  of  injuring  the  reputation  of 
cane  sugars. — [EDITOR.] 


708  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

air  allowed  to  affect  it.  Upon  the  completion  of  the  crystallisation,  the  candy  is  found 
covered  with  a  mixture  of  syrup  and  small  crystals ;  these  are  removed  by  filling  the 
crystallising  vessels  with  weak  lime-water.  The  rinsing  water  must  be  lukewarm,  as 
cold  water  cracks  the  crystals,  and  hot  water  makes  them  blind,  as  it  is  technically 
termed.  The  crystallising  vessel,  when  emptied  of  the  rinsing  water,  is  soaked  to  remove 
all  saccharine  matter,  and,  if  this  be  not  effected  with  hot  water,  a  smooth  stone  is  used 
to  knock  away  the  adhering  crystals.  After  standing  a  day  to  dry,  the  sugar-candy  is 
ready  for  the  market.  It  is  commercially  known  as  of  three  kinds — the  finest,  re- 
fined white,  has  a  large  colourless  crystal ;  yellow  candy,  a  straw-coloured  crystal ;  and 
brown  candy  is  similar  in  colour  to  ordinary  moist  sugar.  In  some  parts  of  France  a 
dark  candy  is  manufactured  under  the  name  of  Sucre  de  Boerhave.  Inferior  cane 
sugar  is  employed  for  the  brown,  boiled  sugar  for  the  yellow,  and  refined  sugar  for 
the  white  candy.  Sugar-candy  is  extensively  used,  the  white  principally  in  preparing 
"  liqueur,"  a  solution  of  candy  in  wine  or  cognac ;  also  in  the  champagne  manufacture, 
and  in  all  cases  where  a  clear  sweetening  solution  is  required  in  large  quantities.  The 
yellow  candy  is  used  for  sweetening  tea  and  coffee  in  restaurants,  and  enters  largely 
into  the  recipes  of  the  pharmaceutist  for  affections  of  the  throat  and  chest,  as  well  as 
for  making  syrups  intended  as  vehicles  for  nauseous  medicines. 

Beet  Treacle. — The  last  residual  syrup  contains  on  an  average  in  100  parts — 

Sugar         . -      v    "'.        50 
Non-sugar  .         .         30 

Water        .        .    •••,.-  •      20 

Of  the  30  parts  which  are  not  sugar,  10  parts  consist  of  mineral  matter,  chiefly 
potassium  salts  (always  including  nitrate) ;  the  remaining  20  parts  comprise  oxalic 
acid  and  betain  combined  with  inorganic  bases,  nitrogenous  matter,  derivatives  and 
decomposition  products  of  albumen,  protoplasm,  cellular  tissue,  &c.  In  consequence 
of  the  offensive  taste  and  smell  of  beet  treacle  it  is  rarely  admissible  as  an  article  of 
human  consumption. 

In  making  up  this  treacle,  the  chief  processes  are  the  osmose,  the  treatment  with 
lime  and  spirit,  or  water,  and  the  strontia  process. 

The  osmose  process  depends  on  diffusion  through  parchment-paper,  and  is  of 
importance,  as  the  treacle  contains  a  number  of  constituents  which  differ  greatly  in 
diffusive  power.  The  saline  matters  diffuse  very  rapidly,  the  saccharose  more  slowly, 
and  the  other  matters  with  great  difficulty  or  not  at  all.  But  the  difference  in  the 
rate  of  diffusion  is  not  sufficient  for  a  direct  method  of  separation.  At  the  commence- 
ment of  the  process  large  quantities  of  the  salts  pass  through  the  parchment-paper  and 
little  saccharose.  Afterwards  the  proportions  are  inverted.  The  osmotic  process  is 
therefore  interrupted  when  a  part  of  the  salt  has  been  removed,  so  that  a  part  of  the 
saccharose  crystallises  out  on  evaporation,  and  the  treacle  whizzed  out  from  the  sugar 
crystals  has  nearly  the  same  composition  as  ordinary  treacle.  This  second  treacle 
is  again  freed  from  salts  osmotically,  until  there  finally  remains  a  treacle  so  con- 
taminated with  colloid  matters  as  not  to  admit  of  further  treatment.  The  yellowish- 
brown  osmotic  water  contains  all  the  diffused  bodies,  salts,  and  varying  quantities  of 
sugar.  It  is  used  in  irrigating  meadows  (for  which  the  presence  of  sugar  renders 
it  questionably  suitable).  The  process  requires  little  initial  outlay.  One  quire  of 
parchment-paper  serves  for  540  kilos,  of  syrup. 

Elution. — This  process,  devised  by  Scheibler  in  1865,  depends  on  the  formation  of 
a  tribasic  calcium  saccharate  and  its  lixiviation  with  alcohol  at  30  per  cent.,  in  which 
the  chief  part  of  the  non-sugar  dissolves,  whilst  a  fairly  pure  saccharate  remains.  The 
difficulty  of  obtaining  a  dry  compound  of  treacle  and  lime  was  overcome  by  Seyferth, 
who  takes  a  concentrated  treacle  at  80°  Tw.  and  mixes  it  with  freshly  burnt 
lime  in  fine  powder.  One  mol.  of  saccharose  in  the  treacle  requires  3  to  4  mols. 


SECT,  vi.]  SUGAR.  709 

quicklime.  The  lime  treacle,  after  lixiviation  with  alcohol,  is  freed  from  alcohol  by 
means  of  steam,  and  then  converted  into  a  sugary  milk  of  lime,  which  is  pumped  into 
large  cisterns  and  run  into  separating  pans.  The  elution-lye  is  worked  up  for  alcohol. 
Elution  yields  about  80  per  cent,  of  the  saccharose  present  in  the  treacle  in  the  state  of 
a  saccharate. 

Substitution  and  Separation. — As  elution  and  similar  processes  consume  much 
alcohol,  Steffen  obtained  by  his  process  a  tolerably  pure  calcium  saccharate  from 
water. 

The  treacle  to  be  worked  up  daily  is  placed  in  tanks  capable  of  containing  water 
equal  in  weight  to  ten  times  the  mass,  and  mixed  with  cream  of  lime  at  54°  Tw.  The 
dilution  with  water  is  so  managed  that  the  solution  gives  a  precipitate  on  heating  to 
100°.  To  the  diluted  treacle  so  much  lime  is  added  as  can  dissolve  in  the  liquid — i.e., 
about  28  parts  of  pure  lime  to  100  parts  of  sugar  in  the  solution.  The  cisterns,  each 
of  which  has  a  capacity  of  20  cubic  metres  for  the  reception  of  10  tons  of  treacle,  are 
fitted  with  agitators.  When  the  lime  has  been  dissolved  for  eight  hours,  the  lye  is 
heated  to  i  jo°,  in  closed  boilers,  by  means  of  steam,  so  that  the  insoluble  sugar-lime 
separates  out,  when  the  entire  contents  of  the  boilers  are  forced  through  filter-presses, 
which  are  so  arranged  that  the  cakes  can  be  lixiviated  with  water  at  110°.  The  cakes 
are  then  wrapped  in  press-cloths  of  ticking,  placed  in  a  hydraulic  press,  and  submitted 
to  a  pressure  of  100-150  atmospheres.  During  filtration  the  lye  must  not  cool  down 
below  1 00°,  and  hence  the  filter- presses  are  heated  with  steam  before  the  admission 
of  the  liquid. 

The  mother  liquor  running  from  the  presses  is  allowed  to  cool,  and  a  quantity  of 
sugar,  corresponding  to  the  sugar-lime  which  has  been  precipitated  again,  is  added  in  the 
state  of  a  saccharated  cream  of  lime.  The  mother  liquor  so  treated  is  stirred  for  three 
hours  at  the  common  temperature  until  the  liquid  is  saturated  with  lime.  The  mother 
liquor  is  then,  by  means  of  substitution,  equal  in  percentages  of  sugar  and  lime  to  the 
original  lye.  The  mother  liquor  is  then  heated  in  the  boilers,  when,  on  the  application 
of  heat,  sugar-lime  again  separates  out,  or  is  filtered  out  and  pressed.  The  quantity  of 
sugar  contained  therein  is  equal  to  the  total  sugar  which  has  been  substituted.  Sub- 
stitution and  precipitation  are  repeated  with  the  same  mother  liquor  twenty  to 
twenty-five  times,  until  it  can  be  no  longer  treated,  owing  to  the  accumulation  of  salts 
arid  non-saccharine  matter.  The  sugar-lime  obtained  is  made  up  in  water  into  a  liquid 
of  14°  Tw.,  and  is  then  further  treated  like  beet- juice. 

For  the  separation  process,  the  treacles,  syrups,  &c.,  are  diluted  with  cold  water  in 
a  cistern  fitted  with  an  agitator.  The  temperature  of  the  solution  must  not  exceed 
35°  Tw.,  and  its  concentration  must  correspond  to  6' 12  per  cent,  of  sugar.  A  certain 
quantity  of  this  cold  solution  is  run  into  a  vessel  fitted  with  an  agitator,  and  to 
every  100  parts  of  sugar  there  are  added,  by  means  of  a  measuring  cylinder,  50-100 
parts  of  ground  lime.  The  whole  is  then  pumped  into  the  so-called  lixiviation  filter- 
presses  in  order  to  remove  any  excess  of  undissolved  lime.  For  100  parts  of  sugar  in 
solution  for  medium  qualities  of  lime,  and  at  temperatures  below  35°,  65  parts  of  lime 
are  mostly  sufficient  to  separate  the  sugar.  When  the  lime  has  been  stirred  in  for  a 
short  time  the  sugar  is  deposited.  The  paste  is  pumped  into  a  second  group  of  lixiviation 
filter-presses,  which  separate  the  sugar-lime  from  the  liquid.  This  liquid,  which 
contains  but  little  sugar,  and  almost  all  the  non-sugar,  is  either  run  off  as  a  waste 
liquor  or  the  same  process  is  repeated  a  second  time.  To  remove  the  liquid  still 
adhering  to  the  sugar-lime,  it  is  purified  with  cold  water  in  the  filter-presses.  The 
sugar-lime  cakes  are  taken  out  of  the  press,  ground  up  in  a  wet  mill  with  beet-juice 
and  solutions  of  sugar  or  water,  and  the  sugar  then  separated  from  the  lime. 

Fig.  492  may  serve  to  elucidate  the  entire  process.  Into  the  so-called  cool- 
masher,  Ay  which  serves  for  forming  and  precipitating  the  sugar-lime,  the  treacle  from 


710 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


the  measuring  vessel  is  put,  whilst  the  washing  liquor  of  the  sugar-lime  presses  flows 
in  from  the  cistern,  C.  The  lime,  which  has  passed  through  a  wire  sieve  with  2000 
meshes  per  square  centimetre,  passes  through  the  measuring  vessel,  D,  generally  made 
as  a  drum  with  four  wings,  so  that  the  space  between  the  wings  contains  4  kilos,  of 

lime  dust. 

Fig.  492. 


Fig.  493- 


Fig.  494. 


The  cooling-masher  shown  in 
Figs.  493  and  494,  is  one-fiftieth  of 
its  real  size,  consists  of  a  cylinder, 
with  the  tubes,  r,  inserted,  which 
are  surrounded  by  cold  water  in 
the  direction  from  a  towards  5.  The 
shaft,  c,  in  the  interior  wide  tube, 
carries  the  wings,  d,  and  the  mixing 
screw,  e.  The  treacle  is  run  in  by  the 
tube  /,  the  lime  by  the  tube  g,  the 
water,  or  the  washings,  by  the  pieces, 
k,  into  the  worms,  I.  These  are  pro- 
vided with  fine  apertures,  from  which 
the  liquid  passes  down.  The  lime 
treacle  formed  is  let  off  by  the  valve, 
in.  The  apparatus  is  fitted  with 
man-holes,  n ;  eye-glasses,  o  ;  ther- 
mometers, t;  air-pipe,  q  ;  short  pieces,. 
s,  for  cleaning  the  eye-glasses ;  and 
a  trial-cock,  s.  The  treacle,  as  al- 
ready mentioned,  is  diluted  with 
water  so  as  to  form  25  hectolitres 
of  liquor,  containing  about  7  per 
cent,  of  sugar.  It  is  then  cooled 
as  far  as  possible  by  letting  in  the 

cooling  water  and  putting  the  agitating  screw,  e,  in  action.  The  lime-dust  is  then 
gradually  added.  The  cooling  water,  six  times  the  weight  of  the  treacle,  enters 
at  8°  and  escapes  at  12°.  The  entire  contents  of  the  cooling-masher  are  forced 
through  the  filter-presses,  E,  by  a  pump  at  P.  From  these  there  first  flows  off  a  lye 
which  contains  scarcely  any  sugar  (polarising  only  0-5  to  o-6),  and  is,  therefore,  at  once? 


SECT.    VI.] 


SUOAR. 


711 


allowed  to  flow  off.  As  the  saccharate  has  a  granular  crystalline  texture,  it  can  be 
washed  in  the  same  presses  with  cold  water,  in  which  it  is  almost  insoluble. 

The  washings  are  also  allowed  to  flow  away,  but  that  finally  obtained  is  used  to 
dilute  the  treacle,  and  it  is  for  the  present  collected  in  the  cisterns,  F.  The  saccharate 
from  the  filter-presses  is  a  white,  sandy  mass,  and  it  is  converted  in  the  sugar-lime  mill, 
G,  into  sugary  milk  of  lime,  and  forced  by  the  montejus,  JOT,  into  the  cistern,  J,  where 
it  stands  ready  for  further  use. 

The  sugar-lime  mill  is  shown  in  Figs.  495,  496,  and  497  at  one-fiftieth  of  its  actual 
size.  The  spiral,  a,  which  lies  below  the  filter  presses,  moves  the  sugar-lime  into  the 
body,  b,  which  lies  above  the  guiding  piece.  If  a  diluting  liquid  is  used,  it  enters 
ate.  The  guiding-piece  is  constructed  after  the  manner  of  coffee-mills.  A  conical  toothed 


Fig.  495. 


Fig.  496. 


disc,  d,  is  fixed  on  a  vertical  shaft,  e,  the  track  of  which  can  be  raised  by  the  lever,  g,  so 
that  the  teeth  of  the  disc,  d,  can  be  set  exactly  opposite  those  of  the  edge,  h.  The 
ground  product  falls  into  the  horizontal  mash- drum,  i  ;  is  here  well  worked  through,  and 
is  drawn  off  at  k  as  ready  milk  of  lime.  If  only  so  much  treacle  is  worked  up  that  the 
lime  in  the  saccharine  milk  of  lime  can  be  entirely  used  for  separation  in  the  sugar 
vats,  the  saccharate  is  immediately  mixed  with  beet-juice  in  the  mill.  But  if  the  lime 
would  be  too  much,  a  part  of  it  has  first  to  be  removed.  It  is  mashed,  therefore,  in 
the  mill  with  the  thin  juice,  or  with  the  juice  of  the  first  saturation.  The  excess  of 
lime,  two  thirds  of  that  originally  combined  with  the  sugar,  is  separated  out  in  filter- 
presses,  and  the  solution,  which  now  contains  25  to  30  of  lime  to  100  of  sugar,  is  then 
passed  on  to  saturation. 

The  Strontia  Process. — Dubrunfaut  proposed,  as  far  back  as  1849,  ^°  separate  sugar 
out  of  treacle  by  means  of  strontia  or  baryta,  and  in  1863  Stammer  showed  that,  on 
woi-king  up  treacle  by  means  of  strontia,  a  much  purer  product  was  obtained  than  with 
lime.  He  considered  the  process  as  impracticable  on  account  of  the  difficulty  of  pro- 
curing strontia.  Meantime  the  Dessau  sugar  refinery  used  strontianite  with  success, 
though  the  details  of  the  process  were  unknown.  The  process  has  recently  been 
developed  by  Scheibler. 

The  treacle  is  intimately  mixed  with  a  hot  saturated  solution  of  strontia ;  the  mixture 
passes  through  a  cooling  apparatus  a,nd  arrives  at  the  crystallisers,  where,  after  the 
addition,  if  necessary,  of  a  little  strontium  non-saccharate  to  induce  crystallisation,  it 
congeals  completely  to  mono-strontium  sugar,  C13H,2OuSr0.5H2O.  The  congealed 
mass  is  then  again  liquefied  by  agitation  and  passed  through  the  filter-presses,  when  it 
is  resolved  into  A,  non-strontium  sugar,  and  B,  sacchariferous  lye. 

The  worked,  white  saccharate  cakes,  A,  from  the  filter-presses  are  mashed  up  with 


7i2  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

water  or  beet-juice,  and  saturated  with  water  only  so  far  that  there  remains  an 
alkalinity  of  0^04  or  o-o6  SrO.  The  precipitated  strontium  carbonate  is  then  sepa- 
rated from  the  solution  of  sugar  by  filter-presses ;  the  white  mud  of  SrC03  is  made  up 
into  bricks  for  the  oven,  whilst  the  filtered  sugar-juice  undergoes  a  second  saturation 
in  order  to  be  entirely  freed  from  SrO.  It  is  boiled  up  and  filtered  again  in  order  to 
separate  the  white  SrC03  mud  from  the  pure  solution  of  sugar.  The  press  mud  goes 
to  the  brick-pressing  machine,  whilst  the  thin  juice  obtained  is  worked  up  after  fil  • 
tration  to  filling  mass  in  the  ordinary  manner,  or  prior  to  filtration  it  is  mixed  with 
separated  and  saturated  thin  juice,  in  order  to  be  worked  up  together. 

The  above-mentioned  saccharine-lye,  JB,  is  mixed  up  with  the  required  quantity  of 
caustic  strontia,  and  boiled ;  the  sugar  is  separated  out  as  bi-strontium  sugar  in  the 
form  of  a  dense  precipitate,  which  rapidly  subsides.  The  precipitate  and  the  lye  are 
most  easily  separated  from  each  other  by  settling  ;  the  former  serves  at  once  for 
mixing  with  treacle  in  order  to  form  mono-saccharate,  whilst  the  latter  is  passed  into 
special  large  cisterns,  in  which  it  cools  and  deposits  the  excess  of  the  dissolved  strontium 
salt,  Sr(OH)2.8H20,  in  the  form  of  yellow  crystals.  After  standing  for  two  or 
three  days,  the  yellow  salt  is  separated  from  the  lye  ;  the  salt  is  again  used  for  forming 
mono-saccharate  or  bi-strontium  sugar,  whilst  the  brown  lye,  free  from  sugar,  is  saturated 
with  carbonic  acid  in  presence  of  an  alkaline  carbonate,  and  all  the  strontia  is  thrown 
down  as  a  strontium  carbonate.  The  brown  product  thus  obtained  goes  to  the  brick- 
pressing  machine,  and  the  final  lye  (containing  no  sugar)  is  used  as  a  manure.  Caustic 
strontia  is  obtained  by  igniting  strontium  carbonate.  Both  the  commercial  strontia 
and  that  recovered  by  the  above  process  are  dried,  pressed  into  bricks,  and,  after 
thorough  drying,  ignited  in  the  furnace. 

Palm  Sugar,  Maple  Sugar,  and  Sorghum  Sugar  are  of  no  importance  so  far  as 
Europe  is  concerned.  There  are  produced  yearly  about  12,000  tons  of  palm  sugar, 
2  500  tons  of  maple  sugar  (in  the  United  States  and  the  Dominion),  and  3000  tons  of 
Sorghum  sugar.  The  cane  and  the  beet  yield  each  from  two  to  two  and  a  half  million 
tons. 

FERMENTATION  ARTS. 

Fermentation  and  Yeast. — Fermentation  is  a  term  applied  to  the  peculiar  changes 
of  complex  organic  substances  of  the  amylaceous  and  saccharine  type  under  the  influence 
of  certain  putrescible  nitrogenous  substances  or  ferments.  The  decomposition  of  fer- 
mentable organic  bodies  by  a  ferment  effects  the  separation  of  their  constituents  into 
two  or  more  combinations,  as  when  by  a  yeast-ferment  dextrose  and  levulose  are 
converted  into  alcohol,  its  homologues,  and  carbonic  and  succinic  acids ;  or  the  molecules 
of  the  original  substance  are  re-grouped,  as  in  the  conversion  of  sugar  of  milk  into 
lactic  acid  during  lactic-acid  fermentation ;  finally,  the  elements  of  the  organic  sub- 
stance may  enter  into  combination  with  the  oxygen  of  the  atmosphere  either  to  form 
new  organic  combinations,  or  to  separate  into  its  inorganic  constituents  carbonic  acid, 
carburetted  hydrogen,  &c.  This  latter  decomposition  is  termed  mouldering  when  a 
residue  rich  in  carbon  (humus)  remains,  but  when  only  the  mineral  constituents 
remain,  decay  is  said  to  have  been  reached.  These  terms  are  thus  defined  more  by 
custom  or  usage  than  by  direct  etymology — dictionaries  hardly  distinguish  between 
them,  but  the  difference  is  known  to  all.  If  large  quantities  of  water  be  present  both 
these  processes  are  resolved  into  putrefaction,  in  which  chiefly  gases— carbonic  acid, 
ammonia,  sulphuretted  hydrogen  — and  water  are  disengaged.  But  fermentation 
always  results  in  the  remaining  or  the  formation  of  other  organic  compounds,  and  the 
variety  of  fermentation  set  up  mostly  depends  on  the  state  of  decomposition  of  the 
azotised  matter  employed  as  a  ferment.  The  most  important  ferment  is  undoubtedly 
yeast,  but  the  ferment  may  be  either  an  organic  substance  (yeast)  or  a  protein  body  in 


SECT,  vi.]  FERMENTATION  ARTS.  713 

a  putrescent  state — it  is  always  a  nitrogenised  body.     In  a  technological  work  the 
varieties  of  fermentation  may  be  classed  as — 

1.  Vinous  or  alcoholic  fermentation,  including  the  changes  observed  during  the 

processes  of  wine  making,  beer  brewing,  and  the  production  of  alcoholic 
liquors  or  spirits. 

2.  Lactic-acid  fermentation,  taking  place  during  the  souring  of  milk;  and  at  a 

higher  temperature  changing  to 

3.  Butyric-acid  fermentation. 

To  these  fermentations  may  be  added — 

4.  Putrescence,  noticeable  only  in  technological  chemistry  as  a  stage  to  be  most 

carefully  avoided. 

Vinous  Fermentation. — Vinous  or  alcoholic  fermentation  is  the  result  of  the  decom- 
position of  saccharine  matter,  dextrose  or  glucose,  levulose  or  chylariose,  and  lactose 
into  several  products,  principally  alcohol  and  carbonic  acid.  According  to  the  recent 
researches  of  Lermer  and  Von  Liebig  (1870),  dextrine  in  the  presence  of  sugar  is  con- 
verted into  equal  parts  of  alcohol  and  carbonic  acid. 

Dextrose,  according  to  the  equation  C6H1S06  =  2C2H60  +  zCO,,  yields  5 1  •  i  per 
cent,  alcohol  and  48-p  carbonic  acid,  saccharine,  and  maltose — 

CUHM0U    +    H,0    =    4C,H60    +    4C02. 
In  the  latter  process  132,000  heat-units  are  liberated,  or  720  per  kilo,  of  alcohol. 

Recently  Pasteur  has  shown  that  lactic  acid  does  not  result  from  alcoholic  fermen- 
tation, but  that  succinic  acid  is  a  constant  product  of  this  fermentation  in  quantities 
never  less  than  o'6  to  0*7  per  cent,  of  the  weight  of  the  sugar  employed.  Glycerine  is 
another  constant  production  to  the  extent  of  3  per  cent,  of  the  sugar;  this  substance 
occurs  in  all  wines.  The  5  to  6  per  cent,  of  substances  remaining  may  therefore  be 
thus  divided : — 

Succinic  acid      ....  o'6  to  0*7 

Glycerine    .        .        .        .      :..  3^2  to  y6 

Carbonic  acid      ....  o'6  to  0*7 

Cellulose,  fatty  substances,  &c.  j'2  to  i'5 

5-6  to  6-5 

Yeast. — The  nature  of  alcoholic  fermentation  was  first  investigated  by  Cagniard- 
Latour,  while  our  present  knowledge  is  due  chiefly  to  the  researches  of  A.  de  Bary, 
J.Wiesner,  Hoffman,  Bail,  Berkley,  Pasteur,  Hallier,  Bechamp,  and  Leriner.  Yeast  on 
being  introduced  into  a  fermentable  fluid  rapidly  throws  out  fermenting  arms,  as  it 
were,  until  the  fluid  is  covered  with  a  superficial  ferment,  termed  in  German  the 
Oberhefe,  while  at  the  bottom  of  the  vessel  a  viscid  sediment  is  deposited,  known  in 
German  as  the  Unterhefe.  The  oberhefe,  or  superficial  ferment,  is  employed  as  barm 
by  the  baker,  for  the  purpose  of  leavening  his  bread ;  while  the  unterhefe,  or  sedi- 
mentary ferment,  is  that  employed  in  the  fermentation  of  wines  and  of  Bavarian  beers ; 
these  beers  differ  from  the  general  beers  of  England,  France,  and  Germany  in  not 
souring  by  exposure  to  air,  this  quality  being  due  to  the  peculiarity  in  the  process  of 
fermentation,  Untergaehrung,  or  fermenting  from  below,  during  which  the  gluten,  the 
substance  absorbing  the  oxygen  of  the  air,  is  removed.  In  the  distillation  of  brandy, 
the  yeast  employed  is  a  mixture  of  barm  and  bottom  yeast,  as  the  terms  run  in  this 
country.  Fresh  yeast  appears  as  a  grey-yellow  or  red  froth  of  strong  odour,  and  with 
an  acid  reaction.  Under  the  microscope  the  two  kinds  of  yeast  are  easily  distinguished. 
The  superficial  yeast  or  barm  consists  of  globular  or  ellipsoidal  cells  of  equal  size,  and 
about  o-o  i  millimetre  diameter.  They  float  in  the  fluid  partly  alone,  partly  in  groups. 
The  walls  of  the  cells  are  so  transparent  that  the  inner  cells  can  be  seen  through  the 
upper.  In  the  centre  of  each  cell  appears  a  dark  speck  or  grain,  the  protoplasma, 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


Fig.  498. 


sometimes  consisting  of  more  than  i  grain.  The  bottom  yeast,  or  sedimentary  ferment, 
also  consists  of  cells,  but  these  do  not  cling  together  so  tenaciously  as  the  cells  of  the 
barm,  and  are  generally  isolated,  while  the  adhesion  is  merely  mechanical  between  those 
that  do  cling  together,  a  slight  concussion  being  sufficient  to  effect  their  separation. 
Sometimes  a  large  cell  of  the  bottom  yeast  contains  two,  three,  or  even  four  smaller 
cells,  the  dimensions  of  these  cells  varying  greatly,  and  not  being  nearly  so  constant  as 
in  the  cells  of  the  barm. 

E.  C.  Hansen  distinguishes  six  kinds  of  yeast ;  the  more  important  are  Saccharomyces 
.cerevisice  /.,  the  ordinary  beer  ferment.  It  is  a  powerful  form  of  a  top  yeast.  The 
cells  (Fig.  498)  are  greyish,  both  by  reflected  and  by  transmitted  light,  and  more  or  less 

globular.  The  size  of  the  cells  varies  from 
2\  to  6  micromillimetres.  There  are  generally 
found  in  each  mother  cell  one  to  four,  or  very 
exceptionally,  five  cells  (49 8,  6).  The  cell  walls 
of  the  spaces  are  generally  more  distinct 
than  in  the  other  kinds.  Fig.  498,  c,  shows 
cells  with  undeveloped  askospores.  Fig.  498, 
a,  is  a  peculiar  form  of  development  which 
often  occurs.  The  cells  are  divided  by  par- 
tition walls  into  several  parts,  each  of  which 
can  send  out  growths. 

Saccharomyces   pastorianus  1.  is  a  yeast 
which  Hansen  has  often  collected  in  the  air 

of  a  brewery  at  Copenhagen.  If  cultivated  in  wort  it  occasions  bottom  fermentation.  The 
askospores  (Fig.  499)  have  in  general  the  diameter  of  1-5  to  3-5  micromillimetres. 
There  are  commonly  one  to  four  askospores  in  each  cell,  but  sometimes  as  many  as 
ten  (Fig.  499,  6). 

Saccharomyces  ellipsoideus  I.  (Fig.  500)  was  collected  in  the  Vosges  on  ripe  grapes. 
It  is  the  ordinary  ferment  of  wines. 

Fig.  499. 


An  important  step  in  the  fermentation  industries  is'  the  obtaining  and  utilisation  of 
pure  cultures  by  Hansen. 

The  moist  chamber  used  is  shown  in  section  on  a  reduced  scale,  Fig.  501.  The 
cultivation  is  carried  on  on  the  lower  side,  6,  of  the  covering  glass,  a  :  c  is  the  side  of  the 
chamber  and  c?  is  a  stratum  of  water  at  the  bottom  to  prevent  desiccation.  All  these 
objects  must  be  passed  through  a  gas  or  spirit  flame,  or,  preferably,  wrapped  in  several 


SECT.  vi. j  FERMENTATION  ARTS.  715 

folds  of  filter-paper  and  sterilised  by  two  hours'  exposure  to  the  temperature  of  150°  in 
an  oven.  The  upper  edge  of  the  sides  must  be  covered  with  vaseline.  A  water  bath 
heated  to  3O°-35°  is  kept  ready  ;  also  a  stand  upon  which  is  set  a  Chamber-land  flask  (Fig. 
502).  Two  such  flasks  are  required,  each  holding  about  30  c.c.,  half  full  of  nutrient 
gelatine.  Their  outer  surfaces  are  passed  through  the  flame,  and 
they  are  then  set  under  a  bell  till  they  are  wanted  for  use.  They 
are  fitted  with  ground-glass  caps  drawn  out  to  a  slender  tube, 
which  is  filled  with  sterilised  cotton.  A  5  per  cent,  solution  of 
gelatine  in  clear  hopped  wort  is  taken  as  nutrient  solution. 

For  the  propagation  of  pure  cultures,  the  flasks  which  contain 
the  nutrient  gelatine  are  cautiously  heated  until  their  contents 
are  liquid,  when  they  are  placed  in  the  water-bath.  For  pure 
cultivations  young  cells  are  taken  in  vigorous  vegetation.  A  small 
number  of  them  are  diluted  in  the  flask  with  sterilised  water 
until  it  becomes  slightly  dull ;  the  flask  is  shaken  in  order  that 
the  cells  may  be  uniformly  distributed ;  a  few  drops  are  taken 
out  with  a  glass  rod  and  examined  under  the  microscope.  A  low 
power  is  used,  so  as  to  just  distinguish  the  cells  from  other  small 
accompanying  bodies.  The  purpose  of  this  first  microscopic  ex- 
amination is  to  estimate  the  quantity  of  cells  in  the  mixture.  After  it  has  been  well 
shaken  up,  an  ignited  platinum  wire  is  dipped  into  the  liquid  and  quickly  inserted  into 
one  of  the  flasks  containing  nutrient  gelatine.  The  temperature  of  the  gelatine  must 
not  exceed  35° ;  it  is  sufficient,  if  kept  liquid,  and  the  microscopic  examination  shows 
that  the  mixture  is  rich  in  cells,  for  the  platinum  wire  to  be  plunged  in  only  to  the 
depth  of  2  millimetres  ;  in  the  opposite  case  it  is  plunged  in  more  deeply. 

For  greater  safety  two  preparations  are  made;  if  both  give  the  same  result, 
it  may  be  assumed  that  the  cells  are  uniformly  distributed,  and  that  average  speci- 
mens have  been  obtained.  It  must  next  be  determined  whether  the  gelatine  has 
received  a  sufficient  number  of  cells  or  not.  If  a  considerable  error  is  committed  in 
this  respect  all  further  work  is  in  vain.  In  order  that  the  cells  may  be  so  distributed 
in  the  gelatine  that  pure  colonies  may  be  obtained  with  certainty,  the  colonies  which  are 
afterwards  formed  must  have  room  enough  not  to  intermingle  with  each  other.  Such 
drops,  in  shape  and  size  as  are  to  be  afterwards  used,  are  placed  upon  an  ordinary  glass 
slip,  or,  preferably,  on  a  slip  where  a  number  of  squares  have  been  marked  with  a  diamond. 
The  squares  give  a  guide  for  the  microscopic  examination.  If  it  appears  that  too  few  or 
too  many  cells  have  been  sown,  more  cells  must  be  added  in  the  first  case,  and  in  the  latter 
more  gelatine,  all  being  calculated  beforehand.  If  we  find  that  the  mixture  contains 
twice  as  many  cells  as  was  intended,  the  right  point  is  reached  by  adding  as  much 
more  gelatine  as  is  already  present.  A  corresponding  portion  must  be  at  once  placed  upon 
the  glass  covers,  which  are  immediately  covered  with  a  little  glass  bell.  As  a  matter  of 
course,  the  gelatines  must  be  kept  liquid  in  the  water  bath  ;  the  cells  must  be  distributed 
by  shaking,  avoiding  the  formation  of  foam.  At  the  ordinary  temperature  of  a  room 
the  gelatines  coagulate  in  a  quarter  of  an  hour.  As  soon  as  the  gelatine  is  coagulated, 
the  covering  glass  is  fixed  to  the  ring  in  such  a  manner  that  the  cultivation  is  down- 
wards. By  a  cautious  pressure  on  those  points  of  the  glass  which  touch  the  ring  the 
chamber  is  quite  shut  off  from  the  outer  air.  When  the  chambers  are  in  order  they  are 
examined  with  a  low  power.  It  must  be  ascertained  whether  the  spots  of  vegetation 
are  pure — i.e.,  whether  each  proceeds  from  a  single  cell.  The  operations  up  to  this 
point  engage  an  investigator  of  some  experience  for  three  hours.  The  moist  chambers 
are  then  placed  in  a  thermostat  at  24°-25°.  If  there  is  a  microscope  in  reserve,  a 
chamber  may  be  secured  to  its  stage  in  such  a  manner  that  the  cell  in  question  can  be 
accurately  seen  and  its  development  followed  step  by  step.  Spots  of  vegetation,  visible 


7i6  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

to  the  naked  eye,  develop  in  two  or  three  days.  In  the  Saccharomycetes  the  vegeta- 
tive spots  have  the  appearance  of  minute  pin-heads  and  a  pale  yellowish-grey  colour ; 
the  surface  may  be  either  dull  or  slightly  shining  :  the  margin,  under  a  low  power, 
appears  sharply  bounded  or  uneven.  The  colonies  of  Mycoderma  vini  and  M.  cerivisice 
and  some  kindred  species  are  of  a  pale  grey,  with  a  dead  surface,  spread  out  like  a  film 
and  hollowed  like  a  capsule.  As  long  as  they  are  covered  with  gelatine  they  resemble 
the  spots  of  the  Saccharomycetes.  In  the  gelatine  film  of  a  single  covering  glass  sixty 
spots  of  vegetation  may  be  developed.  When  the  pure  cultivations  are  transferred  to 
the  nutritive  liquid  the  air  must  be  pure  and  calm,  and  the  apparatus  must  be 
thoroughly  sterilised.  A  pair  of  small  forceps  and  platinum  wires,  which  have  been 
passed  through  the  flame,  must  be  at  hand,  and  a  sufficient  number  of  small  bells  with 
their  glass  plates.  For  culture  in  a  nutrient  liquid,  Pasteur's  two-necked  flask  is 
generally  used  (|  litre,  Fig.  503)  and  hopped  sterilised  wort.  The  thin  tube  is  closed 
at  its  end  with  an  asbestos  plug ;  to  the  straight  tube  is  attached  a  piece  of  flexible 

tubing  closed  with  a  glass  stopper.     If  a  pure  culture 
Fig-  5°3-  of  a  single  species  is  desired,  four  or  five  of  such  flasks 

are  needed.  This  number  is  to  enable  the  observer  to 
compare  the  vegetations  developed  in  the  flasks  and 
ascertain  whether  he  has  obtained  a  growth  of  the  cells 
which  have  been  sown.  It  may  accidentally  occur  that 
one  of  the  flasks  has  been  infected  by  a  foreign  organism, 
or  no  vegetation  at  all  may  be  developed — e.g.,  if  the 
platinum  wire  was  too  hot.  The  chambers  are  examined 
with  the  microscope ;  the  vegetations,  the  origin  of 
which  has  been  ascertained,  are  scrutinised  so  that  we 
may  be  sure  that  the  colonies  arise  each  from  a  single 
cell.  The  boundaries  of  the  selected  colonies  are  marked 
out  with  a  fine  brush  and  a  little  white  colour.  A 
covering  glass  is  then  lifted  off  its  ring,  and  turned  up- 
side down,  so  that  the  spots  are  upwards  and  placed,  if  possible,  on  a  dark  back- 
ground, that  they  may  be  seen  more  distinctly.  By  means  of  a  forceps  we  lift  up  a 
platinum  thread,  and,  after  drawing  it  rapidly  through  a  gas  or  spirit  flame,  the 
selected  spots  are  touched  with  it.  If  several  specimens  are  to  be  taken  from  the 
covering  glass,  it  must  of  course  be  covered  each  time  with  a  small  bell.  The  operator, 
with  his  left  hand,  removes  the  flexible  tube  of  the  Pasteur  flask,  and  brings  at  the 
same  moment,  with  the  other  hand,  the  infected  platinum  wire  to  the  opening  of  the 
tube,  into  which  it  is  let  fall.  The  tube  is  now  inclined  so  far  that  the  liquid  does 
not  run  out,  and  at  the  same  time  it  is  passed  through  the  fire  and  again  covered 
with  the  caoutchouc  tube.  The  flasks  are  placed  in  a  heat  of  25°-28°.  In  the  course 
of  one  or  two  days  there  is  a  Avell-marked  development.  If  every  foreign  infection  has 
been  avoided  on  transferring  the  cells  to  the  flasks,  each  flask  contains  a  pure  cultiva- 
tion. A  specimen  is  taken  from  each  with  due  precautions  and  examined  with  the 
microscope. 

In  order  to  obtain  larger  quantities  of  pure  yeast,  the  receiver,  C  (Fig.  504),  fitted 
with  a  safety  valve,  <?,  and  a  pressure  gauge,  r,  is  filled  with  air  to  a  pressure  of  3  to 
4  atmospheres  by  means  of  the  air-pump,  t  u,  and  the  pipe  s.  The  wort  cylinder, 
A,  provided  with  a  trial  cock,y*,  is  sterilised  with  steam  under  pressure,  when  the  air 
escapes  through  the  tube,  b,  and  air  is  admitted  in  its  place  through  the  cock  g,  and 
the  cotton  filter,  d.  The  wort  is  conveyed  in  a  boiling  condition  into  the  cylinder  from 
the  main  pipe  of  the  boiling-house.  Cooling  is  effected  by  water  trickling  out  of  the 
ring,  e  ;  the  air  needed  for  aeration  is  let  pass  through  the  filter  d.  The  fermentation 
cylinder,  B,  is  sterilised  in  the  same  manner  as  the  wort  cylinder.  It  has  a  similar 


SECT.    VI.] 


FERMENTATION  ARTS. 


717 


Fig.  504. 


filter,  k  ;  a  glass  tube,  o,  in  order  to  observe  the  level  of  the  liquid ;  a  tube,  i  h,  for  the 
escape  of  carbonic  acid ;  an  agitator, 
k,  in  order  to  mix  the  yeast  with 
the  liquid  ;  a  small  tube,  I,  for  introdu- 
cing pure  yeast  and  for  taking  small 
samples. 

The  yeast  is  added  only  once,  and 
the  apparatus  then  works  for  a  year, 
or  longer  if  required.  The  outflow 
cock,  m,  is  so  arranged  that  the  liquid 
itself  effects  the  purification,  and  no 
infection  from  without  can  take  place, 
but  high  tension  must  always  be  kept 
up.  The  wort  is  passed  into  the  fer- 
mentation cylinder  through  the  piping, 
a  n,  which  connects  both  cylinders. 
As  soon  as  it  comes  near  the  yeast 
tube,  I,  the  pipe  is  closed  until  the  yeast  is  added  ;  it  is  then  filled  up  to  the  mark  in  the 
upper  part  of  the  glass  tube;  it  is  stirred,  and  220  litres  of  sterilised  wort  are  thus 
brought  into  fermentation  with  absolutely  pure  yeast.  In  about  ten  days  the  beer 
is  drawn  off  through  the  cock  m.  During  tapping,  air  is  let  enter  through  the 
filter  h.  As  soon  as  any  mud  appears  the  running  is  stopped,  wort  is  added,  stirred 
up,  and  27  litres  are  taken  out  of  this  mixture  of  wort  and  yeast.  Wort  is  added 
afresh,  stirred  again,  and  27  litres  are  taken  of  this  last  mixture.  The  measures 
are  shown  by  a  graduation  on  the  glass  tube,  o.  In  the  54  litres  taken  out  there 
is  yeast  enough  to  set  8  hectolitres  of  wort  in  fermentation ;  the  yeast  remaining  in 
the  cylinder  is  enough  to  bring  again  220  litres  into  fermentation,  and  so  it  goes  on 
continuously. 

Nageli  and  Low  (1878)  found  in  the  bottom  yeast  of  beer  (with  nearly  8  per  cent, 
of  nitrogen) — 

Cellulose  and  vegetable  mucus  .         .        .   :     .-        37  per  cent. 

Proteines  :  «.  Common  albumen        .        i        .:        36 
1).    Gluten  casein  albumen        .         .          9 

Peptones  (precipitable  by  basic  lead  acetate)    .  2 

Fat '5 

Ash 7 

Extractive  matter,  &c 4 

Top  yeast  contains  2*5  per  cent,  and  bottom  yeast  up  to  7  per  cent,  of  ash.  The 
proportion  of  sulphur  averages  0*5  to  o'8  per  cent.  The  ash  of  the  yeast  consists 
chiefly  of  potassa,  phosphoric  acid,  silica,  and  magnesia. 

Physiologists  are  not  agreed  as  to  the  part  played  by  yeast  in  alcoholic  fermenta- 
tion. If  the  yeast  is  to  act  upon  another  substance,  there  must  be  interpenetration. 
As  the  yeast  is  enclosed  in  a  cell-membrane,  the  substances  upon  which  the  yeast  is  to 
act  must  penetrate  this  membrane,  i.e.,  must  be  capable  of  diffusion.  Hence  malt  is 
required  in  the  mashing  process  in  order  to  split  up  the  starch  into  maltose  and 
dextrine,  the  former  of  which  is  able  to  penetrate  through  the  cellular  membranes  of 
the  yeast.  It  is  not  sufficient  for  a  complete  conversion  of  the  maltose  into  alcohol  to 
carry  out  the  process  of  saccharification,  namely,  at  a  suitable  temperature.  For  a  good 
fermentation,  such  as  is  required  in  the  distilling  business,  the  subsequent  action  of 
diastase  is  needed,  whereby  the  dextrine,  which  is  not  diffusible,  is  gradually  converted 
into  maltose,  and  penetrates  into  the  yeast  cell.  The  thinner  the  membrane  the  better 
the  diffusion.  Old  yeast  is  harder  to  nourish  than  young  yeast,  as  in  the  former  the 
membrane  is  thicker.  The  albuminoids  are  converted  by  the  action  of  the  peptase  of 


7Ig  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

the  malt  into  soluble  and  diffusible  peptones,  and  in  this  state  they  pass  into  the  yeast 
cell.  There  they  become  insoluble  and  are  reconverted  into  albumens.  The  case  is 
similar  with  the  maltose,  which  is  formed  from  the  starch  in  the  mashing  process.  A 
small  part  of  it  is  precipitated  as  cellulose  within  the  yeast  cells ;  but  in  great  part  it  is 
split  up  into  alcohol  and  carbon  dioxide,  which  do  not  form  constituents  of  the  starch. 
A  vigorous,  healthy  yeast  prolongs  its  life  even  if  it  receives  no  fresh  nutriment.  This 
vegetation  of  the  yeast  without  nutrition  is  called  the  self -fermentation  of  the  yeast. 
We  have,  therefore,  to  distinguish  two  stages  in  the  development  of  yeast — i.e.,  (i)  the 
reception  of  nutriment  and  their  use  in  the  production  of  new  cells  ;  (2)  the  katagenesis, 
in  which  the  substance  of  the  yeast  cell  is  decomposed. 

Conditions  of  Alcoholic  or  Vinous  Fermentation. — The  conditions  of  alcoholic 
fermentation  are  the  general  conditions  of  the  vegetation  of  the  yeast  plant,  with  the 
distinction  that  by  vinous  fermentation  the  largest  amount  of  alcohol  is  obtained.  The 
following  conditions  must  be  f  ulBlled  when  alcoholic  fermentation  is  the  desideratum : — 

1.  An  Aqueous  Solution  of  Sugar,  in  the  proportion  of   i  part  of  sugar  to  4  to  10 
parts  of  water.     The  sugar  can  be  employed  as  grape  sugar,  dextrose,  or  levulose,  which 
is  always  capable  of  fermentation  ;  or  an  unfermentable  sugar,  cane  sugar,  or  sugar  of 
milk,  may  be  converted  by  means  of  an  acid  or  suitable  agent  into  fermentable  sugar. 
However  gradual  the  process  may  seem,  cane  sugar  is  always  converted  into  grape 
sugar  before  fermentation  sets  in. 

2.  The  Presence  of  Yeast  or  Spawn. — In  the  first  case,  i  part  of  yeast  to  5  parts 
of  sugar  is  sufficient  to  effect  a  strong  fermentation.     If  spawn  only  is  present,  there 
must  also  be  present  substances  upon  which  the  spawn  may  feed  or  develop — protein 
substances,  phosphoric  acid,  humus,  and  alkalies.     If  no  ferment  exists,  the  only  other 
condition  under  which  fermentation  is  effected  is  by  exposure  to — 

3.  The  Atmosphere,  which  introduces  the  before-mentioned  ferment  and  furnishes  life. 

4.  A  known  Temperature,  the  limits  of  which  are  5°  and  30°  C.     As  a  rule,  vinous 
fermentation  is  effected  between  9°  and  25°.     The  lower  the  temperature  the  longer 
the  time  required  for  the  fermentation  to  subside,  and  conversely.     At  30°,  and  at 
higher    temperatures,    the  vinous    fermentation    easily  goes   over  into  butyric-acid 
fermentation.     The  making  of  wines  is  based  on  a  practical  acquaintance  with  alcoholic 
fermentation ;  but  in  this  case  only  a  portion  of  the  sugar  of  the  must  goes  over  into 
alcohol  and  carbonic  acid.     The  alcohol  remains,  while  the  greater  part  of  the  carbonic 
acid  escapes. 

Yeast,  like  all  plants,  requires  for  its  development  and  increase  the  co-operation  of 
atmospheric  oxygen ;  in  the  absence  of  free  oxygen  yeast  cannot  grow  in  a  nutritive 
solution.  The  assertion  of  Pasteur,  that  yeast  can  obtain  the  oxygen  needed  for  its 
increase  from  oxygenous  compounds  (e.g.,  from  sugar),  is  disputed.  Under  suitable 
conditions  yeast  grows  without  setting  up  fermentation,  and,  on  the  other  hand,  it  is 
established  that  fermentation  occurs  without  the  growth  of  yeast.  The  growth  of 
yeast  and  fermentation  are,  therefore,  not  inseparable.  The  production  of  the  "  seed 
yeast "  must  ensue  with  abundant  access  of  air,  but  the  process  of  fermentation  goes 
on  with  the  completest  possible  exclusion  of  air. 

Pressed  Yeast  (Dry  Yeast). — Yeast  may  be  made  in  various  ways.  At  Schiedam 
(Holland)  it  is  made  of  excellent  quality  by  a  mode  which  is  to  a  certain  extent  a  trade 
secret,  and  differs  materially  from  the  following  process  : — A  mash  is  made  in  the 
ordinary  manner  of  i  part  of  bruised  barley  malt  with  3  parts  of  bruised  rye,  the 
mash  being  cooled  with  the  fluid  portion  of  the  wash.  To  100  kilos,  of  the  bruised 
grain  is  added  0-5  kilo,  of  sodium  carbonate  and  0-35  kilo,  of  sulphuric  acid  diluted 
with  water ;  these  ingredients  having  been  added  to  the  mash,  it  is  brought  to  fermenta- 
tion by  the  aid  of  yeast.  The  newly  formed  yeast  is  removed  from  the  strongly 
fermenting  fluid  by  the  aid  of  perforated  ladles ;  it  is  then  strained  through  a  linen 
cloth  or  fine  sieve,  and  poured  into  cold  water,  wherein  it  is  allowed  to  form  a  sediment. 


SECT.  vi. J  WINE  MAKING.  719 

The  sediment  thus  produced  is  collected  after  the  supernatant  water  has  been  run  off, 
is  placed  in  a  stout  canvas  bag  under  a  press,  and  formed  into  a  stiff  clayey  dough,  to 
which  usually  4  to  10  (sometimes  as  much  as  24)  per  cent,  of  dry  potato  starch  is 
added.  Sometimes  the  water  is  removed  from  the  yeast  by  placing  that  substance 
upon  slabs  made  of  gypsum  or  other  absorbent  materials,  care  being  taken  to  keep  the 
yeast  in  a  cool  place  ;  by  the  use  of  the  hydro-extractor — expressly  arranged  as  regards 
its  construction  for  this  purpose — yeast  may  be  very  rapidly  rendered  dry.  As  regards 
the  use  of  the  sodium  carbonate,  it  appears  to  assist  in  the  separation  of  the  glutinous 
constituents  of  the  cereals ;  the  action  of  the  sulphuric  acid  is  partly  similar,  and  it  also 
prevents  the  formation  of  lactic  acid,  which,  if  formed,  causes  a  loss  of  both  starch  and 
spirit ;  the  sulphuric  acid  also  accelerates  the  separation  of  the  yeast.  According  to 
communications  by  some  of  the  most  eminent  distillers  at  Schiedam  to  Dr.  G.  J. 
Mulder,  neither  soda  nor  sulphuric  acid  is  used  at  Schiedam  in  the  preparation  of 
what  the  trade  terms  dry  or  German  yeast,  some  of  which  is  imported  into  this 
country  from  Hamburg.  Assuming  the  researches  of  Pasteur  and  others  on  fermenta- 
tion to  be  correct,  these  observations  are  of  great  value  in  reference  to  the  manufacture 
of  yeast.  It  is  found  that  the  yeast  sporulse  become  properly  developed  when  they  are 
placed  in  a  fluid  which,  instead  of  containing  protein  compounds,  consists  of  aqueous 
saline  solutions  mixed  with  a  sugar  solution,  such  as,  for  instance,  ammonium 
tartrate,  potassium  and  magnesium  phosphate,  and  gypsum.  It  would  hence  appear 
that  under  such  conditions  yeast  cells  take  up  the  material  for  the  propagation 
of  new  cells,  partly  from  inorganic  substances,  partly  from  organic,  viz.,  the  decom- 
posing sugar  which  yields  carbonic  acid  :  in  this  respect  the  yeast  cells  agree,  then, 
with  higher  organised  plants.  As  regards  the  quantity  of  yeast  obtainable  from  a 
given  weight  of  materials,  it  may  be  stated  that  from  100  kilos,  of  rye,  including  the 
bruised  malt,  about  15  to  16  kilos,  of  dry  yeast  can  be  obtained.  As  the  quantity  of 
real  yeast  or  of  the  nitrogenous  matter  for  sale  present  in  the  ready  prepared  dry 
yeast  amounts  at  the  most  to  20  per  cent.,  the  nutritive  value  of  the  wash  obtained 
after  the  distilling  off  of  the  spirits  from  the  fermented  liquid  is  but  little  impaired. 

In  testing  yeast  a  portion  is  placed  in  solution  of  sugar,  and  the  carbon  dioxide 
formed  is  determined  gravimetrically  or  volumetrically. 

The  industries  based  on  alcoholic  fermentation  are — 

1.  The  production  of  wine.     The  alcohol  is  not  separated  from  the  fermented 
liquid.     If  the  fermentation  is  suppressed,  a  portion  of  the  carbon  dioxide  formed 
remains  in  solution  and  escapes  with  effervescence  on  the  removal  of  the  pressure 
{champagnes). 

2.  Brewing,  in  which  the  substance  forming  alcohol  is  chiefly  starch.     A  part  of 
it  is  changed  into  non-fermentible  dextrine,  but  the  greater  part  into  maltose,  which 
is  decomposed  on  fermentation.     A  small  part  of   the  sugar  serves   to   keep  up  a 
secondary  fermentation,  which  is  retarded   as   much   as  possible  by  a   reduction  of 
temperature,  whilst  the  gradual  escape  of  carbon  dioxide  contributes  to  the  preservation 
of  the  beer.     Here  also,  as  in  the  case  of  wine,  the  alcohol  is  not  separated  from  the 
fermented  liquid. 

3.  Whilst,  in  brewing,  a  part  only  of  the  starch  used  as  a  raw  material  is  converted 
into  maltose,  and  is  only  by  degrees  transformed  into  alcohol  and  carbon  dioxide,  the 
object  in  a  distillery  is  to  obtain  from  the  given  material  (starch  or  sugar)  in  a  minimum 
of  time  a  maximum  of  alcohol,  which  is  separated  from   the  fermented  liquid  by 
distillation.     The  secondary  fermentation  is  conducted  so  that  the  yeast  destroys  itself. 

WINE  MAKING. 

By  the  name  of  wine  is  generally  distinguished  an  alcoholic  fluid  prepared  with- 
out distillation  by  the  fermentation  of  grape-juice.  In  the  widest  meaning  of  the  term 
is  included  the  result  of  the  vinous  fermentation  of  all  natural  juices. 


720 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


The  Vine  and  its  Cultivation. — The  vine,  Vitis  vinifera,  is  generally  cultivated  in 
Europe  at  a  temperature  of  50°,  while  the  best  and  ripest  drinking  wines  are  obtained 
from  grapes  grown  at  a  temperature  of  51°  to  52°.  It  requires  an  average  tempe- 
rature of  10°  to  11°,  and  an  average  summer  temperature  of  18°  to  20° ;  but  it  is  the 
summer's  sun  that  forms  the  sugar.  A  climate  with  severe  winters  and  hot  summers 
is  therefore  as  favourable  to  the  cultivation  of  the  grape  as  a  temperate  climate. 
England,  with  a  mean  average  annual  temperature  of  11°,  is  consequently  very 
unsuited  to  the  growth  of  the  vine.  The  weather  has  the  greatest  influence  upon 
the  vine  :  during  the  growth  rain  is  required,  but  during  the  ripening  only  the  sun's 
rays  should  reach  the  grape.  The  soil  is  not  so  much  a  matter  of  consequence  if  a 
quantity  of  potash  be  present ;  but  a  warm,  loose  soil  is  the  best. 

Volcanic  soils,  rich  in  potash,  such  as  those  of  the  banks  of  the  Rhine,  of  the  Greek 
islands,  and  of  Southern  Italy,  are  most  suitable  for  the  vine.  The  wines  produced  at 
high  latitudes  on  the  continent  of  Europe,  e.g.,  at  Grlinberg,  in  Silesia,  are  of  a  very 
low  character. 

Besides  serving  for  the  production  of"  wine,  grapes  are  used  for  immediate  consump- 
tion, and  also  dried  in  the  state  of  raisins.  They  are  also  employed  in  the  preparation 
of  (genuine)  grape  sugar,  and  in  the  manufacture  of  cognac,  wine- vinegar,  &c.  An  oil 
is  obtained  from  the  seeds,  and  the  lyes  are  the  principal  raw  material  for  the  manu- 
facture of  tartar  and  tartaric  acid. 

Vintage. — The  sugar  is  found  at  an  early  stage  of  the  growth  of  the  grape.  When 
unripe  the  grape  contains  malic,  citric,  and  tartaric  acids,  potassium  and  calcium  bitar- 
trate,  organic  salts  in  smaller  proportions,  and  a  little  colouring  and  extractive  matter. 
Successive  analyses  have  been  made  of  the  grape  during  its  period  of  growth  by  C. 
Neubauer  from  samples  obtained  from  the  Neroberg,  near  Wiesbaden  (i86S),  and  have 
given  the  following  results : — 


July          27th  . 

August       Qth  . 

I  ;th  . 

„        28th  . 

September  7th  . 

1 7th  . 

„        28th  . 

October      5th  . 

,,        I2th  . 

22nd 


O'6  per«cent.  sugar  and  27  per  cent,  free  acid 


0-9 

2-3 

8-2 

11-9 

18-4 

17-5 
16-9 
18-6 
17-9 


2'9 

2-8 
i-9 

I '2 

0-8 
0-8 
0-9 
0-9 


It  appears  that  the  riper  the  grape  the  more  sugar  it  contains,  and  it  produces  a 
wine  richer  in  alcohol,  so  that  the  grapes  are  never  gathered  until  perfectly  ripe.  The 
grapes  of  the  white  vine  are  of  a  brown-yellow  when  ready  for  gathering  for  wine,  and 
the  red  and  blue  grape  must  be  extremely  dark  before  the  seed  will  separate  from  the 
fleshy  part  of  the  grape  sufficiently  for  wine-making  purposes. 

The  grapes  are  sometimes  plucked,  and  sometimes  left  on  the  stalk.  The  separation 
of  the  grape  from  the  stalk  is  effected  either  by  hand  or  by  the  aid  of  a  hurdle,  the 
openings  between  the  bars  of  which  are  only  sufficiently  wide  to  admit  the  passage  of 
the  grape,  or  by  a  wooden  or  brass  trellis-work,  or  finally  with  a  large  wooden  fork  0*5 
to  0*6  metre  in  length.  The  stalk  contains  much  tannic  acid,  and  it  is  therefore 
necessary  that  all  the  grapes  should  be  thoroughly  separated  before  pressure ;  but  in 
some  cases,  when  the  grape  contains  too  little  of  this  acid,  a  few  stalks  are  purposely 
allowed  to  remain. 

The  Pressing  of  the  Grapes. — After  the  grapes  are  stripped  from  the  stalks,  they  are 
placed  in  a  vat  and  stamped  with  a  wooden  maul  or  pestle  to  express  the  juice.  They  are 
generally  allowed  to  remain  for  some  time,  and  afterwards  submitted  to  a  second  bruis- 


SECT.    VI.] 


WINE  MAKING. 


721 


ing,  the  maceration  being  for  the  purpose  of  softening  the  skins  and  fleshy  part  of  the 
grape.  The  whole  of  the  juice  and  grape-skins,  or  marc,  is  then  put  into  a  butt  with 
perforated  sides,  through  which  the  must  trickles  into  the  fermentation  vat  beneath. 
If  a  white  wine  is  being  operated  upon,  to  prevent  it  becoming  stringy,  as  the  term 
runs,  from  an  insufficient  supply  of  tannic  acid,  small  quantities  of  stalks  are  added 
from  time  to  time.  This  addition  renders  the  wine  more  easily  clarified  by  the  addition 
of  white  of  egg  or  isinglass  in  a  subsequent  stage  of  the  process.  While  the  wine  is  in 
the  vat,  the  fermentation  is  allowed  to  proceed,  and  the  slight  acidity  generated  reacts 
upon  the  colouring  matter  and  aromatic  constituents  of  the  grape,  these  being  taken 
up  in  the  alcohol  set  free. 

The  wine-presses  are  of  very  various  construction.  The  most  general  is  the  beam- 
press,  roughly  constructed  with  a  pole  12  to  16  metres  in  length,  and  four  to  six  oaken 
cross-beams.  These  presses  have  considerable  power,  but  they  are  tedious  to  work,  and 
soon  get  dirty.  The  lever-press  is  more  efficacious,  and  is  made  in  many  forms,  the 
pressure  being  mostly  from  below.  The  hurdle-  or  sledge-press  is  of  the  rudest  kind, 
consisting  merely  of  hurdles  and  rough  heavy  stones.  The  best  presses  are  the  screw- 
presses  made  of  wood  or  cast-iron.  100  parts  of  grapes  yield  60  to  70  parts  of  must. 
The  ripest  grapes  yield  the  first  juice  in  the  press  ;  the  results  of  stronger  pressure  are 
more  acid.  The  result  of  the  first  pressure  is  termed  the  wine  or  the  first  wine  ;  then 
comes  the  press-wines  ;  and  finally  the  after-win.es.  The  residue  or  marc  is  sometimes 
treated  with  water  to  obtain  an  inferior  wine. 

The  Centrifugal  Machine.  —  In  1862  Steinbeis,  of  Stuttgart,  with  the  co-operation 
of  Reihlen,  endeavoured  to  express  the  juice  of  the  grape  with  the  aid  of  the 
centrifugal  machine  instead  of  the  press.  They  were  enabled  in  ten  minutes  to  ex- 
press the  juice  perfectly  from  100  to  120  Ibs.  of  grapes,  including  the  time  required 
to  fill  and  empty  the  machine.  In  1869,  Ballard  and  A  lean  obtained  equally 
successful  results,  some  of  which  were  made  comparative  with  those  obtained  by  a 
good  press  :  — 


Must 
Residue 

Loss 


Centrifugal  Machine. 
.        79'Hi 
.         20-214 
.  0-645 


Press. 
77-086 
18-601 

4-3I3 

lOO'OOO 


Fig-  5°5- 


Ferret  fixes  in  a  vat  six  pillars,  each  of  which  has  six  hooks  pointing  downwards 
(Fig.  505)  at  25  centimetres  apart.  Six  hurdles  made  of  ribs 
placed  6  to  8  centimetres  from  each  other  are  then  put  in  the 
vat  in  such  a  manner  that  as  it  is  filled  they  may  rise  only  so 
far  as  the  hooks  of  the  pillars  allow,  thus  preventing  the  skins, 
stalks,  &c.,  from  ascending.  Upon  the  upper  hurdle  is  laid  a 
thin  layer  of  straw  in  order  to  prevent  any  berries  which  may 
be  carried  up  by  the  motion  of  fermentation  from  ascending  to 
the  top.  When  the  wine  is  drawn  off,  the  hurdles,  with  the 
dregs,  &c.,  between  them,  sink  to  the  bottom.  The  process 
deserves  attention. 

The  Chemical  Constituents  of  the  Must. — Besides  the  stalk 
of  the  grape,  there  are  the  outside  skin,  the  hull,  the  seeds,  and 
the  juice.  Of  the  composition  of  all  these  substances,  with  the 

exception  of  the  grape-juice,  our  knowledge  is  very  deficient.    J    ^^   -   ^ 

Besides  cellulose,  the  stalks  contain  much  tannic  acid,  and  an  acid  very  sour  to  the 
taste.  The  hull  of  th.3  grape  contains  the  colouring  matter  and  a  small  quantity  of 
tannic  acid.  The  seed  contains  a  peculiar  acid,  oenanthic  acid,  and  an  ether,  bearing 
the  same  name,  to  which  the  bouquet  of  the  wine  is  due. 

2  z 


722  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

The  Sugar  of  the  Grape. — The  wine  grape  contains  more  sugar  than  any  other  kind 
of  grape.  The  quantity  of  sugar — a  mixture  of  dextrose  and  levulose — is  seldom  less 
than  12  per  cent.,  while  it  is  sometimes  as  much  as  26  to  30  per  cent.  The  proportion 
of  acid  to  sugar  is  in  good  years  and  in  a  good  grape,  according  to  Fresenius,  i  :  29  ;  in 
average  years  and  cases,  i  :  16  ;  and  when  the  proportion  is  only  i  :  10  the  grapes  are 
useless  for  the  production  of  wine.  The  proportion  between  the  acid  and  sugar  in  wine- 
must  from  the  same  kind  of  grape  for  different  years  is,  according  to  this  eminent 

chemist — 

In  a  very  inferior  year,  1847,  as  i  :  12 
In  a  better  year,  1854,  as  i  :  16 

In  a  good  year,  1848,  as  I  :  24 

During  the  fermentation  of  the  must,  potassium  bitartrate  is  deposited,  and  from 
this  source  most  of  the  tartar  of  commerce  is  obtained.  This  salt  is  insoluble  in  dilute 
alcohol ;  consequently,  as  the  sugar  changes  into  alcohol  it  is  thrown  down.  It  is  from 
the  fact  of  containing  tartaric  acid,  which,  by  combining  to  form  an  insoluble  salt,  is 
thus  prevented  exerting  an  unfavourable  influence  on  the  wine,  that  grapes  possess  so 
much  more  the  property  of  making  a  good  wine  than  do  other  fruits.  The  malic  and 
citric  acids  contained  in  currants  and  gooseberries  cannot  be  withdrawn  in  this  manner. 
Hence  the  addition  of  sugar  to  wines  made  from  these  fruits  to  veil  the  acidity •  the 
addition,  however,  giving  rise  to  the  danger  of  a  second  fermentation,  and  consequent 
acidity.  According  to  Al.  Classen,  i  kilo,  of  ripe  grapes  gave  (in  1868)  577  to  688 
grammes  of  juice ;  and  i  litre  of  juice  contained — 

Water 860  to  830  grammes 

Sugar  (dextrose  and  levulose)  .         .     150  „  300        „ 
Pectin,  gums,   extractive  matter,) 

protein     substances,    organic  [•        30  „     20        „ 

acids,  and  mineral  matters    .  I 

1040  to  1 1 50       „ 
1000  parts  of  juice  of  ripe  (Rhine,  1868)  grapes  contained — 

I.  2.  3. 

Solid  matter      ....  164*4  •••  l&9'7  •••  204-6 

Sugar         .                 ...  149*9  ...  162-4  ...  174-0 

Free  acid  .        .        .        .        .7-2  ...  6'8  ...  4-8 

Ash 27  ...  3-0  ...  4-0 

In  too  parts  of  the  ash  were  contained — 

I.  2.  3. 

Phosphoric  acid         .        .        .     16*6        ...         i6'i        ...         14-0 
Potash       .        .        ...        .     64-2        ...        66-3        ...        71-4 

Magnesia   .....      47        ...          2'8        ...          2'6 

C.  Neubauer  (1868)  analysed  two  kinds  of  grapes,  and  found — 

Neroberger  Steinberger 

(Large  Grapes).  (Selected  Grapes). 

Sugar 18-06  ...  24-24 

Free  acid 0*42  ...  0*43 

Albuminous  substances      .         .        .  0*22  ...  0*18 

Mineral  constituents  (potash,  phos-  ) 

phoricacid,  &c.)     .        .        .        ]"  °'47 

Combined  organic  acids  and  extract- 1 
ive  matter  j 

Total  of  soluble  constituents      .        .         23-28  ...  29*22 

Water 7672  ...  70-78 

lOO'OO  ICO'OO 


SECT,  vi.]  WINE  MAKING.  723 

The  Fermentation  of  the  Grape-juice. — The  fermentation  of  the  grape-juice  is 
spontaneous — that  is,  it  is  consequent  upon  the  exposure  of  the  grape- juice  to  the 
atmosphere,  without  the  addition  of  yeast.  The  albuminous  matter  of  the  must  forms, 
under  the  influence  of  the  atmospheric  spawn,  or  yeast  germ,  the  well-known  fungus 
Penicillium  glaucum,  or  yeast  cells.  The  fermentation  begins  at  a  temperature  of  10° 
to  15°,  and  is  effected  more  or  less  rapidly  according  to  the  temperature.  Too  low  a 
temperature  will  retard  the  progress  of  fermentation,  as  also  will  the  addition  of  sul- 
phurous acid ;  the  same  effect  is  obtained  by  the  addition  of  other  sulphur  compounds, 
as,  for  instance,  the  essential  oil  of  mustard,  which  contains  allyl  sulphocyanide. 
The  must  is  left  in  open  vats.  Bubbles  of  carbonic  acid  soon  appear,  scum  collects 
upon  the  surface  of  the  juice,  and  an  alcoholic  odour  pervades  the  wine  at  this  stage. 
About  the  seventh  day  the  fermentation  commences  to  decrease,  and  about  the  tenth 
or  fourteenth  day  the  fluid  begins  to  clear,  no  more  carbonic  acid  or  scum  appearing. 
The  yeast  cells  formed  are  carefully  removed  from  the  bottom  of  the  vessel,  and  the 
wine  run  into  casks,  where  it  undergoes  a  slight  after-fermentation.  If  there  be  much 
sugar  contained  in  the  grape,  and  a  small  quantity  of  azotised  matter,  the  resulting 
wine  will  be  sweet ;  but  if  the  proportion  of  sugar  be  small  and  albumen  large,  a  dry 
wine  is  the  result. 

Drawing-off  and  Cashing  the  Wine. — After  the  principal  fermentation,  the  greater 
part  of  the  sugar  of  the  must  is  found  to  be  separated  into  alcohol  and  carbonic  acid. 
There  is  still  likely  to  arise,  unless  the  temperature  be  considerably  decreased,  a  fresh 
fermentation,  known  as  the  after-fermentation.  Should  this  after-fermentation  continue 
too  long,  vinegar  is  formed,  and  to  prevent  this  the  wine,  after  the  disappearance  of  the 
bubbles  of  carbonic  acid  upon  the  conclusion  of  the  principal  fermentation,  is  at  once 
"  spigotted  off"  from  the  lees  into  casks,  the  object  being  to  cut  off  communication  with 
the  atmosphere  as  much  as  possible.  The  casks  are  nearly  filled,  and  are  bunged  loosely, 
being  filled  completely  a  day  or  two  after.  Wines  casked  in  December  will  often  con- 
tinue fermenting  till  February  or  March.  Strong  wines  rich  in  alcohol  can  be  kept  in 
cask  until  they  have  become  quite  clear ;  but  weak  wines  must  be  soon  bottled,  as  the 
oxygen  of  the  air  is  liable  to  convert  the  hydrate  of  the  oxide  of  ethyl,  or  alcohol,  into 
tri oxide  of  acetyl,  or  vinegar. 

Constituents  of  Wine. — Constituents  that  were  not  found  in  the  must  are  character- 
istic of  the  wine ;  the  chief  of  these  is  alcohol.  Succinic  acid  and  glycerine,  the  constant 
products  along  with  alcohol  and  carbonic  acid  of  vinous  fermentation,  are  also  to  be  found. 
A  "  dry  "  wine,  such  as  the  French  and  Rhenish  wines,  is  one  in  which  all  the  sugar 
has  been  decomposed ;  a  "  sweet"  wine,  on  the  other  hand,  is  one  in  which  some  sugar 
has  remained  undecomposed,  either  from  an  insufficiency  of  albuminous  matter  to  nourish 
the  yeast  cells,  or  from  the  checking  of  the  fermentation  by  exposure  to  a  low  tempera- 
ture. A  very  sweet  and  thickly  fluid  wine  is  termed  a  "liqueur."  The  difference  in 
colour  is  due  to  three  substances — a  blue  colouring  matter,  a  brown  colouring  matter, 
and  tartaric  acid.  The  brown  colouring  matter  is  present  in  all  light  or  white  wines, 
while  the  blue  colouring  matter,  found  in  the  skins  of  purple  or  black  grapes,  becomes 
in  the  wine  a  red  colour,  the  change  arising  from  the  contact  with  the  tartaric  acid. 
Wines  of  the  first  year  after  growth  are  termed  new  or  "  green  "  wines.  The  average 
composition  of  wines,  in  1000  parts,  is  the  following  : — 


724 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


900-891 
80-70 


20-30 


Fig.  506. 


Water      .         .         .         ..... 

Alcohol*          ...  .... 

Homologues  of  alcohol  (propylic,  butylic  alcohol)* 

Ethers  (acetic,  osnanthic)* 

Essential  oils  .         .         .      ..<< 

Grape  sugar  (dextrose  and  levulose)       .         ...;•_•  .... 

Glycerine*       .         .         .         .    „.  .        .      ,..;.,,.' 

Gums      .         .    .     .        .  -      .  .      .         , "       .       ., 

Pectin     .  *'r  ."''''  I"      ....         .         .  '  " 

Colouring  and  fatty  substances       .         .         .'     '  .    ' 
Protein  bodies  •'•  •>.  '•*  •  '•.   '     .  '      ...         . 

Carbonic  acid*        .    ;.'.,i        ,         ..        .         .    ..-:».'/ 

Tartaric  and  racemic  acids     .      '.•>'•..    .         ..',/..  .j 

Malic  acid        .....'.. 

Tannic  acid     .  "     '.    "    ."      .        .         ., 
Acetic  acid*    .    '    '.  "  '  .         .        .  '.     .'        . 
Lactic  acid  (?)  *      .    -1'.    •     :•       . 
Succinic  acid*         ,.:>i-v-     '•..'  '.-..•    •  .        , 
Inorganic  salts         .   .;.  »   ' 
Those  substances  marked  (*)  are  formed  during  the  principal  fermentation. 

The  quantity  of  alcohol  contained  in  a  wine  is  due  partly  to  the  quantity  of  sugar 

and  partly  to  the  quantity  of  albuminous  matter  con- 
tained in  the  must.  It  is  chiefly  ethylic  or  ordinary 
alcohol.  The  specific  weight  of  the  wine  gives  only 
approximately  the  alcoholic  contents.  A  better 
method  of  estimation  is  by  means  of  an  alcoholometer. 
Of  these  instruments,  Geissler's  vaporimeter  is,  per- 
haps, one  of  the  best,  in  which  the  pressure  exerted 
by  the  vapour  of  the  wine  upon  a  column  of  mercury 
gives  a  measure  of  the  alcohol  contained.  The  vapour 
of  absolute  alcohol  at  a  temperature  of  78'3°  exerts 
a  tension  equal  to  that  exerted  by  aqueous  vapour  at 
1 00°.  It  is  therefore  only  necessary  to  ascertain  the 
height  of  the  column  of  mercury  and  the  temperature 
to  arrive  at  the  quantity  of  alcohol.  The  apparatus 
is  shown  in  Fig.  506,  and  consists  essentially  of  four 
parts — viz.,  (i)  A  brass  vessel,  A,  half  filled  with 
water,  heated  by  means  of  the  lamp  to  the  boiling- 
point  ;  (2)  A  bent  glass  tube,  B,  to  which  a  wooden 
scale  is  fixed  ;  (3)  A  cylindrical  glass  vessel,  0,  filled 
with  mercury  and  the  wine  to  be  tested ;  (4)  A 
cylinder  of  sheet-brass,  in  the  upper  part  of  which  a 
thermometer,  T,  is  fixed.  The  glass  vessel,  0,  is 
filled  with  mercury  to  the  mark,  a,  and  then  com- 
pletely filled  with  the  liquid  to  be  tested.  The  boiling- 
vessel  is  now  affixed,  the  brass  cylinder  drawn  over 
the  mercury  tube,  and  the  thermometer  inserted. 
Heat  is  applied,  and  the  water  raised  to  the  boiling- 
point  ;  the  steam  ascends  into  the  brass  cylinder,  and 
heats  the  wine  and  mercury  to  the  boiling-point  of 
water.  The  wine  expands,  and  is  partly  vaporised, 
forcing  the  mercury  up  the  arm,  B,  which  has  been 
previously  graduated  by  experiments  with  fluids  of 
known  alcoholic  contents ;  the  mercury  of  course 
rises  the  higher  the  more  .alcohol  there  is  contained  in  the  wine.  The  variable  consti- 


SECT.    VI .] 


WINE  MAKING. 


725 


tuents  of  the  wine,  the  extractive  matter,  &c.,  do  not  influence  the  result.  The 
carbonic  acid  must  have  been  removed  previously  by  filtering  the  wine  through  freshly 
burnt  lime.  Equally  good,  if  not  better,  results  are,  however,  to  be  obtained  by  the 
distillation  test,  effected  by  distilling  10  c.c.  of  the  wine,  and  adding  to  the  distillate 
sufficient  water  to  make  a  total  of  10  c.c.,  the  specific  weight  of  the  fluid  giving  the 
alcoholic  contents  of  the  wine.  The  alcoholometer  most  generally  employed  is  the 
ebuMioacope  of  Tabarie  (Fig.  507).  With  the  barometer  at  760  mm.  water  boils 

Fig.  508. 


at  +  1 00°,  and  alcohol  at  +  78'3°  C.  The  nearer,  therefore,  the  boiling-point  of  the 
fluid  tested  approaches  7 8  '3°,  the  greater  the  alcoholic  contents.  The  wine  is  poured 
into  the  vessel  (7,  and  the  cover,  E  II,  replaced.  The  fluid  is  heated  by  means  of  the 
lamp,  L,  and  the  steam  ascends  round  the  thermometer,  t  t',  the  height  of  the  mercury 
of  which,  when  the  fluid  boils,  varies  inversely  as  the  alcoholic  contents  of  the  wines 
tested.  The  vessel  M  M'  is  filled  with  cold  water,  to  hasten  the  condensation  of  the 
vapours.  If  the  boiling-point  of  pure  water  be  taken  at  99-4°  C.,  the  following  boiling- 
points  show  the  quantity  of  alcohol  contained  : — 


96-4°  C.  3  per  cent,  alcohol 

95'3    ,    4 

94'3 


927 
91-9 


91-1°  C.    9  per  cent,  alcohol 

9O'2       ,    1O  i, 

11  >< 

12  „ 

,    13 
14 


>4 


Latterly,  the  ebullioscope  of  Malligand  and  Vidal  has  come  into  use  in  France  and 
Germany.  It  consists  of  a  brass  vessel,  F  (Fig.  508),  of  the  form  of  a  truncated  cone, 
and  is  connected  at  its  bottom  with  a  vessel,  bent  in  the  shape  of  a  ring.  A  lid, 
which  can  be  screwed  on,  and  which  is  provided  with  two  apertures,  closes  the  vessel 


726 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


^perfectly  air-tight.  One  of  the  apertures  receives  the  refrigerator,  7?,  and  the 
other  the  thermometer,  T.  The  thermometer  is  horizontal,  and  is  provided  with  a 
scale,  upon  which  the  vol.  percentages  of  alcohol  are  shown,  from  o°  to  25°.  The 
boiler  is  first  filled  with  water,  which  is  heated  to  boiling  by  the  spirit-lamp,  L,  and 
the  thermometer  is  read  off.  Boiling-point  answers  to  the  nul  of  the  alcoholic  scale. 
The  vessel  is  then  filled  with  the  wine  in  question  up  to  a  ring  in  the  inside,  and 
its  proportion  of  alcohol  is  found  by  heating  to  the  boiling-point.  Wines  very  rich 
in  alcohol  are  first  diluted  with  an  equal  volume  of  water  before  being  submitted  to 
the  experiment. 

Amagat's  ebullioscope  (Fig.  509),  in  order  to  compensate  for  the  height  of  the  baro- 
meter, has,  in  addition  to  the  wine-boiler,  A,  a  similar  boiler,  7?,  for  water.  The  pipes 
leading  to  the  funnels,  C  and  D,  are  surrounded  by  the  coolers,  R. 
When  the  instrument  is  to  be  used,  50  c.c.  of  the  wine  in  question 
are  introduced  into  A  through  the  funnel  C,  and  15  c.c.  water  into 
B  through  D,  and  it  is  heated  to  a  boil  by  means  of  the  spirit-lamp, 
L.  The  thermometer  F  shows  the  boiling-point  of  water,  accord- 
ing to  which  the  scale  G  is  fixed  by  means  of  the  handle,  k,  so  that 
the  result  can  be  read  off  on  the  thermometer  E. 

Red  French  wines  contain  9  to  14  percentage  by  volume  of 
alcohol;  Burgundy,  9,  10,  and  n  percent.;  Bordeaux,  10,  u,  and 
1 2  per  cent.  Other  French  wines  contain  8  to  i  o  per  cent. ;  the 
wines  of  the  Palatinate,  7  to  9*5  per  cent. ;  Hungarian  wines,  9  to 
ii  per  cent.  Champagne  contains  9  to  12  per  cent.;  Xeres, 
17  per  cent.;  Madeira,  17  to  23-7  per  cent.  Acids  exist  in  all 
wines,  and  are  generally  carbonic,  succinic,  tartaric,  malic,  and 
acetic  acids ;  these  acids  are  found  partly  free,  partly  combined  as 
salts ;  tartaric  acid,  for  instance,  as  cremor  tartari,  potassium  bitar- 
trate,  and  other  acid  tartrates.  Faure  found  an  essential  gum, 
which  he  termed  oenanthin,  and  which,  with  glycerine — first  shown 
by  Pasteur  in  1859  to  be  a  normal  constituent  of  wine — helps  to 
give  a  certain  consistency  to  the  wine.  Pohl  found  (1863)  in 
Austrian  wines  2'6  per  cent,  glycerine.  As  wine  ages  the  glycerine  disappears.  The 
colouring  matter  of  wine  is  of  interest  in  the  case  of  red  wines  only,  as  the  yellow-brown 
colour  of  some  wines  is  undoubtedly  due  to  oxidised  extractive  matter.  The  colouring 
matter  of  red  wines  has  received  from  Mulder  and  Maumene  the  name  of  renocyanine, 
while  it  is  commonly  termed  wine-blue;  it  is  a  blue  substance  similar  to  litmus,  pos- 
sessing the  property  of  turning  red  in  the  presence  of  acids.  It  is  insoluble  in  water, 
alcohol,  ether,  olive  oil,  and  oil  of  turpentine ;  but  soluble  in  alcohol  containing  small 
quantities  of  tartaric  or  acetic  acid.  With  a  trace  of  acetic  acid  the  solution  is  practi- 
cally blue,  turning  red  upon  the  addition  of  more  acid  ;  neutralised  with  alkalies,  the 
solution  remains  blue.  On  the  evaporation  of  a  wine  to  dryness  the  extractive  matter 
remains,  consisting  of  a  mixture  of  non-volatile  acids,  the  salts  of  organic  and  inorganic 
acids,  with  cenanthin,  colouring  matter,  sugar,  protein  substances,  and  extractive 
matter,  the  nature  of  which  is  unknown.  The  quantity  of  extractive  matter  differs 
greatly,  varying  with  the  kind  of  wine  and  the  degree  of  fermentation  of  the  sugar. 
Fresenius  found  in  Rhine  wines  a  maximum  of  io-6  and  a  minimum  of  4' 2  per  cent, 
of  extractives;  Fischern,  in  the  wines  of  the  Palatinate,  from  io'7  to  1*9  per  cent. ;  in 
Bohemian  wines,  2*26;  in  Austrian,  2-64;  in  Hungarian,  2-62  per  cent.  The  mineral 
constituents  of  wines  exist  in  but  small  quantities — as  an  average  in  old  Madeira, 
0-25  per  cent.;  in  old  Rhine  wines,  0-12  per  cent.;  and  in  old  ports,  0-235  per  cent. 
Van  Gockom,  Veltmann,  and  Mosmann  found  in  1000  parts  of  wine — 


SECT.    VI.l 


WINE  MAKING. 


727 


Madeira  . 
Teneriffe  . 
Khine  wine 
Port 


2-55  parts  of  ash 

2-91 

i  '93  i, 

2'35 


Pohl  estimated  the  following  number  of  parts  ash  in  100  parts  of  wine: — 


Bohemian 
Croatian     . 
Carniola     . 
Lower  Austrian 


1-97  part 
1-68  „ 
1-81  „ 
2'oo  parts 


Slavonian  . 
Styrian 
Tyrol 
Hungarian 


1-91  part 

1-63      ,, 

1-84      „ 
i -80 


The  ash  contains  potash,  lime,  magnesia,  soda,  sulphuric  acid,  and  phosphoric  acid. 

The  ffandtuorterbuch  der  Reinen  und  Angewandten  Chemie  (Bd.  ix.  Seite  676)  gives 
the  following  analyses  of  wine-ash,  the  first  four  being  by  Crasso,  and  the  fifth  by 
Boussingault : — 


Ash  of  Wine. 

i. 

2. 

3- 

4- 

5- 

Ash  (per  cent)        .... 

0-26 

0-34 

0'4I 

0'29 

0-18 

6?-!; 

6vo 

71"? 

62'O 

A.1'1 

Soda 
Lime 
Magnesia 
Iron  oxide 
Manganese  oxide 
Phosphoric  acid 
Sulphuric  acid 

0'3 
5*2 
3  '3 
07 
0-8 

IS'5 
5  '2 

2'O 

0-4 

3'4 
47 
0-4 
07 
16-8 
5  '5 

2*1 

I  '2 

3'4 
4'0 
O'l 
O'l 
I4-I 

3'6 

I  "2 

2'6 

5'i 
4-0 
0-4 
0-3 
17-0 

4  '9 

2  '2 

4'9 
9'2 

22'I 

5'3 
O'l 

Potassium  chloride 
Carbonic  acid 

i'5 

2'I 

I'O 

i  '5 

I3-3 

IdO'O 

100  'O 

ICO'O 

IdO'O 

lOO'O 

For  the  determination  of  glycerine  in  sweet  wines  50  c.c.  of  the  sample  are  mixed 
in  a  capacious  flask  with  10  grammes  sand  and  slaked  lime  in  powder  and  heated  on 
the  water  bath  until  no  more  lime  is  dissolved,  all  the  sugar  is  converted  into  sugar- 
lime,  and  the  mass,  after  prolonged  heating,  has  still  a  caustic  smell.  100  c.c.  of  alcohol 
at  96  per  cent,  are  gradually  added,  the  whole  is  well  shaken,  the  precipitate  is  allowed 
to  settle,  the  largest  part  of  it  is  decanted  or  passed  through  a  flannel  filter,  the  residue 
is  twice  washed  with  alcohol  (filtered),  the  precipitate  is  rinsed  upon  the  filter,  drained, 
washed  again  if  the  filtrate  is  slightly  yellowish,  the  alcohol  is  expelled  from  the  filtrate, 
and  the  residue  is  treated  like  the  first  evaporation  residue  of  a  common  wine. 

Concerning  the  odoriferous  constituents  of  wine,  which  often  determine  its  value, 
nothing  trustworthy  is  yet  known.  That  compound  which  gives  wine  its  peculiar 
odour  is  a  mixture  of  renanthic  ether  with  alcohol.  But,  according  to  an  investigation 
of  Neubauer's,  cenanthic  ether  is  a  compound  of  different  substances,  of  which  the  most 
important  are  caprylic  and  capric  ethers,  and  is  a  product  of  the  fermentation  of  the 
must.  The  bouquet  (German  :  Blume)  is  probably  a  mixture  of  ethers  formed  during 
fermentation,  but  which,  on  account  of  their  extremely  minute  quantity,  have  not  been 
•distinguished  and  insulated. 

Neubauer  justly  says  in  his  Chemie  des  Weines :  "  Everything  which  art  has  yet 
-done  to  imitate  the  aroma  of  wine,  in  spite  of  the  enticing  names  by  which  it  is 
advertised,  is  a  miserable  sham  [elendes  Machwerk].  Our  chemical  knowledge  of  the 
bouquet  is  extremely  trifling,  and  science,  with  her  present  resources,  is  impotent  as 
against  the  genii  of  wine." 

The  Diseases  of  Wine. — Wines  are  subject  to  various  causes  of  deterioration,  termed 
maladies,  distempers,  or  diseases.  That  most  commonly  occurring  is  ropiness  or 
viscidity,  the  cause  of  which  was  for  a  long  time  unknown.  Fra^ois  showed  that  it 


728  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

was  due  to  the  decomposition  of  the  glucose  into  azotised  matter  and  mannite,  and  at 
the  same  time  indicated  the  proper  remedy — the  addition  of  tannic  acid.  He  employs 
15  grammes  of  tannin  to  230  litres  of  wine.  This  is  well  mixed  with  the  wine,  which  is 
allowed  to  stand  for  a  few  days.  At  the  end  of  this  time  the  tannin  will  have  separated 
the  azotised  matter,  and  the  wine  may  be  bottled  off. 

The  souring  of  wine  is  due  to  the  conversion  of  the  alcohol  into  acetic  acid,  caused, 
according  to  Pasteur,  by  the  formation  of  the  vinegar  plant,  or  Mycoderma  aceti,  which 
he  found  in  all  sour  wines.  This  disease  is  very  common,  and  may  result  from  too 
small  a  proportion  of  alcohol,  too  high  a  temperature  of  the  cellars,  or  exposure  to 
the  atmosphere.  The  wine,  if  too  far  soured,  is  fit  only  for  making  vinegar ;  but 
slight  cases  can  be  remedied  by  an  addition  of  sugar.  The  formation  of  vinegar  may 
be  somewhat  delayed  by  impregnating  the  wine  with  sulphurous  acid.  In  some 
cases  the  acetic  acid  may,  by  the  addition  of  tartaric  acid,  be  removed  as  acetic  ether  ; 
but  the  acetic  acid  can  never  be  neutralised  with  alkalies,  as  the  salts  formed  are 
very  easily  soluble. 

The  bittering  of  wine,  or  its  acquirement  of  a  bitter  flavour,  is  due  to  another 
cause,  the  formation  of  a  bitter  substance,  which  develops  as  the  wine  ages,  or  at  too 
high  a  temperature.  Maumene  suggests  as  a  remedy  the  addition  of  slaked  lime  in 
the  proportion  of  0-25  to  0-50  gramme  per  litre.  Bittering  is  due  also  to  the  formation 
of  brown  aldehyde  resin.  Mould  in  wines  appears  as  a  white  vegetable  (fungus)  film 
covering  the  surface,  and  arises  from  an  insufficiency  of  alcohol ;  consequently,  weak 
wines  are  more  subject  to  this  malady.  The  film  of  mould  should  be  removed  and  the 
wine  used  as  soon  as  possible,  for  wine  affected  with  this  disease  soon  turns  sour.  The 
decaying  of  a  wine  is  due  to  the  dissipation  of  the  alcohol  and  the  decomposition  of 
the  acids  of  the  wine ;  the  wine  obtains  an  astringent  taste  and  a  dim,  thick  colour, 
finally  turning  sour.  The  potassium  bitartrate  is  converted  into  potassium  carbonate, 
affecting  the  colouring  matter,  and  tannic  acid,  which  pass  over  into  humus  substances. 
At  the  commencement  of  this  decomposition  a  remedy  may  be  found  in  the  addition  of 
a  small  quantity  of  sulphuric  ether.  Caskiness,  or  the  taste  of  the  cask,  due  to  an 
essential  oil  formed  in  casks  that  have  long  stood  empty,  is  best  removed  by  the 
addition  to  the  wine  of  a  small  quantity  of  olive  oil,  and  agitation  ;  the  olive  oil 
absorbs  the  essential  oil,  and  brings  it  to  the  surface  of  the  wine,  whence  the  oily 
matter  may  be  skimmed,  or  the  wine  may  be  filtered  through  freshly  burnt 
charcoal.  All  casks  and  vessels  that  have  stood  long  empty  should  be  well  steamed 
before  use. 

Pasteuring. — Pasteuring,  a  term  which  usage  has  substituted  for  pasteurisation, 
or  the  conservation  and  artificial  ageing  of  wines,  according  to  Pasteur's  method,  is 
a  great  improvement  in  the  general  treatment  of  wines  to  ensure  their  keeping.  It 
consists  essentially  in  heating  the  wine  to  60°  C.,  and  for  this  purpose  the  apparatus 
designed  by  Rossignol  is  best  suited.  A  metal  cask,  T  (Fig.  510),  contains  at  the 
bottom  a  copper  vessel,  (7,  with  a  trumpet-shaped  cover  extending  in  the  open  tube,  c, 
above  the  top  of  the  vessel  T ;  t  is  a  thermometer.  Water  is  poured  into  the  vessel, 
C,  until  the  tube  c  is  three  parts  full.  The  wine  is  placed  in  the  metal  cask,  T,  and, 
by  means  of  the  tap,  r,  and  the  tube/,  run  off  into  the  cask  f,  when  sufficiently 
heated.  The  water  in  the  copper  vessel,  C,  is  employed  to  prevent  the  direct  heating, 
by  the  flame,  of  the  vessel  containing  the  wine,  and  the  consequent  burning  of  any 
insoluble  matter  settling  to  the  bottom  of  the  vessel.  Fig.  511  shows  in  detail  the 
manner  of  fastening  the  vessels  together.  A  copper  ring,  a,  encircles  the  vessel  T,  and 
beds  with  the  walls  of  this  vessel  into  the  india-rubber  band,  d,  into  which  it  is  pressed 
by  the  tightening  of  the  bolts,  e,  binding  the  ring  of  angle-iron  and  lower  iron  ring,  6, 
together.  The  joint  is  thus  rendered  water-tight.  The  vessel  T  is  not  quite  filled 
with  wine,  to  allow  for  expansion  under  heat ,  by  this  means  the  wine  is  exposed  to  a 


WINE  MAKING. 


729 


known  quantity  of  air.  Wine  should  not  be  artificially  aged  in  contact  with  air,  as 
Pasteur  has  proved  that  such  processes  deteriorate  the  colour  and  the  flavour  of  the 
wine ;  and  in  ordinary  cases,  where  part  of  the  process  of  ageing  consists  in  heating 
the  wines  for  a  short  time  in  an  open  vessel  with  a  full  exposure  to  air,  the  wine 
acquires  a  peculiar  boiled  flavour,  goilt  de  cuit,  easily  recognisable  by  the  connoisseur. 
By  Pasteur's  method,  however,  neither  the  flavour  nor  the  colour  of  the  wine  is  deterio- 
rated ;  indeed,  the  latter  is  improved  by  the  expulsion  of  the  carbonic  acid. 

Pasteur  has  shown  that  most  of  the  diseases  of  wine  (acetification,  ropiness, 
bitterness,  and  decay  or  decomposition)  are  due  to  the  growth  of  different  fer- 
ments, consisting  of  minute  vegetable  cells,  always  existing  in  wines,  and  becoming 
active  and  destructive  under  certain  conditions,  such  as  change  of  temperature  and 
oxidation.  He  recommends  *  that  these  plants  or  fungi  should  be  kitted,  as 
the  best  means  of  ensuring  the  keeping  of  the  wine,  and  the  particular  modus 
operandi  selected  is  essentially  the  following,  differing  considerably  from  the  fore- 
going method.  The  bottles  are  quite  filled,  the  wine  touching  the  cork,  which  is 
inserted  with  such  a  degree  of  firmness  that  the  wine  in  expanding  may  force  tho 


Fig.  510. 


Fig.  512. 


Ffg.  511. 


cork  out  a  little,  but  not  so  much  as  to  admit  air  into  the  bottle.  The  bottles  are 
then  placed  in  a  chamber  heated  to  45°  to  100°,  where  they  remain  for  an  hour  or  two, 
after  which  they  are  removed,  set  aside  to  cool,  and  the  cork  driven  in.  By  this  means 
the  life  or  active  principle  of  the  fungi  is  destroyed,  while  the  wine  acquires  an 
increased  bouquet,  is  of  a  more  beautiful  colour,  and,  in  fact,  is  to  a  considerable  extent 
aged.  Both  new  and  old  wines  can  be  thus  treated. 

For  heating  wine  in  its  own  casks,  Ballo  proposes  an  apparatus,  the  hygrothermant. 
The  liquid,  heated  in  the  spiral,  ascends  through  the  tube,  a  (Fig.  512),  into  the  cask, 
and  cold  wine  enters  in  its  place  through  b.  The  circulation  begins  with  the  smallest 
difference  in  temperature  between  a  and  b,  and  lasts  to  the  boiling-point.  The 
apparatus  depends  on  the  principle  of  heating  by  hot  water.  The  novelty  here  is  that 
the  cold-  and  hot-water  pipes,  on  their  exit  from  the  source  of  heat,  unite  to  a  single 
tube  in  which  the  two  opposite  currents  are  separated  by  a  thin  metal  partition.  The 
form  of  the  pipe  is  shown  in  Fig.  513. 

*  Comptes-Rendus.  May  I,  29;  August  14,  1865. 


73o  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

Clearing  or  Fining  the  Wine. — Most  wines  are  self -clearing,  the  ferment  settling  to 
the  bottom  of  the  cask,  and  leaving  the  wine  clear  and  pure.  This  applies  chiefly  to 
dry  wines,  which  have  less  sugar  than  sweet  wines.  The  sweet  wines  are  generally 
more  thickly  fluid  on  account  of  the  quantity  of  sugar  they  contain,  and  consequently 
more  frequently  need  clearing.  Fining,  as  it  sometimes  called,  or  clearing,  consists  in 
adding  to  the  muddy  wine  some  albuminous  or  similar  substance  that  will  mix  with 
the  suspended  matter  and  carry  it  to  the  bottom  or  bring  it  to  the  surface  of  the  wine. 
The  substances  most  generally  employed  are  white  of  egg,  ox-blood,  and  milk,  or 
mixtures  of  these  substances.  "  Plastering,"  or  the  addition  of  gypsum  to  the  must,  is 
said  to  improve  the  colour  of  red  wines,  and,  by  taking  up  water,  it  increases  the  relative 
proportion  of  alcohol,  which  retards  the  fermentation,  and  thus  gives  more  time  for  the 
extraction  of  colouring  matter.  It  converts  the  soluble  potassium  salts  into  insoluble 
lime  salts  and  potassium  sulphate.  As  the  plastered  wine  contains  potassium  sulphate 
in  quantity  and  remains  saturated  with  gypsum,  wine  thus  treated  has  probably  un- 
pleasant and  injurious  effects  on  the  human  organism ;  the  addition  of  gypsum  to  wine 
is  to  be  unconditionally  condemned. 

Hugounenq  recommends,  instead  of  gypsum,  an  addition  of  calcium  diphosphate  as  a 
clarifying  and  preservative  agent.  "  Phosphatage  "  is  said  to  have  all  the  good  effects 
of  plastering  without  increasing  the  proportion  of  sulphates  and  diminishing  that  of 
phosphates. 

Residues  from  the  Production  of  Wine. — The  waste  of  wine  making  consists  of  the 
stems,  husks,  and  seeds  of  the  grapes,  as  well  as  of  the  fermentary  sediment  and  tartar. 
Both  descriptions  of  waste  find  numerous  applications.  The  lees  left  from  the  pressing 
of  the  wine  contain  a  not  unimportant  quantity  of  must,  which  (i)  is  employed  in 
preparing  an  inferior  wine ;  (2)  in  the  making  of  an  inferior  brandy ;  (3)  in  the  pre- 
paration of  verdigris  (see  page  458) ;  (4)  in  vinegar  making,  and  for  promoting  the 
formation  of  vinegar  from  saccharine  or  alcoholic  fluids.  (5)  In  wine-making  countries 
the  lees  are  much  employed  as  fodder  for  horses,  mules,  and  sheep;  while  (6)  the 
residue  of  the  after-pressing  or  final  pressing  is  used  as  manure.  (7)  The  grape  seed 
yields  an  oil  in  quantities  of  10  to  u  per  cent.,  or  (8)  tannic  acid  in  large  quantities. 
The  oil  can  be  extracted  by  pressure  or  by  treatment  with  benzole,  or  with  carbon 
disulphide.  The  tannin  obtained  can  be  employed  for  the  preservation  of  hides,  &c. 
(9)  Potash  is  prepared  from  the  calcined  lees.  (10)  The  stalks  and  seeds  when  calcined 
are  employed  in  the  preparation  of  a  black  colouring  material  (vine  black),  (n)  The 
ferment  and  stalks  are  in  some  wine-producing  countries,  besides  being  employed  in 
the  preparation  of  tartar  and  potash,  also  used  in  the  distillation  of  a  peculiarly  rich 
brandy,  in  which  an  oil  is  found  possessing  highly  the  flavour  of  cognac,  and  known  in 
commerce  as  wine  oil,  cognac  oil,  huile  de  marc.  (12)  Crude  tartar  is  found  with 
calcium  tartrate,  colouring  matter,  and  yeast,  forming  a  more  or  less  thick  crust  on  the 
walls  of  the  wine  cask  or  in  the  crust  deposited  in  the  wine,  but  not  firmly  attached  to 
the  vessel,  and  is  the  chief  source  of  the  pharmaceutical  potassium  bitartrate  (C4H5KO6) 
and  tartaric  acid. 

Effervescing  Wines. — Effervescing  wines  have  been  known  for  many  centuries. 
Some  of  Rembrandt's  paintings  exhibit,  among  the  accessories,  a  champagne  glass  with 
effervescing  wine.  And  from  Yirgil — 

"  Ille  impiger  hausit, 
Spumantem  pateram  " — 

it  would  appear  that  this  description  of  wine  was  known  to  the  Romans.  In  1870 
there  were  in  Germany  fifty  producers  of  effervescing  wines,  with  a  production  of  2^ 
to  3 1  millions  of  bottles,  i|  million  of  which  were  exported.  In  France  the  pro- 
duction amounts  yearly  to  16  to  18  millions  of  bottles. 

All  wines  are  capable  of  being  produced  as  effervescing  wines  if  bottled  before  the 


SECT,  vi.]  WINE  MAKING.  731 

fermentation  is  over.  By  bottling  at  this  period  the  carbonic  acid  is  retained  in  the 
wine,  and,  when  the  bottle  is  opened,  the  disengagement  of  the  gas  causes  the  appear- 
ance of  effervescence.  In  this  country  the  effervescing  wine  most  generally  known  is 
champagne ;  but  hocks,  Moselles,  and  even  red  wines  are  very  admirable  when  thus 
treated.  If  the  wine  contains  much  sugar,  the  fermentation  is  arrested  in  the  bottle 
before  all  the  sugar  is  consumed,  producing  a  sweet  effervescing  wine.  On  the  other 
hand,  if  the  sugar  is  all  exhausted  in  producing  the  carbonic  acid,  the  result  is  a  dry 
effervescing  wine.  These  wines  are  very  agreeable  to  the  palate,  and  may  be  supposed 
to  assist  the  digestion  of  the  food  with  which  they  are  taken ;  but,  when  new,  they 
are  dangerous,  as  being  likely  to  communicate  their  state  of  change  to  the  contents 
of  the  stomach,  interfering  seriously  with  digestion,  and  producing  what  is  well  known 
as  "  acidity."  Dry  effervescing  wines  are  less  likely  to  disagree  than  sweet  wines  of 
this  class  containing  much  sugar  and  fermentable  matter.  The  connoisseur  places 
great  reliance  in  his  judgment  of  a  champagne  upon  the  loudness,  or  rather  sharpness, 
of  the  report  when  the  cork  is  drawn,  and  upon  the  "  bead  "  or  bubble  formed  on  the 
side  of  the  glass  by  the  carbonic  acid  gas.  These  effects  are  not  proportionate,  for 
while  a  loud  report  results  from  an  extended  fermentation,  a  good  bead  may 
be  obtained  with  a  very  weak  fermentation.  The  gas  in  a  bottle  of  champagne 
exerts  a  pressure  of  some  5  atmospheres,  and  it  will  at  once  be  evident  that  if 
the  bottle  be  made  a  little  smaller,  reducing  the  space  between  the  cork  and  the 
wine  only  one-twentieth,  a  considerable  increase  in  loudness  of  the  report  will 
ensue. 

The  process  of  manufacturing  effervescing  wines  is  in  general  the  following : — The 
best  grapes  are  used  for  this  purpose ;  for  champagne,  the  black  grape,  called  by  the 
French  noirien,  is  employed.  The  juice  is  expressed  from  the  grape  as  soon  after 
gathering  as  possible,  in  order  to  prevent  the  colouring  matter  of  the  skin  affecting  the 
wine ;  while  the  fruit  is  pressed  as  quickly  and  as  lightly  as  possible.  The  juice  from 
the  second  and  third  pressings  is  reserved  for  inferior,  or  red-tinted  effervescing  wines. 
The  expressed  juice  is  immediately  poured  into  tuns  or  vats,  where  it  is  left  to  stand 
for  twenty-four  to  thirty-six  hours.  In  this  time  any  earthy  matter  or  vegetable  im- 
purities will  have  settled,  and  the  juice  is  ready  to  be  transferred  to  the  fermenting 
vats,  where  it  remains  for  about  fifteen  days.  It  is  then  put  into  casks,  which  are 
securely  bunged ;  sometimes  brandy  is  added  in  the  proportion  of  one  bottle  to  one 
hundred  bottles  of  juice  or  must.  Towards  the  end  of  December  the  wine  is  fined 
with  isinglass,  and  a  second  time  in  the  ensuing  February.  About  the  beginning  of 
April  the  clear  wine  is  fit  for  bottling.  It  now  contains,  if  a  good  wine,  16  to  18 
grammes  of  sugar,  u  to  12  per  cent,  of  the  volume  of  alcohol  per  bottle,  and  an 
equivalent  to  3  to  5  grammes  of  sulphuric  acid  in  free  acids. 

Great  care  is  necessary  in  the  manufacture  of  champagne  bottles ;  they  must  be 
free  from  flaws,  and  made  of  pure  materials.  Generally  each  bottle  is  from  850  to  900 
grammes  in  weight,  and  equal  in  thickness  throughout.  Formerly  the  flawed  bottles 
amounted  to  15  to  25  per  cent.,  but  recent  improvements  in  manufacture  have  reduced 
the  percentage  to  10.  Before  the  wine  is  introduced,  the  bottle  is  rinsed  with  a  liqueur 
•of  white  sugar-candy  150  kilos.,  wine  125  litres,  and  cognac  10  litres,  the  liqueur  being 
.allowed  to  remain  in  the  bottle :  according  to  F.  Mohr,  the  cane  sugar  of  the  liqueur 
becomes  converted  into  grape  sugar  in  the  champagne.  It  is  doubtful  whether  glycerine 
might  not  be  advantageously  substituted  for  a  portion  of  the  sugar  of  the  liqueur. 
The  liqueur  employed  varies  with  the  flavour  of  the  wine :  port,  Madeira,  essence  of 
muscatels,  cherry  water,  &c.,  are  used,  but  rarely  unmixed  with  some  other  favourite 
solution  of  the  manufacturer,  as,  for  instance,  water  60  litres,  saturated  solution  of 
alum  20  litres,  tartaric  acid  solution  40  litres,  tannin  solution  80  litres.  About  2  litres 
of  this  mixture  would  in  practice  be  added  to  a  butt  of  wine.  The  bottles  are  filled  by 


732 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


women,  the  proportion  of  liqueur  introduced  being  about  15  to  16  per  cent,  of  the 
wine.  A  space  of  about  2  to  3  inches  is  left  between  the  wine  and  the  cork,  which, 
after  being  thoroughly  moistened,  is  next  inserted  by  a  machine.  The  bottle  is  then 
passed  to  a  man,  termed  in  the  French  establishments  the  maillocher,  who  drives  the 
cork  home  with  a  mallet.  Another  process,  now  generally  effected  by  the  aid  of  a 
machine,  is  the  "wiring"  or  securing  the  cork  with  wire  or  string.  The  bottles  are 
now  conveyed  to  a  cellar,  where  they  are  laid  in  horizontal  racks  against  the  wall. 
In  about  eight  or  ten  days  a  deposit,  termed  "  griffe,"  is  formed,  and  shows  that  the 
time  has  arrived  for  the  wine  to  be  transferred  to  the  cellar  where  it  is  to  remain 
until  sold  to  the  merchant.  The  deposit  is  allowed  to  form  during  the  summer,  and  in 
the  ensuing  winter  means  are  taken  for  its  removal.  The  bottles  are  well  shaken,  and 
placed  with  their  mouths  downwards,  to  cause  the  deposit  to  settle  on  the  cork.  The 
cork  being  removed,  the  sediment  falls  out,  when  more  liquor  is  added,  and  the  bottle 
re-corked  and  again  wired.  The  bottle  is  now  laid  upon  its  side  at  an  angle  of  about 
20°,  and  in  about  eight  to  ten  days  the  inclination  is  gradually  increased  until  the 
vertical  position  is  attained,  when,  by  a  dexterous  movement  of  the  cork,  the  gas  is 
permitted  to  force  out  the  remaining  sediment.  This  process  is  repeated  as  many 
times  as  may  be  necessary,  until  the  wine  is  perfectly  clear.  Wine  thus  prepared, 
generally  known  as  sparkling  wine,  inn  mousseux,  is  ready  for  the  consumer  at  the  end 
of  from  eighteen  to  thirty  months,  the  time  varying  with  the  temperature  of  the  season. 
One  of  the  greatest  causes  of  loss  is  the  bursting  of  the  bottles,  sometimes  as  much  as 
30  per  cent,  of  the  wine  being  wasted.  This  in  some  measure  accounts  for  the  dearness 
of  these  wines. 

By  the  analysis  of  several  sparkling  wines  (1867  and  1870)  the  following  results 
were  obtained : — 


*' 

' 

3- 

Per  mille. 
V3OO 

Per  mille. 
e-qoo 

Per  mille. 
7-^00 

Per  mille. 
7-800 

Per  mille. 
6"2OO 

Per  mille. 
6*500 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Alcohol    

Sugar        .         .         .        .:.:,.! 
Extractive  matter    .... 
Specific  gravity        .... 

8-400 
8-200 
1  1  -600 
1-036 

9-500 
4-300 
7-500 
1-029 

8-500 
6-900 
9-800 
1-039 

8*400 
9'100 
I2'OOO 
1-046 

9'8oo 
7-500 
1  1  -600 
1-039 

8-400 
5-400 
15-200 
1-041 

No.  i  came  from  Chalons;  Nos.  2,  3  and  4  from  Wiirtzburg,  2  being  for  export  to 
India ;  3  being  the  manufacture  of  J.  Oppmann,  and  4  of  Silligmiiller,  both  well-known 
German  firms.  No.  5  came  from  Sotaine  &  Co.,  of  Rheiins,  and  6  from  a  well-known 
Rhenish  firm,  glycerine  being  substituted  for  a  portion  of  the  sugar. 

Improving  Wine  Musts  and  Artificial  Wines. — The  worth  or  character  of  a  wine  is 
determined  by  its  aroma  and  the  amount  of  alcohol  and  free  acid  contained — decreasing 
with  an  increase  of  the  latter,  and  increasing  with  increase  of  the  former.  The  pro- 
portion between  the  chief  constituents  of  the  grape-juice,  sugar,  acid,  and  water,  is 
nearly  equal  in  all  good  wines,  and  this  proportion  is  never  accidental,  but  always 
belongs  to  a  good  wine.  The  grapes  not  fitted  for  making  good  wines  are  treated  in 
two  ways :  either  the  expressed  juice  is  allowed  to  ferment  as  it  is,  in  which  case  an 
inferior  wine  is  obtained ;  or,  by  the  study  of  chemical  analyses  of  good  wines,  the  in- 
complete constituents  are  supplied,  and  others  injurious  to  the  wine  removed,  to  make 
the  must  of  that  quality  which  will  yield  a  good  wine.  The  following  are  the  best 
methods  of  improving  the  must : — 

1.  The  addition  of  sugar  to  wine  poor  in  this  constituent,  and  the  neutralisation  of 
an  excess  of  acid  by  means  of  pulverised  marble  (Chaptal's  method). 

2.  The  addition  of  sugar  and  water  to  must  poor  in  sugar  and  rich  in  acid  (Gall's 
method). 


SECT,  vi.]  WINE  MAKING.  733 

3.  Repeatedly  fermenting  the  husks  with  sugar-water  (Petiot's  method). 

4.  Removing  the  water  by  means  of  freezing,  or  by  treatment  with  gypsum. 

5.  Removing  the  acid  by  means  of  a  chemical  reaction. 

6.  Addition  of  alcohol  to  poor  wines. 

7.  Treating  the  prepared  wine  with  glycerine  (Scheele's  method). 

The  addition  of  sugar  to  must  poor  in  this  constituent  is  the  oldest  method  of  im- 
provement, and  appears  to  have  been  known  to  the  Greeks  and  Romans.  At  that  time 
cane  sugar  was  unknown,  honey  being  used  for  sweetening  purposes,  which,  being 
added  to  the  wine,  gave  it  a  peculiar  flavour,  and  rendered  it  thick.  In  years  when 
honey  was  scarce,  we  are  informed  that  the  wine  was  inferior.  Chaptal,  in  1800,  wrote 
a  work  on  the  cultivation  of  the  grape,  in  which  he  gives  a  recipe  for  adding  sugar  to 
an  inferior  must,  to  render  the  wine  equal  to  that  of  better  years,  the  acid  being 
neutralised  with  pieces  of  marble.  In  Burgundies,  Chaptal's  method  is  not  much 
required  to  be  used,  as  these  wines  rarely  contain  more  than  6  parts  per  1000  of  free 
acid.  The  amount  of  pulverised  marble  (calcium  carbonate)  required  to  neutralise 
60  parts  of  free  acid  is,  as  a  rule,  50  parts ;  and  the  amount  of  sugar  to  be  added, 
when  the  acid  is  in  excess,  is  100  parts  for  each  50  parts  of  alcohol  required  after 
fermentation,  it  being  found  that  15  per  cent,  of  sugar  in  the  must  produces  7-5  per 
cent,  of  alcohol  in  the  prepared  wine.  Thus,  should  it  be  desired  to  heighten  the 
alcoholic  contents  from  7*5  to  10  per  cent.,  50  kilos,  of  sugar  are  added  to  every 
1000  kilos,  of  must. 

The  cause  generally  of  the  poorness  of  the  must  in  sugar  is  a  wet  or  cloudy  season, 
during  which  there  has  been  but  little  warmth  from  the  sun  to  ripen  the  grapes. 
Most  German  wines  show,  besides  a  lack  of  sugar,  a  superabundance  of  malic  and 
tartaric  acids ;  and  while  the  addition  of  a  sugar  solution  increases  the  alcoholic  con- 
tents, it  does  not  remove  these  acids,  which  impart  a  flavour  to  the  wine  and  lessen 
its  worth.  The  addition  of  saccharine  solution  does  not,  as  might  be  expected,  enfeeble 
the  bouquet  of  the  wine  if  pure  starch  sugar,  containing  no  dextrine,  be  employed. 
The  use  of  impure  starch  sugar  causes  a  quantity  of  unfermented  matter  to  remain  in 
the  wine,  imparting  to  it  a  tendency  to  decay.  Gall's  method  is  found  to  be  economical, 
as  a  flavouring  material  can  be  added  to  very  inferior  must.  According  to  Gall,  a 
normal  must  should  consist  of — 

Sugar         .         .         .         .        .        .         24*0  per  cent. 

Free  acid  .        .        .        .  .          o'6        „ 

Water 75-4        „ 

100  X> 

1000  kilos,  of  such  a  must  contain,  therefore,  240  kilos,  of  sugar,  6  kilos,  of  free  acid, 
and  754  litres  of  water.  If,  by  analysis,  the  must  to  be  improved  yields  only  167  per 
cent,  sugar  and  o'8  per  cent,  acid,  there  are  to  be  added  153  kilos,  of  sugar  and  180 
kilos,  or  litres  of  water,  by  which  addition  1333  kilos,  of  normal  must  are  obtained, 
corresponding  to  an  increase  in  quantity  of  33  per  cent. ;  while  in  some  years,  when 
the  acid  contents  are  as  much  as  12  to  14  per  cent.,  the  increase  in  quantity  rises  to 
100  to  115  per  cent.,  but  seldom  more. 

Petiot  based  his  method  on  the  fact  that,  according  to  the  usual  process  of  pre- 
paring the  must,  the  colouring  arid  bouquet  constituents  remaining  in  the  marc  are 
sufficient  to  give  the  flavour  and  odour  of  wine  to  a  lixivium  of  sugar-water.  This 
method  may  therefore  very  justly  be  considered  as  yielding  a  wine  without  the  aid  of 
grape-juice.  To  the  marc  left  after  the  expressure  of  the  grape-juice  cold  water  is 
added,  equal  in  quantity  to  the  must  removed :  in  this  water  the  marc  is  allowed  to 
macerate  for  two  to  three  days.  The  water  takes  up  the  various  soluble  constituents 
of  the  marc;  after  the  time  specified  the  liquor  is  removed,  and  the  amount  of  sugar 


734  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

and  acid  it  contains  ascertained.  There  is  usually  only  2  to  3  per  cent,  of  sugar ;  con- 
sequently, an  addition  of  17  to  1 8  per  cent,  must  be  made ;  and  if  there  should  be  too- 
little  acid,  tartaric  acid  must  be  added  to  approximate  to  the  acid  contents  of  a  normal 
must.  The  artificial  must,  as  it  may  be  considered,  is  then  put  into  the  fermenting 
vat,  while  the  marc  is  again  treated  in  a  similar  manner,  a  longer  immersion  being  this 
time  required.  The  resulting  wines  are  darker  in  colour  than  wines  prepared  from  the 
natural  must,  in  consequence  of  a  larger  proportion  of  tannin.  The  flavouring  of  these 
wines  is  a  matter  of  experience,  and  does  not  fall  under  any  chemical  consideration. 

Freezing  is  employed  in  the  improvement  of  wine,  for  the  purpose  of  reducing  the 
aqueous  contents.  According  to  the  experiments  of  Vergnette-Lamotte  and  Bous- 
singault,  the  effect  of  cold  upon  wine  is  of  a  very  complicated  nature.  By  cooling  the 
wine  at  a  temperature  of  o'6°  there  first  occurs  the  precipitation  of  those  substances 
that  are  insoluble  at  this  temperature.  These  consist  of  cream  of  tartar,  colouring 
matter,  and  nitrogenous  substances,  and  a  fluid  possessing  the  property  of  becoming 
solid  at  6°.  When  these  substances  are  removed  the  wine  becomes  more  ardent,  richer 
in  alcohol,  and  its  peculiar  merit  is  that  it  is  not  liable  to  after-fermentation,  and  can 
be  kept  in  vats  and  half-empty  casks.  The  removal  of  the  acid  from  wine  is  effected 
best  by  means  of  calcium  carbonate  (pulverised  marble,  chalk),  sugar  of  lime,  or  neutral 
potassium  tartrate.  An  addition  of  calcium  carbonate  to  the  must,  or  to  the  wine,  is 
not  detrimental,  in  so  far  that  the  wine  retains  none,  or  a  very  small  quantity,  of  the 
lime-salt.  Calcium  carbonate  will  not  be  of  service  in  the  case  of  so-called  acid  fermen- 
tation, as  calcium  acetate  will  then  be  formed,  and  the  wine  is  no  longer  worthy  the 
name.  Liebig  recommends  the  use  of  neutral  potassium  tartrate  for  this  purpose,  as 
potassium  bitartrate  is  formed,  which  settles  as  an  insoluble  salt  on  the  sides  of  the 
vessel  or  bottle.  The  use  of  this  neutralising  agent  has  the  merit,  moreover,  of  not 
injuring  the  flavour  and  odour  of  the  wine.  Sugar  of  lime  can  be  employed  in  the 
case  of  wines  not  containing  acetic  acid.  To  prepare  the  sugar  of  lime,  slaked  lime  is 
diluted  with  ten  times  the  quantity  of  water,  to  form  a  thin  cream.  This  cream  is 
thinned  with  sufficient  water  to  obtain  a  milk  of  lime,  in  which  sugar-candy  is  dissolved. 
The  solution  is  left  to  stand,  and  the  clear  supernatant  liquor — a  solution  of  sugar  of 
lime — decanted  to  mix  with  the  wine  as  required.  When  the  wine  is  treated  with  the 
sugar  of  lime  solution,  the  lime  forms  with  the  acid  of  the  wine  an  insoluble  salt,  which 
is  precipitated,  while  the  sugar  remains  in  the  wine. 

Another  addition  to  wine,  hardly  bearing  upon  its  improvement,  but  effected  as  a 
means  for  its  preservation  during  removal  or  exportation,  is  that  known  in  France  as 
the  vinage,  a  certain  quantity  of  brandy  being  mixed  with  the  prepared  wine.  When 
the  wine  is  to  be  exported  from  France,  the  law  permits  the  addition  of  5  litres  of 
brandy  to  each  hectolitre  of  wine,  provided  the  alcoholic  contents  after  the  addition  do 
not  exceed  21  per  cent.  But  experiments  have  proved  that  the  wine  delivered  to 
private  consumers  does  not  on  the  average  contain  more  than  10  to  n  per  cent,  of 
alcohol,  while  the  wine  delivered  to  retail  firms  averages  16  to  17,  and  to  wholesale 
firms  22  to  24  per  cent.  To  prevent  this  fraudulent  proceeding,  the  operation  of 
vinage  is  permitted  only  in  the  Departments  of  the  Pyrenees-Orientales,  Aude,  Herault, 
Garde,  Bouches-du-Rhone,  and  Var,  immediately  under  the  inspection  of  the  Com- 
missioners appointed  to  this  duty.  In  1865  Scheele  introduced  his  method  of  improv- 
ing wine  by  the  addition  of  glycerine,  the  addition  being  made  after  the  first  fermenta- 
tion has  subsided.  The  limits  of  the  addition  lie  between  i  to  3  litres  of  glycerine  to 
I  hectolitre  of  wine.  But  the  expense  will  not  permit  of  extended  operations. 

It  is  to  be  remarked  that  if  a  must  is  sweetened  with  starch  sugar,  a  substance 
(dextrine)  is  introduced  which  is  absent  in  natural  wines  [and  which  probably  prevents 
the  formation  of  a  fine  aroma,  doubtless  the  reason  why  malt  vinegars  are  deficient  in 
the  odour  and  flavour  of  wine,  fruit,  and  cane-sugar  vinegar]. 


SECT.  vi.J  BEER  BREWING.  735 

Cider. — A  must  obtained  from  apples  contained  before  and  after  filtration  ia 
100  c.c. — 

Must  (Filtered).  Cider. 

Alcohol    ....  ...  5 -800  centimetres 

Extract     ....  16-250  ...  2-360  grammes 

Ash           ....  0-350  ...  o '310  gramme 

Malic  acid        .         .         .  0-330  ...  o'3io        ,, 

Acetic  acid       ...  ...  0*080        „ 

Sugar        ....  12-500  ...  0-750        „ 

Pectin      ....  0-620  ...  trace 

Lime        ....  0*025  •••  0-024        » 

Magnesia          .         .         .  0*018  ...  0*018        „ 

Potassa    ....  0*106  ...  0-105        »> 

Phosphoric  acid       .         .  0-024  ...  0-022        „ 

Sulphuric  acid          .         .  0*009  •••  0*680  (?) 

Glycerine          ...  ...  0*680        „ 

Tartaric  and  citric  acids  were  absent.  Hence  cider  is  distinguished  from  grape  wine 
merely  by  the  complete  absence  of  tartaric  acid  and  the  corresponding  larger  pro- 
portion of  lime.  The  same  feature  distinguishes  gooseberry,  currant  (Ribes),  and  other 
fruit  wines.  If  a  moderate  proportion  of  tartaric  acid  is  added  to  cider  the  product 
cannot  be  distinguished  from  wine. 

APPENDIX. — A.  Kommir  finds  that  an  active  ellipsoidal  ferment,  if  introduced  into  grapes  when 
crushed  at  temperatures  below  2i°-22°,  multiplies  more  rapidly  than  the  spores  of  the  ferments  found 
on  the  skins  of  the  grapes.  If  a  small  quantity  of  an  ellipsoidal  ferment  is  added  to  grapes  at 
temperatures  above  2i°-22°,  the  ferment  added  develops  along  with  the  natural  ferment,  and  modi- 
fies the  bouquet  of  the  wine.  K.  Martinand  has  made  an  experimentum  crwis  which  seems  to  con- 
firm the  author's  theory.  He  divided  the  grapes  of  one  and  the  same  vine  into  five  lots,  and  added 
to  each  lot  a  different  ferment— to  (i)  that  of  a  must  of  cherries  in  full  fermentation  ;  (2)  of  Beau- 
jolais ;  (3)  of  Burgundy ;  (4)  of  champagne ;  (5)  of  Bordeaux.  All  these  wines  presented  distinct 
flavours. — Chemical  News,  vol.  Ixi.  p.  277. 

BEER  BREWING. 

By  beer,  in  the  ordinary  meaning  of  the  word,  we  understand  a  spirituous  liquor 
still  in  the  state  of  secondary  fermentation,  obtained  from  germinating  amylaceous 
seeds,  chiefly  barley  (or  wheat,  latterly  also  rice),  and  hops,  water,  and  yeast,  by  fermen- 
tation, but  without  distillation.  According  to  the  views  of  the  German  Brewers 
Association  and  the  International  Medical  Congress  at  Brussels  (1874),  with  which  the 
conclusions  of  the  Imperial  Sanitary  Department  coincide,  only  liquors  brewed  from 
cereals  and  hops,  fermented,  but  still  in  a  state  of  secondary  fermentation,  have  a  right 
to  be  regarded  as  beer. 

Materials  far  Beer  Brewing. — The  materials  of  beer  brewing  are: — (i)  Grain,  or 
amylaceous  substances ;  (2)  hops ;  (3)  a  ferment ;  (4)  water. 

The  Grain. — The  grain  selected  for  this  purpose  is  generally  barley,  as  containing 
the  proportion  of  sugar  and  starch  best  adapted  to  form  alcohol.  Many  substitutes 
have  been  suggested,  but  with  less  success.  In  Bavaria,  the  large  double  barley 
(Hordeum  distichon)  is  preferred.  According  to  Lermer,  100  parts  of  dried  barley 
contain — 

Starch 68-43 

Protein  substances 16-25 

Dextrine 6-63 

Fat 3-08 

Cellulose 7-10 

Ash  and  other  constituents     .        .        .        .          3*51 

The  ash  of  barley  contains  in  100  parts — 


736  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

Potash 17 

Phosphoric  acid 30 

Silicic  ac'd 33 

Magnesia •  .                .  7 

Lime 3 

with  other  constituents.  Potatoes,  rice,  maize,  glycerine,  and  potato  or  starch  sugar 
are  employed  in  some  modern  breweries. 

A  good  barley  for  brewing  should  be  rich  in  starch,  so  that,  when  malted  and  con- 
verted into  wort,  it  may  give  the  highest  proportion  of  extract.  It  must  have  a 
thorough  germinating  capacity,  swell  uniformly,  and  grow  uniformly  and  rapidly  if  it 
has  to  produce  a  good,  sound  malt.  The  starch  of  the  barleycorn  should  dissolve 
uniformly  and  rapidly  ;  it  must  be  free  from  mould  and  bacteria,  perfectly  inodorous, 
and  in  the  subsequent  operations  it  must  communicate  to  the  wort  and  the  beer  no 
substances  of  a  bad  smell  or  taste.  The  nitrogen  must  not  exceed  a  certain  limit. 
Marcker  found  in  the  highest  quality  of  barley  from  the  Saale  an  amount  of  proteine  not 
exceeding  9  or  9^  per  cent.  100  barley  grains  weigh  from  3  to  5-26  grammes.  The 
best  barley  contains  6|  per  cent,  of  husk ;  other  qualities  up  to  24/2  per  cent. 

Barley  for  distilling  must  have  coats  of  a  very  uniform  thickness.  It  should  have 
a  high  percentage  of  proteine,  which  is  converted  into  diastase,  capable  of  transforming 
starch  into  maltose  and  dextrine. 

For  judging  the  quality  of  a  barley  for  brewing  a  high  germinating  power  is  required. 
A  good  barley  should  have  a  germinating  power  of  from  88  to  90  per  cent.  The  barley 
should  also  grow  uniformly.  The  weight  of  the  grains  and  their  degree  of  clearness 
should  also  be  regarded.  A  germinating  bed  is  prepared  as  follows  : — Fine  sand,  which 
has  been  previously  ignited,  is  laid  upon  a  plate  so  high  as  to  touch  the  upper  margin 
of  the  cavity  of  the  plate.  So  much  water  is  added  that  the  sand  on  shaking  moves 
loosely.  So  much  more  sand  is  then  sifted  evenly  over  the  surface  as  to  stiffen  the  whole. 
The  sand  is  then  smoothed  off  level  with  the  edge  of  the  plate,  and,  after  sowing,  it  is 
covered  with  a  second  plate. 

Hops. — The  hop  (Humulus  lupulus)  is  a  disecious  plant  of  the  natural  order  of 
Urticacece,  the  female  flowers  of  which,  or  catkins,  are  used  for  flavouring  beer.  The 
catkins,  or  strobils,  are  composed  of  a  number  of  bracts  or  scales,  which  are  green, 
afterwards  changing  to  a  pale  yellow.  At  the  base  of  each  flower  is  seated  the  pistil 
containing  the  seed,  while  surrounding  the  pistil  are  a  number  of  little  grains,  embedded 
in  a  yellow  powder,  the  farina,  containing  the  active  property  of  the  hop,  essentially 
lupuline,  the  grains  being  termed  lupulinic  grains.  This  yellow  pulverulent  substance 
contains  an  essential  oil,  tannic  acid,  and  mineral  constituents.  The  essential  oil,  the 
flavouring  principle  of  the  hops,  is  found,  in  air-dried  hops,  to  the  amount  of  o-8  per 
cent.  ;  it  is  yellow-coloured,  with  an  acrid  taste,  without  narcotic  effect,  of  a  sp.  gr. 
=  0-908,  turning  litmus-paper  red.  It  requires  more  than  600  times  its  weight  of 
water  to  effect  a  solution.  It  is  free  from  sulphur,  and  belongs  to  the  group  of  essential 
oils  characterised  by  the  formula  C5H8,  and  can  become  oxidised  under  contact  with 
the  air  into  valerianic  acid  (C5H10O,,),  this  oxidation  being  the  cause  of  the  peculiar 
cheesy  odour  of  old  hops ;  it  is  a  mixture  of  a  hydrocarbon,  C5H8,  isomeric  with  the 
oils  of  turpentine  and  rosemary,  with  an  oil  containing  oxygen,  C10H180,  having  the 
property  of  oxidation  alluded  to.  Tannic  acid  is  found  in  the  several  kinds  of  hops,  in 
quantities  varying  from  2  to  5  per  cent.,  and  is  an  important  constituent,  as  it  pre- 
cipitates the  albuminous  matter  of  the  barley  and  serves  to  clear  the  liquor.  It  gives 
with  the  per-salts  of  iron  a  green  precipitate  ;  treated  with  acids  and  synaptase,  it  does 
not  separate  into  gallic  acid  and  sugar ;  and  by  dry  distillation  it  does  not  give  any 
pyrogallic  acid.  The  hop  resin  is  the  important  constituent  of  the  hops,  and  contains 
the  bitter  principle  or  lupuline.  It  is  difficultly  soluble  in  water,  especially  in  pure 


SECT.  vi.'J  BEER  BREWING.  737 

water,  and  when  the  lupuline  or  essential  oil  is  absent.  But  water  containing  tannic 
acid,  gums,  and  sugar  dissolves  a  considerable  quantity  of  the  resin,  especially  when  the 
essential  oil  is  present.  It  is  intensely  bitter  in  taste,  and  becomes  foliated  when 
exposed  to  the  atmosphere.  Hop  resin  and  the  essential  oil  are  not  identical ;  the 
former  is  soluble  in  ether,  the  latter  is  not.  In  the  course  of  long  exposure  it  becomes 
insoluble.  The  gum  and  extractive  colouring  matter  are  of  little  use.  The  mineral 
constituents  of  hops  dried  at  100°  are — 9  to  10  per  cent,  ash,  15  per  cent,  phosphoric 
acid,  17  per  cent,  potash,  &c. 

Quality  of  the  Hops. — The  quality  of  the  beer  is  almost  proportionate  to  the  quality 
of  the  hops.  A  rich  soil  is  required  for  the  growth  of  the  hop-plant,  well  exposed  to 
the  influence  of  the  sun's  rays,  and  protected  from  easterly  winds,  which  are  highly 
detrimental.  The  hops  must  on  no  account  be  gathered  until  the  seed  is  perfectly  ripe, 
as  it  is  only  then  that  the  bitter  principle  is  fully  developed.  The  ripeness  of  the  hops- 
can  be  ascertained  by  rubbing  them  between  the  fingers ;  if  an  oily  matter  remains, 
with  a  strong  odour,  they  are  fit  for  gathering.  When  gathered,  the  next  most  impor- 
tant operation  is  the  drying,  which  is  effected  in  kilns  or  stoves,  at  a  temperature  of  40°, 
with  a  good  ventilation.  When  sufficiently  dried,  the  small  stem  attached  to  the 
flower  snaps  readily.  The  temperature  must  be  carefully  regulated  :  not  permitted  ta 
range  so  high  as  to  run  the  risk  of  burning  the  hops,  nor  allowed  to  fall  so  low  that 
the  hops  may  afterwards  become  mouldy  from  under-drying.  When  dried,  the  hops 
are  carefully  packed,  the  finer  kinds  being  put  into  canvas  pockets,  and  the  inferior 
into  hop-bags  of  a  coarser  texture.  The  bags  are  then  subjected  to  slight  pressure  in 
a  hydraulic  or  screw  press,  to  render  them  more  impervious  to  air.  To  preserve  the 
hops  they  are  sometimes  sulphured,  that  is,  subjected  to  the  action  of  vapours  of 
burning  sulphur,  i  to  2  Ibs.  of  sulphur  being  employed  to  i  cwt.  of  hops.  Old  hops- 
are  sometimes  treated  in  this  manner,  to  impart  the  colour  and  appearance  of  freshly 
dried  hops,  but  the  fraud  can  be  detected  by  the  odour.  A  good  method  of  testing 
for  sulphur  in  hops  is  as  follows  : — A  sample  of  the  hops  is  placed  in  a  sulphuretted 
hydrogen  apparatus,  with  some  zinc  and  hydrochloric  acid ;  the  disengaged  gas  is  passed 
through  a  solution  of  acetate  of  lead.  If  the  hops  contain  sulphurous  acid,  sulphu- 
retted hydrogen  will  be  disengaged  (S02  +  2H2  =  SH2  +  2H20),  and  lead  sulphide  will  be 
thrown  down  from  the  lead  solution.  Another,  and  still  better,  method  is  to  receive 
the  disengaged  gas  in  a  solution  of  sodium  nitroprusside,  to  which  a  few  drops  of 
potash-lye  have  been  added ;  the  slightest  trace  of  sulphuretted  hydrogen  imparts  a 
beautiful  purple-red  colour  to  the  solution. 

Substitutes  for  Hops. — Attempts  have  been  made  to  substitute  quassia,  walnut  leaves, 
wormwood,  gentian,  extract  of  aloes,  colchicum,  and  picric  acid  for  the  hop.  None  of 
these  substances  are  efficient  substitutes  for  the  hop,  though  they  impart  a  strong,  bitter 
flavour.  Three  of  them  may  be  considered  as  poisonous.  There  was  no  foundation 
for  the  report  that  the  seeds  of  a  species  of  strychnos  (and  even  ready  prepared 
strychnine)  were  used  in  brewing  bitter  ales. 

The  water  used  in  steeping  the  barley,  extracting  the  malt,  and  mashing  has  a 
great  influence  upon  the  quality  of  the  beer.  A  pure,  soft  water,  or,  at  the  most,  one 
very  slightly  hard,  is  best  suited  for  the  purposes  of  the  brewer. 

Water  contaminated  with  decomposing  organic  matter  is  especially  objectionable. 
Such  substances  cling  to  the  barley,  continue  to  decompose  on  the  softening  floor, 
occasion  mouldiness  and  putridity,  and,  under  some  circumstances,  interfere  with 
the  fermentation  of  the  wort  obtained  from  such  malt.  Tannic,  crenic,  and  apocrenic 
acids  have  an  injurious  action  ;  hence  water  from  woodlands,  and  that  of  rivers  which 
receive  the  waste  of  tanneries,  are  to  be  used,  if  at  all,  with  caution.  Beer  made  with 
water  containing  animal  impurities  Avill  not  keep.  The  entrance  of  the  waste  waters 
of  the  brewery  is  often  manifested  by  disturbance  in  the  process  of  fermentation. 

3  A 


738  CHEMICAL   TECHNOLOGY.  [SECT.  vi. 

Lintner  points  out  that  the  water  used  for  softening  the  barley  and  filling  the  casks 
should  contain  little  organic  matter,  and  especially  no  ferment  organisms.  As  regards 
the  primary  decomposition  products,  ammonia  and  nitrous  acid,  Lintner  remarks  that 
as  we  justly  view  with  suspicion  water  containing  such  impurities,  and  reject  it  for 
dietetic  use,  so  also  in  malting  and  brewing  it  should  be  used  only  in  extreme  cases  and 
with  great  caution.  A  malting-house  which  used  such  water  for  softening  had  always 
to  contend  with  mouldiness  in  the  malt,  which  disappeared  as  soon  as  it  was  found 
possible  to  get  a  better  supply  of  water.  "Water  containing  calcium  carbonate  is  good 
for  malting ;  calcium  and  magnesium  chlorides,  gypsum,  and  iron  are  injurious. 
The  brewing  of  beer  may  be  considered  to  consist  of  the  following  operations  : — 

(1)  The  malting. 

(2)  The  mashing. 

(3)  The  fermentation  of  the  beer- worts  and  the  fining,  ripening,  and  preserva- 

tion of  the  beer. 

i.  The  Malting. — Malting  is  the  process  during  which  the  grain — barley — is 
germinated,  by  means  of  steeping  in  water  until  it  swells  and  becomes  soft.  The  non- 
germinated  grain  possesses  only  in  a  very  small  degree  the  property  of  changing  its 
starch  into  sugar  (dextrose) ;  this  property  is  very  fully  developed  during  the  germina- 
tion, so  much  so  that  it  would  be  an  easy  matter  to  distinguish  between  the  germinated 
and  non -germinated  seed  by  the  degree  of  this  property  alone.  As  has  been  already 
stated,  barley  is  the  grain  preferred,  on  account  of  its  forming  sugar  in  larger 
quantities  than  any  other  kind  of  grain.  The  germination  of  the  seed  takes  place  in 
three  well-marked  periods.  In  the  first,  the  seed  is  enveloped  in  an  outer  organ, 
which  becomes  exhausted  and  withered.  In  the  second,  the  growth  of  the  germ  is 
shown  by  the  swelling  at  the  end  by  which  it  was  attached  to  the  stalk ;  and  in  the 
third  period,  the  little  plumule,  or  acrospire,  which  would  form  the  stem  of  the  new 
plant,  is  put  forth.  The  germinating  seed  is  similar  to  an  egg,  with  its  white,  yolk, 
and  embryo ;  the  shell  corresponds  with  the  outer  or  hard  coating  of  the  seed ;  the 
white  and  yolk  of  the  egg  appear  as  the  albumen,  or  meal  of  the  grain ;  while  the 
embryo  of  the  egg  has  its  analogue  in  the  germ  of  the  grain.  A  remarkable  change 
takes  place  during  germination ;  the  glutinous  constituent  has  passed  from  the  body 
of  the  grain  to  the  radicula,  or  rootlet,  which  has  grown  to  nearly  the  length  of  the 
grain,  while  about  one-half  of  the  starch  has  been  converted  into  sugar.  This  conver- 
sion is  the  aim  of  the  malting,  as  by  this  means  the  sugar  can  be  readily  dissolved. 
The  grain  is  supposed  to  have  been  sufficiently  treated  when  the  plumule,  or  acrospire, 
has  attained  a  length  equal  to  two-thirds  of  the  entire  length  of  the  grain.  The 
operation  of  germination  is  the  same  with  all  kinds  of  grain  employed  in  brewing. 
The  conditions  of  success  are — the  saturation  of  the  grain  with  moisture,  and  a 
temperature  of  not  higher  than  40°  nor  lower  than  4°,  with  access  of  air  and  exclusion 
of  light. 

(a)  The  Softening  or  Soaking  of  the  Grain  is  accomplished  in  large  cisterns  of  wood, 
sandstone,  or  cement,  half  filled  with  water.  The  grain  is  poured  into  the  water,  and, 
after  the  lapse  of  an  hour  or  so,  sinks  to  the  bottom  of  the  tank,  only  the  inferior  and 
diseased  seed  remaining  on  the  surface,  to  be  removed  with  wooden  shovels,  and 
thrown  aside  for  use  as  fodder  for  horses,  cattle,  &c.  The  steep  water  receives  the 
soluble  constituents  of  the  husk  of  the  seed,  and  becomes  of  a  brown  colour  and 
peculiar  flavour,  with  a  decided  inclination  to  lactic,  butyric,  and  succinic  acid 
fermentation.  The  duration  of  the  softening  varies  according  to  the  age  of  the  grain, 
the  temperature  of  the  water,  &c.  A  young,  fresh  grain  requires  forty-eight  to  seventy- 
two  hours'  soaking,  while  an  older  grain,  containing  more  gluten,  is  not  thoroughly 
softened  under  six  to  seven  days.  Grains  of  equal  age  and  constitution  must  be  soaked 
together,  to  obtain  an  equally  softened  product.  After  sufficient  soaking,  the  grain 


.SECT,  vi.]  BEER   BREWING.  739 

is  allowed  to  drain  for  eight  to  ten  hours,  then  taken  out  and  thrown  into  heaps 
on  the  floor  of  the  malt-house.  The  sufficiency  of  the  soaking  is  ascertained — (i) 
By  pressing  the  grain  between  the  finger  and  thumb-nail,  when,  if  sufficiently 
moistened,  the  germ,  or  embryo,  will  be  projected.  (2)  The  husk  is  easily  destroyed 
by  pressure  between  the  fingers.  (3)  When  crushed  with  a  piece  of  wood  the  grain 
yields  a  floury  mass.  The  grain  when  softened  has  a  peculiar  aroma,  resembling 
that  of  apples.  The  quantity  of  water  usually  absorbed  by  the  barley  amounts  to 
40  to  50  per  cent,  of  its  weight,  while  the  grain  correspondingly  increases  in  volume 
1 8  to  24  per  cent.  During  this  absorption  the  grain  loses  1*04  to  2  per  cent,  of 
its  own  weight  in  solid  matter.  Lermer  states,  that  in  fresh  steep  water  he  has 
found  succinic  acid  in  the  proportion  of  30  grammes  to  i  bushel  of  grain  soaked . 

(b)  The   Germination   of  Softened   Grain. — As   soon   as   the  grain  is    thoroughly 
saturated   with    moisture,    the    conversion    of    the    starch   into   sugar    commences. 
When  germination  has  proceeded  far  enough  it  must  be  stopped,  as  about  this  time 
the  formation  of  sugar  has  reached  a  maximum.      The  softened  barley  is,  as  before 
stated,  transferred  to  the  floor  of  the  malting-room,  where  it  is  "  couched,"  or  placed 
in  a  layer  of  4  to   5   inches  in  thickness.     Here  the   germination  proceeds  till  the 
plumules  have  attained  the  desired  length.     The  temperature  rises  some  6°  to  10° 
on  account  of  the  heat  developed  during  germination,  and  consequently  much  of  the 
moisture  is  dissipated.      The  chief  art  of  the  maltster  consists  in  stopping  the  ger- 
mination at  that  point  when  the  plumules  and  roots  commence   to   draw  upon  the 
constituents  of   the    grain.      The   duration  of   the   germination   varies,  during   the 
warmer  months  of   the    year,  from  seven  to  ten  days,  while   towards  autumn  the 
process  will  not  be  completed  under  ten  to  sixteen  days,  but  the  average  duration 
is  eight  days.     The  grain,  during  germination,  loses  about  2  per  cent,  of  its  weight, 
probably  by  the  oxidation  of  the  carbon  to  carbonic  acid  by  the  oxygen  of  the  air. 

(c)  The  Drying  of  the  Germinated  Grain. — The  grain  is  now  removed  to  the  drying 
floor  (Welkboden},  where  it  is  exposed  to  the  air  in  layers  3  to  5  centimetres  in  depth,  and 
turned  about  with  rakes  six  to  seven  times  daily.     When  the  malt  becomes  dry  it  is 
cleared  from  the  rootlets,  some  of  which  drop  off  by  themselves,  while  others  have  to 
be  removed  by  winnowing.     Malt  must  be  dried  for  the  making  of  most  kinds  of  beer, 
and  has  to  undergp  a  roasting  process  before  quite  fitted  for  use.     This  drying  or 
roasting  is  effected  in  a  malt  kiln  or  cylinder  heated  by  flues  to  the  boiling-point  of 
water.     During  the  roasting  the  malt  acquires  a  darker  colour,  due  to  the  conversion 
of  the  remainder  of  the  starch  into  sugar.     The  equality  of  the  temperature  is  of  the 
utmost  importance,  so  that  one  part  of  the  malt  may  not  be  more  strongly  heated  than 
.another.     Before  the  malt  is  submitted  to  this  operation,  however,  it  is  first  heated  to 
30°  or  40°.     By  this  means  some  of  the  starch  is  converted  into  gluten,  and  forms  a 
•coating  to  the  grain  impervious  to  water,  the  malt  being  in  this  stage  known  as  "bright" 
malt  from  its  smooth,  glossy  appearance. 

The  malt  kilns  consist  essentially  of  the  drying  plates  upon  which  the  malt  is  laid, 
.and  the  heating  flues.  The  plates  used  to  be  of  stone  or  sheet-iron,  but  modern 
brewers  employ  wire-wove  frames,  placed  one  above  the  other,  so  that  the  hot  air  from 
the  flues  beneath  may  ascend  through  the  interstices.  The  flues  are  generally  of 
sheet-iron  for  the  better  conduction  of  heat  to  the  surrounding  atmosphere.  Coke  is 
used  as  fuel  on  account  of  the  absence  of  smoke,  as  with  coal  or  wood,  in  the  event  of 
a  leakage  in  the  flues,  considerable  damage  would  be  done  to  the  malt. 

The  malt  is  not  all  dried  at  the  same  heat  (50°  to  100°  C.),  but  is  distinguished 
as  pale,  amber,  brown,  or  black  malt,  according  to  the  degree  of  heat  to  which  it  has 
been  exposed.  Pale  malt  results  from  heating  to  33°  to  38° ;  amber,  from  a  tem- 
perature of  49°  to  52°  ;  and  brown  from  the  rather  high  temperature  of  65-5°  to  76-5°. 
Black  malt,  commonly  called  patent  malt,  is  prepared  by  roasting  in  cylinders,  like 


74o  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

coffee  cylinders,  at  a  temperature  of  163°  to  220°.     These  darker  malts  are  used  in 

England  for  colouring  porters  and  stouts. 

100  parts  of  barley  give  92  parts  of  air-dried  malt.      The  loss  of  8  parts  may  be  thus 

accounted  for : — 

In  the  steep- water i'S 

During  malting 3'° 

During  germination 3'° 

Other  losses •        °'5 

Total  loss .        .        8-0 

The  moisture  in  air-dried  malt  amounts  to  12  to  15*2  per  cent.,   and  is  expelled 
during  the  kiln  drying.    According  to  C.  John  (1869),  100  parts  of  dried  barley  give — 

I.  II. 

Malt         ...        .        83-09  85-88 

Plumules          .        .        .          3-56  ...  3-09 

Eadicules  (rootlets)          .          4-99  ...  4-65 

Fermentary  products      .-          8-36  ...  6-38 


The  change  undergone  during  the  drying  or  roasting  of  the  malt  is  shown  in  the 
following  table,  the  result  of  Oudeman's  analyses  : — 

Air-dried  Malt.  Kiln-dried  Malt.        Strongly  Dried  Malt 

Products  of  roasting     .  o'o  ...  7'8  ...  I4'O 

Dextrine        .                 .  8'O  ...  6'6  ...  IO'2 

Starch  ....  58-1  ...  58^6  ...  47'6 

Sugar  0-5  ...  07  ...  0-9 

Cellulose       .        .        .  14-4  ...  io-8  ...  11-5 

Albuminous  matter       .  iy6  ...  10-4  ...  io'5 

Fat         ....  2-2  ...  2-4  ...  2'6 

Ash        ....  3-2  ...  27  ...  27 

The  amount  of  sugar  is  undoubtedly  increased  during  the  process ;  and  the  dextrine 
appears  to  increase  with  decrease  of  starch,  and  vice  versd.  The  conversion  of  starch 
into  dextrine  and  sugar  is  effected,  as  far  as  is  known,  by  the  agency  of  diastase. 
Dubrunfaut  has  (1868)  shown  that  malt  presents  another  sukstance  similar  in  its 
effect  to  diastase,  and  which  he  termed  maltin.  This  principle  is  found  to  be  much 
more  active  than  diastase,  so  that  with  the  same  quantity  of  maltin  which  a  known 
quantity  of  malt  contains,  ten  times  as  much  beer  can  be  obtained  as  when  diastase 
only  is  employed.  Dubrunfaut  has  also  found  a  second  but  less  active  substance.  Its 
behaviour  with  respect  to  the  decomposition  of  starch  is  similar  to  that  of  diastase ; 
malt  contains  i|  per  cent.,  while  only  i  per  cent,  of  maltin  is  found.  The  treatment 
with  alcohol  necessary  to  obtain  diastase  destroys  the  maltin.  Dubrunfaut  believes 
diastase  to  be  only  a  less  active  modification  of  these  new  substances. 

The  author  is  of  opinion  that  the  building  in  which  the  process  of  germination  is 
conducted  may  have  its  windows  advantageously  constructed  of  violet  glass. 

The  combustion  value  of  i  kilo,  of  starch  is  =  4200  heat-units.  For  100  kilos,  of 
dry  malt  there  will  be  evolved  during  the  process  of  germination  6"j  x  4200=  28,100 
heat-units. 

Pneumatic  Malting. — In  order  to  remove  the  carbon  dioxide,  which  interferes  with 
germination,  and  to  prevent  an  excessive  rise  of  temperature,  so-called  pneumatic  malt- 
ing has  been  devised.  Galland,  e.g.,  in  his  pneumatic  maltings  keeps  the  air  moist 
by  means  of  a  tower  (Fig.  5 14),  which  contains  coke  resting  on  the  gratings,  b  and  c. 
The  air,  previously  heated,  enters  through  the  pipe  a,  ascends  to  meet  the  descending 
water  through  the  bed  of  coke,  and  passes  through  C  into  the  recipients,  A  and  E, 
which  contain  the  barley.  The  requisite  water  is  let  into  the  cistern,  w,  through  a 


SECT. 


VI.] 


BEER  BREWING. 


74i 


Fig.  514. 


Fig.  SIS- 


cock,  J,  flows  through  the  overflow,  y,  to  the  sprinkling  apparatus,  r,  and  then  down- 
wards. In  order  to  use  the  water  over  again,  it  is  lifted  by  the  pump,  //,  below  the 
filter,  k,  through  which  it  rises  to  the  cistern,  10.  In  the  softening-beck,  A ,  there  is  a 
perforated  false  bottom,  d.  The 
barley  to  be  malted  is  softened 
in  this  beck  for  forty-eight  to 
sixty  hours  in  water.  When 
the  water  is  removed  the  grain 
soon  begins  to  sprout.  Contrary 
to  the  present  process,  it  is  left 
undisturbed  for  two  or  three 
days,  the  softening-beck  being 
meantime  kept  closed  with  a 
plate.  In  order  to  remove  the 
heat  which  is  evolved,  fresh  air 
is  conveyed  to  the  barley  through 
the  pipe  B,  which  escapes  through 
the  pipe  D.  The  sprouted  grain 
falls  through  the  hopper,  t,  and 
the  aperture,  o,  into  the  drum, 
E  (Fig.  515).  This,  consists  of 
a  sheet-iron  cylinder,  closed  at 
both  ends.  The  partition,  s,  is 
provided  with  openings,  d,  with 
which  are  connected  the  channels 
€,  made  of  sieve-plate.  The  air 
entering  at  /  arrives  from  the 
ante-chamber,  N,  in  the  channels 
JE,  traverses  the  barley,  and  is 

drawn  off  by  the  intermediate  sieve -tube,  and  the  main,  S.  The  drum  is  continually 
turning  on  the  rollers,  G.  The  movement  can  be  effected  in  various  manners — e.g.,  as 
in  Fig.  515,  by  an  endless  screw,  V,  which  plays  into  a  circuit  of  cogs.  During  the  first 
four  days  after  introduction  into  the  drum,  E,  fresh,  moist  air  is  continually  supplied 
to  the  barley  from  the  coke-tower  through  the  pipe  P.  As  soon  as  the  germination 
is  retarded,  there  is  supplied  for  two  days  a  suitable  mixture  of  fresh,  moist,  and 
warm  air,  the  latter  coming  from  a  hot-air  chamber  through  an  opening  in  the  tubing, 
P.  Then  dry  air  at  50°  is  allowed  to  enter,  and  the  temperature  is  gradually  raised 
until  the  malt  is  ready. 

In  Leicht's  malt  kiln  (Fig.  516)  the  combustion  gaees  pass  from  the  fire  a,  through 
the  flues  b,  beneath  the  preliminary  air-heaters,  to  the  flues  c,  in  which  case  the 
movable  dampers  A,  B,  and  D  are  closed,  whilst  E  is  open ;  from  the  flue  c,  the  fire- 
gases  pass  through  the  iron  flues  d,  to  the  common  duct,  e,  and  if  the  damper  F  is 
closed  and  G  is  open,  through  the  flue  f,  to  the  vapour  chimney  h.  Inversely,  the 
combustion-gases  from  the  fire  al  take  their  way  through  the  flues  bv  cv  whilst  the 
dampers  A ,  B,  and  E  are  closed,  and  D  is  open,  to  dv  e  ;  and,  further,  if  G  is  closed 
and  F  open,  to  6P  and  then  to  the  vapour  chimney  hv  in  the  direction  indicated  by 
the  dotted  arrows.  By  alternately  opening  and  closing  the  dampers  A,  D,  and  B,  E,  the 
combustion-gases  can  be  led  from  the  fires,  a  or  av  directly  into  the  chimney  above, 
whereby  the  roasting  of  the  malt  on  each  floor  is  assisted.  Further,  the  escaping 
gases  can  be  led  either  to  h  or  hv  by  opening  and  shutting  dampers  F  and  G,  in 
order  to  promote  the  draught  in  the  required  direction,  according  as  the  drying  is 
conducted  on  H  or  Hr  In  practice  this  is  done  alternately  day  by  day,  one  flue  being 


742 


CHEMICAL   TECHNOLOGY. 


[SECT.  vi. 


used  for  drying  and  one  for  roasting.     If  H  is  used  for  drying,  the  fire  a  and  the^ 
preliminary  heating  chamber  are  active,  and  the  draught  is  accelerated  by  the  heated 

chimney  h,  whereby  the 
temperature  on  the  floor 
II  remains  moderate  even 
with  the  strongest  fire, 
whilst  the  radiant  heat  is 
given  off  in  the  flues  d  for 
roasting  on  the  floor  Hv 

If  the  temperature  on 
the  floor  7/x  is  not  sufficient 
for  roasting,  the  fire  al  is 
used  in  assistance,  with  the 
open  dampers  B  and  E,  so 
that  the  fire  gases  may  pass 
directly  into  the  flues  d. 

In  a  trial-malting  all 
the  samples  of  barley  are 
steeped,  malted,  and  dried: 
under  identical  conditions. 
The  barley,  freed  as  far  as 
possible  from  stones,  the 
seeds  of  weeds,  oats,  &c.r 
is  weighed,  washed  till  the 
water  runs  off  clean,  and 
then  steeped  in  a  cylin- 
drical glass  with  an  equal  weight  of  water.  After  some  hours  the  floating  grains  are 
taken  off,  air-dried,  and  weighed.  The  steeping  water  is  changed  every  twenty- 
four  hours,  at  a  maximum  temperature  of  15°  in  the  room,  and  is  replaced  by  an  equal 
quantity  of  water.  After  the  barley  has  reached  the  right  degree  of  softness  it  is 
spread  on  a  horse-hair  sieve  in  a  layer  6  to  8  centimetres  in  height.  Each  sieve  is  laid 
over  a  flat  vessel  containing  water,  and  covered  with  a  wet  cloth.  In  these  experi- 
mental maltings  on  the  small  scale  it  is  necessary  to  free  the  barley  from  dust  before 
steeping,  rubbing  the  grains  cautiously  in  water  with  the  fingers  or  on  a  cloth,  as 
otherwise  mouldiness  would  set  in.  The  malt  is  then  weighed  and  spread  on  a  small 
square  drying-floor  heated  with  gas,  where  it  remains  twenty -four  hours.  The  drying 
takes  twenty-four  hours  at  a  maximum  temperature  of  36° ;  the  heat  is  gradually 
raised,  and  the  malt  is  finally  roasted  at  80°  for  five  hours. 


.» 

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M 

sj 

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a 

be 

88? 

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a 

1g  S  g 

Origin. 

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«Jfl 

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•2-S 

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\S  (»"(§. 

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H 

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Q)   .^3 

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If 

'o 

^   O 

SS3 

p.  c. 

mgrm. 

p.  c. 

hours. 

days. 

hours. 

p.  c. 

p.  c. 

p.  e. 

p.  c. 

Hungary  . 

85-87 

37^4 

073 

75 

II  'OO. 

41 

148-1 

83-2 

5'79' 

91-27 

Slavonia  .                 .         . 

87-03 

38-02 

0-44 

92 

9-40' 

34 

153-1 

84-4 

6-55 

90-62 

Regensburg 

84-65 

41-17 

1-28 

79 

8-90 

47 

157-3 

81-0 

4-80 

91-09 

Bohemia  . 

86-31 

44-50 

0-82 

74 

8-90 

38 

83-3 

5  '40 

91-30 

Franconia 

82-35 

47-40 

1-40 

95 

10-25 

57 

146-4 

78-5 

4-72 

90-82 

Saale 

86-56 

43-60 

0-56 

73 

933 

48 

153-7 

83-3 

5  '42 

9I'OI 

Moravia    . 

86-70 

38;65 

1-34 

94 

9-25 

46 

158-2 

80-8 

5'°7 

89-17 

Sweden    . 

81-69 

1-14 

92 

11-05 

92 

152-9 

79-6 

92-86 

SECT.    VI.] 


BEEE   BREWING. 


743 


The  nitrogen  of  the  barleys  and  the  malts  obtained,  with  the  constituents  of  the  ash, 
amounted  to — 


Barleys. 

i. 

2. 

3- 

4- 

5- 

6. 

7- 

8. 

N    

1-809 
2-690 

0-599 
I  -010 

0-056 
0-009 

I-629 
2-64O 
0-67I 
0-790 

0-059 
0-013 

1*877 
2-850 
0-656 
I-078 

0-065 

0-016 

I*809 
2*570 
0-65I 
0-923 
0*082 
0-062 
0-23I 
O-OI5 
0-3I5 

1-859 
2-810 
0-826 
0798 
0-147 
0-059 
0*229 
O-O07 
0-608 

1-696 
2-860 

0*579 
0-8I7 

0-037 

0*216 
0*013 
0-528 

1750 
2-650 
0-645 
0-804 

0-640 
O-009 

1-605 
2-630 
0-711 
0-767 
0-107 
0-067 
0-224 
0-003 
0-592 

Ash          .... 

Si02         

P,0e 

SO,  . 

CaO         .... 

MgO        

Fe,03       
K20          

N    . 
Ash 
Si02 
PA 
SO3 
CaO 
MgO 
Fe208 
K2O 

Malts. 

1-625 
2*480 
0-598 
0-929 
0*029 
O-O9I 
0-253 
O'O22 
0-468 

ir6oo 
2-390 
0-711 
0-868 
0-054 
0-072 
0-266 
0*018 
0-363 

1-857 
2-440 
0-677 
0-904 
0*012 
0-087 
0-236 
0-019 
0-470 

1-798 
2-300 
0^644 
0-708 
O-O29 
0-077 
O-2I9 
O-OI4 
0-367 

1729 
2-420 
0-725 
0-779 
0-012 
0-084 
0-239 
0-017 
0-385 

1*568 
2-350 
0-556 
0-784 

0-019 

0*096 

0*239 

0*011 

0-417 

1733 
2*320 
0*770 
0-830 
0-03I 
0-085 
0-2.19 
0-015 

I-4I3 
2-310 
0-651 
0-693 
0-058 
0-082 
O'2I2 
O-OI5 
0-407 

It  is  seen  how  different  is  the  loss  in  the  several  constituents  of  barley  on  malting. 
One  part  of  the  loss  is  due  to  the  .steeping  water,  which  has  a  lixiviating  action. 
Another  part  consists  of  the  matters  removed  in  the  germs.  Though  the  Munich 
water  used  in  the  experiments  was  not  very  hard,  it  did  not  extract  any  lime,  but  yielded 
some  to  the  grain. 

Balke  examined  several  specimens  of  barley  of  the  season  1883,  and  of  the  malts 
obtained  from  them.  He  obtained  in  percentages — 


Barley. 

Dry  Substance. 

Origin. 

Dry 

Substance. 

Starch 
Value. 

Proteine 
NX  6-25. 

Ash. 

P205  in 

Ash. 

Germ-power. 

Per  cent. 

Per  cent. 

Moravia,  I. 

84-84 

64-8 

8-89 

2-77 

31-82 

98-0 

Moravia,  II. 

85-82 

69-2 

9-68 

2-76 

35-I4 

95-0 

Silesia 

85-I9 

63-2 

10-71 

3'02 

20-54 

84-0 

Magdeburg 

8477 

68-9 

1077 

2-56 

37-19 

96-0 

Stumsdorff 

8775 

71-4 

10-07 

3-08 

2875 

95-8 

Coethen 

84-84 

69-9 

10-16 

2*58 

37-80 

97-5 

Malt. 

Dry  Substance. 

Extract. 

Origin. 

Dry 

Substance. 

Extract. 

Proteine 
NX  6-25. 

Ash. 

P205  in 
Ash. 

Maltose. 

Maltose  : 
Non-mal- 
tose=i. 

Moravia,  I.                                   .91*18 
Moravia,  II.                                 .       92*22 
Silesia        .                                  .       89*35 

75-54 
73-68 
75-26 

II79 
9-40 

8-53 

2-65 
2-8S 
2-48 

38-50 
32-I8 
37'35 

Per  cent. 
69-50 
72-30 
6872 

0-46 
0-39 
0-45 

Magdeburg 
Stumsdorff 

89-34 
93-30 

72-90 
76-19 

10-44 
10-25 

2*39 
2-39 

40-00 

7271 
70-23 

0-38 
0-31 

Coethen    . 

93-20 

74-93 

9-94 

2-49 

70-63 

0-31 

The  proportion  of    soluble  nitrogenous    constituents   of    different  malts  in   per- 
centages of  the  dry  matter  amounted,  according  to  Salamon  (1886),  to — 


744 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


Origin. 

Total 
Nitrogen. 

Albuminoid 
Nitrogen. 

Peptonic 
Nitrogen. 

Amidic 

Nitrogen. 

Unknown 

Nitrogen. 

England,  good  . 

0-6148 

O-I2OO 

0-0340 

0-4090 

0*05490 

England,  ordinary 

0-6167 

0-I44I 

0-0074 

0-3804 

0-08490 

Scotland    . 

0-5404 

0*0514 

0-0149 

0*4025 

0*07160 

France 

07147 

I  -0470 

0*0624 

0*5000 

0*07476 

Denmark    .        .    • 

0-7111 

0-1393 

0-0634 

0*5084 

Moravia 

0-6159 

0-1435 

0-0438 

0-4286 

Or  in  percentages  of  total  nitrogen — 


England,  I  
England,  II  

I9-5I 
2V^6 

5'53 

I  -2O 

66-02 
6  1  -68 

8-94 
1-7-76 

Scotland  
France  
Denmark  
Moravia  

9-5I 
14-64 

I9'59 
23-30 

275 
873 
8-91 
7*11 

76-33 
69-95 
71-50 

69-59 

11*41 
6-68 

According  to  Lintner  and  Aubry,  good  malt  should  yield  an  extract  of  at  least  7 1 
per  cent,  of  its  dry  substance.  In  the  extract  there  should  be  64  to  69  per  cent, 
maltose,  and  hence  the  proportion  of  maltose  to  non-maltose  in  the  extract  should  be 
as  i  :  0*45  to  i  :  0*55.  If  the  proportion  is  higher,  say  i :  0*30,  the  beers  ferment 
too  strongly  and  bear  little  head  ;  if  it  is  lower,  as  i  :  0*60,  there  is  too  little  maltose  in 
the  wort,  and  the  fermentation  is  feeble.  These  proportions  are  doubtless  correct 
for  the  full-bodied  Bavarian  beers,  but  in  malts  for  the  light  and  vinous  North  German 
beers  the  most  favourable  proportions  of  maltose  to  non-maltose  in  the  extract  are 
1  :  °'35  to  i  :  0*47,  the  maltose  in  the  extract  being  68-75  per  cent.  Practice  shows 
that  such  malts  yield  normal  worts,  fine  fermentations,  and  beers  of  a  good  flavour. 
A  further  character  which  Lintner  and  Aubry  demand  in  a  good  malt  has  been  fully 
confirmed — i.e.)  a  good  malt  should  be  completely  saccharified  in  twenty  minutes,  if 
mashed  at  70°. 

The  object  of  the  malting  process  is  to  form  a  non-organised  ferment,  diastase,  at  the 
expense  of  the  nitrogenous  constituents  of  the  barley.  This  starch,  in  the  subsequent 
mashing  process,  splits  up  the  starch  into  maltose  and  dextrine.  According  to 
Zulkowsky  (1878),  the  mean  composition  of  a  purified  diastase  obtained  from  barley 
malt  is — 

Carbon 45  "57 

Hydrogen 6*49 

Nitrogen 5*14 

Ash 3-16 

Oxygen  and  sulphur 37*64 

A  second  non-organised  ferment,  generated  during  the  malting  process,  is  peptase, 
which  during  mashing  converts  the  protein  compounds  into  peptones  and  para-peptones. 
A  part  of  the  constituents  of  the  gluten,  the  parenchyma  in  which  the  starch  granules 
are  embedded,  is  rendered  soluble  or  much  loosened.  The  starch  is  so  modified  that 
it  is  turned  into  paste  at  a  lower  temperature. 

The  Production  of  the  Wort. — In  Bavaria,  the  Schenk,  or  pot  beer,  is  brewed  in  the 
winter,  and  the  Lager,  or  store  beer,  in  the  summer.  The  winter  beer  is  brewed  during 
October  to  April,  when  the  highest  range  of  the  thermometer  is  12°  to  13°.  A  part  of 
the  beer  by  a  short  storing  is  set  aside  for  winter  consumption,  while  the  remainder  is 
used  during  the  summer  months. 

i  volume  of  malt  gives  on  an  average  2-5  to  2*6  volumes  of  winter  beer. 
i  „  ,,  ,,  2'oto2'i  summer  beer. 


2.  Preparation  of  the  Wort. — Under  this  head  is  included  the  preparation  from 


SECT,  vi.]  BEER  BREWING.  745 

malt  of  the  wort — a  saccharine  fluid  containing  dextrine — and  the  flavouring  with 
hops.     The  general  method  of  preparation  is  in  three  operations — 

a.  The  bruising  of  the  malt. 

b.  The  mashing. 

c.  The  boiling  and  flavouring  of  the  wort  with  hops. 

a.  The  Bruising  of  the  Malt. — Beer- wort,  or  the  wort,  as  it  is  generally  termed,  is 
obtained  by  means  of  the  extraction  of  the  bruised  malt  with  water.     To  the  end  that 
all  the  active  principles  may  be  extracted  from  the  malt,  it  must  be  bruised  or  ground 
to  a  fine  meal.    The  obtaining  of  a  clear  liquor,  after  the  extraction,  is  effected  by  means 
of  nitration.     The  grinding  is  ordinarily  performed  in  a  malt  mill,  a  machine  with 
rollers  being  preferred,  as  affording  a  more  equable  product. 

b.  Mashing. — The  mashing  is  a  most  important  operation,  on  success  in  which 
depend  many  of  the  good  qualities  of  the  beer.     It  is  during  this  operation  that  not 
only  are  the  sugar  and  dextrine  already  existing  in  the  malt  set  free,  but  the  uncon- 
verted starch,  by  the  aid  of  diastase,  water,  and  a  favourable  temperature,  suffers 
conversion  into  sugar  and  dextrine.    Lermer  found,  in  the  best  cases  of  mashing,  that 
only  half  the  starch  was  converted  into  a  corresponding  quantity  of  sugar.     The  opera- 
tion is  very  variously  performed,  but  generally  may  be  considered  as  effected  by  either 
of  two  methods  : — 

(1)  The  Decoction  Method. — After  the  infusion  has  been  made  the  mash  is  brought 

to  the  boiling-point,  and 

(a)  A  portion  of  the  water  evaporated  to  form  a  thick  mass  (thick  mash 

boiling).      At   a   subsequent   stage,   only  a  portion   of  the  mash 

having  been  thus  treated,  the  remainder  of  the  mash   is  added ; 

and 
(/3)  The  whole  of  the  mash  is  heated  to  the  boiling-point  (clear  mash 

boiling).     The  hops  are  added  during  the  clear  mash  boiling. 

(2)  The  Infusion  Method,  according  to  which  the  mash  is  prepared  at  a  certain 

degree  of  heat,  but  never  attains  the  boiling-point.  The  crushed  malt  is 
thrown  into  hot  water  (first  cast)  in  the  mash  tun,  and  when  the  mash  has 
reached  a  certain  saccharine  condition,  a  further  addition  of  water  is  made 
(second  and  third  cast).  The  infusion  method  is  much  employed  in  North 
Germany,  Prance,  England,  Austria,  and  Bavaria. 

The  mashing  vessels  are  either  round  tubs  or  wooden  cisterns  with  a  double 
bottom,  the  upper  being  perforated,  and  about  an  inch  above  the  true  bottom.  Between 
the  bottoms  is  a  tap  through  which  the  wort  is  drawn  off.  In  large  breweries  these 
bottoms  are  of  metal  instead  of  wood.  The  hot  water  is  supplied  from  the  bottom 
and  not  from  the  top  of  the  vessel.  Under  the  mashing  vessel  is  situated  a  large 
reservoir,  either  of  stone,  cement,  wood,  or  masonry,  and  destined  to  receive  the 
fluid  run  off  from  the  mash.  The  continuous  stirring  of  the  contents  of  the  mash- 
tun  or  tub  is  effected  either  by  hand  or  machinery  driven  by  water  or  steam 
power. 

(i)  Decoction  Method. — The  general  description  of  the  mashing  process  having  been 
given,  we  now  pass  on  to  the  particular  method  of  preparing  the  wort  by  decoction. 
The  infusion  takes  place  in  the  mash-tun,  in  which  the  required  quantity  of  water  is 
placed,  and  the  malt  to  be  mashed  shaken  in.  The  quantity  of  water  employed  in 
making  the  infusion  is  generally  in  the  proportion  of  202  volumes  of  water  to  100 
volumes  of  malt,  both  at  the  ordinary  temperature.  After  the  bruised  malt  has  been 
well  stirred  in  the  water,  the  whole  is  allowed  to  stand  for  six  to  eight  hours.  During 
this  tune  the  necessary  quantity  of  water  is  heated  to  the  boiling-point  in  the  copper. 
The  quantity  of  water  used  to  prepare  an  estimated  quantity  of  beer  is  termed  the 


746  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

"  cast,"  and  the  quantity  of  malt  the  "  yield."      In   Bavaria  the  quantity  of   beer 
prepared  from  a  denned  quantity  of  malt  is  as  follows  : — 

(2O2'3  volumes  of  Schenk  beer. 
100  volumes  of  malt  yield  |  ^^         >?       ^   Lager  beer> 

In  order  to  produce  this  quantity  of  beer  an  equivalent  quantity  of  water  must  of 
course  be  employed,  so  that,  in  a  Bavarian  brewery,  to  100  volumes  of  malt  there  are 
taken  of  water — 

Schenk  Beer.  Lager  Beer. 

For  infusion        .        .        .• :     202-3  vols.  ...  202*3  vols. 

For  mashing        .        .        .         170*0     ,,  ...  130*0    „ 

372-3     „  .«  3323     „ 

These  proportions  vary  according  to  the  quality  of  the  grain,  the  state  of  the  weather, 
the  length  of  time  of  keeping,  &c. 

The  various  modifications  of  the  decoction  method  are — (a)  The  Bavarian  or  Munich 
method  ;  (/3)  The  Augsburg-Nuremberg,,  or  Swabian  method,  sometimes  termed  "  sedi- 
ment brewing  "  (Satz  brauen). 

(a)  Thick  Mash  Soiling. — According  to  the  Munich  method  (thick  mash  boiling)  the 
cast  of  water  is  divided  into  three  portions,  two  of  which  are  poured  into  the  mash-tun 
to  form  a  paste  with  the  bruised  malt.  After  this  mash  has  stood  for  two  to  four 
hours,  the  remaining  third  of  the  water,  which  during  this  time  has  been  heated  to  the 
boiling-point  in  the  copper,  is  added,  the  whole  of  the  mash  attaining  thereby  a  tem- 
perature of  30°  to  40°.  Then  follows  the  first  thick  mash  boiling  •  for  this  purpose  the 
brewer  draws  the  mashed  grain  to  one  side  of  the  tun,  and  removes  a  portion  to  the 
copper,  where  for  schenk  beer  it  is  boiled  for  thirty  minutes,  and  for  summer  beer  for 
seventy-five  minutes.  The  quantity  of  mash  boiled  at  each  operation  is  generally 
about  half  the  cast.  The  boiling  mass  is  returned  to  the  mash-tun.  Then  follows  the 
second  thick  mash  boiling,  which  for  schenk  beer  lasts  seventy-five  minutes,  and  for 
summer  beer  an  hour.  By  means  of  the  first  boiled  mash  the  contents  of  the  mash- 
tun  are  raised  to  a  temperature  of  48°  to  50°,  and  by  the  second  addition  to  60°  to 
62°.  After  the  finishing  of  the  second  mashing  the  clear  mashing  begins  ;  that  is,  the 
thinly  fluid  part  of  the  mash  is  placed  in  the  copper  and  boiled  for  about  fifteen 
minutes,  and  is  then  returned  to  the  mash-tun.  The  temperature  of  the  mash  is  now 
72°  to  75°,  and  is  most  suited  for  the  formation  of  sugar.  The  mash  remains  in  the 
covered  tun  i^  to  2  hours.  During  this  time,  and  as  soon  as  the  clear  mash  has  been 
removed  from  the  copper,  the  latter  is  refilled  with  a  sufficient  quantity  of  water  for  the 
purposes  of  brewing  small  beer.  When  the  sugar  has  been  properly  formed  and  dis- 
solved in  the  wort,  the  latter  is  removed  from  the  mash-tun  to  the  fermenting  vessels. 
The  remaining  mash  is  then  treated  with  hot  water  to  yield  small  beer,  i  bushel  of 
malt  yielding  35  to  50  quarts  of  this  beer.  The  residue  of  the  small  beer  is  again 
treated  with  water,  the  resulting  infusion  being  employed  in  vinegar  making.  The 
residue  from  this  process  is  used  as  fodder  for  cattle. 

The  thick  mash  boiling  is  by  no  means  a  rational  method,  as  the  separation  of  the 
mash  and  the  several  removals  are  unnecessary  labour,  and  do  not  contribute  so  much 
to  the  complete  extraction  of  the  malt  as  is  generally  supposed  ;  the  high  temperature 
renders  a  portion  of  the  diastase  ineffective,  while  much  of  the  starch  remains  uncon- 
verted into  dextrine  and  dextrose. 

All  who  have  tried  to  reduce  the  brewing  process  to  simple  methods  based  upon 
sound  chemical  and  physical  principles  declaim  against  the  process  of  thick  mash 
boiling,  stating — and  with  good  reason,  proved  by  experiments — that  the  advantages 
of  this  method  are  absurdly  overrated ;  and  that,  in  order  to  lessen  the  bad  effects  of 
this  method  as  much  as  possible,  it  should  be  replaced  by  a  method  of  hot  mashing — 
viz.,  at  a  temperature  of  from  60°  to  65°. 


SECT,  vi.]  BEER  BREWING.  747 

(/3)  Augsburg  Method. — Distinct  from  the  foregoing  mash  methods  is  the  so-called 
"  sediment  brewing  "  used  in  many  Swabian  and  Franconian  breweries.  It  essentially 
consists  in  treating  the  bruised  malt  with  cold  and  then  with  hot  water,  to  obtain  a 
saccharine  wort.  The  bruised  malt  is  mixed  with  cold  water  in  the  mash-tun  in  the 
proportion  of  7  Bavarian  bushels  to  30  to  35  eimers  (each  =  68*41  litres)  of  water. 
After  standing  for  four  hours,  two-thirds  of  the  fluid  is  drawn  off.  During  this  time 
a  quantity  of  water  (48  eimers  to  7  bushels  of  bruised  malt)  is  brought  to  the  boiling- 
point  in  the  copper ;  a  portion  of  this  water  is  now  added  to  the  contents  of  the  mash- 
tun,  which  thus  attains  a  temperature  of  50°  to  52°,  while  the  liquor  or  weak  wort 
drawn  off'  from  the  mash-tun  is  poured  along  with  the  rest  of  the  water  in  the  copper. 
The  liquor  that  has  been  drawn  off  contains  albumen,  diastase,  dextrine,  and  dextrose. 
The  mash  is  allowed  to  stand  for  a  quarter  of  an  hour  in  the  tun,  when  the  fluid  is- 
entirely  drawn  off,  transferred  to  the  copper,  and  heated  to  the  boiling-point.  This  i& 
termed  the  "  first  mash."  While  this  is  going  on,  enough  fluid  will  have  drained  from 
the  malt  in  the  mash-tun  to  fill  the  space  between  the  double  bottoms  of  the  tun  ;  this- 
fluid  is  at  once  removed  to  the  cooling  vessels.  The  fluid  heated  in  the  copper  is  now 
returned  to  the  mash-tun,  the  entire  contents  of  which  attain  a  temperature  of  72°  to- 
75°.  This  "second  mash"  is,  after  an  hour's  interval,  followed  by  a  "third  mash." 
The  wort  is  then  run  into  the  cooling  vessels. 

(2)  Infusion  Method. — The  infusion  method  is  distinguished  from  the  decoction 
method  by  a  slight  difference  in  the  procedure,  the  bruised  malt  being  treated  with 
water  at  a  temperature  of  70°  to  75°,  but  without  any  portion  of  the  mash  being 
boiled.  The  method  is  that  usually  employed  in  this  country,  North  America,  France,. 
Belgium,  and  North  Germany. 

The  water  intended  to  be  used  for  the  mashing  process  is,  according  to  the  initial 
temperature  of  the  water  the  brewer  has  at  hand,  heated,  either  wholly  or  in  part,  in 
the  copper,  the  temperature  being  raised  in  winter  to  75°,  in  summer  to  from  50°  to  60°. 
The  necessary  quantity  is  first  poured  into  the  mash-tun,  the  bruised  malt  being  next 
added,  and  the  mixture  made  up  so  as  to  form  a  moderately  thin  paste.  Water  is 
heated  to  the  boiling-point  in  the  copper  in  order  to  proceed  further  with  the  mashing 
process.  As  soon  as  a  sufficient  quantity  of  water  boils  it  is — usually  by  means  of 
properly  constructed  pipes — allowed  to  run  into  the  mash-tun,  wherein  it  is  consider- 
ably cooled  owing  to  the  colder  liquor  present  in  that  vessel ;  the  increase  of  temperature 
of  the  contents  of  the  tun  to  75°  (the  most  suitable  for  saccharification)  is  gradually 
made  in  order  to  prevent  the  formation  of  starch  paste,  whereby  the  formation  of 
diastase  would  be  interfered  with.  Since  the  conversion  of  amylum  (starch)  into  dex- 
trine and  dextrose  proceeds  gradually  only,  it  is  clear  that  the  contents  of  the  mash- 
tun  should  be  kept  at  the  temperature  suitable  for  that  process ;  while,  however,  on 
the  other  hand,  care  has  to  be  taken  to  prevent  the  mash  becoming  sour  by  the  for- 
mation of  lactic  (probably  also  propionic)  acid. 

The  progress  of  the  formation  of  dextrine  and  dextrose  is  best  ascertained  by  the 
help  of  an  aqueous  solution  of  iodine,  or  preferably  of  iodine  dissolved  in  iodide  of 
potassium,  in  the  proportion  of  i-o  gramme  of  iodine  and  ro  of  iodide  of  potassium  to 
100  c.c.  of  water ;  this  solution  will  at  first  give  with  a  sample  of  the  mash  a  dark  blue 
coloration,  next  a  wine  red,  and  finally,  when  only  dextrine  and  dextrose  are  present, 
no  coloration  at  all.  The  addition  of  2  or  3  drops  of  the  clear  wort  to  a  small 
quantity  of  this  iodine  solution  is  sufficient  for  testing.  When  the  mash  has  been 
kept  for  about  one  hour's  time  at  the  temperature  most  suitable  for  the  saccharification, 
the  wort  is  run  either  into  a  large  reservoir,  or  into  a  vessel  kept  expressly  for  this 
purpose,  or,  lastly,  at  once  into  the  copper ;  a  fresh  quantity  of  water  is  then 
poured  into  the  tun,  and  the  contents  of  the  tun  are  allowed  to  remain  for  half  to 
one  hour  at  a  temperature  of  75°.  It  is  of  course  quite  evident  that  the  infusion 


748 


CHEMICAL  TECHNOLOGY. 


[SECT.  vr. 


method  may  be  varied  as  regards  the  quantity  of  water  and  repeated  number  of 
infusions  ;  but  in  order  to  brew  a  beer  of  a  certain  and  fixed  brand  it  is  requisite 
that  the  degree  of  concentration  of  the  wort  be  always  the  same.  For  the  purpose  of 
ascertaining  the  degree  of  concentration,  Balling's  saccharometer  is  generally  employed, 
which  instrument,  when  put  into  sugar  solutions,  indicates  the  percentage  of  sugar 
they  contain.  Balling  has  shown  that  solutions  of  dry  extract  of  malt  have  the 
same  specific  weight  as  cane-sugar  solutions  of  equal  percentage.  For  use  in  a  brewery 
the  saccharometer  need  only  be  graduated  for  solutions  varying  between  20  and  30  per 
cent. 

Extractives  of  the  Wort. — The  quantity  of  extract  which  a  wort  should  contain 
depends,  of  course,  upon  the  quality  of  the  beer  which  the  brewer  desires  to  make,  and 
differs  according  to  the  nature  of  the  beer,  whether  it  shall  be  thick,  heavy  (rich  in  ex- 
tract), or  strong  (of  great  alcoholic  strength).  The  quantity  of  malt  extract  varies  in  dif- 
ferent beers  from  4  to  1 5  per  cent.,  that  of  the  alcohol  from  2  to  8  per  cent,  i  per  cent,  of 
sugar  in  the  wort  yields  after  fermentation  o-5  per  cent,  of  alcohol.  To  produce  a  beer 
containing  5  per  cent,  of  alcohol  and  7  per  cent,  of  malt  extract,  the  wort  should,  before 
fermentation,  mark  the  degree  on  the  saccharometer  corresponding  to  17  per  cent.  A 

beer  of  3-5  per  cent. 

Fig.  517.  of   alcohol    and    5-5 

per  cent,  of  malt  ex- 
tract will  result  from 
a  wort  containing 
12-5  per  cent,  of 
sugar. 

c.  Boiling  the 
Wort. — The  prepared 
but  not  yet  boiled 
wort  contains  dex- 
trose, dextrine,  some 
unconverted  starch, 
protein  substances, 
extractive  matter, 
and  organic  salts. 
The  colour  of  the 
wort  is  a  brown  or 
yellow-brown,  accord- 
ing to  the  variation 
of  colour  of  the  malt 
fxom  which  it  has 
been  obtained.  The 
odour  is  agreeable 
and  the  taste  sweet. 
The  wort  exhibits  an 
acid  reaction  to  test- 
paper,  owing  to  the 
presence  in  that  fluid 
of  small  quantities  of 
free  phosphoric,  lac- 
tic, and  probably  other  acids ;  but  in  case  the  wort  has  by  accident  become  sour,  or  if 
wort  is  made  purposely  from  already  exhausted  grain  which  has  become  sour,  this 
reaction  is  far  stronger,  and  may  be  ascertained  by  the  odour,  owing  to  the  formation 
of  volatile  acids,  among  which  butyric,  and  in  the  latter  case  lactic  and  propionic  acids, 


SECT.    VI.] 


BEER   BREWING. 


749 


are  present  in  large  quantity.  The  boiling  of  the  wort  aims  at  its  concentration,  and 
also  at  the  extraction  of  the  bitter  principle  of  the  hops  ;  further,  also,  for  the  purpose 
of  coagulating  and  precipitating  a  portion  of  the  albuminous  substances  by  the  aid  of 
the  tannic  acid  contained  in  the  hops.  This  latter  reaction  renders  the  wort  clear. 
In  many  breweries  gypsum  is  added  to  the  boiling  wort  to  reduce  the  whole  of  the 
nitrogenous  substances.  The  boiling  is  generally  effected  in  copper  cauldrons  (tech- 
nically, also  simply,  "  the  copper  "),  set  in  masonry  over  a  fire-grate.  The  fire  is  very 
carefully  disposed,  to  prevent  the  burning  of  the  wort,  as  the  pans  are  exposed  to  the 
direct  action  of  the  flame.  The  manner  of  hopping  (as  it  is  termed) — that  is  to  say, 
the  mode  of  adding  the  hops  to  the  wort — varies  in  different  breweries,  and  depends,  as 
regards  quantity,  also  upon  the  quality  (strength)  of  the  hops,  the  larger  or  smaller 
amount  of  extract  contained  or  desired  to  be  retained  in  the  beer,  and  last,  but  not 
least,  the  mode  of  preservation  and  length  of  time  it  is  intended  to  keep  the  beer. 

Figs.  517  and  518  show  the  ground  plan  and  section  of  the  mashing-house  in  the 
Bavarian  State  Brewery  in  Weihenstephan.  The  bruised  malt  is  mixed  with  water  in  the 
beck,  B,  which  is  fitted  with  an  agitator.  A  part  of  the  mixture  is  allowed  to  flow  down, 
through  the  pipe  (7,  into  the  pan,  M.  Here  it  is  boiled  with  agitation ;  the  hot  mass 
flowing  off  is  then  brought 
back  through  the  tube,  n, 
by  means  of  the  centri- 
fugal pump,  P,  into  7>  ; 
it  is  well  mixed,  another 
portion  boiled  in  the  pan, 
M,  so  that,  when  it  has 
been  pumped  back  into  B , 
the  temperature  desired 
for  converting  the  starch 
into  maltose  and  dextrine 
(68°  to  70°)  is  reached. 
When  the  formation  of 
sugar  is  completed  the 
mixture  is  brought  into 
the  clearing  tank,  L,  pro- 
vided with  a  perforated 
false  bottom,  in  which 
the  grain  remains  whilst 
the  wort  flows  through 
the  tubes,  o,  into  a  com- 
mon channel,  and  thence 
to  the  wort-pan,  W,  in 
which  a  steam  pan  is 
laid.  Here  it  is  boiled 
up  with  hops.  The  watery 
vapours  escape  through 
the  pipes  a.  The  wort 
flows  through  a  strainer, 
and  is  pumped  into  the 
cooling-becks,  K. 

Lintner  prefers  the  Bavarian  to  every  other  method  of  decoction,  with  two  thick 
mashes  and  a  clearing  mash. 

A  pan-mashing  adopted  in  the  brewery  at  Niirtingen,  with  steam  washing,  deserves 
more  general  attention.     The  mashing-pan,  M  (Fig.  519),  is  fitted  in  the  ordinary 


75° 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


manner  with  a  thermometer,  safety-valve,  pressure-gauge,  inlets  for  cold  and  hot 
water,  double  globular  bottom,  and  cocks  for  the  admission  of  steam.  The  prepara- 
tory mashing  apparatus,  v,  is  connected  by  the  pipe,  ra,  with  the  chest  for  bruised 
malt.  A  mashing  machine  with  a  double  movement  effects  the  regulation  of  the  tem- 


perature. The  waste  steam  escapes  through  d  to  a  preliminary  water  heater.  The  mash 
and  clearing  beck,  L,  contains  a  combined  machine  for  stirring  up  and  throwing  out  the 
grains,  and  is  connected  with  the  wort-pump,  p.  The  wort-pan,  W,  is  arranged  like 
the  mashing-pan,  and  in  its  jacket  there  is  a  glass  introduced  to  show  the  level  of  the 
wort.  All  the  vessels  are  made  of  sheet-iron,  jacketed,  and  with  double  bottoms.  The 
hop-pan,  H,  is  connected  with  the  circular  pump,  P. 

Adding  the  Hops. — To  make  winter  beer,  which  in  Germany,  as  a  rule,  is  consumed 
in  four  to  six  weeks  after  brewing,  old  hops  (viz.,  one  year  old)  are  added  in  the 
proportion  of  2  to  3  Ibs.  to  a  Bavarian  bushel  of  malt  (2^22  hectolitres).  For 
summer  beer,  to  be  consumed  in  May  and  June,  4  to  5  Ibs.  of  new  hops  are  added 
to  the  bushel  of  dried  malt ;  while  for  the  beer  for  September  and  October  consump- 
tion, 6  to  7  Ibs.  of  new  hops  are  employed  with  each  bushel  of  malt.  Among  the 
constituents  of  hops  which  are  active  in  the  process  of  brewing,  we  may  mention  in  the 
first  place  the  bitter  ingredient  it  contains  (not  correctly  known,  notwithstanding 
recent  research),  and  which  imparts  to  beer  its  bitter  taste  and  narcotic  property ; 
further,  the  tannic  acid,  which  combines,  during  the  boiling  of  the  wort,  with  a  portion 
of  such  of  its  protein  compounds  as  are  not  rendered  insoluble  by  the  boiling  alone,  and 
form  together  a  precipitate,  rendering  the  wort — previously  turbid — quite  clear,  and 
also  regulating  the  first  and  second  (so-called  after-)  fermentation.  The  essential  oil 
and  resin  met  with  in  hops  act  to  a  certain  extent  as  retarding  the  fermentation,  and 
thxis  prevent  the  wort  becoming  converted  into  a  sour  liquid.  The  inorganic 
constituents  of  hops  do  not  appear — at  least  cannot  be  directly  proved — to  be  of 
much  consequence.  As  regards  the  degree  of  concentration  to  be  given  to  the  wort 
by  the  process  of  boiling,  it  should  be  observed  that  the  degree  of  concentration  as 
ascertainable  by  the  saccharometer  should  remain  from  o-5  to  i  saccharometrical 
percentage  under  the  degree  of  concentration  which  the  wort  should  indicate  at  the 
beginning  of  the  fermentation,  because,  while  cooling,  the  wort  gains  in  concen- 
tration just  the  percentage  alluded  to.  The  separation  of  the  coagulated  albumen 
does  not  take  place  until  the  temperature  of  the  wort  has  reached  90°;  and  the  quan- 
tity separated  is  greater  from  wort  prepared  by  the  infusion  method  than  from  that 


SECT.    VI.] 


BEER   BREWING. 


7S1 


prepared  by  the  decoction  method.  As  soon  as,  in  a  sample  of  the  boiling  wort  taken 
from  the  pan  and  poured  into  a  large  test-glass,  the  suspended  flocculent  matter 
settles  rapidly  to  the  bottom  of  the  glass,  the  boiling  can  be  discontinued,  the  wort 
being  then  ready ;  but,  in  the  infusion  method,  the  boiling  is  continued  for  the  purpose 
of  further  concentrating  the  liquor,  and  for  this  purpose  it  may  even  last  for  from  five 
to  eight  hours.  If  the  boiling  only  aims  at  the  coagulation  of  the  albuminous 
compounds,  one  hour  in  winter,  and  three-quarters  of  an  hour  in  summer,  is  quite 
sufficient.  As  regards  the  hops,  it  is  best  to  add  them  in  a  somewhat  cut-up  state, 
and  not  before  the  greater  part  of  the  albuminous  compounds  have  been,  as  far  as 
possible,  precipitated  by  a  good  boiling  of  the  wort.  In  order  to  extract  the  hops, 
the  wort  is  either  passed  through  a  basket  or  through  any  suitably  constructed  per- 
forated vessel  retaining  the  hops,  this  vessel  being  placed  in  communication  with  the 
coolers ;  or  the  hops  are  boiled  along  with  the  wort ;  or,  again,  several  portions  of  the 
wort  are  boiled  successively  along  with  the  same  quantity  of  wort ;  and  lastly,  even  with 
the  weakest  wort  or  after- run. 

Cooling  the  Wort. — The  cooling  of  the  wort  to  the  degree  necessary  for  the  com- 
mencement of  the  fermentation  is  effected  in  large  wooden,  stone,  or  iron  cisterns.  As 
at  a  temperature  of  25°  to  30°  C.  the  wort  has  a  great  tendency  to  set  up  lactic- 
acid  fermentation,  the  cooling  has  to  be  very  rapid  in  order  that  the  temperature 
of  the  liquid  may  be  soon  much  below  25°  to  30°,  and  thus  any  danger  of  souring 
prevented. 

The  cooling  of  the  wort  is  an  operation  which  is  performed  in  well-constructed 
buildings  well  ventilated  in  all  directions  and  protected  from  rain,  in  which  buildings 
the  coolers  are  placed.  Owing  to  improvements  in  the  modes  of  cooling,  it  is  now 
possible  even  to  brew  beer  in  localities  (as,  for  instance,  Montpellier  and  Marseilles, 
Barcelona  and  Naples)  where  formerly,  on  account  of  the  prevailing  high  temperature 
during  the  greater  portion  of  the  year,  brewing  could  not  take  place  at  all ;  while  also, 
for  the  same  reason,  in  various  countries  (America,  United  States,  especially)  excellent 
lager  beer  is  brewed.  The  cooling  vessels  are  generally  only  6  to  8  inches  deep,  of 
wood,  iron,  or  copper,  and  are  placed  in  an  airy  situation  near  or  immediately  under 
the  roof  of  the  brewery.  Metallic  vessels  are  of  course  more  effectual  in  cooling  the 
wort  in  a  short  time  than  wooden  ones  ;  they  are  also  more  cleanly,  and  less  liable  to 
get  out  of  order.  In  some  breweries  where  a  constant  stream  of  cold  water  is  avail- 
able, the  coolers  are  placed  therein ;  but  this  is  of  course  a  matter  entirely  depending 
on  the  locality  of  the  brewery.  Without  doubt  the  surest  means  of  cooling  the  wort 
rapidly  is  by  employing  ice,  either  in  blocks  in  the  wort  or  in  pans  placed  in  the  cooling- 
tuns.  But,  for  economic  reasons,  this  plan  is  not  generally  available.  The  temperature 
to  which  the  wort  is  to  be  cooled  is  that  best  suited  to  fermentation,  the  next  process 
to  which  the  wort  is  subjected.  The  following  are  the  temperatures  at  which  fermen- 
tation most  readily  sets  in,  depending  upon  the  temperature  of  the  locality  and  upon 
the  kind  of  fermentation  : — 


Temperature  of  the 
Locality  where  the  Fer- 
mentation takes  place. 

Temperature  of  the  Wort. 

In  Sedimentary 
Fermentation. 

In  Superficial 
Fermentation. 

6°  to    7° 

12° 

15° 

7     „     8 

II 

14 

8    „     9 

IO 

13 

9     ii    I0 

9 

12 

IO      „     12 

7°  to  8° 

12°  tO  11° 

The  concentration  of  the  boiled  and  hopped  wort  is  expressed  in  degrees  per  cent,  of 
the  saccharometer. 


752 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


Fig.  520. 


The  old  cooling  process  has  the  defect  that  the  wort  is  exposed  for  a  long  time  to 
impure  air,  so  that  the  benefit  of  pure  air  is  rendered  doubtful.  In  order  to  prevent 
the  contamination  of  the  wort  with  schizomycetes  during  cooling,  the  improved  cooler 
(Figs.  520  and  521)  has  been  used  with  success  at  the  Carlsberg  Brewery.  The  boiling 
vat  runs  through  the  pipe,  M,  into  a  large  cistern  of  galvanised  iron  capable  of  holding 

100  hectolitres.  It  has  a  roof- 
shaped  cover,  B,  which  can  be 
raised  and  lowered,  and  closes  the 
cistern  by  means  of  a  water- joint. 
Through  an  opening  in  the  middle 
of  the  cover  there  moves  the  axle 
of  a  screw,  D ;  there  are  at  the 
side  of  the  cover  two  openings 
for  the  escape  of  steam,  E,  F,  in 
which  there  are  short  tubes  filled 
with  cotton.  There  is  also  in  the 
cover  a  tube,  G,  through  which 
sterilised  air  can  be  introduced 
into  the  space  about  the  wort, 
when  the  latter,  after  cooling,  is 
allowed  to  stream  down  into  the 
fermenting  cellar,  thus  prevent- 
ing the  entrance  of  impure  air. 
Into  the  lowest  part  of  the  cis- 
tern underneath  the  screw  there 

opens  a  tube,  H,  with  numerous  small  apertures ;  through  these  sterilised  air  is  intro- 
duced, ascending  through  the  wort  in  bubbles,  and  supplying  it  with  oxygen.  In  the 
middle  of  the  cistern  lies  a  system  of  cylindrical  tubes  through  which  flows  cold  water 
to  cool  the  wort.  In  the  bottom  there  is  an  outflow  for  the  wort,  N,  another,  0, 
for  droppings,  and  a  third,  P,  for  the  deposited  sediment  and  for  the  water  required 
for  rinsing  and  cleansing  the  apparatus. 
Lastly,  there  is  a  thermometer  which 
shows  the  temperature  of  the  wort  in  a 
man-hole,  H.  The  air  which  is  pumped 
into  the  cistern  and  rises  through  the 
wort  has  been  previously  freed  from  all 
organisms  and  germs  by  means  of  a 
cotton  filter,  and  is  consequently  sterile. 
As  soon  as  the  wort  has  risen  above 
the  entrance  places  of  the  air,  its  access 
is  permitted,  and  the  wort  remains  in 
continual  contact  with  the  air  until  it 
is  cooled  down  to  a  suitable  tempera- 
ture, or,  in  summer,  so  far  that  the 
cooling  can  be  completed  by  means  of 
ice.  The  stay  of  the  wort  in  the  appa- 
ratus does  not  require  more  time  than 
its  exposure  in  the  cooling-becks. 
When  all  the  wort  is  run  into  the 
cistern  the  water  is  allowed  to  flow  through  the  cooling-worm,  and  the  screw  is  set  in 
action  until  the  required  temperature  has  been  reached.  The  wort  is  left  to  stand  quietly 
xintil  the  sediment  has  been  deposited,  and  it  can  be  conveyed  into  the  fermenting  cellar. 


SECT.    VI.] 


BEER   BREWING. 


753 


By  means  of  two  apparatus  and  mashings,  each  of  100  hectolitres,  wort  was  cooled 
down  daily  at  Alt-Carlsberg. 

The  point  to  which  the  wort  must  be  cooled  depends  on  the  temperature  of  the 
cellar  and  the  kind  of  fermentation.  The  following  temperatures  have  been  found 
most  satisfactory  in  practice  : — 


Temperature  of  Cellar. 

Temperature  of  Wort. 

Bottom  Fermentation. 

Top  Fermentation. 

6°  to    7° 

8    „     9 

10     „    12 

12° 
IO 

7°  to  8° 

15° 
13 
11°  to  12° 

According  to  J.  Gschwandler's  researches  (1868),  the  under-mentioned  Bavarian 
beer-worts  had  the  following  composition  : — 


Beer-wort. 

Decoction. 

Bock. 

Sedimentary 
Method. 

Infusion. 

Sugar             .         .     .  .  »,.  ..      . 

4-850 

7-100 

4  '3  70 

5-260 

6^240 

8'6oo 

7'6io 

6  "680 

Nitrogenous  substances 

0790 

i  '350 

Other  constituents 

0-410 

0-630 

0-950 

0-700 

Specific  weight   . 

I-05O 

1-073 

1-052 

1-051 

Extract  (direct  estimation) 
,,       (according  to  Balling) 

1  1  '870 
I2'29O 

17-050 
1  7  '680 

1  1  -980 
12-930 

1  1  '940 
12*640 

While  the  wort  remains  in  the  cooler  a  yellow-grey  or  brown  sediment  is  deposited, 
consisting  of  a  compound  of  coagulated  albumen  with  the  tannic  acid  of  the  hops, 
and  some  starch  similarly  combined.  This  sediment,  during  the  first  cooling,  is  formed 
in  quantities  varying  from  3  to  4  per  cent,  of  the  quantity  of  the  cooled  wort ;  the 
sediment,  when  washed  and  dried,  amounts  to  0*5  per  cent,  of  the  quantity  of  malt 
employed. 

3.  The,  Fermentation  of  the  Beer-wort. — The  wort,  when  cool,  is  run  into  the 
fermenting  tanks,  where  fermentation  sets  in  either  spontaneously  or  is  induced  by 
the  addition  of  yeast.  The  first  kind — spontaneous  fermentation — begins  as  soon 
as  the  wort,  having  been  cooled  down  to  the  temperature  most  suitable  for  fermenta- 
tion, is  left  to  itself,  and  this  fermentation  is  induced  by  the  sporules  of  yeast 
(ferment  cells)  always  present  in  all  fermenting  localities,  which,  meeting  with  the 
wort,  find  in  that  liquid  the  proper  conditions  for  their  growth.  This  kind  of 
spontaneous  fermentation  is  applied  usefully  in  the  brewing  of  the  Belgian  beers 
known  as  Faro  and  Lambick,  which  are  rich  in  lactic  acid.  Usually,  however,  yeast 
is  added  to  the  wort,  and  there  is  avoided  the  dangerous  first  stage  of  spontaneous 
fermentation,  for  by  the  addition  of  the  yeast  a  regular  and  rapid  fermentation  is  set 
up,  but  yet  so  regulated  that  the  yeast  only  gradually  converts  the  dextrose  into 
alcohol  and  carbonic  acid. 

The  results  of  the  researches  made  by  Yon  Lermer  and  Liebig  (1870)  are  of  great 
importance  for  a  rational  basis  of  the  brewer's  business.  According  to  these  savants, 
an  addition  of  sugar  to  a  solution  of  dextrine,  to  which  previously  beer-yeast  has  been 
added,  causes  a  large  quantity  of  the  dextrine  to  be  converted  into  alcohol  and  carbonic 
acid,  just  as  if  the  dextrine  were  sugar. 

The  higher  the  temperature  of  the  wort  and  of  the  locality,  the  smaller  the  quantity 
of  yeast  required.  A  yeast  formed  by  a  violent  fermentation  and  at  a  high  temperature 
has  more  active  qualities  than  yeast  formed  at  a  lower  temperature  and  by  a  longer 
fermentation.  The  first  spreads  itself  rapidly  over  the  surface  of  the  fluid,  and  is 
termed  superficial  yeast  (Oberhefe) ;  while  the  second  sinks  to  the  bottom  of  the  vessel, 
and  there  continues  its  action;  this  is  termed  sedimentary  or  bottom  yeast  (Unterhe/e). 


754  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

The  fermentations  resulting  from  these  two  yeasts  are  respectively  termed  super- 
ficial fermentation  (Obergahrung)  and  sedimentary  fermentation  (  Untergahrung).  The 
latter  fermentation  is  induced  in  worts  that  are  intended  to  yield  beers  of  great 
durability,  such  as  the  Bavarian  beers.  The  superficial  fermentation  is  induced  in 
such  beers  as  are  intended  to  be  soon  drunk.  Where  fermentation  is  induced  in  a 
wort  at  a  low  temperature  and  with  deposit  only  (bottom-yeast),  the  so-called  surface 
fermentation — that  is  to  say,  a  vinous  fermentation  whereby  yeast  is  carried  to  the 
surface  of  the  fermenting  fluid — is  employed  chiefly  for  such  kinds  of  worts  as  are 
intended  to  produce  a  beer  which  is  not  required  to  be  kept  for  any  length  of  time, 
but  rapidly  consumed  after  having  been  brewed.  The  wort  is  in  this  instance  generally 
rich  in  sugar  (glucose) ;  and  while  only  a  portion  of  this  sugar  is  converted  into 
alcohol  (sweet  beer  being  formed),  the  formation  of  a  small  quantity  of  alcohol  (the 
wort  being  only  lightly  hopped)  contributes  largely  to  the  preservation  of  this  kind 
of  beer.  Surface  fermentation  is  also  induced  in  such  kinds  of  worts  as  are  either 
very  concentrated  or  contain  substances  which  to  some  extent  retard,  or  might  even 
altogether  impede,  fermentation ;  as,  for  instance,  the  empyreumatic  substances  pre- 
sent in  a  very  highly  roasted  malt  or  a  large  quantity  of  hops,  these  conditions 
obtaining  in  the  brewing  of  porter,  stout,  and,  as  regards  hops,  of  bitter  ale.  Worts 
of  this  description  come  comparatively  very  difficultly  into  fermentation.  Fermenta- 
tion, no  matter  whether  surface  or  sedimentary  (the  yeast  is  in  this  case  slowly 
deposited  as  a  sediment  on  the  bottom  of  the  vessel),  exhibits  the  three  following 
phases — viz.  : 

1.  The   chief   fermentation,   beginning    soon   after   the  addition   of    the    yeast, 
characterised  by  tho  decomposition  of  the  glucose,  by  the  formation  of  new  yeast,  and 
by  an  increase  of  temperature. 

2.  The  after-fermentation,    during  which   decomposition    of    glucose    continues 
slowly,  while  the  formation  of  new  yeast  cells  does  not  ensue  so  energetically  as  in 
the  first  phase,  the  suspended  particles  of  yeast  settling  down,  and  the  beer  becoming 
clear. 

3.  The  quiet  or  imperceptible  fermentation,  taking  place  when  the  after-fermentation 
is  finished,  is  characterised  by  a  further  decomposition  of  glucose,  while  the  formation  of 
yeast  is  not  perceptible  to  any  extent. 

Sedimentary  fermentation. — Sedimentary  fermentation  is  employed  in  the  brewing 
of  the  Bavarian  schenk  and  lager  beers,  taking  place  in  large  fermentation  vats  con- 
taining 1000  to  2000  litres  of  wort.  Recently,  upon  the  suggestion  of  G.  Sedlmayr, 
these  vessels  have  been  constructed  of  glass.  The  addition  of  yeast  may  be  effected  in 
two  different  ways  :  yeast  may  be  either  added  to  the  wort,  or  a  small  portion  of  the 
wort  is  first  separately  brought  into  a  state  of  fermentation,  and  next  added  to  the 
bulk  of  the  liquid.  In  the  first  case — dry  y easting,  as  it  is  termed — the  yeast  is  placed 
in  a  small  tub  and  wort  poured  over  it,  and,  these  substances  having  been  well  mixed, 
the  whole  of  the  contents  of  the  vessel  are  thrown  into  the  fermentation  vats,  and 
there  worked  about  by  the  aid  of  a  stirring  pole.  According  to  the  second  method — 
wet  y easting  or  yeast  carrying — 6  to  8  maas*  of  yeast  are  added  to  100  maas  of 
wort,  and  well  mixed  with  about  3  eimers  of  wort,  the  mixture  being  allowed  to 
stand  for  four  to  five  hours.  After  fermentation  has  set  in,  the  fermenting  liquid  is 
mixed  with  the  wort  in  the  fermentation  tank.  Tho  yeast  intended  to  be  used  for 
this  purpose  should  be  obtained  from  a  former  and  normal  fermentation  ;  it  should 
not  be  too  old,  should  possess  a  pure  odour  (not  be  foul)  and  a  thick  consistency,  and 
be  frothy. 

After  the  wort  has  been  mixed  with  the  yeast  the  following  phenomena  are  ex- 
hibited:— After  ten  to  twelve  hours  the  decomposition  of  the  dextrose  becomes 
*  The  Bavarian  maas  is  equivalent  to  1-25  English  quart. 


SECT,  vi.]  BEER  BREWING.  755 

apparent  by  the  evolution  of  bubbles  of  carbonic  acid  gas,  which  forms  a  wreath  of 
white  froth  at  the  edge  of  the  vessel.  In  another  twelve  hours  larger  quantities  of  a 
more  consistent  froth  are  formed,  causing  the  surface  of  the  liquid  to  exhibit  a  very 
peculiar  appearance,  which  might  be  compared  to  that  of  irregular  masses  of  broken- 
up  rocks ;  at  the  same  time  a  more  vivid  evolution  of  carbonic  acid  takes  place,  and 
becomes  perceptible  by  the  smell.  The  German  term  for  this  phase  of  the  fermenta- 
tion, das  Bier  steht  im  Krdusen,  can  hardly  be  expressed  in  English,  but  the  meaning 
is  the  fermentation  is  in  full  force ;  these  phenomena  continue,  with  a  regularly 
proceeding  fermentation,  in  full  activity  for  from  two  to  four  days,  and  then  gradually 
subside,  there  remaining  on  the  surface  of  the  liquid  a  somewhat  brown-coloured  film 
of  froth,  much  contracted,  and  chiefly  consisting  of  the  resinous  and  oily  constituents 
of  hops. 

The  yeast  formed  is  only  to  a  very  small  extent  present  on  the  surface  of  the 
liquid,  as,  in  the  case  of  sedimentary  fermentation,  the  carbonic  acid  evolved  cannot 
carry  the  isolated  yeast-cells  to  the  surface.  The  temperature  of  the  fermenting 
liquid  increases  at  the  beginning  of  the  fermentation,  so  that  the  liquid  becomes 
several  degrees  warmer  than  the  air  of  the  locality  where  the  fermenting  vats  are 
placed.  By  the  fermentation  the  wort  loses  the  greater  portion  of  its  dextrose,  about 
half  of  which  is  evolved  in  the  shape  of  carbonic  acid,  while  the  remainder  is  con- 
verted into  alcohol ;  further,  a  portion  of  the  albuminous  substances  dissolved  in  the 
wort  is  rendered  insoluble,  and  deposited  in  the  shape  of  yeast.  On  being  tested 
•with  the  saccharometer,  the  liquid — for  reasons  just  explained — exhibits  after  fer- 
mentation a  less  degree  of  strength  than  before.  The  difference  in  percentage 
shown  by  the  saccharometer  before  and  after  fermentation  is  in  direct  proportion 
to  the  quantity  of  dextrose  decomposed,  and  provides  a  means  of  ascertaining  the 
•course  of  the  progress  of  the  fermentation.  If  this  difference  be  made  the  numerator 
of  a  fraction,  the  denominator  of  which  is  the  percentage  indicated  by  the  sac- 
charometer before  fermentation,  the  value  of  the  fraction  will  increase  proportionately 
with  the  completeness  or  efficacy  of  the  fermentation ;  if,  for  instance,  a  wort 
before  fermentation  marks  a  saccharometrical  percentage  of  11*5,  and  afterwards 
gives  5  per  cent.,  the  difference  (6*5  divided  by  11*5)  gives  the  co-efficient 
0-565;  that  is,  of  100  parts  of  malt  extract  56-5  per  cent,  are  decomposed  during 
.fermentation. 

After-fermentation  in  the  Casks. — After  the  chief  fermentation  is  completed,  which 
'for  summer  or  lager  beer  requires  nine  to  ten  days,  and  for  winter  or  schenk  beer 
seven  to  eight  days,  the  young  or  green  beer  is  put  into  barrels,  after  having  become 
quite  clear  by  the  separation  of  the  yeast.  Before  the  beer  is  vatted  the  scum 
present  on  its  surface  is  removed.  The  yeast,  settling  to  the  bottom  of  the  vat  in 
which  the  fermentation  took  place,  consists  of  three  layers,  the  middle  being  the 
best  yeast ;  the  lowest,  decomposed  yeast  and  foreign  matter,  is  mixed  with  the  yeast 
of  the  upper  layer,  and  if  not  otherwise  saleable  is  sometimes  employed  in  the 
•  distilleries  of  malt  spirits.  The  middle  layer  serves  for  further  fermenting  opera- 
tions. In  breweries  where  pure  water  (the  reader  should  bear  in  mind  that  Bavaria 
is  alluded  to)  is  not  to  be  had,  this  yeast  is  occasionally  obtained  fresh  from  other 
breweries.  It  is  usual  to  fill  casks  or  vats  with  winter  beer  at  once  quite  full;  but 
.  as  regards  summer  beer  several  brewings  are  mixed  in  smaller  vats  in  order  to  obtain 
a  uniformly  coloured  mixture.  The  barrels  are  usually  coated  with  pitch  on  the 
inside,  the  aim  being  to  prevent  the  beer  soaking  into  the  wood,  and  thus  giving  rise, 
when  the  cask  is  emptied,  to  the  formation  of  acetic  acid.  For  the  after-fermentation, 
the  beer  is  placed  in  stone  cellars,  which  should  be  kept  at  the  lowest  temperature 
practicable,  so  as  to  cause  the  after-fermentation  to  proceed  as  slowly  as  possible,  and 
thus  admit  of  the  beer  being  kept  until  the  brewing  season  opens. 


756 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


In  all  parts  of  Germany,  but  mostly  so  in  Bavaria,  great  attention  is  paid  to  the 
construction  of  the  cellars :  these  cellars  are  often  excavated  in  rocks,  and  sometimes 
ice-pits  are  placed  in  the  cellars  to  keep  them  very  cool.  The  after-fermentation  of 
the  beer  sets  in  when  it  is  vatted,  the  moment  of  the  beginning  of  this  process  partly 
depending  on  the  condition  of  the  beer  when  vatted  and  partly  upon  the  temperature 
of  the  cellar.  The  after-fermentation,  which  becomes  manifest  by  the  appearance  of  a 
bright  white-coloured  foam  at  the  bung-hole,  may  set  in  immediately  after  the  vatting 
of  the  beer,  or  may  only  become  perceptible  some  eight  days  after.  Should  the  beer 
happen  not  to  exhibit  any  sign  of  incipient  after-fermentation,  green,  young,  or  new 
beer  is  added  for  the  purpose  of  inducing  this  process.  When  the  after-fermentation 
is  finished,  the  bungs  of  the  casks  or  tuns  are  not  tightly  fastened,  and  the  beer  is  left 
in  this  condition  (in  the  cellars,  of  course)  during  the  summer  months.  About  a  fort- 
night before  the  beer  in  the  casks  is  intended  to  be  tapped,  the  bungs  are  tightly 
closed  in  order  to  cause  as  much  carbonic  acid  to  accumulate  in  the  fluid  as  will  occasion 
the  beer  to  foam  on  being  tapped ;  but  if  beer  happens  to  be  vatted  in  very  green 
condition,  the  bung-hole  should  not  remain-  closed  for  so  long  a  period,  because  then  so 
violent  a  fermentation  may  set  in  that,  on  tapping  the  cask,  its  contents  become  too 
much  agitated,  and  thereby  a  very  turbid  beer  (full  of  yeast)  is  served  to  the  customers. 
Sometimes  the  addition  of  liqueur  (a  solution  of  white  sugar)  is  resorted  to  for  the 
purpose  of  setting  up  a  strong  fermentation  in  very  old  beer.  According  to  J. 
Gschwandler  (1868),  beer  obtained  by  the  processes  alluded  to  has  the  following 
composition : — 


Beer. 

Decoction. 

Bock. 

Sedimentary 
Method. 

Infusion. 

Alcohol 

2  -8  10 

3-380 

2-940 

3'ISO 

Sugar   .... 

1-580 

2-320 

1-460 

i  '330 

Dextrine 

4-610 

6-910 

4-770 

4-800 

Nitrogenous  substances 

0-380 

0740 

Other  constituents 

0-380 

0-400 

0-890 

0-550 

Sp.  gr.  of  solution  of  extract 

I  -022 

1-042 

1-028 

1-026 

Extract  (direct  estimation)  . 
„       (according  to  Balling) 

6-570 
6-950 

9-980 
10-380 

6-230 
7'I2O 

6-130 
6-680 

Surface  Fermentation. — Surface  fermentation  is  that  induced  in  the  worts  intended 
for  the  brewing  of  the  bottled  beers  of  North  Germany,  Bohemia,  Alsace,  England, 
and  Belgium.  Beer  obtained  by  this  process  of  fermentation  is  not  so  lasting  as  that 
prepared  by  the  sedimentary  fermentation  process.  This  difference  is  due  to  the  fact 
that  the  surface  fermentation  goes  on  at  a  higher  temperature,  proceeds  more  rapidly,, 
while  the  elimination  of  the  nitrogenous  compounds  is  also  less  complete.  The  reason 
why  this  process  is  preferred  to  the  sedimentary  fermentation  process  is  that  brewing 
by  the  application  of  the  last  process  is  so  greatly  dependent  upon  a  low  temperature 
that  this  mode  of  brewing  cannot  be  continued  throughout  the  whole  year,  while,  as 
regards  the  other  process,  it  may  be  continuously  carried  on,  and  the  stock  of  beer  kept 
ready  for  use  can  thus  be  considerably  decreased.  Surface  fermentation,  however,  i& 
the  only  plan  for  preparing  briskly  foaming  and  strong  beers.  Porter,  stout,  and  ale 
could  be  brewed  as  well  by  the  sedimentary  method — although  in  the  English  climate 
this  process  would  be  more  difficult  to  conduct  successfully — but  the  main  reason  why 
the  surface  fermentation  is  employed  for  English  malt  liquors  is  that  this  method,  by 
the  great  saving  of  time,  is  cheaper.  The  phenomena  of  the  surface  fermentation  are 
similar  to  those  of  the  sedimentary,  with  the  exception  that  the  progress  is  by  far  more 
violent,  the  froth  surging  more  to  the  surface  of  the  wort.  The  yeast  is  employed  in 
the  same  manner.  An  ingenious  contrivance  is  adopted  in  the  London  breweries  for 
the  purpose  of  carrying  off  the  yeast  from  the  beer  after  it  has  undergone  the  process- 
of  fermentation.  The  wort  is  placed  in  large  hogsheads,  or  rounds,  the  tops  of 


SECT.  7i.]  BEER  BREWING.  757 

which  are  fitted  with  wooden  troughs.  Into  these  troughs  the  yeast  runs  as  it 
rises,  and  is  carried  away.  The  beer  now  becomes  clear,  and  is  pumped  into  the 
stone  vats. 

Steam  Brewing. — The  extensive  application  of  steam  to  the  manufacture  of  beet- 
root sugar  and  alcoholic  spirits  has  given  rise  to  many  suggestions  for  the  substitution 
of  heating  by  steam  for  direct  firing  in  brewing.  The  heating  is  effected  by  a  system 
of  tubes  similar  to  that  described  in  the  preparation  of  beet-root  sugar  (see  p.  705). 
In  brewing,  however,  though  much  would  be  gained  by  uniformly  heating  the  worts, 
and  by  reducing  the  chances  of  burning,  there  would  not  ensue  any  great  economising 
of  fuel,  though  much  labour  might  be  saved.  Steam  could  not  be  employed  directly 
without  a  series  of  tubes,  as  the  condensation  would  cause  a  great  dilution  of  the 
mash. 

Constituents  of  Beer. — The  constituents  of  a  normal  beer  prepared  from  malt  and 
hops  (not  from  substitutes)  are: — Alcohol,  carbonic  acid,  undecomposed  dextrose, 
dextrine,  constituents  of  the  hops  (oil  and  bitter  substance,  no  tannic  acid),  protein 
substances,  a  small  quantity  of  fat,  some  glycerine,  and  the  inorganic  matter  of  the 
barley  and  hops.  The  acid  reaction  which  a  normal  beer  exhibits  after  the  carbonic 
acid  has  been  expelled  from  it  by  boiling  is  due  to  succinic  and  lactic  acids,  with 
traces  of  acetic  acid,  and  perhaps  propionic  acid.  The  sum  of  all  the  constituents  of  a 
beer  after  the  abstraction  of  the  water  is  termed  the  total  contents ;  the  sum  of  the 
non-volatile  constituents,  the  extractive  contents.  Beer  rich  in  malt  extract  is  termed 
rich,  fat,  or  full-bodied  beer  ;  and  that  which  is  poor  in  extract,  but  contains  much 
alcohol,  the  wort  having  been  rich  in  sugar  which  has  all  been  converted,  is  termed  a 
dry  beer. 

The  proportion  of  alcohol  in  beer  can  be  estimated  by  distillation  and  the  testing 
of  the  distillate  with  an  alcoholometer,  or  by  means  of  an  ebullioscope,  or  with  the  help 
of  a  vaporimeter  (see  Wine-testing,  pp.  724-5-6).  The  following  table  shows  the 
average  weight  per  cent,  of  the  alcoholic  contents  of  several  beers  : — 

Per  cent. 

Wiirtzburg  lager  beer  (1870) 44o-4'3 

„          schenk  beer 3 '3-4 '2 

Stuttgardt  lager  beer  (1865) 4*1 

Culmbach  lager  beer  (1865) 4-$ 

Coburg  lager  beer 4*4 

Munich  lager  beer .        .  4'3~5*l 

,,      schenk  beer 3-8-4 -o 

Bock  (Munich,  1870) .  4 '3-4 *8 

Porter  (Barclay,  Perkins  &  Co.,  London,  1862)         .        .  5'5-7'Q 

Strasburg  beer  (1870) 4*21 

Vienna  beer  (1870)  .                  4'i 

Rice  beer  of  the  "  Rhenish  Brewery  "  in  Mentz       .        .  3*6 

The  quantity  of  carbonic  acid  in  beer  varies  between  o'i  to  0*2  per  cent.  Accord- 
ing to  C.  Prandtl  (1868),  dextrose  is  found  in  beer  in  quantities  varying  from  o'2  to 
i '9  per  cent.  The  quantity  of  dextrine,  according  to  Gschwandler's  analyses,  varies 
from  4' 6  to  4*8  per  cent.  The  proportion  of  sugar  to  dextrine  is  never  constant.  The 
occurrence  of  protein  substances  in  beer  has  not  been  sufficiently  investigated  to  warrant 
an  exact  conclusion.  It  may  be  said  that,  on  an  average,  malt  extract  contains  7  per  cent, 
protein  substances,  from  which  Mulder  deduces  that  i  litre  of  beer  should  contain  5*6 
per  cent,  albuminous  substances.  A.  Yogel  (1859)  found  that  i  Bavarian  maas 
(=»  i~o6g  litre)  of  beer  on  an  average  contained  i  to  1*2  gramme  nitrogen ;  and  Feich- 
tinger  (1864)  obtained  from  i  Bavarian  maas  of  several  Munich  beers  between  0*467 
and  1-248  gramme  nitrogen.  Succinic  acid,  acetic  acid,  and  lactic  acid  occur  in  Belgian 
and  Saxony  beers  in  large  quantities.  Tannic  acid  occurs  in  Bavarian  beers  only  in 
small  quantity.  The  inorganic  constituents  of  beer  have  received  great  attention. 


CHEMICAL  TECHNOLOGY. 


[SECT. 


Martius  obtained  from  1000  parts  of  Bavarian  lager  beer  2-8  to  3-16  parts  ash,  con- 
taining one-third  potash,  one-third  phosphoric  acid,  and  one-third  magnesia,  lime,  and 
silica.  J.  Gschwandler  and  C.  Prandtl  (1868)  found  an  average  extractive  contents  in. 
100  parts  of — 


Schenk  beer  (Munich)      .        .        .        • 
Lager  beer  (Munich)        .        .        .        . 
Schenk  beer  (Wiirtzburg) 
Lager  beer  (Wiirtzburg)   . 

Bock  (Munich) 

Salvator  (Munich) 

Rhenish  rice  beer 

Porter  (Barclay,  Perkins  &  Co.,  London) 
Scotch  (Edinburgh)          . 


Parts. 

S'5-6-0 

6-r 

4-6 

4 '4 

S'6-9'8 
9-0-9-4 

7'3 

5-6-6-9 
lO'O-II'O 


Burton  ale 14-0-19-29 

100  parts  of  extractive  matter  contain^  according  to  A.  Vogel  (1865),  3-2  to  3-5  parts 
of  ash ;  100  parts  of  ash  contain  28  to  30  parts  phosphoric  acid,  i  litre  of  beer  contains 
0-57  to  0-93  gramme  of  phosphoric  acid. 

Lermer  (1866)  subjected  several  Munich  beers  to  analysis,  with  the  following 
results : — 


T  * 

2- 

Specific  gravity    . 

i  -02467 

1-0141 

1-01288 

I  -O2 

i  -02678 

i  -03327 

1-017 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Extractive  matter 

773 

4  "93 

4'37 

4'55 

8-50 

9^3 

5  '92 

Alcohol 

5-08 

3'88 

3'SI 

4-41 

5  '23 

4  '49 

3-00 

Inorganic  constituents 

0-28 

0-23 

0-15 

o-iS 

Nitrogen  — 

In  100  parts  extract 

11-15 

871 

12-19 

8-85 

— 

6-99 

In  loo  parts  beer 

0-87 

0-43 

0'53 

0-39 

— 

0-67 

The  analysis  of  the  ash  of  five  of  these  beers  gave- 


2. 

•3 

J' 

4- 

s« 

Potash    . 

29'3I 

33-25 

24-88 

34-68 

29-32 

Soda 

1-97 

0-45 

20-23 

4-19 

O'll 

Sodium  chloride 

4-61 

6'oo 

6-56 

5-06 

6-00 

Lime 

2-34 

2-98 

2-58 

3-14 

6'2I 

Magnesia 

11-87 

8-43 

0-34 

777 

775 

Iron  oxide 

I'OI 

O'll 

0-47 

0-52 

0-84 

Phosphoric  acid 

34-i8 

32-05 

26-57 

29-85 

29-28 

Sulphuric  acid 

1-29 

271 

6-05 

5-16 

4-84 

Silicic  acid     . 

12-43 

14-12 

770 

2-86 

S-oi 

Sand 

0-83 

0-67 

2-30 

5-20 

6-27 

Carbon   .....        ; 

O'4Q 

0-81 

0-40 

0-65 

0-28 

v    +f~y 

100-33 

101-47 

98-03 

99-08 

98-91 

The  high  importance  of  beer,  both  as  regards  its  value  as  a  nutriment  and  the- 
enormous  trade  done  in  this  article,  has  given  rise  to  attempts  to  find  proper  and 
suitable  means  for  testing  that  liquid  in  respect  of  its  quality  and  purity. 

Beer-testing .—The  experiments  proposed  for  ascertaining  the  strength  as  well  as 
freedom  from  adulteration  of  beer  are  termed  beer-testing;  it  is  desirable  that  these 
operations  should  be  easily  executed  and  yield  sufficiently  trustworthy  results.  The 
strength  of  the  beer  is  judged  according  to  the  quantity  of  alcohol,  extract,  and 

*  i.  Bock  beer.  2.  Summer  beer.  3.  White  beer.  4.  White  Bock  beer  (superficially  fer- 
mented, obtained  by  surface  fermentation  from  malted  wheat).  5.  Another  sample  of  Bock  beer.. 
6.  Salvator  beer.  7.  Winter  beer. 


SECT,  vi.]  BEER   BREWING.  759 

carbonic  acid  it  contains ;  it  is  evident,  however,  that  the  real  constituents  of  the 
extract — viz.,  the  therein  contained  quantities  of  dextrine,  hop  constituents,  the 
bye-products  of  alcoholic  fermentation,  such  as,  for  instance,  succinic  acid  and 
glycerine,  not  to  mention  such  substances  as  glucose  and  glycerine  purposely  added 
to  the  wort  as  substitutes  for  malt — largely  influence  the  quality  of  any  kind  of  beer, 
and  therefore  ought  to  be  determined  when  any  rigorously  exact  analysis  of  that 
liquid  is  wanted. 

Beer-testing  is  effected  partly  by  ascertaining  certain  physical  qualities  of  the  beer, 
partly  by  chemical  means.  To  the  former  belong  its  flavour,  odour,  colour,*  con- 
sistency, transparency,  specific  gravity,  refractive  power  to  light,  &c.  By  chemical 
analysis  we  ascertain  and  determine  the  immediate  constituents — viz.,  carbonic  acid, 
alcohol,  extractives,  and  water.  The  carbonic  acid  contained  in  the  beer  is  first 
eliminated  either  by  repeatedly  pouring  a  quantity  of  beer  from  one  tumbler  or  beaker- 
glass  into  another,  care  being  taken  to  let  the  beer  fall  from  some  height,  or  is 
removed  by  shaking  the  liquid  up  in  a  bottle  and  pouring  it  out  of  the  same  and  into 
it  again.  The  gas  having  been  driven  off,  the  specific  gravity  of  the  beer  is  taken 
by  means  of  the  hydrometer  or  saccharometer ;  the  beer  is  next  boiled  down  to  half 
its  original  bulk ;  next  there  is  added  to  it  as  much  water  (best  distilled)  as  is  required 
to  restore  the  liquid  to  its  original  bulk,  and  of  this  liquid  the  specific  gravity  is  again 
determined ;  this  will  be  found  greater  than  that  previously  obtained.  The  difference 
between  the  two  determinations  gives  the  amount  of  alcohol  contained  in  the  beer. 

Sailing's  Saccharometrical  Beer-test. — Since,  by  fermentation,  100  parts  of  malt  ex- 
tract yield  50  parts  alcohol,  twice  the  quantity  of  alcohol  found  will  indicate  the 
quantity  of  malt  extract  necessary  for  its  formation.  This  quantity  of  malt  extract 
added  to  that  still  existing  in  the  beer  indicates  the  whole  of  the  malt  extract  existing 
in  the  wort  before  fermentation. 

The  specific  gravity  of  the  beer-wort  becomes  lower  by  fermentation,  partly  because 
the  specifically  lighter  alcohol  is  formed,  partly  by  the  loss  of  some  of  the  extractive 
matter,  and  partly  also  by  the  loss  of  the  substances  taken  up  in  the  yeast.  This 
decrease  of  the  specific  gravity,  or  attenuation,  as  it  is  termed,  can  be  estimated  either 
directly  by  weighing,  or  by  means  of  the  saccharometer.  The  degree  marked  by  the 
saccharometer  in  a  beer  freed  from  carbonic  acid  we  will  call  m  ;  the  malt  extract  of 
the  wort,  p.  Subtracting  m  from  p,  the  difference  (p-m)  gives  the  apparent 
attenuation,  which  is  the  greater  the  more  thorough  the  fermentation.  The  quantity 
of  alcohol  in  a  beer  varies  in  direct  proportion  with  the  apparent  attenuation.  The 
empirical  alcohol  factor,  a,  by  which  the  apparent  attenuation  must  be  multiplied  to 
obtain  the  alcoholic  contents  of  the  beer  =  A  in  weight  per  cent,  [(p—  m)a  —  A],  be- 
comes the  greater  the  higher  the  original  degree  of  concentration  of  the  wort.  For 
worts  between  6  to  30  per  cent,  of  extractive  matter,  this  factor  varies  from  0-4879  to 
0-4588.  The  alcohol  factor  can  be  found  by  the  following  equation,  when  the  apparent 
attenuation  (p-m)  and  the  alcoholic  contents  of  the  wort  (A)  are  known;  then 

With  the  help  of  the  alcohol  factor,  a,  the  alcoholic  contents  in  weight 

per  cent,  can  be  calculated.  A  quantity  of  beer  being  boiled  to  volatilise  the  alcohol, 
and  the  residue  having  been  diluted  with  water  to  the  original  bulk  or  weight,  if  a 
weighed  quantity  were  operated  with,  the  specific  gravity  gives  the  quantity  of 
extractive  matter  contained  in  the  beer,  which  Balling  terms  n.  The  difference  be- 
tween the  extractive  matter  contained  in  the  wort  (p)  and  that  of  the  beer  (n),  or 

*  Very  recently,  C.  Leyser  has  invented  a  colorimeter  with  which,  by  means  of  a  normal 
solution  of  iodine  (12-7  grammes  iodine  to  a  litre)  after  having  brought  the  beers  to  an  equal  colora- 
tion with  water,  he  estimates  the  relative  degree  of  the  original  colour.  The  invention  is  -fully 
described  in  the  Jahresberichte  der  Chem.  Technologic  for  1869,  p.  467. 


_/   A   \ 

\p-mj' 


760  CHEMICAL  TECHNOLOGY.  |_SECT-  VI- 

(p  —  ri),  gives  the  actual  attenuation,  which,  multiplied  by  the  alcohol  factor  for  the 
actual  attenuation  (b),  likewise  gives  the  quantity  of  alcohol  contained  in  the  beer 
expressed  in  percentage  by  weight.  The  alcohol  factor  for  the  actaal  attenuation 

/   A   \ 
is  6  =  (    _     ).     Subtracting  from  the  apparent  attenuation  (p  -  m)  the  actual  (p-ri), 

the  difference  (d)  in  the  attenuations  is  obtained — d  =  (p-m)  -  (p -n) ;  or  d  =  m  —  n. 
d  is  known  when  the  extractive  matter  contained  in  the  beer  (?i)  and  the  saccharo- 
inetrical  percentage  (m)  of  the  beer  free  from  carbonic  acid  are  known;  d  is  the 
greater  the  more  alcohol  the  beer  contains.  The  alcohol  factor  multiplied  by  the 
difference  in  attenuation  gives  the  percentage  (A)  of  alcohol,  from  which  the  alcohol 
factor  for  the  difference  in  attenuation  can  be  obtained  by  the  following  equation: — 
A 

c  = .     It  averages  2  -24.     Finally,  with  the  help  of  c,  the  difference  in  attenuation 

(p-m) 

of  the  alcoholic  contents  of  a  beer  can  b.e  calculated  approximative^,  even  when  the 
quantity  of  extractive  matter  of  malt  contained  in  the  wort  is  not  known.  The  apparent 
divided  by  the  actual  attenuation  gives  a  quotient  (d),  which  is  the  ratio  of  the 

p  —  m, 
attenuations,  d  =  — - — ,  and  can   be  calculated  with  the  help  of  the  alcohol  factor  for 

the  apparent  attenuation  (a)  and  of  the  original  extractive  contents  of  the  wort  (p\. 
First — (a)  is  obtained  by  the  division  of  the  alcohol  factor  for  the  actual  attenuation 
by  the  corresponding  attenuation  quotient  or  ratio.  Assuming  the  alcohol  factor  for 
the  difference  in  attenuation  to  be  —  2-24,  and  next  doubling  the  approximative  alcoholic 
contents  thus  obtained,  we  arrive  at  the  quantity  of  the  extractive  matter  of  the  wort 
from  which  the  alcohol  was  formed.  Adding  to  this  the  extract  yet  met  with  in  the 
beer,  the  sum  thus  found  expresses  the  approximate  percentage  of  the  extractive  con- 
tents of  the  wort.  When  (p)  has  thus  been  approximately  obtained,  Balling's  tables 
give  the  corresponding  attenuation  quotient  q,  reckoning  all  decimals  above  0*5  as 
units,  and  neglecting  those  under  0-5.  If  only  the  original  concentration  of  the 
wort  (p)  is  to  be  calculated,  the  percentage  of  the  alcohol  of  the  beer  may  be 
obtained  from  the  equation  to  the  actual  attenuation  A  =  (p  —  n)b.  If  the  degree 
after  fermentation  is  975  or  (16-29  —  6-54),  the  saccharometrical  percentage  (see 

9'75 

PP-  748,  759)  = =0-542. 

16-29 

THE  MANUFACTURE  OF  SPIRITS. 

The  industrial  production  of  alcohol  has  in  most  countries  a  different  basis  and 
signification,  different  raw  materials,  different  purposes,  and  different  fiscal  regulations 
and  circumstances,  all  of  which  have  a  great  influence  on  the  conditions  of  manufacture. 
If  an  alcoholic  fluid  is  submitted  to  distillation,  alcohol  and  water  pass  over,  whilst 
the  non-volatile  constituents  of  the  liquid  remain  behind  in  a  more  concentrated 
form. 

Properties  of  Alcohol. — The  formula  of  alcohol  (as  a  chemically  pure  substance)  is 

C1  IT  i 
C,H6O,or     *  jj}0-     I*  is  a  colourless,  thin,  very  mobile  fluid  of  0-792  sp.  gr.,  boiling 

a*  78'3°,  while  water  boils  under  the  same  atmospheric  pressure  at  100° ;  thus  there  is 
afforded  a  means  of  ascertaining,  by  the  boiling-point  of  an  alcoholic  fluid,  the  quantity 
of  alcohol  contained.  Between  o°  and  78-3°  (its  boiling-point)  alcohol  expands  0-0936 
of  its  volume,  while  the  co-efficient  of  expansion  of  water  between  the  same  degrees  is 
0-0278.  The  expansion  of  alcohol  is  thus  3^  times  greater  than  that  of  water;  and 
this  fact  is  made  available  in  alcoholimetry.  The  tension  of  the  vapour  of  alcohol 


SECT,  vi.]  THE   MANUFACTURE   OF  SPIRITS.  761 

at  78-3°  is  equal  to  an  atmosphere,  while  water  must  be  raised  to  a  temperature  of  100° 
to  obtain  the  same  pressure.  Thus,  the  variation  in  height  of  a  column  of  mercury 
subjected  to  the  pressure  of  these  vapours  may  be  made  a  measure  of  the  quantity  of 
alcohol  contained  in  a  fluid.  On  this  principle  the  vaporimeter  (see  p.  724)  is  con- 
structed. Alcohol  is  readily  inflammable,  and  burns  with  a  pale  blue  flame  without 
giving  off  soot.  Its  heat  of  combustion  corresponds  to  7183  units  of  heat.  It  eagerly 
absorbs  water,  and  upon  this  property  is  based  its  use  for  the  preservation  of  articles 
of  food,  cherries  and  other  fruit,  and  also  anatomical  preparations.  It  mixes  with 
water  in  all  proportions,  whereby  a  decrease  of  bulk  of  the  mixture  and  increase  of 
specific  gravity  is  observed — 

5 3 '9  volumes  of  alcohol,  with 

49*8         „  water,  form  a  mixture,  not  of 


103*7,  but  of  100  volumes. 

Alcohol  is  a  solvent  for  resins  (upon  which  property  is  based  its  application  to  the 
manufacture  of  varnishes,  cements,  and  pharmaceutical  preparations),  and  also  a 
solvent  of  many  essential  oils.  These  solutions  are  employed  either  as  perfumes,  such 
tis  eau  de  Cologne,  or  as  liqueurs,  cordials,  and  aqua  vitse,  or  as  spirits  for  burning  in 
lamps,  as,  for  instance,  the  mixture  of  oil  of  turpentine  and  alcohol,  so-called  fluid  gas ; 
jilcohol  also  dissolves  carbonic  acid  gas,  a  property  made  available  in  the  making  of 
effervescing  wines. 

By  the  influence  of  certain  oxidising  agents,  alcohol  is  converted  first  into  aldehyde 
and  next  into  acetic  acid,  as  illustrated  in  the  so-called  quick  vinegar  making  process. 
Alcohol  does  not  dissolve  common  salt,  and  upon  this  property  Fuchs's  test  is  based. 

By  the  action  of  most  of  the  stronger  acids,  aided  by  heat,  alcohol  is  converted  into 
what  are  termed  ethers ;  as  regards  the  action  of  sulphuric  acid  upon  alcohol,  it 
depends  upon  the  relative  quantities  and  degree  of  concentration  of  these  liquids 
whether  sulphovinic  acid,  ether,  or  bicarburetted  hydrogen  gas  be  formed.  Hydro- 
chloric acid  forms,  with  alcohol,  ethyl  chloride  or  hydrochloric  ether.  Butyric  and 
oxalic  acids  form  ethers  directly  when  heated  along  with  alcohol ;  but  most  of  the 
other  organic  acids  require  the  aid  of  sulphuric  or  hydrochloric  acid  for  this  purpose. 
Alcohol  is  the  intoxicating  principle  of  all  spirituous  liquors. 

Eaw  Materials. — Alcohol  is  always  the  product  of  vinous  fermentation.  The 
manufacture  of  spirits  therefore  includes  three  principal  operations  : — 

1.  The  preparation  of  a  saccharine  fluid. 

2.  The  fermentation  of  this  fluid. 

«  3.  Separation  of  the  alcohol  by  distillation. 

All  saccharine  fluids,  therefore,  or  those  substances  which  yield  alcohol  by  fermen- 
tation, can  be  employed  in  the  manufacture  of  spirit ;  and  all  materials  so  employed 
contain  already  either  completely  formed  alcohol,  or  cane  sugar  and  dextrose,  or,  finally, 
substances  which  by  the  influence  of  diastase  or  dilute  acids  are  converted  into  dextrose. 
Such  substances  are  starch,  inuline,  lichenine,  pectin  compounds,  and  cellulose.  The 
raw  materials  of  spirit  manufacture  may  be  generally  classed  in  the  three  following 
groups : — 

ist  Group. — Fluids  in  which  the  alcohol  is  already  present,  requiring  only  distilla- 
tion to  effect  its  separation.  Such  fluids  are  wine,  beer,  and  cider. 

2nd  Group.— Substances,  either  solid  or  liquid,  which  contain  sugar,  which  may  be 
either  cane  sugar,  or  dextrose  and  levulose,  or  sugar  of  milk.  In  this  group  are 
included  the  sugar-cane,  beet-root,  carrot,  maize  stalk,  the  Chinese  sugar-cane  (sorghum), 
some  kinds  of  fruit — viz.,  apples,  cherries,  figs — some  berries  (grapes,  mountain  ash 
berries,  &c.),  the  melon  and  gourd,  some  fruits  of  the  cactus  tribe,  the  molasses  of  cane 


762  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

and  of   beet-root   sugar   manufacture,  the  marc  of  grapes  and  refuse  grain  of  beer 
making,  honey,  and  milk. 

yd  Group. — All  substances  which  originally  contain  neither  alcohol  nor  sugar,  but 
the  constituents  of  which  may  be  converted  into  sugar  and  dextrose.  Such  are  starch, 
inuline,  lichenine,  pectin  compounds,  and  cellulose,  chiefly  found  in — 

(a)  Roots  and  bulbs :  Potatoes,  dahlia  roots,  &c. 

(b)  Cereals :  Rye,  wheat,  barley,  oats,  maize,  and  rice. 

(c)  Leguminous  and  other  seeds :  Buck- wheat,  millet,  black  or  negro  millet,  peas, 

lentils,  beans,  vetch,  chestnut,  horse-chestnut,  oak  leaves,  &c. 

(d)  Substances  containing  cellulose :  Sawdust,  paper,  straw,  hay,  leaves,  osiers, 

moss. 

In  the  future  a — 

ajtk  Group  may  be  added,  which  will  embrace  all  substances  which  probably 
may  enter  into  the  synthetic  preparation  of  alcohol,  and  thus  form  what  might  be 
called  a  mineral  spirit.  Berthelot  in  1855  proved  that  alcohol  can  be  formed  from 
olefiant  gas  and  water  (C2H4  +  H20  =  C2H60).  Olefiant  gas,  when  agitated  for  a 
length  of  time  with  concentrated  sulphuric  acid,  gives  rise  to  the  formation  of  sulpho- 
vinic  acid:  and  from  this  liquid,  after  having  been  diluted  with  water,  a  dilute 
alcohol  can  be  distilled.  This  experiment  has  as  yet  only  a  scientific  interest ;  the 
process  has  been  tried  on  the  large  scale  in  France,  but  failed  to  be  commercially 
available. 

For  the  conversion  of  the  starch  of  potatoes,  &c.,  into  maltose,  diastase  is  employed. 
The  production  of  malt  for  the  distiller  differs  little  from  that  of  a  malt  for  brewing. 
For  the  purpose  of  distilling,  it  is  necessary  to  produce  a  malt  which  is  able  to  split  up 
a  maximum  of  starch  into  maltose  and  dextrine.  It  is,  therefore,  the  object  of  the 
distillery  maltster  to  produce  a  maximum  of  diastase  in  the  sprouting  barley  and  to 
bring  it  into  a  state  of  efficacy. 

Saccharification. — As  has  been  explained  above,  when  starch  is  split  up  by  the 
action  of  diastase  at  temperatures  below  75°,  there  are  formed  diastase  and  dextrine  ; 
this  process  is  saccharification.  By  the  action  of  dilute  sulphuric  acid  upon  starch  at 
higher  temperatures  there  is  formed,  along  with  dextrine,  chiefly  dextrose,  and  also- 
small  quantities  of  maltose.  By  the  prolonged  action  of  sulphuric  acid  much — though 
not  all — of  the  dextrine  changes  into  dextrose.  The  dextrine  which  is  formed  from 
starch  by  the  action  of  diastase  may  be  regarded  as  non-fermentable  in  the  short  time- 
allowed  for  the  alcoholic  fermentation  in  distilleries,  and  yet  during  the  fermentation 
it  is  converted  into  a  fermentable  sugar — as  appears  from  the  experiments  of 
Delbruck  and  Marcker — by  the  subsequent  action  of  the  residual  diastase.  When, 
therefore,  the  fermentable  maltose  has  been  used  up  by  the  yeast,  the  residual  diastase 
converts  the  dextrine  into  maltose.  For  the  exhaustion  of  the  fermentable  material 
it  is  therefore  necessary  to  retain  diastase  in  the  mash  for  alcoholic  fermentation. 
The  secondary  action  of  the  diastase  is  disturbed  by  too  high  a  temperature  and  by 
lactic  acid  in  the  fermenting  mash. 

Mashing  Process. — The  mashing  process  was  formerly  carried  on  in  distilleries  in 
the  same  manner  as  in  breweries.  The  new  methods  are  based  upon  the  use  of  steam 
under  pressure,  and  have  been  developed  in  different  directions  by  Hollefreund,  Bohm, 
and  Henze. 

All  these  new  mashing  processes  aim  at  a  simplification  of  the  operations,  a  better 
utilisation  of  the  raw  materials,  perfection  and  certainty  in  execution,  or  (like  the 
apparatus  of  Henze)  simplification  in  the  saccharification.  The  apparatus  of  Holle- 
freund consists  of  a  horizontal  vessel  resembling  a  steam  boiler,  and  for  a  fermenting 
space  of  4000  litres  it  must  have  a  capacity  of  6000  litres.  The  potatoes — 3000  kilos. 
for  the  above  capacity — are  introduced  through  a  man-hole,  and  heated  by  direct  steam 


SECT.    VI.] 


THE    MANUFACTURE   OF   SPIRITS. 


Fig.  522. 


after  the  apparatus  has  been  closed,  until  the  temperature  reaches  137°  to  143°,  which 
answers  to  a  pressure  of  2  to  2\  atmospheres.  An  agitator,  consisting  of  knives  placed 
spirally  around  a  shaft,  is  set  in  action  to  comminute  the  potatoes.  The  steam  is  then 
blown  oft'  by  opening  a  valve,  and  the  temperature  is  let  sink  to  about  160°,  a  degree, 
however,  which  would  still  destroy  the  diastase  in  the  malt  which  is  now  added.  An 
artificial  refrigeration  is  therefore  needed.  As  soon  as  the  pressure  in  the  mashing  - 
pan  has  fallen  to  i  atmosphere  the  valve  is  closed,  and  an  air-pump  connected  with 
the  apparatus  is  set  in  action  which  causes  the  contents  to  boil  and  water  to  evaporate. 
By  a  powerful  air-pump  it  is  possible  in  fifteen  minutes  to  reduce  the  temperature 
from  1 06  to  65°.  The  rarefaction  of  the  air  serves  to  suck  the  bruised  malt  into 
the  apparatus  and  effect  saccharification  in  a  very  short  time. 

Bohm's  apparatus  consists  of  a  pan  in  which  the  potatoes  are  steamed.  The 
apparatus  works  without  an  air-pump,  and  effects  refrigeration  by  a  combined  agitat- 
ing and  cooling  arrangement.  The  agitator  consists  of  flat  cylindrical  vessels  of  sheet- 
iron,  fitted  011  their  surfaces  with  knife-like  projections,  in  order  to  comminute  the 
potatoes.  The  sheet-iron  cylinders  are  fixed  011  a  hollow  axle  in  such  a  manner  that 
the  cooling  wnter  passes  through  the  cylinders  and  escapes  through  a  double  tube  in 
the  hollow  axle.  The  apparatxis  is  cooled  from  without  by  sprinkling  with  cold 
water. 

Both  apparatus  require  a  great  mechanical  power,  and  have  been  almost  completely 
superseded  by  that  of  Hen/e,  a  cylinder  of  strong  boiler-plating,  provided  with  a 
manometer  and  a  safety-valve.  It  is  filled  with 
potatoes  through  a  man-hole  in  the  cover ; 
steam  is  introduced  through  pipes,  one  of 
which  opens  underneath  the  cover,  and  the 
others  in  the  lower  conical  part,  until  all  the 
air  has  been  expelled  through  the  open  safety- 
valve,  which  is  then  closed,  and  a  pressure  of 
2  to  3  atmos.  is  given.  After  the  steaming 
process,  the  lower  valve  is  opened,  so  that  the 
potatoes  are  forced  out  in  a  state  of  fine 
division.  They  then  arrive  in  a  preliminary 
mashing-tub,  cooled  by  means  of  water ;  they 
meet  here  with  the  needful  supply  of  malt,  and 
are  easily  liquefied.  Greatly  to  be  recommended 
is  the  method  of  admitting  steam  introduced  at 
Biesdorf,  which  sets  the  mass  in  rotatory  move- 
ment. In  order  that  the  steam  may  move 
spirally  upwards,  the  inlet-pipe,  c  (Fig.  522),  is 
turned  upwards. 

According  to  the  experiments  of  Maercker 
and  Delbriick  on  the  action  of  the  modern 
steaming  apparatus,  the  starch  of  the  fresh 
potato  floats  in  a  watery  liquid,  as  shown  in 
the  section  (Fig.  523)  of  a  potato  magnified 
400  times.  The  intercellular  substance,  con- 
sisting of  matters  resembling  pectine,  which  connects  the  several  cells,  is  insoluble  in 
cold  water,  but  is  readily  converted  into  soluble  substances  in  boiling  water  under  pres- 
sure. Fig.  524  shows  the  cells  of  a  potato  steamed  at  3  atmospheres  ;  the  starch 
granules  are  completely  swelled,  and  the  intercellular  matter  is  perfectly  dissolved  ;  the 
cells  still  hang  together,  but  they  are  easily  separated  if  they  have  not  all  burst. 

The  further  continuation  of  this  part  of  the  subject  would  be  superfluous  where,  as 


764 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


in  Britain,  the  distiller  does  not  operate  upon  roots,  but  upon  either  grain  or  saccharine 
matter. 


Fig  523- 


Figr.  524. 


Preparation  of  a  Vinous  Mash. —  Vinous  Mash  from  Cereals. — Grain  brandy  (corn 
brandy)  may  be  prepared  from  either  wheat,  rye,  or  barley.  Generally  more  than  one 
kind  of  grain  is  xised,  because  experience  has  proved  that  a  larger  quantity  of  alcohol  is 
obtained  when  two  kinds  of  grain — for  instance,  wheat  and  barley,  rye  and  barley — are 
mixed.  A  mixture  of  rye  with  wheat  or  barley  malt,  or  wheat  with  barley  malt,  is  very 
generally  used,  at  least  abroad.  To  i  part  of  malt  from  2  to  3  parts  of  non-malted  gram 
are  usually  taken.  Either,  as  is  done  in  England,  wort  is  made,  the  gram  being  first 
malted,  next  mashed,  and  the  wort  drawn  off,  or  the  mixture  of  malt  or  unmalted  gram  is 
allowed  to  ferment  together.  The  latter  method  is  more  usual  in  Germany,  and  will  be 
that  described  here.  In  Russia  and  Sweden  brandy  is  prepared  without  malting  ;  by 
properly  mashing  rye-meal  a  reaction  ensues  between  its  constituents,  the  effect  of 
which  is  the  same  as  if  it  had  been  acted  upon  by  diastase  of  malt 

The  preparation  of  a  mash  from  grain  may  be  considered  as  consisting  of  the  follow- 
ing  four  operations  : — 

(1)  The    Bruising. — The  materials,  malted  as   well  as  unmalted  grain,  are   first 
bruised.     As  it  is  not  essential  in  the  manufacture  of  spirits  that  a  clear  wort  should 
be  prepared,  the  grain  may  be  broken  up  very  small,  whereby  the  formation  of  sugar 
is  rendered  more  complete.  Green  malt  is  now  generally  considered  preferable  by  many 
distillers. 

(2)  The  Mixing  with  Water. — Making  of  Mash. — This  operation  is  almost  identical 
with  that  of  the  mashing  of  the  brewer  ;  the  only  distinction  being  that  the  distiller 
aims  at  the  entire  conversion  of  the  starch  into  glucose,  while  the  brewer  does  not  re- 
quire this,  as  he  also  wants  some  dextrine.     The  complete  saccharification,  and  next 
the  complete  conversion  of  the  glucose  into  alcohol   during  fermentation,  are  possible 
only  with  a  certain  degree  of  dilution  of  the  mash.     The  quantity  of  water  to  be 
mixed  with  the  grain  must  not  be  reduced  too  much,  because  that  would  involve  a  loss 
of  spirits. 

(3)  The  Cooling  of  the  Mash. — When  the  saccharification  is  complete,  the  mash 
should  be  rapidly  brought  to  the  temperature  suitable  for  fermentation   by  being 
placed  in  cooling  vessels,  just  as  is  done  with  the  wort  in  brewing,  by  being  placed  in 
an  apparatus  termed  a  refrigerator,  or  by  the  application  of  ice  or  cold  water.     The 
temperature  to  which  the  mash  has  to  be  cooled  varies  according  to  the  locality  and 
the  duration  of  the  fermentation,  but  it  averages  23°  C.     When  sufficiently  cooled  the 
liquid  is  placed  in  the  fermenting  vats. 

(4)  The  Fermentation  of  the  Mash. — The  fermentation  vat  is  generally  made  of  wood, 


SECT.    VI.] 


THE  MANUFACTURE  OF  SPIRITS. 


765 


though  sometimes  stone  is  used.  The  first  possesses  the  property  of  retaining  the  heat 
for  a  longer  time,  and,  for  the  same  reason,  large  vessels  are  preferred.  The  capacity 
seldom  exceeds  4000  litres.  Either  beer  yeast  in  its  fluid  condition  or  dry  yeast  is  used 
to  set  up  fermentation.  The  latter  is  mixed  with  warm  water  before  being  added  to  the 
contents  of  the  fermentation  tanks.  Of  the  fluid  beer  yeast  there  are  usually  taken 
to  1000  litres  of  mash  8  to  10  litres  ;  while  for  3000  litres  of  mash  15  to  20  litres  of 
yeast  are  a  sufficient  quantity.  Of  the  dry  yeast,  f  kilo,  is  employed  to  1000  litres 
of  mash,  or  i  kilo,  of  yeast  to  3000  litres  of  mash.  In  large  distilleries  artificial 
yeast  is  sometimes  employed,  as  beer  yeast  of  the  requisite  quality  cannot  always  be 
procured  at  a  remunerative  price.  The  mode  of  adding  the  yeast  is  the  same  as  that 
employed  in  breweries.  After  standing  for  from  three  to  five  hours  the  temperature  of 
the  mash  will  have  increased  to  from  30°  to  32°.  Carbonic  acid  is  then  given  off,  and 
the  heavier  substances  settle  to  the  bottom  of  the  tank.  This  continues  for  about 
four  days,  when  the  clear  fluid  may  be  considered  ready  for  further  operations. 

The   yield   of   alcohol   is   better   if   the  temperature  is   reduced   to  2 7°- 28°.     It 
is  therefore  prudent  to    sus- 
pend  in     the   cooling-beck    a  Fi£-  525- 
copper  refrigerating  worm  tra- 
versed by  cold  water,  as  shown 

in  Fig-  525- 

An  apparatus  for  cooling 
introduced  by  Eckert  is  shown 
in  Fig.  526.  The  agitators, 
formed  as  U  -tubes,  can  be 

easily  taken  to  pieces.  In  the  front  sides  of  the  vat,  A,  is  fixed  the  shaft  a, 
upon  which  are  arranged  within  the  vat  a  number  of  hollow  rings,  b.  At  the  ends 

Fig.  526. 


of  the  shaft  a  there  is  fixed  a  rather  longer  ring,  c,  provided  with  a  screw  thread. 
Upon  this  thread  two  female  screws,  cv  are  cut,  so  as  to  hold  the  rings,  6,  fast 
together.  Each  of  the  rings,  b,  has  two  radial  perforations,  in  which  threads  are 
cut,  and  in  which  a  number  of  U -tubes,  d,  are  screwed,  and  connected  by  concentric 
rings  in  such  a  manner  that  the  ends  of  each  tube,  d,  open  into  two  rings,  6,  lying  side 
by  side.  Thus  all  the  rings  and  tubes  form  with  the  shaft  a  system  which  can  be  set 
in  motion.  This  system  of  pipes  effects  an  energetic  mixture  of  the  mass  in  the  vat 
by  means  of  its  curvature.  In  order  to  effect  an  afflux  and  reflux  of  the  water  for 
cooling,  a  pipe,  g  or  h,  is  pushed  upon  the  shaft  a,  over  the  rings,  c.  This  pipe  is 
closed  by  the  stuffing-boxes,  e.  Both  tubes,  g  and  h,  are  fitted  with  short  pieces, 
I  or  m,  of  which  the  former  effects  the  influx  of  the  cooling  water  and  the  latter  its 
outflow. 


766  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

Spirits  from  /Sugar  Waste. — In  India  the  scum  from  the  boiled  sugar,  the  molasses, 
<fec.,  are  brought  to  fermentation  and  the  fermented  fluid  distilled.  The  product  is  in 
the  English  colonies  known  as  Sum,  in  Madagascar  and  Mauritius  as  Guildine.  The 
peculiar  aroma  of  rum  is  contained  in  the  portion  which  first  distils  over.  By  the 
fermentation  and  distillation  of  the  scum  from  the  boiling  of  the  sugar-cane  juice,  a 
coarse,  sour,  dark  brown  or  black-coloured,  acrid-tasting  brandy  is  obtained ;  it  is 
known  as  Negro  rum.  In  England  and  Germany  rum  is  frequently  made  from  the 
diluted  molasses  of  the  sugar  refineries  fermented  with  yeast,  the  fermented  fluid  being 
distilled  after  about  three  or  four  days'  fermentation.  The  aroma  peculiar  to  rum  is 
obtained  by  the  addition  of  some  pelargonic  ether  or  essence  of  pine-apple.  Beet-root 
molasses  is  also  largely  used  for  the  purpose  of  obtaining  spirits.  By  itself  the  beet- 
root sugar  molasses  is  difficult  to  ferment,  but  if  the  alkalinity  of  this  material  is 
first  neutralised  by  the  addition  of  some  sulphuric  acid,  and  the  material  next  boiled 
with  a  further  addition  of  acid  for  the  purpose  of  converting  into  inverted  sugar  the 
cane  sugar  it  yet  may  happen  to  contain,  the  fermentation  may  be  readily  set  up  and 
regularly  proceed.  100  kilos,  of  molasses  yield  on  an  average  40  litres  of  spirit.  The 
very  objectionable  odour  of  this  spirit  is  due  to  fusel  oil,  which  contains  small  quanti- 
ties of  propylic,  butylic,  and  amylic  alcohol,  pelargonic  acid,  and  caprylic  acid,  while 
later  researches  have  added  to  this  list  cenanthic,  caproic,  and  valerianic  acids.  The 
residue  left  in  the  retort  is  used  for  the  preparation  of  potassa  (see  page  291).  The 
addition  of  sulphuric  acid  has  not  only  the  effect  of  converting  the  cane  sugar  into 
an  easily  fermentable  sugar,  but  also  prevents  the  setting  up  of  lactic-acid  fer- 
mentation. 

Spirits  from  Wine  and  Lees. — The  distillation  of  spirits  from  wine  is  chiefly  carried 
on  in  France,  Spain,  and  Portugal.  The  yearly  production  of  spirits  from  wine  or 
French  brandy  (alcool  de  vin)  in  France  alone  amounts  to  450,000  hectolitres  of  85 
per  cent,  and  400,000  hectolitres  of  60  per  cent.  The  quality  of  the  spirit  is  indirectly 
affected  by  the  degree  of  ripeness  of  the  grapes,  and  directly  by  the  care  bestowed 
upon  the  fermentation  and  distillation,  by  the  more  or  less  intimate  mixture  of  the 
volatile  principles  of  the  wine  with  the  alcohol,  and  by  the  age  of  the  wine.  Old  wine 
yields  a  spirit  of  better  quality  than  new  wine.  The  freshly  distilled  brandy  is  colour- 
less, and  remains  so  even  when  bottled ;  but  since  the  spirit  is  kept  in  oaken  casks  it 
extracts  therefrom  some  colouring  and  extractive  matter.  The  best  kinds  of  brandy 
are  distilled  in  the  Departement  de  Charente,  and  the  brand  known  in  commerce  as 
Cognac  (name  of  a  town)  is  the  most  valued.  From  the  marc  and  wine-lees  spirit  is 
also  distilled.  By  the  distillation  of  spirits  from  wine  a  residue  is  left  in  the  retort 
(the  vinasse)  which  contains  a  large  quantity  of  glycerine,  which  may  thus  be  obtained 
as  a  bye-product. 

Since  the  invasion  of  the  phylloxera  the  amount  of  spirit  distilled  from  Avine  has 
sunk  to  about  15,000  hectolitres  (1885). 

Fermentation. — The  addition  of  yeast  to  the  cooled  mash  in  the  fermenting  vat 
takes  place  in  the  same  manner  as  with  malt.  To  100  kilos,  of  mash  are  added  i  to 
2  litres  of  beer-yeast,  or  f  to  i  kilo,  of  dry  yeast.  The  potato  mash  contains,  besides 
the  husks  of  malt  and  grain,  some  finely  divided  cellular  tissue  ;  these  substances  during 
fermentation  are  carried  to  the  surface  of  the  mash  and  form  a  scum,  the  appearance 
and  behaviour  of  which  give  an  opportunity  of  judging  the  progress  of  the  fermenta- 
tion. The  fermentation  is  said  to  be  regular  or  irregular ;  the  former  begins  some 
four  to  six  hours  after  the  yeast  has  been  added,  and  proceeds  in  a  regular  manner, 
the  end  depending  upon  the  quantity  of  yeast  added  and  upon  the  temperature.  The 
progress  is  quiet,  not  violent,  the  scum  which  appears  on  the  surface  sinking  or  being 
drawn  to  one  side  of  the  vat  and  thrown  up  at  the  opposite  side,  while  bubbles  of  air 
or  gas  appear  and  burst  on  the  surface,  much  as  bakers'  dough  heaves  under  the 


SECT,  vi.]  THE   MANUFACTURE   OF   SPIRITS.  767 

influence  of  the  ferment.  Irregular  fermentation  is  so  far  opposed  to  the  former  that 
the  surface  of  the  mash  is  only  partly  covered  with  froth,  which  remains  in  one 
position,  and  does  not  move  of  itself.  The  result  of  such  a  fermentation  is  generally 
defective,  the  reason  being  the  incomplete  saccharification  of  the  mash,  the  addition  of 
too  small  a  quantity  of  yeast,  or,  finally,  working  at  too  low  a  temperature.  After 
about  sixty  to  seventy  hours  with  a  regular  fermentation,  the  mash  is  ready  for  distil- 
lation. Recently,  large  quantities  of  spirits  have  been  prepared  from  maize  and  also 
from  rice. 

Distillation. — The  fermented  mash  (as  obtained  from  potatoes)  is  a  mixture  of  non- 
volatile and  volatile  substances.  To  the  first  belongs  the  fibre,  malt  husks,  inorganic 
salts,  protein  substances,  undecomposed  and  decomposed  yeast,  succinic  acid,  lactic 
acid,  glycerine,  <fec. ;  to  the  volatile,  the  alcohol,  fusel  oil,  water,  and  small  quantities 
•of  acetic  acid.  The  volatile  constituents  of  the  mash,  the  products  of  the  fermenta- 
tion, are  separated  from  the  non- volatile  by  distillation,  during  which  the  volatile 
•constituents  are  converted  into  vapour,  afterwards  cooled  and  condensed  in  another 
vessel.  When  a  vinous  mash  is  heated  to  the  boiling-point,  vapours  are  generated 
which  consist  essentially  of  alcohol  and  water  ;  by  condensing  these  vapours  there  is 
•obtained  a  mixture  of  alcohol  and  water. 

Water  boils  at+  100°,  barometer  760  mm. 
Alcohol  „     „  +  78-3°,         „  „ 

Thus  it  might  be  thought  that,  while  the  boiling-point  of  water  is  21-7°  higher 
than  that  of  alcohol,  it  would  follow  that,  when  a  vinous  mash  is  heated  to  80°,  only 
the  alcohol  would  be  converted  into  vapour,  the  water  remaining  behind.  But  this  is 
not  the  case,  for  under  all  circumstances  the  boiling-point  of  a  mixture  of  alcohol  and 
water  is  higher  than  that  of  pure  alcohol  alone,  and  the  vapour  formed  consists  of  both 
alcohol  and  water.  The  reason  is  partly  due  to  the  affinity  of  alcohol  for  water,  partly 
also  to  the  fact  that  water  evaporates  at  a  lower  temperature  than  its  boiling-point ; 
the  former  (affinity)  retains  alcohol  and  prevents  its  escape  at  proper  boiling-point 
(78'3°)  in  the  shape  of  vapour.  If  the  mixture  of  alcohol  and  water  be  heated  to  its 
boiling-point  (suppose  90°),  much  more  alcohol  will  be  converted  into  vapour,  because 
its  boiling-point  is  lower,  while  of  water  only  just  so  much  is  evaporated  as  would  be 
the  case  were  it  when  pure  to  be  heated  to  this  temperature,  while  simultaneously  a 
current  of  air  is  passed  through  it,  because  the  vapours  of  alcohol  evolved  from  the 
mixture  act  exactly  in  the  same  manner  as  would  a  current  of  air  carried  through  the 
mixture  of  alcohol  and  water,  the  former  substance  taking  up  just  as  much  water  as 
will  be  volatilised  at  the  boiling-point  of  the  mixed  liquids.  As  the  quantity  of  vapour 
evolved  from  a  liquid  bears  a  direct  relation  to  the  temperature  of  that  liquid,  the 
quantity  of  aqueous  vapours  in  the  mixture  of  vapours  will  increase  according  to  the 
increase  of  temperature,  until  at  last,  as  soon  as  the  boiling-point  rises  to  that  of  water 
(100°),  no  more  alcohol  will  be  present  in  the  vapours  which  are  given  off.  At  the 
commencement  of  the  distillation  the  vapour  given  off  contains  much  alcohol  and  very 
little  water ;  presently  more  water  comes  over,  and  finally  only  water.  It  is  therefore 
quite  evident  that  we  cannot  by  distillation  separate  alcohol  at  once  from  the  rest  of 
the  volatile  constituents  of  a  vinous  mash  liquor.  By  interrupting  the  distillation  at 
the  proper  time,  there  is  obtained  in  the  distillate  all  the  alcohol  contained  in  the 
mash,  along  with  a  certain  quantity  of  water,  while  the  residue  of  the  distillation  will 
not  contain  any  trace  even  of  alcohol.  The  liquor  obtained  by  the  first  distillation  is 
generally  very  weak  alcohol,  and  requires  further  rectification,  as  it  is  termed,  to 
increase  tho  proportion  of  alcohol.  This  rectification  (another  process  of  distillation) 
may  be  continued  till  the  alcohol  contains  only  a  small  quantity  of  water,  which  can 
only  be  eliminated  by  the  aid  of  such  substances  as  have  a  greater  affinity  for  water 
than  the  alcohol,  which  retains  that  liquid  very  tenaciously.  Anhydrous,  or  absolute 


768  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

alcohol,  can  only  be  obtained  by  treating  highly  rectified  alcohol  with  some  substances 
which  have  a  great  affinity  for  water,  such  as  caustic  lime,  fused  calcium  chloride, 
<fec. ;  but  really  absolute  alcohol  is  never  used  on  the  large  scale  in  industry.  The  first 
portions  of  liquid  obtained  by  the  distillation  of  vinous  mash  are  rich  in  alcohol,  and  are 
termed  fore-run  or  first-run,  while  the  last  portions  of  the  fluid  yet  containing  alcohol 
are  termed  after-run.  A  doubly  rectified  alcohol  contains  50  per  cent,  pure  spirit ;  but 
by  means  of  rectification  alone  a  stronger  alcohol  than  of  95  per  cent,  cannot  be 
obtained.  The  residue  of  the  distillation  is  called  fluid-wash. 

Apparatus  for  Distillation. — A  distilling  apparatus  as  usually  employed  consists  in 
its  simplest  form  of  four  parts — namely,  the  still  or  retort,  the  head  or  cap  of  the 
still,  the  cooling  apparatus,  and  the  receiver. 

The  still  or  retort  is  generally  constructed  of  sheet-copper — more  rarely,  of  iron 
boiler-plates.  The  shape  of  the  vessel  varies,  but  is  generally  a  somewhat  flattened 
cylinder,  provided  with  a  round  opening  of  12  to  14  inches  diameter,  fitted  with  a 
collar  about  i  inch  in  height  forming  the  neck,  on  which  the  cap  or  head  is  placed. 
The  bottom  of  the  still  is  either  somewhat  bulged  inwards  at  the  centre  or  is  quite 
flat.  The  residue  of  the  distillation  is  removed  through  a  waste-pipe  fitted  with  a 
stop-cock  attached  to  the  bottom  of  the  vessel.  From  the  cap  or  head  a  pipe  conveys 
the  volatilised  alcohol  to  the  receiver,  while  jutting  obliquely  from  the  top  of  the  still 
is  a  pipe  for  the  introduction  of  the  mash.  The  head  carries  the  vapours  from  the 
still  into  the  cooling  or  condensing  apparatus ;  although  a  simple  tube  might  answer 
this  purpose,  it  is  preferred  to  make  the  head  of  the  stills  large  and  wide,  not  only  for 
the  purpose  of  separating  any  particles  of  mash  which  might  happen  to  be  carried  oft" 
with  the  vapours  of  the  boiling  liquid,  but  also  to  obtain  a  distillate  richer  in  alcohol, 
because  an  increased  surface  is  favourable  to  the  cooling  of  the  vapours,  whereby 
the  aqueous  vapour  is  first  condensed ;  moreover,  large  heads  are  advantageous,  lest 
by  a  rapid  evolution  of  vapours  the  mash  might  boil  up  (priming) ;  roomy  space  in 
the  head  then  prevents  the  liquid  passing  over  into  the  worm.  Since  the  volume  of 
the  vapours  decreases  during  the  condensation,  a  somewhat  conically  shaped  head  would 
be  the  best  form  for  this  portion  of  the  apparatus.  The  cooling  apparatus  is  not 
simply  destined  to  convert  the  vapours  carried  into  it  from  the  head  into  liquid,  but  it 
is  also  required  that  this  liquid  be  so  far  cooled  down  as  to  prevent — at  least  as  much 
as  possible — the  evaporation  of  the  distillate ;  the  condensing  apparatus  should  not 
be  too  roomy ;  that  is  to  say,  there  should  not  be  too  much  space  for  the  vapours, 
because  this  would  cause  air  to  enter  the  cooling  apparatus,  and  this  air,  while  mixing 
with  the  vapours  of  alcohol,  carries  off  along  with  it  some  of  this  fluid,  thereby  causing 
a  loss  of  the  fluid.  It  is  also  requisite  that  the  cooling  apparatus  be  strongly  made, 
yet  at  the  same  time  so  constructed  as  to  admit  of  being  readily  taken  down  for 
cleansing  purposes  and  easily  fitted  up  again  ;  usually  the  cooling  apparatus — techni- 
cally termed  worm — consists  of  a  series  of  spirally  bent  tubes  made  either  of  block 
tin  or  copper,  seldom  of  lead ;  this  apparatus  is  placed  in  a  large  wooden  or  metal  vat 
containing  cold  water,  or  as  in  the  more  recently  constructed  distilling  apparatus,  cold 
vinous  mash,  which  is  thus  made  warm  previous  to  being  transferred  into  the  still, 
whereby,  of  course,  a  saving  of  fuel  is  effected. 

The  principal  improved  apparatus  which  we  shall  describe  are  those  of  Pistorius, 
Gall,  Schwarz,  Siemens,  and  Cellier-Blumenthal. 

Pistorius's  Apparatus. — Pistorius  first  introduced  in  Germany  a  distilling  apparatus 
fitted  with  two  stills  ingeniously  connected  with  rectificators  and  dephlegmators. 
When  a  distilling  apparatus  is  required  which  not  only  extracts  all  the  alcohol  from 
the  mash,  but  also  produces  the  alcohol  in'  a  very  pure  and  concentrated  state,  per- 
forming this  work  with  the  least  possible  expenditure  of  fuel  and  labour,  Pistorius's 
apparatus  answers  the  purpose  admirably.  A  and  B,  Fig.  527,  represent  the  two  stills. 


SECT.  VI.] 


THE   MANUFACTURE   OF  SPIRITS. 


769 


A  is  the  main  still,  which  is  either  placed  on  a  furnace  and  heated  directly  by  fire  or 
by  means  of  steam.  Heating  by  steam-pipes  instead  of  direct  firing  possesses  many 
advantages.  The  second  still,  B,  is  placed  at  a  somewhat  higher  level  than  the  first, 
and  when  not  heated  by  steam-pipes  is  situated  on  the  flue  of  the  furnace  fire  of  the 
first  still.  The  main  still,  A,  is  fitted  with  a  large  helm,  D,  fastened  on  the  still  with 
bolts  and  nuts,  p  is  a  tube  projecting  from  the  helm  and  provided  with  a  safety-valve 
which  opens  inwards,  in  order  to  give  access  to  air  as  soon  as  a  vacuum  ensues  in  the 
interior  of  the  apparatus  towards  the  end  of  the  distillation  in  consequence  of  the  con- 
densation of  the  vapours.  There  is  also  connected  with  this  tube,  p,  a  small  condenser 
q,  as  in  Dorn's  apparatus,  from  which  samples  showing  the  progress  of  the  distillation 
may  be  taken.  In  both  stills  stirring  apparatus,  m  and  n,  are  fitted  to  prevent 
the  mash  from  burning.  By  the  tube  x  the  vapour  of  the  "  low  wine "  is  admitted 
to  the  second  still,  the  mash-still.  From  the  helm,  F,  of  the  mash-still  a  curved  pipe, 
s,  conveys  the  vapour  to  the  mash  fore-warmer,  which,  as  in  Dorn's  apparatus,  is 

Fig.  527. 


divided  into  two  parts,  the  upper,  E,  containing  the  mash,  the  lower,  g  (the  "low  wine" 
cis-tern),  the  vapour  ascending  along  the  narrow  passage,  V,  to  the  rectification 
apparatus,  H.  Frequently  the  vapour  is  conveyed  to  a  third  still  before  entering  #/ 
this  still  is  not  shown  in  the  drawing.  The  rectification  apparatus,  ff,  consists  of  two 
or  three  conically  shaped  vessels,  made  of  sheet-copper  and  connected  together,  and  is 
provided  with  a  cistern  filled  with  water,  W ' ;  it  is  connected  with  the  condenser,  R,  by 
the  tube  C.  The  tube  x  conveys  cold  water  to  the  rectification  apparatus,  and  the 
short  tube,  y,  does  so  to  the  fore-warmer.  The  pump,  P,  is  employed  to  pump  the 
mash  from  the  cistern,  Z,  to  the  fore-warmer;  thence  it  is  carried  to  the  second  still, 
and  thence  again  to  the  first  still.  When  both  stills  and  the  fore-warmer  are  filled 
with  mash,  the  fire  is  lighted  under  the  first  still.  The  steam  or  vapour  from  the 
inash  in  A  passes  to  the  mash  in  B,  which  is  thereby  heated  to  the  boiling-point.  The 
still  B  serves,  therefore,  the  purpose  of  a  rectificator.  When  the  distillation  has  begun, 
the  vessel,  W,  on  the  rectificator  is  filled  with  cold  water,  which  is  re-supplied  when  it 
has  become  warmed  by  the  passing  vapours.  As  soon  as  the  steam  reaches  the  upper 

3  c 


770 


CHEMICAL  TECHNOLOGY. 


[SECT.  TO. 


rectificator,  the  real  distillation  commences.     The  condensed  fluid  drops  into  a  cistern 
in  which  a  hydrometer  is  placed. 

Gall's  Apparatus. — In  most  apparatus  for  distilling  from  a  vinous  mash  the  distil- 
late becomes  gradually  weaker  and  is  not  throughout  of  the  same  strength.  Gall  and 
Marienbad  have  endeavoured  to  avoid  this  defect  in  their  apparatus,  Fig.  528, 
so  as  to  obtain  a  more  uniform  product  during  each  distillation.  Two  stills  are  placed 
in  a  suitable  manner  in  a  steam-boiler  and  the  stills  are  connected  with  the  separator 
(low  wine  cistern).  B  B  are  the  stills ;  C  is  a  boiler  with  flues,  *  i.  The  stills,  in  order 
to  prevent  them  cooling,  are  fixed  into  the  boiler.  D  is  a  third  still  placed  on,  not  in, 
the  boiler ;  E  is  the  low  wine  cistern ;  F  and  G  two  dephlegmators  or  separators ;  A 
is  a  condenser  with  a  worm,  H.  The  mash  is  put  first  into  the  still  D  by  means  of  the 
tube  a  a,  this  still  serving  as  a  fore-warmer  and  rectificator.  From  this  still  both  the 

Fig.  528. 


stills  B  B  are  filled.  From  the  boiler  a  current  of  steam  is  conveyed  through  the  bent 
tube,  b,  into  the  three-way  cock,  c,  whence  the  steam  is  either  passed  into  one  or  both 
the  stills  B  B,  or  is  conveyed  upwards  by  the  tube  b  to  the  vessel  destined  to  steam  the 
potatoes.  The  vapour  from  one  or  both  of  the  stills  B  B  proceeds  to  the  still  Z>,  and 
thence  into  the  low  wine  cistern,  E,  and  passing  through  the  dephlegmators,  F  and  G, 
finally  enters  into  the  condenser.  The  peculiarity  of  Gall's  apparatus  consists  in  that 
by  the  peculiar  arrangement  of  tubes  and  stop-cocks,  each  of  the  two  stills  may  at  will 
be  brought  into  action,  it  being  possible  to  turn  the  s,team  at  pleasure  into  the  right- 
hand  still,  and  next  into  the  left-hand  still,  or  vice  versa.  Each  still  may  be  also  dis- 
connected, the  wash  therefrom  discharged,  and  the  still  re-filled  without  in  the  least 
interrupting  the  working  of  the  other  apparatus  of  the  portions  ;  the  distillation  can 
therefore  proceed  uninterruptedly,  one  part  of  the  apparatus  being  filled  while  the 
other  is  at  work. 


SECT.   VI.] 


THE  MANUFACTURE  OF  SPIRITS. 


771 


Schwarz's  Apparatus. — Schwarz's  apparatus  is  in  very  general  use  in  the  south-west 
of  Germany.  It  consists,  Fig.  529,  of  the  steam  boiler,  D  ;  two  mash-stills,  A  and  B  ; 
the  fore-warmer,  C  ;  the  "  low  wine  "  cistern,  or  receiver,  E  ;  the  rectificators,  H  and 
F  ;  and  the  condenser,  G.  M  is  a,  reservoir  for  cold,  N  one  for  hot  water.  The  steam 
generated  in  the  boiler,  Z>,  passes  through  the  pipe,  g,  into  the  under  compartment,  A, 
of  the  double  still,  and  through  the  mash  contained  there  •  becoming  mixed  with  vapours 
of  alcohol,  it  arrives  in  the  helm  z,  and  further  makes  its  way  by  means  of  the  tube  u 
into  the  upper  part  of  the  double  still;  thence,  after  a  double  rectification,  it  is  conveyed 
by  means  of  the  tube  t  to  the  fore- warmer,  G ;  the  upper  part  of  this  vessel,  pro- 
vided with  the  tubes  a  a  a,  acts  as  a  dephlegmator  or  separator,  the  condensed  fluid 
flowing  into  E.  The  steam  which  arrives  from  the  upper  part  of  the  still  passes 
through  E,  and  thence,  by  way  of  the  tubes  a  a,  into  the  helm  and  the  tube  n,  which 
latter  is  surrounded  with  the  vessel  H,  kept  cold  by  means  of  cold  water  ;  the  dephleg- 
mation  continues  here.  From  H  the  steam  passes  through  V  to  F,  an  apparatus  cor- 

Fig.  529- 


responding  to  the  fore-warmer,  C,  but  of  smaller  dimensions,  because  here  the 
quantity  of  vapour  has  become  greatly  reduced  while  it  has  become  richer  in  alcohol. 
The  dephlegmator  tubes  are  here  surrounded  by  cold  water,  not  by  cold  mash,  the 
former  liquid  being  constantly  renewed  so  as  to  keep  cold.  The  steam  or  vapour 
collected  in  the  helm  b  is  sufliciently  laden  with  alcohol  to  admit  of  being  at  once 
conveyed  to  the  condenser,  G,  the  condensed  distillate  flowing  out  at  i.  The  vinous 
mash  is  first  poured  into  the  fore-warmer,  (7,  wherein  it  is  occasionally  stirred  by  the 
arms,  d  d,  and  crank,  d,  so  as  to  keep  it  uniformly  mixed  and  heated.  When  the  mash 
has  become  warm  it  is  conveyed  into  the  upper  compartment  of  the  double  still  by  the 
pipe  e,  and  into  the  lower  compartment  through  the  open  valve  ;  this  compartment 
also  serves  as  cistern  for  the  phlegma  from  all  other  parts  of  the  apparatus ;  the  fluid 
flows  backwards  from  the  compartments  h  and  I  of  the  rectificators,  H  and  F,  by  way 
of  the  tubes  m'  and  n,  into  the  low  wine  cistern,  E,  thence  into  the  upper  compart- 


772 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


ment  of  the  double  still,  where  it  mixes  with  the  mash.  As  soon  as  the  mash  has  given 
up  all  its  alcohol,  which  can  be  ascertained  by  testing  the  inflammability  of  the  vapour 
issuing  from  the  test  stop-cock,  o,  the  residue  is  removed  by  opening  the  tap,  p.  By 
means  of  the  tubes  q  q  q,  the  rectificators  and  condensing  apparatus  are  supplied  with 
cold  water.  The  warm  water  from  the  condenser  is  conveyed  by  the  tube  r  into  the 
boiler.  By  means  of  fi,  the  steam  can  be  admitted  to  the  potato  vessel,  and  by  S  into 
the  reservoir,  N,  when  it  is  desired  to  heat  the  water  it  contains  to  the  boiling-point. 
Schwarz's  apparatus  possesses  the  advantage  of  being  easily  taken  to  pieces  and 
cleansed.  But,  on  the  contrary,  among  its  disadvantages  are  the  following  : — The  con- 
struction of  the  mash-warmers  is  not  quite  suited  for  the  purpose,  while  also  the 
condensed  liquid  in  E  is  not  brought  sufficiently  into  contact  with  the  hot  steam  to 
effect  a  thorough  distillation  or  rectification.  The  steam  passes  so  quickly  through 
the  liquid  that  it  is  only  very  imperfectly  deprived  of  its  water  (dephlegmated)  when 
it  reaches  the  dephlegmation  apparatus,  where  it  will  consequently  be  but  imperfectly 
rectified,  while  the  vertical  steam-pipes  offer  too  few  points  of  contact,  and  allow 
much  steam  to  pass  off  without  being  fully  condensed ;  while  even  the  partly  con- 
densed vesicular  steam  is  carried  off  along  with  the  steam  escaping  condensation.  The 
condenser  itself  is  imperfect,  being  constructed  of  a  number  of  vertical  pipes,  through 
which  the  condensed  liquid  rapidly  falls  without  becoming  quite  cold,  and  in  order  to 


obtain  a  sufficient  condensation  an 
immense  quantity  of  cold  water  has  to 
be  used. 

/Siemens's  Apparatus. — Among  the 
apparatus  capable  of  producing  a  large 
quantity  of  spirits  at  a  small  cost  is 
that  of  Siemens.  This  apparatus  is 
much  used  in  the  distillation  of  brandy. 
It  consists,  Fig.  530,  of  two  mash-stills 
set  in  a  boiler,  and  capable  of  being 
alternately  used  (by  means  of  the  three 
cocks,  a,  b,  and  c),  in  the  same  manner 
as  in  Gall's  apparatus,  while  the  fore-warmer  and  dephlegmator  is  constructed  accord- 
ing to  Siemens's  plan  L  is  the  boiler;  P  one  of  the  mash-retorts;  K is  the  low  wine 
receiver;  R  the  fore- warmer;  A,  a  reservoir  in  which  the  condensed  water  intended 
as  feed  water  of  the  boiler  is  collected ;  0  is  the  dephlegmator ;  B  a  reservoir  for  the 


SECT.  7i.]  THE  MANUFACTURE   OF  SPIRITS.  773 

vapours  condensed  in  C.  From  the  dephlegmator  the  vapour  passes  to  a  condenser  not 
shown  in  the  engraving.  This  apparatus  is  constructed  of  such  dimensions  that  it  can 
perform  the  work  about  to  be  mentioned.  The  boiler  has  to  steam  about  5000  kilos, 
of  potatoes  in  four  lots,  during  from  forty  to  forty-five  minutes  each,  and  should  thus 
lie  capable  of  yielding  in  three  hours  the  fifth  part  of  the  weight  of  the  potatoes,  =  1000 
kilos.,  or  in  one  hour  333  kilos,  of  steam,  which  renders  necessary  a  steam-generating 
surface  of  about  1 1  square  metres.  But  since  the  distillation  requires  steam  also,  this 
generating  surface  has  to  be  increased  by  about  20  per  cent.,  and  should  consequently 
be  13-5  to  14  square  metres.  The  size  of  the  mash-stills  should  be  sufficiently  large 
to  contain  with  ease  500  litres  when  properly  filled  •  because,  as  already  stated,  the  fluid 
from  A  is  not  returned  to  the  still,  but  to  the  steam-boiler,  the  stills  being  set  into  the 
last-named  vessel  not  becoming  externally  cooled,  whereby  the  quantity  of  water  carried 
along  with  the  vapours  of  spirit  is  compensated  for. 

The  mash-warmer  consists  of  a  cylindrical  portion,  i  i,  the  lower  part  of  which 
has  an  indentation,  c.  In  the  cylinder  is  placed  a  narrower  portion,  o  o,  of  the  real 
mash-containing  vessel  fitted  with  the  heating  tube,/w.  The  upper  part  of  the  fore- 
warmer  is  fitted  to  the  lower  part  by  means  of  the  flange,  h  h.  r  is  a  stirring  apparatus, 
which  is  frequently  set  in  operation  during  the  process  of  distillation.  The  vapours 
from  the  second  still  are  carried  into  the  depression,  c,  under  the  fore-warmer,  which, 
in  order  that  the  vapours  may  come  into  contact  with  the  phlegma,  is  covered  with  a 
sieve.  The  vapours  surround  the  under  part  of  the  mash  reservoir  and  enter  into  the 
tube  /,  through  which  they  pass  to  the  lower  cylinder  of  the  dephlegmator.  The  con- 
densed water  of  the  dephlegmator  is  conducted  into  the  reservoir,  A.  The  upper  and 
under  part  of  the  fore-warmer  are  made  of  cast-iron,  but  the  interior  bottom  and 
heating  surfaces  are  made  of  copper.  This  kind  of  fore-warmer  has  the  advantage  of 
uniformly  distributing  the  heat,  while  it  can  be  easily  cleansed.  The  dephlegmator,  C, 
is  so  contrived  that  the  rectified  vapour  can  be  conveyed  to  the  condenser  by  two  separate 
pipes  placed  in  an  opposite  direction  to  each  other,  and  are  joined  again  in  close 
proximity  to  the  condenser.  The  remainder  of  the  details  will  be  seen  on  studying  the 
drawing. 

Continuous  Distilling  Apparatus. — Among  the  distilling  apparatus  intended  for  the 
distillation  of  wine  (not  of  mash),  and  so  constructed  as  to  be  fit  for  continuous 
working,  we  must  not  neglect  to  mention  the  apparatus  of  Cellier-Blumenthal,  as 
improved  by  Derosne,  and  represented  in  Fig.  531.  This  apparatus  consists  of  two 
stills,  A  and  A' ;  the  first  rectificator,  B ;  the  second  rectificator,  C ;  the  wine  warmer 
and  dephlegmator,  D  ;  the  condenser,  F ;  the  regulator,  E ;  a  contrivance  for  regulating 
the  flow  of  the  fluid  wine  from  the  cistern,  G.  The  still  A,  which,  as  well  as  the  still 
A',  is  filled  with  wine,  acts  as  a  steam  boiler.  The  low  wine  vapours  evolved  come,  when 
they  have  arrived  in  the  rectificators,  in  contact  with  an  uninterrupted  stream  of  wine, 
whereby  dephlegmation  is  effected ;  the  vapour  thus  enriched  in  alcohol  becomes  still 
stronger  in  the  vessel  Z),  and  thence  arrives  at  the  cooling  apparatus,  F.  In  order  that 
a  real  rectification  should  take  place  in  the  rectificators,  the  stream  of  wine  should  be 
heated  to  a  certain  temperature,  which  is  imparted  to  it  by  the  heating  of  the  condenser 
water.  The  steam  from  the  still  A'  is  carried  by  means  of  the  pipe  Z  to  the  bottom  of 
the  still  A.  Both  stills  are  heated  by  the  fire  of  the  same  furnace.  By  means  of  the 
tube  B'  the  liquid  contained  in  the  still  A  can  be  run  into  the  still  A'.  The  first 
rectificator,  £,  contains  a  number  of  semicircular  discs  of  unequal  size,  placed  one 
above  the  other,  and  which  are  so  fastened  to  a  vertical  centre  rod  that  they  can  be 
easily  removed  and  cleansed.  The  larger  discs,  perforated  in  the  manner  of  sieves,  are 
placed  with  their  concave  surfaces  upwards.  In  consequence  of  this  arrangement  the 
vapours  ascending  from  the  stills  meet  with  large  surfaces  moistened  with  wine,  which, 
moreover,  trickles  downwards  in  the  manner  of  a  cascade  from  the  discs,  and  comes, 


774 


CHEMICAL   TECHNOLOGY. 


[SECT.  vi. 


therefore,  into  very  intimate  contact  with  the  vapours.  The  second  rectificator,  C,  ia 
fitted  with  six  compartments;  in  the  centre  of  each  of  the  partition  walls  (iron  or 
copper  plates)  a  hole  is  cut,  and  over  this  hole,  by  means  of  a  vertical  bar,  is  fastened 
an  inverted  cup,  which  nearly  reaches  to  the  bottom  of  the  compartment  wherein  it  is 
placed.  As  a  portion  of  the  vapours  are  condensed  in  these  compartments  the  vapours 

are   necessarily    forced 

Fig-  S31-  through  a  layer  of  low  wine, 

and  have  to  overcome  a 
pressure  of  a  column  of 
liquid  2  centimetres  high. 
The  fore-warmer  and  de- 
phlegmator,  Z>,  is  a  hori- 
zontal cylinder  made  of 
copper  fitted  with  a  worm, 
the  convolutions  of  which 
are  placed  vertically.  The 
tube  M  commxmicates  with 
this  worm,  the  other  end 
of  which  passes  to  0.  A 
phlegma  collects  in  the  con- 
volutions of  this  tube,  which 
is  richer  in  alcohol  in  the 
foremost  windings  and 
weaker  in  those  more  re- 
mote :  this  fluid,  collecting 
in  the  lower  part  of  the 
spirals,  may  be  drawn  off  by 
means  of  small  tubes,  thence 
to  be  transferred,  at  the 
operator's  pleasure,  either 
all  or  in  part,  by  the  aid 
of  another  tube  and  stop- 
cocks, to  the  tube  0,  or 
into  the  rectificator.  By 
means  of  the  tube  L  the 
previously  warmed  wine  of 
the  clephlegmator  can  be 
run  into  the  rectificator. 
The  condenser,  F,  is  a  cylin- 
drical vessel  closed  on  all 
sides,  and  containing  a 
worm  communicating  with 
the  tube  0.  The  other  end 
of  the  condensing  tube  car- 
ries the  distillate  away. 
On  the  top  of  this  portion  of  the  apparatus  the  tube  K  is  placed,  by  means  of  which 
wine  is  run  into  the  dephlegmator.  The  cold  wine  flows  into  the  cooling  vessel  by 
the  tube  /.  When  it  is  desired  to  work  with  this  apparatus,  the  first  thing  to  be 
done  is  the  filling  of  the  vessels  A  and  A'  with  wine.  The  stop-cock,  U,  is  then  opened, 
whereby  the  tube  J,  the  condenser,  F,  and  the  dephlegmator  are  filled  with  wine.  The 
wine  in  the  still  A'  is  next  heated  to  the  boiling-point ;  the  steam  enters  the  tube  Z 
and  is  condensed  in  A  until  the  wine  here  is  heated  to  the  boiling-point  by  the  combined 


SECT,  vi.]  THE   MANUFACTURE  OF  SPIRITS.  775 

effect  of  the  steam  and  the  hot  gases  circulating  in  the  flue.  The  low  wine  vapour  then 
passes  to  the  rectificator,  B,  and  thence  into  the  worm  of  the  dephlegmator,  D,  where 
the  greater  portion  of  it  is  condensed,  the  phlegma  flowing  backwards  into  the  rectifi- 
cator. As  soon  as  the  fore- warmer  is  so  far  heated  that  the  hand  cannot  be  kept  in  the 
hot  wine,  the  stop-cock  of  the  vessel  E  is  opened,  and  the  distillation  commences.  The 
wine  which  is  conveyed  by  the  tube  J  into  the  cooling  vessel,  F,  soon  begins  to  become 
hot,  and  is  then  conveyed  to  the  fore-warmer,  where  its  temperature  becomes  nearly  as 
high  as  the  boiling- point ;  by  means  of  the  tube  L  this  fluid  is  conveyed  into  the  recti- 
ficator, £,  and  thence  into  the  still  A. 

As  soon  as  the  wine  in  the  still  A'  contains  no  more  alcohol,  the  stop-cock  fitted  to 
the  lower  part  of  the  vessel  is  opened,  and  the  vinasse  run  off  at  R,  the  still  being  re- 
supplied  by  opening  the  stop-cock  B'.  The  vapour  proceeds  in  the  same  way,  but  in  a 
reversed  direction ;  when  the  vapour  has  been  condensed  in  F  it  is  first  collected,  as 
alcohol,  in  the  small  vessel,  N,  provided  with  an  areometer,  and  thence  conveyed  to  the 
cistern,  H.  The  strength  of  the  alcohol  obtained  by  means  of  this  apparatus  increases 
with  an  increase  of  the  number  of  coils  of  the  condenser  placed  in  the  dephleg- 
mator and  connected  with  the  rectificator.  Practical  experience  decides,  according  to 
the  alcoholic  strength  of  the  wines  to  be  distilled,  and  the  quantity  of  pure  alcohol 
desired  in  the  distillate,  the  opening  or  shutting  of  the  various  stop-cocks  of  this 
apparatus.  Derosne's  apparatus  may  be  readily  made  continuous ;  for  this  purpose  it 
is  only  necessary  to  fill  the  reservoir,  condensing  apparatus,  and  rectificator  with  cold 
water,  while  the  lower  portion  of  the  tube  L  is  closed. 

Among  the  recent  continuous  action  apparatus  is  that  of  R.  Ilge.  It  consists  (Fig. 
532)  of  the  steam  regulator,  ABC,  the  mash-column,  D,  the  vinasse  regulator,  E, 
the  rectifier,  F,  and  the  dephlegmator,  G.  The  apparatus  is  chiefly  constructed  of 
cast-iron — only  the  cocks,  the  steam  damper,  C,  and  the  support  of  the  float  in  the 
vinasse  regulator  are  of  brass,  the  float  and  the  tubes  are  of  copper,  and  certain  rods 
are  of  wrought  iron.  The  function  of  the  steam  regulator  is  to  reduce  to  a  normal 
pressure  the  boiler-steam,  which  enters  through  the  cock,  d,  and  the  engine-steam, 
introduced  through  the  pipe,  b.  The  body  of  the  still,  A,  is  filled  with  water  up  to 
the  short  tube,  c,  which  is  pressed  up  by  the  steam  entering  by  d  through  the  tube  e 
to  the  float,  B.  The  float,  by  means  of  its  guide-rod,  communicates  its  movement 
downwards  to  the  plunger  of  C.  The  case  of  C  contains,  as  shown  in  the  drawing, 
two  mutually  superimposed  expansions,  f  and  g,  each  with  a  short  pipe.  Four  slits  in 
the  hollow  piston  connect,  according  to  the  movement  of  the  float,  the  interior  of  the 
piston  either  with  the  expansion  f  or  with  g,  or  with  neither  of  the  two.  As  long 
as  the  float  does  not  rise,  the  slits  convey  the  entire  steam  of  the  boiler  from  f .  The  rise 
of  the  float  cuts  off  the  steam  more  and  more,  and  as,  at  the  same  time,  the  escaping 
steam  from  the  engine  streams  in  through  b,  the  case  may  occur  that  the  slits  are 
exactly  covered  by  the  intervals  between  the  two  expansions,  or  extend  beyond  the 
expansion  g,  and  let  the  superfluous  steam  escape  into  the  open  air.  In  any  case  the 
piston  will  place  itself  so  that  the  pressure  of  the  steam  is  equal  to  the  column  of 
water  raised.  In  order  that  the  steam  boiler  is  not  filled  with  water  above  L,  a  tube, 
h,  is  inserted  through  which  the  steam  presses  the  water  up  and  down  without  itself 
escaping.  In  the  mash-column,  D,  the  boiling  mash  forms  a  continuous,  unbroken 
column  of  liquid.  From  the  cock  a'  the  regulated  steam  enters  through  the  short 
piece,  k,  into  the  space  between  the  vessel  1,  and  the  lowest  cy Under,  m,  passes  through 
the  vinasse  downwards,  and  streams,  equally  distributed,  in  an  upper  direction  into  the 
mash.  Ribs  are  cast  on  the  lower  surface  of  the  bottom  m,  and  through  their  inter- 
vals the  steam  enters  the  mash  in  the  same  direction  as  the  mash.  Hereby  the  liquid  is 
kept  in  a  rotatory  movement,  and  as  it  arrives  at  the  bottom  n  with  a  movement  in  the 
opposite  direction,  a  thorough  interpenetration  of  steam  and  mash  is  effected.  Tho 


776 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


ascending  vapours  collect  on  the  superjacent  floor,  o,  and  are  led  back  into  the  mash  by 
the  ribs,  but  with  a  rotation  to  the  left,  while  a  rotation  to  the  right  was  produced  by 
the  floor  n.  The  upward  passage  of  the  vapours  takes  the  same  form  ;  at  the  floor 
in  the  mash  is  turned  to  the  right,  and  every  floor  o  to  the  left.  A  plentiful  distilla- 


.  532. 


Explanation  of  Terms. 

Nach  H 1  ....  Across  Section  H  I. 
Nach  K  L  .  .  .  .  Across  Section  K  L. 
Nach  M  N  .  .  .  Across  Section  M  N. 


tion  takes  place  by  both  currents,  and  also  a  dephlegmation  on  the  upper  floors,  where 
the  vapours  meet  with  the  cold  mash  flowing  in  by  the  tube  p.  In  the  elevation  only 
two  ribs  are  shown,  but  on  the  ground  floor  we  see  the  whole  arrangement  of  the  ribs, 


SECT.    VI.] 


THE   MANUTACTURE   OF  SPIRITS. 


777 


Fig.  533- 


seen  from  below.  It  appears  from  the  drawing  how  the  floors  n  are  mounted  on  a 
wrought-iron  rod  by  means  of  sheaths,  and  how  the  floors  n  are  arranged  between 
two  cylinders,  m.  As  the  mash-column,  D,  during  working,  is  filled  with  mash  above 
its  highest  floor,  o,  the  vinasse,  which  had  entered  into  the  vinasse  regulator,  E, 
through  the  square  channel,  q,  has  risen  to  the  same  height  in  the  latter,  though  less 
high  than  in  D,  as  here  the  mash  is  specifically  lighter  than  the  vinasse.  The  float  in 
E  communicates  its  upward  movement  by  means  of  a  rod  to  the  vinasse  cock,  r,  and 
emits  through  the  latter  as  much  vinasse  as  mash  enters  through  the  pipe  p.  The 
development  of  steam  from  the  overheated  vinasse  (which  is  perceptible  in  large  works) 
is  rendered  innocuous  by  the  floors  s,  which  expedite  the  vapours  upwards,  and  at  the 
same  time  present  by  their  conical  sections  sufficient  room  for  the  ascending  and  de- 
scending vinasse.  The  floor  t,  resting  on  four  feet,  keeps  off  the  vapours  from  the  float. 
The  ascending  vapours  come  in  intimate  contact  with  the  liquid  dripping  down 
from  the  dephlegmator,  G.  The  rectifier,  F,  and  the  dephlegmator,  G,  have  four-sided 
sections.  F  is  filled  with  porcelain 
balls  from  the  grate  up  to  its  upper 
edge.  G  contains  a  number  of  copper 
tubes  laid  almost  horizontally  in  rows, 
among  which  the  cooling  water  flows 
upwards  from  row  to  row  by  means 
of  the  two  water-covers,  u.  To  each 
copper  tube  there  are  soldered  slips 
of  sheet-copper,  30  millimetres  in 
length,  6  millimetres  in  breadth,  and 
painted  below,  at  intervals  of  25  milli- 
metres from  each  other,  as  shown  in 
the  lowest  tube  in  the  figure.  The 
alcoholic  vapours  rising  out  of  the 
mash  pass  through  the  grate,  through 
the  intervals  of  the  porcelain  balls, 
through  the  intervals  of  the  cooling- 
tubes,  and  ultimately  through  the 
short  tube,  v,  to  the  spirit-cooler. 
Each  drop  which  is  formed  on  the 
cooling-tubes  runs  to  the  next  copper 
slip,  falls  off  from  its  point  to  the  next 
tube  below,  and  arrives  ultimately  at 
the  upper  layer  of  balls,  which  are 
uniformly  wetted  by  all  the  descending 
drops  as  they  trickle  downwards  from 
ball  to  ball.  Rectification  takes  place 
on  the  balls  and  on  the  moistened 
surfaces  of  the  pipes  and  the  slips. 

In  the  distilling  and  rectifying  ap- 
paratus of  Siemens  Brothers  &  Co. 
the  principal  parts  are : — The  pre- 
iminary  heater,  A,  the  mash-column, 
B,  and  the  rectifier,  C  (Figs.  533  to 

536),  formed  of  cast-iron  pieces,  held  together  by  the  long  bolts,  m,  and  with 
joints  rendered  air-tight  by  means  of  varnished  pasteboard.  In  working,  the  cham- 
bers b  of  the  preliminary-heater,  A,  and  a  part  of  the  support,  c,  are  full  of  hot 
vinasse ;  the  chambers  a  and  the  remaining  part  of  c  are  f  nil  of  cold  mash,  which 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


is  to  be  deprived  of  its  spirit,  which  obtains  a  preliminary  heating  by  withdrawing 
a  large  share  of  heat  from  the  adjacent  boiling  vinasse  before  passing  into  the  de- 
alcoholising  column,  B.  Accordingly,  the  mash,  which  is  pumped  up  at  d  into  the 
preliminary  heater,  traverses  in  succession  the  compartments,  a,  of  the  band,  D  (Fig. 
534),  falls  down  into  the  piece,  c,  underneath,  and  passes  through  a  wide  opening 
into  the  central  tube,  D,  in  which  it  rises  upwards  and  pours  at  f  into  the  mash- 
column,  B. 

This  column,  B,  consists  of  a  number  of  pieces,  with  central  tube  open  at  both  ends 
and  ring-shaped  perforated  bottoms  (Fig.  535).  The  space  beneath  this  bottom  serves 
for  collecting  and  receiving  the  vapours  rising  from  the  liquid  below,  whilst  the  space 
above  the  bottom  serves  to  receive  the  liquid  which  has  to  give  up  its  alcohol.  In  every 
one  of  these  nested  pieces  the  liquid  to  be  deprived  of  its  alcohol,  in  passing  through  the 
apparatus,  can  only  flow  round  in  one  direction,  and  not  quite  round,  because  a  perpen- 
dicular rib  hinders  the  annular  connection  of  the  liquid,  whilst  a  lower  opening  makes 
a  connection  with  the  liquid  in  the  next  lower  compartment.  In  consequence  of  this 
arrangement  of  the  column,  the  mass  is  so  thoroughly  de-alcoholised  that  the  heat  can 
be  used  over  again,  and  the  removal  of  the  alcohol  effected  at  the  cost  of  relatively  very 
little  heat. 


Fig.  534- 


frische  Maische 
heisse  Schlempe 


che 
Jaische. 

btisseSchltmpt. 


Fresh  mash. 
Hot  vinasse. 


Explanation  of  Terms. 


Dampfe 
Maische 


Vapours. 
Mash. 


Wosser  .  .  Water. 
hochgrtidige  Alkoholddmpfe : 

Strong  alcoholic  vapours. 
schwoche  Alkoholddmpfe  .• 
Weak  alcoholic  vapours. 


From  the  lowest  part  of  the  column,  B,  the  mash,  perfectly  freed  from  spirit,  passes 
as  vinasse  into  the  preliminary  heater,  traverses  the  chambers  b,  giving  off  a  consider- 
able quantity  of  heat  to  the  cold  mash  in  the  interposed  mash-chambers,  a,  and  flows 
off  continuously  at  K  from  the  vinasse  outflow  pipe,  I.  The  chambers,  a  and  b,  of  the 
preliminary  heater  having  sloping  bottoms,  both  mash  and  vinasse  flow  downwards ; 
hence  no  deposits  can  be  formed  in  the  chambers.  Grains,  &c.,  pass  into  the  piece,  c, 
which  keeps  them  back,  and  is  removed  every  two  or  three  months.  The  apparatus, 
when  working,  is  full  of  mash  up  to  the  gauge-glass,  n. 

The  alcoholic  vapours  liberated  from  the  mash  ascend  into  the  rectifier,  c.  It  con- 
sists of  a  number  of  cast-iron  pieces,  put  together  so  as  to  form  a  way  for  the  vapours 
rising  from  the  mash-column,  B,  and  partly  serve  to  receive  the  cooling- water,  which 
deprives  the  vapours  of  their  excess  of  heat  and  facilitates  the  process  of  rectification. 


SECT,  vi.]  THE.  MANUFACTURE  .OF  SPIRITS.  779 

The  vapours  pass  at  F  into  ;  the :  spirit-cooler  for  condensation,  whilst  the  phlegni 
formed  in  the  rectifier  collects  on  the  floors  of  the  chambers,  and,  if  it  is  not  re- 
evaporated  by  the  process  of  rectification,  flows  back  into  the  mash-column  by  an  in- 
ternal tube. 

The  cooling- water  takes  its  way  into  the  rectifier  at  i,  and  flows  off  at  h.  It  is 
convenient  to  let  this  cooling-water  first  act  on  the  spirit-cooler,  so  that  it  enters  the 
cooler,  S,  at  s,  and  then  flows  through  the  tube  t  into  the  rectifier  at  i. 

The  sensitive  indicator,  T,  gives  an  easy  and  certain  indication  whether  the  mash  is 
perfectly  de-alcoholised  .or  not.  It  must  be  considered  that  spirit,  distilled  in  cast-iron 
apparatus,  often  gets  a  bad  smell  and  taste,  by  taking  up  hydrocarbons  and  sulphuretted 
hydrogen. 

Purification  of  the  'Crude  Spirit  (De-fuseling). — In  working  up  crude  spirits  there 
are  obtained  two  products,  which  contain  the  impurities.  Some  of  the  ethers  thus  formed 
exhibit  a  highly  agreeable  odour,  and  are  therefore  used  in  perfumery,  and  for  the 
flavouring  of  sweetmeats,  bon-bons,  &c. 

As  for  many  of  the  applications  of  potato-spirit  the  fusel  oil  is  a  disadvantage, 
the  spirit  has  to  be  submitted  to  an  operation  of  rectification,  whereby  the  fusel 
oil  is  got  rid  of.  The  suggestions  which  have  been  made  for  this  purpose  refer 
either  to  the  destruction  of  the  fusel  oil  by  oxidation  or  the  action  of  chlorine,  or  of  the 
masking  of  the  oil  and  its  conversion  into  less  disagreeable  compounds  ;  partly  also  to 
a  real  removal  of  the  fusel  oil  from  the  spirit.  When  the  fusel  oil  containing  spirit  is 
rectified  over  chloride  of  lime  (bleaching- powder),  potassium  permanganate,  <fec.,  valeri- 
anate  of  fusel  ether  is  formed.  But  since  the  action  of  these  reagents  is  not  limited  to 
the  amylic  alcohol,  but  extends  to  the  ethylic,  it  is  very  difficult  to  adjust  the  quan- 
tity of  these  reagents  so  that  only  the  amylic  alcohol  be  acted  upon.  If  the  spirits 
from  which  the  fusel  oil  is  to  be  removed  are  treated  with  a  mixture  of  sulphuric  acid 
and  vinegar,  there  is  formed,  besides  some  acetic  ether,  amyl  acetate,  of  a  pleasant 
fruity  flavour.  Hydrochloric  and  nitric  acids,  also  used  to  remove  fusel  oil,  act 
in  a  somewhat  similar  manner.  The  most  approved  method  of  removing  the  fusel  oil 
is  by  means  of  well-burnt  charcoal  (vegetable  charcoal,  or 
bone-black),  which,  when  brought  into  contact  with  the 
crude  spirit,  absorbs  the  fusel  oil  mechanically.  By  the 
aid  of  charcoal,  spirits  and  brandy  (when  not  obtained  from 
wine)  are  purified  either  in  the  state  of  vapour,  or  by 
digestion  with  the  charcoal,  and  filtration  at  the  ordinary 
temperature  of  the  air  ;  rectification  at  boiling  temperature 
over  charcoal  is  altogether  unsuitable,  owing  to  the  fact  that 
the  fusel  oil  absorbed  by  the  charcoal  is  again  readily  dis- 
solved at  that  temperature.  The  charcoal  to  be  employed 
is  granulated  and  passed  through  a  sieve,  in  order  to  remove 
adhering  dust.  The  granulated  charcoal  is  placed  in  a 
copper  cylinder,  fitted  at  the  top  and  bottom  with  a  per- 
forated plate  or  disc.  This  cylinder  is  connected  with  the 
distilling  apparatus  between  the  dephlegmator  and  recti- 

ficator  in  such  a  manner  that  the  vapours  pass  through  the  charcoal.  To  100  litres  of 
brandy  to  be  purified,  3  to  5  litres  of  granulated  charcoal  are  generally  required ;  this 
can  be  again  employed  after  having  been  re-burnt  at  a  bright  red  heat.  Falkmann's 
apparatus  consists  of  a  helm-shaped  vessel,  A  (Fig.  537),  in  which  the  perforated  dia- 
phragms, b  b  b,  are  placed ;  upon  each  diaphragm  a  layer  of  charcoal,  surmounted  with 
a  cover,  c,  is  placed.  The  apparatus  is  closed  with  a  hollow  cover  containing  a  layer  of 
charcoal,  d  d.  The  vessel,  2,  is  surrounded  by  a  cooling  apparatus,  which  in  the  cut  is 
represented  by  the  cold-water  tubes,///,  and  the  hot- water  (which  becomes  hot  by 


780  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

the  passage  of  alcoholic  vapours  through  A)  tubes,  e  e  e  e;  these  serve  the  purpose  cf 
regulating  the  temperature  of  the  layers  of  charcoal. 

100  litres  of  Cognac  distilled  from  wine  contained,  according  to  Morin  (1887) — 

Aldehyde ;  trace 

Ethylic  alcohol 50*837 

Propylic  alcohol  (normal) 27*170 

Isobutylic  alcohol          .        .        .         .        i.'      .        .  6*520 

Amylic  alcohol      .        .        .        .        .        «      •  •        .  190*210 

Furfurol  bases        .         .         .         .     -   .        .        .         .  2*190 

Oil  of  wine ./.       ;.        .        .  7*610 

Acetic  acid trace 

Butyric  acid trace 

Isobutylglycol        .        .'        .        .        .        .         .         .  2*190 

Glycerine       .                 .......  4*380 

Butylic  alcohol  is  absent.  The  presence  of  furf urol  can  be  directly  shown  by  adding 
aniline  to  the  Cognac.  It  is  noteworthy  that  wine  contains  amylic  alcohol. 

Brockhaus  has  examined  by  experiments  upon  himself  the  action  of  the  most  im- 
portant impurities  of  potato-spirit :  aldehyde,  paraldehyde,  acetal,  propylic-isobutylic 
and  amylic  alcohol.  10  drops  of  aldehyde  in  100  grammes  of  water  had  a  repulsive, 
and  violently  burning  taste ;  there  was  a  sensation  of  burning  on  the  tongue 
and  in  the  throat,  a  repulsive  after-taste,  not  to  be  removed  by  frequent  draughts 
of  water,  cough,  feeling  of  suffocation,  nausea,  pain  in  the  stomach,  heat  in  the  head,  and 
palpitation  of  the  heart.  These  symptoms  passed  away  in  about  an  hour.  The  effects 
of  10  drops  of  aldehyde  in  wine  were  rather  less  unpleasant.  From  the  experiments 
with  amylic  alcohol  and  other  constituents  of  fusel  the  inference  seems  justified  that 
the  impurities  of  ordinary  spirits  play  a  leading  part  in  the  development  of  drunkard's 
diseases. 

Rabuteau  (1878)  found  on  analysing  i  litre  potato-fusel — 

c.c. 

Isopropylic  alcohol .  1 50 

Primary  propylic  alcohol 30 

Butylic  alcohol,  ordinary 50 

„            „        normal 65 

Secondary  amylic  alcohol  (methyl  propyl  carbinol)    .        .  60 

Ordinary  amylic  alcohol  (isobutyl  carbinol)        .        .         .  275 

Products  boiling  above  132°,  containing  amylic  alcohol      .  170 

Water 125 

Yield  of  Alcohol. — The  quantity  of  alcohol  obtainable  from  any  given  substance 
not  only  depends  on  the  relative  quantity  of  the  alcohol-forming  constituents  (starch, 
dextrose,  or  cane  sugar)  of  the  raw  material  applied  for  the  purpose  of  distillation, 
but  very  largely  also  on  the  more  or  less  suitable  mode  of  conducting  all  the  opera- 
tions of  the  spirit  distillation  (mashing,  fermentation),  in  properly  constructed 
apparatus.  Leaving  out  of  the  question  the  small  quantities  of  glycerine  and  succinic 
acid  formed  by  vinous  fermentation,  chemistry  teaches  that — 

100  parts  of  starch  yield  56*78  of  alcohol 

100        „       cane  sugar        „      53'8o        „ 
loo        „       dextrose  „      51*01         „ 

Experience  shows  that  the  yield  of  alcohol  is  in  practice  less  than  it  should  be, 
premising  that  every  mol.  of  starch  or  sugar  yields  2  mols.  of  alcohol ;  100  parts  of 
cane  sugar  do  not  yield  in  practice  the  quantity  of  alcohol  above  indicated,  viz.,  53*8 
parts,  but  only  51*1. 


SECT,  vi.]  FLOUR  AND  BREAD.  781 

loo  kilos,  of  barley  give  44-64  litres  of  corn  brandy  at  50°  Tralles 
loo        „        barley  malt      „    54-96        „          „          „  „          „ 

100        „       wheat  „    49-22        „          „          „          M         |f 

100        »       !7e  it    45'So        „          „          „          „         „ 

loo        „       potatoes  „    18-32        „      potato  spirit      „         „ 

6  litres  (quart  or  maas)  of  brandy,  from  the  metrical  hundredweight  (hectolitre,  <fcc.), 
is  reckoned  to  yield  6  x  50  =  300  per  cent,  alcohol ;  7  litres,  consequently,  350  ;  8  litres, 
400.  8  litres  at  48  per  cent.  Tralles  =  384  per  cent,  alcohol.  The  number  of  litres  of 
brandy  or  spirit  multiplied  by  the  alcohol  in  percentage  according  to  Tralles  therefore 
yield — 

I  metrical  cwt.  of  barley  44 '64  x  50=2232  per  cent,  alcohol 

i        „  „       barley  malt   54-96x50=2748        „  „ 

I        „  „        wheat  49-22x50=2461        „  „ 

I        „  „        rye  45*80x50=2290        „  „ 

i        „  „        potatoes        18-32x50=  916        „  „ 

FLOUR  AND  BREAD. 

Modes  of  Bread  Making. — The  preparation  of  bread  aims  at  the  production  in  the 
flour  obtained  by  grinding  up  the  cereals  of  such  a  chemical  and  physical  condition  as 
will  tend  to  render  it  most  readily  masticated  by  the  teeth,  and,  after  having  been  duly 
mixed  with  saliva  in  the  mouth,  digested  by  the  juices  of  the  stomach.  When  flour 
is  mixed  with  water  so  as  to  form  a  dough,  and  this  mixture  dried  at  the  ordinary 
temperature  of  the  atmosphere,  a  kind  of  cake  is  obtained  which  contains  the  starch 
unaltered  and  in  an  insoluble  state,  so  that  this  kind  of  cake  is  very  difficult  to  digest, 
while,  moreover,  its  taste  is  so  unpleasant  as  to  create  no  appetite.  Again,  if  the  cake 
is  dried  at  the  boiling-point  of  water,  it  becomes  like  a  dried  starch-paste,  which  is  also 
very  difficult  to  digest.  When  this  temperature  only  acts  upon  the  surface  of  such  dough, 
and  does  not  penetrate  into  the  interior,  the  resulting  cake  will  be  a  mixture  somewhat 
similar  to  ship's  biscuit,  which  may  always  be  considered  as  a  strongly  dried  dough, 
and,  although  it  may  be  preserved  for  almost  any  length  of  time,  it  is  far  less  digestible 
than  bread.  The  object  of  the  baking  process  is  to  impart  to  the  dough  so  high  a  degree 
of  heat  as  to  render  the  starch  soluble,  while  it  is  further  desired  to  form  a  light  spongy 
mass,  instead  of  a  brittle  or  watery  paste ;  the  heat  should  be  strong  enough  to  torrify 
and  roast  the  outer  surface  of  the  bread  mass  to  such  an  extent  as  to  form  a  deeply 
coloured  crust,  whereby  not  only  the  taste  of  the  bread  is  greatly  improved,  but  it  can 
also  be  kept  in  good  condition  for  some  time.  The  usual  means  of  rendering  dough 
spongy  is  by  vinous  fermentation  set  up  by  the  addition  of  a  ferment,  this  being  either 
leaven  or  yeast;  a  small  portion  of  the  starch  of  the  flour  is  thus  converted  into 
glucose,  which  is  then  decomposed,  yielding  alcohol  and  carbonic  acid  gas ;  the  latter 
is  prevented  from  escaping  by  the  toughness  of  the  dough,  which  is  thereby  rendered 
spongy. 

The  alcohol  is  of  no  consequence  whatever.  White  bread  is  prepared  with 
wheaten  flour  and  yeast ;  rye  meal,  or  a  mixture  of  rye  meal  and  wheaten  flour, 
with  leaven,  yields  "  black"  or  rye  bread.  Heeren  found  that  flour  in  the  state 
in  which  it  is  usually  applied  for  bread  baking  contains  an  average  of  13  per  cent, 
moisture. 

The  Details  of  Bread  Baking. — The  raw  materials  in  the  preparation  of  bread  are 
flour,  water,  and  a  ferment ;  salt,  spices,  &c.,  are  also  used.  The  composition  of  the 
most  important  kinds  of  flour  and  meals  is  as  follows  : — 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


Water     . 

Albumen .         . 

Vegetable  glue 

Casein     . 

Fibrin      . 

Gluten     . 

Sugar 

Gum        .         . 

Fat 

Starch     . 

Sand 


15:54 
i'34 
176 
o'37 
5-19 
3 'So 
2-33 
6-25 
1-07 

63-64 


b. 

14-60 
i-56 
2-92 
0-90 
7-36 


4*10 
i  -80 

64-28 


c. 

14-00 
i -20 
3-60 

i '34 

8-24 

3 '04 
6-33 

2-23 

53T5 
6-85 


d. 

11.70 
1-24 

3-25 

0-15 

14-84 

2-19 

2-81 

5-67 

58-I3 


a.  Wheat  flour.     6.  Kye  meal.     c.  Barley  meal.     d.  Oatmeal. 


In  addition  to  these  kinds  of  meal,  those  derived  from  Zea-Ma'is  (Indian  corn),  beans, 

&c.,  are  occasionally  employed  for  making  bread. 
The  principal  phases  of  the  preparation  are  : — 

The  Mixing  of  the  Dough. — The  mixing  of  the  flour  with  water  is  the  first  mani- 
pulation of  the  baking  process.  The  object  of  this  operation  is  first  to  render  dextrine 
and  sugar  (owing  to  the  action  of  the  gluten  upon  the  starch,  the  quantity  of  sugar 
becomes  increased  while  the  mixing  process  is  going  on)  and  some  albuminous  sub- 
stances soluble,  and  next  to  mix  the  solution  thus  formed  thoroughly  with  the 
starch  and  gluten  of  the  flour,  and  to  soak  and  somewhat  dissociate  these  substances ; 
dry  yeast  or  leaven  is  at  the  same  time  admitted  to  the  bread  mass,  the  former  ferment 
being  used  when  it  is  intended  to  make  white,  the  latter  when  black  bread  is  desired  to 
be  made. 

By  sour  dough  or  leaven  is  understood  that  portion  of  the  already  fermenting 
dough  which  is  set  apart  and  kept  for  the  next  baking  operation ;  it  consists  of  a 
mixture  of  flour  and  water,  in  which  a  portion  of  the  starch  is  converted,  partly 
into  sugar,  which  is  again  changed  by  vinous  fermentation,  and  acetic  acid,  but 
chiefly  into  lactic  acid,  by  a  process  of  fermentation,  set  up  by  the  peculiar  conversion 
into  active  ferments  of  the  protein  compounds  of  the  flour  itself.  Leaven,  therefore, 
acts  as  a  fermentation-producing  substance  in  a  fresh  batch  of  dough,  its  action  being 
similar  to  that  of  yeast,  or  of  already  fermenting  wort  when  added  to  a  freshly  made 
wort.  After  a  length  of  time  the  leaven  becomes  putrid  and  unfit  for  use  as  a  fer- 
ment. As  regards  the  quantity  of  leaven  to  be  used  with  the  dough  nothing  definite 
can  be  said,  since  it  depends  as  much  on  the  degree  of  sourness  of  the  leaven  as  on  the 
quality  of  the  bread  intended  to  be  made ;  usually,  4  parts  of  leaven  are  added  to  100 
parts  of  flour,  or  to  80  parts  of  bread  3  parts  of  leaven.  In  the  case  of  white  bread,  100 
parts  of  flour  require  2  parts  of  dry  yeast.  The  mixing  of  the  flour  is  effected  with 
lukewarm  water,  at  a  temperature  of  from  21°  to  37°. 

Kneading. — The  thin  dough  obtained  from  flour,  water,  and  ferment  is  dredged 
over  with  dry  flour,  and  placed  in  a  warm  situation  for  a  time,  generally  during  the 
night.  Fermentation  is  thus  set  up  by  the  action  of  the  ferment  upon  the  dextrose 
of  the  dough,  the  carbonic  acid  developed  rendering  the  dough  spongy.  The  sponge 
thus  prepared  is  next  mixed  with  more  flour,  to  bring  it  to  the  consistency  required 
for  the  baking,  this  operation  being  known  as  the  kneading  of  the  sponge.  The 
method  usually  employed  in  these  operations  is  that  one-third  of  the  total  quantity 
of  flour  required  for  a  batch  is  mixed  first  with  water  and  ferment,  and  when  this 
mass  has  come  into  full  fermentation,  the  two  other  thirds  of  flour  are  kneaded  up 
along  with  the  sponge,  sufficient  water  being  added  to  form  a  normal  dough.  After 
the  kneading  operation  the  dough  is  again  dredged  over  with  some  dry  flour,  and  left 
in  a  warm  situation  for  the  purpose  of  becoming  thoroughly  spongy ;  for  this  con- 
tinued fermentation  only  about  half  the  time  is  required  for  the  first-mentioned 


SECT.  VI.] 


FLOUR  AND   BREAD. 


783 


fermentation.  In  most  bakeries,  however,  this  second  fermentation  is  not  proceeded 
with,  but  the  dough  is,  immediately  after  having  been  kneaded,  cut  up  and  shaped 
into  loaves. 

By  means  of  the  kneading  the  dough  becomes  squeezed  together,  and  has,  there- 
fore, again  to  be  left  in  a  warm  situation  for  further  fermentation,  during  which  it 
heaves  up  and  increases  to  double  its  size.  The  bulk  of  the  dough  increases  twofold. 
When  rye  bread  is  made,  the  dough  is  frequently  moistened  on  its  external  surface 
with  lukewarm  water,  applied  by  the  aid  of  a  brush,  in  order  to  prevent  cracks  in  the 
outer  coating  of  the  dough  by  the  evaporation  of  the  water  ;  just  before  putting  the 
loaves  into  the  oven  this  brushing  over  with  water  is  repeated.  The  water  softens  the 
outer  surface  of  the  dough,  and  dissolves  some  of  the  dextrine  it  contains,  which  sub- 
stance, after  the  evaporation  of  the  water  from  the  surface,  remains  as  a  glaze  upon 
this  kind  of  bread.  When  the  loaves  have  risen  sufficiently  and  exhale  a  peculiar 
vinovis  odour,  it  is  time  to  commence  the  baking  process.  Since  the  bread  loses  consider- 
ably in  weight  during  the  baking,  the  baker  must  proportion  so  much  dough  to  each 
loaf  before  baking  as  will  yield  the  legal  weight  of  the  baked  bread.  The  weight  of 
dough  to  be  proportioned  to  a  loaf  of  a  certain  fixed  weight  varies  according  to  the 
size  of  the  loaf ;  but  increases  comparatively  with  decrease  therein.  The  dough 
generally  loses  in  baking  about  25  per  cent,  of  its  weight.  The  smaller  the  loaf,  the  more 
crust  in  proportion  to  crumb;  and  since  the  crust  contains  less  moisture,  and  consequently 
weighs  less  than  the  crumb,  the  loss  of  weight  is  proportionately  greater  in  a  small  than 
in  a  large  loaf. 

The  use  of  machinery  in  kneading  dough  is  gradually  extending,  and  it  will  doubt- 
less become  general  wherever  bread  is  prepared  on  the  large  scale. 

Baking. — The  conversion  of  the  fermented  dough  into  bread  is- effected  by  baking 
in  ovens,  the  common  kind  of  which  consists  of  a  round  or  oval  hearth,  covered  with  a 

Fig-  538. 


Explanation  of  Terms. 

Schnitt  1U-IV.    .        .        .         Section  ITI.-IV. 
Schnitt  I-IL         .        .        .         Section  I.-II. 


Explanation  of  Terms. 
Schnitt   V-VI.       .        .       Section  V.-VI. 
Schnitt  VII-VIII.         .       Section  VII.-VIII. 


vault.  Far  more  advantageous  are  the  ovens  heated  from  below,  which  allow  of  un- 
interrupted work  with  a  smaller  consumption  of  fuel  and  greater  cleanliness.  In 
Seidel's  oven,  e.g.,  the  baking-room,  A  (Figs.  538  to  540),  rests  on  stones  forming 


784  CHEMICAL  TECHNOLOGY.  [SECT,  vi 

parallel  channels,  whilst  the  actual  hearth  is  kept  at  some  distance  from  the  side  by 
cubic  stones,  so  as  to  form  the  hollow  space,  w.  On  both  sides  of  the  baking-space, 
A,  the  flues  z  are  formed,  through  which  the  air  heated  by  the  fire-gases  passing  in 
the  flues  i  rise  up  and  enter  the  baking-space,  A.  The  sole  of  the  space  c  is  provided 
with  an  opening  on  both  sides,  which  can  be  closed  by  means  of  the  dampers  moved 
by  the  hand-levers,  h,  and  through  which  the  heat,  when  the  firing  is  completed,  can 
be  passed  directly  into  w  or  A.  To  the  flues  i,  underneath  which  there  crosses  a 
cleansing  flue,  x,  there  are  joined  the  flues  c,  which  rise  up  at  the  rear- wall  of  the 
baking-space,  and  extend  to  the  flues  a,  with  the  openings  for  cleansing,  y.  Tho 
flues  c  and  a  are  so  arranged  that  the  heat  in  each  two  flues  i  and  c  passes  forwards 
in  each  one  of  the  flues  a,  turns  round  backwards  in  the  second  of  the  flues  a,  as 
shown  by  arrows  on  the  left  hand  of  Fig.  540,  in  order  to  escape  into  a  general  flue,  n, 
opening  into  the  chimney,  S.  From  the  water-pan,  e,  a  pipe,  d,  leads  to  the  steam 
generator,  /.  The  pipe  g  conveys  the  steam  into  the  baking-space,  A,  whilst  the 
steam-escape,  o,  which  vents  into  the  flue  n,  is  regulated  by  cross-valves  and  a  draught 
arrangement,  b. 

The  temperature  of  the  furnace  suitable  for  baking  is  200°  to  225°.  Before  the 
loaves  are  introduced  into  the  oven  their  surface  is  brushed  over  with  water  in  order 
to  prevent  the  crust  from  bursting  in  consequence  of  the  too  rapid  action  of  a  high 
temperature.  The  watery  vapours  with  which  the  oven  is  gradually  filled  are  neces 
sary  in  order  to  convert  the  starch  into  dextrine  on  the  surface  of  the  bread,  and  thus 
obtain  a  smooth  crust.  The  time  required  for  baking  depends  on  the  size,  the  shape, 
and  the  kind  of  the  loaves.  Black  bread  requires  a  longer  time  than  white. 

Substitutes  for  Yeast  in  Baking. — We  have  seen  from  the  preceding  details  that  the 
preparation  of  bread  is  essentially  based  upon  the  fact  that  by  the  act  of  fermentation 
the  gluten  of  the  flour  forms  a  kind  of  cellular  tissue  by  which  the  escape  of  the 
carbonic  acid  is  prevented,  and  the  bread  thus  rendered  porous  and  spongy,  whereby 
its  digestibility  is  increased.  This  quality  of  the  bread  is  obtained  at  the  cost  of  a 
portion  of  the  starch  of  the  flour,  which  is  first  converted  into  starch-sugar,  and  then 
by  means  of  fermentation  into  alcohol  and  carbonic  acid  gas ;  to  the  expansion  of  the 
latter  the  bread  owes  its  spongy  texture.  Many  attempts  have  been  made  for  the 
purpose  of  effecting  the  "  raising  "  of  the  bread,  as  it  is  termed,  without  the  use  of  a 
ferment,  by  introducing  into  the  dough  some  gas-  or  vapour -producing  substance, 
which  would  have  the  same  mechanical  effect  at  least  as  the  carbonic  acid  derived  from 
the  fermentation.  Although  the  problem  of  preparing  bread  of  good  quality  without 
the  aid  of  fermentation  cannot  be  said  to  be  quite  settled,  many  proposals  have  been 
made  in  this  direction,  and  some  of  these  deserve  notice ;  we  therefore  quote  the  most 
important.  When  ammonium  sesquicarbonate  (the  so-called  sal  cornu  cervi  of 
pharmacy)  is  added  in  small  quantity  to  the  dough,  it  will  cause  the  raising  of  the 
same,  partly  because  some  acid  is  always  present  in  the  dough,  whereby  the  salt  is 
decomposed  and  carbonic  acid  set  free,  partly  because  by  the  heat  of  the  oven  the  salt 
is  volatilised,  and,  by  assuming  the  state  of  vapour,  causes  the  expansion  and  consequent 
sponginess  of  the  dough.  Liebig  recommends  the  addition  of  sodium  bicarbonate  and 
hydrochloric  acid  to  the  dough,  the  carbonic  acid  being  evolved  according  to  the 
formula  NaHCO3  -f  HC1  =  NaCl  +  H2O  +  C02,  with  the  formation  of  common  salt, 
which  remains  in  the  dough.  The  proportions  are  as  follows  : — To  100  kilos,  of  meal 
for  making  black  bread  i  kilo,  of  sodium  bicarbonate  is  taken,  and  4^25  kilos,  of  hydro- 
chloric acid  of  1*063  8P-  gr-  (  =  9'5°  B.  =  13  per  cent.  C1H),  yielding  175  to  2  kilos,  of 
common  salt;  the  quantity  of  water  to  be  added  amounts  to  from  79  to  80  litres. 
From  this  mixture  is  obtained  150  kilos,  of  bread.  The  proportion  of  the  sodium  bi- 
carbonate to  the  hydrochloric  acid  is  so  arranged  that  5  grammes  of  the  former  are  fully 
saturated  by  33  c.c.  of  the  latter,  leaving  in  the  bread  a  faintly  acid  reaction.  The 


SECT,  vi.]  FLOUR  AND   BREAD.  785 

substance  known  and  sold  as  Horsford's  yeast  powder,  also  recommended  by  Liebig,  is 
preferable  and  more  readily  employed.  This  powder  consists  of  two  separate  prepara- 
tions, viz.,  the  acid  powder  (acid  calcium  phosphate  with  acid  magnesium  phosphate), 
the  other  the  alkaline  powder  (a  mixture  of  500  grammes  of  sodium  bicarbonate  and 
443  grammes  of  potassium  chloride).  To  100  kilos,  of  flour,  2'6  kilos,  of  the  acid  powder 
and  i '6  kilo,  of  the  alkali  powder  are  added.  During  the  kneading  the  following 
changes  occur  : — The  sodium  bicarbonate  and  potassium  chloride  are  first  converted 
into  sodium  chloride  and  potassium  bicarbonate,  the  latter  salt  being  in  its  turn 
decomposed  by  the  acid  phosphate,  whereby  carbonic  acid  is  set  free.  By  the  use  of 
this  baking  powder  it  is  possible  to  make  flour  into  bread  within  two  hours'  time, 
while,  moreover,  100  pounds  of  flour  yield  10  to  12  per  cent,  more  bread  than  with 
the  best  method  of  baking  in  the  usual  way.  The  plan  of  incorporating  pure 
carbonic  acid  gas  with  the  dough  has  been  frequently  taken  up,  and  successful  work 
has  been  done  in  this  direction,  but  the  process  has  its  opponents  as  well  as  its 
defenders. 

Yield  and  Composition  of  Bread. — Flour  from  various  kinds  of  grain  contains 
in  its  ordinary  air-dry  condition  from  12  to  1 6  per  cent,  of  water ;  by  its  conversion 
into  bread  the  flour  takes  up  much  more  water.  100  Ibs.  of  fine  wheaten  flour 
combine  with  50  Ibs.  of  water,  and  give  150  Ibs.  of  bread.  The  composition  of  the 
flour  and  of  the  bread  is,  therefore,  as  follows  : — 

Wheaten  Flour.  Wheaten  Bread. 

Dry  Flour 84  ...  84 

Water  originally  contained  in  the  flour         16  ...  16 

Water  added  for  making  the  dough      .        —  ...  50 

100  ...  150 

According  to  Heeren,  100  Ibs.  of  wheaten  flour  yield  at  least  125  to  126  Ibs. 
of  bread;  100  Ibs.  of  rye  meal,  131  Ibs.  of  bread.  Fresh  wheaten  bread  contains 
9  per  cent,  of  soluble  starch  and  dextrin,  40  per  cent,  of  unchanged  starch,  6'5 
per  cent,  of  protein  compounds,  and  from  40  to  45  per  cent,  of  water.  As  is  generally 
known,  newly  baked  bread  possesses  a  peculiar  softness,  and  is  at  the  same  time  tough 
and  does  not  crumble  readily  :  after  one  or  more  days'  keeping,  the  bread  loses  this 
softness,  becomes  dry,  crumbles  readily,  and  is  then  called  stale  or  old  bread ;  it  is 
usually  supposed  that  this  change  is  due  to  a  loss  of  water,  but,  according  to  the 
researches  of  Boussingault,  stale  bread  contains  as  much  water  as  fresh  bread ;  the 
alteration  is  solely  due  to  a  different  molecular  condition  of  the  bread. 

Impurities  and  Adulterations  of  Bread. — When  the  flour  intended  for  the  pre- 
paration of  bread  is  more  or  less  decayed,  the  gluten  it  contains  is  thereby  altered ; 
the  carbonic  acid  evolved  during  the  fermentation  of  the  bread  does  not  render 
the  dough  spongy,  but  it  becomes,  owing  to  the  altered  state  of  the  gluten,  a 
more  or  less  slimy  mass,  which  yields  a  tough  and  far  less  white-coloured  bread ;  in 
order  to  counteract  this  defect,  and  to  impart  a  good  appearance  to  the  bread  made 
from  flour  which  has  been  damaged  by  damp,  or  by  having  been  too  closely  con- 
fined in  casks  and  thereby  heated,  the  bakers  in  Belgium  and  Northern  France 
add  to  the  dough  a  small  quantity  of  copper  sulphate,  y-^^jj  to  -goooo  >  ^e  ^ase 
of  this  salt  combines  with  the  gluten,  forming  therewith  an  insoluble  compound, 
thus  rendering  the  dough  tough  and  white,  and  capable  of  taking  a  large  quantity  of 
water.  In  order  to  detect  the  copper  sulphate  in  the  bread,  a  portion  of  the  bread 
to  be  operated  upon  is  first  dried,  then  ignited,  and  the  copper  separated  from  the  ash 
by  gently  washing  away  the  lighter  particles,  leaving  the  metallic  copper  in  the  shape 
of  small  shining  spangles. 

In  England  alum  was  at  one  time  very  generally  added  to  flour  and' bread.  But 

3D 


786 


CHEMICAL  TECHNOLOGY. 


[SECT. 


VI. 


this  fraud,  which  was  always  illegal,  has  been  practically  suppressed  since  the  appoint- 
ment of  public  analysts.  In  Germany  the  addition  of  copper  sulphate  and  of  alum  is- 
forbidden  by  the  authorities. 

MILK,  BUTTER,  CHEESE. 

Milk. — Cows'  milk  contains,  according  to  the  race  of  the  animals,  the  kind  of 
feeding,  &c : — 

Per  cent. 

Total  solids 6-8-17-1 

Fat i-4-7'2 

Albuminates 2 '2- 6 '2 

Sugar        .         .         .         s        .     •   .        .         .         I '0-5 '2 
Salts 0-1-17 

A  verage  samples  of  total  milk  taken  morning,  noon,  and  evening  in  three  different 
cow-houses  contained,  according  to  ThOrner,  1885  : — 


Time  of  Milking. 

Spec.  Grav.- 

Cream. 

Fat. 

Total  Solids. 

Ash. 

Entire  Milk. 

Skim  Milk. 

I. 

Vol.  per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Morning 

I  '0306 

I-0325 

7-0 

2-460 

lO'So 

0-57 

Noon     .... 

I  -0304 

I  '0320 

9-0 

3-460 

1  2  '2O 

0-58 

Evening         .         .         . 

1-0311 

I  -0332 

S-o 

2-940 

11-50 

0-60 

II. 

Morning 

1-0314 

I  -0329 

6-5 

2-620 

"'37 

0-65 

Noon     .... 

1-0309 

I  -0339 

9-8 

3  '470 

12-09 

0-68 

Evening         .         .         . 

I  -0303 

1-0317 

8-0 

3-230 

H'74 

075 

III. 

Morning 

I  -0294 

I  -0324 

I  HO 

3-470 

1  1  -80 

074 

Noon     .... 

I  '0289 

I  -0326 

11  '5 

4-004 

12-15 

0-66 

Evening 

I  "0302 

I  -0324 

13-5 

4-6^0 

12-91 

0-65 

Lot  I.  consisted  of  the  milk  of  twenty- five  cows,  each  fed  daily  with  10  to  12^ 
kilos,  brewery  grains,  i  kilo,  of  a  cattle-food  (containing  14  per  cent,  protein  and  38- 
per  cent,  of  non -nitrogenous  extractive)  and  green  food,  with  hay  and  straw  as- 
required. 

Lot.  II.  comprised  the  milk  of  thirty-two  cows,  fed  on  80  litres  rye-vinasses  and 
6  kilos,  of  hay. 

Lot  III.  was  obtained  from  twelve  cows,  half  pasturage  and  half  stall-fed.  The 
latter  consisted  of  red  clover  with  Italian  rye-grass  and  0*25  kilo,  of  cotton-seed  cake- 
and  i  kilo,  of  crushed  rye. 

The  composition  is  hence  very  variable.* 

If  we  subtract  the  fat  from  the  dry  substance  we  obtain  a  figure  which  varies  but 
little. 

Milk  is  a  mixture  of  several  insoluble,  very  minutely  divided,  emulsified  substances,, 
suspended  in  a  watery  liquid.  The  specific  gravity  of  milk  varies  from  1-030  to  1*045^ 
Under  the  microscope  it  becomes  evident  that  the  white  colour  of  milk  is  due  to  the 
so-called  milk  globules — small  globular  bodies  of  a  yellow  colour,  with  a  more  deeply 
coloured  circumference,  and  exhibiting  a  pearly  gloss.  It  was  formerly  believed  that 
these  globules  consisted  of  an  exterior  envelope  filled  with  butter,  but  the  recent 
researches  of  Drs.  Von  Baumhauer  and  F.  Knapp  have  proved  these  opinions  to- 
be  eironeous.  When  milk  is  left  standing  these  globules  rise  to  the  surface  and  form 
cream,  below  which  remains  a  blue  transparent  fluid  containing  the  sugar  of  milk, 
salts,  and  caseine,  the  latter  in  the  form  of  caseine-soda.  When  milk  is  kept  for  some 

*  Compare  Wanklyn's  treatise  on  the  Analysis  of  Milk.  London:  Kegan  Paul,  Trench, 
Trubner  &  Co. 


SECT,  vi.]  MILK,   BUTTER,   CHEESE.  787 

time,  a  portion  of  the  lactose  (sugar  of  milk)  is  decomposed  and  converted  into  lactic 
acid  by  the  aid  of  the  caseine,  which  acts  as  a  ferment.  In  its  turn  the  lactic  acid 
decomposes  the  caseine-soda,  whereby  the  caseine  is  set  free  and  separated  as  an 
insoluble  substance;  this  action  takes  place  in  the  coagulation  of  milk.  The  whole 
of  the  lactose  or  sugar  of  milk  becomes  converted  into  lactic  acid  by  long  keeping. 

Lactic  acid  (C3H602)  is  also  formed  by  the  fermentation  of  starch,  cane  sugar,  and 
glucose,  under  the  influence  of  caseine  and  a  ferment.  This  acid  is  met  with  in 
sauerkraut  (a  favourite  dish  of  the  Germans,  being  a  well-preserved  mixture  of  white 
and  savoy  cabbages  cut  into  shreds,  and  packed  in  casks  along  with  salt,  coarse  pepper, 
and  some  water)  and  in  other  pickles,  in  beer,  and  in  nearly  all  animal  liquids.  Lactic 
acid  is  also  present  in  some  of  the  fluids  of  the  tan-yard  tanks;  in  the  sour  water 
of  starch  works  where  starch  is  prepared  by  the  old  methods  ;  in  the  bran  baths  of 
dye  works  ;  and  is  constantly  met  with  in  the  residual  liquids  of  corn  spirit  distilla- 
tion. When  lactic  acid  is  heated  with  sulphuric  acid  and  peroxide  of  manganese, 
aldehyde  is  formed,  which  is  used  in  the  preparation  of  aniline  green  and  of  hydrate  of 
chloral. 

The  coagulation  of  fresh  milk  is  effected  by  the  use  of  rennet,  which  is  prepared 
from  the  stomach  of  a  calf,  well  washed  and  stretched  out  on  a  wooden  frame,  then 
dried  either  in  the  sun  or  near  a  fire.  The  substance  thus  prepared  was  formerly  soaked 
in  vinegar,  but  experience  has  proved  this  to  be  unnecessary.  When  required,  a  small 
piece  is  cut  off  and  steeped  in  warm  water,  and  the  liquid  added  to  the  milk,  previously 
heated  to  from  30°  to  35°.  The  milk  is  hereby  coagulated,  even  in  large  quantity,  in  about 
two  hours;  i  part  of  rennet  is  sufficient  for  the  purpose  of  coagulating  1800  parts  of 
milk.  The  mode  of  action  of  rennet  is  not  well  understood,  but  it  does  not  consist,  as 
was  formerly  believed,  in  the  instantaneous  conversion  of  a  portion  of  the  lactose 
present  in  milk  into  lactic  acid,  since  experiments  have  shown  that  rennet  coagulates 
milk  which  exhibits  an  alkaline  reaction. 

Whey.  —  By  the  term  whey  is  understood  the  fluid  in  which  the  coagulated  caseine 
of  milk  floats,  and  which  may  be  obtained  either  by  decantation  or  filtration.  The 
whey  of  sour  milk  contains  very  little  lactose  and  a  large  quantity  of  lactic  acid  (sour 
whey)  ;  while  sweet  whey,  obtained  by  coagulating  milk  with  rennet,  contains  all  the 
lactose.  Sweet  whey  containing  3  to  4  per  mille  of  a  proteine  compound  (termed  lacto- 
proteine  by  Millon  and  Commaille)  is  evaporated  to  some  extent  in  Switzerland,  with 
the  view  of  obtaining  the  sugar  of  milk  in  a  crystalline  state.  The  substance  thus 
obtained  is  purified  by  recrystallisation. 

Lactose  (Sugar  of  Milk),  C12H22On  +  H.,0,  does  not  possess  a  very  sweet  taste,  and 
feels  sandy  in  the  mouth.  It  is  soluble  in  6  parts  of  cold  and  2  parts  of  hot  water. 
It  is  not  capable  of  alcoholic,  but  only  of  lactic  acid  fermentation.  By  the  action  of 
dilute  acids  sugar  of  milk  is  converted  into  galactose,  a  kind  of  sugar  similar  to  grape 
sugar,  and  is  then  capable  of  alcoholic  fermentation.  Industrially,  sugar  of  milk  is 
sometimes  employed  for  the  purpose  of  reducing  a  silver  solution  to  the  metallic  state, 
as  in  the  case  of  looking-glass  making.  100  parts  of  the  commercial  sugar  of  milk 
from  Switzerland  (a),  and  from  Giesmannsdorf  in  Silesia  (b),  were  found  to  consist 

(  1  868)  of:— 

a.  b. 

Salts  .        .        .        .        .        .        0-03  ...  0-16 

Insoluble  matter        .        .        .        0*03  ...  0^05 

Foreign  organic  substances       .         1*14  ...  1*29 

Sugar  of  milk    ....      98-80  ...  98*50 


Uses  0/J/t7&.—  Milk  is  used  as  food  and  for  the  preparation  of  butter  and  cheese, 
for  clarifying  wine  in  order  to  render  it  less  deep-coloured  and,  if  turbid,  quite  clear. 


788  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

More  recently  milk  has  been  largely  sold  in  the  so-called  condensed  state,  by  which  is 
understood  milk  evaporated  in  vacua,  after  the  addition  of  sugar,  to  the  consistency  of 
thick  honey.  This  mode  of  preserving  milk  was  first  employed  by  the  Anglo-Swiss 
Condensed  Milk  Company  at  Cham,  Canton  Zug,  Switzerland,  and  is  now  carried  on 
in  various  parts  of  the  Continent  and  in  the  United  States,  and  also  in  England,  in 
Surrey  and  Buckinghamshire. 

The  average  composition  of  condensed  milk,  according  to  Soxhlet,  is — 

i.  ii. 

Water 26-88  ...  2470 

Salts        ;. 2-26  ...  2- ii 

Fat 8-67  ...  6-02 

Albumen iro;  ...  977 

Sugar        .        .        .        ...     51-12  ...  57-40 

Kefyr  is  obtained  by  a  peculiar  fermentation  of  cows'  milk  set  up  by  certain  fungi. 
The  fermentation  of  mares'  milk  yields  koumiss.  Three  samples  of  koumiss  had  the 

following  composition  : — 

I  ii.  in. 

Water    .        .        .        .        .  91-87  ...  92-38  ...  92-42 

Alcohol         ,    •   .        .        .      3-29  ...  3-26  ...  3-29 

Fat 1-17  ...  1-14  ...  i -20 

Caseine          .        ..,     .        .      o-8o  ...  0-85  ...  0-79 

Albumen        ....       0-15  ...  0-32  ...  0-32 

Lacto-proteine  and  peptone  .       1-04  ...  0-59  ...  0-76 

Lactic  acid    ....      0-96  ...  1-03  ...  i'oo 

Sugar 0-39  ...  0*09 

Ash,  soluble  .        .        .        .      o'io  ...  O'i2  ...  0-12 

„     insoluble        .        .        .      0-23  ...  O"22  ...  0-23 

Butter. — This  substance  is  prepared  as  follows  : — Milk  of  good  quality  is  placed  in 
a,  rather  cool  cellar  or  other  locality  for  the  purpose  of  causing  the  cream  to  separate. 
The  cream  is  poured  into  a  clean  stoneware  or  glass  vessel  kept  for  the  purpose,  and 
left  until  by  constant  stirring  it  has  become  thick  and  sour ;  it  is  then  put  into  a 
churn,  by  the  action  of  which  the  solid  fat  globules  are  separated  from  the  thick  fluid 
in  which  the  caseine  with  a  small  quantity  of  butter  remains  suspended.  Butter,  being 
specifically  lighter  than  water,  should,  it  might  be  thought,  separate  very  readily  from 
a  liquid  which  contains  in  solution  various  substances  which  are  heavier  ;  but  the  fact 
is  that  caseine  renders  the  separation  of  butter  from  cream  difficult  even  when  the 
cream  is  sweet  and  not  thick ;  when,  on  the  other  hand,  milk  coagulates  before  the 
cream  is  separated,  the  butter  is  lost.  Two  methods  have  been  devised  for  the  purpose 
of  obtaining  all  the  butter  contained  in  milk.  Gussander,  a  Swedish  agriculturist,  has 
proposed  that  the  separation  of  cream  should  be  rendered  more  rapid,  and  always  com- 
pleted before  the  milk  becomes  sour,  while  Trommer  prevents  the  souring  of  the  milk 
by  the  addition  of  some  soda. 

The  liquid  from  which  the  butter  is  separated  is  known  as  churn-milk  or  butter- 
milk; it  contains  0-24  per  cent,  butter,  3-82  per  cent,  casein,  90-80  per  cent,  water, 
5*14  per  cent,  sugar  of  milk  and  salts.  Lactic  acid  is  present  in  the  water.  18  parts 
of  milk  yield  on  an  average  i  part  of  butter,  which  in  fresh  condition  consists  of — 

I.  II.  Ill  IV. 

Butter  fat        .        .        .  94-4        ...        93-0        ...        87-5        ...       7^5 

Caseine,  sugar  of  milk)  1>o 
Extractive  matter         ) 

Water      ....  5-3        ...          67        „.        ll'S        ...      21-2 

Owing  to  the  presence  of  water  and  caseine,  butter  after  some  time  becomes  rancid. 
It  is  salted  in  order  to  prevent  this  rancidity  as  much  as  possible,  the  salt  being 
thoroughly  mixed  with  the  butter  by  kneading.  To  i  kilo,  of  butter  30  grammes  of 


SECT,  vi.]  MILK,    BUTTER,   CHEESE. 


789 


salt  are  required.  According  to  Dr.  Wagner,  butter  in  England  is  salted  with  a 
mixture  of  4  parts  of  common  salt,  i  part  of  saltpetre,  and.i  part  of  sugar.  In  Scot- 
land, France,  and  Southern  and  Western  Germany,  butter  is  not  salted  at  all,  and  is 
therefore  only  made  and  sold  in  comparatively  small  quantities  at  a  time.  Salt  butter 
is  termed  in  Scotland  pounded  butter. 

By  melting  butter  until  the  first  turbid  liquid  has  become  clear  and  oily,  water  and 
caseine  are  eliminated,  and,  settling  to  the  bottom  of  the  vessel,  the  supernatant  fat 
may  be  put  into  another  vessel,  and  will,  after  cooling,  keep  sweet  without  salt  for  any 
length  of  time.  Butter  is  often  artificially  coloured  by  the  aid  of  either  annatto, 
turmeric,  or  infusion  of  calendula  flowers. 

Chemical  Nature  of  Butter. — Butter  consists  of  a  mixture  of  neutral  fats  (glycerides) 
which  on  being  saponified  yield  several  fatty  acids,  among  which  the  non-volatile 
are— Palmitinic  acid  (C16H3202)  and  butyroleic  acid  (CjjH^O,).  The  volatile  are- 
Butyric  acid*  (C4H802),  capronic  acid  (C6H1202),  caprylic  acid  (C8H1802),  and  caprinic 
acid  (C10H2002).  The  last  four  constitute  in  the  shape  of  glycerides  the  butyrin  or 
special  fat  of  butter,  and  impart  to  that  substance  its  peculiar  odour  and  flavour. 

Schmitt  examined  two  samples  of  cow-butter  with  the  following  results  : — 

i.  II. 

Melting-point 36*5°  ...  36*5° 

Fat 86-250  ...  86-50 

Water 9-800  ...  10-54 

Caseine 2-225  •••  J'42 

Ash o-ioo  ...  0-85 

Solid  fatty  acids,  insoluble  in  water        .  88*570  ...  89-15 

Volatile  acids,  soluble  in  water       .         .       4-452  ...  4-45 

Melting-point  of  solid  fatty  acids    .         .       39 '8°  ...  40*0° 

Composition  of  Butter  Fats  : — 

Butyrine  [CSH5(O.C4H,0)S]      ....       5  per  cent. 
Oleine  [CSH5(O.CI8RS0)3]        .         .         .         .     60        „ 
Margarine  (tristearine  and  tripalmitine)         .     35        „ 

Rancid  butter  contains  free  butyric  acid,  O'O2  gramme  of  which  per  kilo,  is  suffi- 
cient to  spoil  the  taste. 

Artificial  Butter  (Margarine  and  Oleomargarine)  is  now  manufactured  on  the  large 
scale.  At  first  the  process  consisted  in  softening  tallow  by  a  gentle  heat  and  freeing  it 
by  pressure  from  the  excess  of  stearine,  thus  producing  a  softer  mixture  of  oleine  and 
palmitine.  Such  mixtures  were  formerly  called  margarine,  under  which  name  and 
that  of  "  oleomargarine  "  artificial  butter  is  now  legally  sold,  according  to  the  law  for 
the  prevention  of  fraud.  The  want  of  the  smell  and  taste  of  genuine  butter  is  in  part 
overcome  by  a  treatment  similar  to  that  which  true  butter  undergoes  in  churning. 

This  manufacture  was  first  established  by  Mege-Mouries  at  Vincennes  in  1869. 
The  tallow,  washed  in  water  and  comminuted,  is  cautiously  melted.  The  clear,  yellow 
liquid  deposits  on  standing  all  membranes,  &c.  The  liquid  is  let  off  into  large  wooden 
cisterns  and  conveyed  into  a  room  of  the  temperature  of  20°,  where  it  cools  slowly.  In 
from  twelve  to  twenty-four  hours  sufficient  stearine  has  separated  out  in  a  granular- 
crystalline  form  ;  the  cisterns  are  removed  to  the  press-room,  where  at  an  air  tempera- 
ture of  30°  the  soft  fatty  masses,  wrapped  in  press-cloths,  are  exposed  to  a  gradually 
increasing  pressure.  The  liquid  oily  fat  drains  off;  the  press-cakes  consist  of  white 
stearine,  which  is  used  in  the  manufacture  of  soap  and  of  candles.  The  expressed  oil, 
consisting  of  a  hot  saturated  solution  of  stearine  and  palmitine  in  oleine,  is  cooled 

*  This  acid  is  formed,  not  only  by  the  saponification  of  butter,  but  is  also  met  with  in  secreted 
perspiration  and  the  juices  of  the  stomach,  and  results  from  the  fermentation  and  decay  of  sugar 
(in  weak  solutions),  starch,  fibrine,  caseine,  &c. 


790  CHEMICAL  TECHNOLOGY.  [SECT.  vi. 

down  to  20°,  and  then  worked  up  in  butter  kegs  with  sour  milk  and  a  little  of  the 
colouring  matter  of  annatto.  After  ten  to  fifteen  minutes  the  mixture  becomes  rmiform, 
and  is  emptied  out  through  an  opening  in  the  bottom  into  a  vessel,  where  it  is  stirred 
up  with  powdered  ice  in  order  to  prevent  the  fat  from  separating  out  in  a  granular  form. 
In  from  two  to  three  hours  the  mass  is  taken  out  and  divided  on  tables  with  slightly 
sloping  tops,  so  that  the  ice  may  melt  away.  Lastly,  the  butter  is  salted  by  working 
in  2  to  3  per  cent,  of  common  salt.  Or  to  200  kilos,  of  solid  fat  there  is  added  the 
stomach  of  a  sheep  or  a  swine  finely  mixed  up  and  so  much  calcium  phosphate  and 
hydrochloric  acid  as  to  form  an  artificial  gastric  juice,  and  heated  to  2o°-5o°.  In  an 
hour  there  rises  to  the  surface  a  yellow  liquid  of  a  butter-like  smell.  This  is  drawn 
off  and  mixed  with  £  per  cent,  common  salt  at  45°,  which  eliminates  a  small 
quantity  of  a  ferment.  When  clear  the  mass  is  allowed  to  crystallise  at  25°,  the 
liquid  part  is  pressed  out  and  mixed  in  the  butter  keg  with  12  to  20  per  cent,  of 
sugar,  to  which  yrJW  sodium  bicarbonate  has  been  added.  After  churning  for  half  an 
hour  it  is  allowed  to  cool  and  solidify.;  all  the  milk  is  pressed  out  of  the  mass  by 
passing  it  under  rollers,  and  it  is  moulded  for  sale.  As  a  matter  of  course,  artificial 
butter  should  be  sold  only  as  such.  When  carefully  prepared  it  is  less  liable  to  turn 
rancid  in  hot  climates  than  is  natural  butter. 

Cheese. — Cheese  is  prepared  from  caseine.  It  is  made  either  from  skimmed  or  un- 
skimmed milk.  In  the  former  case  a  lean,  dry  cheese  is  obtained  ;  in  the  latter  a  fat 
cheese,  such  as  Cheshire,  Cheddar,  American,  and  the  bulk  of  Holland  cheeses.  Lean 
cheese  is  made  in  Germany  by  pouring  the  skimmed  and  already  sour  milk  upon  a 
cloth,  through  the  pores  of  which  the  whey  passes,  while  the  caseine  remains  on  its 
surface  as  a  pasty  mass,  which  is  put  by  hand  into  the  cheese-moulds,  these  being  next 
exposed  to  air. 

Fat  cheese  is  made  of  sweet  milk  just  drawn  from  the  cows,  the  milk  being  coagu- 
lated by  rennet  after  having  been  heated  to  30°  to  40°.  The  gelatinous  mass  thus 
obtained  is  broken  up  and  pressed  by  hand,  and  the  whey  gradually  removed  by  the 
aid  of  wooden  ladles.  The  caseine,  having  been  freed  from  whey,  is  next  well  kneaded 
with  some  common  salt,  and  then  put  into  wooden  moulds  with  two  or  three  small 
holes  at  the  bottom  for  the  purpose  of  allowing  the  whey  to  flow  off  when  the  cheese 
is  pressed.  -  The  newly  made  cheese  is  usually  dipped  every  alternate  day  in  warmed 
whey,  next  wiped  dry,  put  into  the  mould  again,  and  pressed.  When  the  crust  has 
sufficiently  formed  and  the  cheese  become  so  hard  as  to  admit  of  being  handled,  some 
salt  is  rubbed  into  its  surface,  and  it  is  then  placed  in  a  cool  well-aired  room  upon  a 
shelf  to  dry  and  become,  as  it  is  termed,  ripe.  The  vesicular  appearance  of  some  kinds 
of  cheese  (the  Gruyere  cheese  exhibits  this  in  a  high  degree)  is  indirectly  due  to  the 
incomplete  removal  of  the  whey,  the  sugar  contained  becoming,  during  the  ripening, 
converted  into  alcohol  and  carbonic  acid,  which  by  its  expansion  while  escaping  pro- 
duces the  vesicular  texture.  Dutch  cheese  does  not  exhibit  this  appearance,  on  account 
of  being  strongly  pressed  and  containing  much  salt,  by  which  the  fermentation  of 
the  sugar  of  milk  in  the  cheese  is  prevented.  The  quality  of  the  cheese  depends  to 
some  extent  npon  the  temperature  of  the  room  in  which  it  ripens.  At  Allgiiu  i  cwt. 
of  Swiss  cheese  of  the  first  quality  is  produced  from  600  litres  of  milk,  while  for  the 
second  quality  720  to  750  litres  of  milk  are  taken  for  the  same  weight.  The  theory  of 
cheese  formation  is  not  well  known,  but  it  appears  that  fermentation  plays  an  impor- 
tant part  in  it.  W.  Hallier  has  proved  that  freshly  made  cheese  is  filled  with  ferment 
nuclei  (Kemhefe). 

Cheese  cannot  be  formed  without  this  ferment,  and  by  the  addition  of  suitable 
ferments  the  duration  of  the  cheese-ripening  process  and  the  quality  of  the  cheese  may 
be  to  some  extent  regulated  at  will.  By  exposure  to  air  cheese  undergoes  changes 
which  may  be  best  observed  in  skimmed-milk  cheese.  When  new  or  young  its  colour 
is  white.  By  being  kept  so  that  it  does  not  dry,  it  turns  yellow  and  often 


SECT.   VI.] 


MILK,   BUTTER,   CHEESE. 


791 


becomes  transparent,  waxy  and  then  exhibits  the  peculiar  odour  of  cheese.  When 
cheese  gets  very  old  it  becomes  a  soft  and  pasty  mass,  this  change  commencing  at  the 
outside  and  progressing  towards  the  interior.  The  waxiness  of  cheese  is  due  to  an 
evolution  of  either  ammonia  or  acid.  Mild  cheese  usually  exhibits  an  acid  reaction, 
while  strong  cheese  is  ammoniacal.  Chemically  speaking,  skirnmed-milk  cheese  is  a 
compound  of  caseine  with  ammonia  or  ammonia  bases — amylamine,  for  instance.  The 
so-called  dry  cheeses,  green  Swiss  cheese,  contain  an  infusion  of  herbs,  Melilotus,  &c., 
with  volatile  fatty  acids,  valerianic,  capric,  and  caproic  acids,  and  indifferent  substances, 
leucin,  &c.  The  composition  of  sweet  milk  cheese  (a)  and  of  sour  skim- milk  cheese  (b) 
is  exhibited  by  the  following  table  : — 

a.  b. 

Water 36^0  ...  44-0 

Caseine 29-0  ...  45-0 

Fatty  matter 30-5  ...  6-o 

Ash  .        .        .        .      '  .  '      .        ,c        4-5  ...  5-0 

ICO'O  ...  lOO'O 

The  results  of  the  researches  of  Payen  on  cheese  are  quoted  below  in  100  parts  for 
the  following  kinds: — (i)  Brie,  (2)  Camembert,  (3)  Roquefort,  (4)  Double  cream, 
(5)  Old  Neufchatel,  (6)  New  Neufchatel,  (7)  Cheshire,  (8)  Gruyere,  (9)  Ordinary 
Dutch,  (10)  Parmesan. 


I. 

i. 

2. 

3- 

4- 

5- 

Water  . 

45  '20 

5I-90 

34'50 

9'50 

34'50 

Nitrogenous  matter 

18-50 

I8-90 

26-50 

18-40 

13-00 

Nitrogen 

2-93 

3-00 

4'2I 

2-92 

3'3i 

Fatty  matters 

2570 

21-00 

30-10 

59  '90 

41-90 

Salts     . 

5  '60 

470 

5'oo 

6-50 

3-60 

Non-nitrogenous  organic  ) 
matter  and  loss            }  ' 

5'oo 

4  '50 

3-90 

570 

7-00 

ir. 

6. 

7- 

8. 

9- 

IO. 

Water          . 

T.6  60 

•JC'OO 

Nitrogenous  matter     . 

8-00 

26-00 

31'50 

29-40 

44-10 

Nitrogen     

1-27 

4-13 

5  'oo 

4-80 

7-00 

Fatty  matters      .... 

4070 

26-30 

24-00 

27-50 

r6'oo 

Salts    

0-50 

4-20 

3-00 

0-90 

570 

Non-nitrogenous  organic  \ 
matter  and  loss             }  * 

14-20 

7-60 

1-50 

6-10 

6-60 

The  varieties  mentioned  under  I.  exhibit  an  alkaline  reaction,  and  contain,  with, 
ammonia,  cryptogamic  plants,  or,  as  it  is  termed,  are  mouldy.  The  varieties  under  II., 
so-called  boiled,  strongly  pressed,  and  salted  cheese,  exhibit  an  acid  reaction,  as  also 
does  freshly  prepared  caseine.  A  portion  of  the  fat  contained  in  the  cheese  is  even 
from  the  first  decomposed  into  glycerine  and  fatty  acids. 

Emmenthaler   (a)  and  Backstein  (b)    cheese  are  composed,  according  to  Lindt's 
researches  (1868),  as  follows: — 


If 

Water    

77-4 

367 

45'2 

35-8 

Fatty  matters 
Caseine  
Salts      

2 
30-6 

28-5 
3'5 

30-5 

29-0 
3'8 

28-2 
23-2 
3'4 

37'4 
24-4 
2-4 

lOO'O 

lOO'O 

lOO'O 

lOO'O 

792 


CHEMICAL  TECHNOLOGY. 


[SECT.  vi. 


The  results  of  E.  Hornig's  recent  analyses  (1869)  of  different  kinds  of   cheese 
are : — 


6 

, 

g 

• 

2> 

Water     . 

38-66 

56-60 

51-21 

57-64 

36-72 

34-08 

59-28 

49'34 

Fatty  matters 

20-14 

17-05 

9-16 

20-31 

33'69 

28-04 

10-44 

20-63 

Caseine  . 

34-90 

1876 

33-60 

18-51 

25-67 

23-28 

24-09 

24-26 

Salts 

6-17 

678 

6-01 

3-51 

37i 

5-58 

6-17 

5'4S 

Loss 

0-13 

0-8  1 

O'O2 

0-04 

0-71 

0'02 

0'O2 

0-32 

lOO'OO 

lOO'OO 

lOO'OO 

lOO'OO 

lOO'OO 

lOO'OO 

IOO-OO 

lOO'OO 

No.  i  was  Dutch  cheese ;  2  and  3,  Ramadoux  cheese,  made  in  Bavaria ;  4,  Neuf- 
chatel  cheese  ;  5,  Gorgonzola  cheese ;  6,  Bringen  or  Liptau  cheese,  from  the  Zyps 
Comitat,  Hungary ;  7,  Schwarzenberg  cheese  ;  8,  Limburg  cheese,  made  in  the  environs 
of  Dolnain-Limburg,  in  Belgium. 

Every  rennet  contains,  according  to  Benecke,  the  hay  bacillus,  Bacillus  subtilis, 
which  is  also  present  in  ripening  cheese.  There  is  also  a  bacterium,  which  splits  off 
butyric  acid  from  the  albuminoids,  and  this,  if  it  is  formed  in  unusual  quantities,  gives 
the  cheese  a  bad  flavour. 

Loose,  fat  cheese  is  digested  in  from  four  to  ten  hours  ;  lean  cheese  is  more  difficult 
of  digestion. 

Freshly  made  caseine  mixed  with  lime  is  used  as  a  kind  of  cement.  Caseine  is  also 
used  in  calico-printing  as  a  mordant,  under  the  name  of  "  lactarine  "  ;  and  a  solution  of 
caseine  in  borax  is  used  instead  of  glue.  In  tho  seeds  of  the  leguminous  plants,  peas, 
beans,  lentils,  &c.,  a  nitrogenous  substance  is  met  with  which  is  soluble  in  water  and 
precipitable  therefrom  by  weak  acids ;  this  material  is  very  similar  to  caseine,  and, 
according  to  M.  J.  Itiers's  accounts,  in  China  peas  and  beans  are  boiled  with  water 
and  strained,  and  to  the  liquid  thus  obtained  some  solution  of  gypsum  is  added, 
whereby  the  vegetable  caseine  (legumine)  is  coagulated,  and  the  coagulum  thus 
obtained  is  treated  as  that  of  milk,  obtained  by  the  addition  of  rennet  to  the  latter. 
The  mass  so  obtained  gradually  becomes  like  cheese  in  all  respects. 

MEAT. 

What  is  commonly  known  as  meat  is  the  muscular  substance  of  the  slaughtered 
animals,  together  with  more  or  less  fat  and  bone. 

Muscular  tissue  is  histologically  composed  of  a  variety  of  complex  tissues  and  fluids, 
the  basis  of  which  is  animal  fibre  or  fibrin,  an  organised  proteine  compound.  The 
muscular  fibre  held  together  by  cellular  tissue  forms  the  muscle,  fat  being  deposited 
in  the  cellular  tissue  and  in  cells  peculiarly  constructed  for  that  purpose.  Blood- 
vessels, lymph-vessels,  nerves,  and  other  organised  tissues  are  dispersed  through  the 
muscles,  and  serve  a  variety  of  physiological  purposes.  The  muscular  tissue  is  im- 
pregnated with  a  proteine  fluid  in  which  a  variety  of  other  substances  are  met  with, 
as  kreatinin,  hypoxanthin,  kreatin,  inosite  or  muscular  sugar,  lactic  acid,  inosinic  acid, 
extractive  matter,  and  inorganic  salts — among  these  being  potassium  chloride  and 
magnesium  phosphate. 

Constituents  of  Meat. — The  average  results  of  a  great  number  of  researches  recently 
made  on  the  large  scale  concerning  the  quantity  of  water  contained  in  the  meat  of 
fattened  or  half-  or  non-fattened  animals  are  the  following  : — 


In  the  non-fattened  meat 
„      half -fattened  meat 
„      fully  fattened  meat 
fat  meat 


Lamb. 
62 

49 


Sheep. 
58 
5° 
40 
33 


Bullock. 

54 
46 


Pi?. 

56 

39 


SECT,  vi.]  MEAT.  793 

Hence  it  appears  that  with  an  increase  of  fat  the  quantity  of  water  present  in  meat 
decreases,  a  portion  being  replaced  by  fat.  Well-fed  and  fattened  meat  contains  for 
equal  weights  about  40  per  cent,  more  dry  animal  matter  than  non-fattened  meat,  while 
in  highly  fattened  meat  it  may  amount  to  60  per  cent. 

The  difference  in  nutritive  value  of  the  meat  of  well-fattened  bullocks  as  compared 
with  that  of  non-fattened  is  exhibited  in  the  following  percentage  results  obtained  by 
Breunlin : — 

Fattened.  Non-fattened. 

Water  ,*     ;  ,    .     .         .         .         38-97  ...  59-68 

Ash  ~.      , .        .        .        .          1-51  ...  1-44 

Fat 23-87  ...  8-07 

Muscle       '.'•".".        .        .         35-65  ...  30-81 


lOO'OO  ...  lOO'OO 

1000  grammes  contain — 

Muscular  Meat.          Fat.  Ash.  Water. 

Meat  from  fattened  bullocks         .         356       ...       239       ...       15       ...       390 
Meat  from  non-fattened  bullocks .         308       ...         81       ...       14       ...       597 

Difference      ....       +48       ...   +158       ...     +i       ...   -207 

Consequently,  the  meat  of  fattened  bullocks  contains  in  1000  parts  207  more  of  solid 
nutritive  matter  than  the  meat  of  the  same  in  unfattened  condition. 

The  Cooking  of  Meat. — Meat  is  either  roasted  or  boiled.  By  boiling,  meat  is  very 
essentially  altered  in  composition  according  to  the  time  it  is  boiled,  and  the  quantity 
of  water  used  to  bcil  it  in.  The  fluid  in  which  meat  has  been  boiled  contains 
soluble  alkaline  phosphates,  salts  of  lactic  and  inosinic  acids,  magnesium  phosphate, 
and  a  trace  of  calcium  phosphate.  In  order  to  be  of  the  highest  nutritive  value, 
meat  should  retain  all  its  soluble  constituents;  hence,  boiled  meat  loses  much  in 
nutritive  power.  The  albumen  contained  in  meat  is  lost  by  boiling  according  to  the 
usual  plan.  Meat  intended  to  be  boiled  should  be  immersed  in  boiling  water  to 
which  some  salt  has  been  added,  the  meat  being  put  in  while  the  water  boils  violently, 
whereby  so  great  a  heat  is  at  once  imparted  to  the  outer  portions  of  the  meat  as 
to  coagulate  the  albumen,  which  then  acts  as  an  impermeable  layer,  retaining  the  juices 
in  the  meat.  Liebig's  directions  for  making  good  broth  are  the  following : — Lean 
meat  is  minced,  mixed  with  distilled  water,  to  which  a  few  drops  of  hydrochloric  acid 
and  common  salt  are  added.  After  having  been  digested  in  the  cold  for  about  an  hour, 
the  liquid  is  strained  through  a  sieve,  and  upon  the  residue  some  distilled  water  is 
again  poured  so  as  to  extract  all  soluble  matter.  In  this  way  an  excellent  and  highly 
nutritive  cold  solution  of  extract  of  meat  is  obtained ;  this  may  be  drunk  without 
being  heated,  and  contains  albumen  in  solution,  which  is  coagulated  by  heating.  100 
parts  of  beef  yield  an  extract  containing  2*95  parts  of  albumen  and  3*05  parts  of  other 
constituents  of  meat  not  coagulable  by  heat.  Chevreul  obtained  from  500  grammes  of 
beef  containing  77  per  cent,  water,  27*25  grammes  of  extract,  in  which  were  3^25  grammes 
fat;  deducting  these,  there  remain  4-8  per  cent,  extract.  The  bulk  of  this  fluid  extract 
was  i '2 5  litre,  the  weight  1004-09  grammes,  and  it  contained — 


Water       

Organic  matter  f  Soluble  in  alcohol 
1  Insoluble  in  alcohol 

.     991-30 
0-44 
3-12 
8-67 

1004-09 

Broth  made  from  beef  contains  only  3  parts  of  meat  substance,  inclusive  of  glue 
and  fat. 


794  CHEMICAL  TECHNOLOGY.  [SECT,  vi. 

Under  the  best  conditions,  i  kilo,  of  beef  yields — 

...    (Coagulated  albumen     .        .         29-5 
Soluble  in  cold  water        .        .         60  j  ...  &         .        .   .. 

I  Albumen  in  solution     .         .         30-5 

.  (Glue-yielding  substance       .  6~o 

Insoluble  m  cold  water     .         .       ^{y.^,^     _         _         ;       ^ 

Fat 20 

Water 75° 

The  Soiling  of  Meat. — We  have  already  stated  that  the  meat  intended  to  be  boiled 
should  be  immersed  in  boiling  water  and  the  fluid  kept  boiling  for  a  few  minutes,  so 
much  cold  water  being  next  added  as  will  reduce  the  temperature  of  the  liquid  to  70° 
or  74°.  At  that  heat  the  liquid  should  be  kept  for  some  hours  to  produce  a  very 
savoury,  sweet,  succulent  piece  of  boiled  meat.  If,  however,  it  is  desired  to  make  a 
strong  broth,  lean  meat  is  first  minced,  next  well  exhausted  with  cold  water,  and  then 
slowly  heated — best  on  a  water  bath — and  just  allowed  to  come  to  the  boil  over  a  slow 
fire.  The  liquid  is  strained  from  the  solid  meat,  and  the  latter  put  into  a  clean  cloth 
and  well  pressed.  The  residue  is  fit  only  for  the  making  of  manure.  The  broth  may 
be  coloured  with  caramel  if  desired.  Broth  so  made  contains  all  the  soluble  consti- 
tuents of  meat,  and  exhibits  an  acid  reaction  owing  to  the  free  lactic  and  inosinic 
acids.  Broth  does  not  owe  its  good  properties  to  the  gelatine  it  contains,  this  sub- 
stance being  present  in  very  small  quantities,  while  the  so-called  bouillon  tablettes 
obtained  from  bones  are  altogether  unfit  for  food.  These  tablettes  should  not  be  con- 
fused with  solid-meat  extract  cakes  of  Russian  make,  which  contain,  according  to 
Reichardt  (1869)— 

Water  driven  off  at  1 00° 15*13  per  cent. 

Ash 475 

Fat o'22        ,, 

Nitrogen 10*57         ,, 

Substance  soluble  in  alcohol  at  80  per  cent.         .  38  '09        „ 

When  broth  is  boiled  for  a  long  time  it  becomes  deep-coloured  and  assumes  the 
very  agreeable  flavour  of  roast  meat.  Evaporated  upon  a  water-bath  it  yields  a  pasty, 
deep  brown-coloured  mass,  18-27  grammes  of  which  yield,  with  i  Ib.  of  hot  water  and 
the  addition  of  some  salt,  a  very  strong  and  excellent  soup.  32  Ibs.  of  bones,  with  the 
adhering  scraps  of  lean  meat,  yield  i  Ib.  of  this  extract.  Extract  of  meat,  as  gen- 
erally met  with,  is  now  made  in  South  America  by  several  firms,  at  Fray-Bentos, 
Uruguay,  Gualeguaychu  (Entre  Rios).  i  kilo,  of  this  extract  contains  all  the  soluble 
portion  of  34  kilos,  of  meat  without  bones,  or  45  kilos,  of  average  butchers'  meat. 
Australian  extract  of  beef  (the  American  extract  is  of  mutton  and  beef  mixed,  manu- 
factured by  R.  Tooth)  is  largely  imported  into  Europe.  The  chief  test  for  the  purity 
of  the  extract  of  meat  is  its  solubility  in  alcohol  at  80  per  cent.,  next  the  quantity  of 
moisture  it  contains,  and  the  absence  of  albumen  and  fat.  At  least  60  per  cent,  of  the 
extract  should  be  soluble  in  alcohol.  The  quantity  of  water  amounts  to  about  16  per 
cent.,  the  nitrogen  to  10  per  cent.,  and  the  ash  to  18  to  22  per  cent.,  consisting  essen- 
tially of  calcium  and  magnesium  phosphates,  and  chlorides  of  the  alkalies,  among  which 
potassium  chloride  predominates. 

Preservation  of  Meat. — Among  the  many  methods  employed  for  the  preservation  of 
meat,  that  by  complete  exclusion  of  air  ranks  foremost.  Appert's  plan  of  packing 
meat  in  tin  canisters,  from  which  the  air  is  completely  exhausted,  is  generally  the 
following  : — The  meat,  or  very  concentrated  soups,  game,  &c.,  is  put  into  tin  canisters, 
which  are  thoroughly  filled.  A  lid  is  then  soldered  on,  in  which  a  small  hole  is  made 
for  the  purpose  of  entirely  filling  any  interstices  with  gravy.  This  having  been  done, 
the  small  hole  is  soldered  over,  after  which  the  canisters  are  placed  in  a  cauldron  filled 


-SECT,  vi.]  .      MEAT.  795 

with  brine  and  boiled  therein  for  a  half  to  four  hours,  according  to  the  size  of  the 
canisters.  When  any  of  them  is  not  well  soldered,  there  will  issue  from  the  leakage 
smaller  or  larger  vesicles  of  air  and  vapour,  and  where  such  is  the  case  hot  solder  is 
applied  on  the  spot.  By  this  boiling  the  albuminous  substances  are  coagulated  and 
converted  into  a  less  readily  putrescible  modification.  The  oxygen  of  the  air  contained 
in  the  canisters  is  partly  converted  into  carbonic  acid,  partly  deozonised,  and  thus  ren- 
dered ineffective  for  the  production  of  putrescence.  After  having  been  submitted  to 
the  action  of  boiling  heat  for  some  time,  the  canisters  are  placed  in  a  room  heated  to  30°, 
and  left  there  in  order  to  test  whether  putrefaction  can  set  in,  manifested  by  the  bulging 
outward  of  the  top  cover,  which,  if  the  operation  has  been  thoroughly  successful,  is 
usually  somewhat  concave  in  consequence  of  a  vacuum  having  been  formed  inside  the 
tin.  After  having  been  thus  tested  for  several  days,  the  canisters  may  be  considered 
sound,  and  will  keep  for  an  indefinite  period.  Dr.  Redwood's  method  of  preserving 
meat  under  a  layer  of  paraffin,  and  Shaler's  plan  of  preserving  meat  in  dry  carbonic 
acid  gas  at  o°,  are  in  principle  the  same  as  Appert's  method. 

Preservation  of  Meat  by  Withdrawal  of  Water. — Meat  may  be  preserved  by  drying 
it  or  salting  it,  both  methods  being  based  upon  the  withdrawing  of  the  water.  Al- 
though drying  is  the  best  method  of  preserving  meat,  it  is  an  operation  attended 
with  very  great  difficulty.  The  natives  of  North  and  South  America  cure  meat  by 
cutting  it  into  thin  strips,  removing  the  fat,  and  rubbing  Indian-corn  meal  on  the 
surface.  Thus  prepared,  the  meat  is  exposed  to  the  heat  of  the  sun,  and  dries  rapidly 
forming  a  flexible,  non-putrescent  mass,  which  in  North  America  is  termed  Pemmican, 
in  South  America  Tassajo,  and  in  South  Africa  Biltongue.  100  parts  of  beef,  which 
is,  after  drying,  rolled  up  so  as  to  form  a  compact  mass,  yield  26  parts  of  tassajo. 
The  drying  of  meat  is  in  Europe  never  effected  on  a  large  scale,  partly  on  account  of 
the  low  temperature,  partly  on  account  of  the  necessity  of  cutting  the  meat  into  pieces, 
rendering  it  in  many  instances  unfit  for  culinary  purposes. 

Many  preparations  of  flour  and  meat  extract  have  been  introduced  at  different 
times  under  the  name  of  meat  biscuit,  first  made  in  1850  by  Gail  Bordon  at  Galveston, 
Texas,  U.S.,  and  greatly  improved  upon  by  C.  Thiel  at  Darmstadt.  The  latter  minces 
fresh  lean  meat,  next  exhausts  it  with  water,  and  uses  the  liquid  obtained  for  mixing 
with  the  flour  instead  of  water.  The  large  biscuit  manufacturing  firms  in  England, 
especially  Huntley  &  Palmer  at  Reading,  prepare  patent  meat  biscuits  or  wafers,  made 
with  Liebig's  extract  of  meat  and  Hassall's  flour  of  meat.  On  the  Continent,  E. 
Jacobsen  at  Berlin  prepares  a  similar  biscuit,  more  especially  with  the  view  of  pre- 
paring soup.  To  the  mixtures  of  animal  and  vegetable  matter  prepared  so  as  to  be 
suitable  for  keeping  for  a  length  of  time  belong  the  pea-sausages,  first  made  by 
Griineberg  at  Berlin,  and  largely  used  as  an  excellent  food  for  the  German  armies 
during  the  Franco-Prussian  war. 

/Salting  Meat.— This  method  of  preserving  meat,  based  upon  the  principle  of 
withdrawing  water,  has  been  used  from  time  immemorial.  The  salt,  while  penetrating 
into  the  meat  and  thereby  hardening  it,  displaces  the  water  and  aids  the  preservation 
of  the  substance.  The  freshly  slaughtered  meat  is  first  rubbed  with  coarse  salt,  and 
then  left  in  a  cask  with  salt  for  some  days.  It  is  next  pressed  and  put  into  another 
•  cask,  the  wood  of  which  has  been  previously  soaked  with  brine.  Some  salt  is  then 
added,  and  lastly  the  brine,  which  had  been  obtained  by  pressing  the  meat,  is  poured 
over  it,  and  the  lid  of  the  cask  put  on.  Frequently  some  potassium  nitrate  and  sugar 
are  added,  as  well  on  account  of  the  antiseptic  property  of  these  substances  as  for  impart- 
ing a  bright  red  colour  to  the  meat. 

Salt,  however,  not  only  withdraws  water  from  the  meat,  but  also,  as  has  been  proved 
:.by  Dr.  Liebig's  researches,  some  of  the  very  best  and  essential  portion  of  the  juices  of 


796  CHEMICAL    TECHNOLOGY.  [8EcT.  vi. 

the  meat,  including  albumen,  lactic  and  phosphoric  acids,  magnesia,  potash,  kreatin, 
and  kreatinin.  Hence  it  is  clear  that  unless  these  substances  are  in  some  way  or  other 
added  to  the  salted  meat,  its  use  as  food  for  a  lengthened  period  cannot  fail  to  become 
injurious  to  the  system,  and  it  is  surmised  that  scurvy  is  due  to  this  condition  of  salt 
meat.  Liebig  has  suggested  that  meat,  instead  of  being  treated  with  dry  salt,  should 
be  salted  with  a  strong  brine  made  up  of  common  salt,  Chili  saltpetre,  potassium 
chloride,  and  extract  of  meat.  The  salt  to  be  used  for  making  this  brine  should  be 
previously  purified  by  the  application  of  a  solution  of  sodium  phosphate,  whereby  lime 
and  magnesia  are  precipitated.  Cirio's  method  of  meat  preservation,  which  was  ex- 
hibited in  1867  at  the  Paris  Exhibition,  consists  in  placing  the  meat  in  vacuo  and  then 
forcing  brine  into  it.  By  this  process  the  nutritive  value  of  meat  is  much  impaired, 
owing  to  the  loss  of  the  juices. 

Smoking  or  Curing  Meat. — The  ratioiiale  of  this  process  and  the  preservative  action 
of  the  smoke  have  not  been  scientifically  elucidated.  In  the  first  place,  the  heat  of  the 
smoke  dries  the  meat,  while,  further,  smoke  contains  a  creosote,  which,  according  to 
the  more  recent  researches  of  Hlasiwetz,  -Gorup-Besanez,  Marasse,  and  others,  essen- 
tially consists  of  a  mixture  of  C7H802,  C8H1002,  and  C9H12Oj.  This  creosote  possesses 
the  property  of  coagulating  the  albuminous  substances  of  meat,  and  once  coagulated, 
and  thereby  rendered  insoluble,  these  substances  are  not  capable  of  decay,  or  only  so 
after  a  very  great  lapse  of  time.  Smoke,  moreover,  contains  some  pyroligneous  acid 
and  other  creosote-like  substances  (oxyphenic  and  carbolic  acids),  which  undoubtedly 
play  some  part  in  the  preservative  action. 

Vinegar  is  an  excellent  preservative  of  meat,  especially  in  hot  summer  weather. 
Abroad,  meat  is  frequently  put  into  a  clean  linen  cloth  which  is  thoroughly  soaked 
with  vinegar,  some  salt  also  being  sprinkled  on  the  cloth.  Meat  kept  for  a  few  days 
in  this  manner  is  very  tender  and  readily  digested.  It  is  very  probable  that  vinegar 
might  be  advantageously  employed  on  the  large  scale  for  the  preservation  of  meat, 
together  with  complete  exclusion  of  air.  In  order  to  prevent  the  vinegar  extracting 
the  juices  of  the  meat,  the  latter  should  be  exposed  to  the  action  of  the  vapours  of 
strong  vinegar. 

Lamy  more  recently,  and  Bracoimot,  Robert,  and  De  Dombasle  nearly  half  a  cen- 
tury ago,  proposed  to  preserve  meat  by  the  aid  of  sulphurous  acid  gas,  pieces  of  meat 
weighing  from  2  to  3  kilos,  being  exposed  to  the  action  of  this  gas  for  ten  minutes, 
while  larger  pieces,  of  10  kilos,  or  more,  are  exposed  to  the  action  of  the  gas  for  twenty  to 
twenty-five  minutes.  After  having  been  exposed  to  fresh  air  for  some  minutes  for  the 
purpose  of  getting  rid  of  the  excess  of  the  gas,  the  meat  is  coated,  with  a  brush,  with  a 
solution  of  albumen  in  a  decoction  of  marsh-mallow  root  to  which  some  molasses  have 
been  added.  Very  recently  meat  has  been  preserved  by  first  drying  it  in  a  current  of 
hot  air  and  next  coating  it  with  a  film  of  caoutchouc  or  gutta-percha,  by  immersing 
the  meat  in  a  solution  of  these  substances  in  chloroform  or  sulphide  of  carbon.  It  is 
very  generally  known  that  a  temperature  below  freezing-point  is  a  most  perfect  pro- 
tection against  decay  of  animal  matter ;  hence  ice  is  largely  used  for  the  preservation 
of  fish  in  summer  time.  Meat,  as  well  as  game  and  poultry,  are  best  preserved  in  hot 
weather  in  ice-pits.  In  no  country  in  the  world  is  so  much  use  made  of  this  mode 
of  preserving  meat  and  vegetables  as  in  Russia,  where  the  very  severe  winter  is 
turned  to  good  account  for  preserving  all  kinds  of  animal  food ;  in  fact,  oxen,  sheep, 
hogs,  deer,  and  all  kinds  of  game  and  poultry  are  brought  to  market  in  a  frozen 
condition,  and  may  be  kept  so  for  any  length  of  time  -without  impairing  the  good- 
ness or  taste  after  cooking.  At  St.  Petersburg  large  stores  of  frozen  animal  food 
and  game  brought  from  distances  of  hundreds  of  miles  are  kept  throughout  the 
winter.  At  the  Dornburg,  near  Hadamar  (Province  of  Nassau,  Prussia),  a  natural 
permanent  ice  store  exists,  wherein  perishable  food  is  kept  stored  in  large  quantity. 


SECT,  vi.]  NUTRITION.  797 

The  artificial  production  of  ice  by  means  of  Carre's  machine  is  employed  in  New 
South  Wales  for  the  freezing  of  meat,  which  is  next  packed  in  ice  ready  for  trans- 
port. 

It  must  be  added  that  the  process  of  smoking  meat  has  some  resemblance  to  a 
tanning  process,  whereby  its  digestibility  is  naturally  diminished.  On  the  other  hand, 
the  digestibility  of  meat  can  be  improved  by  rubbing  it  with  the  juice  of  Carica 
papaya.* 

NUTRITION. 

The  blood  circulating  in  the  living  animal  body  consists  of  a  clear  liquid,  containing 
substances  capable  of  forming  albumen  and  fibrine,  and  numerous  microscopic  corpuscles, 
especially  haemoglobin.  This  haemoglobin  takes  up  in  the  lungs  the  oxygen  of  the 
inhaled  air,  and  assumes  in  consequence  a  bright  red  colour.  The  bright  red  arterial 
blood  gives  off  this  oxygen  whilst  circulating  through  the  body,  and  the  haemoglobin 
of  the  blood-corpuscles  absorbs  carbon  dioxide  in  its  place,  which  the  venous  blood, 
rendered  thereby  darker,  exchanges  again  for  oxygen  in  the  lungs.  A  man  inhales 
at  every  breath  about  0*5  litre  of  air,  and  consumes  daily  750  grammes  oxygen,  giving 
off  320  grammes  watery  vapour  and  900  grammes  carbon  dioxide. 

The  food  is  moistened  in  the  mouth  by  the  saliva  secreted  by  three  glands,  which 
converts  starch  into  dextrine  and  sugar.  The  food  encounters  in  the  stomach  the 
strongly  acid  gastric  juice  containing  free  hydrochloric  acid  and  pepsine.  This  agent 
prepares  the  proteine  matters  in  the  food  for  reception  into  the  blood.  In  the  bowels 
the  digestion  is  completed  by  the  alkaline  pancreatic  secretion  and  the  gall,  when  the 
substances  suitable  for  the  formation  of  blood  are  taken  up  by  the  lymphatic  vessels 
and  conveyed  into  the  veins. 

By  the  inspiration  of  oxygen  the  parts  of  the  body  are  oxydised  and  conveyed  away 
by  the  blood,  the  carbon  dioxide  being  eliminated  in  the  lungs,  and  the  urea,  CO(NH!!),, 
formed  from  the  proteine  substances,  in  the  kidneys.  These  losses  must  be  com- 
pensated by  the  blood,  to  which  fresh  matter  must  be  conveyed  by  taking  food. 

Nutrition  has  therefore  two  distinct  tasks  to  fulfil — viz.,  (i)  the  formation  and 
preservation  of  the  body;  (2)  supply  and  utilisation  of  energy  for  the  power  of  the 
entire  body  and  its  organs — i.e.,  the  production  of  heat,  mechanical  work,  and  elec- 
tricity. The  first  duty  is  chiefly  assigned  to  the  albuminoids ;  in  the  production  of 
power  all  the  organic  matters  are  concerned  according  to  the  sum  of  the  tension  forces 
contained  in  them  and  liberated  by  the  metabolism  in  the  body.  The  non-nitrogenous 
substances,  which  only  play  a  subordinate  part  in  building  up  the  organs,  but  possess 
the  greatest  sum  of  available  tension,  are  chiefly  concerned  in  the  production  of  vis 
viva,  the  chief  representative  of  which  is  animal  heat. 

If  a  strong  man,  previously  well  fed,  entirely  abstains  from  food  for  twenty-four 
hours,  he  consumes  muscle  corresponding  to  the  expenditure  of  8-024  grammes  of  nitro- 
gen, 3*65  grammes  carbon  in  the  liquid  excretions,  180-5  grammes  carbon  in  respira- 
tion, 507  grammes  albumen,  and  198'!  grammes  of  fat.  With  a  diet  entirely  free  from 
nitrogen,  consisting  of  150  grammes  of  fat,  300  grammes  starch,  and  100  grammes 
sugar  (together  =  254-68  grammes  carbon),  there  were  eliminated  in  the  liquid  excreta 
8' 1 6  grammes  nitrogen  and  3*6 1  grammes  carbon  ;  in  the  solid  excretions  18*79  grammes 
and  in  respiration  200-50  grammes  carbon,  so  that  the  body  had  lost  51*8  grammes 
albumen,  but  gained  81-5  grammes  fat.  On  a  purely  animal  diet,  nitrogen  is  retained  in 
the  body,  and  the  amount  of  fat  is  reduced.  A  perfect  equilibrium  between  the  intake 
and  the  outlay  in  the  body  of  a  vigorous  man  (during  muscular  rest)  is  obtained 
by- 

*  This  process  is  applicable  only  if  the  meat  is  to  be  immediately  consumed.— [EDITOR.] 


793  CHEMICAL  TECHNOLOGY. 

Albumen  (with  15-5  grammes  N.)    ....  100  grammes 

Fat  ..........  100        ,, 

Starch  and  sugar 240        ,, 

Water,  drunk,  and  contained  in  the  solids       .        .  2535        ,, 

Salts 25        ,, 


[SECT, 


These  quantities  correspond  to  250  grammes  meat,  400  grammes  bread,  70  grammes  sugarr 
100  grammes  fat,  10  grammes  salt,  and  2100  grammes  water.  A  man  on  a  mixed  diet 
uses,  therefore,  49  grammes  albumen  and  43  grammes  fat  more  than  a  similarly  hungry 
man  not  doing  work  which  promotes  digestion.  With  severe  muscular  work  a  man 
needs  very  little  more  albumen,  but  considerably  larger  quantities  of  fat  and  carbo- 
hydrates, than  when  at  rest.  This  extra  consumption  of  albumen  and  fat  for  the 
work  of  digestion  must  be  considered  in  deciding  on  the  value  of  nutriment.  Th& 
greater  tension-power  a  certain  weight  of  nourishment  introduces  which  becomes  free- 
and  available  in  the  organism  the  higher  is  its  food  value. 

If  we  estimate,  in  animal  foods,  100  grammes  albumen  at  65  pfennige,*  100  grammes- 
fat  at  20  pfennige,  and  in  vegetable  foods  100  grammes  albumen  at  15,  fat  at  4-5,  and 
non-nitrogenous  extract  at  2*5  pfennige,  we  have  the  following  values  : — 


Chemical  Composition  in  per  cent. 

T.-1          . 

i  Kilo,  has 

e  « 

3 

~ 

Vegetable  Foods. 

tS 

"o 

e 

.. 

*"•§ 

s 

£ 

£ 

a>"3'" 

o 

i 

Album 

n 

H 

K 

S 

^O 

* 

S      • 

"S  g 

13-38 

Q'o6 

I  "42 

-..-, 

0-6"? 

0-08 

-J-j'2 

"6 

„      coarse         .... 

15-02 

9-18 

1-63 

69-86 

0-62 

1-69 

37  '9 

24 

14-41 

6  "94 

O'tJI 

77'6i 

0-08 

o'4t; 

7O'O 

80 

4"?  '26 

6*12 

O'QT 

46*6'* 

O'i7 

i  '80 

21  -3 

20 

Fine  wheat  bread       .... 

26-39 

8-62 

0*60 

62-98 

0-41 

i-oo 

28-9 

48 

I4'5O 

2VOO 

2"OO 

53-50 

4  '"JO 

2'tJO 

48-7 

•JQ 

QI'22 

O*7Q 

0*26 

6'OQ 

0-86 

O'7Q 

2-8 

•j-i 

Cauliflower         .        .        • 

2-89 

0-16 

3-02 

0-80 

0-79 

5-2 

320 

7577 

1-79 

0-16 

20-56 

075 

0-97 

7-5 

6 

Animal  Foods. 

Chemical  Composition  in  per  cents. 

i  Kilo,  has 

C 

"3 

'O  .  —  s 

1.S 
1-tt 

<"" 

"8 

fi 

e  > 

f|| 
•;:  t<  'a 

!«S 

o  S 
Ko 

05 

j3 

*i& 

ill 

ill 

£?5 

a  <=• 
fc 

Market  Price, 
Pfennige. 

73-48 
65-11 
71-66 
71-41 
71-17 
4871 
73-82 

73-13 
47-12 
51-77 
42-79 
49-93 
72-46 
88-00 

I2-OO 

36-00 

19-17 
17-94 
18-14 
14-65 
17-94 
15-98 
23-54 

22*19 

18-97 

22-30 
11-69 

11-81 

11-36 

3  "20 

0-50 
23-00 

5-86 

15-55 
7-18 

12-64 

8-38 
34-62 
1-19 
1-77 
16-67 

2'2I 
39-6I 
II-48 
I3-40 
4'OO 

86-00 
37-00 

O'll 
0-62 

0-32 
0-47 

0-47 
1-39 

2-25 
25-09 

1-73 
4"OO 
0-50 

1-38 
0-78 
3-02 
0-98 
2-04 
0*69 
1-07 
I-52 
I7-24 
23-72 

3-66 
1-69 
1-05 
i  -80 

I  -00 

4-00 

I36-3 
I43-9 
I32-3 
I20-5 

I33-4 
I72-I 

I43-4 
147-8 
156-6 

I49-3 
I55-2 
76-4 

1  06  '6 
33-6 
176-9 

223-5 

1  60 
144 
86 

IOO 

5o 
300 

221 
6OO 
105 

465 
360 
60 
2OO-24O 

15 

200-240 
I  50-200 

„      2nd  quality        .... 
„     3rd  quality        .... 

Hain  (pig)   .                 .... 

Fieldfares   
Herring        ...... 

Frankfurt  sausage       .... 

Milk    
Butter          

Cheese         

loo  pfennige  = 


SECT,  vi.]  NUTRITION.  799 

According  to  this  table  the  fattest  kinds  of  meat  are  most  to  be  recommended ; 
game  and  poultry  are  very  costly ;  fish  cheap  in  proportion  to  nutritive  value. 
Sausage  and  smoked  meats  are  dearer  than  fresh  meat.  Milk  and  cheese  are 
cheap. 

Legumens  are  cheap  in  proportion  to  nutritive  value.  Wheat  and  rye  are  cheaper 
than  rice ;  vegetables  (cauliflower,  carrots,  &c.)  the  most  costly.  Meat,  eggs,  and  milk 
are  most  completely  utilised  ;  vegetables  much  less  thoroughly,  as  from  20  to  40  per  cent, 
are  excreted  undigested.  A  powerful  body  can  scarcely  be  built  up  and  maintained 
on  a  purely  vegetable  diet.  The  small  capacity  for  work  of  persons  so  fed  is  known. 


SECTION    VII. 
CHEMICAL   TECHNOLOGY  OF  FIBRES. 


WOOL. 

Origin  and  Properties  of  Wool. — Wool  is  distinguished  from  hair  chiefly  by  the 
three  following  properties  :  it  is  finer ;  it  is  not  straight,  but  curled ;  while  it  generally 
contains  less  pigment,  and  hence  is  white  in  colour.  The  quality  of  wool  improves 
with  the  increase  of  these  three  characteristics.  Wool,  like  hair,  exhibits  an  organised 
structure,  consisting  histologically  of  an  epithelium,  of  a  rind,  and  of  a  pith  or 
marrow.  The  epithelium  of  wool  consists  of  small  thin  plates  which  overlap  each 
other  like  the  tiles  on  a  roof ;  in  this  manner  the  cuticular  plates  give  to  the  sur- 
face a  squamose  appearance,  which  may  be  coarsely  represented  as  the  appearance 
exhibited  by  a  fir-cone.  Fig.  542  exhibits  a  piece  of  wool  of  an  ordinary 
sheep;  while  Fig.  541,  magnified  to  the  same  number  of  diameters,  exhibits  a 
Fig.  541.  Fig.  542. 

Fig.  543- 


piece  of  the  very  finest  Saxony  wool,  thus  showing  the  great  difference  of  fine- 
ness of  these  two  sorts  of  wool.  The  grooves  on  the  surface  of  the  wool  are 
the  cause  of  its  rawness  to  the  touch,  and  from  the  existence  of  these  grooves 
wool  admits  of  being  felted.  When  the  fibres  which  exhibit  this  texture  are 
pressed  together  with  a  kind  of  kneading  motion,  and  at  the  same  time  softened 
by  the  action  of  steam,  they  join  to  each  other  in  the  direction  of  the  scales  on 


SECT.    VII.] 


WOOL. 


801 


their  surface  and,  becoming  entangled,  form  a  firm,  dense  texture,  which  is  termed 
felt. 

Coarser  wools  have  also  longitudinal  grooves,  as  shown  in  Fig.  543. 

The  varieties  of  wool  obtained  from  animals  other  than  sheep  are  : — 

(a)  Cashmere  wool ;  the  fine  downy   hair  of  the  Cashmere  goats  inhabiting  the 
eastern  slopes  of  the  Himalaya,  from  14,000  to  18,000  feet  above  sea  level.    The  colour  is 
white-grey  or  brown.     In  the  state  in  which  it  is  sent  to  Europe  it  is  largely  mixed 
with  coarse  hair,  so  that,  after  sorting  and  cleansing,  100  kilos,  of  the  raw  material  yield 
only  20  kilos,  of  fine  hair. 

(b)  Vienna   wool ;    the  very   slightly   curly    hair   of    the    llama   or   vicuna   goat 
(Auchenia  vicuna),  a  native  of  the  high  mountains  of  Peru,  Chili,  and  Mexico.     This 
kind  of  wool,  or  rather  woolly  hair,  was  formerly  more  used  than  now  for  weaving 
fine  tissues.     Sometimes  a  mixture  of  ordinary  wool  and  the  finest  hair  of  hares  and 
rabbits  is  substituted  for  this  wool.      What  is  now  termed  viguna  or  vicuna  wool  in 
the  trade  is  a  tissue  made  of  a  mixture  of  wool  and  cotton. 


Fig-  544- 


Fig-  545- 


J 


(c)  Alpaca  wool,  or  pacos  hair ;  the  long,  sleek,  white,  black,  or  brown  hair  of  tht, 
alpagua  or  alpaco  (pako),  a  kind  of  goat  which  dwells  in  Peru.     This  kind  of  woolly 
hair  has  great  similarity  with  the  vicuna  wool,  but  is  not  quite  so  fine.* 

(d)  Mohair,  or  so-called  camel's  wool ;  the  long,  slightly  curly,  silky  hair  of   the 
angora  goat  (Capra  angorensis),  a  native  of  Asia  Minor.     This  substance  is  spun  and 
woven  into  non-fulled  tissues  (camlet  or  plush),  and  is  also  mixed  up  with  the  half-silk 
tissues  of  which  it  forms  the  woof  or  weft. 

Chemical  Composition  of  Wool.— Purified  and  cleansed  wool  consists  chiefly  of  an 
albumenoid  sulphur-containing  substance  termed  keratin  (horny  matter),  but,  as  met 
with  on  the  animals,  wool  contains  much  dirt,  dust,  and  suint.  The  labours  of  Faist, 
Reich,  Ulbricht,  Hartmann,  Marcker,  and  E.  Schulze  have  greatly  increased  our 
knowledge  of  this  substance. 

The  following  results  are  those  obtained  by  Faist  when  analysing  various  kinds  of 

merino  wool : — 

*  The  microscopical  texture  and  properties  of  this  kind  of  hair  have  been  investigated  and  are 
described  in  Wiesner's  work,  Einleitung  in  die  technische  Mikroslcopie.  Vienna,  1867,  pp.  172 
?£  seq. 


302 


CHEMICAL  TECHNOLOGY. 


[SECT.  vn. 


i. 

2. 

a. 

b. 

c. 

d. 

e. 

/. 

Mineral  matter 

6-3 

16-8 

0-94 

i'3 

I'O 

I  '2 

Suint  and  fatty  matter 

44  '3 

447 

21'00 

40-0 

27*0 

16-6 

Pure  wool 

38-0 

28-5 

72-00 

56-0 

64-8 

777 

Moisture   .         .         .        . 

11-4 

7-0 

6-06 

27 

7-2 

3'5 

lOO'O 

lOO'O 

lOO'OO 

lOO'O 

lOO'O 

lOO'O 

Percentage  of  pure  | 
air-dry  wool         ) 

49  "4 

35-5 

78-06 

58-7 

72  x> 

82-2 
1 

i .  Raw  wool,  air-dried. — (a)  Hohenheim  wool,  with  a  small  quantity  of  readily  soluble 
suint.  (6)  Hohenheim  wool  (the  name  of  a  large  agricultural  establishment  and  agrono- 
mical school  near  Stuttgart,  Wurtemburg),  containing  a  large  quantity  of  glutinous 
suint.  2.  Washed  wool,  air-dry.* — (c)  Hohenheim  wool.  (d)  Same  variety,  with 
difficultly  soluble  suint.  (e)  Hungarian  wool,  very  soft.  (/)  Wiirtemburg  wool, 
less  soft. 

While  making  researches  on  wool,  Eisner  of  Gronow  estimated  the  loss  which  wool 
experiences  when  treated  with  sulphide  of  carbon  for  the  elimination  of  the  suint. 
The  results  were — 

Washed  merino  wool  *    .        .        .        .         .         15  to  70  per  cent. 
Unwashed  wool  (laine  en  suint,  raw  wool)        .         50  to  80        „ 
Long  carded  wool 18        ,, 

Suint  is  a  mixture  of  secreted  and  accidental  substances,  dust,  &c.  When  raw  wool 
is  macerated  for  some  time  in  warm  water,  there  results  a  turbid  liquid  which  contains 

suspended  as  well  as  dissolved  matters. 

Fig.  546.  The  dry  substance  of  the  aqueous  extract 

of  suint   consists,  according  to  Marcker 
and  Schulze  (1869),  of — 

T.  2.  3.  4. 

Organic  matter    .     58-92     6i'86     59-12     60*47 
Mineral  matter   .     41-08    38-14    40-88    39-53 

i  and  2  relate  to  wool  of  mountain  sheep. 
3  and  4  to  full-bred  Eambouillet  sheep. 

The  soluble  portion  contains  the  potash 
salt  of  a  fatty  acid  (potassium  suintate}. 
The  fatty  acids  contained  in  suint  are, 
according  to  Reich  and  Ulbricht,  mixtures 
of  oleic  and  stearic  acids,  probably  also 
palmitic  acid  and  a  small  quantity  of 
valerianic  acid,  with  potash  in  such  quan- 
tity, that  more  recently  this  material 
has  been  employed  for  obtaining  there- 
from potassium  carbonate  and  potassium 
chloride.  100  kilos,  of  raw  wool  may 
yield  from  7  to  9  kilos,  of  potash  (see 
p.  283).  • 

Artificial  Wool  is  formed  by  tearing  up  woollen  rags,  and  is  used  in  very  con- 
siderable quantities  both  along  with,  and  instead  of,  fresh  wool.  The  trade  dis- 

*  Washed  on  the  sheep  while  alive,  an  operation  performed  by  the  farmers,  and  to  be  distin- 
guished from  the  washing  wool  undergoes  during  manufacture. 


W  =  Wool. 
B    =  Cotton. 
L    =  Linen. 
S    =  Silk. 
J    =  Juie. 


SECT,  vii.]  SILK.  803 

tinguishes  shoddy,  the  artificial  wools  obtained  by  tearing  up  into  a  fibrous  state 
all  sorts  of  fabrics  known  as  "  softs "—  i.e.,  blankets,  flannels,  old  stockings,  &c. 
Mungo  is  obtained  by  grinding  up  the  "  hard "  rags  from  milled  cloths.  Fig.  546 
shows  the  mixed  fibres  obtained  by  tearing  up  cloth.* 

SILK. 

Silk  is  at  once  distinguished  from  cotton,  flax,  hemp,  and  wool  by  being 
naturally  produced  as  a  very  long  and  continuous  thread,  whereby  the  operation  of 
spinning  is  dispensed  with ;  but  in  its  stead  the  operation  known  as  silk-throwing  is 
required,  by  which  several  of  the  natural  fibres  of  the  silk  are  twisted  into  one  in  order 
to  obtain  a  stouter  yarn. 

Silk  is  the  produce  of  the  silkworm  (Bombyx  mori),  an  insect  which  undergoes  four 
metamorphoses.  The  worm  is  produced,  in  the  spring,  from  the  egg,  or  ovule.  It 
•casts  its  skin  from  three  to  four  times,  and  finally  spins  a  thread,  produced,  or  rather 
secreted,  by  two  glands  placed  near  the  head,  from  small  apertures,  in  which  is  gluti- 
nous fluid,  which  immediately  coagulates  under  contact  with  air.  Thus,  what  is 
termed  a  cocoon  is  formed,  which  serves  as  a  shelter  for  the  pupa  against  injury  and 
cold.  The  thread  is  double,  but  is  united  in  one  by  a  peculiar  kind  of  glue  termed 
sericin,  which  is  laid  as  a  kind  of  varnish  over  the  whole  surface  of  the  thread,  of 
the  weight  of  which  it  forms  about  35  per  cent.  After  a  period  of  from  fifteen  to  twenty- 
one  days,  the  pupa  is  metamorphosed  into  a  butterfly,  which,  in  order  to  leave  its 
prison,  softens  a  portion  of  the  cocoon  with  a  juice  which  it  secretes,  and  then  per- 
forates the  softened  part.  For  the  purpose,  however,  of  producing  silk,  the  pupa  is 
not  allowed  to  develop  so  far,  but  is  killed  (excepting  in  a  number  of  cocoons  intended 
for  the  full  development  of  the  moths,  so  that  they  may  produce  eggs),  and  the 
thread  of  the  cocoon  is  carefully  wound  on  a  reel. 

Sericiculture. — Varieties  of  Silkworms. — The  Bombyx  mori  is  the  main  supplier  of 
silk.  Its  food  is  the  leaves  of  the  white  mulberry  tree,  Morus  alba.  There  are, 
however,  other  silk-producing  insects,  among  which  the  following  are  to  be 
noticed : — 

(a)  Bombyx  cynthia,  largely  cultivated  by  the  natives  of  the  north-east  portion  of  the 
interior  of  Bengal  and  also  by  the  Japanese.  The  former  call  this  worm  A  rrindy-arria, 
the  latter  Yama-ma'i.  This  worm  feeds  on  rice  leaves,  and  on  Ricinus  communis.  The  silk 
obtained  from  this  insect,  although  less  brilliant  than  that  which  the  ordinary  silkworm 
yields,  is  very  useful,  as  being  durable  and  strong.  This  worm  will  feed  on  other  leaves, 
such  as  that  of  the  weavers'  thistle,  Dipsacus  fullonum,  wild  chicory,  Chicoriv/m  intibiis, 
and  the  leaves  of  the  Ailanthus  glandulosa.  The  results  of  acclimatising  this  insect  in 
France  and  Germany  have  been  satisfactory. 

(&)  Bombyx  pernyi  is  a  native  of  Mongolia  and  China ;  it  feeds  on  oak-leaves. 
Some  years  ago  these  worms  were  introduced  into  France,  and  have  been  fed  and 
reared  successfully  upon  European  oak-leaves. 

(c)  Bombyx  mylitta,  or  Tussa  worm,  is  a  native  of  the  colder  parts  of  Hindostan 
and  of  the  slopes  of  the  Himalaya.  Its  silk  is  an  important  article  of  commerce  in 
Bengal.  This  insect  feeds  on  oak  and  other  leaves,  casts  its  skin  five  times,  and  yields 
large  cocoons.  The  fibre  of  this  kind  of  silk  is  from  six  to  seven  times  stouter  than 
the  silk  of  the  ordinary  worm,  but  unfortunately  the  Tussa  worm  only  lives  in  its 
free  natural  state,  and  when  captive  does  not  produce  silk.  The  following  silk- 
producing  varieties  belong  to  North  America: — (d)  Bombyx  polyphemus  ;  on  oak  and 

*  For  full  information  on  wool  from  an  industrial  point  of  view,  the  reader  may  compare  The, 
Structure  of  the  Wool  Fibre  in  its  delation  to  tlie  Use  of  Wool  for  Technical  Purposes,  by  Dr.  F.  H. 
Bowman,  F.L.S.,  &c.  Manchester  :  Palmer  and  Howe. — [EDITOR.] 


804  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

poplar  trees,  (e)  B.  cecropia  ;  on  elm,  whitethorn,  and  wild  mulberry  trees.  (/)  S. 
platensis  ;  on  a  kind  of  mimosa,  Mimosa  platensis.  (g)  B.  leuca,  which  deserves  f  urther 
attention. 

We  quote  the  following  account  of  the  culture  and  rearing  of  silkworms  : — (i)  The 
mulberry  tree.  The  leaves  of  the  variety  known  as  the  white  mulberry  tree,  from 
the  fact  that  its  fruit  is  yellow  or  light  red  in  colour,  is  the  most  suitable  food  for  this 
insect,  but  its  cultivation  belongs  to  horticultural  pursuits,  and  we  cannot  enter  upon 
the  subject  here.  (2)  The  production  of  the  eggs  or  ova  of  the  silkworm  is  effected  in 
the  following  manner : — The  largest  and  finest  cocoons,  and  such  as  have  a  fine 
thread,  are  selected  and  preserved ;  usually  the  cocoon  of  the  female  insect  is  more 
oval  than  that  of  the  male,  which  is  more  pointed  at  the  ends  and  is  somewhat 
depressed  in  the  centre.  Although  these  characteristics  do  not  apply  in  all  cases, 
sericiculturists  become  sufficiently  adepts  in  this  matter  to  be  able  to  select  a 
sufficient  number  of  cocoons  of  each  sex.  100  to  120  pairs  of  well-formed  cocoons 
yield  30  grammes  of  eggs,  about  50,000  in  number,  from  which,  however,  only 
70  to  75  per  cent,  of  worms  are  obtained.  The  cocoons  selected  for  breeding 
purposes  are  allowed  to  remain  on  a  table  covered  with  a  white  cotton  cloth. 
After  some  twelve  days  the  moths  make  their  appearance,  and,  having  paired, 
the  females,  after  a  lapse  of  some  forty  hours,  lay  from  300  to  400  eggs.  (3)  The 
eggs  are  properly  protected  from  cold  in  winter  and  remain  in  the  buildings 
called  magnaneries,  being  placed  in  a  uniform  layer  on  a  cotton  cloth  stretched  on 
a  wooden  frame.  The  eggs  are  covered  with  sheets  of  white  paper,  perforated  with 
small  holes.  Upon  the  sheets  of  paper  mulberry  leaves,  at  first  cut  up  so  as  to  form 
a  kind  of  chaff,  are  placed.  In  France  a  contrivance  known  as  a  couveuse, — that  is 
to  say,  an  oven,  in  which  a  suitable  temperature  is  kept  up — is  now  generally  used 
for  the  purpose  of  breeding  the  worms,  which  are  best  hatched  from  the  eggs  at  a 
temperature  of  30°,  provided  moisture  is  also  present.  The  young  brood,  on  leaving 
the  eggs,  creep  through  the  holes  in  the  paper,  and  seeking  daylight  (there  is  always 
free  access  of  light  in  magnaneries)  begin  at  once  to  feed  on  the  mulberry  leaves. 
(4)  The  rearing  of  the  worms  requires  care  and  attention.  They  are  best  placed 
on  paper  laid  on  wooden  frames.  The  worms  grow  rapidly,  and  are  very  voracious. 
They  cast  their  skins  four  times,  and  after  from  thirty  to  thirty- two  days  begin  to  spin  the 
cocoons.  (5)  When  the  period  of  spinning  approaches,  the  worms  are  placed  in  small, 
somewhat  conical  wicker-work  baskets,  in  which  they  are  comfortably  located.  The 
first  thread  spun,  or  rather  an  entangled  flocky  mass,  is  afterwards  separately  collected 
and  kept  as  floss  silk.  The  insect  discharges,  before  beginning  to  spin  further,  first 
a  solid  substance,  white  or  green  in  colour,  and  consisting,  according  to  Peligot,  chiefly 
of  uric  acid  ;  next  a  clear,  watery,  very  alkaline  liquid,  which  contains  1-5  per  cent,  of 
potassium  carbonate,  this  curious  discharge  amounting  to  from  15  to  20  per  cent,  of  the 
weight  of  the  worm.  The  formation  of  the  cocoon  is  finished  in  about  five  days,  but 
the  cocoons  are  not  collected  for  the  purpose  of  reeling  the  silk  until  after  seven  or 
eight  days,  so  as  to  make  sure  that  all  the  worms  have  spun. 

As  far  as  the  chemical  composition  of  silk  is  concerned,  we  have  to  distinguish 
between  the  fibre  and  its  envelope.  The  fibre  consists,  for  about  half  its  weight,  of 
fibroin,  a  substance  which,  according  to  Stadeler's  researches,  is  nearly  related  to 
horny  matter  and  mucus,  and  is  identical  with  these  as  regards  chemical  compo- 
sition. The  formula  of  silk  fibroin  is  C15H23N506.  The  gum-like  envelope  of  the 
silk  fibre,  which  has  been  termed  by  Cramer  and  Stadeler  silk  glue  or  sericin,  is 
partly  soluble  in  water  and  readily  so  in  soap-suds  and  other  alkaline  fluids.  The 
formula  of  sericin  is  Ci5H25N"508.  P.  Bolley's  researches  have  proved  that  in  the  silk- 
producing  and  secreting  glands  of  the  worm  only  glutinous,  semi-liquid  fibroin 
occurs,  which,  on  coming  into  contact  with  air,  is  acted  upon  by  the  oxygen,  and 


SECT,  vii.]  SILK.  805 

then  converted  into  seriein.  Haw  silk  leaves,  on  ignition,  a  small  quantity  of  ash  ; 
Guinon  found  in  Piedmontese  raw  silk,  dried  at  100°,  0-64  per  cent,  of  ash,  consisting 
of  0-526  lime  and  o'ii8  alumina  and  oxide  of  iron.  Dr.  J.  G.  Mulder  found  in  100 
parts  of  raw  silk — 

Yellow  Silk  from  White  Silk  from  the 
Naples.                  Levant  (Almasin  Silk). 

Fibroin 53-40  ..  54-o 

Glue-yielding  matter     .        .        .        .        2070  ...  19-1 

Wax,  resin,  and  fatty  matter         .        .           1*50  ...  1-4 

Colouring  matter          .        .        .        .          0-05  ...  — 

Albumen       .......        24-40  ...  25-5 

(6)  Killing  the  Pupa  in  the  Cocoon. — The  pupa  remains  in  the  cocoon  for  from  fif- 
teen to  twenty  days,  and  is  then  metamorphosed  into  a  butterfly,  which  will  perforate 
the  cocoon,  and  thus  obtain  an  exit.  It  is  clear,  however,  that  the  cocoon  not  intended 
for  breeding  purposes  should  not  be  kept  so  long,  because  by  the  perforation  of  the  cocoon 
the  silk  is  spoiled,  or  at  least  greatly  deteriorated.  Therefore  the  pupae  in  the  cocoons 
are  either  killed  by  the  application  of  oven-heat  or  of  steam. 

Manipulation  of  the  Silk. — Six  different  operations  are  required  to  render  raw  silk  fit 
for  use  as  an  article  of  commerce  and  suitable  for  weaving,  &c.  These  operations  are  : — 

1 i)  The  Sorting  of  the  Cocoons,  an  operation  which  requires  great  care  and  greater  expe- 
rience, its  aim  being — (a)  the  separation  of  yellow  from  white  cocoons ;  (/3)  the  elimina- 
tion of  all  damaged  cocoons  as  only  fit  for  yielding  floret  silk ;  the  damage  may  arise  in 
various  ways,  as,  for  instance,  by  mouldiness,  injury  by  other  insects,  and,  lastly,  foul- 
ing of  the  pupa,   as  well  as  perforation  by  the  moth ;  (7)  selection  of  the  cocoons 
according  to  varying  fineness  of  thread  and  uniformity  of  the  silk. 

(2)  Winding  the  Silk  on  the  Reel  is  the  first  operation  with  the  cocoon.    By  this  the 
threads  of  silk  which  the  insect  has  wound  up  into  a  kind  of  ball  are  unwound  and 
brought  into  the  shape  of  a  skein  or  strand. 

As  the  single  fibre  of  silk  is  far  too  thin  to  be  manipulated,  the  operator  usually 
takes  from  3  to  10  or  even  20,  making  them  unite  by  the  operation  of  reeling.  This 
is  not  by  any  means  so  readily  performed  as  might  be  imagined,  because  it  is  difficult 
to  find  the  end  of  the  thread,  whilst  the  surface  of  the  cocoon  is  varnished  with  a 
gum-like  mass,  which  glues  the  fibres  together.  Partly  by  the  aid  of  hot  water  and 
partly  by  dexterity  these  difficulties  are  overcome,  and  by  good  management  a  thread 
of  from  250  to  900  metres  length  may  be  obtained  from  each  cocoon,  each  yielding 
from  0-16  to  0*20,  at  the  very  utmost  0-25  gramme,  of  raw  silk,  i  kilo,  of  raw  silk 
requires  from  10  to  12  kilos,  of  cocoons.  The  silk  thus  obtained  is  termed  raw  silk, 
which  should  be  quite  uniform  as  regards  thickness  and  strength  of  fibre.  That  por- 
tion— the  interior  and  a  portion  of  the  outer  layer  of  the  cocoon — which  does  not 
admit  of  being  reeled  off  is  employed  for  making  floret  silk,  by  operations  similar  to 
those  in  use  for  wool  and  cotton — viz.,  cleansing,  disentangling,  combing,  carding,  and 
spinning,  to  produce  a  silk  yarn. 

(3)  The  Throwing  of  Silk. — As  the  thread  obtained  by  reeling  is  too  fine  for  use, 
either  for  weaving,  knitting,  sewing,  &c.,  it  is  usual  to  unite  several  threads  of  silk  by 
means  very  similar  to  those  used  in  rope- making,  an  operation  termed  throwing,  known 
as  twisting  when  the  thread  of  raw  silk  is  simply  rotated  on  its  axis  so  as  to  make  it 
stronger.     The  following  are  the  chief  varieties  of  thrown  silk : — (a)  Organzine,  used  as 
chain  for  woven  silk  fabrics,  is  prepared  from  the  best  raw  silk.   The  threads  of  from  3  to 
8  cocoons  are  united,  being  first  strongly  twisted  and  next  thrown,  after  which  two  of 
such  threads  are  twisted  together,     (b)  Trame  used  for  woof  or  weft,  and  for  silk  cord, 
is  made  from  inferior  cocoons.     Single-threaded  trame  consists  of  one  single  twisted 
raw  silk  thread  made  up  of  the  united  threads  of  from  3  to  1 2  cocoons.     The  double- 
threaded  trame  consists  of  two  threads  twisted  to  the  left,  but  less  strongly  than  in 


806  CHEMICAL   TECHNOLOGY.  [SECT.  vii. 

organzine.  There  are  also  three-threaded  trame,  &c.  Trame  is  softer  and  smoother 
than  organzine,  and  therefore  fills  better  than  round  threads  in  weaving,  (c)  Marabou 
silk  is  stiffly  thrown  and  similar  to  whipcord ;  it  is  made  from  three  threads  of  the 
whitest  raw  silk  and  thrown  in  the  trame  fashion  ;  is  dyed  without  being  previously 
scoured  (boiling  the  gum  out  in  this  instance),  and  is  again  thrown  after  dyeing. 
(d)  Foil  silk  is  a  simple  raw  silk  thread,  twisted,  and  chiefly  used  as  a  basis  for  gold  and 
silver  wire,  such  as  is  worn  on  military  uniforms.  Sewing  silk  is  obtained  from  some 
3  to  22  cocoon  threads  being  twisted  together.  There  are  several  other  varieties  of 
silk  thread  used  for  crochet,  knitting,  &c. 

(4)  Conditioning  or  Testing  of  Silk. — The  fineness  of  raw  as  well  as  of  thrown  silk 
is  expressed  by  stating  how  many  yards  or  metres  length  of  the  fibre  are  contained  in 
a  certain  weight.     The  unit  abroad  is  400  ells  or  475  metres.     When  the  expression 
is  used,  that  such  silk  is  at  10  grains,  it  is  understood  that  475  metres  length  of  that 
particular  silk  weighs  10  grains;  a  silk  at  20  grains  has  the  same  length  but  double  the 
weight,  and  consequently  that  silk  is  only. half  <is  fine  as  the  former. 

Raw,  as  well  as  thrown  silk,  contains  a  large  quantity  of  hygroscopic  water,  the 
quantity  of  which  cannot  be  judged  by  the  external  appearance  of  the  material.  The 
silk  usually  met  with  in  commerce  contains  from  10  to  18  per  cent,  of  hygroscopic  water ; 
and  silk  may  occasionally  contain  even  30  per  cent,  without  appearing  to  be  moist. 
As  silk  is  a  very  expensive  material  and  often  sold  by  weight,  it  is  clear  that  this 
property  of  taking  up  water  is  too  important  to  be  left  unnoticed  ;  and  for  that  reason 
silk  is  conditioned  as  it  is  called,  that  is,  the  quantity  of  water  it  contains  is  duly 
ascertained. 

(5)  Scouring  or  Boiling  the  Gum  out  of  Silk. — Excepting  a  few  instances,  such  a& 
for  example,  in  the  weaving  of  fine  silken  sieve  cloths,  and  for  crape  and  gauze  fabrics, 
raw  silk  has  to  be  deprived  of  its  envelope,  the  gummy  matter  already  mentioned,, 
in  order  to  give  softness,  suppleness,  gloss,  and  especially  also  to  render  the  silk  fit  for 
being  dyed. 

The  operation  of  scouring  is  comprised  in  the  following  manipulations : — 

(1)  Removing  the  gum. 

(2)  Boiling. 

(3)  Colouring. 

The  taking  out  of  the  gum  is  performed  in  the  following  manner : — Olive  oil  soap 
is  first  dissolved  in  hot  water  and  into  this  solution  at  85°  the  skeins  of  silk  are 
placed  hung  on  sticks.  The  skeins  are  moved  about  in  this  bath  until  all  the  gum  has 
been  uniformly  taken  out.  The  silk  is  next  wrung  out,  rinsed  in  fresh  water  and  then 
dried.  Silk  may  by  this  process  lose  from  12  to  25  per  cent,  in  weight,  according  to  the 
quality  of  the  raw  silk  and  the  quantity  of  soap  employed.  The  scoured  silk  is  ready 
for  dyeing  with  dark  colours,  but  if  required  to  be  dyed  with  bright  colours  it  has  to  be 
first  boiled.  To  this  end  it  is  put  into  coarse  canvas  bags,  each  containing  from  12  to- 
1 6  kilos,  of  silk,  and  in  these  sacks  the  silk  is  placed  in  a  soap  bath  and  boiled  for  i£ 
hours  :  the  silk  is  next  rinsed  in  water,  wrung  out,  and  dried.  The  operation  of  rosing 
or  colouring  aims  at  imparting  to  the  silk  a  slight  tint  in  order  to  enhance  its  beauty. 
The  trade  distinguishes  various  hues  of  white  silk,  such  as  Chinese  white,  azure  white, 
pearl  white,  &c.  The  first  of  these  hues,  a  somewhat  ruddy  tint,  is  obtained  by  rinsing 
the  silk  in  soap- water,  to  which  some  annatto  has  been  added.  The  bluish  hues  are 
produced  by  indigo  solutions.  The  bleaching  of  scoured  silk  is  effected  by  the  aid  of 
sulphurous  acid,  the  fibre  either  being  placed  in  a  room  where  this  gas  is  evolved  from 
burning  sulphur,  or  by  treating  the  silk  with  an  aqueous  solution  of  the  acid.  As  silk 
loses  a  great  deal  in  weight  as  well  as  in  body  by  the  scouring,  which  is,  however  r 
required,  because  raw  silk  does  not  permit  of  being  dyed,  it  has  become  the  practice  to 
produce  a  material  called  souple,  obtained  by  treating  the  raw  silk  with  boiling  water 


SECT,  vii.]  SILK.  807 

in  which  only  a  small  quantity  of  soap,  i  kilo,  to  25  kilos,  of  silk,  is  dissolved.  Instead 
of  this  soap  solution,  an  acidified  (with  dilute  sulphuric  acid)  solution  of  magnesium 
or  sodium  sulphate  is  sometimes  used.  The  silk  loses  by  this  process  only  from  4  to  10 
per  cent,  in  weight.  In  order  to  bleach  raw  silk  without  depriving  it  of  its  natural 
rigidity,  the  skeins  are  digested  at  a  temperature  of  from  20°  to  30°  with  a  mixture  of 
alcohol  and  hydrochloric  acid ;  this  liquor  becomes  green  in  colour,  and  the  deeper 
the  hue  the  whiter  the  silk.  The  silk  is  rinsed  in  water,  and  having  been  dried  will 
be  found  to  have  lost  only  about  2*91  per  cent,  in  weight.  The  alcohol  used  in  thi» 
process  may  be  readily  recovered  by  neutralising  the  acid  with  chalk  and  subsequent 
distillation. 

Means  of  Distinguishing  Silk  from  Wool  and  from  Vegetable  Fibres. — Owing  to 
the  manufacture  of  mixed  fabrics,  it  has  become  a  necessity  to  be  enabled  to  detect  and 
distinguish  silk  from  woollen  as  well  as  from  cotton  and  linen  fibres.  Microscopical 
investigation  aided  by  chemical  tests  is  resorted  to  for  this  purpose. 

The  animal  fibres  (silk,  wool,  and  alpaca)  are  at  once  distinguished  from  the 
vegetable  (flax,  hemp,  cotton),  by  the  fact  that  the  former  are  soluble  in  caustic  potash 
and  the  latter  not.  The  animal  fibres  on  being  singed  give  off  a  smell  of  burnt 
feathers,  and  when  ignited  in  the  flame  of  a  candle  are  almost  immediately  extinguished, 
a  carbonaceous  residue  being  left.  Cotton  and  linen  fibres  continue  to  burn,  do  not 
give  off  the  smell  of  burnt  feathers,  and  do  not  leave  a  carbonaceous  mass  when 
extinguished.  Wool  and  silk  are  coloured  yellow  by  nitric  acid  (i'2  to  1-3  sp.  gr.), 
cotton  and  linen  not  so.  Nitrate  of  protoxide  of  mercury  colours  animal  fibres 
intensely  red,  and  upon  the  addition  of  a  soluble  alkaline  sulphuret  this  colouration 
becomes  black.  Linen,  or  flax,  and  cotton  are  not  at  all  acted  upon  by  this  reagent. 
An  aqueous  solution  of  picric  acid  dyes  wool  and  silk  intensely  yellow,  but  not  so 
vegetable  fibres.  The  colourless  liquid  obtained  (according  to  Liebermann)  by  boiling 
a  solution  of  magenta  with  caustic  potash  does  not  impart  to  a  mixed  fabric  of  wool 
and  cotton  any  colour  at  all ;  but  when  the  fabric  is  thoroughly  washed  in  water,  the 
woollen  fibre  becomes  intensely  red-coloured,  while  the  cotton  fibre  remains  colourless. 
A  solution  of  ammoniacal  oxide  of  copper  in  excess  of  ammonia  dissolves,  first  silk, 
next  cotton,  but  not  wool.  When  wool  and  floret  silk  are  mixed  the  latter  may  be 
dissolved  by  successive  treatment  with  nitric  acid  and  ammonia,  while  wool  is  left. 
A  solution  of  oxide  of  lead  in  caustic  potash  or  soda  may  serve  to  distinguish  wool 
from  silk,  owing  to  the  fact  that,  in  consequence  of  the  former  containing  sulphur  and 
the  latter  not,  the  mixture,  when  wool  is  present,  becomes  black.  Sodium  nitro- 
prusside  is  undoubtedly  the  most  delicate  test  for  distinguishing  between  silk  and  wool 
in  solution  in  caustic  alkali,  because,  owing  to  the  sulphur  of  the  wool,  this  reagent 
produces  in  the  solution  a  violet  colouration. 

By  the  aid  of  the  microscope,  cotton,  wool,  and  silk  are  readily  distinguished  from 
each  other.  As  for  cotton,  it  is  fully  described  on  pp.  802,  813,  815,  and  its  micro- 
scopical appearance  illustrated  by  woodcuts,  as  also  are  silk  and  woollen  fibres.  Of 
the  latter  we  may  now  state  that,  whereas  cotton  fibre  consists  of  only  one  cell,  wool 
(as  also  hair  and  alpaca)  is  made  up  of  numerous  juxtaposed  cells ;  the  silk  fibre  being 
similar  to  the  secreted  matter  of  spiders  and  various  kinds  of  caterpillars.  The  silk  fibre 
(Fig.  547)  is  smooth,  cylindrical,  devoid  of  structure,  not  hollow  inside,  and  equally 
broad.  The  surface  is  glossy  and  irregularities  are  but  seldom  seen  on  it.  If  it 
is  desired  to  detect  in  a  woven  fabric  the  genuineness  of  the  silk,  it  is  best  to  cut  a 
sample  to  pieces,  place  it  under  water  under  the  object-glass  of  a  microscope  magni- 
fying from  120  to  200  times,  covering  it  with  a  thin  piece  of  glass.  The  round,  glazed, 
equally  proportioned  silk  fibre,  Fig.  547,  is  easily  distinguished  from  the  unequal  and 
scaled  wool  fibre  (TFin  Fig.  548),  and  from  the  flat  band -like  and  spiral  cotton  fibre 
(B  Fig.  549).  Under  the  microscope  also  the  admixture  of  inferior  with  superior  fibres 


8o8 


CHEMICAL  TECHNOLOGY. 


[SECT.  vii. 


of  silk  can  be  easily  detected.     A  small  microscope  known  as  a  "  linen  prover  "  is  sold 
for  these  examinations.* 

Fig.  548.  Fig.  549. 


Fig.  547- 


Silk. 


Cotton. 


VEGETABLE   FIBEES. 


Fig.  550. 


Vegetable  fibre,  essentially  cellulose,  C6HI00.,  forms  the  texture  of  plants.     With 
incrustations  it  forms  woody  fibre ;  in  long  threads  or  tufts  it  appears  as  flax,  hemp, 

cotton,  &c.,  which  constitutes  the  impor- 
tant groups  of  vegetable  fibres,  and  serves 
for  the  production  of  tissues,  paper,  and 
gun-cotton. 

Flax. — The  flax  used  in  spinning  is  the 
fibre  of  the  flax  plant,  Linum  usitatis- 
simum,  a  plant  of  the  class  Pentandrise, 
order  Pentagynise,  in  the  system  of  Lin- 
naeus, and  the  type  of  the  order  Linnacese 
in  the  natural  system  of  Botany.  The 
flax  is  gathered,  tied  in  bunches,  and  dried 
in  the  fields.  After  drying  the  plant  is 
combed  with  an  iron  or  flax  comb,  to 
separate  the  seeds,  and  is  then  bound  in 
thick  bunches.  The  flax  fibre  used  in 
linen  fabrication  lies  under  the  bark  of 

Bruckstelle.    lj¥IJ)Wk\  \     the  plant,  and  is  surrounded  by  a  gummy 

•mbstance,  or  pectose  according  to  J.  Kolb, 
which  must  be  removed  by  chemical  or 
mechanical  means  to  fit  the  fibre  for  in- 
dustrial purposes.  This  is  done  by  "  soft- 
ening "  or  "  rottening,"  by  which,  according  to  Kolb,  pectin-fermentation  is  set  up,  and 


Flax. 
Druclcstelle  =  Place  of  pressure. 


For  further  particulars  on  silk  Dr.  Bowman's  work  may  be  consulted  ;  and  for  an  account  of 
the  so  called  wild  silks  see  Handbook  of  the  Collection  of  the  Wild  Silks  of  India,  by  Thomas  Wardle 
(Her  Majesty's  Stationery  Office.)— [EDITOR.] 


SECT,  vii.]  VEGETABLE   FIBRES.  809 

the  pectin  converted  into  pectic  acid.  The  flax  is  kept  under  water  until  the  impurities 
float  on  the  surface,  leaving  the  fibre  intact ;  this  is  the  soaking  method.  Another 
method,  dew-softening,  as  it  is  termed,  consists  in  spreading  out  the  flax  in  layers 
to  the  influence  of  the  atmosphere,  water  being  occasionally  thrown  over  the  flax. 
Both  these  methods  are  unsound,  as  the  flax  is  liable  to  become  rotten,  while  the 
impurities  are  not  thoroughly  removed. 

Hot-water  Cleansing. — -After  many  experiments  with  different  chemical  substances, 
an  alkaline  bath  and  dilute  sulphuric  acid  have  been  found  the  best  agents  to  effect  the 
separation.  The  flax  is  placed  in  large  vessels  of  water  heated  by  steam  from  25°  to  30°  ; 
after  standing  from  sixty  to  ninety  hours  the  operation  is  complete.  This  mode  of  treat- 
ment, aided  by  an  alkaline  or  acid  solution,  yields  the  best  results,  the  value  of  the 
process  being — (i)  That  the  construction  of  the  fibre  is  equally  affected,  rendering  the 
article  better  suited  for  manufacture.  (2)  That  the  fibre  does  not  lose  weight  as  in  the 
other  methods,  where  10  per  cent,  is  sometimes  lost.  (3)  That  there  is  a  considerable 
saving  in  expense. 

The  retted  flax,  as  it  is  technically  termed,  consists  of  cellulose  and  pectic  acid.  The 
next  process  is  termsd  scutching,  and  includes  the  separating  of  the  fibre  from  the 
woody  structure  of  the  stem.  The  machine  for  this  purpose  consists  of  two  parts ;  the 
upper  of  wood,  in  the  form  of  two  splints,  working  on  hinges.  Wooden  knives 
are  placed  under  the  splints,  and  are  arranged  to  act  upon  the  fibre  by  pressure  upon 
a  handle. 

Beating  or  Batting  the  Flax. — Scutching  consists  of  two  operations — bruising  the 
flax  and  beating  away  the  woody  parts  from  the  fibre.  For  the  latter  operation  the 
Belgian  batting-hammer  is  generally  used.  It  is  a  deeply  grooved  wooden  block, 
furnished  with  a  long  curved  handle.  The  sheaf  of  flax  is  laid  on  the  ground,  untied, 
and  spread  out,  and  is  beaten  with  the  hammer  by  the  workman.  If  the  flax  is  not 
sufficiently  loosened  by  batting,  it  is  submitted  to  the  swinging-block,  having  a  cut 
at  three-fourths  of  its  height  serving  to  hold  about  a  handful  of  flax.  This  flax  is  then 
beaten  with  the  scutch-blade,  a  piece  of  hard,  tough  wood,  generally  walnut-wood. 
Instead  of  the  swinging-block  a  grinding-knife  is  sometimes  used  on  an  iron  block. 
The  knife  is  formed  of  a  thin  blade,  and  a  heavy  wooden  handle.  A  bunch  of  flax  is 
held  in  the  left  hand,  at  an  angle  for  the  easy  use  of  knife  with  which  the  flax  is 
beaten.  Notwithstanding  these  clarifying  processes  the  bark  still  adheres  to  the  flax, 
which  has  to  undergo  a  further  operation,  that  of  combing. 

Combing  the  Flax. — The  combing  or  hackling  of  the  flax  removes  all  the  material 
detrimental  to  the  ultimate  spinning  of  the  fibres,  and  also  equalises  their  length, 
rendering  them  smooth  and  parallel.  The  combs  are  made  of  zinc  or  steel,  and  are  of 
varying  degrees  of  fineness,  the  process  commencing  with  a  coarse  comb  and  finishing 
with  a  fine  one. 

Tow,  or  Tangled  Fibre. — However  carefully  the  operation  of  scutching  may  be  per- 
formed, there  is  always  a  certain  amount  of  waste  resulting  from  the  entanglement  of 
the  fibre,  and  this  waste  is  termed  scutching-tow  or  codilla.  It  is  used  in  the  manu- 
facture of  ropes,  and  for  similar  inferior  purposes.  The  flax  fibre,  before  it  is  fitted 
for  spinning,  has  to  be  boiled  in  an  alkaline  lye,  to  remove  the  dirt  and  grease. 

100  kilos,  of  cleansed  flax  weigh  after 

Bruising  .         .         .         .         .     45  to  48  kilos. 
Scutching          .         .         .         .     15  „  25      „ 
Combing  ....  10      ,, 

Flax  Spinning. — The  spinning  of  the  combed  flax  into  yarn  is  effected  by  hand  and 
by  machinery.  The  combed  flax  is  first  placed  in  bands  of  equal  thickness,  and  then 
stretched.  The  hand  spinning-wheel  is  universally  known.  The  mechanical  spinning 
•consists  in — (i)  Placing  the  fibres  in  a  parallel  series  of  equal  thickness  and  length 


8ro 


CHEMICAL  TECHNOLOGY. 


[SECT.  vii. 


throughout.  (2)  These  bands  are  stretched,  the  finer  the  fabric  to  be  woven  the 
greater  being  the  stretching  required.  (3)  By  further  stretching  and  twisting  cord  is 
spun.  (4)  The  fine  cord  is  still  further  stretched  and  twisted.  Tow,  or  codilla,  is  spun 
similarly  to  the  flax,  being  previously  combed  and  placed  in  bands  of  equal  length. 
Flax  yarn  is  either  used  unbleached  or  is  bleached  before  spinning.  Linen  thread  is 
obtained  by  twisting  sevei'al  cords  together. 

Weaving  the  Linen  Threads. — By  weaving  the  cords  parallel  to  each  other,  chain 
cords  are  spun.  Webbing,  wrappers,  and  thick  fabrics  are  made  in  this  way. 

Linen. — Linen  is  produced  by  weaving  the  twisted  cord.  The  selvage  is  made  by 
the  return  of  the  shuttle  on  each  side  of  the  fabric.  For  coloured  fabrics  coloured 
threads  are  used  instead  of  white,  only  more  shuttles  are  required,  one  shuttle  to  each 
colour.  Linen  damask,  as  well  as  drill,  is  woven  in  various  patterns,  the  difference 
being  that  the  woof  forms  the  pattern  on  drill,  while  chain-cord  is  used  for  that  of 
damask.  Batiste  is  a  fine  linen  cloth,  slightly  thinner  than  cambric. 

Hemp. — Hemp  (Cannabis  sativa)  is  ohiefly  cultivated  for  the  fibre  of  its  inner  bark. 
This  fibre,  although  rough,  is  very  hard  and  firm,  and  better  adapted  for  the  manu- 

Fig-  552- 


Hemp. 


Hemp,  when  spun. 


553- 


facture  of  sail-cloth,  canvas,  rigging,  &c.,  than  any  other. 
Its  uses  for  inferior  domestic  purposes  are  manifold. 
The  working  of  the  hemp  stalk  accords  essentially  with 
that  of  flax,  being  steeped  in  water,  dried  and  crushed  in 
a  hemp  mill.  By  the  old  method  the  husk  is  crushed 
under  a  large  stone  cone  moving  in  a  circular  course 
around  a  vertical  axis.  The  construction  of  the  new 
hemp  mill  is  more  advantageous.  The  hemp  is  purified 
by  winnowing  and  afterwards  combing.  It  is  difficult  to 
spin  on  account  of  its  length,  and  is  woven  in  two  or 
three  parts.  Of  late  various  foreign  fibres  have  been 
used  as  substitutes,  principally  the  following : — 

a.  Stalk  Fibre. 

(i)  Chinese  Grass  (Chinagras,  Tschuma),ei  fibre  from 
Urtica  s.  Boehmeria  nivea  and  heterophylla,  which  is  cul- 
tivated in  China  and  the  East  Indies,  Mexico,  the  Valley 
of  the  Mississippi,  Cuba,  the  Wolga  Plains  in  Russia,  the 
South  of  France,  and  in  Algiers.  The  Chinese  method  of  treating  the  fibre  is 


Chinese  Grass,  Tschuma. 


SECT.    VII.] 


VEGETABLE    FIBRES. 


811 


remarkable.  The  fibre  is  not  spun,  but  cut  into  appropriately  small  pieces,  these 
being  placed  end  to  end,  and  rolled  by  the  hand  until  joined  together.  The  fibre  is 
thus  rolled  quite  smooth  and  does  not  require  pressing.  It  forms  a  beautiful  texture 
of  singular  brightness,  called  grass  linen,  or  China  grass  cloth.  The  raw  material  is 
of  a  green  or  brown  colour,  but  when  bleached,  can  be  dyed  any  colour. 

(2)  The  Great  Nettle  (Fig.  554),  Urticas.  dio'ica.    The  interior  fibrous  pith  supplies 
the  material  for  nettle  cloth  and  muslin. 

Fig-  554- 


II 


Nettle  Fibre. 


(3)  Ramie  Hemp,  from  Urtica  s.  Boehmeria  utilis,  is  of  the  nettle  species,  and  a 
native  of  Borneo,  Java,  Sumatra,  and  other  islands  of  the  Indian  Archipelago.    Of  late 
various  experiments  as  to  its  mode  of  manufacture  have  been  tried  in  Germany.     It  is 
from  one  to  two  metres  in  length,  of  a  delicate  golden  white,  and  not  so  bright  and  stiff 
as  flax. 

(4)  Rhea  Grass,  Urtica  s.  Rhea  tenacissima,  is  a  native  of  the  East  Indies,  of  little 
value  for  manufacture. 

(5)  Jute  (paut  hemp)  is  obtained  from  a  lime  tree,  a  native  of  the  East  Indies  and 
China,  Corchorus  caf>sularis,  G.  textilis,  G.  olitorius,  C.  siliquosus  (Figs.  555,  556).     The 
fibre  for  spinning  is  brown,  and  in  England  is  used  for  sackcloth  and  coarse  packing 
thread.     It  is  not  a  material  adapted  for  purposes  of  nautical  application,  as  it  has  not 
sufficient  firmness  to  withstand  water. 

Queensland  Hemp,  the  bast-fibre  of  various  species  of  sida,  belonging  to  the  family 
of  the  Malvaceae. 

(6)  Bombay  Hemp,  from  Hibiscm  cannabinus.     The  woody  fibre  of  this  plant  is 
roasted  and  separated  by  means  of  beating.      In  England  it  is  used  for  cordage, 
rigging,  &c. 

(7)  Sun  Hemp,  Japan,  or  East  Indian  Hemp,  from  Crotolaria  juncea,  resembles 
other  hemp  in  the  length  and  firmness  of  its  fibre. 

p.  Leaf  Fibre. 

(8)  New  Zealand  Flaxes  (Phormium  tenax),  Fig.  557,  are  employed  in  their  native 
country  for  articles  of  domestic  use.     The  leaf  is  straight,  the  fibre  tough,  and  of  a 


&12 


CHEMICAL  TECHNOLOGY. 


[SECT.  VH. 


shining  white.     The  prepared  material  is  similar  to  ordinary  hemp  in  roughness  and 
stiffness. 


Fig.  555- 


Fig.  556. 


Jute. 


557- 


(9)  Aloe  Hemp  (Agave  Americana,  A.  vivipara,  A. 
foetida,  &c.)  is  a  native  of  Peru,  India,  the  Antilles, 
and  Mexico,  where  the   leaf,  which  is  generally   a 
yellow-white,  is  cultivated  for  its  fibre,  and  used  for 
rope-making. 

(10)  Manilla  Hemp  (Feather  Fibre)  is  a  native  of 
India  and  many  islands  of  the  Malay  Archipelago,  and 
comes  from  Musa  textilis,  M.  troylodytarum,  and  M. 
paradisiaca.     It  is  commercially  known  as  a  yellow- 
white  or  brown-yellow  fibre,  and  is  from  1*3  to  2*2 
metres  long.     The  inside  bark  is  stripped  off  from  the 
bottom  upwards,  refined,  and  combed.    The  white  kind 
is  silky  and  bright,  and  is  used  in  the  manufacture  o.f 
damask  furniture  and  various  fancy  articles. 

(n)  Ananas  Hemp  comes  from  the  West  Indies, 
Central  and  South  America,  where  the  common 
ananas  is  cultivated,  Ananassa  sativa  s.  Bromelia 
ananas,  as  welt  as  other  species.  It  is  rather  inferior 
to  some  fibres  for  spinning. 

(12)  Pikaba  Hemp  is  from  the  leaf  of  the  Attalia 
funifera,  a  Brazilian, palm.  It  is  used  in  rope-making. 

(13)  Cocoa-nut  Fibre  is  a  reddish-brown  fibrous  material,  in  which  the  cocoa-nut 
shell  (Cocos  nucifera)  is  enveloped.  It  is  very  strong  and  elastic,  and  is  used  for 
matting,  ropes,  hurdles,  &c. 

Cotton. — Cotton  surrounds  the  fruit  of  a  shrubby  plant  of  the  species  Gossypium,  cul- 
tivated in  the  tropics  and  the  Southern  States  of  America  for  manufacturing  purposes. 


Phormium  Tenax. 


SECT.    VII.] 


VEGETABLE   FIBRES. 


The  fruit  consists  of  a  cup-shaped  calyx,  enclosed  in  a  three-cleft  exterior  calyx,  bearing 

a  soft  white  down.     Another  species,  Gossypium  religiosum,  bears  a  yellow  down,  used 

by  the   Chinese  in  manufacture.     The  down  is  kept  separate  from  the  seed  when 

packed  for  travelling,  to  prevent  its  becoming  oily 

and  unfit  for  use.     While  in  a  raw  state,  it  is 

subjected  to  an  operation  termed   ginning  in  a 

saw-gin,   to   separate   the   wool   from   the    seed. 

Whitney's  saw-gin  consists  of  from  1 8  to  20  circular 

saw-blades,  revolving  on  a  horizontal  axis  about 

100  'times  a  minute.      The  teeth  of  these   saws 

project  through  a  grating,  seize  the  wool  and  pull 

it  through,   the   bars  of   the    grating  being  too 

narrow  to  admit  the  seed.     Twenty  saw-blades  will 

clean    400  Ibs.,    and    80    saw-blades,  worked  by 

2-horse  power,  500  Ibs.,  raw  cotton  per  day.     Of 

late    the    carding    cylinder    is    sometimes   used 

instead  of  the  saw-gin.     In  America  oil  is  largely 

extracted  from  the  seed,  30  Ibs.  yielding  about 

i  Ib.  of  oil.     The  seed  is  also  used  for  manure. 
Species  of  Cotton. — The  quality   of    cotton  is 

decided  by  its  smoothness,  and  distinguished  by 

the  country  from  which  it  is  imported.  The  various 

kinds  are  : — North  American :  Sea  Island,  or  Long 

Georgia,  Orleans,   Upland,   Louisiana,  Alabama, 

Tennessee,  Georgia,  Virginia.     South  American  : 

Fernambuco,  Bahia.     Columbian  and    Peruvian. 

Barthelemy.     East  Indian  :    Dhollerah,   Surat,    Manilla,  Madras,  Bengal.     Levant : 

Macedonian,  Smyrna.     Egpytian  :    Mako  or  Jumel.     Australian :  Queensland.     Euro- 
pean :  Spanish  and  Sicilian. 

/Substitutes  for  Cotton. — Substitutes  for  cotton  are  found  in  the  black  poplar 
(Populus  ncgrra)andthe  aspen  (P.  tremula)  ;  the  fibres  of  the  latter  are  not  so  elastic  as 
some  of  the  substitutes  discovered.  The  rush  (Juncus  effusus],  the  German  tamarisk, 
and  the  thistle  (Ayrostis),  the  Salix  pentandra,  the  Zostera  marina,,  and  the  flax  tree, 
supply  material  for  manufacture.  Some  twenty  years  ago  Chevalier  Claussen 
endeavoured  to  open  the  filaments  of  flax  by  chemical  action  by  steeping  the  fibres  in 
a  bath  of  t  part  sulphuric  acid  to  200  parts  water,  and  then  dipping  it  into  a  weak 
solution  of  carbonate  of  soda.  By  this  process  the  flax  is  changed  into  a  downy  mass 
resembling  cotton  in  lightness ;  but  the  method  was  not  successful,  as  the  firmness  of 
the  fibre  was  injured,  and  its  value  deteriorated  in  other  ways. 

Detecting  Cotton  in  Linen  Fabrics. — There  is  a  great  difficulty  in  detecting  cotton 
in  linen  fabrics  when  the  fibres  are  closely  interwoven.  The  old  method  of  testing  the 
presence  of  cotton  in  linen  was  by  placing  it  under  a  powerful  microscope,  but  chemical 
analysis  presents  more  reliable  methods.  The  following  tests,  recommended  by  Kindt 
and  Lehnert,  prove  the  existence  of  cotton  in  linen  by  absorption.  The  linen  con- 
taining cotton  fibre  is  placed  in  a  bath  of  sulphuric  acid  of  1-83  sp.gr.  for  from  i  to  i| 
minutes.  The  cotton  fibre  is  immediately  absorbed,  the  sulphuric  acid  acting  upon  it 
more  quickly  than  upon  the  linen ;  the  fabric  upon  being  dried  has  a  curled  or 
shrivelled  appearance.  Other  fibres — sheep's  wool,  silk,  and  flax — are  now  treated 
chemically,  and  their  smoothness  and  glossiness,  which  are  found  to  be  the  greatest 
preservatives  against  decay,  are  attributable  to  chemical  agency.  The  colour  test  of 
Eisner  is  useful,  but  not  always  successful,  on  account  of  the  transition  of  the  delicate 
colours  being  so  instantaneous  as  to  make  it  difficult  to  form  a  decision.  As  a  colour 


Cotton,  spun.  Cottoii,  unspun. 

West  Indian :    Domingo,  Bahama, 


CHEMICAL  TECHNOLOGY.  [SECT,  vn 

test  there  may  be  taken  half  an  ounce  of  the  root  Rubia  tinctorum,  i.e.,  madder,  macerated 
for  twenty-four  hours  in  6  ounces  of  alcohol  at  94  per  cent.  When  filtered,  the  tincture 
appears  a  clear  brown-yellow.  Pure  linen  fabrics  immersed  in  it  become  a  dull 
orange  red,  and  pure  cotton  yellow ;  the  flax  fibre  will  assume  a  yellow  red,  and  the 
cotton  a  bright  yellow,  the  fabric  appearing  not  uniform  in  colour  but  streaky.  When 
the  fabric  becomes  so  unequally  streaked  as  to  make  it  difficult  to  discern  whether  it  be 
linen  or  cotton,  the  following  test  will  prove  decisive  : — Place  the  streaky  fabric  in  a 
solution  of  spirits  of  wine,  and  then  in  a  weak  solution  of  aniline  red,  by  which  it 
becomes  coloured,  and  finally  let  it  remain  from  one  to  three  minutes  in  a  weak  solution 
of  sal  ammoniac;  the  colour  of  the  cotton  fibre  will  be  dissipated  and  the  linen  will 
become  a  beautiful  rose  red.  From  Eisner's  first  test  for  change  of  colour  the  method 
of  previously  colouring  the  linen  fabric  was  established.  Cochineal  was  selected  for 
this  purpose,  and  the  linen  placed  in  a  weak  solution,  chloride  of  lime  being  used  to 
prevent  the  colour  in  the  linen  running,  while  the  cotton  contained  in  the  fabric 
changes  colour  immediately.  Frankenstein's  oil  test  for  uncoloured  fabrics  can  be 
recommended  for  its  simplicity  and  excellence.  The  fabric  is  dipped  in  olive  or  rape- 
seed  oil ;  it  quickly  becomes  soaked  through,  and  the  surplus  oil  is  removed  by  blotting- 
paper,  the  linen  fibre  becoming  transparent,  leaving  the  cotton  opaque.  When  an 
unbleached  fabric  is  tested  in  this  manner  it  appears  shining  at  first,  but  becomes 
dimmer  in  the  parts  where  the  cotton  is  present.  A  truer  method  of  testing,  however, 
is  given  by  the  magnifying  glass.  Bottger  gives  a  test  with  potash.  The  linen  fabric 
is  immersed  in  a  concentrated  solution  of  potash ;  in  about  two  minutes  it  becomes  a 
deep  yellow,  the  cotton  fibre  assuming  a  light  yellow. 

Stockhardt  gives  a  spirit  test.  Linen  fabrics  are  placed  in  layers  with  lighted 
brandy ;  the  linen  fibre  extinguishes  the  flame,  while  the  cotton  acts  as  a  wick,  absorb- 
ing the  spirit.  This  experiment  can  be  successfully  used  with  coloured  materials, 
with  the  exception  of  those  coloured  with  chrome  yellow,  lead  chromate.  The 
singeing  test  requires  the  most  delicate  treatment.  The  fibre  is  placed  in  a  glass 
vessel  over  the  flame  of  the  spirit-lamp  until  it  becomes  a  light  yellow ;  then  by 
microscopic  examination  the  cotton  fibres  will  be  found  curled  up,  while  the  flax  fibres 
are  distended  and  clearly  separated  from  each  other.  Hemp  and  flax  act  in  the  same 
manner,  but  do  not  separate  so  much.  Nitric  acid  can  be  so  applied  as  to  leave  the 
flax  fibre  unchanged  in  colour,  while  the  hemp  immediately  becomes  a  pale  yellow,  and 
the  New  Zealand  flaxes,  Phormium  tenax,  a  blood  red.  The  admixture  of  cotton  in 
linen  fabrics  is  detected  by  the  following  test,  the  discovery  of  0.  Zimmermann : — 
Place  the  fabric  in  a  mixture  of  2  parts  saltpetre  and  3  parts  sulphuric  acid  for  from 
eight  to  ten  minutes,  then  wash,  dry  and  treat  with  alcohol  containing  ether.  The  cotton 
so  treated  is  soluble  as  collodion,  the  linen  fibre  is  not. 

Separation  of  Animal  and  Vegetable  Fibres  by  Means  of  Singeing. — The  mixture  is 
placed  near  a  bright  flame  to  singe  until  the  hair  is  consumed,  leaving  a  black  ashy 
mass  in  the  same  proportion  as  the  fibre,  if  it  be  mixed  with  sheep's  wool. 

Animals  and  flaxen  fibres  are  separated  by  boiling  in  potash,  which  loosens  the 
filaments  of  wool  or  silk,  leaving  the  cotton  and  linen  fibres  unaltered.  Pohl  gives  us 
the  following  test : — Place  the  fibres  in  a  solution  of  picric  acid  for  one  minute ;  then 
carefully  wash ;  the  wool  or  silk  filaments  will  have  turned  yellow,  the  cotton  or  flax 
fibre  remaining  white ;  this  can  be  applied  to  mixed  fabrics.  The  most  certain  method 
is  examination  under  the  microscope,  where  the  linen  fibre  appears  in  a  cylindrical  forn? 
and  never  flat ;  it  is  not  stiff  or  twisted,  and  is  chiefly  characterised  by  the  narrow- 
ness of  its  inner  tube.  Hemp  is  similar  to  flax  fibre,  being  easily  broken ;  its  ends 
branch  out  stiffly,  and  its  tube  is  open.  The  fibres  in  cotton  fabrics  are  long,  of  a  close 
'thin  texture,  like  a  twisted  band.  Sheep's  wool  under  the  microscope  appears  thicker 


SECT,  vii.]  BLEACHING.  815 

than  the  other  filaments,  having  a  perfectly  circular  stalk  with  tile-shaped  scales.  The 
silken  fibre,  Fig.  559,  is  a  slender  column,  smooth  on  the  exterior  and  easily  dis- 
tinguishable from  wool,  Fig.  561  representing  a  mixed  silken  and  woollen  fabric,  as  it 
appears  under  a  low  power.  Wool  and  cotton,  Fig.  560,  are  also  easily  distinguished 
from  one  another.* 

Fig.  560. 


Fig-  559-  ^         i  **** 


Adulteration  of  Cotton  Fabrics. — No  other  name  can  be  given  to  the  dressing 
cottons  with  salts  of  magnesium,  china  clay,  &c.,  to  an  extent  sometimes  exceeding 
50  per  cent.  This  practice  is  carried  to  such  a  length  that  the  finished  goods  are 
sometimes  sold  for  a  lower  price  than  the  same  weight  of  raw  cotton. f 

BLEACHING. 

The  operation  of  bleaching  aims  at  more  or  less  perfectly  whitening  or  decolourising 
the  yarns  spun  from  flax,  hemp,  jute,  cotton,  or  the  textile  fabrics  woven  from  the 
same.  Vegetable  fibre  resists  the  action  of  most  chemical  agents  in  use  in  bleach- 
ing, while  the  foreign  or  incrustating  or  colouring  matters,  occurring  chiefly  on  the 
surface  of  the  fibre,  are  rendered  soluble  or  completely  destroyed.  The  bleaching  of 
the  fabrics  and  fibres  which,  such  as  linen  or  cotton  tissues,  consist  mainly  of  cellulose, 
is  based  on  this  principle.  The  method  of  bleaching  wool  and  silk  differs  from  that  of 
the  vegetable  fibres,  inasmuch  as  the  chemicals  used  for  the  latter  would  exert  upon 
the  former  a  solvent  action,  not  only  as  regards  the  impurities,  but  the  substance 
itself. 

Grass  Bleach. — The  agent  in  natural  or  grass  bleaching  is  apparently  ozone,  or 
doubtless  more  accurately  hydrogen  peroxide.  In  this  process  the  formation  of  ozone 
is  due  to  the  decomposition  of  water  in  consequence  of  the  action  of  light. 

Chlorine  Bleach. — Schiitzenberger  regards  chloride  of  lime  as  an  oxidising  agent, 
and  not  as  a  source  of  chlorine.  Without  the  co-operation  of  an  acid  it  is  split  up 
into  calcium  chloride  and  oxygen  (CaOCl2  =  CaCl2  +  0),  which  latter  destroys  the 
colouring  matter.  Witz  remarks  hereby  that  the  slightest  trace  of  carbonic  acid 

*  For  further  information  the  reader  is  referred  to  The  Structure  of  the  Cotton  Fibre  in  its 
Relation  to  Technical  Application,  by  Dr.  F.  H.  Bowman,  F.L.S.,  F.C.S.,  &c.  Manchester:  Palmer 
&  Howe. 

t  See  Sizing  and  Mildew  in  Cotton  Goods,  by  G.  E.  Davis,  C.  Dreyfus,  and  P.  Holland  ;  Man- 
chester :  Palmer  &  Howe ;  and  The  Sizing  of  Cotton  Goods,  by  W.  Thompson ;  Manchester  : 
J.  Heywood.  It  must  not  be  forgotten  that  the  sizing  and  dressing  of  cottons  in  England  is  not 
carried  to  the  same  extent  as  the  "  loading  "  and  "  weighting  "  silks  on  the  Continent — a  fraud  the 
more  reprehensible  as  the  genuine  article  is  so  much  more  expensive  than  cotton. — [EDITOR.] 


8x6  CHEMICAL   TECHNOLOGY.  [SECT.  vn. 

makes  the  chloride  of  lime  much  more  efficacious.  Without  the  presence  of  carbonic 
acid  in  the  atmosphere,  chloride  of  lime  is  inactive  in  certain  bleaching  processes. 
Whilst  the  hypochlorous  acid  gives  off  oxygen  there  is  hydrochloric  acid  formed,  which 
in  turn  reacts  upon  the  chloride  of  lime,  and  so  continuously  increases  its  action,  which 
would  end  in  complete  combustion  of  the  organic  matter.  A.  Girard  ascribes  the 
destructive  effects  of  chloride  of  lime  to  the  formation  of  hydrochloric  acid,  which 
remains  free  in  spite  of  the  presence  of  CaC03  and  CaOCl2,  hydrating  the  cellulose 
and  converting  it  into  brittle  cellulose.  Witz  shows  that  ozone  produces  the  same 
modifications  of  cellulose  as  does  chloride  of  lime ;  in  this  case  hydratising  acids  are 
not  present,  and  consequently  Girard's  suppositions  cannot  hold  good. 

Witz  warns  us  against  baths  of  chloride  of  lime  which  are  too  strong  or  too  pro- 
longed, and  which,  if  applied  unequally  and  under  the  influence  of  air  and  light,  have 
inevitably  a  destructive  action.  In  practice  a  strength  of  07°  Tw.  should  not  be 
exceeded.  Hunter  shows  that  chloride  of  lime  is  cheaper  than  permanganic  acid  and 
similar  oxidising  agents. 

In  order  to  strengthen  the  action  of  solutions  of  chloride  of  lime,  G.  Lunge  recom- 
mends the  addition  of  acetic  or  of  formic  acid.  The  price  of  the  acid  need 
scarcely  be  considered,  as  only  a  small  quantity  is  required.  There  first  result  from 
acetic  acid  and  chloride  of  lime  free  hypochlorous  acid  and  calcium  acetate ;  during 
the  action  the  former  gives  up  oxygen,  and  is  converted  into  hydrochloric  acid,  which, 
in  conjunction  with  the  calcium  acetate,  is  at  once  transformed  into  calcium  chloride 
and  free  acetic  acid  ;  the  latter  acts  anew  upon  chloride  of  lime  : 

(1)  2CaOCl2    +    2C2H4O3    =    Ca(C2H302)2    +    CaCl2    +    2HOC1, 

(2)  2HOC1    =    2HC1    +    O2, 

(3)  Ca(C2H302)3    +    2HC1    -    CaCl,    +    2C2H402. 

The  hydrochloric  acid  produced  according  to  equation  (2)  is  never  present  in  a  free 
state,  as  it  at  once  reacts  upon  calcium  acetate  as  in  equation  (3).  This  is  very 
important,  as  hydrochloric  acid  attacks  the  fibres  on  prolonged  contact,  whilst  acetic 
acid  is  perfectly  harmless.  As  no  insoluble  calcium  salts  are  present,  the  treatment 
with  acids  after  bleaching  is  dispensed  with ;  this  not  merely  economises  acid  and  the 
trouble  of  the  subsequent  washing,  but  it  obviates  the  danger — especially  in  the  case 
of  thick  goods — of  any  traces  of  acid  being  left  adhering  to  the  fibre.  Such  traces 
become  concentrated  on  drying,  and  attack  the  fibre,  besides  being  injurious  in 
various  dyeing  operations.  The  acid  can  be  applied  in  various  ways  —  e.g.,  by 
adding  a  small  quantity  to  the  solution  of  chloride  of  lime  at  the  outset,  and  at  the 
end  of  the  ordinary  treatment  with  chloride  of  lime ;  by  passing  the  goods  (prior  to 
washing)  through  water  containing  a  very  small  trace  of  acetic  acid  ;  or  by  placing  them 
iu  water  very  slightly  acidulated  with  acetic  acid,  and  gradually  running  in  the  solution 
of  chloride  of  lime  with  constant  agitation.  If  the  goods  to  be  bleached  retain  a  little 
alkali  from  the  previous  bowking,  or  if  the  water  is  very  hard,  or  if  the  solution  of 
chloride  of  lime  contains  appreciable  traces  of  caustic  lime,  important  quantities  of 
acetic  acid  would  be  required  to  neutralise  the  bases  before  hypochlorous  acid  can  be 
set  free.  In  such  cases  acetic  acid  can  be  economised  by  using  a  portion  of  sulphuric 
or  hydrochloric  acid  in  its  place,  taking  care,  however,  that  no  free  mineral  acid  is 
present,  but  merely  acetic  acid.  This  is  easily  reached  in  practice  by  keeping  the 
reaction  very  faintly  acid  to  litmus-paper. 

According  to  Lunge  the  removal  of  the  last  traces  of  the  bleaching  agents  from 
fibrous  goods  may  be  effected  by  means  of  hydrogen  peroxide.  On  bleaching  with 
chloride  of  lime  the  hydrogen  peroxide  gives  off  its  active  oxygen  along  with  that  of 
the  hypochlorous  acid,  whereby  the  latter  (or  its  salts)  is  destroyed.  Hydrogen 
peroxide  can  also  be  used  as  "  antichlore  "  in  bleaching  vegetable  fibre  or  paper  stuff  in 


SECT,  vn.]  BLEACHING.  817 

order  to  increase  the  durability  of  the  bleached  goods,  and  to  remove  the  smell  of 
bleach  without  the  disadvantages  of  other  "  antichlores." 

Sulphurous  acid  bleaches  by  masking  the  colouring-matter,  and  in  few  cases  only 
by  its  destruction.  The  colouring  matters  of  many  blue  and  red  flowers,  fruits,  &c., 
form  colourless  combinations  with  sulphurous  acid  ;  but  the  colour  is  merely  concealed, 
not  destroyed ;  dilute  acids,  nitrous  vapours  diluted  with  air,  chlorine,  bromine  and 
iodine,  and  the  mere  action  of  heat,  destroy  the  bleached  sulphurous  compounds,  and  the 
original  colour  re-appears.  The  colouring-matters  of  yellow  flowers  are  not  bleached 
by  sulphurous  acid.  The  same  is  the  case  with  the  green  of  plants  (chlorophyll).  Many 
dyed  tissues,  such  as  indigo  blue  and  carmine,  are  at  first  not  affected  by  sulphurous 
acid,  but  bleaching  ultimately  takes  place,  the  colouring  matters  being  oxidised  under 
the  influence  of  light.  Bleaching  with  sulphurous  acid,  as  it  is  industrially  carried  out, 
is  not  a,  fast,  but  merely  a  fugitive  process,  which  disguises  the  colours  to  the  eye.  On 
mere  exposure  to  the  air,  the  sulphurous  acid  gradually  disappears  from  the  bleached 
goods,  especially  after  previous  friction,  so  that  many  bleached  tissues  resume  their 
original  colour  spontaneously.  Lunge  recommends  the  removal  of  the  fixed  sulphurous 
acid  by  a  weak  solution  of  hydrogen  peroxide. 

For  bleaching,  the  goods  are  suspended  in  the  sulphuring  chamber  on  rods  in  a  moist 
state  as  they  come  from  the  centrifugal  machine  after  washing.  They  are  covered 
with  a  layer  of  thick  cloth,  which  is  removed  from  time  to  time.  After  filling  the 
sulphur  chamber  (stove)  the  necessary  quantity  of  sulphur  is  placed  in  an  iron  pot  in 
one  corner,  set  fire  to,  and  the  chamber  is  tightly  closed.  The  sulphur  burns  as  long 
as  there  is  sufficient  oxygen  present  in  the  chamber  and  the  sulphurous  acid  condenses 
upon  the  moist  fibre.  According  to  Moyret  sulphurous  acid  acts  only  at  the  moment 
of  condensation,  and  he  compares  it  with  the  action  of  an  acid  in  the  nascent  state,  and 
he  describes  the  alleged  inertness  of  sulphurous  acid  in  solution  to  the  absence  of  this 
circumstance.  According  to  Lauber  gaseous  sulphurous  acid  owes  its  stronger  action 
merely  to  the  circumstance  that  in  the  gaseous  condition  it  comes  in  contact  with  the 
slightly  moistened  fibre  in  a  very  concentrated  state,  whilst  the  solution  of  sulphurous 
acid  finds  its  limit  at  the  point  of  saturation.* 

According  to  the  desired  purity  of  the  whites  the  goods  are  left  in  the  stove  for 
twelve,  twenty-four,  and  even  more  hours.  The  cover  of  cloth  serves  to  prevent  any 
drops  of  sulphuric  acid  formed  on  the  roof  of  the  stove  from  falling  upon  the  goods  and 
destroying  them  at  the  point  of  contact.  When  the  process  is  completed  the  air  of 
the  stove  is  forced  into  the  chimney  of  the  works  by  means  of  a  blast,  and  the  goods 
are  freed  from  sulphur  by  taking  them  through  dilute  hydrochloric  acid  at  a  hand 
heat.  Any  yellow  spots  which  have  been  formed  by  a  condensation  of  sulphur  dis- 
appear, and  the  white  comes  up.  Sometimes  the  stoving  is  twice  repeated  if 
a  particularly  good  white  (so-called  double-stove  white)  is  required.  The  goods  may 
also  be  treated  with  a  solution  of  soda,  in  which  case  sodium  bisulphite  is  formed  on 
the  fibre ;  this  process  is  especially  used  for  straw.  Sodium  bisulphite  is  used  on  the 
large  scale  for  bleaching  loose  wool ;  the  wool  is  steeped  for  some  hours  in  the  solution 
of  sodium  bisulphite,  and  then  taken  through  hydrochloric  acid  at  a  hand  heat. 

Cotton  is  bleached  by  steeping  in  boiling  water,  which  removes  all  soluble  matter. 
It  is  then  boiled  in  a  solution  of  soda.  After  the  dressing  and  grease  have  thus  been 
removed  the  cotton  is  treated  with  a  weak  caustic  soda-lye,  which  dissolves  away 
certain  resinous  matters.  The  goods  are  then  placed  in  a  clear  solution  of  chloride  of 
lime,  which  is  heated  by  the  admission  of  steam,  and  they  are  then  rinsed  by  a  passage 

*  Sodium  bisulphite,  known  in  commerce  as  leucogene,  has  some  advantages  over  the  fumes  of 
burning  brimstone.  Its  action  is  more  regular  and  it  does  not  injure  the  health  of  the  workmen. 
Liquid  sulphurous  acid  at  about  14°  Tw.  bleaches  silk  and  wool  better  than  the  fumes  of  burning 
brimstone. —[EDITOR.] 

3  » 


8i3  CHEMICAL   TECHNOLOGY.  [SECT.  vn. 

through  dilute  sours  (sulphuric  and  hydrochloric).  The  acid  is  finally  removed  by  an 
alkaline  bath. 

According  to  H.  Koechlin  the  raw  cotton  cloth  is  saturated  with  alkali  and  then 
steamed.  The  alkali  can  be  used  either  as  caustic,  or  carbonate,  or  as  soap.  The  dura- 
tion of  the  action  of  the  steam  varies  according  to  the  concentration  of  the  solution  and 
the  pressure  of  the  steam  from  a  few  seconds  to  several  hours.  As  in  the  ordinary 
bleaching  process,  this  treatment  is  preceded  by  an  acid  bath  and  a  passage  through 
the  solution  of  a  hypochlorite.  The  cotton,  in  the  state  of  yarn  or  cloth,  is  washed 
and  taken  through  a  bath  of  dilute  hydrochloric  and  sulphuric  acid  at  roi33  sp.  gr. 
It  is  then  allowed  to  lie  wet  for  one  hour  and  taken  through  the  solution  of  hypo- 
chlorite— preferably  sodium  hypochlorite — at  roo66.  The  cotton  is  then  allowed  to  lie 
in  heaps  for  an  hour,  washed,  and  passed  through  soda-lye  at  1-0704  sp.  gr.  It  is  then 
steamed  for  an  hour,  washed,  again  taken  through  a  bath  of  sodium  hypochlorite  of 
the  above  strength,  left  in  heaps  for  an  hour,  washed,  taken  again  through  a  bath  of  the 
strength  given,  again  washed  and  dried. 

The  bleaching  process  of  J.  Thompson  is  carried  out  as  follows  by  the  firm  of  Mather 
and  Platt,  of  Manchester.  For  removing  the  dressing  the  pieces  are  first  taken,  spread 
out,  through  a  solution  of  soda,  for  which  purpose  there  is  used  the  washing  machine 
commonly  employed  in  bleach  works.  They  are  then  laid  in  basket  trucks,  simply 
folded  backwards  and  forwards.  These  trucks  are  made  of  a  sheet-iron  texture, 
covered  with  zinc ;  they  can  convey  a  ton  weight  of  pieces,  and  run  upon  rails  laid  on 
the  floor  of  the  works.  The  trucks  when  full  are  at  once  run  into  the  new  Mather  work- 
ing-pan. This  pan  is  a  horizontal  cylinder  closed  at  its  front  by  a  door,  which  can  be 
lifted,  within  which  the  rails  are  continued  and  which  has  room  for  two  trucks  one  behind 
the  other.  The  door  hangs  from  a  chain  which  is  conveyed  over  pulleys  to  the  back  of 
the  cylinder  and  is  there  joined  to  a  piston  to  be  moved  by  steam  or  water-pressure. 
On  admitting  the  pressure-liquid  into  its  cylinder  the  door  is  quickly  raised.  The 
steam-tight  closure  of  the  door  is  effected  not  by  means  of  screw-bolts,  &c.,  but  the  frame 
of  the  door  is  made  wedge-shaped  below  and  the  front  margin  of  the  boiler  is  hollowed 
accordingly,  so  that  the  door  is  tightly  closed  by  its  own  weight.  These  arrangements 
promote  speed  in  loading  and  unloading.  After  two  trucks  full  of  pieces  moistened  with 
the  solution  of  soda  have  been  introduced,  steam  is  turned  in  at  the  pressure  of 
I  atmo.  To  protect  the  pieces  from  the  injurious  action  of  dry  heat,  they  are  continually 
moistened  with  a  weak  solution  of  soda,  or  with  caustic  lye  at  2  per  cent.  This  pro- 
cess is  effected  by  means  of  a  pump  which  constantly  sucks  up  the  liquid  from  the 
lowest  part  of  the  pan  and  then  squirts  it  out  over  the  trucks  by  means  of  a  perforated 
tube.  Instead  of  the  soda-solution  hot  water  is  then  conveyed  into  the  pan  and  the 
goods  are  washed  in  the  same  manner.  They  are  then  run  out  of  the  cylinder, 
which  immediately  receives  a  fresh  charge  in  the  same  manner,  so  that  6  tons  of  cloth 
can  be  prepared  daily  for  bleaching.  The  trucks  with  the  cloth  thus  freed  from  dres- 
sing are  run  to  the  bleaching  machine,  into  which  the  pieces  are  at  once  transferred,  so 
that  there  is  no  interruption  in  the  process. 

The  continuous  bleaching  machine  of  the  same  firm  is  an  essential  requisite  for  the 
proper  working  of  the  Thompson  bleaching  process,  since  by  its  means  the  repeated 
saturation  of  the  tissues  with  the  bleach  liquor,  the  subsequent  treatment  with  gaseous 
carbonic  acid,  and  the  repeated  washing,  are  rendered  possible  in  one  passage,  whether 
the  pieces  are  spread  out  at  full  width  or  folded  into  a  cord,  in  which  latter  case 
several  such  cords  can  be  treated  side  by  side.  The  pieces  move  at  the  rate  of  about 
60  metres  per  minute.  The  cloth  passes  first  into  the  washing  beck,  II  (Fig.  562), 
with  hob  or  cold  water,  and  after  being  nipped  between  two  rollers  it  arrives  at  beck  C, 
containing  the  bleaching  liquid  (mostly  a  solution  of  chloride  of  lime  at  0*4  per  cent.). 
After  leaving  the  nipping-rollers  of  the  beck,  (7,  the  pieces  pass  into  the  carbonic  acid 


SECT.   VII.] 


BLEACHING. 


819 


chamber,  K.  This  is  a  simple  sheet-iron  chest  with  guide-rollers  for  the  pieces,  and  pro- 
vided at  the  slits  left  for  the  entrance  and  exit  of  the  pieces  with  slips  of  caoutchouc, 
which  apply  themselves  to  the  cloth  and  prevent  the  escape  of  the  gas.  The  carbonic  acid 
is  introduced  by  a  pipe  at  the  bottom  of  the  chest, 
and  a  simple  arrangement  indicates  the  level  of  the 
<*as  in  the  chamber,  K.  At  one  of  the  sides  there 
is  a  gas-pipe  connected  above  and  below  with  the 
interior  of  the  chamber.  In  the  gas-pipe  a  thin 
parti-coloured  glass  bulb,  filled  with  air,  indicates 
the  level  of  the  carbonic  acid.  The  carbonic  acid, 
being  of  a  higher  specific  gravity,  keeps  the  glass 
bulb  suspended  at  a  height  corresponding  with  its 
own  level  in  the  chamber.  After  the  treatment  of 
the  pieces  with  carbonic  acid  there  follows  a  wash- 
ing with  water  and  a  o.i  per  cent,  solution  of 
soda  in  the  several  vats  Wv  JF2  and  W3,  then  a 
passage  in  a  hot  solution  in  S,  and  repeated  washing. 
The  beating  of  the  pieces  in  the  washing  becks  is 
effected  by  means  of  the  rollers  to ;  the  washing 
water  is  conveyed  upon  the  cloth  between  the  nip- 
ping-rollers through  the  spirting  tube  s.  The 
goods,  conveyed  for  a  little  into  the  open  air, 
arrive  for  a  renewed  similar  treatment,  are  washed 
in  the  vat  JF,  with  weak  hydrochloric  acid,  then 
with  water,  then  with  soda-solution  and  again  with 
water,  and  are  finally  conveyed  to  an  ordinary 
washing  machine  for  the  final  washing. 

The  advantages  of  the  Mather-Thompson  pro- 
-cess  (with  the  employment  of  the  plant  just  de- 
scribed) lie  chiefly  in  the  economy  of  time  and 
washing  water.  As  two  pieces  can  be  taken 
through  the  apparatus  side  by  side,  from  4500  to 
5000  kilos.,  or  36,000  to  40,000  metres,  of  goods 
can  be  bleached  in  a  day  of  ten  working  hours. 
But  if  we  also  include  the  time  needed  for  steam- 
ing, it  appears  that  from  2000  to  5000  kilos, 
(according  to  the  size  of  the  plant)  can  be  com- 
pletely bleached  in  eighteen  to  twenty  hours. 

The  process  above  described  is  used  for  cloth 
which  is  to  be  sold  white.  But  if  it  is  desired  to 
produce  good  whites  for  printing  the  pieces  are 
first  taken,  not  through  soda-lye,  but  through  hot 
sours.  The  steaming  is  effected  in  the  same  manner, 
only  to  2000  kilos,  of  cotton  there  are  added  10  kilos, 
of  resin,  previously  saponified.  The  chlorinising  is 
effected  in  the  manner  above  described. 

Latterly  a  bath  of  weak  hydrochloric  acid  has 
been  substituted  for  the  carbonic  acid  treatment. 
For  bleaching  on  the  large  scale  this  process  seems 
likely  to  supersede  all  others. 

Bleaching  with  chlorine  produced  electrolytically  has  been  repeatedly  attempted 
but  hitherto  without  noteworthy  results. 


820  CHEMICAL  TECHNOLOGY.  [SECT.  vii. 

In  bleaching  linens,  according  to  Kolb  it  is  necessary  to  remove  two  substances, 
pectic  acid  and  a  grey  substance  formed  during  the  rotting  of  the  flax.  This  is  effected 
either  by  the  grass  bleach  or  by  treatment  with  chloride  of  lime.  The  grey  matter  is 
oxidised  and  the  pectic  acid  is  removed  in  a  soluble  form. 

According  to  Cross,  jute  may  be  easily  bleached  by  treatment  with  the  permanga- 
nates and  subsequent  washing  with  dilute  acids  or  by  means  of  hydrogen  peroxide,  but 
these  two  processes  are  too  expensive. 

Cross  washes  the  cloth  with  a  solution  of  soluble  glass,  borax,  or  soda,  at  70°  to 
80°,  and  then  takes  it  through  a  solution  of  sodium  hypochlorite,  containing  07 
to  i  per  cent,  effective  chlorine,  corresponding  to  2  per  cent,  chloride  of  lime.  A 
slight  excess  of  soda  completely  prevents  the  formation  of  chlorinised  products  from 
the  fibre.  After  a  thorough  rinsing  the  goods  are  passed  into  cold,  dilute  hydro- 
chloric acid,  containing  a  small  quantity  of  sulphurous  acid  in  order  to  remove  salts 
of  iron  and  basic  compounds  which  might  subsequently,  in  contact  with  oxidising 
agents,  discolour  the  fibre.  If  thus  treated  the  jute  has  a  pale  cream  colour  and  a 
soft,  shining  appearance.  If  it  is  to  be  dyed  it  may,  after  a  thorough  rinsing,  be  at 
once  transferred  to  the  dye  beck.  If  intended  for  printing  the  pieces  are  first  placed 
in  a  bath  of  sodium  bisulphite,  containing  from  i  to  2  per  cent,  of  sulphurous  acid. 
Here  they  remain  two  or  three  hours  and  are  then  dried  on  steam  cylinders. 
Sulphurous  acid  escapes  and  the  goods  when  dry  are  uniformly  saturated  with  sodium 
sulphite,  which  subsequently  prevents  the  oxidising  and  destructive  action  of  steaming 
upon  the  fibre,  without  interfering  with  the  development  of  the  printed  colours.  The 
whiteness  of  the  goods  is  farther  improved  by  the  treatment  with  sodium  bisulphite. 

If  an  attempt  be  made  to  bleach  jute  with  chloride  of  lime  in  the  same  manner 
as  cotton  or  linen,  a  chlorinised  compound  is  formed  which  is  easily  recognised  by 
the  magenta-red  colour  which  it  assumes  if  moistened  with  sodium  sulphite.  If 
such  a  tissue  were  afterwards  steamed  hydrochloric  acid  would  be  set  free  by  the 
decomposition  of  the  chlorine  compounds,  a  dark  brown  colour  would  appear  and  the 
tissue  would  crumble  away.  Sometimes  these  changes  appear  only  after  the  cloth  has 
come  into  use,  which  increases  the  common  prejudice  against  jute.  This  fibre 
is  further  oxidised  by  hypochlorites  to  form  derivatives  which  produce  insoluble  lime 
compounds.  These  are  deposited  on  the  fibre,  so  that  the  common  bleaching  process 
converts  jute  into  a  rough,  brittle,  ill-smelling  product  of  low  quality. 

The  first  step  in  bleaching  silks  is  the  ungumming.  Silk  goods  which  are  to- 
remain  white  are  stoved.  To  mask  the  yellow  tint  which  remains  it  receives  a  slight 
red  tint  by  means  of  a  solution  of  annatto  in  soap-lye,  or  a  blue  reflection  with  aniline 
blue.  Latterly  silks  are  bleached  with  hydrogen  peroxide. 

Wool  bleaching  begins  with  scouring  effected  by  treatment  with  stale  urine  (lant) 
or  with  a  soap-bath.  The  bleaching  itself  is  performed  with  sulphurous  acid  in  the 
stove,  more  rarely  with  sodium  bisulphite  (leucogene). 

Wool  intended  to  be  bleached  with  hydrogen  peroxide  must  be  washed  clean.  If 
the  commercial  peroxide  is  diluted  with  10  parts  of  water  the  wool  should  be  treated. 
in  the  bleaching-bath  for  from  thirty  to  forty  minutes.  The  wool  must  have  sufficient 
room  in  the  vat  to  be  turned  readily,  as  this  expedites  the  bleaching.  If  the  hydrogen- 
peroxide  is  diluted  with  1 5  parts  of  water  the  wool  must  be  allowed  to  steep  for  an  hour 
after  it  has  been  taken  out  of  the  bleach-bath ;  the  action  continues  as  long  as  the. 
wool  is  moist.  Hence  it  should  not  be  dried  too  rapidly,  and  if  possible  it  should  be 
dried  in  the  open  air  with  exposure  to  the  sun.  If  a  very  dilute  peroxide  has  been 
used  a  very  small  quantity  of  extract  of  indigo— which  is  necessary  for  the  production 
of  a  pure  white — may  be  added  at  once  to  the  bath,  and  if  a  more  concentrated  peroxide 
bleach  is  used,  the  blue  tone  must  be  given  in  a  special  bath.  With  strong  yellow 
wools  it  is  well  to  add  to  the  bath  a  few  drops  of  dissolved  methyl  violet. 


SECT,   vii.]  DYEING   AND   TISSUE-PRINTING.  821 

DYEING  AND  TISSUE-PRINTING. 

Textile  fibres  are  capable  of  taking  up  colouring-matters  and  certain  constituents  of 
mordants  from  solutions  and  of  retaining  them.  The  combination,  however,  is  often 
so  unstable  that  it  is  easily  destroyed  by  repeated  treatment  with  solvents,  especially 
with  the  aid  of  heat.  Thus,  a  fibre  dyed  with  indigo  sulphate,  or  with  Prussian  blue 
dissolved  in  oxalic  acid,  can  be  decolorised  by  continual  washing.  The  fibre  is,  therefore, 
truly  dyed  only  when  the  dissolved  colouring-matter  forms  with  the  fibre,  and  mostly 
with  the  co-operation  of  a  third  substance,  a  mordant,  an  insoluble  compound  which 
cannot  be  removed  by  the  application  of  a  solvent.  According  to  Knecht's  recent 
investigations,  wool  forms  with  colouring-matters  actual  chemical  compounds.  The 
colour  thus  produced  is  called  fast  when  it  resists  the  weather,  light,  soap-lye,  dilute 
alkalies,  and  very  dilute  acids.  A  colour  which  is  destroyed  under  such  circumstances 
is  called  fugitive.* 

The  combination  of  the  fibre  with  the  colouring  matter  necessary  for  dyeing  may 
be  effected — (i)  by  removing  the  solvent.  Thus,  copper  oxide  dissolved  in  ammonia  can 
be  fixed  upon  the  fibre  by  the  mere  evaporation  of  the  ammonia.  The  precipitation  of 
carthamine  from  an  alkaline  solution  by  means  of  an  acid  and  the  precipitation  of  many 
tar-colours  soluble  in  spirit  by  the  addition  of  water,  likewise  belong  here.  An  in- 
soluble combination  can  also  be  produced — (2)  by  oxidation,  the  colouring-matter, 
previously  soluble,  being  rendered  insoluble  by  taking  up  oxygen.  Here  belong  besides 
ferrous  and  manganous  sulphate  which  form  insoluble  hydrates  on  oxidation,  the 
tanniferous  substances  which  at  the  same  time  contain  a  colouring-matter,  such  as 
quercitron  bark,  sumach,  fustic,  fustet,  &c.  If  we  saturate  cloth  with  the  watery  or 
alkaline  extract  of  these  substances  and  expose  it  to  the  air,  the  colouring-matter  is 
turned  brown  and  ceases  to  be  soluble  in  water,  possibly  in  consequence  of  the  form- 
ation of  substances  resembling  phlobaphene.  A  similar  change  is  effected  more 
quickly  if  tissues  saturated  in  this  manner  are  treated  with  oxidising  agents,  such  as 
potassium  chlorate,  chromic  acid  (alkaline  bichromates),  or  vanadium  compounds.  An 
instance  of  this  kind  is  black-dyeing  by  means  of  logwood  and  potassium  chromate, 
where  the  haematoxyline  of  the  wood  is  oxidised  to  haemateine,  and  the  chromic  acid 
is  reduced  to  a  chromium  sesquioxide.  Similar  is  blue-dyeing  with  indigo  in  the  vat 
and  the  production  of  aniline  black.  Often — (3)  the  insoluble  compound  is  produced  by 
double  decomposition — e.g.,  blue  by  a  soluble  ferrocyanide  and  ferric  oxide,  yellow  by 
potassium  chromate  and  a  soluble  salt  of  lead.  This  method  of  fixation  is  applicable 
only  with  mineral  colours.  The  most  important  method  of  fixing  colours  is — (4)  by 
means  of  mordants. 

Bancroft  divided  the  colouring-matters  into  substantive  and  adjective ;  the  former 
are  those  which  pass  into  an  insoluble  state  upon  the  fibre  without  the  intervention  of 
a  mordant,  as  all  the  mineral  colouring-matters,  indigo,  turmeric,  annatto,  safflower, 
and  most  of  the  coal-tar  colours.  By  adjective  colours  he  means  those  which  require 
some  mediating  agent  in  order  to  become  insoluble  upon  the  fibre.  These  mediating 
substances  are  the  mordants  in  question.  But  such  mordants  have  not  merely  the 
function  of  effecting  the  combination  of  the  colouring-matter  with  the  fibre.  They 
serve  in  certain  cases  for  effecting  such  a  change  in  tissues  already  saturated  with 
earthy  or  metallic  salts  that  the  parts  upon  which  they  have  been  placed  appear 
colourless  when  lifted  out  of  the  flot.  Such  mordants  are  called  discharges.  They 
include  the  phosphoric,  tartaric,  oxalic,  and  arsenious  acids.  Here  also  belong  the 
resists  used  in  tissue  printing.  Mordants  are  often  used  to  modify  the  tone  of  colours 
which  have  already  been  produced,  rendering  them  brighter  and  purer,  an  effect  which 
is  known  as  raising  (Fr.  aviviren  ;  Ger.  schoenen). 

*  Compare  Leo  Vignon,  Chem.  News,  vol.  Ixiii.  pp.  153,  177  &  285.— [EDITOB.] 


822  CHEMICAL   TECHNOLOGY.  [SECT.  vn. 

Among  the  most  important  mordants  are  the  salts  corresponding  to  the  sesquioxides- 
of  the  general  formula,  R203,  especially  the  salts  of  aluminium,  iron,  and  chrome. 
Here  it  is  important  to  present  solutions  of  the  salts  to  the  fibre  in  a  form  such  that. 
they  can  easily  and  completely  pervade  it  —  with  the  co-operation  of  the  fibre  itself  — 
and  to  deposit  upon  the  fibre  either  the  oxides  or  very  basic  salts.  The  insoluble  com- 
pounds of  aluminium,  iron,  chrome,  &c.,  deposited  in,  upon,  or  between  the  several 
fibres  and  tufts  of  fibre  form  the  mordant  in  the  stricter  sense  of  the  word.  They 
combine  with  the  colouring  matters  either  chemically,  or  in  the  opinion  of  some,. 
mechanically  only,  and  thus  effect  the  colouration  of  the  fibre,  which  would  otherwise 
be  impracticable.  The  compounds  of  antimony  are  also  important. 

The  chief  organic  mordants  are  turkey-red  oil  (alizarine  oil),  tannin  (especially  for 
fixing  the  madder  colours,  cochineal,  and  the  aniline  dyes  upon  cotton  and  linen), 
albumen,  gluten,  caseine,  glue,  glycerine  (sometimes  a  solution  of  arsenious  acid  in 
glycerine),  and  fatty  oils.  The  cloth  to  be  dyed  is  taken  through  these  mordants 
which  are  again  fixed  according  to  th.eir  nature,  either  by  airing,  by  the  dunging 
process,  by  the  bran  bath,  or  by  soaping,  and  the  tissues  are  then  introduced  into  the 
solution  of  colouring-matter. 

Alumina  mordants  were  used  by  the  ancients,  and  are  still  employed  on  all  kinds  of 
fibres.  Aluminium  sulphate,  Al2(S04)3.i8HsO,  is  decomposed,  according  to  the  re- 
searches of  Liechti  and  Suida,  by  soda  or  sodium  bicarbonate  : 

A12(S04)3   +   Na2C03   +   H20   =   A12(S04)2(OH)J   +    Na,SO4   +    C02, 
A12(S04)3   +    6NaHC03   =   A14(S04)3(OH)6   +•  3Na2S04   +    3COr 
A12(S04)3   +    4NaHC03   =   A12S04(OH)4   +    2Na2SO4 


The  more  basic  the  compound  the  more  alumina  is  deposited  upon  the  fibre. 
Similar  is  the  behaviour  of  aluminium  acetate,  whilst  aluminium  chloride  and  aluminium 
sulphocyanide  behave  less  favourably.  Thus,  in  order  —  e.g.,  to  mordant  cotton  it  is- 
saturated  with  a  solution  of  2  kilos,  aluminium  sulphate  and  0-32  kilo,  sodium  car- 
bonate in  10  litres  of  water,  diluted  if  requisite  to  1-05  sp.  gr.,  the  excess  is  removed 
from  the  cotton  by  pressure,  dried,  passed  for  five  or  ten  minutes  through  liquid 
ammonia  (0-5  per  cent.),  washed  and  dyed.  Instead  of  ammonia  there  may  be  used 
solutions  of  sodium  arseiiiate  or  phosphate,  soaps,  or  turkey-red  oil. 

Aluminium  acetates  and  sulphacetates  are  especially  used  in  calico-printing.  The- 
solutions  are  thickened  with  flour,  starch,  or  dextrine,  printed  upon  cotton  cloth  and 
dried.  Too  high  a  temperature  during  dyeing  must  be  carefully  avoided,  especially 
with  mordants  which  are  very  readily  decomposed  (basic  salts),  as  the  results  will 
otherwise  be  uneven  and  poor.  The  object  is  reached  by  the  use  of  hot  plates,  hot 
air,  &c.,  in  place  of  rollers  heated  by  steam.  If  too  strong  a  heat  is  employed  the- 
mordant  fixed  upon  the  fibre  is  deprived  of  its  water  of  hydration,  or  undergoes  some- 
physical  change  by  which  it  is  rendered  incapable  of  taking  up  colouring-matter. 
When  this  occurs  the  printed  mordant  is  said  to  have  been  burnt. 

Upon  printing  and  dyeing  follows  ageing,  which  consists  in  exposing  the  printed 
goods  in  a  more  or  less  open  state  to  an  atmosphere  at  a  suitable  temperature  and 
degree  of  moisture.  This  treatment  is  rendered  continuous  by  means  of  the  ageing 
apparatus,  a  large  chamber  heated  to  from  32°  to  38°,  whilst  at  the  same  time  steam  is- 
admitted  until  the  moistened  bulb  of  the  thermometer  stands  at  from  4°  to  6°  lower. 
The  printed  pieces  are  slowly  passed  over  and  under  a  set  of  rollers  fixed  at  the  top  andi 
bottom  of  the  chamber,  so  that  they  remain  exposed  to  the  moist,  warm  atmosphere  for 
from  twenty  to  thirty  minutes.  During  this  process  the  starch,  or  other  thickener,  is- 
more  or  less  softened  by  the  moisture  and  the  mordant  penetrates  more  completely  into> 
the  fibre.  Quantities  of  acetic  acid  are  expelled  and  an  insoluble  basic  salt  is  fixed 
upon  the  cotton.  Immediately  after  leaving  the  chamber  the  pieces  are  rolled  up 


SECT,  vii.]  DYEING   AND   TISSUE- PRINTING.  823 

loosely  and  left  lying  to  complete  the  ageing,  for  twenty-four  to  forty-eight  hours,  in  a 
room  in  which  the  dry-bulb  thermometer  indicates  32°,  and  the  wet-bulb  28°. 

The  next  treatment  is  the  so-called  "  dunging  "  (Fr.  bousage,  Ger.  Jcuhkothen),  in 
which  the  pieces,  spread  out,  are  drawn  for  two  minutes  through  hot  solutions  of  one 
or  more  of  the  following  substances  :  cow-dung,  sodium  arseniate,  phosphate  or  silicate, 
calcium  carbonate,  &c. 

The  purpose  of  dunging  is  three-fold.  Firstly,  to  retain  that  part  of  the  mordant 
which  was  not  affected  during  ageing  more  completely  upon  the  fibre ;  secondly,  to 
protect  the  unprinted  and  consequently  unmordanted  parts  of  the  tissue  from  the 
mordants,  so  that  they  may  not  be  stained  by  mordant  rubbed  off  from  the  printed 
parts;  and,  lastly,  to  remove  the  thickeners.  The  last  purpose  is  effected  more 
completely  if  the  dunging  is  repeated,  the  pieces  being  folded  up  in  the  form  of  cords 
and  passed  between  rollers.  The  most  effective  process  for  removing  the  thickenings, 
is  to  place  the  pieces  for  one  to  two  hours  in  a  bran-bath,  the  diastase  of  which 
quickly  converts  the  insoluble  starch  into  soluble  glucose.  After  thorough  washing 
the  printed  and  mordanted  cloth  is  ready  for  dyeing. 

Aluminium  acetates  (red  liquor)  are  very  generally  used  in  many  steam  colours  in 
calico  printing — e.g.,  in  the  so-called  alizarine  steam  reds.  In  the  colour  or  thickened 
mixture  for  printing  the  aluminium  acetate  is  merely  mechanically  mixed  with  the 
alizarine  or  other  colouring-matter ;  when  the  printed  cloth  is  exposed  to  steam  decom- 
position of  the  mordant  takes  place,  its  combination  with  the  colouring-matter  and 
the  fixation  of  the  coloured  compound  upon  the  fibre  also  occurring  simultaneously. 

Experiment  shows  that  pure  aluminium  acetate  does  not  give  such  full,  rich  colours 
as  do  double  compounds,  especially  A12S04  (C2H3O2)3OH.  Aluminium  acetates  are 
also  used  in  turkey-red  dyeing.  For  wool  dyeing  aluminium  acetate  is  unsuitable. 
Wolf  recommends  solution  of  ammonium  carbonate  for  fixing  aluminium  mordants 
upon  cotton.  The  use  of  this  agent  has  the  advantage  that  pure  aluminium  hydrate, 
only  a  small  part  of  which  is  combined  with  carbonic  acid,  is  deposited  upon  the  fibre, 
whilst  if  we  use  the  ordinary  dung-substitutes  (substances  other  than  cow-dung  used  in 
the  dunging  process)  we  obtain  basic  phosphates,  arseniates,  &c.,  the  acids  of  which 
are  much  less  readily  expelled  by  alizarine  or  other  dye-wares  of  an  acid  character ; 
that  is,  they  dye  up  more  slowly. 

According  to  experiments  the  ammonium  carbonate  exerts  a  favourable  action 
especially  in  the  case  of  mordants  containing  sulphocyanides,  and  it  is  altogether 
preferable  to  the  use  of  silicates  and  ammonia,  and  equal  to  sodium  phosphate  and 
arseniate.  In  comparison  with  the  former  it  has  the  advantage  of  producing  brighter 
shades.  Ammonium  carbonate,  other  points  being  equal,  is  preferable  to  the  arseniate 
on  account  of  the  poisonous  character  of  the  latter. 

Iron  Mordants. — The  use  of  ferrous  sulphate  (copperas)  as  a  mordant,  though  still 
considerable,  has  been  reduced  by  the  introduction  of  the  chrome  compounds ;  the 
ferrous  acetate  (black  liquor,  pyrolignite  of  iron)  is  more  important,  as  it  serves  for 
blacks,  purples,  and  chocolates  ;  it  should  be  as  free  as  possible  from  ferric  salts. 

Iron  pyrolignite  is  especially  used  for  dyeing  silks  black  and  for  the  fraudulent 
process  of  "  loading  "  or  "  weighting."  The  silk  is  steeped  at  4O°-5o°  in  a  solution 
of  tannin,  especially  extract  of  chestnut,  then  treated  with  iron  pyrolignite  of  1*06 
to  1*07  and  exposed  to  the  air.  This  treatment  is  repeated  from  twice  to  fifteen  times, 
and  the  weight  of  the  silk  is  increased  from  30  to  400  per  cent.* 

*  To  counteract  the  rusty  brown  tone  apt  to  be  thus  produced,  the  silks,  after  an  iron  bath 
(rouille)  are  taken  through  a  solution  of  potassium  ferrocyanide,  which  produces  a  deposit  of 
Prussian  blue  on  the  fibre.  It  must  be  remembered  that  by  the  weighting-process  silks  are  not 
merely  rendered  liable  to  a  slow  decay  (eremacausis),  but  they  become  capable  of  spontaneous 
(so-called)  combustion. 


824  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

Ferric  sulphate,  Fe2(S04)3,  erroneously  called  nitrate  of  iron,  as  it  is  obtained  by 
oxidising  copperas  with  nitric  acid,  is  largely  used  in  silk  dyeing,  especially  in  the  state 
of  the  basic  compound  :  1 2FeS04  +  3H2SO4  +  4HN03  =  3Fe4S04)5(OH2)  +  2H2O  +  4^0. 

In  mordanting  raw  silk  it  is,  according  to  Hummel,  first  treated  in  a  solution  of 
sodium  carbonate  at  40°  to  50°,  and  then  worked  for  half  an  hour  to  one  hour  in  a  cold 
solution  of  the  mordant  at  14°  Tw.  The  silk  is  then  taken  out,  well  washed,  and  left 
to  steep  for  thirty  minutes  in  a  solution  of  sodium  carbonate  at  from  40°  to  50°.  It  is 
well  washed.  These  different  treatments  are  repeated  three  to  four  times  if  fraud  is 
intended. 

In  mordanting  boiled  silks  they  are  soaked  for  half  to  one  hour  in  a  cold  solution 
of  basic  ferric  sulphate  at  48°  Tw.,  the  excess  of  liquid  is  removed  by  pressing,  and 
the  silk  is  well  washed,  first  in  cold  and  then  in  lukewarm  water.  This  treatment  is 
repeated  seven  or  eight  times,  and  the  silk  is  then  put  into  an  old  soap-beck  at  100°, 
or  in  a  bath  of  panama-bark,  to  which  have  been  added  2  per  cent,  of  soda-crystals,  and 
oleicacid  soap  equal  to  about  12  per  cent,  of  the  weight  of  the  silk.  It  is  again  washed 
in  water  when  the  mordanting  process  is  completed.  Both  the  iron-  and  the  soap- 
beck  remain  continuously  in  use,  care  being  taken  to  keep  up  the  proper  concentration 
in  the  former  by  the  addition  of  fresh  mordant,  and  to  boil  up  a  fresh  quantity  of  soap 
in  the  latter  before  mordanting  so  that  the  iron-soap  which  has  been  formed  during 
former  operations  may  rise  to  the  surface  and  be  skimmed  off. 

In  raw  silks  where  a  relatively  weak  solution  of  ferric  sulphate  is  used,  the  gummy 
matter  of  the  silk  occasions  decomposition  and  precipitates  a  quantity  of  an  insoluble 
basic  salt  during  dipping.  The  washing  in  water  and  the  rinsing  in  solution  of 
sodium  carbonate  complete  the  decomposition  and  remove  the  acid  salts  which  have 
been  liberated.  In  silk  which  has  been  boiled  off  the  liquid  is  simply  absorbed  by  the 
fibre  whilst  being  dipped  into  the  concentrated  solution  of  the  mordant.  The  use  of 
water  containing  calcium  bicarbonate  is  advantageous  for  washing,  as  it  promotes  tho 
decomposition  of  the  mordants  which  have  been  absorbed.  Boiling  in  soap  lye  is 
necessary  to  complete  the  decomposition  of  the  mordants,  and  the  temperature  of  100° 
then  applied  modifies  the  precipitated  ferric  sulphate  so  that  it  is  less  easily  dissolved 
in  the  following  baths. 

Silk  is  destroyed  by  oxidation  if  it  is  allowed  to  lie  in  the  air  after  saturation  with 
ferric  oxide. 

Ferric  nitrosulphates,  so-called  nitrates  of  iron,  e.g. — 

6FeS04  +  8HN03  =  3^e2(S04)2(NOg)2  +  2NO  +  4H20 
i2FeS04  +  ioHN03  =  3Fe4(SO4)4(N03)2(OH)2  +  4NO  +  2H2O, 

are  used  chiefly  for  blacks  on  cotton.     Pure  ferric  nitrate,  ferric  acetate,  and  iron-alum 
are  little  used. 

Nickel  mordants,  according  to  Leichti,  may  be  recommended  for  producing  fast 
colours  in  light  shades.  For  dyeing  the  nickel-ammonium  chloride,  and  for  printing  the 
nickel  nitro-acetate,  are  to  be  recommended. 

Chrome  mordants  are  of  comparatively  recent  origin.  According  to  Liechti,  the 
quantity  of  the  chromium  oxide  deposited  upon  the  fibre  in  mordanting,  drying,  and 
ageing  increases  with  the  neutralisation,  as  with  the  aluminium  mordants ;  in  mor- 
dants of  the  same  acid,  of  the  same  degree  of  neutralisation  but  different  production, 
the  presence  of  foreign  salts  has  an  unfavourable  influence.  Alkaline  sulphates  espe- 
cially, under  circumstances  otherwise  the  same,  decrease  the  quantity  of  the  chromium 
oxide  retained  by  the  fibre,  and  must  be  considered  as  agents  which  retard  dissocia- 
tion. The  fixation  of  the  acetates  and  mixed  acetates  during  drying,  &c.,  is,  with  the 
exception  of  those  mordants  which  incline  to  spontaneous  decomposition,  to  be  referred 
alone  to  the  decomposing  influence  of  the  fibre,  as  in  the  absence  of  the  fibre  insoluble 
basic  salts  are  not  obtained  by  the  evaporation  of  acetic  acid.  The  strongly  basic 


SECT,  vii.]  DYEING  AND  TISSUE-PRINTING.  825 

sulphates,  Cr2(S04)2(OH)2,  Cr(SO)4(OH)6,  Cr2S04(OH)4,  &c.,  yield  the  largest  quantity 
of  chromium  oxide  to  the  fibre,  but  never  in  so  large  a  proportion  as  in  the  case  of 
certain  aluminium  products.  Kopp  recommends  chromium  fluoride. 

Chromium  chlorate  is  recommended  by  Lauber,  and  H.  Koechlin  proposes  a  mix- 
ture of  1 6  parts  solution  of  chromium  acetate  at  24°  T\v.,  48  parts  water,  32  parts  soda- 
lye  at  66°  Tw.,  and  i  part  glycerine.  After  mordanting,  the  goods  are  allowed  to  dry 
for  some  hours  and  are  then  washed.  The  more  caustic  the  solution  of  chrome  the  better 
it  acts ;  if  the  proportion  of  soda-lye  is  insufficient,  little  or  no  chromic  oxide  is  depos- 
ited on  the  fibre.  On  the  other  hand,  if  the  causticity  is  excessive  the  fibre  contracts 
strongly.  According  to  Schmidt,  this  phenomenon  always  takes  place,  and  in  modera- 
tion it  is  not  unwelcome,  since  it  strengthens  the  fibre  by  mercerisation.  Alkaline 
chrome  mordants  must  be  used  with  care,  as  they  may  produce  sores.  If  cotton  yarns 
are  mordanted  by  hand,  caoutchouc  gloves  should  be  used.  Instead  of  fixing  chromium 
oxide  by  letting  the  cloth  lie  for  some  time  rolled  up,  the  same  end  is  reached  in  a  very 
short  time  by  steaming.  Knecht  shows  that  the  quantity  of  chrome  deposited  upon 
wool  varies  with  the  concentration  of  the  solution.  If  we  take  the  quantity  of  chrome 
precipitated  upon  the  fibre  as  a  measure  for  the  efficiency  of  the  mordant,  chromic 
acid  is  by  far  the  best  chrome  mordant  for  wool.  Next  in  value  follows  potassium 
dichromate  along  with  sulphuric  acid,  then  the  dichromate  alone,  and,  lastly,  neutral 
potassium  chrom^te. 

Tin  Mordants.* — Stannous  chloride,  SnCl22H20,  called  salts  of  tin  or  tin  crystals, 
is  still  extensively  used  in  printing,  both  as  a  solid  and  in  solution.  Generally  the 
stannous  salts  are  more  serviceable  for  woollens  and  the  stannic  salts  for  cotton  goods. 
Sometimes  stannous  chloride  is  added  to  the  dye-bath  towards  the  end  of  the  dyeing 
process,  in  order  to  heighten  the  shade.  Stannic  chloride,  and  less  frequently  "  pink 
salt,"  SnCl4(NH4Cl)2,  as  well  as  sodium  stannate,  have  a  number  of  applications. 

Manganese  Mordants  (MnCl2  and  KMn04)  and  lead  mordants  are  little  used,  the 
affinity  of  lead  for  the  fibre  being  feeble.  Copper  mordants,  especially  the  nitrates, 
Cu(N03)2,  are  sometimes  used  on  account  of  their  oxidising  action — e.g.,  in  catechu 
colours. 

Antimony  Mordants  were  first  recommended  by  Brooks,  in  order  to  combine  tannin 
at  once  with  colouring  matter  and  with  a  metallic  oxide,  which  he  effected  with  tartar 
emetic,  K.SbO.C4H406.  The  action  of  all  antimonial  mordants  depends  on  the  fact 
that  antimony  oxide  deposits  on  the  fibre  as  an  antimonial  lake  in  conjunction  with 
tannin,  thus  fixing  the  colour  upon  the  fibre. 

On  account  of  the  high  price  of  tartar  emetic,  potassium-antimony  oxalate  has 
latterly  come  into  use.  Koehler  recommends  antimony  oxide  in  an  alkaline  solution  of 
glycerine  as  a  mordant  for  cotton  dyeing.  Antimonious  chloride  and  antimony  lac- 
tate  have  been  recommended.  Of  more  importance  is  the  antimony  sodium  fluoride, 
SbNaF4,  and  especially  ammonium  antimony  fluoride  sulphate,  SbF3(NH4)2S04. 

Tannin  Mordants. — For  colours  of  a  basic  character,  such  as  magenta,  malachite 
green,  &c.,  tannin  plays  the  part  of  a  mordant,  just  as  does  alumina  for  alizarine,  as  it 
combines  with  the  colourless  base  contained  in  these  colouring-matters  and  produces  an 
insoluble  lake.  During  the  precipitation  of  a  basic  colouring-matter  from  its  solution 
by  means  of  tannin,  the  acid  previously  combined  with  the  colour  base  is  liberated. 
J.  Koechlin  has  remarked  that  the  addition  to  the  mixture  of  an  alkali  like  sodium 
carbonate  makes  the  precipitation  easier  and  more  complete.  For  the  production  of  a 
tannin  lake  it  is,  according  to  Hummel,  not  necessary  that  the  tannic  acid  should  be 

*  The  importance  of  the  tin  mordants  has  greatly  declined  since  the  introduction  of  the  coal- 
tar  colours.  So  long  as  scarlets,  crimsons,  and  other  bright  colours  had  to  be  obtained  from 
cochineal,  lac  and  the  woods,  compounds  of  tin  were  used  in  a  multitude  of  modifications,  and 
much  skill  and  nicety  were  needed  in  their  preparation. — [EDITOR.] 


826 


CHEMICAL  TECHNOLOGY. 


[SECT.  vii. 


in  a  free  state.  Insoluble  metallic  tannates  have  as  great,  if  not  a  greater,  affinity  for 
basic  colouring-matter.  The  presence  of  the  metallic  oxido  facilitates  the  decomposi- 
tion, because  it  neutralises  a  part  of  the  liberated  acid  of  the  colouring-matter,  and 
there  is  probably  formed  an  insoluble  bibasic  compound  (antimony  and  colour-base 
tannate).  But  the  use  of  insoluble  metallic  salts  prevents  the  lake  formed  upon  the 
fibre  from  re-dissolving,  either  on  account  of  an  excess  of  tannin  or  of  colouring 
matter.  An  excess  of  tannin  yields  soluble  compounds  with  basic  colouring-matters, 
so  that  the  exact  amount  of  tannin  needful  must  first  be  deposited  upon  the  fibre  and 
then  the  colouring-matter. 

Tannin  forms  insoluble  compounds  with  alumina  and  the  iron,  tin,  and  antimony 
oxides.  These  bases  act  as  mordants  for  colouring-matters  of  an  acid  character, 
whether  they  occur  as  hydrates  or  in  combination  with  tannic  acid  or  other  acids, 
such  as  the  phosphoric,  arsenic  acids,  &c.  They  have  still  the  power  to  attract  such 
colouring-matters,  and  to  form  with  them  coloured  lakes.  For  this  reason  tannin  is 
often  used  as  a  precipitant  or  fixing  agent  for  aluminous,  tin,  or  iron  mordants. 

The  tannin  compounds  obtained  with  the  iron  mordants  have  a  bluish  black  colour, 
of  sufficient  intensity  to  serve  as  a  grey  or  even  as  a  black  dye.  In  this  respect  tannin 
may  be  regarded  as  a  coloming-matter  in  the  same  manner  as  alizarine.  In  many 
cases  the  blue-black  iron  tannate  serves  merely  to  darken  certain  colours,  which  is 
effected  by  means  of  preparations  specially  applied.  In  such  cases  the  iron  tannate 
acts  at  once  as  a  mordant  and  a  ground  colour. 

Cotton  is  worked,  or  steeped  in  a  solution  of  tannin,  and  the  excess  of  liquid  is 
removed  by  draining  or  nipping,  sometimes  followed  by  drying.  In  padding,  the 
cotton  is  saturated  with  the  solution  for  a  few  seconds,  and  is  then  wrung  out  and 
dried.  In  this  case  the  solution  employed  must  contain  at  least  ten  times  as  much 
tannin  as  the  former  process,  if  it  is  to  be  equally  effective.  ' 

If  textile  fabrics  soaked  in  oil — especially  castor-oil  or  olive-oil — are  exposed  to  the 
air,  the  oil  is  partially  decomposed,  and  the  free  fatty  acid  forms  insoluble  soaps  with 
the  aluminous  mordants.  Especially  important  is  the  turkey-red  oil  obtained  by 
treating  these  oils  with  sulphuric  acid,  on  the  composition  of  which  there  is  still  a 
variety  of  opinions.  Its  chief  constituent  is  probably  (according  to  Benedikt)  sul- 
phoricinoleic  acid,  C^Hj^.OSOjH.  It  is  used  in  turkey-red  dyeing,  and  in  fixing 
aniline  colours  upon  the  fibre. 

The  rancid  smell  of  tissues  mordanted  with  oil  is  unpleasant. 

Albumen  and  casein  (dissolved  in  ammonia  or  borax)  and  gelatine  are  used  in  tissue 
printing. 

Apparatus. — Of  the  recent  apparatus  used  in  dye-works  the  following  may  be 
mentioned : — 

Colour -pans  for  Laboratories  are  heated  by  steam,  according  to  Dawson's  design. 
In  a  strong  cast-iron  tray,  M  (Figs.  563  and  564),  fixed  in  a  frame  so  as  to  admit  of 


Fig. 


Fig.  564. 


turning,  the  cast-iron  pans,  D,  are  fixed  steam-tight  by  means  of  screws.   The  pans,  Z>, 
receive  water  used  for  a  water-bath,  or  preferably  in  its  place  glycerine,  into  which  the 


SECT.   VII.] 


DYEING  AND   TISSUE-PRINTING. 


827 


Fig.  565. 


copper  dye-pan,  E,  is  fitted  and  secured  by  the  brass  ring,  A',  and  the  caoutchouc  rings,  r. 
The  lower  ring  prevents  the  escape  of  annoying  vapour?  from  the  liquid  bath.  Into  the 
tray,  M,  steam  of  about  4  centimetres  is  admitted  at  one  side  through  the  revolving 
plug,  whilst  the  condensed  water  escapes  from  the  lowest  point  of  the  tray  by  a 
vertical  channel.  Handles,  H,  allow 
the  entire  series  of  pans  to  be  emptied 
by  turning  the  tray,  M.  To  prevent 
felting,  loose  wool  and  cotton  are 
exposed  to  the  rotating  liquid  in  a 
compressed  state. 

For  bleaching  and  dyeing  cops 
0.  Fisher  recommends  a  centrifugal 

O 

machine.  Into  the  internal  sieve,  A 
(Figs.  565  and  566),  there  extend 
the  two  tubes,  Z>,  fed  in  common  by 
one  conductor,  and  both  having  a 
slit,  through  which  the  liquid  issues 
uniformly,  in  its  entire  height.  In 
order  to  cleanse  the  slits  there  are 
small  slides,  m,  fixed  to  the  rods,  E, 
and  dirt  may  thereby  be  expelled 
from  the  machine  even  while  it  is 
at  work.  The  tubes,  I),  are  also 
closed  below  with  nuts  provided  with 
holes,  so  that  dirt  cannot  accumulate 
or  can  be  easily  removed  by  un- 
screwing the  nuts. 

For  the  uniform  saturation  of 
the  yarns  with  dye  liquor,  mordants, 
or  dressing,  &c.,  there  are  used, 
especially  in  indigo  and  turkey-red 
dyeing,  so-called  passing-machines, 

Fig.  567. 


Fig.  566. 


the  general  arrangement  of  which  is  shown  in  Fig.  567.  First  the  roller  A,  fixed 
perpendicularly  on  the  axle  //,  is  pushed  up  to  roller  B,  so  that  a  workman  can  easily 
hang  the  yarns  over  A  and  B.  The  nipping  roller,  C,  fixed  on  the  weighted  lever,  Z>, 


828 


CHEMICAL  TECHNOLOGY. 


[SECT.  vn. 


presses  against  the  roller,  B,  the  lever,  E,  which  stands  above  the  roller,  J3,  falls  down 
into  the  position  shown,  and  draws  the  yarns  into  the  bath  in  the  cistern,  F ;  so  that 
when  the  roller,  B,  is  turned,  they  are  carried  along  through  the  beck.  After  a 
certain  time  the  yarns  are  stretched,  the  axle,  H,  being  brought  back  by  the  weight, 
C ;  the  roller,  (7,  and  the  lever,  //,  return  to  their  original  position,  and  the  axle,  H, 
revolves,  whereby  the  yarns  are  wrung  out.  The  axle,  //,  then  in  turning  back  wrings 
the  yarns  again,  the  roller,  B,  makes  a  rotation,  and  the  axle,  H,  wrings  the  yarns 
again  by  moving  forwards.  This  is  twice  repeated,  so  that  the  parts  which  lie  over 
the  rollers  may  be  uniformly  wrung  out.  The  weight,  G,  is  then  lifted  off,  and  the 
machine  stands  still  to  allow  the  dyed  hanks  to  be  taken  off,  and  fresh  ones  to  be  put 
in  their  place.  The  introduction  of  these  various  movements  is  effected  by  curved 
discs  from  the  shaft,  M. 

The  machine  for  dyeing  piece-goods  and  yarns,  made  by  the  Zittau  Machine  Works, 
consists  of  a  trough  for  the  flot  (Figs.  568-571),  over  which  there  are  several  reels,  B, 
movable  alternately  from  the  r.ight  to  the  left,  and  reversely  over  the  entire  length  of 
the  trough,  or  a  portion  of  it,  and  keeping  all  the  time  in  rotation.  By  this  slow  to 
and  fro  and  alternately  turning  movement  of  the  reels  the  pieces  to  be  dyed  are  moved 

Fig.  568. 


in  such  a  manner  that  the  pieces  are  always  conveyed  from  one  half  of  the  trough  to 
the  other  in  quite  even  folds,  and  are  thus  brought  in  uniform  contact  with  the  dye 
liquor,  and  it  is  rendered  possible  to  dye  up  any  given  quantity  of  goods  at  once  in  one 
and  the  same  flot,  or  in  several  flots  in  succession.  Fig.  568  shows  the  machine  in 
elevation,  and  Fig.  569  gives  a  side  view,  with  a  smooth  drum,  and  with  an  undivided 
trough  as  used  for  dyeing  piece-goods,  spread  out.  Fig.  570  shows  the  elevation,  and 
Fig.  571  the  side  view  of  the  machine,  with  two  compartments  provided  with  reels,  and 
with  a  trough  divided  into  two  compartments  in  length  and  four  in  breadth,  as  applied 
for  yarns  in  warps  (French,  chaines ;  German,  Ketten],  and  for  pieces  folded  up.  In 
both  cases  the  reels  are  placed  capable  of  rotation  on  rolling  trucks,  b,  which  run  on 
horizontal  rails,  J),  fixed  to  the  supports,  C,  Cir  The  movement  of  these  trucks  to  and 


SECT.   VII.] 


DYEING  AND  TISSUE-PRINTING. 


829 


fro,  and  the  alterna  tin  rotatory  movement  of  the  reels,  B,  is  effected  by  the  endless 
band,  S"  S",  which  in  turn  is  moved  by  the  screw  wheels,  V,  V,,,  or  the  band  discs, 
g'  g",  fixed  on  the  shafts  of  the  screw  wheels.  The  screw-wheel  shafts,  V,  V, „  are 
connected  by  the  wheels,  R/  B./;,  with  a  corresponding  number  of  teeth,  according  as 
the  open  band,  ?•',  or  the  cross  band,  r",  runs  upon  the  middle  disc,  c,  whilst  each 

Fig-  57i- 


time  the  other  band  runs  upon  one  of  the  discs  d.     The  change  effected  thereby  is 
that  the  rail,  K,  is  pushed  to  the  left  or  to  the  right  by  the  impact  of  the  truck,  b. 

In  Sulzer's  yarn-dyeing  machine  the  yarns  are  exposed  to  a  current  of  hot 
air  alternately  in  a  freely  suspended  and  in  a  horizontal  position,  and  arrive  pro- 
gressively at  higher  temperatures  as 
the  dyeing  proceeds.  The  hanks  of 
yarn  are  suspended  on  rods  at  e, 
which,  as  appears  from  Fig.  572, 
are  laid  in  endless  chains  moving 
backwards  and  forwards.  Similar 
is  the  yarn-dyeing  machine  con- 
structed by  the  Hartmann  Machine 
Works  at  Chemnitz.  The  difference 
between  the  Sulzer  and  the  Hart- 
mann machine  lies  in  the  manage- 
ment of  the  chains  and  the  arrange- 
ment of  the  system  of  hot-air  pipes. 
The  temperature  of  the  current  of 
air,  which  is  60°  above,  falls  to  30° 
at  the  exit  from  the  machine.  A 
drying  machine  5  metres  in  length, 
3 1  metres  wide,  and  4  metres  high, 
dries  in  eleven  hours  1300  to  1400 
kilos,  of  yarn,  and  requires  about 
4  horse-power. 

Dyeing  Woollens. — Wool  is  dyed 
either  loose  or  spun  into  yarns,  or 

after    weaving   as    cloth.      As    in  M  ^        I  \  ( 

working  up  the  wool  a  certain  part 
is  always  lost  in  the  mechanical  operations,  piece-dyeing  is  the  most  advantageous.* 

Blue  Dyeing. — The  imparting  of  a  blue  colour  to  wool  is  one  of  the  most  important 

*  On  the  other  hand,  it  is  the  most  difficult.  Any  unevenness  in  dyed  wool  or  yarn  is  lost  after- 
wards, but  a  spot  on  a  woven  piece  is  a  permanent  defect.  If  the  colour  to  be  produced  is 
required  to  be  fast,  the  cloths  are  often  prepared  by  boiling  in  solutions  of  alum  and  tartar,  of 
copperas  and  tartar,  or  of  tartar  and  stannic  chloride,  or  pink  salt.  All  processes  which  involve  the 
use  of  tartar  (argol)  are  expensive,  and  it  is  therefore  dispensed  with  whenever  possible.— [EDITOE.] 


830  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

operations  of  dyeing  woollen  goods.  It  is  frequently  effected  with  indigo,  which 
produces  the  most  beautiful  and  fast  colours ;  but  indigo  is  used  only  for  the  better 
and  heavier  kinds  of  woollen  fabrics ;  lighter  tissues — merinos,  for  instance — are  often 
dyed  with  Prussian  blue  (not  a  fast  colour),  while  common  woollen  goods,  flannels,  <fec., 
if  dyed  blue  at  all,  are  dyed  with  logwood  and  blue  vitriol  (copper  sulphate).  In 
order  to  ascertain  whether  a  woollen  tissue  has  been  dyed  with  indigo,  Prussian  blue, 
or  copper  salts,  the  following  tests  may  be  employed.  Woollen  tissue  dyed  with 
indigo  does  not  change  its  colour  by  being  boiled  with  caustic  potash,  or  by  being 
moistened  with  concentrated  sulphuric  acid.  When  Prussian  blue  is  the  dye  used, 
the  tissue  becomes  red-coloured  by  being  boiled  with  caustic  potash,  and  becomes 
discoloured  by  being  moistened  with  strong  sulphuric  acid.  Woollen  goods  dyed  with 
logwood  and  copper  salts  are  reddened  by  being  moistened  with  dilute  sulphuric  acid, 
and,  on  being  incinerated,  the  tissue  leaves  an  ash  containing  copper. 

Indigo  Blue. — Woollen  goods  are  most  frequently  dyed  blue  with  indigo  by  means 
of  a  solution  of  white  indigo  (reduced  indigo)  in  an  alkaline  fluid,  the  goods  being 
blued  by  exposure  to  air — that  is  to  say,  by  the  oxidation  of  the  indigo  taken  up  by 
the  fibre,  the  dye  becoming  simultaneously  fixed.  The  principle  of  this  mode  of  dyeing 
with  indigo  (technically  known  as  blue  vat)  may  be  elucidated  by  the  following 
formula :— C16H12N20,  +  0  =  C16H10N202  +  H20. 

Blue  Vats. — The  greatest  consumption  of  indigo  is  in  forming  the  blue  vats,  in 
which  woollen  or  cotton  goods,  more  rarely  linen,  are  dyed  by  simply  immersing  them 
in  the  solution  of  white  indigo.  The  same  vats  are  not  equally  adapted  for  wool  and 
calico,  there  being,  as  will  be  seen  in  the  following  details,  a  wide  difference  in  their 
composition.  According  to  the  general  accounts,  the  lime  and  copperas  vat  (see  below) 
is  not  well  adapted  for  woollen  goods;  still,  in  the  most  recently  published  French 
treatise  on  woollen  dyeing  there  is  no  mention  made  of  any  other  kind  of  vat ;  the 
following  proportions  and  directions  being  given  for  setting  a  vat  for  dark  blue : — 
1 200  gallons  of  water;  34  Ibs.  of  quicklime;  22  Ibs.  of  green  copperas;  12  Ibs.  of 
ground  indigo ;  4  quarts  of  caustic  potash  solution  at  34°  =  sp.  gr.  i'288.  The  indigo 
is  ground  very  fine  by  trituration  in  properly  constructed  mills,  this  being  a  point  of 
the  utmost  importance.  In  the  above  recipe  the  potash  is  mixed  with  5  gallons  of 
water  in  an  iron  pan,  and  the  indigo  added.  The  mixture  is  gradually  heated  to 
ebullition  and  kept  boiling  for  two  hours  with  uninterrupted  stirring ;  this  softens  and 
prepares  the  indigo  for  dissolving.  The  lime  is  well  slacked  so  as  to  be  very  fine,  and  is 
next  passed  through  a  sieve  in  the  state  of  milk  of  lime.  It  is  then  mixed  with  the 
indigo  and  potash ;  the  copperas  (ferrous  sulphate),  previously  dissolved,  is  added  to 
the  vat  and  well  stirred ;  then  the  mixture  of  lime,  potash,  and  indigo  is  poured  in, 
and  the  whole  well  stirred  for  half  an  hour.  If  the  proportions  are  well  kept,  the  vat 
will  be  fit  for  working  in  twelve  hours ;  if,  however,  it  looks  blue  under  the  scum,  it  is 
a  sign  that  the  indigo  is  not  wholly  dissolved,  and  more  lime  and  copperas  should  be 
added,  and  the  vat  left  undisturbed  for  another  twelve  hours.  The  vat  is  worked  at  a 
temperature  of  70°  to  80°  F.  This  is  the  ordinary  composition  of  a  vat  for  dyeing 
cotton,  but  is  not,  at  least  in  England,  in  use  for  dyeing  woollen  goods. 

The  usual  blue  vats  for  wool  contain  neither  copperas  nor  lime,  or  but  a  small 
quantity  of  the  latter ;  as,  for  instance — Water,  500  gallons ;  indigo,  20  Ibs. ;  potash 
(carbonate,  pearl-ash),  30  Ibs. ;  bran,  9  Ibs. ;  madder,  9  Ibs.  The  water  is  heated  to 
just  below  its  boiling-point ;  the  potash,  bran,  and  madder  are  first  put  into  the  vat,  a 
well-made  wooden  tub  of  convenient  size,  and  then  the  indigo,  previously  very  finely 
ground.  Cold  water  is  added  so  as  to  reduce  the  temperature  to  90°  F.,  and  that 
temperature  is  maintained  constant  by  means  of  a  steam-pipe.  The  ingredients  are 
well  stirred  every  twelve  hours.  The  vat  is  generally  ready  for  use  in  forty-eight  hours 
after  setting.  This  vat  does  not  work  longer  than  about  a  month,  and  is  somewhat 


SECT,  vii.]  DYEING  AND   TISSUE-PRINTING.  831 

expensive  on  account  of  the  potash.  Another — the  so-called  German — vat  is  much 
more  manageable,  and  may  be  worked  for  two  years  without  emptying,  being  freshened 
up  as  required.  It  is  composed  of  the  following  ingredients  : — 2000  gallons  of  water 
are  heated  to  130°  1\,  and  there  are  added  20  Ibs.  of  crystals  of  soda  (common 
carbonate);  z\  pecks  of  bran;  and  12  Ibs.  of  indigo,  the  mixture  being  well  stirred. 
In  twelve  hours  fermentation  sets  in ;  bubbles  of  gas  rise ;  the  liquid  has  a  sweet  smell, 
and  has  assumed  a  green  colour ;  2  Ibs.  of  slaked  lime  are  now  added  and  well  stirred, 
the  vat  is  again  heated  and  covered  up  for  twelve  hours,  when  a  similar  quantity  of 
bran,  indigo,  and  soda,  with  some  lime,  is  added.  In  about  forty-eight  hours  the  vat 
may  be  worked ;  but  as  the  reducing  powers  of  the  bran  are  somewhat  feeble,  an 
addition  of  6  Ibs.  of  molasses  is  made.  If  the  fermentation  becomes  too  active,  it  is 
repressed  by  the  addition  of  lime ;  if  too  sluggish,  it  is  stimulated  by  the  addition  of 
bran  and  molasses.  Like  all  the  other  blue  vats  for  wool,  it  is  worked  hot.  Another 
kind  of  vat  may  be  called  the  woad  vat,  because  a  considerable  quantity  of  woad  is  added 
to  it,  and  also  madder,  which  in  this  case  acts  simply  by  reason  of  the  saccharine  matter 
it  contains.  The  proportions  are :  —Pulverised  indigo,  i  Ib. ;  madder,  4  Ibs. ;  slaked 
lime,  7  Ibs.,  boiled  together  with  water  and  poured  upon  the  woad  in  the  vat.  After 
a  few  hours  fermentation  sets  in,  and  fresh  indigo  is  added  according  to  the  depth  of 
colour  required  to  be  dyed.  The  pastel  vat  is  set  with  a  variety  of  woad  which  grows 
in  France,  and  which  is  richer  in  colouring  matter  than  the  common  woad.  It  is 
possible  that  the  colouring  matter  of  the  pastel  adds  to  the  effect ;  but  it  is  more  likely 
that,  while  it  furnishes  fermentiscible  matters  useful  in  promoting  the  solution  of 
indigo,  it  is  added  as  a  remnant  of  ancient  usage.  Before  indigo  became  again  known 
in  Europe  (the  dye  was  known  to  the  Greeks  and  Romans)  in  the  seventeenth  century, 
woad  was  the  general  blue  dye  material.  The  method  of  dyeing  the  woollen  fibre  and 
fabrics  is  very  simple.  The  wool,  thoroughly  wetted  out,  is  suspended  on  frames,  and 
dipped  in  the  vat  for  an  hour  and  a  half  or  two  hours,  being  agitated  all  the  time  to 
insure  regularity  of  colouring.  The  pieces  are  then  removed,  washed  in  water,  and 
treated  with  weak  hydrochloric  or  sulphuric  acid  to  remove  the  alkali  retained.  As 
regards  blue  vat  for  cotton  dyeing,  in  some  exceptional  cases,  when  thick  and  heavy 
goods  have  to  be  dyed,  the  so-called  German  vat  is  used ;  but  generally  all  calicoes  are 
dyed  blue  by  means  of  the  cold  lime  and  copperas  vat.  The  materials  used  are  lime, 
ferrous  sulphate,  ground  indigo,  and  water.  The  chemical  action  consists,  in  the 
first  instance,  in  the  formation  of  calcium  sulphate  and  ferrous  oxide;  the  latter 
substance,  having  a  considerable  affinity  for  oxygen,  removes  an  atom  of  it  from  the 
blue  indigo,  converting  it  into  white,  which  dissolves  in  the  excess  of  lime,  and  is 
ready  for  dyeing.  The  proportions  are  as  follows: — 900  gallons  of  water,  60  Ibs. 
of  green  copperas,  36  Ibs.  of  ground  indigo,  and  80  to  90  Ibs.  of  slaked  lime.  These 
are  stirred  up  together  every  half-hour  for  three  or  four  hours,  then  left  twelve 
hours  to  settle,  well  raked  up  again,  and  as  soon  as  the  vat  has  subsided  it  is  ready 
for  dyeing. 

The  urine  vat  is  set  up  by  dissolving  indigo  in  stale  urine  (lant).  The  indigo  is 
reduced  by  the  organic  matters  of  the  putrescent  urine,  and  the  indigo- white  thus 
obtained  dissolves  in  the  ammonium  carbonate  produced  at  the  same  time.  This  vat 
is  difficult  to  manage,  and  is  rarely  used  either  for  wool  or  cotton. 

The  hydrosulphurous  vat  (of  Schutzenberger)  is  set  up  by  bringing  a  concentrated 
solution  of  sodium  bisulphite  in  contact  with  zinc  powder.  The  zinc  dissolves  without 
any  escape  of  hydrogen,  and  a  hyposulphite  is  formed:  S02  +  Zn  =  ZnSO2.  The  zinc 
oxide  is  eliminated  by  an  addition  of  milk  of  lime.  This  liquid  is  filtered  with  exclusion 
of  air  and  mixed  with  ground  indigo  and  soda  or  hydrate  of  lime,  when  a  solution  of 
indigo-white  is  quickly  obtained.  This  vat  is  suitable  either  for  animal  or  vegetable 
fibres,  and  is  less  liable  to  "  diseases  "  than  the  fermentation  vats. 


832  CHEMICAL  TECHNOLOGY.  [SECT.  vir. 

The  arsenical  or  orpiment  vat  is  more  used  in  tissue-printing  than  in  dyeing  blue  on 
woollens.  It  is  set  by  dissolving  orpiment  (AssS3}  and  indigo  in  potassa-lye,  and  the 
solution  is  thickened  with  gum  and  printed. 

In  the  tin  vat,  indigo  is  brought  in  contact  with  a  solution  of  stannous  oxide  in 
caustic  potassa,  or  caustic  soda  is  boiled  with  indigo  and  metallic  tin.  There  is  a 
formation  of  indigo-white  and  an  alkaline  stannate.  This  vat  is  chiefly  used  in 
tissue-printing. 

Saxony  Blue. — As  already  stated,  indigo  dissolves  in  concentrated  sulphuric  acid, 
forming  (because  it  is  not  a  solution  in  the  ordinary  sense  of  the  word)  sulphindigotic 
acid,  which  is  employed  in  dyeing  wool  in  the  following  manner : — First,  i  part  of  in- 
digo is  treated  with  4  to  5  parts  of  fuming  sulphuric  acid  ;  next,  this  solution  is  poured 
into  a  vessel  containing  water ;  and  into  this  mixture  flock  wool  is  immersed  for  twenty- 
four  hours.  After  this  time  the  wool  is  removed  from  the  vessel  and  drained,  and 
transferred  to  a  cauldron  filled  with  water,  to  which  has  been  added  either  carbonate 
of  ammonia,  or  of  soda,  or  of  potash,  and  boiled  for  some  time.  The  solution  thus 
obtained,  technically  known  as  extract  of  indigo  or  as  indigo  carmine,  is  used  for  dyeing 
wool  which  has  been  previously  mordanted  with  alum.  There  is  formed  on  the  wool 
aluminium  sulphindigotate. 

Recovery  of  Indigofrom  Rags. — In  order  to  recover  the  indigo  from  scraps  and  rags 
of  woollen  and  other  fabrics  dyed  indigo  blue,  the  materials  are  treated  with  dilute  sul- 
phuric acid,  which  is  heated  to  100°.  The  wool  is  dissolved,  while  the  indigo  is  left  as 
an  insoluble  sediment.  Military  uniforms  yield  from  2  to  3  per  cent,  of  indigo.  The 
acid  solution  is  next  neutralised  with  chalk,  and  a  calcium  sulphate  is  obtained 
which,  owing  to  the  nitrogenous  matter  intermingled,  may  be  usefully  employed  as  a 
manure. 

Berlin  Blue,  Royal  Blue.* — Wool  is  dyed  with  the  so-called  Prussian  blue  (iron 
ferrocyanide)  by  two  methods,  one  of  which  consists  in  saturating  the  wool  with  a 
solution  of  a  ferric  salt  (generally  the  persulphate,  or  preferably  the  pernitrate),  after 
which  the  wool  is  passed  through  a  solution  of  potassium  ferrocyanide  in  water, 
acidulated  with  sulphuric  acid.  The  other  process,  producing  the  so-called  Bleu 
de  France,  is  based  upon  the  decomposing  action  which  the  atmosphere  exerts  on  the 
ferro-  and  ferricyanhydric  acids.  The  goods  are  immersed  in  a  solution  of  either  the 
ferro-  (yellow)  or  ferri-  (ruby-red)  potassium  cyanide  (commonly  called  yellow  or  red 
prussiate)  in  water,  to  which  are  added  sulphuric  acid  and  alum.  Afterwards  the 
goods  are  aged,  or  exposed  to  the  air  in  rooms  in  which  steam  is  simultaneously  ad- 
mitted to  elevate  the  temperature  and  assist  the  action  of  the  oxygen  of  the  air.  The 
result  is  that  the  ferro-  or  ferricyanhydric  acid  is  decomposed,  hydrocyanic  acid  being 
evolved,  while  there  is  deposited  on  the  fibres  of  the  woven  fabric  iron  ferrocyanide, 
Prussian  or  Berlin  blue.  MeitzendorfF  has  proposed  a  method  of  dyeing  this  blue  by 
which  a  colour  is  produced  very  similar  to  that  obtained  by  the  so-called  Saxony 
blue.  He  prepares  a  solution  containing  potassium  ferrocyanide,  stannic  chloride 
(SnCl4),  tartaric  and  oxalic  acids ;  this  solution  is  heated,  and  the  wool  kept  therein  for 
some  time.  The  oxalic  acid  dissolves  the  Prussian  blue,  which  of  course  can  only  act 

*  This  colour  is  called  in  Germany  "  kali  blue,"  which  is  confusing,  as  the  name  "  alkali  blue  " 
is  there  given  to  Nicholson  blue.  The  first  method  given  above  for  producing  Berlin  blue  on  wool 
is  not  satisfactory.  The  best  royal  blue,  on  36  Ibs.  wool,  is  obtained  as  follows : — Mix  4  Ibs. 
potassium  ferrocyanide  and  6  Ibs.  oxalic  acid ;  dissolve,  enter  wool  at  ico°  F. ,  and  work  well  for 
two  hours,  raising  heat  gradually  to  180°  F. ;  take  out,  and  cool.  Cool  liquor  with  2  pails  cold 
water  ;  add  21  Ibs.  alum,  and  work  for  half  an  hour.  Add  f  pint "  yellow  spirit,"  and  work  for  one 
hour,  raising  heat  to  180°  F.,  at  which  heat  work  for  an  hour  and  a  quarter  longer.  Take  out,  and 
add  i  to  2  pints  nitrate  of  iron,  according  to  shade  required.  Enter  wool,  and  give  five  or  six 
turns.  Take  out,  cool,  and  wash  very  well.  This  is  an  expensive  colour,  and  is  generally  super- 
seded by  aniline  blues. — [EDITOK.] 


SECT,  vii.]  DYEING  AND  TISSUE-PRINTING.  833 

as  a  dye  when  dissolved,  any  of  it  left  undissolved  being  lost.  The  tartaric  acid 
increases  the  brilliancy  of  the  colour. 

Logwood  and  Copperas  Blues. — For  this  purpose  logwood  is  boiled  in  the  dye-beck 
with  water,  and  to  the  decoction  are  added  alum,  cream  of  tartar,  and  copper 
sulphate.  The  wool  is  boiled  in  this  fluid,  and  is  next  cleared  by  being  boiled  in  a  fluid 
containing  logwood,  tin  salt  (stannous  chloride),  alum,  and  cream  of  tartar.  The 
goods  dyed  in  this  manner  do  not,  as  is  the  case  with  the  indigo  goods,  become  white 
by  wear.  Instead  of  logwood,  archil  and  cudbear  are  frequently  used  for  so-called 
half-fast  colours. 

In  dyeing  blues  on  wool  with  coal-tar  colours  the  chief  dyes  employed  are  Nicholson 
blue  and  methylene  blue ;  blue-blacks  are  obtained  with  the  indulines. 

For  dyeing  with  indophenol  wool,  silk,  or  cotton  mordanted  for  turkey-red,  the 
following  mixture  is  prepared  : — 10  litres  acetic  acid,  10  litres  tin  acetate,  2  kilos,  indo- 
phenol, 5  litres  calcium  acetate  at  27°  Tw.,  and  i  litre  black  liquor  at  14°  Tw.  The 
whole  is  heated  to  effect  reduction,  and  poured  into  500  litres  of  water.  The  pieces  are 
worked  in  this  flot  at  60°  for  two  hours,  washed  and  oxidised  with  bichromate.  If  the 
wool  has  been  slightly  chlorised,  it  dyes  up  more  readily  and  gives  a  deeper  blue,  which 
.bears  soaping  at  a  boil  much  better.  According  to  Rosenstiehl's  proposal  the  wool  may 
be  dyed  in  an  alkaline  bath.  It  is  plunged  at  50°  for  two  minutes  into  i  litre  water, 
200  grammes  soda  crystals,  25  grammes  indophenol,  and  the  same  weight  of  glucose; 
it  is  then  exposed  to  the  air  for  some  minutes,  and  the  blue  is  fully  developed  by 
chroming. 

For  dyeing  with  alizarine  blue  (S),  which  in  many  cases  threatens  to  supersede 
indigo,  the  wool  is  mordanted  with  chrome  by  boiling  with  3  kilos,  potassium  bichro- 
mate and  2 \  kilos,  argol  to  100  kilos,  wool.  For  light  shades  it  is  sufficient  to  boil  for 
one  hour  with  2  per  cent,  potassium  bichromate  and  i  per  cent,  argol.  If  the 
water  contains  lime  it  must  be  corrected  with  acetic  acid.  The  wool  is  well  turned  in 
the  dye-beck  until  the  liquid  is  clear.  The  process  must  be  continued  at  a  boil  until 
the  colour,  which  at  first  appeared  reddish,  takes  a  pure  blue  tone. 

Dyeing  Yellows. — On  the  Continent,  weld,  which  has  become  quite  obsolete  for 
dyeing  yellow  on  wool  in  the  United  Kingdom,  having  been  entirely  superseded  by 
quercitron  bark,  is  still  used  for  producing  a  yellow  dye,  on  account  of  the  fact  that 
weld,  when  brought  into  contact  with  an  alkali,  becomes  less  red-coloured  than  do  the 
other  yellow  dyes. 

In  dyeing  with  weld  its  colouring-matter  is  extracted  by  water,  and  the  decoction 
added  to  the  goods  intended  to  be  dyed.  With  alum  it  dyes  a  very  fine  clear  yellow, 
tolerably  permanent  in  soap,  but  not  resisting  air  and  light.  Weld  has  not  more  than 
one-fourth  the  tinctorial  power  of  quercitron  bark,  and  on  this  account,  as  well  as  ou 
that  of  its  great  bulk  relative  to  its  weight,  it  is  not  used  in  this  country.  Fustic, 
yellow-wood,  is  very  extensively  employed  in  dyeing,  and  is  the  most  suitable  yellow 
matter  for  working  with  other  colours  in  compound  shades.  With  aluminous  mordants 
it  gives  yellow  of  an  orange  shade;  with  iron  mordants  it  gives  drabs,  greys,  and 
olives.  As  a  yellow  colouring-matter  it  is  considered  to  be  weight  for  weight  of  far  less 
power  than  quercitron  bark,  while  it  is  also  inferior  in  purity  of  colour ;  but  as  fustic 
withstands  the  action  of  acids  and  acid  salts  better  than  bark,  it  is  used  in  greens, 
bkcks,  and  mixed  colours  where  yellow  is  required.  Young  or  French  fustic  (also 
known  as  Venice  sumac  or  f ustet)  is  used  for  imparting  yellow  to  merinos.  A  golden 
yellow  is  produced  upon  wool  with  either  picric  acid  or  Manchester  yellow. 

Martius's  yellow,  Victoria  orange,  aurantia,  chrysoidine,  tropaeoline,  &c.,  have  to  a 
great  extent  superseded  the  vegetable  yellows. 

Eed  Dyeing.— Cochineal  and  lac  are  the  chief  colouring  matters  used  for  giving  wools 
a  red  or  scarlet  colour.  The  goods  are  prepared  by  boiling  in  a  bath  of  cochineal,  tartar, 

3  G 


834  CHEMICAL  TECHNOLOGY.  [SECT,  vii, 

and  tin  crystals  or  scarlet  spirit,  and  finished  with  cochineal  and  scarlet  finishing  spirit, 
a  stannous  chloride  to  which  much  oxalic  acid  has  been  added.*  For  crimsons  a  part  or 
the  whole  of  the  cochineal  used  must  be  previously  prepared  with  ammonia.  The 
water  used  should  be  pure  and  soft,  and  especially  free  from  even  the  least  trace  of  iron. 

Faster,  though  less  brilliant,  reds  are  obtained  with  madder,  or  latterly  with  aliza- 
rine. The  goods  are  prepared  by  boiling  with  alum  and  tartar,  and  then  dyed  with 
alizarine. 

The  redder  azo-colours  have  very  much  interfered  with  the  use  of  cochineal. 

Roccelline,  a  colour  obtained  bydiazotising  naphthylaminesulpho  acid  and  conjugat- 
ing with  £-naphthol,  has  to  a  great  extent  displaced  orchil,  and  in  some  cases  it  is  even 
used  in  place  of  cochineal  and  madder.  It  is  very  extensively  employed  for  silk-dyeing, 
which  is  done  in  a  curdled  soap-beck,  the  colour  being  afterwards  raised  with  sulphuric 
acid.  For  wool-dyeing  Roussel  acidifies  the  beck  slightly  with  hydrochloric  acid,  heats  to 
50°,  and  lets  the  wool  steep  for  from  fifteen  to  thirty  minutes.  The  roccelline  is  gradually 
added,  and  the  temperature  is  then  gradually  raised  to  90°,  at  which  point  it  is  allowed 
to  remain  for  half  an  hour.  By  the  addition  of  chrysoine  a  colour  is  obtained  which 
may  be  substituted  for  madder-reds.  Other  tones  are  produced  by  mixtures  of  roccelline 
with  extract  of  indigo,  chrysoine  orange,  naphthol  yellow,  &c.  The  extract  of  indigo 
is  added  towards  the  end  of  the  process,  along  with  sulphuric  acid  and  Glauber's  salt. 
These  colours  prove,  on  exposure  to  air,  almost  as  fast  as  cochineal,  and  more  permanent 
than  orchil.  Their  tone  is  also  unaffected  by  acids  and  alkalies.  The  production  of 
roccelline  shades  is  cheaper  by  80  per  cent,  than  those  produced  with  cochineal,  and  by 
40  per  cent,  than  those  obtained  with  orchil. 

Green  Dyeing. — Green  dyes  are  usually  obtained  by  combining  blue  ana  yellow, 
"Wool  is  first  dyed  blue,  and,  having  then  been  mordanted  with  cream  of  tartar  and 
alum,  is  dyed  with  fustic,  or,  on  the  Continent,  with  weld.  The  green  cloth  used  for 
covering  billiard-tables  and  other  furniture  is  dyed  in  the  following  manner : — A  weak 
decoction  of  fustic  is  prepared,  and  into  this  some  Saxony  blue  is  poured,  while  there 
is  next  added  alum  and  cream  of  tartar.  The  woollen  fabric  is  immersed  in  the  bath 
and  boiled  for  two  hours.  It  is  next  thoroughly  washed  and  brightened  by  being 
again  immersed  in  a  dye-beck  filled  with  a  fresh  fustic  decoction,  to  which  a  smaller 
quantity  of  Saxony  blue  has  been  added.  All  kinds  of  woollen  tissues,  worsted,  half- 
wool,  alpacas,  delaines,  &c.,  may  be  dyed  green  by  means  of  lo-kao  (Chinese  green)  and 
iodine  green. 

Among  the  green  tar  colours  those  most  commonly  used  are  methyl  green,  malachite 
green,  and  iodine  green.  As  methyl  green  is  transformed  at  high  temperatures  into  a 
violet  colour,  hot  rollers  cannot  be  used  in  finishing  goods  dyed  with  this  colouring 
matter.  Malachite  green  and  analogous  tar  colours  are  often  used  along  with  picric  acid. 
Mixed  colours,  singularly  spoken  of  in  France  and  Germany  as  modes,  are  obtained  by~ 
mixtures  of  greens  with  cochineal,  fustet,  madder,  &c. 

Slack  Dyeing. — Excepting  only  aniline  black,  all  black  dyes  may  be  considered  as  com- 
binations of  iron  or  chrome  with  tannic  or  gallic  acid ;  but  the  best  and  fastest  blacks  on 
broadcloth  are  such  as  have  as  a  first  dye  either  madder  or  indigo.  The  woollen  goods- 
are  mordanted  with  ferrous  sulphate  (green  copperas)  and  dyed  by  immersion  in  a 
decoction  of  logwood,  galls,  sumac,  &c.  The  so-called  Sedan  black  (this  town  is  cele- 
brated for  its  cloth  manufacture)  is  produced  by  dyeing  the  cloth  blue  with  woad, 
when,  after  careful  washing,  it  is  placed  in  a  dye-beck  containing  water,  sumac,  and 
logwood,  and  is  boiled  for  some  three  hours,  after  which  copperas  in  a  solution  of 
known  strength  is  added.  This  operation  is  repeated  until  the  cloth  has  assumed 
an  intensely  black  colour.  Half -fast  black  colours  are  produced  on  cloth  by  dyeing 

*  The  composition  of  the  bath  requires  to  be  varied  according  as  the  wool  is  hard  or  soft ;  some 
dyers  use  a  stannic  chloride. — [EDITOR.] 


SECT,  vii.]  DYEING   AND  TISSUE-PRINTING.  835 

them  blue  with  Prussian  blue,  after  Avhich  the  operation  just  described  is  gone  through. 
Common  black  is  produced  by  dyeing  with  logwood,  sumac,  some  fustic,  and  a  mixture 
of  green  and  blue  vitriol.  Chromium  black,  invented  by  Leykauf  at  Nuremberg,  is 
obtained  in  the  following  manner : — The  cloth  is  mordanted  with  a  solution  of 
potassium  bichromate  and  cream  of  tartar,  after  which  it  is  dyed  in  a  decoction  of  log- 
wood. The  so-called  iron  pyrolignite  (crude  iron  acetate  prepared  from  scraps  of 
old  iron  and  crude  acetic  acid)  is  now  very  generally  used  as  a  mordant  instead  of  the 
green  copperas.  This  acetate,  also  known  as  black  or  iron  liquor,  is  prepared  on  the 
large  scale  and  sold  as  a  liquid  at  a  sp.  gr.  of  1*09  to  1-14. 

Vienna  black,  used  in  the  cloth  works  in  the  Department  Isere,  is  obtained  as 
follows : — For  one  piece  of  cloth  weighing  30  kilos,  there  are  boiled  in  the  dye-pan 
6  kilos,  logwood  and  i  kilo,  fustic  for  thirty  minutes ;  2  kilos,  gall-nuts  are  added,  and  as 
much  sumac,  and  it  is  again  boiled  for  half  an  hour.  The  cloth  is  then  entered  and 
turned  for  half  an  hour,  taken  out,  and  aired.  2  kilos,  of  copperas  are  dissolved  in  the 
beck,  and  the  cloth  is  again  entered  and  worked  for  one  hour,  without  coming  to  a 
boil.  It  is  again  taken  out,  i  kilo,  of  copperas  is  added,  and  the  cloth  is  re-entered  and 
again  treated  as  above.  Finally,  it  is  Avashed  in  a  fulling  mill. 

Very  similar  is  the  Bedarieux  black  produced  upon  woollens  in  a  boiling  bath  of 
logwood  (3  kilos,  to  15  kilos,  cloth),  0*5  kilo,  fustic,  and  3  kilos,  sumac,  with  the 
addition  of  0^75  kilo,  copperas. 

Geneva  black  is  obtained  with  logwood  and  fustic,  with  copperas  and  bluestone 
along  with  a  little  argol. 

Tours  black  is  got  up  with  logwood,  sumac,  copperas,  and  a  little  verdigris.  The 
cloth  is  entered  five  times  in  the  dye-bath  and  aired  between  each  operation,  whence 
it  is  called  noir  d,  cinqfeux. 

Nenuphar  black  is  obtained  by  boiling  wool  with  the  roots  of  the  white  water-lily, 
logwood,  and  a  little  sulphuric  acid,  and  dyeing  up,  after  airing,  with  copperas  or  black 
liquor. 

Vanadium  black  on  wool  is  an  aniline  black  obtained  in  a  not  of  1000  water,  80 
salt  of  aniline,  40  potassium  chlorate,  5  hydrochloric  acid,  and  o-i  ammonium  vanadate. 
That  cloth  dyed  black  is  especially  liable  to  become  rotten  is  due  on  the  one  hand  to 
the  oxidising  action  of  the  iron  mordants,  and  on  the  other  to  the  circumstance  that 
when  the  dyer  has  failed  in  producing  the  right  shade  on  a  piece  of  cloth  it  is  dyed  black, 
and  has  of  course  been  enfeebled  by  the  extra  boilings,  &c.,  which  it  has  undergone. 

Silk-dyeing. — Silk  is  usually  dyed  in  skeins,  either  in  the  crude  state  (souple)  or 
after  it  has  been  ungummed.  It  is  then  scoured,  bleached,  and  sulphured ;  the  latter  only 
when  the  silk  is  to  be  dyed  with  very  bright  colours  and  delicate  light  hues.  Silk  is 
chiefly  dyed  in  cold  dye  solutions.  It  is  dyed  black  by  any  of  the  following  processes  : — 

1 .  Logwood  and  iron  mordant ; 

2.  Logwood  and  potassium  bichromate ; 

3.  Galls  and  other  substances  containing  tannic  acid  with  iron  salts  as  mordant ; 

4.  With  aniline  black,  according  to  the  recipes  of  Persoz,  jun.,  and  others,  by 

the  use  of  copper  chromate  and  aniline  oxalate. 

The  first  and  second  are  simply  known  as  ordinary  blacks,  while  the  third  is  known 
as  fast  black.  The  ordinary  black  is  obtained  by  simply  mordanting  the  silk  with 
iron  nitrate,  and  then  dyeing  it  in  a  decoction  of  logwood.  This  cheap  dye  is  more 
particularly  applied  to  light  silken  fabrics.  The  colour  is  reddened  even  by  weak  acids, 
such  as  lemon  and  orange  and  other  fruit  juices.  The  fast  black  is  far  more  expensive, 
but  it  is  not  affected  by  weak  acids,  while  it  affords  the  additional  advantage  of  largely 
increasing  the  weight  of  the  silk  (in  the  raw  state,  as  well  as  in  spun  yarn,  silk  is  sold 
and  bought  by  weight),  as  this  textile  fibre  absorbs  from  60  to  80,  and  even  100  per  cent, 
of  its  own  weight,  and  silk  used  for  shoe-laces  even  225  per  cent,  of  the  dye  material. 
When  desired,  the  silk-dyer  has,  for  100  Ibs.  of  raw  silk  delivered  to  him,  to  return  from 


«36  CHEMICAL  TECHNOLOGY.  [SECT.  vu. 

160  to  180  or  250  Ibs.  of  dyed  material,  the  increase  being  obtained  by  "  weighting." 
In  England  nut-galls  imported  from  the  Levant  are  employed  to  dye  silk  black. 
Although  the  increase  in  weight  of  the  silk  by  black  dyeing  is  advantageous  to 
the  dealers,  the  depositing  of  so  much  foreign  matter  in  the  fibre  of  the  silk,  not 
only  injures  its  wearing  qualities,  but  also  gives  rise  to  the  disagreeableness  of  the 
•dye  coming  off  while  the  material  is  being  worn.  Microscopic  research  has  proved 
that  the  dye  adheres  very  loosely  to  the  silk.  The  process  of  dyeing  silk  black  with 
galls  is  very  simple.  The  fibre  is  first  steeped  in  a  solution,  or  rather  infusio- 
decoction,  of  galls,  technically  known  as  "  galling,"  after  which  the  silk  is  placed  in 
a  solution  of  iron  nitrate.  This  black  is  sometimes  dyed  on  silk  previously  dyed 
with  Prussian  blue,  but  far  more  frequently  a  bluish  shade  is  given  to  black  by  first 
dyeing  the  silk  with  logwood,  copperas,  and  some  copper  sulphate. 

As  regards  the  weighting  of  the  silk,  it  is  essentially  due  to  the  fact  that  silk,  as 
an  animal  product,  has  the  property  of  combining  with  tannic  acid  and  thereby  becoming 
heavier.  The  larger,  therefore,  the  quantity  of  tannic  acid  contained  in  the  dye-bath, 
or  the  oftener  the  galling  of  the  silk  is  repeated,  the  heavier,  within  certain  limits,  will 
the  fibre  become.  It  is  not  quite  indifferent  whether  a  ferric  or  ferrous  salt  of  iron  bo 
employed,  the  former  being  preferable.  The  previously  galled  silk  becomes,  when 
passed  through  a  solution  of  ferric  salt,  at  once  coloured  black ;  but  when  it  is 
passed  through  a  solution  of  a  ferrous  salt,  the  silk  becomes  at  first  coloured  only 
black-violet,  and  gradually  deep  black  by  exposure  to  air.  Although  in  every  case  the 
result  is  the  same,  the  use  of  a  ferric  salt  is  advantageous,  and  becomes  necessary 
•with  a  small  quantity  of  tannic  acid,  while  for  a  heavy  weighting  of  the  silk  the  ferrous 
salt  of  iron  only  can  be  employed.  It  is  stated  that  the  dyeing  of  silk  with  aniline 
black  by  means  of  copper  chromate  and  aniline  oxalate  yields  excellent  results. 

For  some  years  silks  have  also  been  dyed  with  an  aniline  black  got  up  with  ammo- 
nium vanadate. 

Blue  Dyeing. — Silk  is  dyed  blue  either  with  indigo,  Berlin  blue,  logwood,  or 
aniline  blues.  The  indigo  vat  has  not  been  much  used  for  imparting  a  blue  colour  to 
silk  since  the  discovery  of  fixing  Prussian  blue  upon  silk ;  and  if  indigo  is  used  at  all  it 
is  as  indigo  extract,  or  the  so-called  distilled  blue — purified  sulphindigotic  acid.  In 
order  to  dye  silk  with  Prussian  blue,  it  is  first  immersed  in  a  solution  of  iron 
nitrate.  This  salt  is  generally  in  use  in  England,  while  in  Fi-ance  iron  persulphate 
made  by  dissolving  green  copperas  in  nitric  acid  is  employed,  and  known  under  the 
name  of  Raymond's  solution,  the  blue  produced  being  termed  Raymond's  blue ; 
Napoleon  blue  is  produced  by  the  addition  of  a  tin  salt  to  the  iron  bath,  followed  by 
treatment  with  a  solution  of  potassium  ferrocyanide  acidulated  with  sulphuric  acid. 
The  latter  blue,  more  brilliant  than  the  former,  is  usually  preferred  in  England,  a 
tin  salt  being  invariably  added  to  the  iron  mordant.  The  mordanted  silk  is  next  passed 
through  a  boiling  soap  solution,  then  washed,  and  next  steeped  in  a  solution  of 
potassium  ferro-cyanide  acidulated  with  hydrochloric  acid.  The  brilliancy  of  the  dyed 
silk  is  greatly  enhanced  by  passing  it  through  water  containing  ammonia.  Dyeing  silk 
with  aniline  or  naphthaline  blue  is  a  very  simple  process,  it  being  only  necessary  to  put 
the  silk  into  a  solution  of  the  dyes,  the  solvent  being  alcohol  or  wood-spirit,  or,  in  the 
case  of  soluble  aniline  blue,  water.  The  silk  is  left  in  the  solution  until  it  has  assumed 
the  desired  hue. 

Until  very  recently  silks  were  dyed  red  with  safflower  (carthamine),  cochineal, 
and  orchil.  Now  magenta,  coralline,  safFranine,  eosine,  and  Magdala  red  are  employed.* 
Violets  are  still  dyed  on  silk  with  orchil,  which  is  being  gradually  superseded  by 
methyl  and  benzyl  violet. 

*  None  of  these  tar  colours  surpass,  even  if  they  equal,  carthamine  in  beauty.  No  true  rose 
can  be  dyed  with  magenta.  The  finest  reds  on  silk  are  now  produced  with  the  cosines. — [EDITOR,] 


SECT,  vii.]  DYEING  AND  TISSUE-PRINTING.  837 

Yellow  Dyes. — Yellow  is  produced  upon  silk  by  first  mordanting  with  alum  and 
dyeing  in  a  decoction  of  weld,  to  which,  if  it  be  desired  to  impart  an  orange  hue,  some 
annatto  is  added,  or,  preferably,  Manchester  yellow.  By  cautious  treatment  with  nitric 
acid,  silk  may  be  dyed  yellow,  some  xanthroproteic  acid  being  formed,  while,  without 
any  mordant,  picric  acid  produces  a  bright  lemon-yellow  on  silk,  the  colour  becoming 
deeper  by  treatment  with  alkalies.  The  production  of  picric  acid  upon  silk  by  the  action 
of  nitric  acid  is  not  now  in  use.* 

Green  Dyes. — Silks  are  now  dyed  green  almost  exclusively  with  methyl  green  and 
malachite  green. 

Cotton- dyeing. — Cotton  is  dyed  either  as  yarn  or  woven  fabric,  but  more  generally 
as  yarn.  Cotton  is  far  more  difficult  to  dye  than  wool,  and  requires,  especially  for 
obtaining  fast  colours,  stronger  mordants.  Blue  is  produced  upon  cotton  (which,  when 
woven,  is  termed  calico)  by  means  of  the  copperas  vat  (see  Indigo) ;  further,  by  Berlin  or 
Prussian  blue,  logwood,  and  green  copperas;  and,  finally,  by  being  passed  through 
a  solution  of  copper  oxide  in  ammonia,  the  fibre,  yarn,  or  tissue  after  drying  ex- 
hibiting a  beautiful  bright  blue  colour.  Yellow  is  produced  with  Persian  berries, 
weld,  fustic,  quercitron,  annatto,  iron  acetate,  technically  known  as  black  liquor 
(nankeen),  and  chrome-yellow.  Green  is  obtained  by  the  copperas  vat  followed  by 
dyeing  with  fustic.  Brown  is  produced  with  a  salt  of  iron  and  with  quercitron  or 
madder,  or  simply  by  means  of  hydrated  manganese  oxide.  Black  is  either  a  fast 
aniline  black,  or  is  produced  by  dyeing  blue  by  the  aid  of  the  copperas  vat,  next 
mordanting  with  iron  acetate,  and  then  dyeing  in  a  bath  consisting  of  galls  and 
logwood.  The  majority  of  the  aniline  colours  can  be  fixed  upon  cotton  only  by  the- 
aid  of  a  specific  mordant — a  solution  of  tannin  in  alcohol ;  or  the  fibre  of  cotton  is  first 
animalised,  as  it  is  termed — that  is  to  say,  impregnated  with  either  albumen  or  caseinr 
the  fibre  being  thus  to  a  certain  extent  made  similar  to  that  of  wool  or  silk,  and  ren- 
dered absorbent  of  aniline  dyes.  Cotton  may  be  mordanted  with  Gallipoli  oil  or  for 
certain  dyes  with  soft  soap. 

A  very  important  observation  has  been  made  by  Witz,  Cross,  and  Schmidt,  that 
cotton  oxidised  by  chloride  of  lime,  chloric  acid,  &c.,  readily  takes  up  colouring-matters. 
The  bath  employed  is  a  solution  of  potassium  chlorate,  saturated  at  common  tempera- 
tures, and  containing  to  i  mol.  KC103  less  than  i  mol.  HC1,  but  more  than  -J  mol. 
and  o-oi  gramme  vanadium  per  litre  in  the  state  of  chloride.  The  cotton,  whether 
loose,  as  yarn  or  as  cloth,  and  whether  crude  or  scoured,  is  steeped  in  the  solution  and 
then  wrung  out,  or,  after  insertion  in  the  liquid,  it  is  quickly  exposed  to  a  heat  of  60°, 
until  the  formation  of  chlorous  acid  is  indicated  by  vapours  or  by  the  appearance  of  a 
yellow  colour.  Or  there  is  used  as  an  oxidising  bath  a  solution  of  potassium  dichromate, 
saturated  at  common  temperatures,  and  acidulated  with  i  to  2  mols.  hydrochloric  acid 
or  sulphuric  acid  to  i  mol.  K,CrzO7.  The  cotton  is  steeped  in  this  liquid  for  thirty- 
minutes.  If  it  is  desired  to  increase  the  action,  the  liquid  may  be  slightly  heated,  or 
the  effect  may  be  reduced  by  the  addition  of  water.  In  every  case  the  cotton  is  thoroughly 
washed  after  oxidation,  and  it  is  then  ready  for  dyeing. 

According  to  a  process  given  by  the  Baden  Aniline  Company,  cotton  (loose,  in  yarn, 
or  cloth)  is  placed  in  a  bath  of  from  30  to  40  grammes  turkey-red  oil  (sulphoricinate)  per 
litre,  whizzed,  and  dried  at  from  50°  to  60°.  As  a  chrome  mordant  there  is  used  a  basic 
chromium  chloride,  obtained  by  dissolving  precipitated  chromium  hydrate  in  an  insuffi- 
cient quantity  of  hydrochloric  acid.  The  oiled  cotton  is  soaked  in  such  chromium 
chloride  at  14°  Tw.  for  from  two  to  three  hours,  turned  out,  and  washed.  To  remove  all 
mineral  acids,  it  is  taken  through  sodium  acetate  at  5  grammes  per  litre  and  washed 
again.  The  goods  are  then  ready  to  be  dyed.  Calcareous  water  must  be  neutralised  or 

*  Picric  acid  cannot  be  used  for  dyeing  handkerchiefs  or  other  articles  which  have  to  be  washed, 
as  the  colour  is  discharged. — [EDITOR.] 


838  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

acidified  to  prevent  the  formation  of  an  insoluble  lime-lake  of  alizarine  blue  or  ceruleine. 
Light  shades  require  3  per  cent,  of  alizarine  blue  (S)  or  ceruleine,  and  dark  shades 
require  6  per  cent.  The  flot  is  heated  slowly  and  gradually ;  cotton-wool  is  kept  in  it 
for  two  hours  at  from  70°  or  80°,  whilst  yarn  and  cloth  are  boiled  for  an  hour.  After 
dyeing,  the  steaming  follows,  at  once  in  the  case  of  loose  cotton,  but  after  a  repeated 
oiling  in  the  case  of  yarn  or  cloth.  The  process  is  concluded  by  washing  and  soaping. 
Alizarine  red  and  orange  can  be  dyed  under  the  same  conditions  in  the  chrome  bath. 

C.  Koechlin  mordants  the  cotton  in  a  bath  containing  to  100  kilos,  of  goods  10  to 
1 2  kilos,  of  tin  crystals,  5-3  kilos,  of  stannic  chloride  at  1 1 5°  Tw.  (  =  3  litres),  and  2^  kilos, 
sulphuric  acid  at  154°  Tw.,  together  with  water  enough  to  wet  the  cotton  thoroughly. 
The  hanks,  after  being  wrung  out,  are  left  lying  over-night,  washed  well,  and  then 
taken  through  a  bath  of  from  40  to  50  grammes  of  soda-crystals  per  litre  at  4QC.  The 
cotton,  when  washed,  is  ready  for  chroming.  It  is  worked  for  an  hour  at  80°  in 
a  beck  of  from  40  to  50  grammes  chrome  alum  per  litre.  Probably  the  use  of 
basic  chrome  salts,  as  Cr4(S04)3(OH)6,  would  be  better.  H.  Koechlin  uses  chromium 
acetate. 

The  solid  violet  obtained  by  H.  Koechlin  by  the  action  of  nitrosodimethylaniline 
upon  gallic  acid,  after  it  has  been  rendered  soluble  with  sodium  bisulphate,  can  be  at 
at  once  dyed  upon  cotton  mordanted  with  chrome,  and  yields  fine  violet-blue  tones, 
which  approach  aniline  violet  in  brightness,  but  are  distinguished  by  their  far  greater 
fastness.  If  solid  violefc  is  dyed  along  with  yellows,  such  as  bark  or  berries,  &c.,  we 
obtain  deep  blues,  resembling  indigo.  According  to  the  tone  desired,  the  bath  is  made 
up  with  from  10  to  1 5  per  cent,  of  solid  violet  (calculated  on  the  weight  of  the  cotton)  and 
from  6  to  1 2  per  cent,  extract  of  bark  at  14°  Tw.,  with  the  addition  of  from  i  to  2  per  cent, 
tannin  and  from  o'i  to  0*2  per  cent,  methylene  blue.  Piece  goods  may  be  dyed  in  this 
flot  in  a  jigger.  They  are  entered  at  the  common  temperature,  which  is  then  gradually 
and  regularly  raised  in  an  hour  and  a  half  to  70°,  at  which  temperature  it  is  allowed  to 
remain  from  a  quarter  to  half  an  hour.  The  bath  is  completely  exhausted,  and  the 
pieces  are  then  washed  and  dried.  If  they  are  steamed,  the  colour  not  merely  becomes 
much  deeper,  but  also  much  faster.  The  colour  also  yields  better  if  the  alkaline  chrome 
bath  is  applied  to  pieces  which  have  been  prepared  in  a  bath  of  tin  chloride  (i  litre  SnCl4 
at  1 1 4°  to  1 6  litres  water).  The  blue  thus  obtained  bears  soaping,  exposure  to  light  and 
dilute  acids,  and,  if  it  is  not  as  fast  as  vat  blue  against  alkaline  carbonates,  it  has  the 
advantage  of  not  smearing  off.  The  fibre  is  dyed  through  and  through,  whilst  indigo 
is  deposited  more  on  the  surface,  and  therefore  rubs  off  on  repeated  washing  and  the 
accompanying  friction.  A  further  advantage  of  the  fast  blues  obtained  with  solid 
violet  is  the  ease  with  which  their  tone  can  be  modified  at  pleasure  from  the  purest 
violet  to  the  greenest  blue  by  merely  changing  the  proportions  of  violet  and  bark- 
liquor,  whilst  indigo  does  not  admit  of  such  modulations. 

Turkey  Red. — Of  the  three  similar  processes,  that  with  turkey-red  oil  is  the  most 
important.  The  bleached  and  dyed  cotton  is  saturated  by  steeping  or  padding  with  a 
solution  of  from  10  to  15  kilos,  of  saturated  turkey-red  oil  (50  per  cent.)  to  100  litres 
water.  The  excess  is  drained  off  and  the  cotton  is  dried.  It  is  steamed  for  from  sixty 
to  ninety  minutes,  and  then  worked  for  from  two  to  four  hours  at  a  hand-heat  in  red 
liquor  or  in  a  solution  of  basic  aluminium  sulphate,  Al2(S04)a(OH)2,  at  7°  Tw. 

After  mordanting,  the  excess  of  the  aluminium  salt  is  removed  in  a  centrifugal,  and 
the  cotton  is  dried  and  washed  in  cold  water,  or  first  treated  for  half  an  hour  at  from  40° 
to  50°  in  a  chalk  bath  containing  from  20  to  30  grammes  ground  chalk  per  litre.  Alkaline 
fixing  agents,  such  as  ammonia  and  sodium  carbonate,  must  be  avoided,  as  they  would 
strip  off  a  part  of  the  oil  preparation.  Then  follows  dyeing,  with  from  15  to  20  per  cent, 
of  alizarine  ( 10  per  cent,  strength),  with  the  addition  of  i  per  cent,  of  its  weight  of  chalk 
or  calcium  acetate.  The  cotton  is  dyed  in  the  cold  for  half  an  hour  to  secure  a  level 
colour,  and  the  temperature  is  then  gradually  raised  in  the  course  of  an  hour  to  70% 


SECT,  vii.]  DYEING   AND   TISSUE-FEINTING.  839 

and  the  dyeing  is  continued  at  this  temperature  till  the  bath  is  exhausted.  The  cotton 
is  next  thoroughly  washed,  avoiding  very  calcareous  water,  the  excess  of  liquid  is 
removed  with  the  centrifugal,  and  the  cotton  pressed  and  dried. 

The  dyed  and  dried  cotton  is  again  saturated  with  a  dilute  solution  of  neutralised 
turkey-red  oil  (from  50  to  60  grammes  to  the  litre),  and  dried.  This  second  preparation 
may  also  take  place  after  the  mordanting,  in  which  case  the  oil  is  fixed  upon  the 
fibre  by  a  second  treatment  with  a  weak  solution  of  basic  aluminium  sulphate.  The 
dried  cotton  is  again  steamed  for  an  hour  as  before,  and  raised  with  soap  and 
stannous  chloride. 

Aniline-Mack  Dyeing. — In  the  old  process,  chiefly  used  in  printing,  the  black  is 
developed  in  the  so-called  oxidation-rooms,  i.e.,  chambers  in  which  the  goods  printed 
with  the  black  colour,  after  being  quickly  dried  in  a  drying  chest,  are  hung  up  to 
oxidise.  This  hanging  process  is  suitable  only  for  the  development  of  patterns,  but  not 
for  giving  calicoes  a  uniform  black  ground,  since,  wherever  the  tissue  is  not  exposed  to 
the  air  in  a  uniform  tension,  lighter  stripes  remain,  which  cannot  be  removed  by  any 
subsequent  treatment.  Wherever  a  black  ground  is  required,  it  has  been  found 
advisable  to  develop  the  black  in  a  steam  chest,  in  which  the  mordanted  pieces  are 
oxidised  merely  by  steaming,  without  the  intervention  of  drying.  This  steam  aniline 
black,  however,  does  not  equal  the  blacks  produced  by  oxidation  in  the  air  in  respect  to 
beauty  and  purity  of  colour. 

The  third  process,  now  very  generally  used  for  cotton  yarns,  both  in  hanks  and  in 
warps,  depends  on  the  use  of  a  metallic  salt,  generally  potassium  chromate,  to  effect 
the  oxidation  in  the  formation  of  aniline  black.  But  this  process  is  not  suitable  for 
producing  blacks  on  piece  goods,  for  not  only  is  it  very  difficult  to  obtain  a  uniform  dye 
in  this  manner,  but  this  aniline  black  smears  off,  as  it  is  not  perfectly  attached  to  the 
•fibre.  Hence  it  follows  that  the  black  produced  by  oxidation,  as  it  does  not  smear  off 
at  all,  surpasses  every  other  aniline  black  in  quality. 

As  far  as  piece-dyeing  is  concerned,  the  original  process  has  been  very  widely 
resumed,  but  the  drying  and  oxidation  processes  take  place  in  a  long  chest  in  which  the 
tissue,  saturated  with  the  mordant,  is  passed  slowly  up  and  down,  stretched  out  equally. 
The  interior  of  the  apparatus  is  kept  at  a  temperature  of  from  44°  to  50°  by  means  of  hot- 
air  pipes,  and  the  vapours  and  gases  given  off  are  drawn  away  uniformly  the  entire 
length  of  the  chest.  The  drying  and  oxidation  of  the  mordant  take  place  in  the  front 
of  the  chest,  and  fresh  air  of  about  25°  streams  constantly  from  below  into  this  part  of 
the  chest  and  between  the  tissues.  As  soon  as  the  goods  thus  dried  and  oxidised 
arrive  at  the  back  part  of  the  apparatus,  which  is  completely  closed,  they  begin  to 
show  colour.  At  the  end  of  the  chest  there  are  placed  between  the  folds  of  the  tissues, 
some  water-troughs,  to  ensure  a  moist  atmosphere,  which  is  essential  for  the  pro- 
duction of  a  good  black. 

Linens  are  dyed  like  cottons,  but  the  process  is  more  difficult,  as  the  affinity  of  the 
linen  fibre  for  colouring-matters  is  still  feebler  than  that  of  the  cotton  fibre. 

Tissue-printing. — The  most  important  part  of  tissue-printing  is  cotton-  or  calico- 
printing.  It  depends  on  the  same  principles  as  dyeing,  but  it  has  much  greater  difficul- 
ties to  encounter,  partly  because  only  certain  given  spots  have  to  take  up  the  colours 
with  well-defined  outlines,  whilst  other  parts  remain  colourless  or  have  to  be  deprived 
of  colour,  and  partly,  again,  because  several  colours  have  to  be  produced  in  juxtaposition. 
There  is  further  required  a  pleasing,  tasteful,  and  artistic  arrangement  of  the  colours. 
The  colours  applied  in  tissue-printing  may  be  divided  into  two  main  classes — those  in 
which  the  colours  are  at  once  placed  directly  upon  the  cloth  by  means  of  engraved 
rollers  or  plates  (application  colours),  and  those  which  are  obtained  by  the  immersion 
of  the  tissue  in  a  dye  bath  (generally  called  pan  or  madder  colours).  To  the  former 
belong  the  iron  colours,  Prussian  blue,  madder  lake,  indigo,  cochineal,  and  most  of  tho 
-coal-tar  colours.  In  the  second  class  fall  madder  and  alizarine,  cochineal,  logwood, 


840  CHEMICAL  TECHNOLOGY.  [SECT,  vm 

weld,  sumac,  &c.  If  steam  is  used  to  fix  the  colours  upon  the  tissue,  we  have  the  steam 
styles.  If  the  colours  are  of  an  inorganic  nature  (ultramarine)  or  lakes  (madder  lake),, 
which  are  fixed  mechanically — i.e.,  by  the  help  of  albumen,  caseine,  gluten,  or  oil 
varnish — we  have  the  pigment  style.  The  pan  colours  are  more  generally  applied  in 
calico-printing.  The  tissue  is  passed  into  the  dye  pan  as  if  it  was  to  be  dyed  of  one- 
colour,  but  by  various  means  the  colour  is  only  attached  locally. 

If  the  colouring-matter  requires  a  mordant  for  its  fixation,  this  is  often  printed  on 
alone,  and,  after  dyeing,  there  is  thus  obtained  a  coloured  design  upon  a  white  ground. 
If,  e.g.,  the  cloth  is  printed  with  thickened  red  liquor  and  dyed  up  in  the  madder  (ali- 
zarine) beck,  the  mordanted  parts  only  are  dyed  red,  &c.  In  this  manner  are  obtained 
the  so-called  madder  styles.  Or  the  parts  which  are  to  remain  white  are  printed  with 
a  resist,  i.e.,  a  preparation  which  hinders  the  colouring-matter  from  attaching  itself  to 
such  parts.  Thus  in  the  case  of  indigo  we  use  as  resists  copper  acetate  or  sulphate ; 
if  cloth  thus  printed  is  passed  into  the  indigo  vat,  the  ground  is  dyed  blue  whilst  the- 
design  remains  white. 

There  is  often  added  to  a  resist  a  mordant  for  some  other  colour,  so  that  the  places 
which  remain  white  in  the  vat  may  take  up  some  other  colour  in  a  dye  beck,  which 
acts  merely  on  the  resisted  or  the  reserved  parts.  Here  belongs  the  so-called  lapis 
style. 

The  cloth  may  also  be  uniformly  mordanted  or  dyed,  and  then  the  mordant  or  the 
colour  is  removed  in  parts.  The  agents  employed  are  called  discharges  (Fr.  erilevagest 
Ger.  Aetzbeizen}.  If  the  cloth  is  first  uniformly  treated  with  a  mordant  and  then 
printed  with  a  discharge  (e.g.,  citric  or  tartaric  acid),  which  dissolves  the  alumina  or 
the  iron  oxide  of  the  mordant,  then  on  dyeing  we  obtain  a  white  design  on  a  coloured 
ground.  A  similar  result  is  obtained  by  printing  a  suitable  discharge  on  dyed  cloth. 
Such  are  either  oxidising  agents  (like  chloride  of  lime  and  chromic  acid)  or  reducing 
agents  (like  salt  of  tin  or  ferrous  sulphate). 

Here  may  be  mentioned  a  curious  application  of  photography  to  tissue-printing. 
The  cloth  to  be  printed  is  padded  with  a  preparation  sensitive  to  light,  then  covered 
with  a  thick  black  paper  in  which  the  pattern  is  cut  out,  and  exposed  to  the  sun, 
when  the  parts  not  protected  are  coloured.  The  matter  susceptible  to  light  is  then 
removed. 

The  above-mentioned  processes  can  be  almost  indefinitely  modified  for  the  produc- 
tion of  certain  designs.  Thus,  if  a  cloth  has  been  printed  with  mordants  and  dyed,  the 
mordanted  parts  appear  coloured  upon  a  white  ground.  Upon  this  ground  other 
mordants  or  colours  may  be  blocked  in.  Colours  which  have  been  already  produced 
may  be  modified  by  printing  upon  them  other  mordants  or  colouring-matters,  thus 
producing  conversion  colours  (couleurs  de  covnersiori). 

The  pieces  which  are  to  be  printed  are  singed,  bleached,  and  calendered  by  a  passage 
between  rollers  to  press  the  threads  of  the  tissue  smooth,  so  as  to  give  the  cloth  a  per- 
fectly even  surface  to  which  the  mordants  and  colours  may  be  applied  uniformly. 
The  cloth  is  then  printed. 

Thickenings* — In  order  to  give  the  colours  or  mordants  used  in  printing,  either  by 
block  or  cylinder,  a  sufficient  consistency,  they  are  mixed  with  what  are  technically 
known  as  thickenings.  As  such  are  used — Gums  Senegal  and  tragacanth,  leiocome, 
British  gum,  dextrine,  salep,  flour,  gluten,  pipe-clay  with  gum,  glue,  and  size,  lead 
sulphate,  sugar,  molasses,  glycerine,  starch,  sometimes  zinc  chloride  and  nitrate. 

*  If  the  intensity  of  the  colour  produced  by  means  of  a  mordant  is  inversely  as  the  quantity 
of  the  solids  which  the  mordant  requires  for  the  thickening,  the  reason  lies  in  the  property  of 
solids  to  form  with  a  portion  of  the  mordant,  a  compound  upon  which  the  tissue  has  no  action, 
and,  partly,  also  because  a  colour  which  contains  less  solid  matter  in  a  given  volume,  when  dyeing, 
undergoes  a  kind  of  fading  which  is  far  greater  than  when  the  thickening  predominates. — [EDITOR.] 


SECT,  vii.]  DYEING   AND   TISSUE-PRINTING.  841 

The  purity  of  the  colours  and  the  distinctness  of  the  outlines  depend  on  the  right 
selection  of  the  thickeners.  Not  every  substance  which  has  the  property  of  rendering 
liquids  glutinous  can  be  thus  used.  Thus,  sugar  is  generally  excluded  in  consequence  of 
its  tendency  to  deprive  the  mordants  of  their  affinity  for  the  fibre.  In  the  selection  of 
a  thickener  for  any  particular  case  the  colour-mixer  has  to  be  guided  by  the  following 
considerations : — 

1.  He  must  attend  to  the  temperature  necessary  for  thickening  a  colour;  if,  e.g.,  a 
colour  is  apt  to  be  decomposed  in  heat,  flour  and  starch  are  not  admissible,  since  these 
substances  thicken  only  when  mixed  hot. 

2.  The   reaction   of  the   colour   or    mordant  is  important.     If  it  is  very  acid, 
flour,  starch,  and  dextrine  are  excluded,  since  these  substances  are  liquefied  by  the 
action  of  the  acids,  and  form  products  which  have  often  an  injurious  action  upon  the 
colours.     If  the  reaction  is  alkaline,  the  question  is  does  it  contain  earths  or  metallic 
oxides :  in  the  former  case  all  thickeners  which  are  coagulated  by  alkalies,  such  as  flour 
and  starch,  are  excluded,  but  gums  and  dextrine   are   admissible;    in    the  second 
case  no  thickener  which   forms   insoluble  compounds  with  metallic  oxides  must  be 
admitted. 

3.  All  decompositions  between  constituents  of  the  colour  or  the  mordant  and  those 
of  the  thickener  must  be  avoided ;  thus,  basic  lead  acetate  precipitates  most  of  the 
thickeners  above  mentioned  with  the  exception  of  sugar.     Ferric  salts  are  coagulated 
by  gums  tragacanth  and  Senegal,  and  must  therefore  be  thickened  with  starch  or 
dextrine.     Stannic  chloride  and   iron  tannate  are  not   coagulated   by  gum  Senegal, 
but  by  all  other  thickeners. 

4.  The  consistency  of  the  colour  is  to  be  regarded,  as  the  speed  with  which  it  dries 
may  have  a  great  influence  upon  the  intensity  of  the  colour  as  it  appears  on  the 
calico.      Thus,  iron  and  aluminium  mordants  (which   are  distinguished    for  drying 
rapidly)  do  not  give  such  full  colours  if  thickened  with  gum  as  if  starch  had  been 
used. 

5.  The  intensity  of  the  colour  to  be  produced  is  often  important.     A  mordant 
thickened  with  tragacanth  or  starch  paste  yields  stronger  tones  than  if  gum  Senegal  or 
dextrine  had  been  used. 

6.  The  colour  of  the  thickener  is  unimportant  only  if  the  colour  printed  upon  the 
tissue  can  bear  cleansing  and  the  removal  of  the  thickener  without  injury.    If,  in  print- 
ing woollens  witn  rose  or  blue,  two  colours  which  do  not  bear  washing  well,  they  are 
thickened  with  dextrine,  the  former  would  take  a  brownish  and  the  latter  a  greenish 
tone.     Upon  calico,  on  the  contrary,  both  colours  can   be    safely   thickened   with 
dextrine,  as  in  this  case  a  thorough  washing  is  practicable. 

7.  The   ease   with   which   a   thickener  can  be  removed  from  the  cloth  is  often 
decisive.     Even  a  colourless  thickener  may,  in  proportion  as  more  or  less  of  it  is  left 
upon  the  tissue,  have  an  injurious  effect  upon  the  colour,  and  give  the  cloth  properties 
which  impair  its  value. 

8.  The  degree  of  contraction  to  which  the  tissue  is  exposed  by  some  thickeners  is 
important,  especially  if  several  colours  have  to  be  printed  on  in  succession.     If  a  very 
thick  solution  of  gum  is  printed  upon  cloth,  it  contracts  in  drying  and  causes  the  cloth 
to  shrink  unequally,  producing  unevennesses,  which  render  the  subsequent  accurate 
application  of  other  colours  impossible.     To  avoid  this  evil  there  is  used  a  mixture  of 
thickeners,  which  counteract,  or  at  least  reduce,  this  shrinkage.     Thus,  the  solution  of 
gum  is  sometimes  mixed  up  with  pipe-clay,  lead  sulphate,  or  glycerine,  which  effects  a 
mechanical  division  of  the  gummy  mass. 

9.  The  succession  in  which  the  colours  are  applied  after  each  other,  or  upon  each 
other,  is  important,  for,  if  we  merely  regard  the  mordant,  the  design  may  easily  suffer 
by  the  mutual  action  of  the  thickeners  upon  each  other  and  by  their  colours.     The 


842  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

colour  to  be  printed  on  first  is  generally  the  darkest,  and  is  thickened  with  starch, 
whilst  the  next  is  thickened  with  gum.  In  fine  cylinder  work  with  three  colours,  the 
first  is  thickened  with  dextrine,  the  second  with  starch,  and  the  third  with  gum 
Senegal. 

10.  The  manner  of  producing  a  design  is  also  important.  If  it  is  very  delicate, 
starch  and  flour  are  inadmissible.  Thin  colours  must  be  used  for  shallow  engraving. 

Madder  Style. — Calico-printing  in  the  dye  beck  (otherwise  called  dyeing  upon  mor- 
dants) is  effected  by  printing  the  cloth  with  mordants>  and,  after  fixing  and  .drying 
them,  dyeing  up  with  madder,  alizarine,  or  other  colouring-matters,  when  only  the 
mordanted  parts  become  dyed,  whilst  the  ground  remains  white,  or  takes  up  merely 
so  little  colour  that  it  may  be  completely  removed  by  a  soap  or  a  bran  bath,  or  by  a 
slight  chlorising. 

Madder  printing  is  effected  as  follows  : — 

(a)  The  mordant  is  printed  on  with  the  cylinder  machine.  If  flowers  have  to  be 
produced  in  which  red,  brown,  and  black  occur,  the  mordants  are  put  on  simultaneously 
with  three  cylinders — with  the  one,  red  liquor  thickened  with  flour  or  starch ;  with  the 
second,  a  mixture  of  red  liquor  and  black  liquor ;  and  with  the  third,  black  liquor  (an 
iron  mordant).  The  following  may  serve  as  specimens  of  the  composition  of  the 
mordants: — For  red  liquor,  188  litres  water,  50  kilos,  alum,  5  kilos. soda,  and  38  kilos, 
sugar  of  lead  ;  the  mordant  decanted  off  from  the  lead  sulphate  marks  16°  to  16-5°  Tw. 
To  "sighten"  the  mordant — i.e.,  to  show  where  it  has  been  applied — i  litre  of  this 
liquid  let  down  to  675°  Tw.,  120  grammes  starch,  and  a  little  red-wood  or  logwood 
liquor  are  taken.  According  to  another  formula,  we  take,  to  100  litres  water,  35^- 
kilos,  alum,  24^  kilos,  sugar  of  lead,  4  kilos,  soda  crystals,  and  2  kilos,  common  salt. 
The  liquid  decanted  off  from  the  sediment  is  mixed  with  45  litres  zinc  nitrate  at  i'ii 
sp.  gr.,  thickened  by  boiling  with  z\  kilos,  starch,  and  sightened  with  100  grammes 
neutral  extract  indigo  dissolved  in  vinegar.  For  the  black  mordant,  take,  to  i  litre 
ferrous  chloride  at  9°  Tw.,  130  grammes  starch  and  130  grammes  wheat  flour.  The 
colour,  mixed  by  boiling  and  stirring,  is  intimately  incorporated  with  15  grammes 
olive  oil. 

Printing  on  the  mordants  is  not  always  merely  the  first  step.  Frequently,  if  it  is 
intended  to  produce  a  full  and  a  light  red  along  with  brown  and  black,  red  liquor  of  the 
proper  concentration  is  first  printed  on  by  two  cylinders,  then  air-dried,  dunged,  and 
dyed  up  in  the  madder  beck.  The  black  liquor  and  the  mixture  of  red  and  black 
liquors  for  browns  are  blocked  in  by  hand,  aired,  dunged,  and  dyed  up  in  a  beck  of 
madder  and  sumach. 

(6)  Drying  and  Ageing. — If  the  cloth  were  dried  in  the  air  just  as  printed,  the 
mordant  would  in  many  cases  spread  and  spoil  the  outlines  of  the  pattern.  Hence  it 
is  important  that  the  pieces,  when  dry,  should  hang  for  at  least  thirty-six  hours  in  a 
heated  chamber,  that  the  mordants  may  be  fixed  insolubly  upon  the  fibre. 

(c)  The  dunging  process  serves  not  merely  to  effect  a  more  intimate  combination  of 
the  base  of  the  mordants  with  the  fibre,  but  to  remove  a  part  of  the  thickening  and 
the  sightening  colour,  as  well  as  any  uncombined  parts  of  the  mordant. 

(d)  The  dyeing  in  the  madder  or  the  alizarine  beck  is  effected  either  in  a  single  process 
or  in  two  operations.     For  dyeing  in  a  single  operation  the  beck  is  filled  with  water.   As 
soon  as  the  temperature  has  reached  35°-45°,  the  madder  is  introduced,  and  the  pieces  are 
run  over  the  reel  in  the  beck,  which  is  kept  in  constant  motion  during  the  dyeing. 
The  temperature  of  the  beck  is  slowly  raised  so  as  to  reach  50°  in  half  an  hour,  and 
after  another  hour  70°,  at  which  the  beck  is  kept  for  another  half  an  hour,  and  is  then 
gradually  raised  to  a  boil.     When  the  dyeing  is  completed  the  pieces  are  wound  off 
the  reel,  and  washed.     Light  shades  are  generally  dyed  only  once ;  for  full  shades, 
especially  for  red  grounds,  the  dyeing  is  performed  twice.     For  the  success  of  the 


«ECT.  VH.]  DYEING  AND   TISSUE-PRINTING.  843 

process,  it  is  necessary  that  the  mordants  should  be  thoroughly  saturated  with  colouring- 
matter.  This  is  especially  the  case  for  colours  which  have  to  be  raised  or  taken  through 
flots  of  other  colouring-matters.  If,  e.g.,  it  were  intended  to  print  upon  the  white 
ground  of  the  cloth,  after  maddering,  red  or  black  liquors,  and  then  dye  them  up  in  the 
-quercitron  bark  beck,  the  first  mordants,  if  not  fully  saturated  with  the  madder  colour, 
would  take  up  a  yellow  colouring-matter,  and  thus  convert  the  red  into  an  orange  and 
the  violet  into  a  grey  olive-green.*  That  a  mordant  is  not  saturated  with  colouring- 
matter  is  known  because  during  dyeing  the  not  becomes  clear  and  exhausted, 
and  the  different  tones  are  not  sharply  distinguished.  Until  they  have  taken  up 
their  maximum  of  colour  they  seem  almost  alike.  The  want  of  colouring  matter  is 
•detected  too  late  when  the  dyed  pieces  lose  their  colour  in  bleaching.  A  certain  sign 
of  unsaturated  mordants  is  a  change  of  colour  when  the  goods  are  passed  into  a  bark 
beck. 

Among  the  ordinary  colouring-matters  fixed  by  means  of  alum  and  iron  mordants, 
that  of  madder  has  the  greatest  affinity  for  the  bases,  and  cannot  be  eliminated  by  any 
other  colouring-matter.  Hence  every  change  of  colour  in  a  beck  other  than  one  of 
madder  is  a  certain  sign  of  incomplete  saturation. 

In  dyeing  mixed  colours  with  madder  and  other  dye-wares  whose  affinity  for  the 
mordants  is  not  equal,  care  must  be  taken  that  no  more  madder  is  used  than  is  exactly 
.needed,  unless  the  dyeing  is  effected  in  two  separate  operations. 

Witz  utilises  oxycellulose  for  calico-printing  by  means  of  the  chlorates.  Chloric 
acid  can  be  substituted  for  the  hypochlorites  if  it  is  brought  into  contact  with  the  fibre 
under  such  circumstances  that  it  is  resolved  into  oxygen  and  unstable  oxides  of 
chlorine  under  the  influence  of  the  reagents  which  it  meets.  Vanadium  salts  decompose 
chloric  acid  most  easily  and  rapidly.  A  saturated  solution  of  potassium  chlorate  mixed 
with  rather  less  hydrochloric  acid  than  the  quantity  required  to  set  free  the  chloric 
.acid,  thickened  with  gum  tragacanth  and  with  10  milligrammes  vanadium  per  litre,  is 
printed  on  the  cloth.  On  drying  at  a  temperature  of  from  50°  to  60°,  the  formation  of 
oxycellulose  takes  place.  The  quantity  of  chlorate  and  of  vanadium  may  be  reduced 
according  to  the  temperature  and  the  duration  of  the  reaction.  Steaming  is  less  ad- 
vantageous than  hot  air.  Quick,  sharp  drying  evolves  a  strong  odour  of  chlorine,  and 
leads  to  energetic  oxidation,  which,  however,  is  not  attended  with  any  notable  injury 
to  the  fibre.  For  printing,  composition  "  doctors "  are  preferable  to  those  of  steel. 
Though  the  chief  action  of  the  chloric  acid  takes  place  during  drying  in  the  hot  air, 
yet,  in  order  to  prevent  injury  from  the  acid  vapours,  the  pieces  must  hang  for  some 
hours  in  a  warm  room,  which  must  be  well  ventilated.  Or  the  cloth  is  padded  with 
a  10  per  cent,  solution  of  potassium  bichromate,  and  dried.  A  starch  paste  contain- 
ing 15  per  cent,  of  oxalic  acid  is  then  printed  on  at  a  hand-heat.  The  goods  are 
•dried,  washed,  taken  through  weak  sours,  and  washed  again.  On  dyting  in  a  cold 
beck  of  methylene  blue,  the  design  comes  up  in  ten  minutes  as  a  deep  blue  on  a  pale 
blue  field. 

By  "  padding  on  mordants "  is  understood  a  process  by  means  of  which  the  cloth 
is  saturated  with  a  mordant  over  its  entire  breadth,  in  order  either  to  apply  different 
colours  to  it  topically,  or  to  dye  it  entirely,  forming  a  coloured  ground  upon  which 
-coloured  designs  may  be  produced  by  printing  on  mordants  and  dyeing  them  on  white 
•designs  by  printing  on  discharges. 

The  machine  used  in  this  operation  consists  essentially  of  two  brass  cylinders 
wrapped  round  with  thick  layers  of  a  cotton  tissue,  and  a  colour  trough  placed  beneath. 
The  piece  to  be  padded  passes  first  into  the  trough,  where  it  is  saturated  with  the 
mordant,  and  then  between  the  rollers,  which  are  pressed  together  by  a  weighted 

*  English  calico-printers  unfortunately  speak  of  madder  violet  as  "purple,"  which  leads  to 
eome  confusion. — [EDITOR.] 


844  CHEMICAL  TECHNOLOGY.  [SECT.  VIL 

lever,  which  promotes  the  absorption  of  the  mordant  into  the  cloth,  and  at  the  same 
time  removes  the  superfluous  liquid.  The  pieces  are  generally  passed  twice  through, 
the  pressure  being  stronger  the  second  time.  Red  liquor,  black  liquor,  and  mixtures 
of  both  can  be  applied  by  means  of  the  machine  with  great  uniformity.  In 
order  that  in  drying  the  padded  pieces  there  may  not  take  place  any  accumu- 
lation of  the  mordant,  which  would  occasion  spots  in  dyeing,  the  pieces  are  either 
stretched  out  horizontally  or  they  are  passed  on  guide-rollers  through  drying-stoves. 
The  dried  goods  are  washed,  dunged,  printed  with  the  colour,  washed,  and  raised  if 
necessary.  This  process  is  especially  suitable  for  inorganic  colours  in  buff,  Prussian 
blue,  manganese  or  bistre  brown,  chrome  yellow,  and  chrome  green. 

Printing  with  Resists. — Sometimes  there  are  applied  to  the  cloth,  at  places  which 
are  to  remain  white,  certain  substances  which  prevent  dyeing.  Such  substances  are 
known  as  resists.  In  most  cases  a  resist  serves  to  prevent  the  absorption  of  indigo- 
in  the  vat  at  the  reserved  places.  In  tissue-printing  there  are  four  different  kinds  of 
resists — the  fatty,  the  white,  the  coloured,  and  the  so-called  lapis. 

Fatty  Resists  are  used  chiefly  in  silk-printing,  sometimes  in  woollen-printing,  but 
rarely  on  calico.  They  consist  generally  of  wax  or  ceresine,  or  a  mixture  of  resin  and 
tallow,  or  resin  and  paraffine,  sometimes  of  an  emulsion  of  tallow,  palm  oil,  and  gum 
mucilage.  Now  and  then  fatty  resists  are  used  on  cottons.  If,  e.g.,  a  red  or  violet 
pattern  has  been  printed  upon  a  white  ground,  dyed,  and  raised,  and  it  is  intended  to 
produce  also  a  lighter  purple  colour  on  the  ground,  the  pattern  is  provided  with  a 
fatty  resist,  and  the  pieces  are  taken  through  a  dilute  iron  mordant,  proceeding 
exactly  as  in  the  madder  style.  As  the  designs  are  covered,  the  colours  reappear, 
after  the  second  raising,  with  their  original  shade. 

White  Resists. — A  very  common  constituent  of  white  reserves  is  a  copper  salt,  blue- 
stone,  or  verdigris,  which  is  thickened  with  pipe-clay  and  gum.  On  dyeing  up  in  the 
vat,  its  alkali  decomposes  the  salt  of  copper,  forming  at  once  insoluble  indigo-blue  from 
the  dissolved  indigo-white. 

Coloured  Resists  not  merely  prevent  the  indigo-blue  from  being  deposited  on  the 
reserved  parts,  but  also  produce  other  colours  in  these  reserved  places.  In  this 
manner  buff  and  chrome-yellow  designs  can  be  obtained  on  a  blue  ground. 

Lapis  Style. — This  manner  of  printing  consists  in  a  combination  of  the  madder 
style  and  of  indigo-vat  colours.  The  mordants  intended  for  the  madder  colours  are 
mixed  with  the  resists,  printed,  dyed  in  the  vat  to  the  shade  intended,  and  then  dyed 
in  the  madder  or  in  the  bark  beck,  and  the  whites  are  cleared.  The  lapis  style 
yields  not  only  very  fast,  but  very  manifold,  products,  in  consequence  of  the  numerous 
modifications  which  it  admits  of,  and  it  is  hence  extensively  used.  It  derives  its  name 
from  a  certain  resemblance  of  the  patterns  thus  obtained  upon  a  blue  ground  to- 
lapis  lazuli.  The  white  resists  in  this  style  have  not  merely  to  protect  certain  parts 
from  the  action  of  the  vat,  but  to  keep  them  unmordanted,  so  as  to  consume  as  little 
colour  as  possible  in  the  madder  beck.  In  this  case  mercuric  chloride  is  preferred  to- 
copper  sulphate. 

Two  kinds  of  white  resists  are  used  in  the  lapis  style.  The  one  kind  acts  like  the 
ordinary  resist  containing  copper  oxide — i.e.,  it  covers,  without  exerting  any  action 
upon,  the  mordants  beneath,  so  that  it  may  be  safely  printed  over  mordants  for  dark 
or  light  reds  without  interfering  with  their  subsequent  action.  The  other  kind5 
renders  the  mordant  ineffective.  To  this  latter  kind  belongs  a  resist  made  up  of  i| 
kilo,  sodium  arseniate,  i£  kilo,  gum  Senegal,  2  kilos,  pipe-clay,  and  4  litres  water,  with 
which  are  incorporated  by  boiling  500  grammes  olive  oil  and  375  grammes  mercuric 
chloride.  The  arsenic  acid  forms,  with  the  ferric  oxide  and  the  alumina  of  the  mor- 
dants afterwards  printed  on,  insoluble  arseniates  which  have  no  affinity  for  the  fibre. 
A  resist  of  the  first  kind  is  composed  of  a  mixture  of  0*5  kilo,  gum  Senegal,  i 


SECT,  vii.]  DYEING  AND  TISSUE-FEINTING.  845 

pipe-clay,  180  grammes  olive  oil,  and  2  litres  water,  to  which  180  grammes  mercuric 
chloride  are  added. 

Discharges  are  to  effect  the  local  removal  of  the  mordant  printed  upon  the  cloth  by 
means  of  thickened  acids.  On  dyeing  there  is  obtained  a  white  design  on  a  coloured 
ground.  Or  an  acid,  by  itself,  or  mixed  with  a  mordant,  is  printed  upon  the  cloth, 
upon  which  a  dark  mordant  is  then  padded  and  the  piece  is  dyed.  The  parts  printed 
with  the  acid  remain  white,  forming  white  designs  on  a  coloured  ground. 

The  acids  used  as  discharges  act  upon  the  metallic  oxides  in  the  mordants  and  form 
with  them  soluble  salts,  liberating  the  fibre  from  the  mordant.  The  common  mineral 
acids  (sulphuric,  nitric,  and  hydrochloric)  are  otherwise  suitable  for  this  purpose,  but 
they  are  apt  to  weaken  the  fibre,  whence  organic  acids  (such  as  malic,  citric,  and 
tartaric)  are  preferred,  as  they  do  not  tender  the  fibre  and  have  little  action  upon  the 
doctors  and  the  rollers.  Phosphoric  and  arsenic  acid  at  sp.  gr.  1*85  may  be  used 
instead  of  tartaric  acid,  as  can  also  hydrofluosilicic  acid.  Instead  of  i  kilo,  tartaric 
acid  there  may  be  used  from  1*25  to  1*5  kilo,  of  liquid  phosphoric  or  arsenic  acid.  The 
latter  has  the  grave  defect  that  it  attacks  the  hands  of  the  workmen,  destroys  the  finger 
nails,  and  is  highly  poisonous.  Oxalic  acid  is  commonly  used  in  the  proportion  of 
from  12  to  15  per  cent,  to  tartaric  acid.  It  has  the  property — very  important  for  the 
preparation  of  steam  colours — of  dissolving  alumina  and  ferric  oxide  in  the  cold  and 
of  re-depositing  them  at  higher  temperatures  in  an  insoluble  condition. 

Stannic  chloride  may  also  be  used  in  place  of  tartaric  acid :  1 1  parts  of  the  com- 
mercial salt,  as  free  as  possible  from  acid,  serve  instead  of  10  parts  of  tartaric  acid. 
Stannic  chloride  (with  which  lime  is  mixed,  the  quantity  depending  on  the  proportion 
of  acid)  acts  by  liberating  chlorine,  forming  calcium  chloride,  and  separating  tin 
hydroxide.  If  an  iron  mordant  has  to  be  removed,  stannous  chloride  is  to  be  used, 
which  dissolves  tho  iron  mordants  in  virtue  of  its  reducing  power,  whilst  stannous 
oxide  is  converted  into  stannic  oxide,  which  partly  remains  on  the  fibre.  Hence,  in 
using  tin  salts  as  a  discharge,  it  must  be  remembered  that  a  tin  mordant  takes  the 
place  of  an  iron  mordant,  and  the  colour  produced  in  the  dye  beck  will  be  modified 
accordingly. 

Discharges  are  thickened  with  gum  Senegal  and  pipe-clay  in  order  to  obtain  well- 
defined  outlines ;  for  heavy  designs,  dextrine  may  be  used. 

Discharges  are  often  combined  with  ordinary  mordants.  Thus,  if  it  is  intended  to 
produce  a  red-and-white  design  upon  a  purple  ground,  the  calico  is  padded  with  weak 
black  liquor,  and,  when  dry,  red  mordant  mixed  with  citric  acid  is  printed  on.  The 
iron  mordant  is  thus  removed  at  these  places,  and  an  aluminium  mordant  is  sub- 
stituted. A  discharge  is  printed  at  the  places  which  are  to  remain  white,  and  the  cloth 
is  cleansed  with  milk  of  lime,  dunged,  dyed  in  the  madder  beck,  and  raised. 

China-blue  Style. — This  style  (otherwise  known  as  Fayence  blue)  was  often  used 
for  producing  blue  designs  on  a  white  ground.  The  process  is  very  old,  and  has  been 
used  in  India  for  centuries.  It  is  a  topical  style,  which  can  be  effected  only  with 
indigo.  Its  peculiarity  is  that  the  indigo  is  applied  in  the  insoluble  state,  dissolved, 
and  then  fixed  on  the  fibre. 

A  very  intimate  mixture  of  finely  ground  indigo  and  copperas  is  printed  upon  a 
white  ground,  and  it  is  then  dissolved  and  reduced  by  alternate  treatment  with  lime- 
water  and  solution  of  copperas.  The  indigo  penetrates,  as  indigo-white  lime,  into  the 
fibre,  and  in  contact  with  the  air  the  indigo-white  is  oxidised  to  indigo-blue,  rendered 
insoluble,  and  thus  fixed  upon  the  fibre.  To  improve  the  action,  orpiment  is  commonly 
added,  which  acts  similarly  to  copperas  and  prevents  higher  oxidation. 

Pencil  blue  is  distinguished  from  china  blue  as  follows  : — In  the  latter,  indigo-blue 
is  printed  upon  the  fibre,  and  is  then  converted  into  indigo-white,  whilst  in  pencil  blues 
an  indigo- white,  already  prepared,  is  printed  upon  it.  To  obtain  mere  concentrated  solu- 


846  CHEMICAL  TECHNOLOGY.  [SECT,  viu 

tions,  orpiment  is  used,  which  reduces  indigo-blue  just  as  copperas  does.  The  arsenical 
or  orpiment  vat  gives  a  very  intense  colour,  which  is  thickened  with  gum,  and  applied  to 
the  tissue  by  means  of  small  pencils,  whence  the  name  pencil  blue.  Instead  of  the 
or  orpiment  vat  the  tin-crystal  vat  may  be  vised  for  the  production  of  a  pencil  blue. 

The  discharge  style  aims  at  the  local  removal  of  a  colour  already  printed  on  by 
means  of  oxidising  agents,  whilst  the  discharge  mordants  act,  not  upon  the  colouring 
matter,  but  upon  the  mordant ;  either  removing  it,  or  cancelling  its  character  as  a 
mordant. 

As  a  discharge  for  indigo  there  is  used  chromic  acid  or  ferric  chloride,  or  a 
mixture  of  potassium  ferricyanide  with  soda ;  for  madder,  chlorine  is  used. 

To  produce  a  white  design  on  a  blue  ground,  according  to  Koechlin's  process,  potas- 
sium chromate  is  used,  which,  when  decomposed  by  oxalic  or  tartaric  acid,  decolorises 
the  indigo-blue  by  supplying  oxygen,  and  converts  it  into  soluble  isatine,  whilst  the 
chromic  acid  is  reduced  to  chromium  sesquioxide.  Instead  of  chromic  acid,  Mercer 
proposes  to  destroy  the  indigo  with  a  mixture  of  potassium  ferricyanide  with  concen- 
trated caustic  soda  (Mercer's  liquid).  To  this  end  the  cloth  dyed  blue  in  the  vat  is 
saturated  with  a  solution  of  ferricyanide,  and  caustic  soda  thickened  with  starch  gum 
is  printed  on.  The  alkali  converts  the  ferricyanide  into  ferrocyanide,  and  the  indigo- 
blue  is  transformed  into  isatine  by  the  oxygen  liberated. 

In  order  to  obtain  a  white  design  upon  a  turkey-red  ground,  the  property  of  chloride 
of  lime  is  utilised,  not  to  destroy  the  colouring-matters  by  itself,  but  to  act  only  in 
proportion  as  chlorine  is  evolved  by  the  action  of  acids.  For  this  purpose  the  parts 
to  be  discharged  are  printed  with  an  acid  mordant  and  taken  through  chloride  of  lime. 

The  discharges  are  put  together  in  such  a  manner  as  to  constitute  the  mordant 
for  subsequently  dyeing  the  discharged  spots ;  they  may  also  contain  colours  to  dye 
the  decolorised  parts.  For  white  there  is  printed  on  an  acid  mixture  of  tartaric 
and  oxalic  acid  and  lime-juice  thickened  with  gum  and  pipe-clay;  for  yellow,  a 
similar  mixture  containing  lead  nitrate  and  sightened  with  a  little  potassium  chromate. 
The  calico  printed  with  the  discharge  passes  into  the  chloride  of  lime  liquor,  contained 
in  a  wooden  cistern  lined  with  sheet-lead.  On  leaving  this  cistern  the  cloth  passes 
between  a  pair  of  rollers,  when  it  is  suspended  in  flowing  water,  rinsed,  and  dried.  If 
the  discharge  contain  lead  nitrate  to  produce  white  on  a  red  ground,  the  pieces  are 
reeled  through  a  solution  of  potassium  chromate,  and,  after  rinsing,  they  are  raised  by 
a  passage  in  dilute  hydrochloric  acid. 

According  to  Steinbach,  the  solution  of  chloride  of  lime  is  printed  on  with  the 
cylinder  and  the  cloth  is  dried  on  steam  drums,  when  the  chloride  of  lime  is  converted 
into  calcium  chloride  and  chlorate,  the  latter  giving  off  oxygen  at  elevated  temperatures 
and  destroying  the  alizarine.  This  process  has  the  defect  that  the  reds  and  the  roses 
are  turned  distinctly  brown. 

For  printing  aniline  blacks  on  dyed  cottons  the  aniline-black  colour  is  made  up  with 
i^-  kilo,  potassium  chlorate  dissolved  in  40  litres  of  water ;  then  there  are  added  4  litres 
solution  of  potassium  ferrocyanide  (28  :  100)  and  2*6  kilos,  aniline  hydrochlorate  pre- 
viously mixed  with  the  quantity  of  aniline  oil  needed  for  complete  neutralisation.  The 
bleached  goods  are  taken  through  this  liquid,  dried,  oxidised  in  the  steaming-machine 
so  that  they  issue  dark  green ;  then  they  are  taken  through  a  chrome  bath  at  80°  (i  litre 
water  to  10  grammes  potassium  dichromate,  5  grammes  soda,  and  5  grammes  sodium 
chloride),  washed,  and  printed  on  as  a  discharge.  For  whites  :  10  kilos,  calcined  starch 
with  6  litres  water  and  16  kilos,  calcium  acetate  (24°  Tw.),  boiled;  then  there  are 
added  5  kilos,  sodium  acetate  and  5  kilos,  sodium-lye  at  30°  Tw.  For  yellows: 
10  kilos,  chrome  yellow  (paste),  6  kilos,  albumen  water,  2  kilos,  sodium  acetate, 
o'3  kilo,  soda-lye  at  30°  Tw.  For  reds:  16  kilos,  cinnabar,  2  kilos,  glycerine,  2  kilos. 
water,  2  kilos,  sodium  acetate,  8  kilos,  albumen  water. 


SECT,  vii.]  DYEING  AND  TISSUE-PRINTING.  847 

Steam  Colours. — For  a  long  time  there  were  known  only  two  methods  of  fixing 
colouring  -matter  on  the  fibre — i.e.,  either  the  printing  matter  was  printed  on,  which,  like 
indigo  in  the  china-blue  and  pencil-blue  styles,  had  been  made  soluble  and  was  again  sepa- 
rated on  the  fibre  as  insoluble  indigo-blue ;  or,  recourse  was  had  to  discharges,  to  discharge 
mordants,  to  resist,  and  discharge  styles,  upon  which  the  various  styles  are  founded 
which  have  been  described  in  the  previous  sections.  Not  until  1 740  was  the  attempt 
made  to  print  on  the  colouring-matters  themselves,  and  to  obtain  colours  which  were 
afterwards  known  as  application  colours.  They  did  not,  however,  bear  washing,  and  had 
so  little  fastness  that  their  general  introduction  was  attended  with  great  difficulty. 
Gradually  it  has  been  found  practicable  to  fix  them  by  steaming,  and  thus  create  the 
steam  style,  which  now  plays  so  important  a  part  in  tissue-printing. 

The  colours  almost  exclusively  used  as  steam  colours  require  the  co-operation  of  a 
mordant.  Some  of  them  are  thickened,  printed  upon  the  mordanted  cloth,  and  then 
steamed.  In  other  steam  colours  the  colouring-matters  and  mordants  are  printed 
together,  but  they  are  always  added  to  a  body  which  holds  the  lake  in  solution  or  hinders 
the  combination  of  the  colouring-matter  and  the  mordant  to  a  lake  until  the  operation 
of  steaming.  To  the  latter  class  of  bodies  belongs  stannic  chloride,  which  is  resolved 
by  watery  vapours  into  hydrochloric  acid  (which  is  either  volatilised  or  neutralised), 
and  into  stannic  oxide,  which  is  deposited  on  the  fibre.  Aluminium  chloride  acts  in  the 
same  manner.  Acetic  acid  is  also  used  in  the  production  of  steam  colours,  and  in  con- 
siderable quantity  since  the  introduction  of  artificial  alizarine.  Acetic  acid  is  added 
to  the  mass  in  order  to  keep  the  colouring-matter  in  solution  until  the  cloth  is 
steamed.  .Recently  copper  chromate  is  often  used,  and  proves  to  be  an  excellent  oxid- 
ising agent.  The  steaming  is  generally  effected  under  tension  in  the  apparatus  of 
Mather  &  Platt. 

Steam  blue  is  obtained  by  printing  a  solution  of  potassium  ferrocyanide  and 
tartaric  acid  with  small  quantities  of  sulphuric  acid,  thickened  with  starch,  drying, 
airing,  and  steaming  for  half  an  hour;  there  is  formed  hydroferrocyanic  acid,  which  is 
decomposed  at  high  temperatures,  yielding  Prussian  blue,  which  is  deposited  upon  the 
cotton  fibre. 

Steam  colours  may  also  be  obtained  from  reduced  indigo  when  the  indigo-white 
is  precipitated  by  hydrochloric  acid  from  the  copperas  vat  and  mixed  with  magnesia 
or  with  magnesium  sulphate  with  an  addition  of  alkali.  A  good  blue  may  be  ob- 
tained with  5  kilos,  precipitated  indigo,  5  litres  of  gum  water,  and  o-6  kilo,  of  mag- 
nesia. 

Steam  green  is  produced  by  mixing  blue  with  a  salt  of  lead,  printing  on  the 
mixture,  and  dyeing  up  the  cloth  after  washing  and  steaming  in  a  beck  of  potassium 
chromate. 

Steam  reds  are  at  present  obtained  with  artificial  alizarine. 

Schlieper  and  Baum  propose  a  very  curious  process  of  indigo  printing.  The  first 
step  is  the  careful  grinding  of  an  indigo  mixture  of  25  kilos,  indigo,  100  litres  water, 
50  litres  soda-lye  at  1-35  sp.  gr.,  and  58-33  kilos,  of  solid  caustic  soda.  The  colours 
consist  of — 

Dark  Blue.  Medium.  Light. 

British  gum       ....     3-00  ...  3'°°  —  3'°° 

Maize  starch     .        .        .        .     1-50  ...  i'5o  ...  i'SO 

Water 375  •••  375  -  375 

Soda-lye  (sp.  gr.  i -35)       .         .   16-00  ...  28-00  ...  40-00 

Indigo  mixture          .         .         .  30-00  ...  iS'oo  ...  6'oo 

Dark  blue  contains  55-5  grammes  indigo  per  kilo,  of  colour,  medium  blue  33^3 
grammes,  and  light  blue  in  grammes.  These  colours  are  printed  on  the  tissue,  which 
has  been  padded  with  a  solution  of  i  kilo,  glucose  in  4  litres  water  and  then  well 
Iried.  After  printing,  the  goods  are  rapidly  dried  at  from  60"  to  70°  and  then  taken 


848  CHEMICAL  TECHNOLOGY.  [SECT.  vii. 

through  a  small  steam  chest  for  from  fifteen  to  twenty  seconds,  so  that  the  indigo  is 
reduced.  They  are  then  passed  through  cold  water  for  two  minutes. 

Precipitated  sulphur  is  the  only  good  resist  under  the  new  steam  blue,  150  grammes 
sulphur  to  I  litre  of  thickening  resists  even  the  darkest  blue.  A  yellow  resist  consists 
of  220  grammes  cadmium  chloride,  140  grammes  precipitated  sulphur,  and  i  litre 
thickening. 

A  red  resist  consists  of  red  liquor,  salt  of  tin,  calcined  starch,  and  150  grammes 
sulphur  per  litre;  buff  and  similar  colours  have  from  130  to  140  grammes  sulphur 
to  i  litre  thickening. 

For  a  light  blue,  soda-lye  of  sp.  gr.  1*35  thickened  with  British  gum  and  starch  is 
printed  on  cloth  which  has  been  saturated  with  glucose,  steamed  for  fifteen  seconds,  dried, 
and  the  indigo  colour  padded  on  with  the  cylinder.  The  glucose  undergoes  a  decom- 
position under  the  action  of  the  caustic  soda,  so  that  the  colour  is  only  developed  up  to 
a  light  blue.  Yery  fine  designs  can  be  produced  in  indigo-discharge  colours  on  grounds 
dyed  in  turkey  red  or  prepared  with  turkey-red  mordant. 

For  a  turkey-red  mordant  40  kilos,  of  dry  aluminium  hydrate  is  heated  for  three 
hours  with  64  litres  soda-lye  at  60°  Tw.  It  is  made  up  with  water  to  300  litres,  neu- 
tralised with  8  litres  hydrochloric  acid  at  sp.  gr.  1-15,  and  water  added  to  make  up  a 
volume  of  620  litres. 

A  mordant  for  padding  is  obtained  by  diluting  4  litres  of  the  above  mixture  with 
i  litre  of  water.  The  cloth  padded  in  this  liquid  is  dried  on  the  drum,  when  it  turns 
yellow,  but  on  hanging  in  an  oxidation  chamber  the  original  colour  returns.  The 
pieces  are  left  till  the  following  day,  taken  through  cold  water  in  a  cistern  fitted  with 
rollers,  washed  well,  and  lastly  passed  through  a  chalk  beck  at  a  hand-heat  in  order 
to  convert  the  sodium  bi-  or  tri-aluminate  into  calcium  aluminate.  The  mordant, 
now  ready  for  dyeing,  bears  sulphuric  sours  at  n'5°  Tw.  without  losing  much  of 
its  efficacy,  and  the  red  thus  produced  behaves  similarly.  The  production  of  the 
indigo-discharge  styles  is  founded  upon  this  property.  The  tissue  thus  mordanted, 
whether  dyed  or  not,  is  prepared  in  glucose,  and  the  indigo  colour  is  then  printed 
on.  The  pieces  are  then  steamed,  washed,  aged  for  a  few  .minutes  in  the  air,  passed 
through  sulphuric  sours  at  ii'5°  Tw.  for  from  ten  to  twenty  seconds,  washed,  taken 
through  weak  soda,  and  washed  again.  The  discharged  turkey-red  pieces  are 
.soaped  at  a  boil.  The  alizarine  present  below  the  indigo  is  dissolved,  and  the  blue 
appears. 

In  order  to  obtain  white  upon  turkey  red  and  indigo-blue  the  dark  indigo  colour 
and  a  strong  soda-lye  are  printed  on,  proceeding  otherwise  as  indicated  above.  Or 
strong  soda-lye  may  be  printed  on  the  turkey-red  mordant,  steamed  to  destroy  the 
glucose,  dried,  and  the  indigo  colour  printed  on.  A  light  blue  appears  when  the 
indigo  is  superimposed  on  the  whites. 

Goppelsroder  proposes  to  produce  patterns  in  indigo  and  turkey -red  by  means  of 
electrolysis. 

In  order  to  utilise  the  mordanting  action  of  metallic  sulphides  in  steam  colours, 
Schmid  thickens  those  metallic  salts  whose  sulphides  can  be  precipitated  by  means 
of  sodium  hyposulphite  (thiosulphate)  along  with  the  latter  salt  and  the  colouring 
matter,  and  prints  them.  On  steaming,  an  insoluble  sulphide  is  precipitated,  and  along 
with  it  the  colouring  matter.  In  this  manner  there  may  be  fixed  in  one  operation  the 
cadmium,  lead  and  copper  sulphides,  methylene  blue,  malachite  green,  dimethylaniline 
violet,  &c.  The  tones  obtained  correspond  to  those  of  the  sulphides  and  the  colouring 
matters  employed.  Thus,  cadmium  sulphide  with  methylene  blue  forms  a  green  ;  with 
aniline  green,  a  yellowish  green  ;  &c.  These  colours  bear  soaping  fairly  well.  A  bright 
yellowish  steam  green  is,  e.g.,  obtained  with  950  grammes  tragacanth  mucilage  (200 
grammes  per  litre),  200  grammes  crystalline  cadmium  nitrate,  30  grammes  crystal 


SECT.  VIL]  DYEING   AND  TISSUE-PRINTING.  849 

lised  sodium  thiosulphate,  20  grammes  malachite  green,  10  grammes  acetic  acid  at 
10°  Tw.,  and  150  c.c.  water. 

Along  with  the  steam  styles  rank  the  processes  used,  both  in  printing  and  dyeing, 
to  produce  a  metallic  appearance  on  tissues.  This  operation  is  called  coppering.  The 
cloth  is  covered  with  an  exceedingly  thin  layer  of  metallic  sulphide,  when  the  colour 
comes  up  in  thin  layers,  resembling  the  elytra  of  certain  beetles. 

According  to  Barlow's  process,  the  pieces  are  steeped  in  a  solution  of  copper  acetate 
or  nitrate,  or  corresponding  salts  of  lead,  or  bismuth,  pressed,  washed,  and  then 
steamed  for  five  to  thirty  minutes,  hydrogen  sulphide  being  mixed  with  the  steam. 
After  steaming,  the  goods  are  washed  and  dried. 

Topical  or  application  colours  include  such  as  are  fully  formed  when  printed,  and 
are  freed  from  the  thickenings  and  acid  salts  by  washings,  so  that  the  colours  appear 
intimately  combined  with  the  fibre.  Some  such  colours  (I.)  are  applied  in  solution  and 
gradually  pass  into  the  insoluble  state  upon  the  fibre,  and  thus  become  combined  with 
it  and  rendered  able  to  resist  washing.  Others  (II.) — indeed,  the  most — are  printed 
in  the  insoluble  state,  and  are  thickened  with  plastic  substances,  by  means  of  which 
they  adhere  to  the  fibre.  The  chief  difficulty  in  producing  such  colours  consists  in  find- 
ing thickeners  which  give  the  colours  the  violet  lustre,  and  which  best  resist  water. 

Examples  of  Class  I.  ("  Spirit  Colours  "). — According  to  Schmid,  we  obtain,  e.g.,  a 
fine  soap-fast  chrome  yellow  by  printing  250  grammes  tragacanth  water  (200  grammes 
per  litre),  250  grammes  lead  nitrate,  5  50  grammes  barium  chromate,  and  50  grammes 
water,  and  subsequent  steaming.  Red  and  rose  are  obtained  from  red  wood  and  a 
mixture  of  stannic  and  stannous  oxides.  The  red  wood  (generally  sapan)  is  used 
either  as  a  decoction  or  as  a  solution  of  the  solid  extract,  to  which  a  preparation 
of  tin. is  added,  or  a  lake  is  made  of  the  red  wood  and  dissolved  in  stannous  chloride. 
The  oxide  of  tin,  separated  from  the  tin  compound,  deposits  on  the  fibre  and  gradually 
takes  up  the  colouring  matter. 

Madder  lakes  are  also  often  used  for  obtaining  such  colours. 

A  topical  black  is  often  obtained  from  a  decoction  of  logwood  and  galls,  thickened, 
and  mixed  with  an  iron  mordant. 

The  second  group  of  these  colours  (pigment  style)  includes  those  which  are  applied 
in  an  insoluble  state  ground  up  with  albumen  or  with  an  oil  varnish.  Such  colouring 
matters  are  ultramarine,  umber,  chrome  yellows,  Guignet's  green,  vermilion,  shearings 
from  dyed  woollen  cloth,  metallic  powders,  &c.  As  examples  may  be  mentioned  ultra- 
marine and  gold  and  silver  printing. 

In  the  use  of  ultramarine  in  printing,  the  earliest  agent — at  once  for  fixing  and 
for  thickening — was  albumen,  often  mixed  with  gum  Senegal,  both  from  economical 
reasons  and  that  the  mixture  may  print  more  easily.  Some  printers  fix  ultramarine 
simply  by  a  passage  through  boiling  water,  and  thus  obtain  purer,  but  less  saturated, 
colours  than  by  steaming.  But  fixation  by  steam  is  necessary  if  other  pigments,  such 
as  Schweinfurt  green  or  violet  lakes,  are  to  be  fixed  along  with  the  ultramarine. 
Chrome  orange  and  chrome  green  require  peculiar  care,  as  all  substances  must  be 
avoided  which  tend  to  convert  copper  or  lead  into  sulphides.  Colours  containing  oils 
are  to  be  rejected,  as  well  as  acids  and  acidifiable  substances  which  may  decompose  the 
albumen  and  evolve  from  it  hydrogen  sulphide. 

For  printing  with  gold  and  silver,  isinglass  is  dissolved  in  water  and  brandy ;  on  the 
other  hand,  powdered  mastic  is  dissolved  in  alcohol,  and  the  two  are  mixed.  Red  bole, 
previously  ground  up  with  brandy,  is  stirred  into  the  mixture,  which  then  serves  as  a 
ground  for  gold.  For  silver,  pipe-clay  is  used  instead  of  bole,  and  the  mixture  is  printed 
in  the  ordinary  manner.  Immediately  after  printing,  leaf  gold  or  silver  is  applied  to 
the  printed  parts,  which  are  then  pressed  down  with  cotton.  When  dry,  the  superfluous 

3  H 


850  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

metal  is  removed  with  a  brush.  In  order  to  print  with  a  metallic  powder,  such  powder 
is  stirred  into  the  above-mentioned  mixture  instead  of  the  bole  or  pipe-clay.  Or  the 
requisite  parts  of  the  design  are  moistened  with  a  solution  of  gold,  which  is  then  con- 
verted into  the  reguline  state  by  means  of  reducing  agents. 

Printing  with  Coal-tar  Colours. — These  colours  may  be  printed  and  fixed  upon 
cotton  tissues  in  several  manners.  Either  (i)  the  thickened  mordant  is  printed  on,  fixed 
by  drying  and  airing  or  by  steaming,  and  afterwards  dyed  in  a  beck  of  the  colouring 
matter,  when  the  colour  attaches  itself  only  to  the  mordanted  places.  If  it  is  desired 
to  keep  the  ground  clean,  the  mordant  is  padded  on  locally.  Or  (2)  the  mordant  is  mixed 
with  the  dye,  thickened,  printed,  dried,  and  steamed.  After  printing,  the  pieces  are 
washed  and  dried. 

The  substances  used  as  mordants  are  numerous — albumen  (egg  or  blood),  preparations 
of  gluten,  caseine  dissolved  in  caustic  alkali  or  in  acetic  acid,  gelatine  or  tannate  of 
gelatine,  tannin,  fatty  oils  and  preparations  of  oils  (sulpholeic  acid,  sulphopalmitic  and 
sulphoglyceric  acids),  and  certain  gum-resins,  e.g.,  shellac  dissolved  in  borax. 

In  aniline  printing  by  means  of  gluten,  the  gluten  of  wheat  is  left  to  itself  until  it 
becomes  slimy.  It  is  then  saturated  with  sodium  carbonate  and  thus  rendered  in- 
soluble, washed,  redissolved  in  caustic  soda  at  sp.  gr.  ro8,  and  the  solution  is  diluted. 
When  the  cloth  has  been  printed  or  padded  with  this  liquid  and  dried,  it  is  steamed  and 
rinsed.  The  solution  of  the  aniline  colour  is  then  used  as  a  dye  beck  through  which 
the  pieces  are  taken.  Or  the  colour  is  printed  upon  the  cloth  prepared  as  before,  which 
is  then  steamed  again. 

According  to  certain  colour  manufacturers  (not  named),  levulates  of  the  colouring 
bases  or  mixtures  of  levulic  acid  with  the  colouring  matters  may  be  used  for  printing. 
Such  mixtures  are  obtained  by  grinding  in  a  wet  mill  levulic  acid  with  the  colouring 
base  (dry,  or  preferably  rather  moist)  until  a  complete  mixture  is  obtained.  Thus  the 
goods  may  be  printed  with  the  following  mixture  : — 

183  parts  printing  blue  (induline)  as  a  25  per  cent,  paste 
500     .,     levulic  acid 
40     .,      emulsion  of  oil 
630     ,,      acetic-starch  thickening 
100     „      tragacanth  tannin  (50  parts  tragacanth  mucilage  and  50  parts 

tannin), 
developing  the  colour  by  steaming  the  printed  cloth. 

"  Levuline  "  blue  is  obtained  by  adding  i  part  moist  induline  base  to  3  parts  levulic 
acid  and  mixing  intimately. 

According  to  Botsch,  the  Congo  colours  are  prepared  for  printing  as  follows : — 

Benzoazurine  Steam  Blue. 

Water 750  parts 

Wheat  starch 100    „ 

Benzoazurine  G-   ) 50    „ 

Water     .        .     j 250    „ 

Chrysamine  Steam  Yellow. 

Water  750  parts 

Wheat  starch .  100    „ 

Chrysamine    ) •  50    „ 

Water  / 250    „ 

These  colours  are  printed  on  prepared  cloth,  yielding  respectively  blue  or  yellow,  or 
by  a  mixture  of  the  true  indigo-blue  to  olive  according  to  the  proportions ;  a  very  nice 
blue  may  be  produced  by  adding  Victoria  blue  B  or  Nicholson  blue  6B.  The  goods 


SECT,  vii.]  DYEING  AND  TISSUE-PRINTING.  851 

•are  steamed,  according  to  shade,  from  thirty  minutes  to  an  hour.  These  colours  are  all 
fast,  especially  if  chrysamine  predominates.  They  may  also  be  used  for  wool.  The 
stilbene  dyes  (Leonhardt  &  Co.)  may  be  used  in  the  same  manner. 

In  fixing  by  means  of  chrome,  the  following,  e.g.,  colour  may  be  used  for  blue : — 

Indophenol 2000  grammes 

Acetic  acid  (8*25  Tw.) 10  litres 

Tin  acetate  (31°  Tw.) 10    „ 

Gum 8000  grammes 

'The  mixture  is  boiled  and  stirred  for  half  an  hour.  After  printing,  the  goods  are  aged 
for  twenty-four  hours,  steamed  fortwe  minutes,  preferably  in  Mather  &  Platt's  apparatus, 
chromed  at  50°  for  two  minutes  in  a  beck  of  10  grammes  potassium  dichromate  per 
litre  water,  lastly  washed  and  soaped.  Indophenol  is  less  advantageous  than  the  two 
following  colours. 

If  gallocyanine  (from  gallic  acid)  is  used,  excellent  results  are  obtained  with  the 
following  mixture : — 

Wheat  starch 150  grammes 

Gallocyanine  paste  (commercial)        .  .        i  litre 

Tragacanth  mucilage          .        .  .        .         075  litre 

Acetic  acid  (i o°  Tw.) 0-25    „ 

Turkey-red  oil 0*25    „ 

Boil,  stir  till  cold,  and  add  ^  litre  chrome  acetate  at  50°  Tw.  and  60  grammes  potassium 
ferrocyanide.  The  colour  is  printed,  steamed,  and  treated  as  usual. 

For  alizarine  blue  there  are  used  120  grammes  of  a  solution  containing  too  grammes 
starch  per  litre  of  water,  15  to  20  grammes  alizarine  blue  S,  and  30  to  40  grammes 
.solution  of  chromium  acetate  (14°  Tw.).  In  place  of  starch,  tragacanth  or  gum  may  be 
used  as  a  thickener.  The  printed  pieces  may  be  steamed  without  pressure  for  ten  to 
twenty  minutes,  when  the  blue  is  found  fully  developed  and  the  pieces  are  washed, 
soaped,  and  dried.  The  steaming  may  be  effected  in  two  or  three  minutes  in  the 
continuous  apparatus.  If  the  bisulphite  compound  of  alizarine  blue  is  used,  the  colour 
in  the  beck  is  completely  used  up.  The  colour  produced  resists  light,  soap,  and  chlorine, 
and  is  in  this  respect  faster  than  indigo.  Soluble  alizarine  blue  has,  in  point  of  fact, 
superseded  both  indigo  and  ultramarine  in  a  variety  of  applications. 

Propiolic  acid  is  now  little  applied. 

Auramine  is  printed  with  tannin  and  tartaric  acid  upon  vegetable  fibre  ;  the  colour 
is  very  fine. 

Printing  with  aniline  black  has  been  previously  mentioned. 

Attempts  have  been  made,  especially  by  T.  Holliday  &  Sons,  to  produce  azo  colours 
directly  upon  the  fibre,  and  these  experiments  have  been  attended  with  encouraging 
results. 

Finishing. — After  printing,  the  goods  are  finished — i.e.,  taken  through  starch  becks 
to  give  the  cloth  more  firmness,  dried,  folded,  and  pressed.  In  finishing  furniture 
prints,  white  wax  or  paraffine  is  added  to  the  solution  of  starch.  In  order  to  give 
printed  muslins  the  admired  velvety  feel,  there  is  added  to  the  starch,  whilst  boiling  in 
water,  a  small  quantity  of  spermaceti,  paraffine,  or  stearic  acid. 

Linen-printing  is  confined  to  the  production  of  vat-blue  cloths  with  light  blue  or 
•white  designs, 

In  woollen  and  worsted  printing,  topical  styles  are  in  use,  and  the  colours  are  fixed 
•by  steaming.* 

For  producing  a  discharge  blue  upon  azo  colours,  the  woollen  tissue  is  first  dyed 

*  Space  does  not  allow  a  description  of  the  methods  used  for  printing  mixed  cotton  and  woollen 
goods. 


852  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

with  ponceau  or  any  desired  azo  colour.  A  mixture  of  solid  violet,  indophenol,  arid  an 
alkaline  reducing  agent  is  then  printed  and  steamed ;  the  azo  colour  undergoes  the 
characteristic  splitting  up  on  reduction,  whilst  the  blue  colouring  matters,  reduced 
to  leuko  compounds,  penetrate  into  the  fibre,  and,  on  subsequent  exposure  to  the  air, 
reproduce  an  insoluble  fast  blue  on  a  red  ground.  The  following  is  the  composition  of 
the  colour : — 

Indophenol  in  powder 4  kilos. 

Tin  pulp 10  litres 

Thick  dextrine  water  (2^  kilos,  per  litre)         .        .        .14 

Water 6 

Soda  crystals 4 

Solid  violet,  B.S 10 

Glycerine 5 

The  mixture  is  heated  to  60°  for  half  an  hour  until  completely  reduced,  which  is 
shown  by  the  yellowish  colour  of  the  mixture.  It  is  then  printed,  steamed,  and  fully 
developed  by  ageing. 

The  processes  of  silk-printing  are  generally  the  same  as  those  of  cotton -printing, 
but  greater  care  has  to  be  taken  to  keep  the  whites  clear.  Either  topical  colours  are 
applied  and  fixed  by  steaming,  or  various  mordants  are  printed  and  dyed  in  the  beck 
as  in  the  madder  style. 

A  peculiar  style  of  silk-printing  is  founded  on  the  property  of  nitric  acid  to  colour 
silks  and  woollens  a  permanent  yellow,  to  destroy  most  colours,  but  to  act  upon  fats 
and  resins  only  after  some  time.  This  kind  of  printing  is  called  mandarining.  In 
order  to  effect  a  yellow  discharge  on  vat-blue  grounds,  the  silks  are  printed  with  a 
resist  of  resin  and  fat,  steeped  for  two  to  three  minutes  in  an  acid  flot  of  i  part  water 
and  2  parts  nitric  acid  at  50°,  and  placed  in  running  water.  After  this  operation  the 
silk  is  boiled  off  in  a  soap  bath  mixed  with  potash.  The  parts  which  have  not  been 
resisted  are  of  a  fine  yellow. 

Examination  of  Dyed  and  Printed  Textiles. — In  order  to  test  the  fastness  of  the 
dye,  the  sample  is  first  rubbed  upon  white  paper,  which  must  not  be  stained  in  the 
slightest.  To  pure  water  it  must  give  off  no  colour.  To  ascertain  the  effect  of  heat,  a 
swatch  is  laid  between  white  papers  and  smoothed  with  a  flat  iron.  To  find  the  action, 
of  light,  the  swatch  is  covered  with  a  piece  of  black  pasteboard,  or  of  sheet  metal  in 
which  two  round  holes  have  been  cut,  and  thus  exposed  to  the  sun  or  to  an  electric  light. 

Colours  which  appear  unchanged  after  they  have  been  steeped  in  10  per  cent, 
solutions  of  sulphuric  acid,  caustic  soda,  and  ammonia  may  be  pronounced  fast.  Fast 
colours  should  not  be  altered  by  boiling  for  half  an  hour  in  a  i  per  cent,  solution  of 
soap. 

Whether,  in  the  production  of  printed  calicoes,  the  colour  has  been  generated  within 
the  fibre,  or  whether  it  has  been  applied  pre-formedand  fastened  by  means  of  albumen, 
or  whether  both  these  procedures  have  come  into  play,  can  best  be  determined  by 
means  of  the  microscope. 

If  the  tissue  is  teased  out  with  a  needle  so  far  that  the  individual  fibrillse  are 
isolated,  these  latter  appear  uniformly  coloured  and  translucent  if  the  materials 
forming  the  colour  have  been  applied  in  a  dissolved  state.  In  many  colouring  matters 
there  appears  a  granular  texture,  the  characteristic  form  of  the  fibre  is  unchanged,  and 
the  colouring  matter  appears  everywhere  uniformly  deposited  within  it.  In  the 
albumen  processes  the  fibre  is  not  dyed,  but  at  numerous  points  there  appear  single 
coloured  rays  of  coagulated  albumen  adhering  externally.  Here  and  there  such  may 
be  seen  detached  from  the  fibre  in  consequence  of  the  maceration. 

Lenz,  Martin,  Hummel,  and  Lepetit  have  given  instructions  for  detecting  the 
colouring  matters  on  the  fibre.  (See  page  854,  et.  seq.}  The  following  reagents  are 


BECT.  vii.]  DYEING   AND   TISSUE-PRINTING.  853 

employed: — Sulphuric  acid  154°  Tw.,  hydrochloric  acid  32°  Tw.,  soda-lye  at  10  per 
cent.,  the  strongest  ammonia,  and  equal  parts  of  concentrated  hydrochloric  acid  and 
stannous  chloride  (pp.  854-861). 

For  further  information  on  the  tinctorial  industries,  the  reader  is  referred  to  : — 
A  Practical  Handbook  of  Dyeing  and  Calico-printing.  By  William  Crookes,  F.R.S.  London : 
Longmans,  Green  &  Co.— Dyeing  and  Calico-printing.  By  the  late  Dr.  F.  Crace-Calvert,  F.K.S. 
Edited  by  Dr.  J.  Stenhouse,  F.R.S.,  and  C.  E.  Groves,  F.C.S.  (London  and  Berlin.)  Manchester : 
Palmer  &  Howe.— Dyeing  and  Tissue-printing.  By  W.  Crookes,  F.R.S.  London  :  G.  Bell  &  Sons. — 
The  Dyeing  of  Textile  Fabrics.  By  J.  J.  Hummel,  F.C.S.  London:  Cassell  &  Co.  (Limited.)— 
Dyeing  :  comprising  tJie  Dyeing  and  Bleaching  of  Wool,  Silk,  Cotton,  <&c.  By  Antonio  Sansone. 
London:  Hamilton,  Adams  &  Co.;  Manchester:  A.  Heywood  &  Son.— The  Printing  of  Cotton 
Fabrics.  By  Antonio  Sansone.  London  :  Hamilton,  Adams  &  Co.  ;  Manchester  :  A.  Heywood  & 
Son. — Chemistry  of  the  Coal-tar  Colours.  By  Dr.  R.  Benedikt  and  Dr.  E.  Knecht.  London  :  G.  Bell 
&  Sons. — Anthracene :  its  Constitution,  Properties,  Manufacture,  and  Derivatives,  with  their  Applica- 
tions in  Dyeing  and  Printing.  By  G.  Auerbach.  Edited  by  W.  Crookes,  F.R.S.,  &c.  London : 
Longmans,  Green  &  Co.— Manual  of  Colours  and  Dyewares.  By  J.  W.  Slater.  London  :  Crosby 
Lockwood,  &  Co. — Dictionary  of  Calico-printing  and  Dyeing.  By  C.  O'Neill.  London  :  Simpkin, 
Marshall  &  Co. 

PAPER  MANUFACTURE. 

History  of  Paper. — Paper  is  in  reality  a  thin  felt  of  vegetable  fibres,  mechanically 
and  chemically  clarified,  crushed,  and  torn  into  a  pulp  suspended  in  water.  This  pulp 
is  spread  equally  in  thin  layers,  drained,  pressed,  and  dried  into  the  compact  substance 
we  call  paper. 

Materials  of  Paper  Manufacture. — The  chief  materials  of  paper  manufacture  are 
the  waste  rags  from  flax,  hemp,  silk,  wool,  and  cotton.  The  linen  rags  are  mostly  in 
request  for  making  the  best  and  most  durable  white  writing  and  printing  paper.  Silk 
and  woollen  rags  are  unfit  for  this  purpose,  as  the  bleaching  material  will  not  act  upon 
animal  substances.  Cotton  in  a  raw  state  requires  less  preparation  than  hemp.  Bags 
are  classed  under  different  denominations — fines,  seconds,  and  thirds,  the  latter  com- 
prising fustians,  corduroys,  stamps,  or  prints,  as  they  are  technically  termed.  The 
waste  refuse  from  the  wadding  machine  used  in  cotton  spinning  is  employed  for 
scribbling  paper.  Bibulous  papers,  such  as  blotting  and  filter  papers,  are  made  from 
woollen  rags,  on  account  of  their  open  texture ;  cotton  rags,  also,  make  a  spongier, 
looser  paper  when  unmixed  with  linen. 

Substitute  for  Rags. — The  consumption  of  paper  in  Europe  has  more  than  doubled 
within  the  last  fifty  years,  and,  owing  to  the  insufficient  supply  of  rags,  substitutes  had 
to  be  found  in  straw  and  wood.  The  Chinese  first  used  vegetable  pulp  for  paper 
manufacture.  The  inner  bark  of  the  bamboo  is  particularly  celebrated  as  affording  a 
paper  yielding  the  most  delicate  impressions  from  copper-plate,  and  this  paper  was 
originally  called  India-proof.  The  Chinese  also  use  the  bark  of  the  mulberry  and  elm 
trees,  hemp,  rice-straw,  and  wheat.  Among  the  straw  species  appears  the  maize 
(Indian  corn),  from  the  fibre  of  which  a  paper  is  made  that  for  purity  and  whiteness 
cannot  be  equalled.  Also  the  Andropogon  glycichylum,  or  Sorghum  saccJiaratum,  a 
native  of  North  America,  is  used.  In  fact,  nearly  every  species  of  tough  fibrous 
vegetable,  and  even  animal,  substance  has  been  tried ;  but  of  these  straw  has  been 
most  successfully  applied,  in  combination  with  linen  and  cotton  rags,  when  the  silica 
contained  in  the  straw  is  destroyed  by  means  of  a  strong  alkali.  If  the  straw  is  not 
properly  prepared  the  paper  will  be  brittle  and  unfit  for  use.  The  use  of  straw  is  not 
very  extensive,  owing  to  the  extra  expense  of  preparation,  and  its  waste  under  the 
process. 

Esparto  grass  (the  fibre  of  the  Macrochloa  tenacissvma)  and  certain  soft  woods  are 
very  extensively  used. 

Straw,  chopped  up,  is  boiled  with  soda-lye  in  a  revolving  boiler,  and  is  then  washed 


854 


CHEMICAL  TECHNOLOGY. 


[SECT.  vii.. 
Red  Colouring- 


Colouring  Matter. 

HC1. 

H,SO*. 

. 

NaOH. 

Orseilline  B  B. 

Fibre  violet-black,   then 

Fibre  black-blue  ;  liquid 

Fibre  violet  ;  liquid 

(Bayer  &  Co.) 

black  ;  liquid  faint  in- 

indigo,   reddish    violet 

reddish  violet. 

digo. 

with  water 

Congo  red 

Dilute  HC1  :  Fibre  blue- 

Fibre    blue-black  ;     dis- 

Fibre scarcely 

(Berlin  Aniline  Co.) 

black. 

solves    dark    blue    on 

changed. 

Strong    HC1  :     Liquid 

stirring. 

colourless 

Benzopurpurine  I-B. 

Dilute  :  Fibre  red  -brown  ; 

Fibre  black-blue  ;  liquid 

No  action. 

liquid  colourless. 

do.,  on    dilution    red- 

Strong:      Fibre     dark 

black. 

brown. 

Benzopurpurine  II-B. 

Dilute  :  Fibre  blue-black  ; 

Fibre  black-blue  ;  liquid 

No  action. 

liquid  colourless. 

dark  blue,  blue  on  dilu- 

tion. 

Delta  purpurine  G. 

Dilute  :  Fibre  brown-red  ; 

Fibre  blue-black  ;   liquid 

No  action. 

liquid  colourless. 

dark  blue,  on  dilution 

Strong  :    Fibre   greenish 

grey,  then  red-brown. 

black. 

Delta  purpurine  56. 

Dilute:  Fibre  red-brown. 

Fibre      dark     brownish 

No  action. 

Strong  :      Fibre  olive- 

olive;  liquid  dirty  green, 

black. 

turning      reddish      on 

dilution. 

Brilliant  Congo. 

Dilute  :  Fibie  red-brown  ; 

Fibre  blue-black  ;  liquid 

No  action. 

liquid  colourless. 

blue,  on  dilution  purple- 

Strong  :     Fibre    reddish 

violet. 

black-  violet. 

Direct  red. 

Dilute  :     Fibre   black- 

Fibre  black-blue  ;  liquid 

Fibre  darker  and 

violet. 

black-violet,    grey-blue 

rather  bluer  ; 

Strong  :  Fibre  blue  ;  liquid 

on  dilution. 

liquid  faint  brown- 

colourless. 

red. 

Naphthylene  red. 

Fibre  dark  black-green. 

Fibre    and    liquid  blue- 

Scarcely  any  action. 

black. 

Eosazurine  B. 

Dilute:  Fibre  dark  purple- 

Fibre    and    liquid    dark 

No  action. 

red. 

blue,   on  dilution  red- 

Strong :  Olive-green. 

dish,  and  then  greenish. 

Congo-Corinth. 

Fibre  black. 

Fibre  black  ;  liquid  dark 

Fibre  redder  ;  liquid! 

blue,  blue  on  dilution. 

colourless  ;  wash- 

ing restores  ori- 

ginal colour. 

Hessian  purple  N. 

Dilute  :     Fibre      black  ; 

Fibre  black  ;  liquid  blue, 

No  action. 

liquid  colourless. 

on  dilution  grey-blue. 

Hessian  purple  B. 

Strong:  Fibre  dark  grey, 

Fibre  grey-black  ;  liquid 

No  action  ;  liquid 

nearly  black. 

faint  blue. 

faint  rose. 

Azarine  S. 

Fibre      gradually     dark 

Fibre  darker  ;  liquid  fine 

Fibre  more  blue  ; 

brown-red  ;       liquid 

red  ;  on  dilution  both 

liquid  bright 

scarcely  coloured.     On 

yellow. 

cherry-red. 

dilution  colour  of  fibre 

restored. 

Azoeosine. 

Fibre   deep     red-violet  ; 

As  with  HC1. 

Fibre  dirty  orange. 

liquid  scarcely  lilac. 

Water  restores  colour. 

Carmosine. 

Dilute  :  no  action. 

Fibre     violet-black  ;     li- 

Fibre rather  browner;  : 

Strong  :  Fibre  deep  red- 

quid  the  same. 

liquid  light  rose. 

violet  ;     liquid   faint 

lilac.    Washing  restores 

original  colour. 

*  All  the  colours  unattacked  by  NaOHT 


SECT.  VII.] 

Matters. 


DYEING  AND  TISSUE-PRINTING. 


855 


NH3. 

SnCl2+HCl. 

Alcohol. 

Other  Reactions  and  Remarks. 

Like  NaOH. 

Fibre  decol.   slowly 

No  action. 

UNO,  :  Violet  spot,  disappears 

in  cold,  quickly 

on  washing. 

boiling. 

No  action. 

Fibre  blue-black, 

No  action. 

HNO,  :  Blue-black  spot  ;  red 

then  blue,  then 

restored  by  NHS. 

grey,  then  dis- 

HN02 :     Fibre      red-brown, 

charged. 

colour  not  restored  by  NH,  ; 

liquid  becomes  bluish  red. 

No  action. 

Fibre  brown-red, 

Traces  of  colour 

HNO2:  Fibre  brown-black, 

then  rose,  then 

extracted. 

Picric  acid:  Fibre  red-brown.* 

discharged. 

No  action. 

Fibre  blue-  black, 

No  action. 

HN02:  Fibre-violet  black,  then 

then  pale  grey, 

more  violet. 

then  discharged. 

Picric  acid  :  Fibre  dark  brown 

No  action. 

Fibre  dark  brown. 

No  action. 

HNO2  :     Fibre   violet-black  ; 

then  lighter,  then 

violet  red  with  NHS. 

rose,  lastly  dis- 

Picric acid  :  Fibre  brown-red. 

charged. 

No  action. 

Fibre  cinnamon 

A  little  colour  ex- 

brown, then  slowly 

tracted. 

discharged. 

No  action. 

Fibre  red-  brown, 

Trace  of  colour 

HN02:     Fibre    black;    with 

then  discharged. 

extracted. 

NH,  black-violet. 

Picric  acid  :  Fibre  brownish. 

Fibre  fiery  red  ; 

Discharged. 

No  action. 

HN02  :  Fibre  red-brown  ;  not 

liquid  scarce 

changed  by  NH3. 

reddish. 

Picric  acid  :  A  brown  spot. 

Extracts  dye  slightly 

Fibre  black,  then 

Liquid  faint  rose. 

HN03  :  Blue  spot  with  green 

that  change  of 

grey,  then  dis- 

margin. 

colour. 

charged. 

HNO2  :  Fibre  yellow-brown  ; 

NaOH    turns    the    washed 

fibre  dark    brown  ;    liquid 

light  brown. 

No  action. 

Fibre  deep  purple- 

Some  colour  ex- 

HNO2 :  Dark  yellow-grey,red- 

red,  then  discharged. 

tracted,  red. 

brown     on     washing,    and 

touching  with  NHg. 

Fibre  redder  ;  liquid 

Fibre  black,  then 

Liquid  scarcely  rose- 

HNO2  :     Fibre     black-blue  ; 

pale  rose. 

blue-grey,  and 
discharged. 

coloured. 

turns      dark     magenta-red 
on  touching  with  NH3. 

No  action. 

Fibre  black,  then 

Liquid  scarce 

HN02:     Fibre   violet-black; 

colourless. 

coloured. 

dark  red-brown  with  NHr 

Picric  acid  :  Fibre  brown. 

Liquid  pale  rose. 

Fibre  reddish  grey, 
then  colourless. 

No  action. 

HNO2:  Fibre  dark  violet  ;  with 
NHS  red-brown. 

Like  NaOH,  but 
fainter. 

Fibre  yellow  on  boil- 
ing ;  liquid  yellow. 

Liquid  scarce  rose. 

Smells  of  alizarine   oil  ;  ash 
contains  tin. 

HNOj  :  No  action. 

HN03:  Orange  spots.  If  NH3is 

addedtothe  yellow  li  quor  with 

SnCl,  and  HC1,  turns  violet. 

Fibre  scarlet  ;  liquid 
scarcely  coloured. 

Very  slight  action  in 
cold  ;  on  heating 

No  action. 

HNOS  :  Brown  spot,  removed 
by  washing. 

fibre  colourless, 

Fibre  unchanged  ; 
liquid  rose. 

liquid  colourless. 
Slight  action  in  cold, 
discharged  on 

No  action. 

HNOS  :     Violet-brown     spot, 
removed  by  washing. 

boiling. 

are  strongly  attacked  by  hot  soap-lye. 


856 


CHEMICAL  TECHNOLOGY. 


[SECT.  vii. 


Colouring  Matters. 

HC1. 

H2S04. 

NaOH. 

Rhodamine. 

Fibre     dirty    brick-red  ; 

As  with  HC1. 

Fibre  rather  darker 

liquid  colourless.   Fibre 

and.  bluer  ;  liquid 

restored  by  washing. 

colourless. 

Primuline  red. 

Fibre  dark    red-brown  ; 

Fibre  black-violet  ;  liquid 

Fibre  dirty  red- 

liquid  faint  red-brown. 

dirty  do.,  red  on  dilu- 

brown. 

tion. 

Alizarine  S. 

Fibre    orange;     liquid 

Fibre        orange-brown   ; 

Fibre  and  liquid 

light  orange. 

liquid    orange,    yellow 

violet. 

on  dilution. 

Alizarine  S.  (purple 

Fibre   brownish  yellow  ; 

Fibre      brown  ;      liquid 

Fibre  and  liquid 

shade  with  bi- 

liquid yellow. 

brown-red,    yellow    on 

violet. 

chromate). 

dilution. 

Yellow  Colouring 

Quinoline  yellow. 

Fibre     yellow  ;      liquid 

As  with  HC1.    . 

Fibre  deeper  yellow, 

colourless,    colour     re- 

then discharged, 

stored  by  water. 

restored  by  H2O. 

Auramine. 

Fibre  nearly  discharged  ; 

Fibre  discharged  ;  liquid 

Fibre  and  liquid 

liquid    colourless,   yel- 

colourless. 

colourless,  yellow 

low  partly  restored  by 

colour  partly 

dilution. 

restored  by  H20. 

Chrysamine. 

Dilute  :    Fibre  pale  yel- 

Fibre     magenta  -red: 

Fibre  dark  orange  ; 

low. 

liquid  red-violet. 

liquid  scarcely 

Cone.  :  Fibre  red-brown  ; 

coloured. 

liquid  rose  yellowed  on 

dilution. 

Chrysophenine. 

Dilute  :  No  action. 

Fibre  brown,  then  deep 

Fibre  unchanged  ; 

Con.  :  Fibre  black-violet 

violet  ;  blue  on  dilution. 

liquid  scarcely 

liquid  scarcely  coloured. 

yellowish. 

Hessian  yellow. 

Dilute  :  Fibre  paler. 

Fibre  deep  violet  ;  liquid 

Fibre  dark  red  ; 

Con.  :    Fibre  black-blue  ; 

red  violet. 

liquid  light  rose. 

liquid  violet. 

Brilliant  yellow. 

Dilute  :  No  action. 

Fibre  black-violet  ;  liquid 

Fibre  cherry-red  ; 

Cone.:  Fibre  dark  yellow; 

violet. 

liquid  scarcely  rose. 

liquid  nearly  colourless. 

Curcumine. 

Dilute  :  No  action. 

Fibre  black-violet  ;  liquid 

As  in  brilliant  yellow. 

Cone.  :  Fibre  dark  violet  ; 

fine    violet  ;     blue     on 

liquid  nearly  colourless. 

dilution. 

Ta*irazine. 

Fibre  more  orange  ;  liquid 

Same  as  HC1. 

Fibre  more  orange  ; 

yellow. 

liquid  orange- 

yellow. 

Citronine. 

Fibre    deep    violet-red  ; 

Fibre  deep-violet  ;  liquid 

Fibre  dirty  green- 

liquid  magenta  on  dilu- 

violet. 

yellow  ;  liquid 

tion. 

colourless,  yellow 

with  water. 

Primuline  yellow. 

No  perceptible  action. 

Fibre  first  brighter  and 

Fibre  brighter  and 

deeper,       then     pale 

more  orange  ;  liquid 

yellow. 

colourless. 

Toluylen  orange  G. 

Dilute  :  No  action. 

Fibre  magenta-red  ;  liquid 

Fibre  light  orange- 

Cone.  :      Fibre    violet  ; 

not  much  reddened. 

red  ;  liquid  scarcely 

liquid  reddish,  on  dilu- 

coloured. 

tion  colour  restored. 

Toluylen  orange  R. 

Dilute  :  Fibre  more  rose. 

Fibre  yellowish  ;   liquid 

Fibre  more  orange  ; 

Cone.  :  Fibre  paler  liquid 

yellow. 

liquid  colourless. 

yellow  ;     on     dilution 

rose. 

Primuline  orange. 

Fibre  and  liquid  reddish 

Fibre       orange  brown  ; 

Fibre  darkred-brown  ; 

brown. 

liquid  deep  red. 

liquid  nearly  colour- 

less. 

Oriol. 

Dilute  :  No  action 

As  with  HC1. 

Fibre  orange-red  ; 

Cone.  :   Fibre  dark  red  ; 

liquid  colourless. 

liquid    light  red,    yel- 

low on  dilution.     • 

SECT.   VII.] 


DYEING  AND   TISSUE-PRINTING.* 


857 


NH3. 

SnCl2+HCl. 

Alcohol. 

Other  Reactions  and  Remarks. 

Fibre  as  with  NaOH  ; 
liquid  rose,  fluores- 
cent. 

No  action. 

No  action  in  cold  ; 
fibre  dirty  brown 
in  heat  ;  liquid 
faint  rose. 
Fibre  slowly  becomes 
light  reddish  brown. 

Slightly  fluorescent 
extract. 

No  action. 

HNO2  :  No  action. 
NH03  ;  orange  spot  removed 
by  washing  ;  bears  hot  soap- 
lye  well. 
HN02  :  No  action. 

Fibre  fine  deep  red  ; 
liquid  colourless. 

No  action. 

Fibre  gradually 
orange  ;  liquid 
yellow. 
No  action  in  cold, 
red  brown  on 

No  action. 
No  action. 

Yellow  colour  of  SnCl2  solu- 
tion turns  violet  with  NaOH, 

HNO,  :  Orange  spot. 

heating. 

Matters. 

Scarce  any  action. 

In  cold  no  action  ; 

No  action. 

3NOS  :  Deep  yellow  spot. 

liquid  yellow  on 

heating. 

Fibre  paler  ;  liquid 

Slowly  discharged 

No  action. 

HN03  :  White  spot  ;  turning 

colourless. 

in  cold,  quickly  on 

orange  in  the  middle. 

heating. 

Fibre  bright  orange  ; 
liquid  colourless. 

Fibre  dirty  yellow, 
slowly  discharged. 

No  action. 

HN08  :  Brown  spot,  turning 
reddish  grey 

No  action. 

Fibre  brownish 

No  action. 

HNO,  :  No  action. 

yellow,  then  col- 

HNO, :  Violet  spot. 

ourless. 

Fibre  dark  orange  ; 

Fibre  pale  yellow,        No  action. 

liquid  faint  orange. 

then  decolorised. 

..... 

•Iff 

As  with  NaOH. 

Fibre  dirty  yellow, 

No  action. 

':.   '                             V 

quickly  discharged. 

t    i 

•  !• 

As  in  brilliant  yellow. 

Fibre  brownish  yel- 

No action. 

low,  then  dis- 

charged. 

As  with  NaOH,  but 

Discharged  on  heat- 

No action.    , 

HNO,  :  No  action. 

fainter. 

ing. 

Fibre  unchanged  ; 
liquid  colourless. 

Fibre  yellowish 
brown,  discharged 

Slowly  extracted. 

HNO,  :  Violet  red  spot,  then 
red  in  the  middle,  violet  on 

on  heating  ;  liquid 

margin 

yellowish. 

No  action. 

Faint  action. 

No  action. 

HN02:  Fibre  deep   orange; 

with    NHS,    orange-brown  ; 

red  with  £-naphthol. 

No  action. 

Fibre  more  rose,  dis- 
charged on  boiling  ; 

No  action. 

HN02  :    Fibre    grey  ;    with 
NHS,  turns  dirty  yellow. 

liquid  colourless. 

No  action. 

Fibre  first  rose, 
slowly  discharged 
on  boiling. 

No  action. 

HN02  :     Fibre     lilac-grey  ; 
more  reddish  with  NH,. 
HNOS  :  Red  violet  spot  turn- 

ing grey. 

No  action. 

Fibre  orange-brown, 

Slight  extraction. 

HNOg  :  Red-brown  spot. 

then  colourless. 

Fibre  orange  ;  liquid 
nearly  colourless. 

Fibre  faint  yellow, 
by  degrees  dis- 
charged ;  liquid 

No  action. 

HN02:  No  action. 
HN08  :  Faint  orange  spots, 
fast  to  light. 

colourless. 

•.  .•> 

858 


CHEMICAL   TECHNOLOGY. 


[SECT.  vii. 


Colouring  Matter. 

HC1. 

H2S04. 

NaOH. 

Croceine  orange. 

Fibre  reddish  brown  ; 
liquid  rose. 

Fibre  darker  ;  liquid 
orange  ;  fibre  colour  re- 

Fibre orange-brown  ; 
liquid  nearly  col- 

stored on  washing. 

ourless. 

Anthracene  (derived 
from  a  vegetable 

Fibre  rather  greener  ; 
liquid  also.     Fibre  and 

As  with  HCL 

Colour  deeper  yellow; 
liquid  pale  yellow. 

colour). 

liquid  colourless  on 

watering. 

Xanthaurine  (derived 

Like  anthracene. 

Like  anthracene. 

Like  anthracene. 

from  vegetable 

colour). 

Galloflavine  (yarn 
dyed  with  alum 

Fibre  darker  ;  liquid  yel- 
low ;  both  nearly  colour- 

As with  HCL 

Fibre  more  orange; 
liquid  yellow. 

tartar  and  SnClz). 

less  on  dilution. 

Green  Colouring 

Kesorcin  green. 

Fibre  yellow-grey  ;  liquid 

Fibre  and  liquid  ;  brown 

Fibre  darker  ;  liquid 

orange-red. 

no  change  on  dilution. 

colourless. 

Blue  Colouring 

Victoria  blue. 

Fibre  blue-black  ;  liquid 

As  with  HC1. 

Fibre  dark  red  ; 

reddish  ;  on  dilution 

liquid  colourless. 

fibre  green,  then  blue. 

Azo  blue. 

Dilute  :  No  action. 

Fibre  blue-black  ;    liquid 

Fibre  cherry-red  ; 

Cone.  :  Fibre  black- 

blue. 

liquid  faint  rose. 

blue  ;  liquid  colourless. 

Benzoazurine. 

Fibre  blue-black  ;  liquid 

Fibre  black-blue  ;  liquid 

Fibre  dark  crim- 

colourless. 

greenish  blue. 

son  ;  liquid  rose. 

Basle  blue. 

Fibre  dark  grey  ;   liquid 

Fibre    blue-black,    then 

Fibre  darker. 

yellow  ;   fibre   blue    on 

green,  then  yellow;  li- 

washing. 

quid  yellow.  With  water 

both  blue. 

New  blue. 

Fibre  reddish  violet. 

Fibre  dark  grey  ;  liquid 

Fibre  violet-brown  ; 

grey. 

liquid  pale  rose. 

Nile  blue. 

Fibre  green,  then  orange  ; 

Fibre  and  liquid  brown- 

Fibre  red;  liquid  rose. 

liquid  orange. 

red  ;  on  dilution  yellow, 

green,  and  then  blue. 

Naphthylene  blue  G. 

Fibre  brown-violet  ;  liquid 

Fibre  black-brown  ;  liquid 

Fibre  brown  ;  liquid 

brown-orange. 

dark   brown,   on   dilu- 

orange-brown. 

tion  dirty  blue. 

Violet  Colouring 

Fast  violet. 

Fibre   dark    blue-black  ; 

Fibre  black  ;  liquid  grey- 

Fibre  black-blue  ; 

liquid  faint  bluish. 

blue  ;  on  dilution  green- 

liquid pale  violet. 

ish,  then  red;  fibre 

violet. 

Azo  violet. 

Dilute  :  Fibre  blue. 

Fibre  dark  blue  ;  liquid 

Fibre  crimson  ;  liquid 

Cone.  :  Fibre  black-blue  ; 

blue-green. 

colourless. 

liquid  colourless. 

Hessian  violet. 

Fibre  dark  blue;  liquid 

Fibre   dark  violet-blue  ; 

Fibre  redder  ;  liquid 

nearly  colourless. 

liquid    black-blue,     on 

colourless. 

dilution  blue-  violet. 

SECT.  VII.] 


DYEING    AND   TISSUE-PRINTING. 


859 


NH,. 

SnCl.+HCl. 

Alcohol. 

Other  Reactions  and  Remarks. 

No  action. 

Little  action  in  cold  ; 
quickly  discharged 

No  action,  or  faint 
orange  tint. 

HNO,  :  Black-blue  spots. 

on  boiling. 

Fibre  unchanged  ; 
liquid  scarcely 

Fibre  and  liquid 
rather  paler  ;  no 

No  action. 

HN03  :  Brown  spot,  lighter  in 
middle. 

yellow. 

discharge  on  boil- 

Fe2Cls :  Fibre  and  liquid  olive- 

ing. 

green. 

Alum  does  not  give  the  fluor- 

escence of  fustic. 

Like  anthracene. 

Like  anthracene. 

Like  anthracene. 

(Anthracene  and  xanthaurine 

both  from  Persian  berries  ? 

Fibre  darker  and 

No  particular  action. 

Heated  with  Fe2Cl6  :  Fibre 

more  olive  ;  liquid 

dirty  olive. 

almost  colourless. 

Matters. 

No  action. 

Slight  discharge; 

No  action. 

HNO3  ;    Yellow-brown   spot. 

liquid  brownish. 

Ash  contains  iron. 

Matters. 

Fibre  black-blue  ; 

Fibre  darker  in  cold, 

Slight  extraction  in 

HN03:   Black   spot,  turning 

liquid  colourless. 

green-blue  on  boil- 

colci, abundant  on 

red-brown  ;    turned   brown- 

ing  ;  liquid  green 

boiling. 

yellow  by  NH3  ;  latter  colour 

in  heat,  light  blue 

permanent  on  washing. 

when  cold. 

Fibre  violet-red  ; 

Fibre  black-blue, 

No  action. 

Picric  acid  :  Colour  blackish 

liquid  rose. 

then  slow  dis- 

brown. 

charge. 

Fibre  deep  violet  ; 

Slow  discharge. 

No  action. 

Liquid  turned  deep  blue  by 

liquid  cherry-red. 

boiling  with  soap-lye. 

No  action. 

No  action. 

Liquid  very  faint 

HNOS  :  Black  spot. 

blue. 

As  NaOH. 

Fibre  green,  then 

Liquid  faint  blue. 

colourless  ;  liquid 

colourless,  blue  on 

exposure  to  air. 

Fibre  violet. 

Fibre  green,  then 

Liquid  faint  blue. 

HNOf:  Yellow  spot,  green 

colourless  ;  liquid 

in  middle. 

colourless,  blue  on 

exposure. 

Fibre  brown-violet  ; 

Fibre  and  liquid  col- 

Liquid very  faint 

Vapour  of     HC1    turns    the 

liquid  light  red. 

ourless. 

violet. 

blue  to  chocolate-brown 

(colour   better  for  printing 

than  dyeing). 

Matters. 

Fibre  unaltered  ; 

Fibre  discharged, 

Liquid  scarcely 

HN03  :  Blue-black  spots. 

liquid  very  pale 

quickly  on  boiling. 

violet. 

violet. 

Fibre  dark  violet  ; 
liquid  a  faint 

Discharged  slowly. 

No  action. 

Picric  acid:  Fibre  black; 
turns  blue  with  dilute  acetic 

magenta. 

acid. 

No  particular  action. 

Fibre  blue,  dis- 
charged by  pro- 

No action. 

HN02  :    Dirty    violet-grey  ; 
turned  dirty  red  by  NaOH. 

longed  boiling. 

HNO8  :  Large  spot  with  pale 

blue  margin. 

86o 


CHEMICAL  TECHNOLOGY. 


[SECT.  vii. 


i 

Colouring  Matter. 

HCl. 

H2SOV 

NaOH. 

Heliotrope. 

Dilute  :  Fibre  dark  violet. 

Fibre  black-blue;  liquid 

Fibre  dark  crimson  ; 

Cone.  :   Fibre  black- 

blue. 

liquid  colourless. 

blue  ;  liquid  light  blue, 

violet  on  dilution. 

Acid  violet  7B. 

Fibre  green  ;  liquid  yel- 

Fibre  blackish,   then 

Fibre  discharged  ; 

lowish  brown,  green- 

brown  and  brown-red  ; 

liquid  colourless. 

blue  on  dilution. 

liquid  brown-red,   on 

dilution  green-blue. 

Gallocyanine. 

Fibre  and  liquid  violet. 

Fibre  dark  blue-black  ; 

Fibre  black-violet  ; 

liquid  intense  Prussian 

liquid  dirty  purple. 

blue,  light  magenta  on 

dilution. 

Muscarine. 

Fibre  blue-black  ;  liquid 

Fibre  green-black  ;  liquid 

Fibre  brownish  black; 

dirty  blue. 

greenish,    on    dilution 

liquid  nearly  col- 

dirty violet. 

ourless. 

Brown  Colouring 

Benzo  brown. 

Dilute  :   Fibre   reddish 

Fibre  and  liquid  black- 

No  action. 

brown. 

brown. 

Cone.  :   Darker  ;  liquid 

purple-red. 

Anthracene  brown. 

Fibre  paler  and  yellower  ; 

Fibre  paler  and  redder  ; 

Fibre  black  ;  liquid 

liquid  brown-yellow. 

liquid  chestnut,  yellow 

grey. 

on  dilution. 

Fast  brown  KG. 

Fibre  dark  violet-red  ; 

As  with  HCl. 

Fibre  bright  crimson  ; 

liquid  violet,  colour 

liquid  cherry-red. 

restored  on  dilution. 

Black  Colouring 

Cachou  de  Laval. 

Fibre  little  changed  ;  li- 

Fibre rather  yellower, 

No  action. 

quid  faint  grey. 

especially  after    wash- 

ing. 

Alizarine  black. 

Fibre  unchanged  ;  liquid 

Fibre  and  liquid  as  with 

Fibre  unchanged  ; 

faint  greenish  blue. 

HCl. 

liquid  faint  blue. 

Brilliant  black. 

Fibre  unchanged  ;  liquid 

Fibre  more  greenish, 

faint  violet-red. 

liquid  violet-black. 

Naphthol  black. 

Fibre  unchanged  ;  liquid 

Fibre  unchanged  ;  liquid 

Fibre  unchanged  ; 

reddish. 

olive-green. 

liquid  scarcely  red- 

dish. 

Eesorcin  Mask. 

Fibre  yellow-grey  ;  liquid 

Fibre  and  liquid  brown. 

Fibre  unchanged  ; 

orange-brown. 

liquid  very  faint 

green. 

Wool  black. 

Fibre  unchanged  ;  liquid 

As  with  HCl. 

No  action  in  cold  ; 

light  blue,  rose  on  dilu- 

on boiling,  fibre 

tion. 

and  liquid  violet. 

with  hot  water,  the  mass  being  then  comminuted  in  a  stuff-mill  and  bleached  with 
chloride  of  lime  whilst  still  hot.  According  to  the  statement  of  Lahkusse,  200  kilos, 
straw,  26  kilos,  caustic  soda,  and  10  kilos,  chloride  of  lime  are  required  for  the  produc- 
tion of  100  kilos,  of  bleached,  air-dried  straw-stuff. 

The  root-cuttings  of  jute  are  also  used  in  the  manufacture  of  paper,  as  also  the  waste 
from  rope-making,  which  serves  for  an  inferior  paper  for  envelopes. 

Mechanical  wood-stuff  was  first  obtained  by  F.  G.  Keller,  in  1840,  by  grinding  wood 


SECT.    VII.] 


DYEING  AND   TISSUE-PRINTING. 


861 


NH3. 

SnCla+IICl. 

Alcohol. 

Other  Reactions  and  Remarks. 

No  particular  action. 

Fibre  dark  grey, 

No  action. 

HNCX  :    Fibre  green-grey, 

then  discharged. 

orange  brown  on   washing 

and  treatment  with   NH3; 

liquid  faint  brown. 

Picric  acid  :  Dark  brown. 

Like  NaOH. 

Fibre  green  ;  liquid 

Liquid  scarcely 

HN02  :  No  action. 

blue-green  ;  both 

violet. 

HN03  :  Olive,  then  dirty  yel- 

blue on  dilution. 

low  ;  washing  does  not  re- 

store colour. 

Like  NaOH,  but 

Fibre  turns  yellowish 

No  action. 

HN02:   Fibre  dirty  violet- 

fainter. 

grey  ;  liquid  colour- 

grey; liquid  blue-green, 

less. 

green,  and  then  yellow. 

Fibre  violet-blue  ; 

Fibre  blackish,  blue 

No  action. 

HN03:  Black  spots. 

liquid  scarcely 

on  heating,  then 

(Probably  formed  by  action 

violet. 

green  and  yellow- 

of a  nitroso  compound  upon 

ish  grey. 

a  dioxynaphthaline). 

Matters. 

No  action. 

Colour  yellower  and 
lighter  ;  liquid 
brown-  yellow. 

Extracts  traces  of 
of  colour. 

Resists  light  badly. 

Fibre  brown-grey  ; 
liquid  nearly 
colourless. 
As  with  NaOH. 

Fibre  brown-yellow  ; 
liquid  the  same. 

Darker  at  first,  then 
discharged. 

Extracts  traces  of 
colour. 

No  action. 

HN03  :  Black  spot. 

HN03  :   Black   spot,   turning 
light  red-brown. 

Matters. 

No  action. 
No  action. 

Fibre  more  reddish 
or  brownish. 

On  boiling,  brownish. 

No  action. 
No  action. 

Goods  are  rarely  dyed  with 
cachou    de    Laval    alone. 
When   topped    with    other 
colours,  it    is    difficult    to 
detect. 
HN03  :  A  dark  olive  spot. 

Fibre  unchanged  ; 
liquid  violet-black. 

No  action. 
No  action. 

Fibre  dark  garnet  on 
boiling  ;  liquid 
colourless. 
On  boiling,  fibre 
light  green,  blue 
on  washing. 
Fibre  and  liquid 
light  brown. 

No  action. 
No  action. 
No  action. 

HN03  :  Dark  red-brown  spot. 

HNOS  :    A  brown    spot.     (A 
mixture  of  various  colours.) 

HN03  :  Yellowish  brown  spot. 
Ash  contains  iron. 

No  action. 

Fibre  discharged. 

No  action. 

HN03  :  Light  red-brown  spot. 

under  millstones.  This  article  only  obtained  industrial  importance  in  1846,  by  the 
introduction  of  suitable  machinery  for  its  comminution  and  sorting,  which  rendered 
possible  the  production  of  a  uniform  quality  on  the  large  scale.  Ground  wood  serves 
for  the  production  of  inferior  papers,  as  its  fibre  is  too  short  for  strong  papers  and 
not  susceptible  of  felting.  Hence  it  serves  more  for  filling  up  than  as  a  substitute  for 
rags.  The  resin  present  resists  the  action  even  of  a  strong  bleach.  Paper  from  ground 
wood  (mechanical  wood-stuff)  readily  turns  yellow. 


862  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

Much  more  important  is  the  chemical  production  of  cellulose,  for  which  the  wood 
of  coniferous  trees  is  chiefly  used.  The  stems,  freed  from  bark,  branches,  &c.,  are  cut 
tip  and  boiled  from  two  to  three  hours  in  wrought-iron  vessels  in  caustic  soda-lye  of 
sp.  gr.  1*085  under  a  pressure  of  from  6  to  10  atmospheres.  The  whole  is  then  run  oft 
into  cisterns,  where  the  brown  lye  escapes  at  the  bottom.  The  soda  is  recovered  by 
evaporating  down  the  liquid  and  igniting  the  residue.  The  fibrous  mass  is  lixiviated 
with  water  and  washed  clean.  The  oil  of  turpentine  evolved  is  sometimes  collected 
in  suitable  refrigerators.  The  recovery  of  vanilline,  the  presence  of  which  is  detected 
by  the  odour,  has  been  attempted  unsuccessfully.  The  bleaching  is  effected  in  the 
hollander. 

From  a  calculation  given  by  the  author,  it  appears  that,  at  German  prices,  I  ton 
of  wood  cellulose  costs  only  240  marks,  whilst  the  same  weight  of  esparto  cellulose  costs 
305-6  marks. 

Sulphurous  acid  is  also  used  in  the  production  of  cellulose.  The  comminuted  wood 
is  treated  under  pressure  with  an  acid  solution  of  calcium  sulphite  obtained  by  placing 
pieces  of  calcium  carbonate  in  a  tower  and  passing  over  them  water  from  above  and 
sulphurous  acid  from  below.  The  wood,  cut  up  and  freed  from  bark,  is  steamed  in  a 
boiler  lined  with  lead,  into  which  the  acid  solution  of  calcium  sulphite  is  introduced. 
The  whole  is  heated  first  to  108°  and  then  gradually  raised  to  118°.  If  a  sample  of 
the  liquid  is  mixed  with  ammonia  the  residual  calcium  sulphite  falls  to  the  bottom,  but 
the  salts  formed  during  the  working  of  the  process  are  not  precipitated.  The  propor- 
tion of  the  effective  solution  can  easily  be  determined  from  the  precipitate.  If  the 
precipitate  is  only  about  •£$  of  the  volume  of  the  sample,  the  time  for  boiling  off  the 
sulphurous  acid  is  arrived.  The  temperature  and  the  pressure  sink  simultaneously. 
If  the  precipitate  in  the  test-glass  is  only  ^V  in  bulk,  the  process  is  completely  at  an 
end  and  the  solution  must  be  quickly  run  off.  A  higher  temperature  would  hasten 
the  process,  but  would  require  a  higher  pressure,  and  the  cellulose  obtained  would  be 
inferior  in  both  quality  and  quantity. 

The  chemical  process  which  takes  place  during  boiling  is,  according  to  Mitscherlich, 
as  follows : — The  sulphurous  acid  is  oxidised  to  sulphuric  acid  by  a  part  of  the  oxygen  of 
the  organic  matter,  and  this  acid  under  normal  conditions  combines  with  the  bases, 
which  were  previously  combined  with  the  sulphurous  acid.  If  the  process  is  mis- 
managed, free  acid  is  formed  in  the  solution.  At  the  same  time  tannic  acid  is  formed 
from  the  incrusting  substances.  For  the  right  management  of  the  process  a  main 
condition  is  that  the  sulphurous  solution  must  be  free  from  polythionates,  as  the 
operation  miscarries  in  presence  of  the  latter.  At  the  same  time  the  temperature  in- 
creases rapidly,  and  samples  drawn  show  an  anomalous  decrease  of  sulphurous  acid. 
The  polythionic  acids  generally  appear  in  consequence  of  the  presence  of  free  fumes  of 
sulphuric  acid  during  the  roasting  process  To  avoid  this,  care  must  be  taken  that  the 
sulphurous  acid  is  free  from  sulphuric  acid  or  its  salts. 

Ekman  boils  with  a  solution  of  magnesium  sulphite  produced  by  exposing  calcined 
magnesia  in  towers  to  the  action  of  sulphurous  acid  and  of  water.  He  boils,  e.g., 
esparto  grass  (freed  from  roots,  &c.)  with  a  solution  of  1-4  per  cent,  magnesia  and 
4-5  per  cent,  sulphurous  acid.  After  the  pressure  has  gradually  been  raised  to  575-6 
atmos.,  and  is  kept  at  this  point  for  from  two  to  four  hours,  fibres  are  obtained  which, 
after  being  well  washed,  are  at  once  fit  for  common  printing  paper,  and  for  better 
sorts  after  bleaching  with  chloride  of  lime. 

An  experiment  made  at  Bergvik  gave  the  following  results  : — Of  the  4395  kilos,  of 
deal  planks  used  there  appeared  by  the  removal  of  branches  a  loss  of  260  kilos. ;  by 
cutting,  sorting,  and  dusting,  &c.,  of  565  kilos.,  or  a  total  loss  of  825  kilos.  The 
remaining  3570  kilos,  were  placed  in  four  boilers,  and  yielded,  after  washing  in  common 


SECT.    VII.] 


PAPER   MANUFACTURE. 


863 


hollanders,  2875  kilos,  of  stuff,  equivalent  to  1437  kilos,  of  dry  stuff,  or  32^68  per  cent, 
of  the  crude  wood,  which  contained  21  per  cent,  of  moisture. 

In  comparing  the  results  of  the  various  sulphite  processes,  the  test  for  lignose  with 
aniline  sulphate  is  not  trustworthy.  It  is  better  to  treat  the  products  with  chlorine, 
after  which  the  lignose  substance  is  turned  a  magenta  colour  by  sodium  sulphite. 
The  remaining  lignose  may  be  quantitatively  determined  by  boiling  with  potassa-lye. 
According  to  Christy,  in  Ekman's  process  the  incrustations  are  completely  dissolved,  so 
that  the  washed  stuff  gives  no  colour  with  aniline  sulphates,  and  dissolves  in  sulphuric 
acid  almost  entirely  without 
a  dark  coloration.  Fig.  573  **£  573- 

shows  the  fibres  of  the  white 
pine  (tanne)  in  a  longitudinal 
section,  and  Fig.  574  in  a 
cross  section  as  it  appears 
under  the  microscope  after 
treatment  by  Ekman's  process. 
Fig.  575  shows  the  fibres 
(strongly  attacked)  of  linen 
(L)  and  cotton  (B)  rag  papers. 
Fig.  576  shews  ground  wood 
from  conifers,  with  the  cells  and  pith  radii,  which  are  here  easily  recognised,  whilst  in 

Fig-  575-  Fig-  576. 


Fig-  574- 


chemical   cellulose   (Fig.    577)  they  are  not  easily  recognised.     Fig.  578  represents 
straw-stuff,  with  its  cells,  0,  very  distinct  from  those  of  esparto. 

In  examining  wood  and  other  fibrous  vegetable  matter,  H.  Miiller  boils  5  grammes 
of  the  sample  five  times,  using  each  time  100  c.c.  of  water.  He  dries  and  weighs  them, 
and  then  treats  them  in  a  lixiviating  apparatus  with  a  mixture  of  alcohol  and  benzene,  to 
dissolve  fat,  wax,  resin,  &c.  Colouring  matter  and  pectosic  substances  are  removed 
by  repeated  boiling  with  dilute  ammonia.  For  obtaining  the  cellulose  in  a  state  of 
purity  the  sample  is  covered  with  100  c.c.  water  in  a  wide-necked  stoppered  glass,  and 
then,  according  to  the  nature  of  the  sample,  there  are  added  from  5  to  10  c.c.  of  a  solu- 
tion of  bromine  containing  2  c.c.  bromine  in  500  c.c.  water.  The  yellow  colour  of  the 
liquid  disappears  gradually  on  treating  the  purer  bast-fibres,  such  as  flax  or  hemp,  but 


864 


CHEMICAL   TECHNOLOGY. 


[SECT.  vn. 


in  a  few  minutes  in  straw-stuffs  or  woods.  When  the  colour  has  disappeared  a  fresh 
quantity  of  the  bromine  solution  is  added,  and  so  on,  until  at  last  a  point  is  reached 
when  the  absorption  becomes  so  sluggish  that  the  liquid  remains  yellow  even  after  the 
lapse  of  from  twelve  to  twenty-four  hours,  and  the  presence  of  free  bromine  can  be 


Fig.  577- 


Fig.  578. 


detected.  The  mass,  when  freed  from  the  liquid  by  nitration,  is  washed  Avith  water,  and 
heated  almost  to  a  boil  with  500  c.c.  of  water,  to  which  2  c.c.  of  liquid  ammonia  have 
been  added.  All  crude  vegetable  fibres  and  woods,  without  exception,  if  thus  treated,  take 
a  more  or  less  intense  deep  brown  colour,  as  does  also  the  liquid.  The  filtered  and 
washed  mass  is  returned  to  the  stoppered  glass,  again  covered  with  water,  and  solution 
of  bromine  is  again  added.  The  first  addition  of  bromine  is  generally  easily  absorbed, 
and  the  dark  colour  becomes  lighter.  The  purer  fibres,  to  which  only  quantities  of 
5  c.c.  are  added  in  the  second  treatment,  soon  become  colourless,  and  if  further 
quantities  of  bromine  are  added,  they  remain  unabsorbed  for  days.  On  the  other 
hand,  lignified  tissues,  after  the  above-mentioned  treatment  with  ammonia,  absorb 
bromine  with  undiminished  readiness,  and  we  may  continue  adding  quantities  of  10  c.c. 
of  the  bromine  solution  until  the  absorption  comes  to  an  end.  When  this  point  is 
reached  the  treatment  with  dilute  ammonia  is  repeated.  With  the  purer  fibres  this 
second  treatment  is  usually  sufficient,  but  more  strongly  lignified  tissues  require  a  third 
and  sometimes  a  fourth  treatment  with  bromine  in  gradually  reduced  quantities.  After 
drying  and  weighing  the  cellulose,  the  quantity  of  the  soluble  modification  of  cellulose 
can  be  approximately  determined  by  the  loss  on  boiling  four  or  five  times,  each  time 
with  a  solution  of  I  part  crystallised  sodium  carbonate  in  100  parts  of  water.  Such 
soluble  cellulose  is  probably  in  most  cases  wasted  in  the  technical  treatment  of  fibrous 
materials. 

The  nitrogenous  material  derived  from  the  protoplasmic  contents  of  the  cells,  which. 
are  partly  soluble  and  partly  insoluble,  are  small  in  quantity,  and  their  presence  has  no 
technical  importance. 

In  many  raw  materials  an  important  part  of  the  cellulose  occurs  in  the  state  of 
worthless  tissues,  and  it  is  then  important  to  know  its  proportion.  As  this  is  not 
practicable  chemically,  it  has  to  be  reached  by  mechanical  means.  An  approximate 
separation  may  be  reached  by  stirring  up  the  cellulose  with  an  abundance  of  water, 
and  pouring  it  upon  a  straining-cloth,  stretched  over  a  funnel,  repeating  this  treatment 


SECT.   VII.] 


PAPER   MANUFACTURE. 


865 


as  long  as  the  water  runs  through  turbid.     In  this  manner  the  following  figures  were 
obtained : — 


Woods. 

Water. 

Watery 
Extract. 

Resin. 

Cellulose. 

[ncrusttng 
Matter. 

Birch    

12*48 

2-6"; 

I  -JA 

et'C-? 

28-91 

I2'^7 

2  M.T 

33  3^ 

Oak       

I7-J2 

I2'2O 

O'QI 

43  47 

J9  J4 

Alder    

IO"7O 

2*48 

0*87 

Lime     

lO'IO 

V(6 

3"Q1 

54  °2 

31  33 

Chestnut 
Fir        

12-03 
12-87 

SHI 
4*O? 

I'lO 

1-6^ 

52-64 

C3'?7 

28-82 
28-18 

Poplar  ...... 

I2'IO 

2  -88 

I  "37 

20  "88 

Pine      
Willow          

I3-87 

11-66 

1-26 
2-65 

0-97 
1-23 

56-99 
5572 

26-91 
28-74 

According  to  F.  Schulze,  i  part  of  the  dried  and  pulverised  material  is  extracted 
first  with  water,  then  with  alcohol  and  ether,  and  after  it  has  been  well  dried  it  is 
treated  for  from  twelve  to  fourteen  days,  at  a  temperature  not  exceeding  15°,  with  0*8 
part  potassium  chlorate  and  12  parts  nitric  acid  of  sp.  gr.  no.  After  the  lapse  of  this 
time  it  is  diluted  with  water,  filtered,  and  washed,  first  with  cold  and  then  with  hot 
water.  The  contents  of  the  filter  are  rinsed  into  a  beaker  and  digested  for  three- 
quarters  of  an  hour  with  weak  ammonia  (i  part  to  50  water)  at  about  60°.  The  mass 
is  then  washed  with  cold  ammonia  until  the  filtrate  runs  through  colourless.  It  is  then 
successively  and  completely  washed  with  cold  and  hot  water,  with  alcohol  and  ether. 
If  we  disregard  a  small  trace  of  nitrogen,  the  cellulose  so  obtained  is  chemically  pure. 

K  wood  is  treated  with  soda-lye  at  elevated  temperatures  and  high  pressure,  a 
relatively  large  part  of  the  cellulose  is  dissolved  and  wasted. 

As  a  reagent  for  wood  Friesner  recommends  phloroglucine.  If  a  paper  contains 
ground  wood-stuff  it  turns  violet  red,  if  first  moistened  with  HC1  and  then  with 
phloroglucine.  When  lignose  is  mixed  with  cellulose  the  test  is  uncertain,  and  a 
miscroscopic  examination  is  required. 

Mineral  Additions  to  Rags. — A  moderate  addition  of  a  mineral  body  to  the  paper 
material  whitens  the  whole,  and  for  inferior  or  ordinary  paper  it  is  successfully 
employed.  It  is  unfit  for  very  thin  paper,  making  it  shiny  and  brittle.  A  profitable 
addition  of  mineral  matter  is  from  5  to  10  per  cent,  of  the  weight  of  paper,  a  greater 
addition  making  the  paper  dull,  brittle,  and  hairy  to  write  upon.  The  usual  mineral 
mixtures  in  frequent  use  at  the  present  day  are — clay  free  from  sand,  china  clay,  or 
kaolin.  Annaline  pearl-hardening,  in  the  form  of  a  pulp  resembling  clay,  is  most 
preferred,  being  not  so  expensive.  In  1850  it  was  favourably  received,  under  the 
names  of  fixed  white,  raw  white,  patent  white,  or  permanent  white.  15  kilos,  of  the 
paste  with  i  oo  kilos,  of  paper  pulp  are  generally  employed. 

Precipitated  barium  sulphate  has  been  latterly  much  used  in  paper-making,  as  have 
also  finely -ground  bauxite  and  precipitated  magnesia. 

Manufacture  of  Paper  by  Hand. — The  old  method  of  making  paper  by  hand  was 
from  the  pulp  of  waste  paper  placed  in  a  mould  of  the  required  size ;  but  this  method, 
although  still  used  for  writing  paper,  was  found  to  restrict  the  size  of  the  sheets,  and 
different  methods  were  tried  with  varied  success,  until  a  machine  was  invented  which, 
without  the  aid  of  moulds,  manufactured  the  paper  in  any  length. 

Cutting  and  Cleaning  the  Rags. — The  Cutting  and  Sorting  of  the  Rags. — The  first 
operation  is  performed  by  two  machines,  called  the  half-hollander  and  the  whole- 
hollander.  The  rags  are  next  treated  chemically  with  potash  to  rot  them.  By  the 
old  method,  rags  were  cut  into  pieces  about  four  inches  square,  by  being  drawn  across 
a  sharp  knife  fixed  upon  a  table.  Machinery  has  superseded  this  arrangement,  and 
various  cutting  machines  have  been  invented,  among  which  we  may  mention  that  of 

3  i 


866  CHEMICAL  TECHNOLOGY.  [SECT.  vii. 

Davey,  in  which  a  horizontal  knife  revolves  around  a  fixed  cylinder  cutting  the 
rags  into  strips.  Bennet's  cutting  machine  consists  of  two  knives  radiating  from  a 
wheel,  and  bearing  against  another  knife.  Some  machines  are  constructed  with  a 
quantity  of  circular  sharp-edged  steel  plates,  like  the  machine  of  Uffenheiruer,  of 
Vienna.  After  cutting,  the  rags  are  cleansed  from  dust  and  other  impurities  by  the 
Willow  machine.  The  best  kind  of  sifting  machine  is  in  the  form  of  a  drum  with  the- 
upper  part  covered  with  a  wire  grating.  The  rags  are  put  in  by  a  side  door,  which 
acts,  as  the  drum  revolves,  as  a  refuse  door,  casting  off  the  sand  and  impurities, 
leaving  the  rags  winnowed.  They  are  next  boiled  in  an  alkaline  lye,  or  solution 
of  4  to  10  Ibs.  of  sodium  carbonate,  with  one-third  of  quicklime  to  100  of  the- 
material.  The  rags  are  placed  in  large  cylinders  slowly  revolving,  and  causing  them 
to  be  constantly  turned  over.  Into  these  cylinders  a  jet  of  chlorine  water,  with  a 
pressure  of  30  Ibs.  to  the  square  inch,  is  directed.  H.  Volter  patented  in  1859  a  hori- 
zontal steam  cylinder,  which  receives  the  steam  from  a  tubular  guide-cock  provided  to 
the  boiler,  an  inner  cylinder  revolving  to-  move  the  rags.  The  distant  end  of  the  boiler 
and  the  tubular  cylinder  draws  up,  and  the  mass  is  easily  poured  into  the  washing 
machine  when  in  a  fluid  state  (Silberman's  Washing  Hollander).  Although  partly 
cleansed  by  the  above  method,  the  rags  still  require  further  boiling. 

The  Separation  of  the  Rags  for  Half-stuff  and  the  Whole-stuff. — The  machine  used  in- 
separating  and  rending  the  rags  are  : — 

1 .  The  German  stamping  machine. 

2.  The  rag  mill  (rolling  hollander). 

(a)  The  half-hollander. 
(/3)  The  whole-hollander. 

Formerly  the  rags  were  rotted  before  crushing,  being  placed  in  a  stone  trough, 
where  in  two  or  three  days  they  became  heated,  and  developed  a  strong  amnioniacal 
odour.  When  the  surface  was  covered  with  a  mould,  the  rags  were  sufficiently  decayed 
for  the  purpose  of  manufacture.  They  were  then  taken  out  in  a  brown  mass,  those 
remaining  behind  as  sediment  being  used  for  coarse  paper.  The  present  method  of 
boiling  the  rags  with  alkalies  is  preferable,  giving  the  paper  greater  firmness. 

Stamp  Machine. — The  German  stamp  machine  is  at  the  present  time  only  to  be 
found  in  smaller  manufactories.  It  is  of  the  nature  of  a  hammer.  Six  or  eight  stamp 
rods  are  fixed  into  a  strong  oak  beam,  and  work  intermittently  with  a  set  below. 
Through  an  opening  provided  with  a  fine  sieve  the  water  is  conveyed  away.  As  the 
hammers  rise  and  fall,  the  stamp  holes  serve  for  a  water  conduit.  Three  to  five 
hammers  work  in  each  hole.  The  rags  are  mixed  with  sufficient  water  to  form  a  pulp, 
and  remain  in  the  machine  twelve  to  twenty  hours. 

The  hollander  has  a  cylinder  set  with  blades  or  knives  and  kept  in  rapid  rotation. 
Below  this  is  the  so-called  ground-work  fitted  with  similar  blades.  After  the  chest 
has  received  the  necessary  quantity  of  water  the  rags,  &c.,  are  thrown  in.  The  roller 
is  set  in  motion  with  a  speed  of  from  100  to  150  rotations  per  minute.  The  blades 
strike  into  the  liquid  and  draw  the  rags  into  the  space  between  the  circumference  of  the- 
roller  and  those  of  the  ground-work — the  two  sets  of  knives  acting  like  the  blades  of 
scissors — and  finally  eject  the  mass  in  a  state  of  fine  division  over  the  steep  slope  of  the 
cran. 

Bleaching  the  Pulp. — After  this  the  mass  is  placed  in  another  machine,  the  whole- 
hollander,  and  bleached  by  a  solution  of  chloride  of  lime,  chlorine  water,  chlorine 
gas,  or  other  bleaching  agent.  The  lime  is  retained  in  the  machine  until  the  rag& 
are  sufficiently  bleached ;  the  pulp  is  then  let  down  into  long  slate  cisterns  to  steep- 
before  placing  in  the  beating  machine. 

When  bleached  by  chloride  of  lime,  i  to  2  kilos,  are  applied  to   100  kilos,  of  pulp- 


SECT,  vii.]  PAPER   MANUFACTURE.  867 

When  greater  smoothness  is  required,  a  little  hydrochloric  or  sulphuric  acid  is  added, 
although  care  must  be  taken  in  its  use,  for  applied  too  largely  it  destroys  the  fibre. 
Orioli  employs  aluminium  hypochlorite,  known  by  the  name  of  "Wilson's  bleaching 
preparation,  aluminium  chloride  being  obtained  on  the  one  hand,  while,  on  the  other, 
all  the  bleaching  effects  arise  from  the  delivery  of  ozonised  oxygen, 

A12C1603  =  30  +  A12C16. 

Varrentrapp's  zinc  hypochlorite,  under  the  name  of  Varrentrapp's  bleaching-powder, 
is  worthy  of  notice  as  being  extensively  used.  In  this  powder,  chloride  of  lime, 
decomposed  with  zinc  vitriol,  or,  better,  with  zinc  chloride,  is  employed.  When  bleached 
by  zinc  chloride,  the  mineral  acid  decomposes  the  chloride  of  lime,  therefore  no 
risk  is  incurred  by  the  fibre. 

Antichlore. — When  the  bleach  retains  chlorine,  it  is  washed  in  soda,  potash,  or  anti- 
chlore,  to  neutralise  the  adhering  hydrochloric  acid,  which  merely  washing  in  water 
would  not  effect.  The  chief  constituents  of  antichlore  are  sodium  sulphite,  tin  chloride, 
and  sodium  hyposulphite.  A  mol.  of  sodium  sulphite  (Na2S03  +  7H2O)  removes  i  mol. 
of  chlorine  (C12),  whilst  hydrochloric  acid  and  sodium  sulphate  are  formed.  A 
mixture  of  sodium  sulphite  with  sodium  carbonate  is  employed  to  neutralise  the 
hydrochloric  acid.  The  sodium  sulphate  and  sodium  chloride  a*>e  removed  by 
washing.  Calcium  sulphite  is  greatly  approved,  and  is  considered  to  be  as  effective 
as  antichlore,  when  applied  as  the  corresponding  sodium  salt.  A  mol.  of  tin-salt 
(SnCl2+  2H20)  is  taken  up  by  a  mol.  of  chlorine  (C10),  by  which  tin  chloride  (SnCl4) 
arises.  After  the  working  is  completed,  so  much  sodium  carbonate  is  added  as 
is  required  to  saturate  the  hydrochloric  acid.  A  mol.  of  sodium  thiosulphate 
(Na2S203  +  5H2O),  absorbs  4  mols.  of  chlorine,  whilst  sodium  sulphate,  hydrochloric 
and  sulphuric  acids  are  formed. 

Blueing. — Notwithstanding  careful  chemical  bleaching,  the  pulp  has  still  a  yellow 
tinge,  and  requires  a  colouring  matter  which  is  generally  introduced  in  the  process 
of  beating.  The  blues  commonly  used  are  ultramarine,  Paris  blue,  indigo,  aniline 
blue,  and  oxide  of  cobalt.  With  100  kilos,  of  the  dry  paper  stuff,  o'5  to  1*5  kilo,  of 
ultramarine  are  mixed,  according  to  the  strength  of  the  colour  required. 

Sizing. — The  pulp  requires  sizing  to  preserve  the  colour.  It  is  guided,  as  it  issues 
from  the  hollander,  through  a  tub  of  size,  and  afterwards  carried  over  skeleton  drums, 
containing  revolving  fans  to  dry  it  as  it  passes  ;  heated  cylinders  are  also  used  for  drying. 
Starch  is  used  to  give  a  thicker  consistence  to  the  size,  which  is  generally  made  from 
the  best  glue,  resin  being  added  in  quantities  never  exceeding  3  kilos,  per  100  kilos, 
of  the  pulp,  to  impart  the  desired  amount  of  stiffness. 

a.  Hand-made  Paper. — Straining  the  Paper  Sheets. — There  are  three  ways  of 
straining  or  filtering  the  pulp : — First,  by  straining  through  a  brass  sieve  with  fine 
slits  to  allow  the  pulp  to  pass,  and  retaining  all  lumps  and  knots.  Secondly,  by 
pressure ;  and,  thirdly,  by  evaporation.  In  the  first  operation  the  sheet  is  formed  by 
a  mould  of  the  size  required  being  dipped  into  a  tub  of  pulp  previously  strained.  The 
pulp  becomes  extended  to  a  thin  layer  and  the  water  filters  off.  The  tub  is  either 
round  or  of  a  quadrangular  shape  made  of  wood,  lined  with  lead.  A  broad  board 
running  across  the  tub  is  called  the  bridge,  and  a  smaller  one  under  the  large  one  the 
little  bridge.  The  large  bridge  has  a  pointed  support,  technically  termed  the  donkey, 
for  the  form  or  frame  to  lean  against. 

The  sifting  machine,  technically  termed  the  knotter,  used  in  the  manufacture  of 
hand-paper,  consists  of  an  upright  cylindrical  sieve,  in  which  an  inner  cylinder  revolves. 
As  the  whole-stuff  is  taken  from  the  tub,  the  remainder  becomes  massed  together,  and 
steam  or  other  pressure  is  employed  to  force  the  pulp  through  the  sieve  and  cylinder, 
the  latter  retaining  the  lumps  and  knots.  The  paper  forms,  upon  which  the  whole- 


868  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

stuff  is  placed,  are  constructed  with  brass   wires  to  allow  the  water  to   drain  off, 
retaining  the  pulp.     There  are  two  kinds  of  forms  : — 

(1)  The  Ribbed  Form. — A  square  or  oblong  frame  of  oak  or  mahogany  with  parallel 
brass  wires  and  cross  wires  at  intervals  to  steady  them.     Lined  paper  is  made  on  this 
form,  and  is  not  much  glazed  on  account  of  the  time  and  expense,  being  reckoned  an 
inferior  paper. 

(2)  The  Vellum  Form. — A  frame  of  fine  brass  wire-work.     Vellum  paper  is  made 
on  this  form,  and  has  a  delicate  even  surface  ;  it  can  be  made  to  present  any  degree  of 
glossiness,  by  pressing  and  satining.     When  held  to  the  light  it  appears  uniform,  not 
possessing  bright  and  opaque  lines  as  in  the  former  paper. 

A  ribbed  form  similar  to  the  vellum  form  is  employed  in  the  manufacture  of  paper 
distinguished  by  trade  marks,  coats  of  arms,  &c.,  the  impress  of  the  wire  forming  what 
is  termed  the  water-mark ;  bank-notes  are  made  separately  in  a  mould  in  this  way. 
The  edge  of  the  form  makes  the  edge  of  the  paper,  forms  being  used  according  to  the 
size  required;  also  the  quantity  of  the  whole-stuff  varies  in  accordance  with  the 
required  thickness  of  the  sheets.  Felt  is  extensively  used  in  the  manufacture  of  paper ; 
it  is  unlike  the  ordinary  felt  for  hats,  being  a  coarser,  looser,  white  woollen  fabric,  more 
suitable  for  rolling. 

The  work  of  the  pulp-tub  is  divided  into  two  parts,  the  squaring  and  the  scooping ; 
the  latter  is  the  placing  of  the  pulp  in  the  mould,  the  former  the  placing  of  the  sheets 
between  felt.  The  tub  is  stirred  occasionally  with  a  pointed  stick,  technically  termed 
the  scoop  stick.  The  pulp  is  taken  out  on  the  form  in  a  sloping  position,  shaken  a 
little  to  aid  cohesion,  and  finally  placed  on  the  small  bridge.  The  next  sheet  is  placed 
on  the  large  bridge.  The  form  is  laid  in  a  sloping  position  against  the  donkey-rest  to 
drain,  and  the  paper  finally  placed  on  the  felt  to  dry  a  little,  the  empty  form  returning 
to  the  tub.  The  first  paper  sheet  is  covered  with  felt,  on  which  the  next  is  placed  ; 
the  average  number  of  sheets  manufactured  exceeding  5000  a  day. 

Pressing  the  Paper. — As  soon  as  there  is  a  sufficient  number  of  sheets,  they  are 
made  into  a  thick  bale  and  placed  under  the  press,  the  number  of  sheets  comprising 
a  bale  being  generally  181.  Three  bales,  181  x3  =  543  sheets;  twenty  quires  =  480 
sheets  sized,  and  500  unsized.  Pressing  gives  firmness  and  glossiness,  and  by  continued 
pressing  exceeding  smoothness  is  obtained. 

Drying  the  Paper. — The  process  of  pressing  has  not  quite  removed  the  water  from 
the  paper,  which  has  to  be  dried  in  an  airy  chamber, the  sheets  being  placed  separately, 
or  two  to  five  together  as  required.  An  expert  workman  can  place  from  800  to  900 
layers  of  two  to  five  sheets  each  in  a  day,  as  well  as  hang  and  dry  the  sheets  and 
take  them  off  the  cord. 

Sizing  the  Paper. — Paper  is  not  durable  unless  it  is  sized,  and  is  only  used  for 
filtering,  packing,  .printing,  or  scribbling  papers.  Sizing  gives  the  paper  substance  by 
filling  the  pores,  and  making  it  firmer,  stifier,  and  harder.  Ordinary  size  dissolved  in 
water  will  not  always  prove  effective,  and  it  is  necessary  to  add  a  solution  of  an 
aluminium  salt,  such  as  that  of  alum,  aluminium  sulphate,  or  aluminium  chloride,  to 
prevent  decay.  Without  chemical  preparation  the  sheets  are  rendered  sticky  and  have 
to  be  sized  separately,  but  with  the  above  addition  from  80  to  100  sheets  can  be  success- 
fully sized  by  hand ;  a  good  workman  can  size  from  40,000  to  50,000  sheets  in  twelve 
hours.  The  sheets  must  not  be  dried  too  quickly  after  sizing. 

Preparing  the  Paper. — After  the  sized  paper  is  pressed  and  dried,  it  requires  further 
preparation  to  make  it  fit  for  use.  The  first  process  consists  in  the  finishing  or 
trimming  to  remove  all  the  little  specks  and  blemishes,  and  to  smooth  the  sheets. 
The  finished  sheets  are  counted  and  placed  together,  the  workman  by  continued 
practice  counting  8000  to  15,000  sheets  as  he  places  them,  and  separating  them  into 
whole  and  half  quires,  twenty-four  sheets  of  sized  and  twenty-five  sheets  of  unsized 


SECT,  vii.]  PAPER   MANUFACTURE.  869 

paper  making  a  quire ;  the  upper  and  under  quire  of  each  ream  being  placed  on  an 
extra  sheet,  known  as  outsides.  The  even  and  glazed  surface  is  mostly  obtained  by 
hot-pressing,  when  every  sized  sheet  is  interposed  between  two  unsized  sheets ;  this  is 
called  interchanging.  The  preparation  of  the  various  kinds  of  paper  is  now  accom- 
plished, with  the  exception  of  the  finest  letter  paper,  which  requires  an  extra  process 
to  give  it  a  final  gloss,  by  pressing  between  the  rollers  of  the  satining  machine.  The 
different  varieties  of  paper  are  classed  under  three  denominations  : — 

The  Different  Kinds  of  Paper. — A.  Writing  and  drawing  paper,  the  smaller  kinds 
of  copy  paper,  deed  paper,  the  finer  post  and  letter  paper,  and  vellum  letter  paper. 

B.  Printing  paper  for  books,  as  distinguished  from  copy  printing,  deed  printing, 
post  and  vellum  printing,  note  and  copper-plate  paper.     Silk  papers  for  fancy  pur- 
poses ornamented  with  gold  or  silver,  and  printed  from  engraved  copper  plates. 

C.  The  looser  textured  papers,  such  as  unsized  parcel  paper ;  the  better  kinds  are 
filter*  and  blotting-papers.     Packing-paper  is  half-sized,  and  is  met  with  as  a  yellow 
straw  paper,  blue  sugar  paper,  and  pin  and  needle  papers. 

/3.  Machine  Paper. — Manufacture. — Manufacturing  paper  by  hand  requires  much 
time  and  labour,  and  machinery  is  found  to  be  quite  as  efficient.  Endless  paper  of 
any  breadth  can  be  made  by  machinery  with  the  same  amount  of  strength  and 
firmness  as  hand  paper.  The  straight  form  and  the  vibrating  machine  are  used  for 
finer  paper. 

It  is  requisite  that  the  machine  should : 

(1)  Make  the  pulp  of  a  suitable  consistence  by  diluting  it  with  water. 

(2)  Purify  the  whole-stuff  from  knots. 

(3)  When  free  from  knots  work  the  material  by  means  of  regulators,  delivering  the 
stuff  from  the  form,  and  producing  by  the  uniform  flow  of  the  pulp  a  smooth  paper 
leaf  of  the  breadth  required. 

(4)  Be  so  regulated  that  the  stream  of  whole-stuff  may  form  a  sharply  turned  leaf. 

(5)  Free  the  paper  leaf  from  water,  so  that  it  only  requires  drying  in  an  airy  cham- 
ber and  pressing. 

(6)  Remove  the  water,  steam  cylinders  being  principally  used. 
The  finished  paper  is  cut  into  sheets  by  the  paper-cutting  machine. 

After  the  whole-stuff  is  thinned  to  a  consistence  easily  moved  by  water,  it  flows  to 
the  knotter,  placed  in  a  perforated  cylinder  of  sheet  brass,  which  is  supplied  with  an 
interior  mechanism  revolving  with  greater  velocity.  One  of  the  best  knotting  machines 
is  Manuhardt  and  Steiner's,  of  Munich.  After  the  whole-stuff  is  purified  by  the 
knotting  machine  it  passes  out,  and  the  whole-stuff  reservoir  is  supplied  anew.  In 
course  of  time  the  consistence  becomes  altered,  sometimes  producing  a  thicker  sheet 
than  required.  This  variation  is  obviated  by  the  regulator,  an  essential  in  the  paper 
manufactory. 

Hartig  classifies  papers  as  blotting-paper  (unsized),  printing-paper  (sized  with 
resin),  draught-paper,  letter-paper,  paper  for  account  books  and  legal  documents,  and 
covering  paper,  all  the  three  better  kinds  being  sized  with  a  mixture  of  glue  and  resin- 
size,  and  lastly  parchment  paper. 

For  testing  the  strength  of  papers  apparatus  have  been  devised  by  Heuer,  Rausch, 
and  Wendler.  Papers  are  also  arranged  in  seven  classes,  according  to  their  resistance 
to  rubbing  and  crumbling.  The  position  of  a  paper  in  this  series  is  ascertained  by 
certain  manipulations,  which  can  only  be  learned  by  practice. 

Paper-Cutting  Machine. — When  finished  by  the  machine,  the  paper  is  cut  off  into 
long  lengths  and  rolled  by  hand  for  the  manufacturers  of  drawing-  and  wall-papers, 

*  Filter  paper  should  be  free  from  soluble  matter  and  from  earthy,  alkaline,  or  metallic 
compounds,  being  as  near  as  possible  chemically  pure  cellulose.  The  finest  qualities  are  made  in 
Sweden  and  in  Germany.— [EDITOR.] 


8;o  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

scene-painters,  &c.    Attached  to  a  large  wheel  is  a  knife,  whose  regular  strokes  cut  paper 
into  the  size  required.     The  clipping  machine  is  used  for  cutting  the  edges  of  books, 
y.  Pasteboard,  &c. — Making  Pasteboard. — Pasteboard  is  made  in  three  ways  : 

(1)  By  placing  the  pulp  in  a  form — form-board. 

(2)  By  placing  several  damp  sheets  to  form  a  thick  card — elastic  pasteboard. 

(3)  By  pasting  together  the  finished  paper  sheets — sized  pasteboard. 

(1)  Form-board  is  an  inferior  kind  employed  for  ordinary  purposes  of  packing, 
bookbinding,  &c.     It  is  made  from  waste  paper,  refuse  rags,  and  the  coarser  parts  of 
the  pulp.     Clay  or  chalk  is  sometimes  present  to  25  per  cent,  of  the  weight  of  this 
pasteboard.     It  is  made  in  a  coarse  ribbed  form,  goes  through  the  same  process  of 
knotting  as  the  paper  sheet,  and  is  dried  and  pressed  under  a  roller. 

(2)  Elastic  pasteboard  is  of   better  material  and  presents  a  smoother   surface  ; 
six  to  twelve  sheets  of  paper  previously  damped  are  placed  together,  and  pressed  into 
one  compact  sheet.     A  separate  and  harder  kind  of  pasteboard  is  the  thick  elastic 
board  used  for  binding  books.     The  inner  layer  is  made  of  coarser  stuff,  sawdust,  &c. 

(3)  Sized  pasteboard,  or  cardboard,  is  made  of  two  to  fifteen  sheets  of  sized  paper, 
pressed,  and  satined.     There  are  varieties  of  this  cardboard,  such  as  Bristol-board, 
and   London-board,   the  former   being    extensively   used   for  water-colour   drawing, 
mounting-board,  ornamental  board,  &c. 

Papier-Mache  is  used  for  fancy  articles,  such  as  the  covers  for  albums,  inkstands, 
blotting-books,  paper-knives,  &c.,  as  well  as  for  the  cells  of  galvanic  batteries.  It  is 
obtained  from  old  paper  made  into  a  pulp  with  a  solution  of  lime,  and  gum  or  starch, 
pressed  into  the  form,  required,  coated  with  linseed  oil,  baked  at  a  high  temperature, 
and  finally  varnished.  The  pulp  is  sometimes  mixed  with  clay,  sand,  chalk,  &c.,  and 
other  kinds  are  made  of  a  paste  of  pulp  and  lime,  and  used  for  ornamenting  wood, 
inlaying,  &c. 

Coloured  Paper.— The  papers  made  from  coloured  rags  are  the  brown  packing-paper 
and  coarse  coloured  papers,  such  as  sugar-  and  pin-paper.  To  50  kilos,  of  dry  pulp 
coloured  pin-paper  requires  the  several  undermentioned  substances : — 

12  '05  kilos.  Lead  acetate 
Yellow |  o  -45  Potassium  bichromate 


Blue 


Green 


r 
1 1-- 


°5 
'05 
j'oo 
[•05 

Violet 1-05 

Eose 6-00 


Buff 


3-00 
3-00 


Iron  sulphate 

Potassium  f  errocj-anide 

Blue 

Yellow 

Extract  of  logwood 

Extract  of  Brazil  wood 

Oil  of  vitriol 

Chloride  of  lime 


Ultramarine  and  aniline  blue  are  also  used  in  colouring  the  paper.  In  variegated 
papers,  chemical,  mineral,  and  vegetable  colourings  are  used  according  to  the 
required  colours.  Body  colours  are  rendered  fluid  by  a  solution  of  gum  arabic  or 
alum  in  the  size,  which  can  be  applied  by  a  brush  or  sponge  when  only  one  side  is 
to  be  coloured.  Variegated  and  tapestry  papers  are  an  important  part  of  the 
manufacture. 

In  the  manufacture  of  coloured  papers  there  are  used  solutions  of  mineral  or 
organic  colours,  prepared  according  to  the  rules  of  dyeing,  and  fine  earthy  colours 
are  stirred  up  with  starch-paste  or  with  solutions  of  gum,  dextrine,  or  glue  mixed 
with  alum.  If  only  one  side  of  the  paper  is  to  be  coloured,  the  colour  is  applied 
with  a  brush  or  sponge.  Otherwise  the  sheets  are  taken  at  once  through  the  liquid. 
In  the  manufacture  of  paper-hangings  the  processes  are  similar  to  those  employed 
in  calico-printing.  This  manufacture  is  now  very  important. 


SECT.    VII.] 


PAPEE   MANUFACTURE. 


871 


Graphite  paper,  used  for  packing  up  needles,  and  other  small  and  fine  articles  of 
iron  or  steel,  with  a  view  of  preventing  rusting,  is  prepared  by  hand  with  an  addition, 
of  finely  powdered  graphite. 

Parchment  Paper. — Parchment,  although  made  of  animal  membranes,  is  often  con- 
founded with  vegetable  parchment  (phy  toper gamenf).  The  latter  is  made  of  unsized 
paper  treated  with  a  solution  of  chloride  of  zinc  or  sulphuric  acid :  i  kilo,  of 
concentrated  sulphuric  acid  and  125  grammes  of  water,  in  which  the  paper  is  immersed 
so  as  to  equally  affect  both  sides.  The  length  of  time  differs  according  to  the  quality 
of  the  paper,  the  thicker  or  firmer  paper  taking  a  longer  time  to  saturate ;  soft  paper 
will  take  five  to  ten  seconds.  It  is  then  placed  in  a  weak  solution  of  sal  ammoniac, 
rinsed  in  water  till  no  trace  of  the  acid  remains,  and  then  dried.  When  these  opera- 
tions are  effected  mechanically,  a  steam  machine  first  pulls  the  endless  paper  through 
a  vat  of  sulphuric  acid,  then  through  water,  sal  ammoniac,  and  again  water,  the 
paper  passing  on  over  cloth  rollers  to  dry,  and  finally  over  polished  rollers  to  press  and 
glaze  the  surface. 

In  Fritsch's  machine  for  parchmentising  paper,  the  paper  travels  from  the  cylinder 
A  (embraced  by  the  beak,  a,  Fig.  579,  to  regulate  its  tension),  over  the  roller,  B,  into 

Fig-  579- 


the  trough,  K,  filled  with  sulphuric  acid,  in  which 
it  is  supported  by  a  glass  roller,  C,  and  between 
the  two  glass  rods,  D,  to  the  first  press,  _£",  in 
which  the  superfluous  acid  is  squeezed  out.  The 
rollers  of  this  press  are  laid  obliquely,  so  that  the 
acid  pressed  out  may  quickly  flow  back  into  the  trough,  K,  without  flowing  along  the 
paper.  From  E  the  paper  passes  into  a  chest,  k,  filled  with  water,  and  fixed  in  the  large 
tank,  /r,  in  order  to  wash  off  the  acid  adhering  to  the  paper.  The  water  remains  in 
k  until  it  marks  about  30°  Tw.,  and  is  then  let  off  to  recover  the  acid,  whilst  its  place 
is  taken  by  fresh  water.  The  paper  is  passed  over  a  row  of  wooden  rollers,  b,  and  is 
rinsed  from  above  and  below  with  fresh  water  from  the  spirting  tubes,  s,  in  order  to 
arrive  after  the  expander,  e,  at  the  second  press,  Ez,  when  the  dilute  acid  or  the  gela- 
tinous coating  is  pressed  out.  The  paper  next  passes  through  the^trough,  Kv  filled  with 
an  alkaline  bath,  in  order  to  neutralise  any  adhering  acid,  and  for  its  second  and  third 
washings  respectively  to  the  trough,  .A"2,  with  the  spirting  tubes,  t,  and  the  trough,  K# 
with  the  spirting  tubes,  u.  After  a  passage  through  the  third  press,  Ev  the  paper  is 
passed  upon  the  drying  cylinder,  F,  heated  by  steam,  round  which  it  is  held  by  an 
endless  felt,  d.  Above  the  drying  cylinders  are  placed  the  smoothing  rollers,  H,  H^ 
the  upper  one  of  which,  Hv  is" heated  to  prevent  sweating  and  the  formation  of  rust- 
stains.  The  finished  parchment  paper  is  then  rolled  up.  For  the  press  rollers,  E^  E3, 


872  CHEMICAL  TECHNOLOGY.  [SECT.  vn. 

and  J23,  there  are  used  so-called  anti-deflection  rollers,  which  are  coated  with  a  layer  of 
caoutchouc.     The  presses  are  set  in  action  by  expansible  band  discs. 

If  dipped  in  water  parchment  paper  becomes  soft  and  limp  without  losing  its  firm- 
ness. It  is  permeable  for  liquids  only  by  dialysis.  It  is  not  attacked  by  boiling,  and 
does  not  putrefy.  From  its  valuable  properties  parchment  paper  is  suitable  for  a 
variety  of  purposes,  especially  as  a  material  for  deeds,  official  documents,  &c.,  and 
indeed  for  all  writings  the  preservation  of  which  is  important.  In  comparison  with 
ordinary  parchment  it  is  much  less  liable  to  be  destroyed  by  insects.  It  is  used  in 
bookbinders'  work,  and  as  a  substitute  for  leather — e.g.,  the  so-called  "  sweat-leathers  " 
in  hats  and  caps.  It  is  used  instead  of  animal  bladder  for  covering  glasses  of  pre- 
served fruits,  and  for  connecting  the  joints  of  distillatory,  &c.,  apparatus.  It  may  be 
cemented  together  by  means  of  cellulose  dissolved  in  cupric  ammonia.  According  to 
Ludicke  in  the  conversion  of  paper  into  parchment  paper  the  thickness  of  the  paper 
decreases  from  35  to  37  per  cent.  Its  density  increases  from  32  to  42  per  cent,  and 
it  increases  in  firmness  3*8  to  4^5  fold. 


SECTION     VIII. 

MISCELLANEOUS  ORGANO-CHEMICAL  ARTS  AND 
MANUFACTURES. 


TANNING. 

THE  operation  by  which  the  skins  of  various  animals,  more  especially  those  of 
the  larger  mammalia,  are  converted  into  leather  is  called  tanning.  By  leather 
we  understand  a  substance,  tough,  flexible,  not  harsh ;  further,  distinguished  by  re- 
sisting putrefaction  and  by  not  yielding  any  glue  when  boiled  in  water,  as  is  the  case 
with  tanned  hide,  sole  leather,  and  the  so-called  red-tanned  leather,  or  only  after  a 
very  continued  boiling,  as  with  tawed  skins  of  calves,  sheep,  or  goats.  Whatever  the 
differences  which  obtain  in  the  practical  processes  for  carrying  out  the  conversion,  the 
physical  principle  involved  is  the  same  in  all.  Knapp's  general  definition  of  leather  is 
that  it  is  skin,  in  which  by  some  means  or  other  the  agglutination  of  the  fibres  after 
drying  has  been  prevented. 

To  a  comparatively  very  recent  period  tanning  was  conducted  on  an  empirical  basis ; 
it  is  only  by  a  more  accurate  knowledge  of  the  histological  structure  of  the  skin  and 
of  the  tannin-containing  materials  that  the  real  nature  of  the  process  has  become 
known  ;  this  knowledge  being  due  chiefly  to  the  researches  of  F.  Knapp  and  Rollet. 

That  which  is  converted  into  leather  is,  however,  not  the  skin  or  hide,  but  really 
what  is  known  anatomically  as  the  corium,  that  is  to  say,  the  inner  portion  of  the 
skins,  from  which  by  mechanical  (cutting  and  scraping)  as  well  as  by  chemical  means 
(action  of  lime)  the  other  integuments  have  been  removed.  In  its  most  general  sense 
tanning  should  (i)  effect  the  prevention  of  putrefaction;  (2)  render  the  dry  skin  a 
supple,  fibrous,  tough,  non-transparent  substance,  and  not  horny  as  would  be  the  case 
were  the  skin  simply  dried.  A  well-tanned  skin  or  hide  possessing  these  properties 
is  termed  "  well  finished."  The  specific  process  of  tanning  is  of  course  preceded  by 
some  preliminary  operations,  the  aim  of  which  is  to  "  dress  "  the  skins  or  hides — that 
is,  in  scientific  terms,  to  free  the  corium  more  or  less  perfectly  from  all  other 
integuments.  Tanning  in  the  more  restricted  sense  of  the  word  may  be  effected  by  a 
great  many  organic  and  inorganic  substances ;  but  in  practice  on  the  large  scale  there 
are  employed : — 

(1)  The  tannins  of  the  vegetable  kingdom. 

(2)  Alum  and  sodium  chloride  used  in  tawing  or  white  tanning. 

(3)  Oils  and  fats — oil  tawing. 

Anatomy  of  Animal  Skin. — Leaving  the  hair  out  of  the  question,  the  skin  of  tho 
mammalia  consists  of  several  layers.  The  uppermost  of  these  in  which  the  hair  is 
growing,  the  epidermis,  is  very  thin,  semi-transparent,  and  consists  of  cells  which 
contain  nuclei.  This  epidermis  is  covered  by  a  more  or  less  horny  layer  not  possessing 
any  vital  properties,  which  gradually  wears  off,  and  is  as  gradually  replaced  by  the 
stratum  Malpighii,  or  Malpighian  net,  a  structure  consisting  of  cells  containing  fluid 


874  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

and  nuclei.  It  is  this  layer  in  which  the  nerves  and  finer  blood  vessels  are  embedded, 
together  with  the  glands  which  provide  the  perspiration.  In  the  tan-yards  this  layer 
is  known  as  the  bloom  side,  or  hair  side  of  the  skin  or  hide.  The  real  corium  or  derma, 
situated  under  the  layer  just  mentioned,  does  not  consist  of  cells,  but  is  of  a  fibrous 
texture,  and  is  that  portion  of  the  skin  which  after  tanning  constitutes  the  leather ; 
in  the  living  animal  it  is  separated  from  the  muscles  by  a  more  or  less  strongly 
developed  fat-bearing  tissue,  the  so-called  pannicuhis  adiposus,  which  is,  however, 
removed  in  the  dressing,  the  side  of  the  skin  or  hide  to  which  it  was  attached  being 
termed  the  flesh  side.  All  the  histological  constituents  of  skin  or  hide  possess  the 
property  of  swelling  up  when  put  into  hot  water,  and  of  becoming  after  more  or  less 
protracted  boiling  converted  into  glue,  more  slowly  when  the  skin  is  taken  from  old, 
more  rapidly  when  from  young  animals.  By  the  action  of  acetic  acid  the  fibrous 
tissue  of  the  skin  is  converted  into  a  jelly-like  transparent  mass,  in  which  the  fibres 
are  not  only  not  destroyed,  but  are  present  with  their  peculiar  structure.  Alkaline  lyes 
dissolve  this  tissue  but  very  slowly ;  while  lime-  and  baryta-water  have  no  other  effect 
on  it  than  simply  dissolving  therefrom  the  cellular  binding  tissue  which  permeates  it, 
and  which  is  an  albumen  compound  also  acted  upon  by  dilute  acids. 

The  various  operations  of  tanning,  more  particularly  the  preliminary  operations  of 
steeping  and  dressing,  are  based  upon  the  behaviour  of  the  different  histological 
elements  of  the  skin  and  hide  with  alkaline  and  acid  fluids  ;  but  the  real  process  of 
tanning  is  based  upon  the  behaviour  of  the  corium  with  totally  different  re-agents. 
This  latter  substance  has  the  property  of  combining  with  tannic  acid,  several  metallic 
oxides  —  viz.,  alumina  and  the  iron  and  chromium  oxides — oxidised  fatty  matter, 
the  insoluble  metallic  soaps  (compounds  of  fatty  acids — viz.,  stearic,  palmitic,  &c. — 
with  lead  oxide,  &c.),  picric  acid,  pinic  acid  (present  in  rosin),  and  other  organic 
substances,  somewhat  in  the  same  way  as  animal  and  vegetable  fibres  combine  with 
dyes  and  pigments.  In  the  most  extended  sense  of  the  word  all  these  substances  are 
tanning  agents,  because  they  possess  the  property  of  being  precipitated  on  and  in  the 
fibres  of  the  corium,  so  that  when  the  latter  is  dried  the  agglutination  of  the  fibres  is 
prevented,  and  the  natural  suppleness  and  softness  of  the  skin  preserved.  But  in  the 
case  of  the  application  of  alumina  compounds,  the  softness  is  only  imparted  to  the 
tanned  skins  by  the  operations  of  currying  and  dressing. 

Red  or  Bark  Tanning. — This  branch  of  industry  concerns  itself  with  the  conversion 
of  hides  into  ordinary  leather  by  the  use  of  tannins. 

The  tanniferous  vegetable  matters  employed  contain  as  their  essential  principle 
tannin  which  varies  in  different  plants,  but  which  has  always  an  astringent  taste  and 
an  acid  reaction ;  it  gives  a  black  or  green  coloration  with  ferric  salts,  precipitates 
solutions  of  glue  and  of  cinchonine,  and  converts  hides  into  leather.  Etti  distin- 
guishes quercitannic  acid :  ClyH1608 ;  the  first  anhydride  or  phlobaphen :  C34H3oOir ; 
the  second  anhydride  C3lH2801G ;  the  third  anhydride  or  Oser's  "  oak  red "  : 
C34H,60]5 ;  and  the  fourth  anhydride  or  Lowe's  oak-red  :  C34H24OI4.  He  considers 
this  tannic  acid  to  be  a  threefold  methylated  gallylgallic  acid.  According  to  Bottinger 
the  tannin  of  oak-bark  is  Cl9H16O10,  but  that  of  oak-wood  C^H^O^  and  the  tannin  of 
hemlock-bark  C20H1S010.  Concerning  the  tannin  of  nut-galls,  it  is  converted  by  acids 
and  by  fermentation  into  gallic  acid,  which  is  not  suitable  for  the  production  of  leather. 
Phlobaphen  is  apparently  as  important  in  tanning  as  tannic  acid  itself.  Every  tannin 
is  quickly  destroyed  by  alkaline  liquids  (lime  water,  potassa,  or  ammonia)  with  access 
of  air,  brown  humoid  products  being  formed. 

Oak  Bark. — This  substance  is  for  the  tanner  the  most  important  of  all  tannin- 
containing  materials,  and  cannot  be  replaced  by  any  other.  It  is  the  inner  bark  of 
several  kinds  of  oak,  Quercus  robur,  Q.  pedunculata,  &c.,  and  is  stripped  from  the  trees 
and  branches  when  these  have  attained  an  age  of  from  nine  to  fifteen  years,  the  bark 


.SECT,  vm.]  TANNING.  875 

when  cut  into  splints  being  termed  tan.      According  to   E.   Wolff,  the  quantity  of 
tannin  contained  in  oak-bark  is  as  follows  : — 

Tannic  acid.  Age  of  the  trees. 

In  the  crude  bark  covered  with  the  rind       io-S6  per  cent.     ...     41  to  53 
inside  layer  of  the  old  bark          .       14*43  •••     41  to  53 


inside  of  the  bark          .        ...  13-23 

crude  bark  and  inside  of  bark       .  1 1  -69 

inside  layer  and  inside  of  bark     .  13-92 

inside  of  bark        ....  I3'95 

.,  ....  15-83 


4i  to  53 
4i  to  53 
4i  to  53 
14  to  15 
2  to  7 


According  to  Buclmer's  researches  (1867)  the  quantity  of  tannic  acid  contained  in 
the  best  kinds  of  oak  bark  does  not  exceed  6  or  7  per  cent.  The  fir  bark  (produce  of 
Pinus  sylvestris)  is  one  of  the  best  tanning  materials,  and  is  frequently  used  for  sole 
leather ;  this  bark  is  stripped  off  the  trees  immediately  after  they  have  been  cut  down 
for  timber.  While  J.  Feser  found  from  5  to  15  per  cent,  of  tannin  in  this  bark, 
Dr.  Wagner  found  only  7-3  per  cent.  In  the  United  States  the  bark  of  the  Abies 
•canadensis  is  used ;  and  an  extract  is  in  the  trade  which,  according  to  Nessler's 
researches  (1867),  contains  14-3  per  cent,  of  tannic  acid.  The  extract  is  imported 
into  this  country  under  the  erroneous  appellation  of  hemlock  extract.  The  bark 
of  the  elm  with  3  to  4  per  cent,  tannin,  the  bark  of  the  horse-chestnut  with  about 
2  per  cent,  tannin,  and  beech  tree  bark  with  also  about  2  per  cent,  tannin,  are  all 
employed  for  tanning  purposes.  The  younger  branches  and  twigs  of  the  willow 
trees  yield  a  bark  (3  to  5  per  cent,  tannin)  which  is  especially  suited  for  certain 
kinds  of  glove  leather ;  while  another  kind  of  willow  bark  is  used  for  the  tanning  of 
Russia  leather. 

In  Australia  the  barks  of  several  species  of  Acacia  (wattle-barks)  are  used.  The 
most  important  species  are,  Acacia  calamifolia,  A.  pycnantha  and  A.  decurrens. 
A.  pycantha  may  contain  upwards  of  40  per  cent,  of  tannin. 

Sumac. — This  substance  is,  next  to  oak  bark,  one  of  the  most  important  tanning 
materials ;  it  is  the  product — the  leaves  and  stems — of  a  shrub,  the  so-called  tanner's 
sumac  (Rhus  coriaria  and  R.  typhina),  which  grows  wild  in  Southern  Europe  and  the 
Levant,  and  is  cultivated  in  North  America  and  Algeria.  The  shoots  from  the  roots 
-are  collected  and  planted  in  June,  and  after  some  three  years'  growth,  the  shrubs  are 
large  enough  to  admit  of  the  branches  and  leaves  being  gathered.  The  young  branches 
and  twigs  are  cut  off,  and  after  drying  in  the  sun,  the  leaves  are  beaten  off  with  sticks 
or  clubs  and  next  crushed  under  mill-stones,  sifted,  and  packed  into  sac.ks,  and  thus 
sent  into  the  market.  The  sumac  of  commerce  is  a  coarse  powder,  exhibiting  a  yellow 
or  blue-green  colour,  and  containing  12  to  16*5  per  cent,  of  tannic  acid.  By  keeping, 
the  tannic  acid  of  sumac  is  converted  into  secondary  products,  owing  to  a  spontaneous 
fermentation.  Sumac  also  contains  a  yellow  dye-stuff  which  seems  to  be  identical  with 
quercitrin.  With  sumac  should  not  be  confused  another  material  of  the  same  name, 
but  distinguished  as  Italian  or  Venetian  sumac,  and  derived  from  the  Rhus  cotinus, 
also  yielding  fustet  or  yellow  dye-wood.*  Italian  sumac  is  the  pulverised  bark  of  the 
young  twigs  and  leaves  of  this  plant,  which  under  the  name  of  ruga  grows  in  Southern 
Europe  and  also  near  Vienna ;  where  it  is  largely  used  for  tanning  purposes,  being  more 
particularly  employed  for  preparing  goat-  and  sheep-skins. 

Dividivi.—The  material  designated  by  this  name  is  the  seed  capsule  of  some  trees 
found  native  in  Central  America,  and  belonging  to  the  Ccesalpiniacice ;  these  seed 
•capsules  are  about  6  centimetres  long,  are  bent  as  an  S,  have  a  brown-red  colour,  and 
contain  olive-green  coloured,  egg-shaped,  polished  seeds.  In  1 768  the  Spaniards  brought 

*  This  substance  is  sometimes  erroneously  confounded  with  true  fustic,  the  wood  of  Morut 
tinctoria. — [EDITOK.] 


876  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

this  material  to  Europe,  where  it  is  used  for  tanning  purposes  on  account  of  the 
tannin  contained  in  the  epidermis  of  the  capsules  (more  correctly  siliquce,  or  pods). 
The  quantity  of  tannin  was  found  by  Miiller  to  be  49  per  cent.,  by  Fleck  32-4 
per  cent.,  while  Dr.  Wagner  found  from  19  to  267  per  cent.  Dividivi  is  rather  an 
expensive  tanning  material,  but  is  much  used  for  dyeing  purposes.  Among  the 
tannin-containing  substances  which  are  occasionally  imported  from  abroad  may  be 
mentioned  the  bablah,  the  produce  of  the  Acacia  bablah  and  allied  species.  This 
material  contains,  according  to  Fleck,  20-5  per  cent  tannin,  while  Dr.  Wagner  found 
14*5  per  cent.  Algarobilla,  the  seed  capsules  of  the  Prosopis  pallida,  a  native  of 
Chili,  has  been  also  occasionally  employed  as  tanning  material  in  this  country. 
Myrobalans,  the  fruit  of  Terminalia  chebula  and  of  some  allied  species,  are  largely  im- 
ported from  Bombay,  and  are  used  to  a  limited  extent  as  a  source  of  tannin,  in  which 
they  are  much  richer  than  is  sumac. 

Nut  Galls. — We  understand  by  this  name  an  excrescence  formed  on  the  leaves  of 
the  Quercus  infectoria  by  the  puncture  of  the  female  insect  of  the  Cynips  gallce  tinc- 
torice,  or  oak  wasp,  effected  in  the  leaves  and  young  twigs  in  order  to  deposit  its  eggs ; 
the  juices  of  the  tree  collect  round  the  egg,  and  on  hardening  form  the  nut-gall.  This 
material  is  best  collected  before  the  young  insect  has  become  fully  developed,  because 
then  the  gall  contains  the  largest  quantity  of  tannic  acid.  In  the  market  three 
varieties  are  met  with,  termed  black,  green,  and  white  galls.  The  black  and  green 
variety  have  been  gathered  before  the  insect  became  fully  developed  inside  the  nut ; 
these  galls  therefore  do  not  exhibit  outwardly  any  hole  or  opening,  but  on  breaking 
the  gall  there  will  be  observed  in  the  centre  a  small  cavity  surrounded  by  a  light  brown 
friable  substance,  which  contains  the  larva  of  the  insect.  Galls  are  generally  spherical, 
but  exhibit  small  irregularities  of  surface,  and  are  of  a  black-green  or  grey  colour. 
The  white  galls  are  gathered  after  the  insect  is  fully  developed,  and  has  escaped  by  per- 
forating the  tissue  of  the  gall.  This  variety  is  more  spongy,  and  its  colour  is  a  red-brown 
or  brown-yellow.  Galls  of  good  quality  are  obtained  only  from  warmer  countries,  for 
although  galls  are  formed  in  our  climate  upon  oak  leaves,  the  quantity  of  tannin 
contained  amounts  to  only  3  to  5  per  cent.  Fehling  found  in  Aleppo  galls  from 
60  to  66  per  cent,  of  tannic  acid,  while  Fleck  found  58*71  per  cent,  of  this  acid,  and 
5'9  per  cent,  gallic  acid. 

Valonia  Nuts. — These  are  the  dried  immature  acorn  cups  of  two  species  of  oak, 
Quercus  cegilops  and  Valonia  camata,  both  being  employed  in  tannin  as  well  as  the 
valonia  nuts  produced  by  the  puncture  of  the  Cynips  quercus  calycis.  The  quantity  of 
tannic  acid  met  with  in  these  substances  averages  from  40  to  45  per  cent.  In  the  so- 
called  valonia  flour,  obtained  by  grinding  the  acorns  belonging  to  this  class,  Dr.  Wagner 
found  from  19  to  27  per  cent,  of  tannin.  The  acorn  cups  are  imported  under  the  name 
of  drillot,  and  according  to  Rothe  these  contain  from  43  to  45  per  cent,  of  tannin. 

Chinese  Galls. — Under  this  name  has  been  known  in  the  trade  since  1847,  an(* 
imported  from  Japan,  China,  and  Nepaul,  the  excrescence  upon  a  kind  of  sumac,  Rhus 
javanica  and  R.  semialata,  produced  by  the  puncture  of  the  Aphis  sinensis.  This  gall- 
nut  is  rather  oblong  or  bean-shaped,  with  an  irregular  surface  covered  with  a  yellow- 
grey  felt;  the  length  varies  from  3  to  10  centimetres,  and  the  thickness  from  1-5  to 
4  centimetres;  the  texture  is  horny;  the  quantity  of  tannin  varies  from  60  to  70 
per  cent. 

Cutch. — The  substances  long  known  in  medicine  under  the  name  of  catechu  and 
kino  have  been  for  the  last  fifty  years  also  employed  as  tannin  materials.  They  are 
vegetable  extracts,  that  known  as  cutch  (trade  term)  being  obtained  by  exhausting 
with  boiling  water  the  pith  of  the  wood  of  the  Acacia  catechu,  a  tree  met  with  in 
different  parts  of  the  tropical  regions  of  Asia.  The  liquor  obtained  by  boiling  the 
pith-wood  in  water  is  inspissated,  and  on  cooling  forms  a  solid  mass,  which  is  brought 


SECT,  viii.]  TANNING.  877 

into  commerce  in  various  shapes  and  named  after  the  port  of  shipment.  Bombay 
cutch  is  met  with  in  the  shape  of  large  square  blocks,  through  and  round  which  the 
leaves  of  a  kind  of  palm-tree  are  placed.  The  colour  of  the  fracture  of  this  substance 
is  a  brown-black  with  a  fatty  gloss ;  externally  the  mass  is  dull  and  friable.  Bengal 
cutch  is  prepared  from  the  nuts  of  the  Areca  catechu,  and  occurs  in  commerce  as  large, 
irregularly  shaped  cakes,  externally  brown,  internally  more  yellow-coloured.  Gambir 
is  a  variety  of  cutch  prepared  in  Sumatra,  Singapore,  and  Malacca,  and  especially  in 
the  Island  of  Eiouw,  from  the  leaves  and  stems  of  the  Uncaria  gambir.  The  dry 
extract  occurs  in  commerce  in  small  cubical  blocks,  which  are  light,  of  a  cinnamon- 
colour,  and  very  friable,  the  fracture  being  earthy.  All  these  substances  contain  about 
40  to  50  per  cent,  of  a  peculiar  kind  of  tannic  acid  or  catechu-tannic  acid,  the  formula 
of  which,  according  to  J.  Lowe,  is  C15H1406,  as  well  as  a  peculiar  acid,  catechueic  acid, 
C16HU06,  not  of  much  use  in  the  tanning  process. 

Kino. — This  drug  is  very  similar  to  catechu,  and  is  said  to  be  the  extract  prepared 
from  various  plants — viz. : 

African  kino  from Pterocarpus  erinaceus. 

East  Indian  kino  from Pterocarpus  marsupium. 

East  Indian  kino,  according  to  others,  from  .         .  Butea  frondosa. 

West  Indian  kino  from  ......  C.uccolaba  uvifera. 

Australian  kino  from Eucalyptus  resinifera. 

Kino  is  met  with  in  small,  angular,  brittle,  brown-red  to  black-coloured  masses, 
the  powder  of  which  is  always  brown-red.  It  is  soluble  in  hot  water  and  alcohol, 
yielding  a  blood-red  solution  of  an  astringent  and  sweet  taste.  Kino  contains  from 
30  to  40  per  cent,  of  a  tannic  acid  similar  to  that  contained  in  cutch;  both  of  these 
materials  are  especially  useful  in  so-called  quick  tanning. 

Estimation  of  the  Value  of  the  Tanning  Materials. — The  value  of  all  the  tanning 
materials  entirely  depends  upon  the  quantity  of  tannic  acid  they  contain.  The  latter 
is  soluble  in  water,  and  more  or  less  completely  precipitated  from  that  solution  by 
various  re-agents,  such  as  glue  and  animal  skin,  copper  acetate,  iron  acetate, 
cinchonine  and  quinine,  while  a  solution  of  potassium  permanganate  completely 
destroys  the  tannic  acid.  Upon  these  properties  the  following  properties  have  been 
based  for  the  approximative  estimation  of  the  quantity  of  tannic  acid  present  in  various 
tanning  materials : — 

1.  Precipitation  by  glue  or  skin  : — 

(a)  Weighing  of  the  skin  before  and  after  immersion  in  the  liquor  containing  tannin,  the 

increase  of  weight  giving  the  quantity  of  tannic  acid  (DAVY). 
(6)  Precipitation  with  gelatine  solution  of  known  strength  (FEHLING). 

(c)  Titration  by  means  of  aluminated  solution  of  glue  (G.  MCLLER). 

(d)  First  discover  the  specific  gravity  of  the  tannin  solution  by  means  of  an  areometer, 

next  remove  the  tannin  by  skin,  and  then  again  take  specific  gravity  of  liquid,  the 
decrease  being  proportionate  to  the  quantity  of  tannin  in  the  original  liquor  (C. 
HAMMER). 

2.  Precipitation  of  tannin  by  copper  acetate,  and  estimation  of  the  relation  between  tannin 

and  copper  oxide  in  the  precipitate : — 

(a)  Volumetrically  (H.  FLECK)  ;  or 

(b)  By  the  gravimetrical  method  (E.  WOLFF). 

3.  Volumetrical  estimation  of  tannin  by  iron  acetate  (R.  HANDTKE). 

4.  Oxidation  of  tannic  acid  by  potassium  permanganate  (LoWENTHAL). 

5.  Precipitation  of  tannin  by  means  of  cinchonin,  the  solution  of  which  is  tinged  red  by  means 

of  magenta,  i  gramme  of  quercitannic  acid  requires  07315  gramme  cinchonine, 
equal  to  4'523  grammes  of  crystallised  neutral  sulphate  of  cinchonin  (R.  WAGNER). 

The  subjoined  table  shows  the  composition  of  several  tanning  wares  :— 


878 


CHEMICAL  TECHNOLOGY. 


[SECT.  viii.. 


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The  Hides. — The  skins  of  almost  all  quadrupeds  might  be  converted  into  leather  by 
tanning ;  but  the  tanner  chiefly  prepares  his  leather  from  the  hides  of  cattle,  occasion- 
ally from  those  of  horses  and  asses,  as  well  as  of  pigs.  The  quality  of  the  hides  not 
only  depends  upon  the  kind  of  animal,  but  also  upon  its  fodder  and  mode  of  living. 
The  hides  of  wild  cattle  yield  a  more  compact  and  stronger  leather  than  those  of 
our  domesticated  beasts;  among  these  the  stall-fed  have  better  hides  than  the  meadow- 
fed  or  grazing  cattle.  The  thickness  of  the  hide  varies  considerably  on  different  parts 
of  the  body,  the  thickest  part  being  near  the  head  and  the  middle  of  the  back,  while  at 
the  belly  the  hide  is  thinnest.  These  differences  are  less  conspicuous  in  sheep,  goats,. 
and  calves.  As  regards  sheep,  it  would  appear  that  their  skin  is  generally  thinnest 
where  their  wool  is  longest. 

The  hides  of  bulls  and  oxen  yield  the  best  and  stoutest  leather  for  soles.  In  the 
raw — untanned — state,  and  with  the  hair  still  on,  the  hides  are  termed  "  green  "  or 
"  fresh."  Fresh  or  green  hides  are  supplied  to  the  tanners  by  the  butchers,  or  are 
imported  either  dry  or  salted.  A  hide  weighing  in  the  fresh  state  from  25  to  30  kilos, 
loses  by  drying  more  than  half  its  weight.  South  America  (Bahia,  Buenos  Ayres,  &c.y 
exports  a  large  quantity  of  hides,  both  dry  as  well  as  salted,  and  cured  by  smoking. 
The  hides  of  cows  yield  generally  an  inferior  grained  leather ;  but  South  American 
cow  hides  may  be  worked  for  light  sole  leather.  Calves'  hides,  again,  are  thinner,  but 
when  well  tanned,  curried,  and  dressed,  yield  a  very  soft  and  supple  upper  leather  for 
boots  and  shoes.  Horse  hides  are  only  tanned  for  saddlery  purposes,  while  sheep-  and 
goat-skins  and  the  skins  of  lambs  are  tanned — or  more  generally  tawed — for  the 
purpose  of  making  wash-leather,  morocco,  glove-leather,  bookbinders'  leather.  Pigs' 
hides  and  seals'  skins  are  tanned  for  saddlery  purposes.* 

The  Several  Operations. — The  several  operations  of  the  oak  bark  tanning  process 
may  be  reduced  to  three,  viz. : — A.  The  cleansing  and  dressing  of  the  hide  on  the  hair 
and  flesh  side ;  in  other  terms,  the  separation  of  the  corium  from  the  other  integu- 
ments. B.  The  true  tanning.  C.  The  currying  and  dressing  operation,  by  which  the 
tanned  hide  becomes  a  saleable  article.  These  three  operations  are  again  subdivided  as- 
follows : —  > 

A.  The  cleansing  of  the  hide  : — 

(1)  Steeping  and  macerating  the  hide.          (3)  Dressing  the  hair  side. 

(2)  Dressing  the  flesh  side.  (4)  The  swelling  of  the  cleansed  hide. 


*  The  hide  of  the  porpoise  yields  an  excellent  leather  for  stout  boots. — [EDITOR.] 


SECT,  viii.]  TANNING.  879 

B.  The  tanning  of  the  cleansed  hide,  performed  either  by  placing  it  in  tanks  or  pits 
with  oak  bark  and  water,  or  in  a  liquor  of  these  previously  prepared,  or  by  the  so-called 
quick  method. 

C.  The  dressing  and  currying  of  the  tanned  hides,  by  which  is  understood  all  the 
operations  which  tend  to  improve  the  compactness  of  texture,  or  give  a  better  grain 
and  better  appearance  to  the  leather,  together  with  softness,  toughness,  suppleness,  and 
colour. 

A.  Cleansing  the  Hides. — This  operation  includes : — (i)  The  steeping  or  macerating 
of  the  hide  in  water  for  the  purpose  of  rendering  the  texture  uniformly  soft  and 
so  supple  that  it  may  be  bent  without  danger  of  cracking,  while,  on  the  other  hand, 
steeping  also  effects  a  cleansing  of  the  hide  by  removing  from  it  blood  and  dirt.  The 
fresh  hides  of  recently  slaughtered  animals  require  a  maceration  in  water  for  some 
two  or  three  days,  but  dried,  cured,  or  salted  hides  have  to  be  left  macerating  for 
some  eigLt  to  ten  days.  This  operation  should,  if  possible,  be  carried  on  in  a  stream 
of  water ;  but  if  there  is  no  such  convenience,  then  the  hides  are  placed  in  large  tanks  ; 
in  either  case  the  hides  are  taken  out  twice  daily  and  put  back  into  the  water 
again.  When  the  hides  have  become  quite  soft,  they  are — (2)  cleansed  or  dressed  on. 
the  flesh  side  by  being  placed  with  the  hair  side  downwards  on  a  "  tree,"  a  stout  semi- 
circular plank,  one  end  of  which  is  placed  on  the  ground  while  the  other  is  supported 
by  a  trestle,  so  that  the  plank  is  in  a  sloping  position.  The  workman  has  a  so-called 
dressing-knife,  a  tool  to  which  handles  are  fastened,  and  which  is  bent  so  as  to  form  a. 
slight  curve ;  with  this  knife  he  shaves,  or,  as  it  were,  planes  off,  from  the  hide  all  fatty 
tissue  and  integuments  which  are  situated  between  the  hide  and  the  muscles.  At  the 
same  time  the  water  is  squeezed  out  of  the  hide  to  some  extent.  After  a  preliminary 
or  first  dressing,  the  hides  are  again  placed  for  twenty -four  hours  in  water;  the 
dressing  and  planing  is  then  quite  finished,  and  the  hides  having  been  well  washed,  are 
left  to  drain  on  the  tree  ready  for  removing  the  hair.  In  some  instances  the  hides  are 
washed  by  the  aid  of  "  possing-sticks,"  and  "  fulled  "  by  means  of  machinery,  by  which 
the  operation  is  greatly  shortened,  so  much  so,  that  two  to  three  days  suffice,  instead 
of,  as  is  usual  by  the  aid  of  manual  labour,  eight  to  ten  days.  (3)  This  operation  aims 
at  the  removal  from  the  corium  of  the  epidermis  and  hair-containing  integuments.  As 
the  hair  and  integuments  connected  therewith  are  very  firmly  attached  to  the  corium, 
the  removal  can  only  be  safely  proceeded  with,  so  as  to  leave  the  corium  uninjured, 
by  the  employment  of  a  menstruum,  which  more  or  less  dissolves  and  causes  the 
epidermis  to  swell  up.  For  this  purpose  the  hides  are  usually  placed  in  lime-pits,  the 
effect  of  the  lime  being  the  partial  dissociation  (in  an  anatomical  sense)  of  the 
epidermis,  so  that  it  and  the  hairs  may  be  readily  removed  by  mechanical  means. 

The  effect  is  usually  obtained  by — (a)  Sweating ;  (6)  Liming ;  (c)  Application  of  rusma 
or  compounds  of  calcium  sulphide. 

(a)  A  semi-putrefactive  fermentation  called  sweating  is  employed  in  the  case  of 
thick  hides,  such  as  serve  for  sole  leather,  which  are  not  placed  in  lime  owing  to  the 
fact  that  it  cannot  be  completely  removed,  and  would  render  the  leather  brittle.  The 
operation  of  sweating  consists  in  placing  the  hides  one  upon  the  other,  the  flesh  side 
turned  inward,  some  salt  or  crude  wood  vinegar  having  been  first  rubbed  in,  in  a  tank, 
or  box,  which  can  be  closed,  so  that  the  heat  generated  by  the  fermentation  which  sets 
in  may  be  confined  as  much  as  possible  to  aid  the  action.  As  soon  as  the  evolution  of 
ammonia  is  perceptible,  the  hides  are  ready  for  the  removal  of  the  hair,  which  is 
shaved  off,  together  with  the  epidermis,  by  the  aid  of  the  dressing-knife.  Instead  of 
causing  the  sweating  to  be  done  by  fermentation,  the  hides  are  sometimes  hung  on  laths 
in  rooms  either  heated  by  means  of  steam  or  by  fire.  A  temperature  of  from  30°  to  50° 
should  be  kept  up,  together  with  a  good  current  of  steam,  by  which  the  epidermis  is 
thoroughly  softened.  In  order  to  prevent  any  injury  to  the  corium,  the  hides  are 


88o  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

sometimes  submitted  to  what  may  be  termed  a  cold  sweating  process,  consisting 
essentially  in  placing  the  hides  in  water-tight  tanks,  in  which  there  is  a  constant 
current  of  fresh  water,  the  temperature  being  kept  at  from  6°  to  12°.  The  hides  thus 
submitted  to  a  constantly  moist  atmosphere  become,  after  from  six  to  twelve  days,  with- 
out any  perceptible  putrefaction,  fitted  for  the  removal  of  the  epidermis  and  hair. 

(5)  The  liming  of  the  hides  not  only  prepares  them  for  the  removal  of  the  hair,  but 
also  saponifies  the  fatty  matter ;  and  though  the  lime  soap  thus  formed  is  insoluble  in 
water,  it  is  removed  by  subsequent  mechanical  and  chemical  operations.  The  operation 
of  liming  is  carried  on  in  pits,  into  which,  along  with  milk  of  lime,  the  hides  are  placed 
so  as  to  be  quite  covered.  Usually  several  (three  to  five)  pits  are  in  use  at  once,  each 
of  which  contains  a  different  quantity  of  lime.  That  the  milk  of  lime  should  be  fre- 
quently stirred  in  these  pits  is  of  course  evident.  The  hides  remain  in  the  lime-pits  for 
from  three  to  four  weeks. 

(c)  The  very  thin  skins  of  the  smaller  animals  will  neither  sustain  sweating  nor 
liming,  and  are  therefore  treated  with  rusma,  a  salve-like  mixture  of  orpiment  i  part, 
with  2  to  3  parts  slaked  lime.  By  the  rubbing  in  of  this  mixture  on  the  hair  side  of 
the  skins,  the  hairs  are  so  softened  as  to  make  their  removal  an  easy  matter.  Bottger 
states  that  calcium  hydrosulphuret  has  the  same  effect ;  hence  the  lime  of  the  purifiers 
of  the  gas-works  have  been  of  late  years  frequently  employed  for  treating  hides  as 
well  as  skins,  with  the  additional  advantage  of  yielding  a  better  leather. 

Stripping  off  the  Hair. — As  soon  as  the  hides  are  sufficiently  prepared  to  admit  of 
the  removal  of  the  hair  and  epidermis,  they  are  stretched  out  on  the  tree  and  the 
integuments  peeled  off  by  the  aid  of  the  blunt  dressing-knife.  In  order  to  give  to  the 
dressing-knife  a  better  grip,  the  workman  strews  some  fine  sand  on  the  hide,  and  if  he 
has  to  deal  with  very  heavy  and  thick  hides,  uses  a  large  and  rather  sharp  knife. 
When  the  hair  and  the  epidermis  have  been  removed,  the  hides  are  again  washed  and 
macerated  in  water,  and  after  this  dressed ;  that  is  to  say,  reduced  as  much  as  possible 
to  an  equal  thickness,  while  the  waste — tail,  leg,  and  head-pieces — are  cut  off,  and  the 
hide  planed,  thereby  losing  some  10  to  12  per  cent,  in  weight. 

Swelling  the  Hides. — The  aim  of  this  operation  is  to  remove  the  lime,  and  also  to 
render  the  corium  more  capable  of  readily  absorbing  the  tan  materials.  This  end  is 
attained  by  placing  the  hides  in  a  so-called  sour  bath,  made  of  refuse  malt  and  bran, 
which  by  acid  fermentation  yields  as  active  principles  propionic,  lactic,  and  butyric 
acids. 

The  lime  is  removed  from  the  dressed  hides  when  placed  in  this  acid  liquid,  and 
the  lime-soap  present  becoming  decomposed,  the  fatty  acids  set  free  float  on  the 
surface  of  the  liquid.  The  soluble  lime  salts  are  completely  removed  from  the  hides 
by  a  subsequent  thorough  washing  with  water.  The  thickness  of  the  hides  is  doubled 
by  the  swelling  action  of  the  acid  liquid,  aided  by  the  mechanical  action  of  the  carbonic 
acid  evolved  from  the  calcium  carbonate  deposited  within  the  fibres  of  the  hides ;  while 
the  butyric  acid  fermentation  distends  the  fibres  of  the  hides  by  the  gases  thereby 
evolved.  When  the  hides  have  not  been  treated  with  lime  but  have  been  submitted 
to  a  "  sweating,"  they  do  not  require  the  acid  bath,  but  are  simply  placed  in  water  for 
the  purpose  of  swelling  them.  Yet  the  sour  bath  is  preferable  owing  to  its  more 
regular  action. 

Instead  of  using  the  preceding  mixture  for  the  purpose  of  removing  the  lime  and 
of  swelling  the  hides,  they  are  often  placed  in  acid  tan.  liquor  (red  tan  liquor) — that 
is  to  say,  a  liquor  containing  exhausted  oak  bark  solution  which  has  served  for 
tanning.  This  liquor  appears  to  contain  also  large  quantities  of  lactic  and  butyric 
acids.  The  dressed  hides  are  first  placed  in  a  diluted  red  liquor,  and  then  in  a 
stronger  liquor,  this  operation  taking  some  twelve  to  fourteen  days.  Macbride  and 
Seguin  have  proposed  to  substitute  very  dilute  sulphuric  acid  (i  in  1500),  but  although 


SECT,  viii.]  TANNING.  88 1 

by  the  use  of  this  acid  the  operation  of  swelling  is  rendered  far  more  rapid,  the 
quality  of  the  leather  is  impaired.  Phosphates  and  animal  excreta  which  contain  a 
large  quantity  of  uric  acid,  such  as  that  of  dogs  and  of  pigeons,  have  been,  and  in 
many  cases  are  still,  used  for  the  purpose  of  swelling  hides,  especially  skins  of  sheep, 
calves,  and  goats. 

B.  The  Tanning. — The  main  object  of  the  operations  just  described  is  first  to  obtain 
the  corium  as  much  as  possible  separated  from  the  other  integuments  and  textures  be- 
longing to  the  skin,  and  next  to  render  the  corium  as  much  as  possible  permeable  by 
the  liquor  in  which  the  vegetable  matter  containing  tannin  is  dissolved.  In  practice 
it  is  taken  for  granted  that  a  dry  hide  gains  one-third  in  weight  by  being  converted 
into  leather,  consequently  it  absorbs  that  proportion  of  tannin. 

The  impregnation  of  the  fibres  of  the  hide  or  skin  with  tannin  is  effected  by  two 
different  methods,  viz. : — 

(1)  By  placing  the  hides  between  layers  of  oak  bark  chips  in  a  tank,  so-called  tan- 

ning in  the  bark ;  or 

(2)  By  immersing  the  hides,  first  in  a  dilute,  and  then  in  a  concentrated  aqueous 

infusion  of  oak  bark. 

(i)  Tanning  in  Bark. — This  mode  of  tanning  is  at  the  present  time  confined  to 
heavy  hides  intended  for  sole  leather.  The  tanks  in  which  this  operation  is  carried 
on  are  made  of  wood,  either  oak  or  fir,  are  of  course  watertight,  and  are  usually  sunk 
into  the  soil.  Brick  cisterns  lined  with  cement  are  occasionally  used,  but  are  objec- 
tionable, at  least  when  newly  built,  on  account  of  the  deteriorating  action  of  the 
lime  and  cement  upon  the  oak  bark.  In  some  parts  of  Germany  tanks  constructed 
of  slabs  of  slate  or  sandstone  are  used.  Each  tank  has  sufficient  capacity  to  contain  from 
50  to  60  hides.  On  the  bottom  of  the  tank  is  first  placed  a  layer  of  exhausted  (spent) 
tan,  and  upon  this  a  layer  of  some  3  centimetres  in  thickness  of  fresh  bark,  then  a 
hide  with  the  hair  side  downwards,  again  a  fresh  layer  of  oak  bark,  and  again  a  hide, 
alternately  until  the  tank  is  nearly  filled,  care  being  taken  to  put  some  more  bark  on 
the  thickest  part  of  the  hides,  and  to  fill  not  only  all  interstices  with  bark,  but  to  put 
on  the  top  a  layer  of  some  30  centimetres  thickness  of  spent  tan.  Water  is  next 
poured  into  the  tank  until  it  stands  a  few  centimetres  above  the  topmost  hide  ;  this 
having  been  done,  a  lid — in  England  loose  planks — is  placed  on  the  tank,  the  contents 
of  which  are  left  undisturbed  for  some  time.  When  Valonia  flour  is  employed  with 
the  oak  bark  only  half  the  quantity  of  the  latter  is  necessary. 

The  hides  are  left  in  "  the  first  bark"  for  from  eight  to  ten  weeks,  the  period  being  a 
little  shortened  if  Valonia  flour  is  also  used.  Before  all  the  tannin  has  been  absorbed, 
and  as  a  consequence  the  formation  of  volatile  and  odorous  acids  (valerianic,  butyric, 
<fec.)  has  commenced,  the  hides  are  transferred  to  another  tank,  and  again  placed  be- 
tween alternate  layers  of  fresh  bark,  the  only  difference  in  the  arrangement  being  that 
the  hides  which  were  first  placed  on  the  top  are  now  laid  at  the  bottom  of  the  tank. 
The  hides  are  now  left  for  three  or  four  months,  so  as  to  thoroughly  absorb  the  tannin. 
They  are  next  placed  for  some  four  or  five  months  in  another  tank  which  contains  less 
bark.  In  the  case  of  very  heavy  and  thick  hides  the  process  is  repeated  four  or  five 
and  even  six  times.  The  quantity  of  bark  required  for  obtaining  thoroughly  well- 
tanned  leather  depends  partly  on  the  quality  of  the  bark  and  somewhat  on  the  condi- 
tion of  the  hides.  Usually  the  tanners  reckon  that  the  quantity  of  bark  required 
amounts  to  from  four  to  six  times  the  weight  of  the  dry  hides ;  and  taking  the  weight 
of  these  at  an  average  of  20  kilos  there  will  be  required  : — 

For  the  first  tank  40  kilos,  of  bark 
„        second      35  „ 

„        third        30  „ 

105  „ 


832  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

A  dried  and  well-tanned  hide  weighs  about  22  kilos.,  or  from  10  to  12  per  cent, 
more  than  the  dry  raw  hide.  A  thoroughly  tanned  hide  exhibits,  when  cut  with  a 
sharp  knife,  a  uniform  texture,  free  from  fleshy  or  horny  portions,  while  the  grain  on 
the  hair  side  should  not,  on  being  bent,  slowly  exhibit  signs  of  cracking. 

(2)  Tanning  in  Liquor. — The  thinner  hides,  and  indeed  most  skins  (when  tanned, 
as  distinguished  from  tawing),  are  placed  in  infusions  of  the  tannin-containing  mate- 
rial. There  are  various  methods  in  use  for  this  operation,  which  is  based  mainly  upon 
a  thorough  uniform  swelling  of  the  hides,  so  that  when  these  are  placed  in  weak 
liquors  the  tannin  may  penetrate  readily  and  uniformly.  The  hides  are,  in  fact,  very 
gradually  tanned.  When  taken  from  the  liquor  the  fluid  is  forced  by  mechanical 
means  out  of  the  hides  before  they  are  placed  in  a  stronger  liquor,  which  is  obtained 
by  exhausting  the  tanning  materials  by  the  aid  of  cold  water.  The  thinner  kinds  of 
hides  are  thoroughly  tanned  in  from  seven  to  eight,  the  heavier  hides  in  from  eleven  to 
thirteen  weeks. 

Quick  Tanning. — Many  methods — some  quite  impracticable,  and  most  of  them 
thoroughly  irrational — have  been  proposed-  for  converting  hides  into  leather  in  a  very 
short  time.  Of  these  different  methods  we  briefly  mention  the  following  : — (i)  The 
hide  is  simply  placed  in  an  infusion  of  the  tannin-containing  material — Macbride's 
process,  improved  by  Seguin  (1792).  Application  of  hydrostatic  pressure  to  force  the 
liquor  through  the  hides,  kept  from  contact  with  each  other  by  a  stout  woollen 
tissue.  (2)  Circulation  of  the  fluid  containing  tannin,  several  tanks  being  connected 
together  by  means  of  pipes,  and  the  liquor  being  forced  through  the  tanks  by  means 
of  pumps  (Ogereau,  Sterlingue,  and  Turnbull's  methods).  (3)  The  hides  are  sewn 
together  so  as  to  form  sacks,  which  are  filled  with  oak  bark  chips  and  water,  and  then 
placed  in  an  aqueous  solution  of  cutch,  to  which,  in  order  to  increase  its  specific 
gravity,  coarse  molasses  is  added— Turnbull's  method  by  increased  endosmose.  At 
the  time  this  mode  of  proceeding  was  brought  forward,  the  diffusion  of  liquids 
by  dialysis  (discovered  by  Graham  in  1861)  was  unknown.  (4)  Motion  of  the  hides 
in  the  tannin-containing  liquids,  the  hides  being  placed  in  a  cylinder  constructed  of 
wooden  laths,  so  as  to  leave  open  spaces  between  them.  This  cylinder  is  immersed 
horizontally  in  the  liquid  to  a  greater  or  less  depth,  so  that  in  every  revolution  the 
hides  are  alternately  in  and  out  of  the  liquid — Brown,  Squire,  and  C.  Knoderer's 
methods.  (5)  Application  of  mechanical  pressure  to  the  hides,  which  having  been 
from  time  to  time  removed  from  the  tanning  tanks,  are  placed  upon  perforated  planks, 
and  either  pressed  under  a  heavy  roller  or  are  placed  in  a  press — Jones,  Nossiter,  Cox, 
and  Herapath's  method.  (6)  Application  of  hydrostatic  pressure  for  the  purpose  of 
causing  the  tan-liquor  to  penetrate  the  hides,  which  are  sewn  together  so  as  to  form 
bags,  which,  having  been  filled  with  oak  bark  liquor,  are  placed  in  suitably  constructed 
vessels,  so  that  hydraulic  pressure  may  be  applied  without  fear  of  bursting  the  bags ;  or 
the  hides  are  fastened  by  means  of  screws  and  bolts,  placed  on  a  framework  which  is 
immersed  in  a  well-constructed  cistern  filled  with  tan-liquor,  hydraulic  pressure  being 
applied — Drake,  Chaplin,  and  Sautelet's  methods.  (7)  Snyder's  method  of  punctation, 
consisting  in  perforating  the  hide  over  its  whole  surface,  the  punctation  being  effected 
by  sharp  needles,  so  as  to  constitute  artificial  pores.  The  experiments  of  Knapp  have 
proved  the  thorough  irrationality  of  this  plan,  it  having  been  found  that  the  hide  is  so 
permeable  to  tannin-liquor  that  a  piece  of  calf-skin,  when  placed  iji  a  solution  of  tannin 
of  the  consistency  of  syrup,  is  thoroughly  well  tanned  in  about  an  hour's  time. 
(8)  Application  of  a  vacuum  by  placing  the  hides  in  a  vessel  from  which  the  air  may  be 
withdrawn  by  the  aid  of  air-pumps ;  tan  liquor  having  been  forced  into  the  vessel,  the 
air  is  re-admitted  and  again  withdrawn — Knowly  and  Knewsbury's  plan.  Knoderer 
has  recently  found  that  by  a  judicious  combination  of  the  vacuum  method,  followed  by 
motion  and  fulling  of  the  hides  in  the  tan-liquor,  the  operation  of  tanning  is  much 


viii.]  TANNING. 


883 


shortened.     The  reader  should  bear  in  mind  that  the  methods  here  alluded  to  are  not 
•now  in  general  use. 

Dressing  or  Currying  the  Leather. — When  the  hides  have  been  converted  into 
leather  by  the  processes  described,  they  are  not  by  any  means  fit  for  use  nor  ready 
for  sale  as  a  finished  material,  but  require  to  be  dressed,  or,  as  it  technically  termed, 
•curried,  an  operation  not  necessarily  performed  by  the  tanner — at  least,  not  in 
England  and  France.  The  several  operations  are  not  similar  for  all  kinds  of  leather, 
but  depend  to  some  extent  upon  the  use  to  which  it  is  intended  to  be  put.  For  in- 
stance, sole  leather  is  submitted  simply  to  a  process  the  object  of  which  is  to  render 
it  sufficiently  stiff  and  compact,  so  as  not  to  alter  its  shape  by  wear. 

Sole  Leather. — The  dressing  or  currying  of  this  kind  of  leather  consists  mainly  in 
submitting  it  to  a  mechanical  operation  of  hammering,  by  which  the  material  is 
rendered  more  compact.  As  soon,  therefore,  as  the  hides  are  taken  from  the  tanning 
tanks,  the  adhering  spent  tan  is  brushed  off  with  a  broom,  after  which  the  hide  is  dried 
in  a  cool  place,  and  when  dry  is  laid  flat  upon  a  polished  stone  slab,  and  then  beaten 
with  wooden  or  iron  hammers,  an  operation  in  large  establishments  performed  by 
.hammers  moved  by  machinery. 

Upper  Leather. — The  dressing  of  this  kind  of  leather,  chiefly  used  by  saddlers  and 
boot  and  shoe  makers,  is  a  far  more  complicated  process,  and  depends  in  a  great  mea- 
sure on  the  use  for  which  the  leather  is  intended. 

The  Paring. — The  first  of  these  operations  is  the  paring  or  whitening,  which 
means  the  cutting  away,  by  the  aid  of  a  tanner's  shaving-knife,  of  all  portions  of 
the  hide  which  are  too  thick,  so  that  the  whole  hide  may  be  made  of  uniform 
thickness.  This  operation  is  carried  on  upon  the  tanner's  "  wooden  leg,"  the  hide 
being  placed  with  the  hair-side  downwards.  When  goat,  lamb,  sheep,  or  calf- 
skins are  to  be  pared,  they  are  placed  upon  a  polished  slab  of  marble,  and,  having 
been  well-stretched,  the  raw  or  projecting  parts  are  cut  off  with  the  tanner's  shaving- 
knife. 

The  Scraping  or  Smoothing. — The  aim  of  this  operation  is  similar  to  that  of  the 
former,  and  more  particularly  is  employed  in  the  case  of  leather  intended  for  making 
gloves.  The  leather  is  first  dried  and  next  fixed  on  the  "  perching-stick,"  one  end  of 
the  skin  remaining  free,  the  other  being  taken  hold  of  by  the  operator  with  a  pair  of 
forceps.  The  skin  having  been  stretched,  the  perching-knife,  a  highly  polished  some- 
what convex  steel  disc  of  from  1 8  to  30  centimetres  diameter,  and  provided  in  the  centre 
with  an  opening  fitted  with  a  piece  of  leather  serving  as  a  handle,  is  brought  into  use, 
the  portions  of  the  skin  which  require  to  be  pared  off  being  usually  indicated  by  being 
rubbed  over  with  chalk. 

Graining  the  Leather. — As  in  consequence  of  the  drying  of  the  leather  the  grain 
has  become  flat,  smooth,  and  unequal,  it  is  raised  by  an  operation  performed  by  means 
of  the  pommel,  also  termed  the  graining-  or  crimping-board,  a  piece  of  hard  wood 
30  centimetres  in  length  by  10  to  12  centimetres  breadth,  flat  and  smooth  on  the  top, 
but  on  the  opposite  side,  in  the  direction  of  the  length,  somewhat  curved,  so  that  it  is 
thickest  in  the  middle,  this  part  being  provided  with  parallel  notches,  which  are 
occasionally  sharpened  by  means  of  a  file ;  a  leather  strap  is  fastened  to  the  top  as  a 
handle.  The  leather  to  be  grained,  having  been  placed  on  the  dressing-table,  is 
fastened  to  the  edge  of  the  wooden  board  by  means  of  iron  clamps,  and  those  portions 
of  the  leather,  the  grain  of  which  has  to  be  raised,  having  been  somewhat  bent,  are 
rubbed  with  the  pommel  so  as  to  render  the  grain  uniformly  visible. 

Polishing  with  Pumice-Stone. — Such  kinds  of  leather  as  require  no  grain  (for 
instance,  the  leather  used  in  carding  machines)  after  having  been  pared,  are  moistened 
and  then  rubbed  over  on  both  sides  with  pumice-stone,  being  thus  rendered  smooth. 

Raising  the  Grain  Slightly  with  Pommels  of  Cork. — Leathers  which  require  a  higher 


884  CHEMICAL   TECHNOLOGY.  [SECT.  vin. 

gloss,  such  as  the  coloured  leathers,  are  treated  with  a  pommel  made  of  cork,  by  which 
they  are  made  to  assume  a  velvety  appearance. 

Smoothing  with  the  Tawers  Softening  Iron. — If  a  still  higher  gloss  is  required, 
the  leather  is  first  smoothed,  or  rather  ironed,  with  iron  or  copper  "  sleekers,"  and 
next  polished  with  glass  sleekers,  a  stout  cylindrical  piece  of  glass,  0-3  metre  in  length 
by  10  centimetres  diameter,  the  leather  being  placed  on  a  tanner's  wooden-leg. 

Rolling. — Leather  intended  for  saddles,  in  order  to  impart  to  it  the  appearance 
natural  to  hog's  leather,  is  passed  through  rollers,  the  surfaces  of  which  are  provided 
with  blunt  points,  which,  being  forced  into  the  leather,  give  to  it  the  desired 
appearance. 

Finishing  Off, — In  order  to  remove  from  the  leather  any  creases  and  other  in- 
equalities of  surface,  it  is  damped,  and  then  smoothed  with  a  flattening-iron,  or,  if  the 
skins  are  thin,  with  a  piece  of  horn  provided  with  blunt  teeth. 

Greasing. — When  the  upper  leather  is  required  to  be  very  supple  and  soft,  it  is 
greased ;  that  is  to  say,  it  is  rubbed  with  a  mixture  of  fish-oil  and  tallow,  or  better, 
with  the  peculiarly  modified  fish-oil  which  has  been  used  in  "  chamoising,"  having  been 
recovered  by  the  aid  of  a  solution  of  potash  from  the  chamois  leather  skins.  The  hides 
to  be  greased  are  first  moistened,  and  having  been  rubbed  with  the  greasy  matter,  are 
dried  in  heated  rooms,  so  that  the  hides,  by  actually  combining  with  the  fatty 
matters,  become,  as  it  were,  tanned  and  tawed  at  the  same  time.  The  greasing  is  there- 
fore not  simply  an  operation  of  dressing,  but  in  reality  a  second  tanning  (technically 
tawing)  process. 

The  black  colour  usually  seen  on  the  surface  of  leather  required  for  saddlery  and 
boot-making  is  imparted  to  the  hides  by  rubbing  them  with  a  fresh  solution  of  oak 
bark  and  then  sponging  them  over  with  a  solution  of  copperas  to  which  some  blue 
vitriol  has  been  added ;  the  hides  are  then  again  dressed,  and  lastly  rubbed  with  a 
paste  made  of  fish-oil,  tallow,  lamp-black,  yellow  wax,  soap,  and  copperas,  the  object  of 
this  operation  being  to  protect  the  leather  from  the  injurious  effects  of  the  shoe- 
blacking,  which  usually  contains  sulphuric  acid.*  Finally,  the  leather  is  painted  or 
brushed  over  with  a  mixed  tallow  and  glue  solution,  and  then,  having  been  polished 
again  with  glass,  is  ready  for  sale.  In  order  to  keep  leather  supple  and  soft,  it  is  besfc 
to  rub  it  with  a  mixture  of  fish-oil  and  lard. 

Yufts,  Jufts,  or  Jufti,  Russia  Leather. — Under  the  name  of  yufts  is  understood  a 
peculiar  kind  of  leather,  usually  of  a  red  or  black  colour,  which  is  very  water-tight  and 
strong.  This  kind  of  leather  was  formerly  made  exclusively  in  Russia,  whence  it  was 
obtained  in  large  quantity,  the  name  being  derived  from  the  Russian  Jufti,  signifying  a 
pair,  and  apparently  due  to  the  fact  that,  in  tanning,  the  hides  are  sewed  together  in  pairs. 
The  hides  usually  prepared  for  Russia  leather  are  those  of  young  cattle  ;  sometimes,  how- 
ever, the  hides  of  horses  and  the  skins  of  sheep,  goats,  and  calves  are  employed.  The 
operations  for  preparing  yufts  are: — (i)  The  cleansing  of  the  hides,  performed  in  the 
usual  manner  with  lime.  (2)  The  swelling  of  the  hides  in  an  acid  bath  prepared  with 
malt,  exhausted  tan-liquor,  or  with  kaschka  (excreta  of  dogs  rubbed  up  with  water). 
(3)  The  tanning,  not  performed  with  oak  bark,  but  with  the  barks  of  various  kinds  of- 
willows,  fir  and  birch  bark  being  also  used.  The  dressed  hides  are  first  placed  for 
some  days  in  partly  exhausted  bark,  and  are  then  put  into  the  tanning  tanks  along 
with  bark  (as  above  described),  or  are  sometimes  placed  in  a  warm  infusion  of  the 
tannin -containing  materials.  The  tanning  continues  for  five  or  six  weeks.  (4)  The 
tanned  hides  are  placed  on  the  planing-block  for  the  purpose  of  draining,  and  are  next 
impregnated  with  diggut  or  elachert,  oil  of  birch,  obtained  by  a  process  of  dry  distil- 
lation from  birch  wood .  This  oil  contains  creosote,  phenol  (of  a  peculiar  kind  accord- 
ing to  Louginine),  and  paraffine.  It  is  rubbed  into  the  hides  on  the  flesh  side,  and 

*  For  a  shoe-blacking  without  acid  see  Chemical  News,  vol.  xxir.  p.  120. 


SECT.  vni.J  TANNING.  885 

when  thoroughly  impregnated  they  are  stretched  until  they  become  soft  and  supple. 
The  hides  are  next  rubbed  on  the  hair  side  with  a  solution  of  alum,  and  then  grained 
and  dried.  The  dry  hides  are  dyed  in  pairs,  sewn  together  so  as  to  form  a  sack,  into 
which  a  decoction  of  dye  material  is  poured.  When  a  red  colour  is  desired,  the  dye  is 
prepared  from  sandal-wood  and  Pernambuco-wood  extracted  with  lime-water,  to  which 
some  potash  or  soda  is  added.  In  more  recent  methods  the  hides  are  dyed  by  being 
brushed  over  five  or  six  times  with  the  dye  material.  The  dry  leather  is  finally  dressed 
by  the  mechanical  operations  previously  described.  The  use  of  yufts  for  bookbinding 
and  other  purposes  is  well  known.  Owing  to  the  empyreumatic  oil  with  which  this 
kind  of  leather  is  impregnated  insects  do  not  attack  it. 

Morocco  Leather. — By  morocco  leather  is  understood  a  kind  of  leather  which,  when 
genuine,  is  obtained  from  goat-  or  kid-skins,  and  is  very  soft,  elastic,  highly  coloured, 
and  not  lacquered.  We  distinguish  between  genuine  morocco  and  the  imitation 
obtained  by  the  splitting  of  calf,  sheep,  and  other  skins,  as  chiefly  employed  in  book- 
binding. 

The  preparing  of  morocco  leather  is  undoubtedly  one  of  the  many  industrial 
discoveries  of  the  Saracens ;  even  at  the  present  day  a  great  deal  of  morocco  leather 
is  made  by  their  descendants  in  Northern  Africa  and  the  Levant.  The  preparation 
of  good  morocco  leather  requires  very  great  care,  especially  as  regards  the 
preliminary  operations.  The  skins  are  deprived  of  the  hair  by  the  aid  of  lime  and 
sweating.  The  tanning  material  in  general  use  is  sumac,  the  skins  being  sewn  up  so 
as  to  form  sacks  into  which  water  is  poured  together  with  pulverised  sumac ;  by  this 
mode  of  employing  the  tanning  matter  the  operation  is  finished  in  three  days.  Calf 
and  sheep  skin  are  very  generally  tanned  in  England  by  the  same  method.  The 
dyeing  of  morocco  leather  is  not  performed  in  the  Oriental  countries ;  the  dry  tanned 
skins  are  exported  under  the  name  of  Meschin  leather  (cuir  en  croutes)  to  be  dyed  and 
dressed  in  Europe. 

Dressing  Morocco  Leather. — The  skins  are  dyed  and  next  dressed.  The  dyeing  is 
performed — (a)  by  means  of  the  dye- vat  (for  genuine  morocco),  or  (/3)  with  the 
brush  (for  imitation  morocco),  (a)  The  operation  of  dyeing  with  the  vat  is  performed 
in  a  small  trough  large  enough  to  hold  one  skin,  and  filled  with  dye-li  nior  at  60°  from 
a  larger  tank.  The  workman  pours  in  no  more  of  the  dye  material  than  can  be  con- 
veniently absorbed  by  the  skin,  which  is  continually  moved  to  and  fro.  The  dyed 
skins  are  layed  out  flat,  and  from  two  to  four  dozen  placed  one  upon  the  other.  The 
dyeing  operation  is  repeated  several  (three  to  five)  times,  care  being  taken  to  turn  the 
heap  over  so  that  the  undermost  skin  is  placed  on  the  top  of  the  heap  previous  to 
beginning  the  dyeing  operation  again.  The  dyed  skins  are  washed  in  water  and  next 
dressed.  (£)  The  imitation  morocco  is  dyed  by  the  dye-liquor  being  uniformly  brushed 
over  the  skins ;  these  having  been  first  stretched  on  a  table,  the  dye-liquor  is 
brushed  over  more  than  once  so  as  to  produce  a  uniform  hue.  The  effect  of  the 
dyeing  is  greatly  enhanced  by  the  dressing  of  the  skins  and  the  fine  grain  given  to 
them.  The  dyed  skins  are  first  rubbed  on  the  hair-side  with  linseed  oil  applied  by 
means  of  a  piece  of  flannel.  The  calendering  or  glazing  by  machinery  is  the  next, 
operation,  after  which  the  peculiar  appearance  of  the  surface  is  imparted  by  means  of 
strong  pressure  or  so-called  platting.  Yellow  skins  are  not  glazed,  because  their  colour 
would  thereby  become  a  brown.  The  aniline  colours  are  now  largely  employed  in 
dyeing  skins. 

Cordwain,  Cordovan  Leather. — This  differs  from  morocco  only  by  being  prepared 
from  heavy  skins,  and  by  retaining  its  natural  grain  or  not  being  platted.  It  is  usually 
met  with  dyed  red,  yellow,  or  black. 

Lacquered  Leather. — This  kind  of  leather,  now  largely  used  by  coachbuilders  and 
for  making  shoes,  boots,  helmets  and  other  military  accoutrements,  is  an  invention  of 


886  CHEMICAL  TECHNOLOGY.  [SECT,  vin^ 

the  present  time,  its  great  merit  being  its  property  of  resisting  water,  and  in  being; 
supple  and  soft,  while  the  lacquer,  if  well  laid  on,  should  not  crack  nor  peel  off.  Only 
black  lacquered  leather  is  generally  met  with.  On  the  tanned,  rarely  tawed,  hide,  which 
has  not  been  greased,  is  very  uniformly  laid  a  varnish,  which  is  thick  arid  tough  while 
cold,  but  thinly  fluid  when  warm ;  this  having  been  done,  the  hide  is  placed  in  a  brick- 
built  stove  kept  at  50°,  where  the  varnish  dries  after  having  become  so  fluid  as  to- 
run  uniformly  over  the  surface  of  the  leather,  which  is  placed  quite  horizontally.  The 
coloured  lacquers  are  generally  more  thinly  fluid  and  are  dried  at  a  lower  temperature. 
The  hides  chiefly  used  for  lacquering  are  cow-hides ;  or  a  thin  hide  is  obtained  by 
splitting  thick  hides  and  lacquering  them. 

The  leather  in  use  by  pianoforte-makers  for  covering  the  hammers  is  prepared  by  a 
process  usually  kept  a  trade  secret.  This  kind  of  leather  requires  to  be  soft  and  very 
elastic.  All  that  is  known  about  the  process  of  preparing  this  material  is  that  ifc  is 
obtained  by  tanning  and  tawing  (chamoising)  combined  ;  the  hair  having  been  removed,, 
but  not  the  epidermis,  the  hide  is  first  fulled  in  oil,  then  washed  in  lye,  bleached  in  the 
sun,  and  next  tanned  in  a  tepid  oak  bark  infusion.  Danish  leather  is  prepared  by 
tanning  sheep-,  goat-,  kid-,  and  lamb-skins  with  willow  bark ;  such  leather  being 
chiefly  used  for  gloves.  It  is  distinguished  by  its  strength,  suppleness,  and  bright 
colour. 

Alum  Tanning — Taiving.  —  Alum-tanning  makes  use  especially  of  aluminous 
salts  for  converting  hides  into  a  white  or  light-coloured  leather.  It  has  three  varieties  : 

(1)  Ordinary  tawing,  in  which  thin  hides,  such  as  those  of  sheep  and  goats,  are 

worked  lip  with  a  mixture  of  alum  and  common  salt  without  the  use  of  oil. 

(2)  Hungarian  tawing,  in  which  the  hides  of  oxen,  buffaloes,  horses,  &c.,  are  worked 

up  without  a  previous  treatment  with  lime  and  then  saturated  with  oil.  Closely 
connected  with  this  process  is  the  preparation  of  Klemm's  fat-leather. 

(3)  French  or  Erlangen  tawing,  for  obtaining  glove-leather  from  the  skins  of  kids, 

young  calves,  lambs,  rarely  of  chamois. 

(4)  Preparation  of  leather  with  insoluble  soaps  and  its  tanning  with  compounds  of 

iron  or  of  chrome  (Knapp's  Leather). 

(i)  Common  Tawing. — The  tawer  obtains  sheep-skin,  or  occasionally  goat-skin, 
either  with  the  wool  off  or  "  in  the  wool,"  as  the  term  runs,  in  the  latter  case  greater 
care  being  required,  because  the  value  of  the  wool,  which,  by  careful  working  may  be 
obtained  in  good  condition,  refunds  a  considerable  portion  of  the  expense  of  the 
operation  by  its  sale.  The  various  operations  of  tawing  are  in  a  certain  measure 
similar  to  those  of  tanning. 

The  steeping  and  planing  is  carried  on  as  in  the  tanning  process.  The  workman 
places  ten  skins  on  the  planing-tree,  and  dresses  each  skin  with  the  dressing-knife  on 
the  hair  as  well  as  on  the  flesh  side;  next,  the  wool  or  hair  is  shaved  off  after  the 
skins  have  been  first  treated  with  the  lime;  but  when  "in  the  wool "  the  skins  are 
cleansed  with  thin  lime-water,  which  is  laid  on  the  flesh  side  of  the  skin  by  a  brush 
made  of  cow's  hair,  so  that  the  wool  is  not  brought  into  contact  with  lime.  The  wool 
is  removed,  not  by  a  planing-iron,  but  by  means  of  a  piece  of  wood  somewhat  sharpened. 
The  wool  having  been  removed,  the  skins  are  brushed  over  with  a  mixture  of  equal 
parts  of  lime  and  sifted  ashes ;  next  the  head  and  leg  strips  of  the  skin  are  turned 
inside.  Each  skin  is  then  folded  together  and  beaten,  in  order  to  prevent  the  wool 
being  touched  by  the  lime.  The  skins  are  left  in  this  condition  for  eight  to  ten  days 
until  the  wool  is  loosened.  The  skins  are  next  thoroughly  washed  on  the  flesh  side  as 
well  as  on  the  wool  side  in  order  to  remove  the  lime  and  dirt ;  tliis  having  been  done 
the  wool  is  partly  pulled  off  by  the  hands,  partly  removed  by  a  blunt  tool.  The  skins 
thus  deprived  of  wool  are  placed  in  the  lime-pit  and  further  treated  as  just  described. 
In  order  to  remove  the  paste  adhering  to  the  skins  they  are,  on  being  removed,  placed. 


SECT,  viii.]  TANNING.  '  887 

in  a  tank,  where,  owing  to  the  quantity  of  animal  matter  dissolved  in  the  water,  a 
fermentation  has  arisen  accompanied  by  an  evolution  of  ammonia.  By  the  action  of 
this  alkali  a  large  portion  of  the  fatty  matter  contained  in  the  skins  is  removed.  After 
being  taken  from  the  lime-pit  the  skins  are  placed  on  the  dresser's  block,  and  some 
parts,  such  as  the  ears,  skin  of  tail,  portion  of  top  part  of  chest,  are  cut  off  and  thrown 
aside  for  the  glue-boiler.  The  skins  are  put  over-night  to  soak  in  water,  and  then 
again  placed  on  the  dressing-block  in  order  to  be  planed  with  a  blunt  iron  on  both  sides 
of  the  skin ;  this  operation  is  repeated  after  the  skins  have  been  placed  in  a  tank 
containing  water,  and  while  there  thoroughly  beaten  with  a  heavy  wooden  "  possing- 
stick  "  in  order  to  remove  lime.  In  the  subsequent  planing  the  lime  and  lime-soap  are 
forced  out,  and  any  wool  that  has  remained  shaved  off.  In  order  to  dissolve  the  last 
traces  of  lime  the  skins  are  placed  in  an  acid-tank  containing  bran  and  water,  in  which 
by  fermentation  lactic  and  acetic  acid  have  been  formed.  These  acids  convert  the 
lime  of  the  skins  into  soluble  salts,  while  the  process  causes  the  swelling  of  the  skins, 
which  thus  become  better  adapted  to  absorb  the  tanning  material.  The  skins  remain 
in  the  sour-tank  for  two  to  three  days.  The  tanning  material  consists  for  i  dicker 
(10  skins),  of  an  alum  lye,  containing  0^75  kilo,  of  alum,  and  0*30  kilo,  of  common  salt 
dissolved  in  22*5  litres  of  boiling  water,  i  litre  of  this  liquid  is  poured  into  a  trough, 
and  having  become  tepid,  each  skin  is  separately  thoroughly  washed  with  and  soaked 
in  it,  and  then  put  aside  without  being  wrung  out,  the  skins  being  placed  one  upon  the 
other  so  as  to  form  a  heap.  After  lying  thus  for  two  or  three  days,  the  skins  are 
wrung  out  and  hung  up  to  dry  slowly  by  exposure  to  air. 

As  regards  the  theory  of  the  action  of  the  alum  lye  in  the^tawing  operation,  it  was 
formerly  believed  that  only  the  aluminium  chloride — formed  by  double  decomposition 
between  the  constituents  of  the  common  salt  and  the  aluminium  sulphate  of  the  alum 
(the  alkaline  sulphates  being  considered  useless) — was  active,  and  that  a  basic  alu- 
minium chloride  (aluminium  oxychloride)  combined  with  the  skin,  there  being  left  in 
solution  aluminium  chloride.  It  was  also  known  that  aluminium  acetate,  if  used 
instead  of  alum  lye,  was  quite  as  active  and  yielded  excellent  results.  The  experiments 
made  by  Dr.  Knapp,  sen.,  with  alum,  aluminium  acetate,  and  aluminium  chloride 
have  proved  that  110  decomposition  ensues  when  the  aluminium  salt  is  taken  up  by  the 
skin,  the  quantity  taken  up  being  for  the  undermentioned  salts  as  follows : — 

Of  alum 8'Spercont. 

Of  aluminium  sulphate        .        .        .        .        .        •27^9        „ 

Of  aluminium  chloride 27'3        > 

Of  aluminium  acetate         .        .        •        •        •        •     23'3        » 

The  aluminium  salts  do  not,  however,  combine  with  skin  under  all  conditions  in  the 
same  quantity  as  just  mentioned,  as  experience  proves  that  the  skins  absorb  more  when 
placed  in  concentrated  than  when  in  dilute  solutions.  As  regards  the  part  played  by 
the  common  salt  in  the  preparation  of  the  alum  lye,  the  salt  is  not  there  simply  to  bring 
about  the  conversion  of  the  aluminium  sulphate  into  aluminium  chloride  (recent 
experiments  made  by  Knapp  in  1866  have  proved  that  by  employing  i  mol.  of  potash 
alum  and  3  mols.  of  common  salt,  =  37  per  cent.,  no  mutual  decomposition  ensues),  but 
the  salt  is  in  this  process  active  by  itself,  partly  aiding  dialytically  the  action  of  the 
alum,  partly  owing  to  its  property— possessed  also  by  alcohol— of  withdrawing  from 
animal  tissues  the  water  they  contain  sufficiently  to  prevent  the  fibres  from  becoming 
glued  together  by  the  drying  of  the  substance,  thus  promoting  the  formation  of  leather. 
The  dry  and  tawed  skins  will  be  found  to  have  become  shrunken  and  stiff,  having  lost 
much  of  their  suppleness  and  flexibility.  In  order  to  remedy  these  defects  the  skins 
previously  damped  with  water  are  submitted  to  a  mechanical  operation,  being  placed 
on  the  convex  side  of  a  curved  iron,  and  stretched  by  being  drawn  between  this  fixed 
iron  and  a  movable  steel  plate,  which  is  fitted  closely  upon  the  other.  After  having 


888  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

been  thus  softened,  the  skins  are  stretched  on  a  frame  for  some  time  to  become  dry. 
When  dry  they  are  ready  for  sale,  the  leather  thus  obtained  being  largely  used  under 
the  name  of  white  skins  for  the  lining  of  boots  and  shoes. 

(2)  Hungarian   Tawing  Process. — This  process   is  distinguished    from    that   just 
described,  inasmuch  as  the  heavy  hides  of  oxen,  buffaloes,  cows,  horses,  &c.,  are  made 
into  leather  for  saddlery  and  other  purposes,  while  sometimes  also  the  skins  of  wild 
boars  and  of  other  animals  are  thus  tawed  for  making  flail  strings.     The  raw  hides  are 
first  soaked  in  water  to  remove  blood  and  impurities.     Next  the  hair  is  shaved  off  by 
means  of  a  sharp  knife.     This  operation  performed,  the  hides  are  put  into  an  alum 
lye,  which  for  a  hide  weighing  25  kilos.,  consists  of  3  kilos,  of  alum,  3  of  common  salt, 
and  20  litres  of  hot  water.     This  liquor  when  tepid  is  poured  into  an  elliptical  tub  in 
which  the  hide  is  placed. 

One  of  the  workmen  then  jumps  into  the  tub  and  by  moving  the  hide  about  with 
his  feet  soaks  it  thoroughly  with  the  liquor,  in  which  it  is  then  left  for  at  least  eight 
days,  the  operation  of  treading  with  the  feet  being  repeated.  The  hide  is  now  taken 
from  the  tub  and  hung  up  to  dry,  and  when  dry  is  stretched  and  "  fatted  "  in  by  the 
following  method : — The  hide  is  warmed  by  being  held  over  a  charcoal  fire,  and  when 
warm  is  rubbed  on  the  hair  as  well  as  on  the  flesh  side  with  molten  tallow,  of  which 
some  3  kilos,  are  used  for  every  hide.  "When  thirty  hides  have  been  thus  treated, 
they  are  one  by  one  again  held  and  moved  to  and  fro  over  the  fire,  and  next  hung 
up  in  the  open  air  to  dry.  The  tallow  partly  combines  with  the  hide. 

The  hides  thus  prepared  are  converted  into  a  leather  of  excellent  quality,  especially 
suited  for  the  harness  of  horses  and  saddlery  work  of  a  more  common  kind,  in  which, 
as  in  that  used  for  artillery  horses,  great  strength  is  required.  This  leather  is  cheap 
on  account  of  its  being  prepared  in  a  short  time. 

(3)  Glove  Leather. — The  so-called  Erlanger,  or  French  tawing  process,  is  employed 
only  for  the  production  of  the  glace,  or  kid  leather,  used  for  making  gloves  and  ball- 
room shoes.     The  hair  side  of  the  skins  intended  to  be  converted  into  this  leather  is 
left  unchanged,  while  as  regards  wash-leather  gloves  which  are  treated  (tanned)  with 
fish-oil  the  hair  side  is  cut  off.     The  skins  intended  to  be  converted  into  kid  leather 
are  treated  with  extraordinary  care,  and  thus  acquire  in  a  very  high  degree  all  the 
good  quality  of  alum-tanned  (or  rather  tawed)  leather.      As  these  skins  are  often 
intended  to  remain  white  or  are  dyed  with  delicate  colours,  the  greatest  care  is  taken 
to  prevent  any  injury,  as,  for  instance,  contact  with  oak  wood  or  with  iron  while  wet. 

Two  kinds  of  skins  are  employed  for  conversion  into  the  better  varieties  of  kid 
leather  ;  one  of  these,  the  moie  expensive,  being  the  skins  of  young  goats,  fed  solely 
with  milk,  the  other  being  lambskin.  Each  of  these  skins  yields  on  an  average  two 
pairs  of  gloves.  The  leather  of  which  ladies'  ball-room  shoes  are  made  is  obtained 
from  the  hides  of  young  calves  (so-called  calf  kid).  The  preliminary  operations  of 
preparing  this  leather  are  exactly  similar  to  those  already  described  for  the  ordinary 
white  leather  ;  but  the  tawing  operations  are  quite  different,  the  skins  being  put  into 
a  peculiar  mixture,  by  which  they  are  not  only  tawed,  but  simultaneously  impregnated 
with  a  sufficient  quantity  of  oil  to  render  them  soft  and  give  suppleness.  The  mixture 
consists  of  a  paste  composed  of  wheaten  flour,  yolks  of  eggs,  alum,  common  salt,  and 
water.  The  flour,  by  the  gluten  it  contains,  aids  the  absorption  of  the  alumina  com- 
pound, and  thus  assists  the  real  tawing.  The  starch  does  not  enter  into  the  composition 
of  the  skins,  while  the  yolk  of  eggs  acts  by  the  oil  it  naturally  contains  in  the  state  of 
emulsion,  this  oil  giving  to  the  kid  leather  that  suppleness  and  softness  which  is  so 
much  esteemed  in  gloves.  It  appears  that  emulsions  made  with  almond  oil  (the  so- 
called  sweet  oil  of  almonds — a  fixed  oil),  olive  oil,  fish  oil,  and  even  paraffine  may  be 
advantageously  substituted  for  yolk  of  eggs.  The  skins  are  thoroughly  soaked  and 
kneaded  in  this  mixture,  to  which,  in  France,  there  is  sometimes  added  from  2  to  3  per 


SECT,  vni.]  TANNING.  889 

cent,  of  carbolic  acid  for  the  purpose  of  preventing  the  too  strong  heating  of  the 
skins  when  impregnated  with  the  mixture  and  packed  in  heaps.  The  skins  are 
next  stretched  by  hand  and  dried  as  rapidly  as  possible  by  exposure  to  air.  Having 
been  damped,  a  dozen  of  the  skins  are  placed  between  linen  cloths  and  trodden  upon  to 
render  them  soft.  After  this  they  are,  one  by  one,  planed,  dried,  and  again  planed. 
Either  by  rubbing  with  a  heavy  polished  glass  disc  or  by  the  appreteur,  simultaneously 
with  the  application  of  some  white  of  egg,  or  a  solution  of  gum,  or  of  fine  soap,  a 
gloss  is  given  to  the  skins,  the  hair  side  of  which  is  the  right  side  or  dyed  side.  The 
dyes  are  applied  either  by  immersion  or  by  brushing  over  the  leather;  the  latter,  or 
English  method  of  dyeing  skins,  is  more  ordinarily  practised. 

According  to  Knapp's  researches  very  good  white  kid  leather  is  obtained  by  tawing 
the  epidermis  (bloss)  from  lamb-  or  goat-skins  in  a  saturated  solution  of  stearic  acid  in 
alcohol.  The  leather  thus  obtained  is  very  soft,  has  a  whiter  colour  than  ordinary 
glace  leather,  and  a  beautiful  gloss. 

(4)  Knapp's  Leather. — The  preparation  of  leather  with  the  aid  of  insoluble  soaps, 
introduced  by  Knapp,  would  appear  to  have  become  of  some  importance.  The  pro- 
perty possessed  by  oxide  of  iron  of  acting  as  a  tanning  material  has  been  known  for 
along  time,  and  in  1855  Mr.  Belford  took  out  a  patent  in  this  country  for  a  mineral 
tan  method,  in  which  oxide  of  iron  was  used  ;  but  good  leather  did  not  result.  The 
hides  do  not  become  really  tanned  by  being  immersed  in  solutions  of  such  metallic 
salts  as  those  of  the  ferrous  and  ferric  oxides,  and  zinc  and  chromium  oxides ;  for 
though  the  acidity  of  these  solutions  is  reduced  to  a  minimum  without  producing 
a  permanent  precipitate,  and  thereby  the  deleterious  action  of  the  acid  upon  the  fibres 
of  the  hides  decreased,  and  though  a  certain  combination  of  the  oxide  and  fibres  takes 
place,  no  real  leather  is  formed  because  the  substance  when  finished  is  not  fitted  for 
contact  with  water,  for  then  the  so-called  tanning  is  washed  out.  Knapp's  process  also 
is  not  really  a  tanning  but  a  tawing  operation,  by  which  the  skins  are  alternately 
immersed  in  a  solution  containing  from  3  to  5  per  cent,  of  soft  soap,  and  then  in  a  saline 
solution  of  oxide  of  iron,  or  of  chromium,  containing  5  per  cent,  of  the  salt,  from  which 
an  insoluble  metallic  soap  is  precipitated  and  impregnated  with  the  fibres.  After  this 
operation  has  been  several  times  repeated  the  hides  or  skins  are  washed  in  water  and 
dried.  Although  the  exterior  colour  of  good  sound  leather  may  be  imitated,  the  real 
qualities  of  leather  are  wanting.  Knapp's  process  is  not  in  use  or  is  so  entirely 
modified  by  substituting  alum  for  metallic  oxides  that  the  skins  are  tawed  by  a 
combination  of  the  preceding  tawing  processes  and  the  oil-tawing  process  now  to  be 
described. 

Iron-tanning  is  hitherto  without  practical  importance  and  Heinzerling's  chrome 
tanning  is,  in  the  opinion  of  the  author,  perfectly  worthless. 

Electrical  Tanning.— The  novel  process  of  electrical  tanning,  patented  by  MM. Worms 
and  Bale,  and  worked  in  this  country  by  the  British  Tanning  Company,  Limited,  makes 
use  of  ordinary  tan-liquors,  but  the  tannin  is  made  to  act  upon  the  hides  by  means  of  an 
electrical  current.  At  a  demonstration  of  the  process  which  took  place  in  May,  1 890, 
at  Eothsay  Street,  Bermondsey,  the  visitors  were  first  shown  a  drum  containing  tan 
liquor  of  the  required  strength,  into  which  a  pack  of  Australian  salted  hides,  unhaired 
and  cleaned  in  the  ordinary  way,  were  put.  The  drums  employed  are  1 1  feet  6  inches 
in  diameter  by  8  feet  wide,  and  contain  an  electrode  running  round  the  interior  of  one 
end  or  head,  from  which  the  current  passes  through  the  liquor  to  a  similar  conductor 
in  the  other  head. 

The  drum  was  set  in  motion,  and  a  current  of  10  amperes  passed  through  the 
Hquor.  The  action  of  the  current  which  is  applied  is  partly  to  promote  diffusion  and 
partly  to  electrolyse  the  liquor,  both  these  effects,  aided  by  the  rotation  of  the  drum,  are 
no  doubt  the  explanation  of  the  remarkable  saving  of  time  effected  by  this  process,  it 


890  CHEMICAL   TECHNOLOGY.  [SECT.  vin. 

being  possible  thus  to  tan  skins  and  hides  in  from  24  to  144  hours,  against  from  four  to 
fifteen  months  by  the  old  process  of  steeping  in  pits.  A  drum  was  opened  which  had 
been  running  for  a  little  over  five  days,  sections  of  the  hides  (salted  Australian)  were 
cut  and  examined  by  tanners  present,  and  found  to  be  thoroughly  tanned.  The  visitors- 
then  inspected  the  drying  sheds  and  shops  above,  where  leather  was  seen  in  all  stages, 
rolled  for  sole  leather,  curried,  &c.,also  some  hides  prepared  for  machine  belting,  of  which, 
according  to  some  tests  shown  us  by  Mr.  Conrad  Falkenstein,  manager  at  Rothsav 
Street,  the  tensile  strength  before  breaking,  taking  the  average  from  a  number  of 
samples,  was  equivalent  to  4305  Ibs.  per  square  inch  for  the  electrically  tanned  leather,, 
against  3570  to  3800  for  leather  tanned  by  the  ordinary  process.  The  leather  is  now- 
being  sold  in  the  market,  and  is  steadily  taking  its  place  in  every  branch  of  the  trade. 

Oil-Tawing  and  Wash-leather  Process, — By  this  name  is  understood  a  peculiar 
process  by  which  the  skins  and  hides  of  various  animals,  such  as  harts,  deer,  sheep, 
calves,  oxen  (for  the  white  leather  for  military  use  as  belts,  &c.),  are  converted  into  so- 
called  oil-  or  wash-leather.  The  tanning  material  is  oil,  fat,  tallow,  or  fish  oil,  to 
which  there  has  been  recently  added  from  4  to  7  per  cent,  of  carbolic  acid.  The  leather 
thus  obtained  is  chiefly  used  for  making  military  breeches,  socks,  vests,  gloves,  braces, 
belts,  and  surgical  appliances,  a  not  inconsiderable  quantity  being  also  used,  owing  to  its- 
softness,  for  washing  glass  and  porcelain.  On  this  account  wash-leather  is  also  largely 
used  by  gold-  and  silversmiths  for  polishing  trinkets  with  rouge  (very  carefully  pre- 
pared oxide  of  iron).  The  upper  or  exterior  layer  of  the  corium,  which  owing  to  its 
greater  compactness  does  not  possess  the  ductility  and  suppleness  of  the  lower  or 
interior  layer,  is  in  the  skins  intended  to  be  converted  into  wash-leather  entirely  cut 
away,  so  that  no  hair  and  flesh  side  are  taken  into  consideration.  The  cutting  away 
of  this  layer  greatly  promotes  the  absorption  of  the  oil,  which  by  the  joint  action  of 
air  and  heat  yields  a  product  which  is  a  dry  compound  of  fibre  and  oil,  in  which  the 
latter  physically  has  disappeared,  inasmuch  as  the  leather  is  not  impervious  to  water. 
Wash-leather  differs  in  this  respect  from  oil  or  fat  leather ;  still,  on  immersion  in, 
water,  the  skin  does  not  glue  together  and  shrink.  Thin  skins,  such  as  those  of 
goats  and  lambs,  are  not  deprived  of  their  hair  side,  because  it  would  render  them  too 
thin  for  use. 

The  skins  intended  to  be  made  into  wash-leather  are,  as  regards  the  first  stage  of 
the  operation,  treated  exactly  as  described  for  the  skins  treated  with  alum,  the  only 
difference  being  that  the  hair  is  removed  together  with  the  hair  side  portion  of  the 
skins,  which  are  next  placed  in  a  bran  bath  in  order  to  remove  the  lime.  After  this 
the  skins  are  stretched  and  conveyed  to  the  fulling  machine  in  order  to  become 
saturated  with  oil,  for  which  purpose  the  skins  are  first  laid  on  a  table  or  bench  and 
are  rubbed  with  oil,  the  hair  side  being  placed  uppermost.  This  having  been  done 
they  are  made  into  clouts  and  placed  under  the  stampers  of  a  machine  so  as  to 
thoroughly  impregnate  them  with  oil.  From  time  to  time  the  skins  are  taken  from 
the  trough  and  exposed  to  the  air,  then  again  rubbed  with  oil  and  put  under  the 
stampers  until  enough  oil  has  been  absorbed.  By  the  repeated  exposure  to  air  the 
skins  become  dry,  and  oil  (fish  oil  is  chiefly  used)  absorbed ;  the  exposure  to  air 
is  continued  until  the  surface  of  the  skins  appears  quite  dry.  When  the  skins  have 
an  odour  somewhat  similar  to  that  of  horse-radish,  and  have  lost  their  fleshy  odour,, 
they  have  absorbed  a  sufficient  quantity  of  oil,  while  a  portion  of  the  oil  has  been 
somewhat  changed  and  has  entered  into  combination  with  the  fibre,  another  portion 
only  mechanically  adhering  to  the  pores  of  the  skins.  The  next  operation  therefore 
aims  at  rendering  the  process  of  the  combination  of  the  oil  with  the  skins  more  rapid 
by  bringing  about  a  fermentation  attended  with  an  elevation  of  temperature ;  this  is 
effected  by  placing  the  skins  in  a  warm  room,  heaping  them  together,  and  covering 
them  with  canvas  to  keep  in  the  heat  which  is  generated,  care  being  taken  to  air  the 


SECT,  viii.]  TANNING.  S9i 

heap  from  time  to  time  in  order  to  prevent  overheating  and  consequent  deterioration 
of  the  skins.  This  operation  of  airing  the  skins  is  repeated  until  by  the  spontaneous 
heating  they  have  acquired  a  yellow  colour  and  the  workmen  know  by  experience  that 
the  oxidation  of  the  oil  is  finished.  A  portion  of  the  oil  (estimated  at  about  50  per 
cent,  of  the  quantity  originally  employed)  is  left  in  the  skins  in  uncombined  state,  and 
is  removed  by  washing  with  a  tepid  solution  of  potash.  From  this  liquor  there 
separates  on  being  left  at  rest  a  portion  of  fat  termed  degras,  and  which,  as  already 
mentioned,  is  employed  for  the  dressing  of  tanned  hides.  The  skins  having  been  thus 
deprived  of  the  excess  of  oil  are  wrung  out,  dried,  and  next  dressed,  in  order  to  restore 
to  them  their  softness  and  suppleness  partly  lost  in  the  drying.  Cordovan  or  Turkey 
leather,  is  oil-tawed  without  the  hair  side  having  been  first  removed,  while  the  flesh 
side  is  blackened  in  the  usual  way.  This  kind  of  leather  is  chiefly  used  for  ladies' 
boots  and  shoes.  According  to  Knapp,  skins  from  which  the  hair  has  been  first 
removed  may  be  tawed  by  treating  them  alternately  with  a  solution  of  soap  and  dilute 
acids,  so  that  the  fatty  acids  are  precipitated  into  the  fibre.  After  the  tawing  the 
skins  thus  treated  should  be  thoroughly  washed  in  water  to  remove  all  acid.  As 
regards  the  constitution  of  the  leather,  commonly  known  as  wash-leather,  tawed  with 
oil,  nothing  is  definitely  known,  but  it  would  appear  that  this  process  of  tawing  has 
some  analogy  to  the  process  of  imparting  oil  to  calico  intended  for  Turkey-red  dying. 

Parchment. — The  substance  known  as  parchment  is  not  really  leather,  because  its 
fibres  are  neither  tanned  nor  tawed,  as  proved  by  the  fact  that  boiling  water  readily 
converts  parchment  into  a  superior  kind  of  glue  similar  to  isinglass,  of  course  too 
expensive  for  joiners'  use.  Parchment  is  essentially  the  well-cleansed  and  carefully 
dried  skins  of  hares,  rabbits,  and  especially  of  calves  and  sheep. 

Ordinary  parchment  is  prepared  from  sheepskins,  but  the  variety  known  as 
vellum,  Velin  or  Parchemin  vierge,  is  far  finer,  and  is  made  from  the  skins  of  young 
calves,  goats,  and  stillborn  lambs.  According  to  the  use  intended  to  be  made  of 
parchment,  so  is  its  preparation  modified.  The  skins  are  first  soaked  in  water  and 
then  placed  in  the  lime-pits.  Sheepskins  are  cleansed  by  working  with  cream  of  lime 
in  order  to  preserve  the  wool.  When  the  hair  has  been  removed  the  skins  are  washed, 
being  placed  on  the  dresser's  block,  and  usually  also  planed  with  a  sharp  knife  to 
remove  the  superfluous  fleshy  parts.  This  having  been  done,  each  skin  is  separately 
stretched  in  a  frame,  in  a  manner  very  similar  to  that  in  use  for  so-called  Berlin-wool 
work,  the  skins  being  held  in  position  by  means  of  strings,  and  dried  by  exposure  in 
the  open  air.  Parchment  intended  for  drum  skins  (from  calves'  skins),  for  kettle- 
drums (from  asses'  skins),  does  not  require  any  further  operation.  If  intended  for 
bookbinding  the  parchment  is  treated  as  described,  but  after  drying  it  is  planed  with 
a  tool  the  cutting  edge  of  which  is  somewhat  bent  in  order  to  impart  a  rough  surface, 
whereby  the  parchment  is  rendered  capable  of  being  written  on  and  dyed.  If 
the  parchment  be  intended — as  it  was  frequently  before  the  invention  of  metallic 
paper — for  memoranda  written  with  lead  pencils,  to  be  wiped  out  if  desired  with  a 
wet  sponge,  it  is  after  planing  painted  over  with  a  thin  white  lead  paint,  for  which 
a  mixture  of  glue  water  with  baryta  or  zinc  white  is  often  substituted.  The  vellum 
of  this  country  is  generally  obtained  from  sheepskins,  which  are  split  into  two 
sheets  by  means  of  cutting-tools.  Parchment,  after  having  been  dried  on  the  frames, 
is  dusted  over  with  chalk  and  rubbed  with  pumice-stone.  The  sieves  used  in  powder 
mills  for  granulating  the  powder  are  made  of  parchment  obtained  from  hogs'  skins. 

Shagreen. — Genuine  Oriental  shagreen  (saghir,  sagri,  sagre)  is  a  variety  of  tawed 
parchment,  one  side  of  Avhich  is  covered  with  small  hard  grains.  This  material  is 
manufactured  in  Persia,  at  Astrakan,  in  Turkey,  and  in  Roumania,  from  certain  por- 
tions of  the  skins  and  hides  of  wild  asses,  horses,  and  other  animals.  The  hides  are 
soaked  in  water  until  the  epidermis  can  be  removed  easily  together  with  the  hairs  by 


892  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

the  aid  of  a  dressing-knife  ;  next,  the  hides  are  again  placed  in  water  so  as  to  swell  the 
material  sufficiently  to  admit  of  cleansing  it,  and  cutting  away  on  both  flesh  and  hair 
side  all  superfluous  material,  so  as  to  leave  only  the  corium,  which  then  has  the 
appearance  of  a  fresh  bladder.  In  order  to  produce  on  skins  thus  prepared  a  grained 
surface,  they  are  put  into  frames,  as  described  under  Parchment,  while  on  the  hair 
side,  allabuta,  the  hard  black  seed  of  the  Chenopodium  album  is  stamped  in,  either  by 
the  feet  or  forced  in  by  pressure.  When  the  skins  are  dry  they  are  removed  from  the 
frame,  the  seed  shaken  off,  and  the  skins  thoroughly  planed  with  a  sharp  dressing- 
knife,  then  put  again  into  water,  tawed,  and  finally  dyed.  The  tawing  is  effected  by 
the  aid  either  of  alum  or  of  oak  bark.  The  dye  of  shagreen  is  generally  green,  and  is 
due  to  salts  of  copper.  After  dyeing  the  skins  are  soaked  in  mutton  tallow. 

Fish  skin,  or  fish  shagreen,  is  obtained  from  various  kinds  of  sharks  (Squalus 
canicula,  /S.  catulus,  S.  centrina)  and  other  fishes  of  the  same  class.  The  skin  of  these 
animals  is  not  covered  with  scales,  but  with  more  or  less  projecting  hard  points.  The 
skins  having  been  removed  from  the  fish  are  stretched  in  frames  and  simply  dried, 
being  then  sent  to  the  market.  Formerly  sharks'  skin  was  in  some  countries  used  by 
joiners  instead  of  sand-  and  glass-paper  for  preparing  wood.  The  skins  deprived  of 
the  projections  are  dyed  and  used  for  covering  small  boxes,  tubes  of  small  tele- 
scopes, &c.* 

GLUE,  SIZE,  GELATINE. 

General  Observations. — The  organisms  of  all  animals,  but  more  especially  of  the 
higher  classes,  contain  tissues  which  are  insoluble  in  cold  as  well  as  in  hot  water,  but 
which  by  continued  boiling  become  dissolved,  and  yield  on  evaporation  of  the  solution 
a  glutinous  gelatinising  mass,  which,  by  further  drying,  exhibits,  according  to  the 
degree  of  purity  of  the  material,  a  more  or  less  transparent  and  brittle  substance, 
which  in  its  pure  state  is  devoid  of  colour  as  well  as  of  smell,  becoming  swollen  in  cold 
water  and  dissolved  by  boiling  in  that  liquid.  This  substance — i.e.,  the  product  of  the 
conversion  of  the  so-called  glue-  or  gelatine-yielding  tissues,  is  what  is  known  in  the 
trade  as  glue,  and  is  largely  used  by  carpenters,  joiners,  &c.,  for  joining  wood.  It  is 
also  largely  used  for  sizing  paper,  for  clarifying  various  liquids — beer  and  wine,  for 
instance — and  as  a  cement.  Among  the  glue-yielding  tissues  the  following  are  the 
most  important : — Cellular  tissue,  the  corium,  tendons  or  sinews,  the  middle  mem- 
brane of  the  vasa  lymphatica  and  veins,  the  osseine  or  organic  matter  of  bones, 
hartshorn,  cartilage,  the  air  bladders  of  many  kinds  of  fish,  &c.  Chemically,  we 
distinguish  between  glutin,  that  is  to  say,  glue  derived  from  skins,  bones,  <fcc.,  and 
chondrin,  which  has  been  obtained  from  cartilage.  From  a  technical  point  of  view 
this  distinction  is  hardly  required,  as  the  cartilaginous  matter  is  as  much  as  possible 
eliminated  from  other  glue-making  materials,  because  experience  has  shown  that  glutin 
has  a  much  greater  power  of  adhesion  than  chondrin.  The  latter,  however,  is  largely 
used  as  size  in  this  country. 

As  already  observed,  the  glue  or  gelatine-yielding  tissues  yield  on  being  dissolved 
a  gelatinising  mass,  the  aqueous  solution  of  which  does  not,  however,  possess  to  any 
great  extent  a  glueing  property,  which  is  only  imparted  to  the  gelatine  by  a  process  of 
drying.  In  considering,  therefore,  the  process  of  glue-boiling,  we  have  to  distinguish 
the  animal  matter  capable  of  yielding  glue,  the  gelatinous  mass  obtained  therefrom, 
and  the  glue  obtained  by  drying  the  latter.  The  temperature  required  for  producing 
gelatine  differs  according  to  the  different  animal  tissues  employed  ;  the  consistency  of 
the  gelatine  obtained  from  equally  strong  solutions  varies  with  the  age  of  the  tissues 
operated  upon. 

*  The  reader  may  further  consult  Leather  Manufacture,  by  A.  Watt  (London  :  Crosby  Look- 
wood  &  Co.) ;    Text-Book  of  Tanning,  by  H.  K.  Procter  (London  :  C.  &  F.  N.  Spon). 


SECT,  viii.]  GLUE,   SIZE,   GELATINE.  893 

Glue  readily  dissolves  by  boiling  in  water,  forming  on  cooling  a  gelatinous  mass, 
even  if  the  quantity  of  glue  is  only  i  per  cent.  Repeated  boiling  and  cooling  a 
glue  solution  causes  it  to  lose  the  quality  of  gelatinising,  and  the  same  effect  is  produced 
by  acetic  and  dilute  nitric  acids.  Solutions  of  alum  precipitate  glue  solutions  only  after 
the  addition  of  potash  or  soda,  the  precipitate  consisting  of  glue  mixed  with  basic 
aluminium  sulphate.  Glue  enters  with  tannic  acid  into  a  combination  of  constant 
composition ;  hence  glue  or  gelatine  may  be  used  for  the  estimation  of  tannin  in 
vegetable  matter. 

Three  different  kinds  of  glue  are  distinguished  by  the  manufacturers,  viz. : 

(a)  So-called   skin-glue,    or   leather-glue,    prepared    from    refuse   hides,   skins 

tendons,  <fec. 

(6)  The  glue  obtained  from  bones. 
(c)  The  glue  obtained  from  fish-bladders,  termed  isinglass. 

Very  recently  glue  from  vegetable  gluten  and  so-called  albumen  glue  have  been 
prepared. 

Leather  Glue. — This  substance  is  prepared  from  a  large  variety  of  animal  refuse,  the 
chief  sources  being  the  following  : — Refuse  from  tanyards,  tawing  and  leather- dressing 
works,  old  gloves,  rabbit  and  hare  skins  (the  hair  having  been  used  by  hatmakers), 
skins  of  cats  and  dogs,  ox  feet,  parchment  cuttings,  surons  (skins  which  have  served 
the  purpose  of  carrying  drugs,  especially  from  America),  sinews,  gut,  leather  cuttings 
(leather  tanned  with  oak  bark  cannot  be  readily  converted  into  glue).  The  glue-boiler 
on  an  average  obtains  from  the  various  materials  about  25  per  cent,  of  glue,  preference 
being  given  to  the  refuse  of  tawing  operations  and  kid  leather  making,  because  these 
materials  are  ready  for  boiling  without  requiring  any  previous  treatment.  Glue-boiling 
involves  the  following  operations  : — 

(1)  Treating  the  glue-yielding  materials  with  lime. 

(2)  Boiling  these  materials. 

(3)  Forming  the  gelatine. 

(4)  Drying  the  gelatine  so  as  to  form  glue. 

(i)  Treating  with  Lime. — The  aim  of  this  operation  is  the  cleansing  of  the  refuse  and 
the  prevention  of  putrefaction.  It  is  effected  by  placing  the  cuttings  in  tanks  or  lime- 
pits  and  pouring  in  a  thin  milk  of  lime.  The  materials,  while  the  milk  of  lime  is 
frequently  renewed,  are  thoroughly  mixed  with  the  lime-liquid  and  left  for  fifteen  to 
twenty  days  in  the  pits.  By  the  action  of  the  lime  any  blood  and  flesh  is  dissolved 
and  the  fatty  matter  saponified.  In  order  to  remove  the  excess  of  lime,  the  materials 
are  placed  either  in  nets  or  willow  baskets,  and  these  are  immersed  in  a  brook  or 
river,  where  a  continuous  stream  of  fresh  water  removes  the  greater  part  of  the 
lime  in  a  few  days.  The  washed  material  is  next  exposed  in  the  yard  to  the  action  of 
the  air  in  order  that  it  may  become  dry,  as  well  as  form  a  carbonate  of  any  lime 
still  present  in  the  materials.  When  the  materials  are  dry  they  are  packed  and 
sent  off  to  the  glue-boilers,  who,  previous  to  proceeding  with  the  boiling  operation, 
macerate  the  materials  again  in  a  weak  milk  of  lime,  the  maceration  being  followed  by 
washing. 

Fleck  states  that  a  weak  alkaline  lye  (5  kilos,  of  soda  ash  and  7-5  kilos,  of 
quicklime  to  750  to  1000  kilos,  of  glue-yielding  material)  is  preferable  to  the  use  of 
milk  of  lime.  When  the  glue-boiling  and  tanning  operations  are  executed  on  the 
same  premises,  the  lime-treated  glue  materials  are  put  for  a  few  hours  into  old  oak 
bark  liquor,  the  acids  (lactic,  butyric,  and  propionic  acids)  of  which  remove  the  lime, 
while  the  animal  matter  is  at  the  same  time  superficially  tanned.  This  glue  tannate 
rises  during  the  boiling  as  scum  to  the  surface,  and  assists  in  rendering  the  glue  liquor 
clear.  According  to  Dullo,  the  Cologne  glue — a  very  pale  and  strong  glue — is  obtained 


CHEMICAL  TECHNOLOGY.  [SECT,  vm, 

from  offal,  which,  after  liming,  has  been  treated  with  a  solution  of  chloride  of  lime 
{calcium  hypochlorite),  and  thereby  bleached. 

Boiling  the  Materials. — This  operation  is  carried  on  either  in  the  ordinary  manner 
of  boiling  anything  with  water,  or  by  so-called  fractionated  boiling,  or  finally  by  the 
application  of  steam.  As  the  conversion  of  the  glue-yielding  materials  into  glue 
takes  place  slowly  and  gradually  under  the  influence  of  the  boiling- water,  it  is  clear 
that  the  method  of  boiling  cannot  be  without  influence  upon  the  glue  ultimately 
produced.  The  first  portions  of  gelatine  which  are  formed  remain  in  contact  with  a 
boiling-hot  mass,  and  are  thereby  further  changed  so  as  to  lose  the  capability  of 
gelatinising,  while  the  glue  at  last  obtained  exhibits  a  dark  colour,  and  is  often  not  so 
strong,  although  it  is  generally  believed  that  deep-coloured  glue  is  of  a  better  quality. 
A  rational  mode  of  glue-boiling  would  involve  the  gradual  removal  of  the  solution 
obtained,  while  of  course  fresh  water  would  have  to  be  supplied  to  replace  the  liquor 
drawn  off.  The  older  method  of  glue-boiling  consists  in  simply  placing  the  materials 
with  water  in  a  cauldron,  care  being  taken  to  prevent  burning  by  placing  them 
on  a  stout  wire  gauze  or  tying  them  in  a  net  and  suspending  it  in  the  boiling  liquid. 
Soft  water  yields  a  better  result  than  hard.  Gradually  the  materials  become  dissolved, 
and  the  scum  which  is  formed  is  taken  from  the  surface  with  a  large  ladle.  The 
refuse  of  glue  of  former  operations  is  added  to  the  boiling  liquid,  and  the  operation 
continued  until  the  liquid  is  of  the  required  strength,  which  is  tested  by  pouring  into 
a  broken  egg-shell  a  small  portion  of  the  liquor,  and  by  placing  the  partly -filled  shell 
in  ice-cold  water.  If  the  solution  gelatinises  after  a  while,  forming  a  hard  and  rather 
stiff  gelatine,  the  liquor  is  run  off  by  means  of  a  tap,  filtered  through  a  layer  of  straw 
placed  in  a  basket,  and  conveyed  to  a  wooien  lead-lined  cistern,  externally  covered 
with  mats  or  straw,  or  some  bad  conductor  of  heat.  In  some  works  the  liquor  is 
decanted  into  a  deep  but  narrow  boiler,  the  furnace  of  which  is  so  arranged  as  to 
impart  heat  to  the  top  of  the  vessel  only.  This  vessel,  as  well  as  the  cistern,  is  heated 
previously  to  the  liquor  being  poured  in.  The  liquor  is  clarified  by  stirring  into  it  a 
small  quantity  of  very  finely-pulverised  alum,  0*07  to  0*15  per  cent.,  into  the  liquid. 
After  this  the  liquid  is  left  to  stand  all  night.  The  alum  precipitates  any  lime 
remaining  as  calcium  sulphate,  and  also  some  organic  matter  which  renders  the  liquid 
turbid.  Alum,  though  it  prevents  the  putrefaction  of  the  glue  while  drying,  impairs 
its  strength.  The  lime  might  better  be  precipitated  by  oxalic  acid,  and  the  organic 
matter  removed  by  adding  to  the  boiling  mass  some  astringent  matter,  such  as  oak 
bark  decoction  or  hops,  so  that  during  the  boiling  the  organic  impurities  could  be  taken 
away  as  scum. 

Fractionated  Boiling. — By  this  operation  only  a  comparatively  small  quantity  of 
water  is  added  to  the  animal  matter  intended  to  be  converted  into  glue.  When  the 
water  is  fairly  boiling  the  cauldron  is  covered  with  a  well-fitting  lid,  and  the  steam 
being  kept  in  as  much  as  possible,  is  allowed  to  act  upon  the  materials  so  as  to  convert 
them  into  glue.  When,  after  continued  boiling  for  about  two  hours,  the  water  has 
taken  up  sufficient  gelatine,  the  liquor  is  run  off  and  fresh  water  poured  on  the 
materials.  This  operation  is  repeated  until  the  decoction  no  longer  gelatinises,  the 
last  liquor  being  kept  instead  of  water  for  use  for  a  following  operation.  The  liquors 
tjius  obtained,  excepting  the  last,  are  either  mixed  or  each  is  treated  separately.  The 
glue  yielded  by  the  first  decoction  is  stronger  than  that  yielded  by  the  subsequent 
liquors.  By  this  method  of  boiling  the  saturated  liquor  does  not  remain  exposed  to 
the  action  of  heat  and  water  too  long,  and  consequently  a  better  article  is  produced. 
In  some  instances  the  materials  intended  to  be  converted  into  glue  are  boiled  in  a 
vessel  similar  in  construction  to  those  in  use  in  bleaching-works  and  in  paper-mills, 
arranged  in  the  folio-wing  manner.  At  some  distance  from  the  bottom  a  perforated 
false  bottom  is  placed,  in  the  centre  of  which  is  fixed  a  wide  tube  which  reaches  to 


SECT,  vin.]  GLUE,   SIZE,  GELATINE.  895 

about  two-thirds  of  the  height  of  the  cauldron.  The  materials  intended  to  be  converted 
into  glue  are  placed  upon  the  perforated  bottom,  and  water  under  it ;  as  soon  as  the 
water  boils,  the  steam  produced,  not  being  able  to  escape  rapidly  and  readily  through 
the  materials,  exerts  a  pressure  upon  the  liquid,  and  forces  it  through  the  tube,  the 
consequence  being  a  constant  stream  of  boiling  liquid  falls  upon  the  glue  materials, 
which  are  rapidly  dissolved. 

A  more  rational  mode  of  conducting  this  operation  consists  in  employing  high- 
pressure  steam,  admitted  into  the  mass  of  the  animal  materials  to  be  converted  into 
.glue.  In  this  manner  a  very  concentrated  solution  of  glue  is  obtained  in  a  short 
time.  In  England  steam  is  generally  employed,  but  on  the  Continent  its  use  is  the 
•exception.  It  has  been  said  that  it  is  advantageous  to  allow  the  animal  offal  intended 
for  glue  to  become  somewhat  decomposed,  and  then  to  disinfect  it  with  chlorine  or 
sulphurous  acid  before  boiling  it  for  glue,  because  by  this  mode  of  treatment  a  brighter 
glue  is  obtained.  We  are  unable  to  say  whether  this  opinion  is  correct. 

Moulding. — As  soon  as  the  glue  solution  has,  by  standing  in  the  tanks  into  which 
it  had  been  transferred  from  the  boilers,  become  quite  clear  and  somewhat  cooled,  the 
liquid  is  poured  into  moulds,  and  when  solidified  the  jelly  is  cut  into  cakes  of  the 
shape  and  size  met  with  in  the  trade. 

The  moulds,  into  which  the  glue  solution  is  poured  through  a  strainer  made  of 
rnotal  gauze,  are  of  wood,  and  generally  a  little  wider  at  the  top  than  at  the  bottom, 
so  as  to  admit  of  an  easy  removal  of  the  solid  material.  At  the  bottom  of  the  moulds 
a  series  of  grooves  are  cut  at  such  a  distance  from  each  other  as  agrees  with  the  size 
of  the  intended  glue-cakes.  Before  the  liquid  is  poured  into  the  moulds,  these  are 
thoroughly  washed,  and  either  allowed  to  remain  damp,  or  if  dried,  are  oiled,  so  as  to 
prevent  the  solidifying  gelatine  adhering  to  the  wood.  Recently  moulds  made  of 
sheet-iron  and  zinc  have  been  introduced.  The  moulds  are  filled  with  the  lukewarm 
glue  solution,  and  when  the  glue  is  sufficiently  hard  it  is  gently  loosened  from  the 
sides  with  a  sharp  tool,  and  the  mould  having  been  turned  over  on  a  wooden  or  stone 
table,  previously  damped,  is  lifted  off  the  block  of  gelatine,  which  is  next  cut  into 
cakes  or  slabs.  The  cutting-tool  is  simply  a  piano-wire,  or  more  frequently  a  series 
of  these  stretched  in  a  frame  at  sufficient  distance  from  each  other  to  make  the  cakes 
of  the  desired  thickness,  the  frame  being  placed  on  small  wheels  so  as  to  be  easily 
moved.  Glue  is  met  with  in  the  trade  as  a  gelatinous  mass,  or  is  sold  in  casks  under 
the  name  of  size.  It  is  said  that  the  process  of  drying  impairs  the  good  qualities  of 
the  glue. 

Drying  the  Glue. — This  operation  is  performed  by  placing  the  gelatine  cakes  on 
nets  made  of  twine  stretched  in  frames,  and  exposed  in  a  dry  airy  place  to  the  action 
of  the  sun.  The  drying  is  one  of  the  most  difficult  operations  of  the  glue-making 
process,  because  the  temperature  of  the  air  and  its  hygrometric  condition  exert  a 
great  influence  on  the  product,  especially  during  the  first  few  days.*  The  glue  will  not 
bear  a  temperature  above  20°,  because  at  a  higher  temperature  it  becomes  again  fluid, 
and  as  a  matter  of  course  flows  through  the  meshes  of  the  net  and  adheres  to  the 
twine  so  strongly  as  to  require  the  nets  to  be  put  into  hot  water  for  the  removal  of 
the  mass.  Air  too  dry  causes  an  irregularity  in  the  drying  of  the  glue,  and  as  a 
consequence  the  cakes  become  bent  and  cracked  ;  while  frost  causes  disintegration,  so 
as  to  necessitate  a  re-melting  of  the  glue :  hence  it  follows  that  drying  in  the  open  air 
can  only  be  effected  in  the  spring  and  autumn.  Although  the  glue^boilers  have  tried 
to  dry  glue  by  artificial  heat,  this  plan  has  not  been  generally  introduced  owing  to  the 
fact  that  a  slight  excess  of  heat  causes  the  melting  of  the  gelatine,  the  more  readily 
when  ventilation  is  neglected.  Drying-rooms,  as  recently  constructed,  are  large-sized 

*  It  is  very  generally  considered  that  the  occurrence  of  a  thunderstorm  during  the  process 
-of  drying  renders  it  necessary  to  remelt  the  product.— [EoiTOE.] 


896  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

sheds  fitted  with  the  required  frame-work  for  receiving  the  gelatine  cakes,  and  heated 
by  steam-pipes  placed  on  the  floor  near  the  latter.  The  walls  are  provided  with 
openings  which  can  be  closed  by  means  of  valves,  while  there  are  ventilators  in  the 
roof  arranged  to  obtain  a  proper  circulation  of  air.  As  the  gelatine  placed  nearest  to 
the  floor  of  the  room  becomes  most  quickly  dry,  it  is,  with  the  frames  upon  which  it 
placed,  removed  after  eighteen  to  twenty-four  hours  to  a  higher  part  of  the  drying- 
room,  which  is  not  heated  at  all  if  the  outer  air  has  a  temperature  of  from  15°  to  20°. 
The  drying-shed,  or  room,  is  by  preference  built  so  as  to  face  the  north.  When  the  glue 
has  been  thus  dried  as  much  as  possible,  it  is  generally  quickly  dried  in  a  stove  in  order 
to  impart  hardness.  It  is  next  polished  by  being  immersed  in  hot  water,  and  cleaned 
with  a  brush,  and  again  dried. 

Bone-Glue. — The  organic  matter  contained  in  bones,  forming  nearly  one-third  part 
(32-17  per  cent.)  of  their  weight,  consists  of  a  material  which,  after  the  bones  have 
been  treated  with  hydrochloric  acid,  is  very  readily  converted  into  glue  by  the  action 
of  high-pressure  steam.  The  preparation  of  glue  from  bones  by  the  action  of  hydro- 
chloric acid  is  the  usual  mode  of  proceeding,  and  the  operation  is  advantageously 
combined  with  the  making  of  sal  ammoniac  and  phosphorus. 

The  preparation  of  glue  from  bones  includes  the  following  operations  : — 

(1)  Boiling  out  the  Grease. — The  bones  are  put  into  water  and  boiled  in  a  cauldron, 
the  fat  floating  to  the  surface.     Frequently,  in  order  to  save  fuel,  the  bones  are  put  into 
an  iron  wire  basket,  which  is  removed  after  the  boiling  has  been  continued  for  some 
time,  the  bones  thrown  out  and  fresh  ones  put  in,  the  boiling  being  continued  until  a 
thick  gelatinous  liquor  is  obtained.     The  fat  or  grease  is  removed  from  the  surface 
of  the  liquid  by  means  of  ladles.     The  gelatinous  mass  obtained  by  this  process  is 
either  used  as  a  manure  or  is  given  to  cattle  as  fodder  !     In  some  works  bones  have 
been  exhausted  with  carbon  disulphicle  for  the  purpose  of  extracting  the  grease. 

(2)  Treating  the  Bones  with  Hydrochloric  Acid. — The  bones,  having  been  drained, 
are  placed  in  baskets,  and  in  these  are  immersed  in  tanks  to  more  than  half  their  height, 
the  tanks  being  filled  with  hydrochloric  acid  at  9'6°  Tw.  (=1-05  sp.  gr.  =  10-6  per  cent. 
C1H) :  10  kilos,  of  bones  require  40  litres  of  acid.     The  bones  are  kept  in  this  liquor 
until  they  become  quite  soft  and  transparent.     They  are  next  drained,  and  then,  with 
the  baskets,  immersed  in  a  stream  or  brook  with  a  good  supply  of  running  water  to 
wash  out  the  greater  portion  of  the  acid,*  which  is  fully  neutralised  by  placing  the 
bones  in  lime-water,  again  followed  by  washing  with  fresh  water,  the  bones  being  then 
ready  for  boiling.    Gerland  has  suggested  the  use  of  sulphurous  instead  of  hydrochloric 
acid. 

(3)  Conversion  of  the  Organic  Matter  into  Glue. — The  cartilaginous  substance  having 
been  either  partly  or  completely  dried  is  put  into  a  cylindrical  vessel  containing  a  false 
perforated  bottom,  and  between  that  and  the  real  bottom  a  pipe  or  tube.     To  the  top 
of  the  vessel  a  lid  is  fitted,  provided  with  an  opening  for  a  steam-pipe  leading  from  a 
small  boiler.     Shortly  after  the  admission  of  the  steam  a  concentrated  glue  solution 
begins  to  run  off  from  the  pipe  at  the  bottom  of  the  cylinder ;  this  solution  is  usually 
so  concentrated  as  to  admit  of  being  at  once  run  into  the  moulds,  and,  after  having 
become  solid,  is  treated  as  before  described.     After  a  few  hcurs  a  weak  liquid  makes 
its  appearance,  and  as  soon  as  this  happens  the  cylindrical  vessel  is  opened,  the  glue 
mass  removed  with  the  weak  liquid  to  a  copper  and  boiled,  care  being  taken  to  stir  the 
magma  constantly.     As  soon  as  the  glue  is  dissolved  the  liquor  is  poured  into  moulds. 
Glue  obtained  from  bones  exhibits  a  milky  appearance,  due  to  the  presence  of  a  small 
quantity  of  calcium  phosphate  retained  in  the  substance.    Sometimes  there  is  purposely 

*  This  method  of  washing   pollutes  the   streams,  and  is   no  longer  permissible  where   due 
sanitary  inspection  is  enforced. — [EDITOR  ] 


SECT,  viii.]  GLUE,   SIZE,   GELATINE.  897 

added  more  or  less  baryta-white,  zinc-white,  white-lead,  chalk,  or  pipe-clay.  The  glue 
obtained  from  bones  is  sold  under  the  name  of  patent  glue. 

Liquid  Glue. — When  glue  is  dissolved  in  its  own  weight  of  water  and  a  small 
quantity  of  nitric  acid  added  to  the  solution,  it  loses  the  property  of  gelatinising,  while 
the  adhesive  property  of  the  glue  is  not  impaired.  Dumoulin  prefers  to  dissolve 
i  kilo,  of  Cologne  glue  in  i  litre  of  boiling  water,  and  to  add  to  the  solutiou  o'2  kilo, 
of  nitric  acid  at  62°  Tw.  =  1-31  sp.  gr.  After  the  evolution  of  the  nitrous  acid  fumes 
has  subsided  the  fluid  is  cooled.  A  better  liquid  glue  is  obtained  by  dissolving  good 
gelatine  or  glue  of  superior  quality  in  strong  vinegar  or  moderately  strong  acetic 
acid,  to  which  some  pulverised  alum  and  one-fourth  of  its  bulk  of  alcohol  are  added, 
the  solution  being  aided  by  a  water-bath.  The  action  of  the  acetic  acid  is  the  same  as 
that  of  the  nitric  acid.  According  to  Knaffl,  a  very  excellent  liquid  glue  is  obtained 
by  heating  for  some  10  to  12  hours  upon  a  water-bath,  a  mixture  of  3  parts  of  glue 
in  8  parts  of  water,  to  which  are  added  0*5  part  of  hydrochloric  acid,  and  0-75  parb 
of  zinc  sulphate,  the  temperature  of  the  mixture  being  kept  below  85°.  This  kind 
of  liquid  glue  keeps  for  a  very  long  time  and  is  largely  used  for  joining  wood,  horn,  and 
mother-of-pearl.  This  glue  is  employed  by  the  makers  of  artificial  pearls. 

Tests  of  Quality  of  Glue. — Although  the  quality  of  glue  is  best  ascertained  by 
practical  use,  some  of  the  physical  qualities  and  the  external  appearance  of  glue  may 
be  mentioned  as  indicating  a  superior  article.  Glue  of  good  quality  should  exhibit  a 
bright  brown  or  brown -yellow  colour,  should  be  free  from  specks,  glossy,  perfectly 
clear,  brittle,  and  hard,  should  not  become  damp  by  exposure  to  air ;  when  being  bent 
it  should  snap  or  break  sharply,  the  fracture  presenting  a  glassy,  shining  appearance. 
When  placed  in  cold  water  glue  should  not  even  after  remaining  forty-eight  hours  in  this 
fluid  swell  up  and  increase  in  bulk  nor  dissolve.  A  splintery  fracture  of  glue  indicates 
that  it  has  not  been  well  boiled.  The  adhesive  property  of  glue  is  often  increased  by 
adding  certain  pulverulent  earthy  substances.  This  addition  is  regularly  the  case  with 
Russian  glue.  Among  the  substances  employed  are  white  lead,  lead  sulphate,  zinc 
white,  baryta  white,  and  even  lead  chromate.  As  different  kinds  of  glue  may  agree 
in  their  external  aspect  and  yet  vary  as  regards  their  adhesive  power,  methods  of 
testing  glue  have  been  proposed,  some  of  which  are  based  upon  the  chemical,  others 
upon  the  physical,  properties  of  this  substance. 

Chemical  tests  are  less  decisive  than  mechanical  trials.  Lipowitz  dissolves  5  parts 
of  the  glue  in  so  much  hot  water  that  the  weight  of  the  solution  makes  up  50  parts 
and  allows  the  solution  to  stand  for  twelve  hours  at  a  temperature  of  18°,  in  order  to 
gelatinise.  On  the  top  of  an  open  glass  of  uniform  width,  he  lays  a  slip  of  tin  plate, 
through  the  middle  of  which  passes  a  perpendicular  wire,  a  cup-shaped  piece  of  tin  with 
its  convex  side  outwards  being  soldered  to  its  lower  end.  The  wire  with  the  cup 
weighs  5  grammes  and  moves  freely  in  the  tin  plate.  To  the  top  of  the  perpendi- 
cular wire  is  fixed  a  funnel  which  also  weighs  5  grammes  and  into  which  there  may  be 
poured  fine  shot  up  to  the  weight  of  50  grammes.  According  to  the  greater  aptitude 
of  the  glue  to  form  a  solid  jelly  the  apparatus  must  be  the  more  heavily  weighted  in 
order  to  sink  into  the  jelly,  whence  the  tenacity  of  the  glue  may  be  approximately 
calculated. 

Karmarsch  simply  glues  two  pieces  of  wood  together  and  determines  the  weight  re- 
quired to  break  them  asunder.  Weidenbusch  saturates  rods  of  plaster  of  Paris  with 
glue  and  breaks  them.  Bauschinger  glues  two  pieces  of  red  beech-wood  together  in 
such  a  manner  that  their  fibres  run  parallel  and  that  each  projects  one  centimetre 
beyond  the  other,  the  glued  surface  being  10x10=100  square  centimetres.  When 
thoroughly  dry  these  pieces  are  fixed  in  Werder's  testing  machine  in  such  a  manner  that 
its  steel  cheeks  catch  in  the  retreating  angles  formed  by  the  projecting  parts  of  the 
pieces  of  wood,  just  at  the  beginning  of  the  glued  joint.  On  seeking  to  move  these 

3  L 


898  CHEMICAL  TECHNOLOGY.  [SECT.  vin.. 

angles  towards  each  other  by  a  measured  and  gradually  increasing  force,  the  glued 
surfaces  of  the  pieces  of  wood  were  at  last  pushed  over  each  other  and  in  this  manner  the 
resistance  to  a  lateral  pressure  was  measured  in  kilos,  and  square  centigrammes. 

Horn  determined  the  resistance  of  common  glue  to  a  tearing  force  as  9-6  kilos.,  that 
of  Cologne  glue  as  io-6,  and  that  of  gelatine  as  31-5  kilos. 

Kissling  found  in  glue  12-3  to  18  per  cent,  of  water,  1-4  to  5-1  per  cent,  of  ash,, 
o  to  o'S  per  cent,  of  a  volatile  acid,  and  o  to  40  per  cent,  of  matter  insoluble  in  water.. 

SIZES. 

Coarse  glues  are  used  in  finishing,  and  to  some  extent  in  dyeing,  textile  goods,  in 
order  to  increase  their  body,  stiffness  and  gloss.  The  kinds  occurring  in  commerce  are 
bone-size  and  glue-size. 

The  best  bone- size  is  made  from  the  "  sloughs  "  of  the  horns  of  oxen.  Of  these- 
4  cwts.  are  boiled  for  ten  hours.  The  liquid  is  strained,  and  then  are  added,  with' 
vigorous  stirring,  alum  3  Ibs.,  and  zinc  sulphate  2  Ibs.,  both  in  fine  powder.  The 
solution  is  received  in  shallow  tubs  and  allowed  to  cool.  The  yield  from  the  above- 
proportions  is  10  cwt.  It  keeps  for  eighteen  months. 

It  is  pale,  clear,  and  semi-transparent.  Its  adhesive  power  is  less  than  that  of 
the  glue  size  made  from  the  clippings  of  hides. 

Glue  size  is  a  dark  brown,  stiff  semi-solid  mass  of  great  tenacity.  It  is  frequently 
contaminated  with  the  exuviae  of  the  larvae  of  blow-flies,  which  adhere  to  the  goods  and 
render  them  unsightly.  Hence  glue  size  should  be  preferably  made  in  winter,  and  be 
kept  in  cold,  dark,  but  draughty  places. 

Isinglass,  fish  Glue. — The  substance  met  in  commerce  under  the  name  of 
Isinglass  is,  if  genuine,  the  dried  interior  pulpy  vesicular  membrane  of  the  air- 
bladder  of  certain  kinds  of  fish  belonging  to  the  order  of  the  cartilaginous  ganoids, 
and  more  especially  of  the  common  sturgeon  (Accipenser  sturio) ;  the  huso,  or  grand 
sturgeon  (.4.  huso);  the  A.  Giildenstaedti  and  A.  stellatus.  The  bladders  of  these  and 
of  kindred  species  of  fish,  plentifully  met  with  in  the  Caspian  Sea  and  the  estuaries  of 
the  rivers  running  into  it,  are  cut  open,  cleansed,  stretched,  and  dried  by  exposure  to 
sunlight,  and  when  sufficiently  dry  to  admit  of  being  handled  without  fear  of  tearing 
the  outer  muscular  membrane,  which  does  not  yield  any  glue  on  being  boiled,  is  torn 
off,  while  the  interior  membrane  is  moulded  in  various  ways  (as  in  rings,  lyre-shaped, 
or  folded  as  leaves  of  paper),  and  bleached  by  sulphurous  acid,  then  thoroughly  dried, 
by  exposure  to  sunlight. 

According  to  the  countries  from  which  it  is  sent  into  the  trade,  isinglass  is 
distinguished — as  Russian  (the  best  kind  being  obtained  from  Astrakan);  North 
America  (from  (Jadus  melucius) ;  East  Indian  (from  Polynemus  plebejus),  met  with 
in  leaves,  also  in  small  sacks,  and  in  the  entire  bladder ;  Hudson's  Bay  isinglass 
(derived  from  sturgeons) ;  Brazilian  is  probably  obtained  from  various  kinds  of 
Silurus  and  Pimeladus.  This  isinglass  is  met  with  in  commerce  in  hollow  tubes,  in 
lumps,  and  in  discs.  German  isinglass  is  prepared  at  Hamburg  from  the  air-bladder 
of  the  common  sturgeon.  In  Roumania  and  Servia  the  skin  and  intestines  (not  the 
liver)  of  cartilaginous  fishes  are  boiled  into  a  stiff  jelly,  which,  having  been  cut  into- 
thin  slices,  is  di'ied  and  sent  into  the  market  as  isinglass.  As  regards  the  use  of 
this  material,  we  have  to  distinguish  between  fish  glue  and  isinglass.  The  former,  if 
properly  prepared,  is  not  at  all  distinguishable  from  ordinary  glue  as  obtained  from 
bones  or  other  animal  refuse ;  but  isinglass  is  not  glue,  and  is  only  converted  into  it 
by  boiling.  It  consists  of  fibres  or  threads,  which  when  placed  in  water  are  somewhat 
dissolved,  but  retain  their  organised  structure ;  this  being  especially  of  importance  for 
the  use  of  this  substance  in  clarifying  wine,  beer,  and  similar  fluids,  as  the  fibres 


SECT,  viii.]  BONES.  899 

constitute  as  it  were  a  close  network,  which  readily  takes  up  the  turbidity  produced  by 
small  particles.  The  presence  of  tannin  in  liquids  which  are  intended  to  be  clarified 
by  the  use  of  isinglass  is  advantageous,  inasmuch  as  it  promotes  the  contraction  of  the 
isinglass  fibres,  whereby  the  suspended  particles  present  in  the  fluid  to  be  clarified  are 
retained;  so  that  in  truth  the  clarifying  by  isinglass  is  a  kind  of  filtration,  which 
cannot  be  performed  either  by  glue  or  by  a  hot  saturated  solution  of  isinglass.  For 
isinglass,  in  all  other  instances,  such  as  the  dressing  of  woven  silk  fabrics,  the  pre- 
paration of  so-called  court-plaster  and  cements,  there  may  be  substituted  good  gelatine. 
Under  the  name  of  Ichthyocollefranqaise,  Rohart  some  years  ago  introduced  a  substitute 
for  isinglass,  a  compound  said  to  be  obtained  from  fibrin  of  blood  and  tannin. 

Substitutes  Jor  Glue. — Recently  three  substitutes  for  glue  have  been  introduced, 
viz. : — (i)  Gluten  glue  (colle  gluten).  (2)  Albumen  glue  (colle  vegetale  ou  albu- 
minoide).  (3)  Casein  glue  (colle  caseine).  The  first  is  a  mixture  of  gluten  and 
fermented  flour.  It  is  a  very  sour  mixture,  endowed  with  but  very  slight  adhe- 
sive power.  Albumen  glue  is  partially  decayed  gluten,  the  substance  largely 
obtained  in  the  manufacture  of  starch  from  wheaten  flour  thoroughly  washed  with 
water,  and  then  exposed  to  a  temperature  of  from  15°  to  20°,  at  which  it  begins 
to  ferment  and  become  partly  fluid,  or  more  correctly  soft,  so  as  to  admit  of 
being  poured  into  moulds,  which  are  placed  in  a  room  heated  to  25°  or  30°  for  from 
twenty-four  to  forty -eight  hours.  The  surface  having  become  dry  enough  to  admit 
of  the  cakes  being  handled,  they  are  taken  from  the  moulds  and  further  dried  by 
being  placed  either  on  canvas  or  on  wire  gauze.  After  four  or  five  days  the  cakes  are 
quite  dry  and  fit  for  being  kept  in  a  dry  place  for  any  length  of  time.  A  solution  of 
this  substance  in  twice  its  weight  of  water  constitutes  a  normal  solution,  which  may 
be  used  for  the  following  purposes  : — Glueing  wood,  cementing  glass,  porcelain, 
earthenware,  mother-of-pearl,  for  pasting  leather,  paper,  and  cardboard ;  it  may  fur- 
ther serve  as  weaver's  glue,  and  as  dressing  for  silk  and  other  woven  fabrics ;  also  for 
a  mordant  instead  of  albumen  in  dyeing  and  printing  various  fabrics  ;  and  lastly,  for 
clarifying  liquids.  Casein  glue  is  prepared  by  dissolving  casein  in  a  strong  solution  of 
borax.  The  thick  fluid  thus  obtained  has  great  adhesive  powers,  and  may  be  advan- 
tageously employed  by  joiners  and  bookbinders.*  "What  is  known  as  elastic  glue  is  a 
preparation  of  glue  and  glycerine,  by  the  addition  of  which  glue  may  be  rendered 
permanently  elastic  and  soft.  It  is  prepared  in  the  following  manner: — Glue  is 
melted  in  water,  by  the  aid  of  a  water-bath,  into  a  very  thick  paste,  to  which 
glycerine  is  added  in  the  same  quantity  by  weight  as  that  of  the  dry  glue.  The 
mixture  is  thoroughly  stirred,  and  then  further  heated,  in  order  to  evaporate  the 
excess  of  water.  The  mass  is  then  cast  on  a  marble  slab,  and  after  cooling,  serves 
for  the  purpose  of  making  printer's  inking  rollers,  elastic  figures,  galvano-plastic 
moulds,  &c. 

BONES. 

The  bones  of  animals  serve  for  obtaining  phosphorus,  as  already  described,  for  bone- 
meal  and  animal  charcoal,  bone-black  or  spodium. 

For  extracting  fat,  the  bones  are  either  boiled  in  water  or  steamed.  A  great  part 
of  the  fat  separates  out,  but  at  the  same  time  a  part  of  the  cartilage  is  dissolved  as 
glue,  so  that  the  mammal  value  of  the  bones  is  reduced.  The  fat  extracted  by 
boiling  is  the  best ;  that  obtained  by  steaming  is  inferior ;  whilst  the  fat  extracted 
by  benzene  has  the  lowest  value,  since  soaps  prepared  from  such  fat  retain  the  mouldy 
smell  of  the  bones. 

*  Skimmed  milk,  as  free  from  fatty  matter  as  possible,  is  coagulated  by  means  of  weak  acetic 
acid.  The  curd  is  well  washed,  pressed  and  dissolved,  either,  as  above  said,  in  a  concentrated 
solution  of  borax,  or  in  sodium  silicate  (so-called  water-glass).  The  liquid  is  very  useful  in  getting 
up  ornamental  articles,  artificial  flowers  &c. — [BDITOB.] 


900 


CHEMICAL  TECHNOLOGY. 


[SECT.  viii. 


Fig.  5  So. 


As  only  from  3  to  4  per  cent,  of  fat  are  obtained  by  boiling,  but  from  5  to  6  by  the 

benzene  process,  and  as  in  this  latter  case  there  is  no  loss  of  glue — i.e.,  of  nitrogen 

the  extraction  by  means  of  benzene  is  coming  more  and  more  into  use. 

According  to  Biittner,  the  recipient,  A  (Fig.  580),  is  filled  with  bones  ;  then  steam  is 
let  into  the  jacket,  Ic,  and  the  pipes,  e,  through  the  cock,  c,  whereby  the  moist  air  formed 

by  heating  the  bones  is  sucked  out  by  the 
steam-blast,  y,  at  o.  The  cock,  q,  is  then 
opened  into  the  pipe,  n,  the  cock,  d,  to  the  pipe 
i,  the  cock,  d,  to  the  pipe,  u,  and  the  residual 
air  from  the  pan,  A,  and  from  the  bones  is 
sucked  by  the  water-blast,  x,  until  the  air  in  A 
is  sufficiently  exhausted,  when  the  cock,  g,  is 
closed  again.  On  opening  the  cock,  g,  the 
benzene  in  the  space,  t,  of  the  receiver,  J3,  rises 
-up  in  the  pipe,  ft  penetrates  into  the  worm,  v 
(perforated  below),  falls  in  the  form  of  rain 
upon  hot,  dry  bones  free  from  air,  and  pene- 
trates into  them  until  they  are  saturated.  The 
rest  of  the  solvent  is  let  through  the  pipe,/,, 
into  the  receiver,  0,  and  is  there  evaporated. 
The  vapours  of  the  solvent  are  now  drawn  by 
the  aid  of  the  water-blast,  x,  from  above  down- 
wards through  the  pan,  A,  the  pipe,  n,  the  cocks, 
q  and  d,  and  the  pipe,  i,  liquefied  on  their  way  from  x  to  the  receiver,  It,  by  the  water 
of  the  water-blast,  and  collected  along  with  the  water  in  the  space,  r,  of  the  receiver, 
B.  The  water  flows  off  chiefly  by  the  pipe,  I,  whilst  the  pure  benzene  flows  to  the 
space,  t,  in  order,  after  the  air-pressure,  to  rise  into  the  worm,  v,  and  the  receiver,  0. 
When  the  extraction  of  the  fat  is  at  an  end,  the  solvent  is  driven  out  by  admitting 
steam  into  k  in  the  manner  described  above,  and  collected  in  the  space,  t,  of  the 
receiver,  B,  in  order  to  be  used  again.  An  expansion  of  air  is  now  produced  in  the 
space,  V,  below  the  bottom,  ^Y,  by  opening  the  cock,  q,  to  the  pipe,  m,  by  means  of 
the  water-blast,  x,  the  fat  on  the  filtering  stratum  of  the  bottom  is  sucked  through,  and 
the  pure  fat  is  let  off  at  b. 

In  order  to  extract  the  glue  from  the  bones,  water  is  let  in  through  the  cock,  a, 
and  the  worm,  v,  and  steamed  till  the  glue  is  dissolved.  The  cock,  q,  is  opened  into  the 
pipe,  m  and  i}  cock,  d,  steam-blast,  x,  and  cock,  d,  opened  to  u,  and  the  steam  is  let  off 
through  u. 

There  thus  arises  a  strong  current  of  vapours  from  above  downwards  through 
the  pan,  A,  which  forcibly  sweeps  the  dissolved  glue  downwards  through  A,  and 
through  the  filtering-bed,  where  it  is  freed  from  dirt  and  particles  of  bone.  When  this 
has  been  repeated  a  few  times,  the  bones  are  freed  from  gelatine,  and  the  concentration 
of  the  glue  and  the  simultaneous  drying  of  the  bones  may  begin  in  the  pan,  A.  For 
this  purpose  the  space,  k,  is  heated  by  steam  under  pressure,  so  that  the  glue  in  V 
begins  to  boil.  Lest  the  temperature  in  A  should  rise  too  high,  the  water-blast,  x, 
and  the  steam-blast,  y,  are  set  in  action,  so  that  these  two  apparatus  draw  away  the 
water  evaporating  from  the  glue  and  the  bones  through  the  cocks,  iv^  and  q,  and  the  pipes, 
n  and  m,  at  o,  the  glue  is  sufficiently  thickened.  Th«J  glue  is  then  run  off,  and  the 
bones  are  heated  and  dried  for  a  short  time  until  the  last  remnant  of  moisture  is 
expelled. 

Bone-black  (Animal  Charcoal). — The  carbonisation  of  the  bones  is  so  conducted  that 
the  volatile  products  are  either  burnt  or  condensed.  In  the  latter  case  the  broken-up 
bones  are  put  into  iron  retorts  similar  to  those  used  for  coal-gas  manufacture,  and  the 


SECT.   VIII.] 


BONES. 


901 


volatne  products  are  collected  in  suitable  condensing  apparatus,  while  the  gas  after  having 
baen  purified,  is  sometimes  led  into  a  gas-holder  and  used  for  illuminating  purposes, 
or  when  not  purified  is  burnt  under  the  retorts.  According,  however,  to  the  experience 
obtained  in  Germany,  bone-black  thus  made  has  a  lower  decolorising  power  than  when 
the  bones  are  ignited  in  iron  pots,  the  volatile  products  being  burnt  at  the  same  time. 
In  Germany,  therefore,  the  older  plan  of  carbonisation  in  pots  is  usually  resorted  to. 
In  England  and  Scotland,  and  also  in  Holland,  Belgium,  and  France,  retorts  are 
generally  used  for  this  purpose.  The  carbonisation  in  pots  is  carried  on  in  the  fol- 
lowing manner :  Cast-iron  pots  are  filled  with  broken-up  bones  placed  one  on  the  top 
of  the  other,  the  edges  of  the  mouths  of  the  pots  being  luted  with  clay.  The  pots  are 
placed  on  the  hearth  of  a  kind  of  reverberatory  furnace.  After  awhile  the  vapours 
which  are  forced  through  the  lute  become  ignited,  thereby  enveloping  the  pots  in  a 
sheet  of  flame,  so  that  the  carbonisation  goes  on  without  requiring  the  firing  of  the 
furnace  to  be  kept  up.  When  the  flame  subsides  the  carbonisation  is  complete.  The 
yield  of  animal  charcoal  amounts  by  this  method  of  procedure  to  55  to  60  per  cent.,  the 
carbonaceous  matter  being,  however,  mixed  with  about  ten  times  its  weight  of  mineral 
matter,  as  may  be  inferred  from  the  following  results  of  analysis  of  a  dried 
sample  of  bone-black,  which  in  100  parts  was  found  to  consist  of:  Carbonaceous 
matter,  10;  calcium  phosphate,  84;  calcium  carbonate,  6  parts.  By  exposure  to  air 
bone-black  absorbs  from  7  to  10  per  cent,  of  moisture.  The  carbonised  bones  are  broken 
up  and  granulated  by  machinery ,  the  formation  of  dust  having  to  be  avoided  as  much  as 
possible  because  it  has  very  little  value. 

Zwillinger  carbonises  bones  with  superheated  steam  in  a  large  iron  receiver,  A 
(Fig.  581),  coated  with  an  insulating 

mass,  and  secures  at  the  same  time  the  Fig.  581. 

bye-products.  Superheated  steam  is 
introduced  at  the  pipe,  b.  The  vapours 
given  off  escape  through  the  refrige- 
rating room,  D,  to  the  iron  washing- 
ivcssels,  E,  and  the  gas-purifier,  F. 

Properties  of  Bone-black. — As  far 
back  as  the  year  1811,  Figuier  dis- 
covered that  bone-black  possesses  the 
property  of  withdrawing  organic  and 
inorganic  substances — viz.,  lime  and 
potash  from  solutions.  It  appears  that 
this  property  is  duo  to  surface  attrac- 
tion (capillary  action),  although  bone- 
black  is  also  capable  of  decomposing 

chemical  compounds.  Owing  to  the  fact  that  bone-black  can  absorb  inorganic  matter, 
ifc  is  largely  used  for  the  purpose  of  withdrawing  lime  and  saline  matter  from  saccharine 
fluids  in  beet-root  sugar  works.  According  to  Anthon,  the  property  of  bone-black  to 
withdraw  lime  from  solutions  is  partly  due  to  the  fact  that  carbonic  acid  is  condensed 
in  the  pores  of  this  substance. 

By  treating  bone-black  with  hydrochloric  acid,  and  thus  dissolving  the  mineral 
matter  it  contains,  the  residue,  after  having  been  well  washed  with  water,  dried,  and 
re-ignited  in  a  closed  crucible,  has  lost  in  a  very  great  measure  its  property  of  with- 
drawing from  solutions  and  retaining  within  its  pores  inorganic  matter.  When  acid 
liquids  are  to  be  decolorised  by  bone-black,  it  should  always  be  employed  after  having 
been  treated  with  hydrochloric  acid.  Shoe-blacking  manufacturers  employ  in  their 
trade  a  large  quantity  of  bone-black. 

Testing  Bone-black. — The  greater  the  decolorising  power  of  charcoal  the  better  its 


902  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

quality,  though  it  appears  that  the  decolorising  power  is  not  proportionate  to  the 
power  of  withdrawing  lime  and  saline  matters  from  solutions.  In  order  to  ascertain 
the  decolorising  power  of  any  sample  of  bone-black,  its  quality  in  this  respect  is  com- 
pared with  that  of  another  of  known  strength.  Payen  proposes  to  take  equal  bulks  of 
water  coloured  with  caramel,  to  treat  these  with  equal  weights  of  animal  charcoal,  and 
to  filter  these  mixtures ;  the  charcoal  which  yields  the  clearest  liquid  being  the  best. 
Bussy  obtained  the  following  results  by  the  estimation  of  the  relative  decolorising 
power  of  equal  quantities  by  weight  of  different  kinds  of  charcoal : — 

Ordinary  bone  black i  'o 

Bone-black  treated  with  hydrochloric  acid    .        .        .        .  i  '6 

„          and  afterwards  ignited  with  potassium  carbonate  20  x> 

Blood  ignited  with  potassium  carbonate        ....  20-0 

„               „           calcium  carbonate 20 'o 

Glue  ignited  with  potassium  carbonate 1 5  *5 

Brimmeyr's  experiments  on  the  decolorising  properties  of  bone-black  led  to  the 
following  results  :  (i)  The  capability  of  absorption  of  this  substance  does  not  depend 
upon  the  mechanical  structure  of  the  bone-black,  but  upon  the  quantity  of  pure  carbon 
it  contains.  (2)  The  quantities  of  matter  absorbed  by  bone-black  of  various  kinds  are 
— when  reduced  to  pure  carbon — really  equivalent,  and  are  probably  independent 
of  the  varying  chemical  nature  of  the  soluble  absorbed  substance.  (3)  Bone-black 
saturated  with  any  substance  retains  its  absorptive  power  for  other  materials  of 
a  different  chemical  nature.  (4)  Bone-black  acts  the  quicker  and  better  the  less  its 
capillary  structure  has  been  interfered  with  either  by  mechanical  or  chemical  means 
(action  of  hydrochloric  acid).  Schultz's  results  of  experiments  agree  with  those 
just  quoted.  The  specifically  lightest  bone-black  which  contains  the  largest  amount  of 
carbon  is  the  most  strongly  decolorising  material.  As  regards  the  sugar  (especially 
beet- root)  manufacture,  the  power  of  bone-black  to  withdraw  lime  from  a  solution 
comes  also  into  consideration ;  this  lime-absorbing  capability  is  estimated  by  directly 
testing  the  quantity  of  lime  which  a  given  sample  of  charcoal  can  take  up. 

Revivification  (Re-burning)  of  Charcoal. — After  having  served  the  purpose  of  deco- 
lorising and  absorbing  lime  for  some  time  in  the  process  of  sugar  refining,  the  bone- 
black  becomes,  as  it  is  termed,  foul  and  requires  to  be  revived,  for  which  purpose  it  is 
either  first  thoroughly  washed  with  hot  water  or  sometimes  left  to  enter  into  a  state 
of  fermentation,  or  treated  with  steam,  and  finally  always  re-ignited.  The  more  usual 
plan  is  to  wash  the  bone-black,  while  still  in  the  filters,  with  hot  water,  so  as  to  remove 
all  soluble  matter,  the  material  being  next  re-ignited.  In  this  manner  bone-black 
may  be  restored  for  use  from  twenty  to  twenty -five  times.  This  mode  of  reviving  labours 
under  the  disadvantage  that  during  the  ignition  the  organic  matter  (absorbed  im- 
purities) is  not  quite  destroyed,  and  by  choking  the  pores  of  the  bone-black  impairs 
its  decolorising  power.  It  is  therefore  preferable  to  cause  the  bone-black  to  ferment, 
to  treat  it  next  with  dilute  hydrochloric  acid,  wash  it  well,  and  lastly  ignite  it.  The 
quantity  of  hydrochloric  acid  employed  for  this  purpose  in  sugar-producing  works  is 
very  large. 

Substitutes  for  Bone-black. — Among  the  substances  which  have  been  tried  as  substi- 
tutes for  the  use  of  bone-black,  carbonised  bituminous  shale  takes  the  first  place.  This 
material  (the  coke  of  the  Boghead  coal  is  an  excellent  example)  absorbs  colouring 
matter,  but  does  not  touch  the  lime.  Moreover  it  often  happens  that  the  coke  is 
rendered  unfit  for  this  use  by  the  presence  of  a  considerable  amount  of  iron  mono- 
sulphide.  The  coke  of  sea-weed  is  perhaps  a  more  suitable  material.* 

*  A  variety  of  artificial  carbons  have  been  prepared  by  charring  mixtures  of  organic  and 
inorganic  matter,  but  none  of  them  have  come  into  general  use. — [EDITOB.] 


:SECT-  vm-]  FATS.  go3 

FATS. 

Fats  are  neutral  substances  of  animal  or  vegetable  origin  which  leave  upon  paper 
transparent  spot  which  does  not  disappear  on  prolonged  exposure  to  the  air.  They 
cannot  be  volatilised  without  decomposition  •  their  specific  gravity  is  less  than  that  of 
water,  in  which  they  are  insoluble,  but  they  dissolve  in  ether,  carbon  disulphide,  or 
benzene.  Almost  all  fats,  in  contradistinction  to  wax,  are  triglycerides— i.e.,  compounds 
of  glycerine,  C3H.(OH)3,  with  fatty  acids.  Berthelot  has,  e.g.,  obtained  factitious 
tripaimitine  from  palmitic  acid  and  glycerine : 

C3H5(OH)3  +  3H.C16H3102  =  C3H5(C1GH3102)3  +  3H.O, 
•and  in  like  manner  trioleine  from  oleic  acid  : 

C3H5(OH)3  +  3H.C18H3302  =  C3H6(C18H3302)3  +  3H20. 
,tmg  the  drying  oils  aside  there  are  two  homologous  series  of  fatty  acids : 
The  first  series  has  the  general  formula  CnH2nO,. 

Formic  acid CH.  O 

Acetic  acid C,H4O2 

Propionic  acid C  H  0 

Butyric  acid C4Hg°I 

Valerianic  acid      .  C  H  O 

....          v/5n,0Uj 

Capronic  acid C.H,./)., 

(Enanthylic  acid C7H  ]o 

Caprylicacid C^A 

Pelargonic  acid 09HI802 

Capricacid C^H^O, 

Laurie  acid C,2H24O2 

Myristicacid OuH'8Ot 

Palmitic  acid C,6HKOZ 

Stearicacid C18H36O2 

Arachicacid C,0H400.2 

Behenic  acid C2,H4402 

Ceroticacid C27HM°t 

Melissic  acid C^H^Og 

'The  second  series  has  the  general  formula  CnH2n-  aO,-. 

Acrylic  acid C3H402 

Crotonic  acid C4HB02 

Angelicic  acid CSH8O2 

Pyroterebic  acid C8H)00, 

Cyminic  acid Cu^aA 

Hypoparic  aoid C16HS002 

Oleicacid C1SH340., 

Doeglic  acid          .        .        .  .      \        .        .        C,,,!!,,  X)2 

Erucic  acid C^H^O.,, 

The  most  important  of  these  acids  are  stearic  acid,  fusible  at  69.2°  under  a  reduced  \ 
,'pressure,  and  volatile  in  superheated  steam  without  decomposition  :  it  is  readily  soluble  / 
in  alcohol  and  ether,  and  insoluble  in  water.     Palmitic  acid  melts  at  62°.     Chevreul's 
margaric  acid  is  a  mixture  of  10  parts  stearic  acid  and  90  parts  palmitic  acid.     Oleic 
acid  is  a  colourless  oily  liquid  which  congeals  at  4°  and  melts  again  at  44°.     Nitrous 
acid  converts  it  into  its  isomere,  elai'dic  acid,  which  melts  at  44°. 

Most  fats  consist  chiefly  of  tripaimitine,  tristearine  and  trioleine.  Tripaimitine, 
generally  called  simply  palmitine,  melts  at  60°  and  congeals  at  46°  ;  it  is  the  chief 
•  constituent  of  palm-oil.  Tristearine  (stearine)  C3H.(C18H3502)3  melts  at  63°,  and  if 
heated  to  65°  it  solidifies  at  61°  and  melts  at  66° ;  if  it  is  superheated  for  a  length  of 
time  its  melting-point  sinks  to  55°.  Trioleine  (oleine),  the  chief  constituent  of  the 
liquid  fats,  solidifies  at  —5°,  and  is  converted  by  nitrous  acid  into  elai'dine  fusible  at 
36°.  If  heated  with  water  under  a  high  pressure  the  triglycerides  are  split  up  into 
glycerine  and  fatty  acid  : 

C3H5(C18H3502)3  +  3H20  =  C3H5(OH)3  +  3H.C18I!350,. 


904  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

The  chief  animal  fats  are,  with  the  exception  of  butter,  suets  (beef  and  mutton)  and 
hog's  lard.  Tallow  is  obtained  by  rendering  (i.e.,  melting  out)  the  fat  which  collects 
in  the  intestinal  cavity  of  oxen  or  sheep.  The  hardness  of  tallow  depends  on  the  species 
of  animal  from  which  it  is  obtained,  and  on  the  food  which  it  has  consumed.  Dry 
fodder  produces  the  hardest  tallow,  while  the  softest  is  obtained  from  animals  fed  on 
the  waste  grain  from  breweries  and  distilleries.  Russian  tallow  is  far  harder  than  the 
German  quality,  since  in  Russia  cattle  subsist  on  dry  fodder  for  more  than  eight  months 
in  the  year.  Tallow  generally  melts  at  35°-37°.  It  contains  75  percent,  hard  fat 
(tristearine  and  tripalmitine),  the  remainder  is  trioleine. 

Goose-grease,  which  is  a  valued  food-fat  in  Germany,  is — or  was — chiefly  burnt  in 
lamps  in  Russia.  In  Britain  it  is  of  little  importance. 

Fish-oil,  seal-oil,  obtained  from  the  blubber  of  several  varieties  of  Mammalia 
inhabiting  the  seas,  especially  of  the  colder  regions  of  the  globe,  and  belonging  'to  the 
Cetacea  and  Phocena,  varies  somewhat  in  its  properties,  according  to  the  mode  of  pre- 
paration and  the  animal  from  which  it  has  been  derived.  The  specific  gravity  of  this 
oil  is  0*927  at  20°;  when  cooled  to  o°  it' deposits  solid  fat;  it  is  readily  soluble  in 
alcohol,  and  consists  of  oleine,  stearine,  and  small  quantities  of  the  glycerides  of 
valerianic  and  similar  fatty  acids.  Fish-oil,  besides  being  an  important  material  in 
soap-making,  is  also  used  in  tanning,  tawing,  and  leather- dressing  operations. 

Vegetable  fats  either  become  rancid  on  exposure  to  the  air,  and  acid  from  the  forma- 
tion of  free  fatty  acid,  though  they  do  not  solidify,  the  non-drying  oils ;  or  they  are 
converted  into  a  solid  mass  by  taking  up  oxygen,  drying  oils. 

The  most  important  non-drying  oils  from  a  technical  point  of  view  are  : — Palm-oil, 
of  vegetable  origin,  met  with  in  the  fruit  of  a  palm-tree,  Avoira  dais  or  Elais  guinensis; 
according  to  others,  however,  this  oil  is  derived  from  the  Cocos  butyracea,  C.  nucifera, 
and  Areca  oleracea,  trees  growing  wild,  and  also  cultivated  in  Guinea  and  Guiana.  The 
colour  of  this  oil  is  a  red-yellow,  its  consistency  that  of  butter,  while  it  possesses  a 
strong  but  by  no  means  disagreeable  odour,  similar  somewhat  to  that  of  orris  root. 
When  fresh,  this  oil  melts  at  27°,  but  by  becoming  rancid  as  it  is  termed — that  is,  by 
its  decomposition  into  glycerine  and  free  fatty  acids — its  melting  point  rises  to  3 1  °  and 
even  to  36°.  It  is  chiefly  composed  of  palmitine  mixed  with  a  small  quantity  of  oleine. 
Palmitine,  formerly  confused  with  margarine,  is  saponified  by  the  alkalies  and  converted 
into  potassium  or  sodium  palmitate,  while  glycerine  is  set  free  : — 

Palmitine  (tripalmitine),    ,^  -/£  ^    [03|       (Glycerine,       3TT5}^3' 

Potassium  hydroxide,  ?KOH  f  =  |  -r,  ,      •         *  ,  (CLH,.0)~ 

/        /.  '  r  Potassium   palmitate,  -•;  i    l6    3l«y  -  0. 

(caustic  potassa)  )       (  '  *\  Kf 

Palmitic  acid  is  very  similar  to,  and  has  often  been  confused  with,  stearic  acid ;  the 
former  is  in  a  pure  state  a  solid  white  crystalline  mass,  which  fuses  at  62°.  Palm-oil 
often  contains  one-third  of  its  weight  of  this  acid  in  free  state,  and  the  quantity- 
increases  with  the  age  of  the  oil.  The  red-yellow  pigment  of  the  palm-oil  not  being 
destroyed  by  its  saponification,  the  soap  made  from  this  oil  is  of  yellow  colour,  but  if,  pre- 
vious to  saponification,  the  oil  is  submitted  to  a  bleaching  process,  that  is  to  say,  the  pig- 
ment destroyed  by  chemical  agents,  such  as  the  joint  action  of  potassium  bichromate  and 
sulphuric  acid,  the  oil  becomes  nearly  white,  and  yields,  on  being  saponified,  a  white  soap. 

Palm-oil  has  latterly  come  into  use  in  the  so-called  white  baths  in  turkey- red 
dyeing — [EDITOR].  Sometimes  a  cask  of  palm-oil  arrives  in  England  without  having 
become  rancid.  Could  this  result  be  regularly  secured  palm-oil  would  doubtless 
supersede  "  margarine." 

The  illipe,  or  bassia-oil,  very  similar  to  palm-oil,  is  obtained  by  pressure  from  the- 
seeds  of  the  Bassia  latifolia,  a  tree  growing  on  the  slopes  of  the  Himalaya.  At  first 
the  colour  of  this  oil  is  yellow,  but  by  exposure  to  sunlight  it  becomes  white.  Its 


SECT,  viii.]  FATS.  9o5 

odour  is  not  very  strong,  but  rather  pleasant.  At  the  ordinary  temperature  of  the  air 
this  oil  has  the  consistency  of  butter  ;  its  sp.  gr.  is  =  0-958  ;  its  melting-point  from  27° 
to  30°.  It  is  somewhat  soluble  in  alcohol,  readily  in  ether,  and  easily  saponified  by 
potassa  and  soda.  In  its  saponification,  oleic  acid  and  two  solid  acids  with  a  variable 
melting-point  are  formed.  The  galam  butter  produced  by  the  Bassia  lutyracea,  a  tree 
met  with  in  the  interior  of  Africa,  is  sometimes  confounded  with  palm-oil,  to  which  it 
is  very  similar,  but  of  a  deeper  red  colour.  Galam  butter  fuses  at  20°  or  21°,  and  is 
in  its  properties  very  much  like  palm-oil.  Carapa  oil  and  vateria  tallow  belong  to  the 
same  class  of  fatty  substances ;  the  first,  the  product  of  the  kernel  of  a  species  of 
Persoonia,  a  palm-tree  met  with  in  Bengal  and  Coromandel,  is  a  bright  yellow-coloured 
material,  which  at  18°  separates  into  an  oil  and  a  solid  fafc,  known  as  pine-tallow, 
Malabar  tallow,  and  obtained  from  the  fruits  of  the  Vateria  indica,  is  a  white-yellow 
wax-like  tallow,  melting  at  35°.  Mafurra  tallow  is  obtained  by  boiling  ia  water  the 
seeds  or  kernels  of  the  mafurra  tree  found  in  Mozambique  ;  this  seed,  very  rarely 
seen  in  Europe,  is  of  the  size  of  small  cacao  beans.  Mafurra  seed  also  occurs  in 
Madagascar  and  Isle  de  Reunion.  The  fat  obtained  from  this  seed  has  a  yellow 
colour,  the  smell  of  cacao  butter,  and  melts  more  readily  than  tallow.  The  fat  of  the 
seeds  of  the  Brindonia  indica,  employed  at  Goa,  instead  of  butter,  also  for  medicinal 
purposes,  and  for  use  in  lamps,  is  nearly  white,  melts  at  40°,  and  is  insoluble  in  cold, 
but  somewhat  soluble  in  boiling  alcohol.  Cocoa-nut  oil,  obtained  from  the  kernels  of 
the  cocoa-nut  (Cocos  nucifera,  C.  butyracea),  is  largely  used  in  the  tropics,  where  the 
tree  abounds.  This  oil  is  imported  into  Europe,  and  is  also  obtained  here  by  pressing 
and  by  treating  the  kernels  of  the  imported  nuts  with  carbon  disulphide.  It  is  white, 
has  the  consistency  of  lard,  but  possesses  a  disagreeable  odour  and  a  somewhat  foliated 
texture ;  its  melting-point  is  22°.  Chemically  considered  this  fat  consists  of  a  peculiar 
substance  termed  cocinin,  with  small  quantities  of  oleine  ;  by  saponification  the  former 
yields  glycerine  and  cocinic  acid  (cocoa-stearic  acid),  C13H2602.  W.  Wicke  obtained  in 
1860,  6 1 '5 7  per  cent  of  fat  from  the  kernels.  During  the  last  twenty  years  cocoa-nut 
oil  has  been  largely  used  for  soap-boiling,  because  it  is  an  excellent  material  for  the 
preparation  of  so-called  filling  soaps.* 

Olive  oil  is  obtained  from  the  fruit  of  the  olive  tree,  Olea  europea,  belonging  to  the 
natural  order  of  the  Jasminece,  and  largely  cultivated  in  the  whole  of  Southern  Europe 
and  the  coastlands  of  North  Africa. 

In  order  to  obtain  an  oil  of  good  quality  it  is  essential  that  the  olives  should  be 
gathered  when  they  are  fully  ripe,  which  happens  in  the  months  of  November  and 
December.  Unripe  olives  yield  an  oil  having  a  harsh  bitter  taste,  while,  again,  over- 
ripe fruit  yields  a  thick  oil,  readily  becoming  rancid.  The  method  of  oil  extraction 
from  olives  as  carried  on  in  Southern  France  is  the  following  : — The  ripe  olives  are  first 
reduced  to  pulp  in  a  mill ;  this  pulp  is  put  into  sacks  made  of  strong  canvas,  or,  better, 
of  horsehair,  and  submitted  to  pressure.  The  first  portion  of  oil  thus  obtained  is  the 
best  and  is  known  as  virgin  oil,  or  huile  merge.  In  order  to  eliminate  all  the  oil  as 
much  as  possible,  the  cake,  after  the  first  pressing,  is  treated  with  boiling  water  and 
again  pressed.  The  oil  thus  obtained  possesses  a  fine  yellow  colour,  but  is  more  liable 
to  become  rancid  than  the  virgin  oil.  Notwithstanding  the  second  pressure  the  cake 
retains  enough  oil  to  make  it  worth  while  to  submit  it  to  further  operation.  Some 
kinds  of  olive  oil  obtained  by  the  second  pressing  are  employed,  under  the  name  of 
Gallipoli  oil,  in  dyeing  Turkey-red.  This  oil  has  an  acid  reaction  consequent  upon  its 
containing  free  fatty  acids,  is  turbid,  rancid,  and  possessed  of  the  property  of  forming 
with  carbonates  of  alkalies  a  kind  of  emulsion,  which  in  dyeing  is  known  as  the  white 

*  Cocoa-nut  oil  has  recently  been  used  for  preparing  an  artificial  butter  which  approaches  cow- 
butter  more  closely  than  any  other  substitute.  The  rancidity  and  offensive  odour  are  removed  by 
treatment  with  alcohol  and  filtration  over  bone-black. — [EoiTOE.] 


.•906  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

bath.  The  olive  oil  used  for  the  purpose  of  greasing  wool  in  spinning  is  known  as 
lampant  oil.  Under  the  name  of  Huile  d'enfer  is  understood  the  olive  oil  deposited  in 
the  tanks  where  the  water  used  for  adding  to  the  olives  about  to  be  pressed  is  kept ; 
it  is  used  in  the  manufacture  of  soap.  During  the  last  few  years  it  has  become  the 
custom  to  exhaust  the  olives  with  carbon  disulphide  instead  of  pressing  them. 

Rape-oil  and  Colza-oil  (formerly  much  used  for  burning  in  lamps)  are  obtained  from 
the  seeds  of  various  kinds  of  Brassica,  which  are,  in  fact,  merely  varieties  of  Brassica 
campestris.  The  oils  differ  very  little. 

Beech  oil,  from  the  seeds  of  the  beech  (Fagus  sylvatica\  is  used  for  food. 

Sesame  oil  is  obtained  in  India,  Brazil,  Greece,  &c.,  from  the  seeds  of  Sesamum 
orientate  and  S.  indicum.  It  much  resembles  olive  oil,  and  is  used  for  the  sophistica- 
tion of  the  latter.  . 

Earth-nut  oil  is  obtained  from  Arachis  hypogcea  in  India  and  South  America  and 
much  resembles  oil  of  sesame. 

The  chief  drying  oils  are : — Hemp-oil,  obtained  from  the  hemp-seed  (Cannabis 
•sativa),  containing  about  25  per  cent,  of  "oil,  chiefly  used  for  making  black,  green,  or 
soft  soap.  When  fresh  pressed,  hemp-oil  possesses  a  bright  green  colour,  which  in 
time  becomes  a  brown-yellow.*  Linseed  oil,  like  the  former  a  so-called  drying  oil,  is 
obtained  from  the  well-known  linseed  (Linum  usitatissimum),  containing  about  22  per 
cent,  of  this  oil,  the  sp.  gr.  of  which  is  at  12  =  0*9395.  This  oil  consists  chiefly  of  a 
peculiar  glyceride  which,  on  being  saponified,  yields  a  fatty  acid  different  from  oleic 
acid ;  moreover,  linseed  oil  contains  some  palmitine.t 

Nut  oil,  from  the  nuts  of  Juglans  regia,  and  poppy  oil,  from  the  seeds  of  Papaver 
somniferum,  are  used  in  oil-painting  and  also  as  articles  of  food. 

Cotton  oil  is  now  obtained  in  vast  quantities  from  the  seeds  of  the  cotton  shrub,  and 
being  a  bye-product,  formerly  wasted,  it  is  sold  at  a  low  price.  It  consists  of  60  per 
cent,  linoleic  acid  and  40  per  cent,  oleic  acid.  It  is  used  as  an  article  of  food,  either 
alone  or  in  admixture  with  oleic  acid.  It  appears  to  be  perfectly  wholesome. 

The  Waxes,  with  the  exception  of  Japan  wax,  are  not  glycerides.  The  most  im- 
portant are — 

Beeswax,  collected  by  the  honey-bee,  Apis  inelliftca,  and  obtained  by  melting  out 
the  combs  with  warm  water.  It  is  yellow,  seldom  reddish,  and  may  be  bleached  by 
•exposure  to  air  and  light.  Yellow  wax  melts  at  from  61°  to  63°  ;  bleached  white  wax 
at  70°.  It  is  used  for  the  production  of  tapers,  candles,  &c.,  and  for  smoothing  thread,  &c. 

White  wax  is  often  adulterated  with  stearine,  paraffine,  or  ozokerite.  John 
first  observed  that  wax  is  a  mixture  of  these  substances;  the  one,  cerotic  acid, 
•C27H5402,  is  soluble  in  boiling  alcohol ;  the  other,  myricine,  is  sparingly  soluble  in 
alcohol,  and  consists,  according  to  Brodie,  of  the  meh'ssyl-ester  of  palmitic  acid, 
•C46H9,02  =  C16H31(C30H61)02.  The  difference  in  the  melting-point  of  different  sorts  of 
wax  is  due  to  the  different  proportions  of  the  two  constituents. 

Chinese  wax  is  now  imported  from  China  in  quantity,  and  is  derived  from  the  wax 
plant-louse,  Coccus  ceriferus,  which  deposits  it  upon  the  trees — especially  Rhus  succe- 
•danea.  It  much  resembles  spermaceti  in  appearance,  being  snow-white,  crystalline, 
brittle  and  fibrous,  and  fusible  at  82°.  On  dry  distillation  it  yields  cerotic  acid  and 
•cerotine,  a  body  resembling  paraffine.  According  to  Brodie,  Chinese  wax  is  the  ceryl- 
«ster  of  cerotic  acid,  C54H10802,  or  C2rH53(C2JH55)02, 

Andaquies  wax  is  produced  by  an  insect  found  on  the  Orinoco  and  the  Amazon.  It 
melts  at  77°,  has  the  sp.  gr.  0*917,  and  seems  to  have  the  same  composition  as  beeswax. 

*  Hempseed  oil  contains  70  per  cent,  linoleic  acid,  15  per  cent,  linolenic  acid,  and  15  per  cent, 
oleic  acid.— [EDITOE.] 

t  Linseed  oil  contains  linolenic  acid,  isolinolenic  acid  and  linoleic  acid.  Oleic  acid  is  almost 
•entirely  absent. — [EDITOR.] 


.•SECT,  viii.]  FATS.  907 

The  chief  vegetable  waxes  are : 

Japan  wax,  from  Rhus  vernicifera  and  R.  succedanea,  is  met  with  in  commerce 
in  round  discs,  soft  and  brittle ;  it  melts  at  42° ;  dissolves  in  boiling  alcohol,  and 
consists  chiefly  of  tripalmitine. 

Carnauba  wax  is  imported  from  Rio  de  Janiero,  and  forms  a  coating  on  the  leaves 
of  a  kind  of  palm-tree,  Copernicia  cerifera,  or  Corypha  cerifera.  It  consists  essentially 
of  palmitic  melissylester ;  it  melts  at  from  82°  to  83-5°,  and  on  account  of  its  high 
melting  point  it  serves  to  make  more  fusible  fats,  as  also  paraffine  and  ceresine  (mineral 
wax),  fit  for  the  manufacture  of  candles.  Of  late  it  has  been  used  in  the  soap  manufacture. 
Stuercke  has  isolated  from  it  a  hydrocarbon  melting  at  59°,  three  alcohols,  and  three 
acids,  an  alcohol  C26H53.CH9OH,  melting  at  76°,  also  myricyl  alcohol  C29H59.CH2OH, 
melting  at  85-5°,  from  which  there  was  obtained  melissic  acid,  C29H50.COOH,  melting  at 
•90°,  and  a  bi-acid  alcohol  C23H4S(CH2.OH)2,  having  a  melting-point  about  103-5°; 
from  this  alcohol  there  was  obtained  the  acid  C23H4G  (C02H)2  melting  at  102-5°.  An 
acid,  C23H,?.COOH,  melting  at  72-5°,  isomeric  with  lignoceric  acid;  then  an  acid, 
C2(iH53.COOH  melting  at  79°,  identical  or  isomeric  with  cerotic  acid  ;  lastly,  an  acid 
C19H3s.CH2OH.COOH,  an  oxy-acid  or  its  lactone,  C19H38CH2.O.CO,  melting  at  103-5°; 
from  this  there  was  obtained  the  acid,  C19H38(COOH)2,  melting  at  90°. 

Palm  wax,  from  the  bark  of  Ceroxylon  andicola,  a  palm  growing  in  the  upper  regions 
of  the  Andes,  is  obtained  by  scraping  and  boiling  with  water.  It  melts  at  from  83°  to 
86°,  and  is  perhaps  identical  with  Carnauba  wax. 

Myrtle  Wax  is  obtained  in  some  of  the  more  southern  American  States  on  boiling 
the  fruits  of  Myristica  cerifera  with  water.  It  melts  at  45°. 

Ucuhula  Wax,  obtained  in  the  Brazilian  province  of  Para  from  Myristica  surinam- 
ensis,  is  olive-green,  a,nd  melts  at  40°.  It  is  used  for  candles. 

Lubricants. — The  various  substances  used  for  lubricating  machinery  have  the  object 
of  diminishing  friction,  so  as  to  economise  motive  power  and  diminish  the  wear  and 
tear  of  the  parts  which  come  in  contact.  Such  mixtures  must  neither  contain  nor 
form  any  acid  capable  of  corroding  metals,  nor  must  they  thicken  in  the  air  as  do  the 
•drying  oils,  linseed  and  hemp-seed  oil. 

The  lubricants  chiefly  in  use  have  been  olive  and  rape  oil,  often  mixed  with 
mineral  oils ;  also  other  vegetable  and  animal  fats,  sometimes  with  the  addition  of 
graphite,  &c.,  also  resin  oils  and  paraffines.  The  heavier  mineral  oils  are  now  more  and 
more  coming  into  use  as  lubricants. 

The  American  mineral  oils  used  for  this  purpose  are  known  as  globe  oil,  Vulcan 
•oil,  topaz  oil,  star  oil,  &c.  Valvoline  is  obtained  from  Hamburg;  whilst  in  South 
Germany  we  more  commonly  meet  with  the  thick-flowing  Smaragd  oil,  dark 
brown,  with  a  green  fluorescence;  opal,  which  is  thin  and  yellow;  and  ruby  oil, 
-which  is  semi-solid  at  low  temperatures.  The  Russian  petroleum  workings  supply 
caucasine,  &c. 

A  lubricant  reduces  friction  merely  by  forming  a  layer  between  the  moving  sur- 
faces and  preventing  their  actual  contact.  The  friction  becomes  less  the  more  easily 
the  molecules. of  the  lubricant  move  upon  each  other.  If  the  pressure  is  very  strong, 
&  highly  fluid  oil  is  driven  out,  and  if  the  rotation  is  very  rapid  it  may  be  thrown 
out  centrifugally,  so  that  the  metallic  surfaces  come  into  immediate  contact.  Hence 
for  strong  pressures  there  is  required  a  thick  oil  of  little  fluidity,  and  for  light  pres- 
sures a  thin  and  very  fluid  oil.  The  oil  must  therefore  be  selected  with  due  regard  to 
the  weight  of  the  machinery,  to  its  speed  of  rotation,  and  to  the  prevailing  tempera- 
ture. No  one  lubricating  oil  is  equally  well  adapted  for  all  purposes. 

The  examination  of  lubricants  must  include  the  detection  and  determination  of 
any  free  acid,  and  the  determination  of  the  coefficient  of  friction  for  different  pressures 
and  temperatures. 


908 


CHEMICAL   TECHNOLOGY. 


[SECT.  vin. 


Fig.  582. 


A 


In  order  to  ascertain  the  fluidity  of  an  oil  at  different  temperatures,  the  author 
uses  the  apparatus,  Fig.  582.  The  outflow  of  the  copper  cylinder,  A,  consists  of  a  fine 
platinum  tube,  1*2  mm.  in  width  and  5  mm.  in  length,  enclosed  in  a  thicker  copper 
tube,  a.  The  latter  expands  at  its  top  like  a  funnel,  and  can  be  closed  by  the  cone,  c, 
the  handle  of  which  works  up  or  down  in  a  guide-frame,  secured  to  the  vessel. 
The  inner  vessel  is  connected  by  three  slips  of  sheet-metal,  e,  to  the  external 
vessel,  B,  which  rests  on  three  feet,  n  centimetres  high  and  not  shown  in  the 
figure.  In  use,  the  vessel,  A,  is  filled  up  to  a  mark  with  65  c.c.  of 
the  oil  in  question,  the  vessel,  B,  is  filled  with  cold  or  warm 
water,  and  the  oil  is  stirred  with  a  sensitive  thermometer,  until 
both  it  and  the  water  outside  are  at  the  desired  temperature.  A 
bottle  holding  50  c.c.,  with  a  narrow  neck,  is  placed  between 
the  efflux  opening,  the  stopper,  c,  is  raised,  and  the  time  required 
for  50  c.c.  to  flow  into  the  bottle  is  carefully  noted.  The  end  of 
the  tube  projecting  out  of  the  vessel,  B,  is  expanded,  whence  its 
cylindrical  portion,  which  determines  the  speed  of  flowing,  has 
the  same  temperature  as  the  liquid  used  for  the  experiment. 

Varnishes. — By  varnish  we  understand  a  liquid  of  an  oily  or 
resinous  nature  employed  for  coating  various  objects,  the  thin  film 
becoming  dry  and  hard,  thus  protecting  the  object  on  which  it  is 
laid  from  the  action  of  air  and  water,  and  at  the  same  time  im- 
parting a  glossy  and  shining  surface. 

Linseed  Oil  Varnishes. — Oil  varnishes  are  usually  prepared  from  linseed  oil,  but 
sometimes,  especially  for  artist's  purposes,  poppy  seed  and  walnut  oil  (so-called 
drying  oils)  are  used.  Linseed  oil  (raw)  becomes  slowly  converted  by  the  action 
of  the  air  into  a  tough,  elastic,  semi-transparent  mass  ;  but  this  property  is  possessed 
in  a  far  higher  degree  by  the  so-called  boiled  oil — that  is  to  say,  an  oil  which 
has  been  brought  by  the  action  of  heat  and  of  oxidising  materials  into  a  state 
of  greater  activity,  in  fact,  into  a  state  of  incipient  slow  oxidation,  the  result 
of  which  is  the  formation  of  the  substance  termed  by  Dr.  G.  J.  Mulder*  linoxine, 
which  in  many  of  its  properties  corresponds  to  caoutchouc.  The  drying  of  oil 
varnishes  is  not  therefore  due  to  evaporation  (leaving,  as  is  the  case  with  alcohol 
varnishes,  a  coherent  film  of  resin),  but  to  the  oxidising  action  of  the  oxygen  of  the 
air,  whereby  a  coherent  film  of  linoxine  is  formed.  Linseed  oil  (raw)  is  converted  into 
so-called  boiled  oil  by  boiling  with  litharge,  zinc  oxide,  and  manganese  peroxide,  which 
act  upon  the  elaine,  palmitine,  and  myristine  of  the  linseed  oil.  The  greater  part  of 
the  linseed  and  other  drying  oils  is  linoleirie,  3(C.,2H2703).C6H.03,  which  by  slow  oxida- 
tion becomes  linoxine  =  C,,H.,,O  ,,  by  the  action  of  alkalies  converted  into  linoxic  acid, 

OJ  £j          II7  •/ 

HO.C32O25O9.  It  is  certainly  preferable  to  carry  this  operation  into  effect  upon  the 
water  bath,  or  at  least  in  vessels  provided  with  steam  jackets.  The  oxides  are  employed 
in  coarse  powders,  which  are  suspended  in  a  linen  bag  in  the  oil.  In  practice,  i  part 
of  zinc  oxide  or  litharge  is  taken  to  16  parts  of  raw  oil;  and  of  the  manganese 
i  part  to  10  of  oil;  the  oxides  become  partially  dissolved  in  the  oil,  while  they  aid 
in  converting  the  palmitine,  &c.  (not  linoleine),  into  plaster  (lead  or  zinc  soap). 
Boiled  linseed  oil  usually  contains  from  2-5  to  3  per  cent,  of  litharge  dissolved. 
Neither  the  addition  of  zinc  sulphate,  nor  such  absurdly  added  substances  as 
onions,  bread  crust,  or  beetroot,  have  any  result  whatever.  Linseed  oil  intended  to 
be  mixed  with  zinc  white  should  not  be  boiled  with  litharge,  but  with  manganese 
peroxide.  The  lower  the  temperature  at  which  linseed  oil  is  boiled  the  brighter 
its  colour.  Mulder  found  that  when  raw  linseed  oil,  especially  if  old,  was  kept  for  from 

*  This  author  published  some  rears  ago  in  the  Dutch  language  a  highly  interesting  and  valuable 
work — practically  as  well  as  scientifically — on  the  drying  oils. 


SECT,  viii.]  FATS.  909 

twelve  to  eighteen  hours  at  a  temperature  of  100°,  it  acquired  the  property  of  boiled 
oil.     Sometimes,  after  boiling,  linseed  oil  is  bleached  by  exposing  it  in  shallow  trays 

10  centimetres  deep,  best  made  of  sheet  lead,  covered  with  sheets  of  glass,  to  the 
action  of   strong  summer  sunlight.      Liebig's   recipe   for  making  a  bright   varnish 
is  the  following  : — To  10  kilos,  of  raw  linseed  oil  are  added  300  grammes  of  finely 
pulverised   litharge,   after   which   there   is   added   a   solution   of    600    grammes    of 
lead  acetate.     The   mixture  is   vigorously  stirred,  and,  after  the  subsidence  of  the 
materials,    the   clear   varnish    is    ready   for    use.      Manganese   borate    is,  according 
to   Barruel  and  Jean,  an   excellent  so-called   siccative   (dryer)   when  added  to  raw 
linseed  oil,  i  part  to   100  of  oil.     Mulder's  experiments  confirm  this  statement  in 
every  respect. 

Varnish  for  Paper  Hangings. — The  varnish  used  for  fixing  gold  or  shearings  of 
dyed  wool  upon  paper-hangings,  &c.,  is  a  solution  of  linseed  oil  and  lead  plaster  in  oil 
of  turpentine.  The  mixture  is  obtained  by  first  saponifying  linseed  oil  with  caustic 
alkali  and  precipitating  the  aqueous  solution  of  this  soap  with  a  solution  of  lead  acetate. 
The  lead  soap  thus  obtained  is  next  dissolved  in  oil  of  turpentine. 

Printing  Ink. — This  is,  when  genuine  and  when  prepared  from  good  linseed  or 
Avalnut  oil,  anhydride  of  linoleic  acid,  C32H27O3,  mixed  with  very  finely  divided  lamp- 
black, and  obtained  by  heating  raw  linseed  oil  for  several  hours,  at  a  high  tempera- 
ture  (from  315°  to  360°),  whereby  the  fatty  constituents — glycerine,  palmitine,  &c. — are 
volatilised.  Usually  the  oil  is  heated  in  vessels  directly  exposed  to  the  action  of  fire, 
and  as  the  colour  of  the  ink  is  black,  a  deep  colour  from  the  residue  of  the  heating  of  the 

011  is  not  of  much  consequence.     In  order  to  render  printing  ink  more  rapidly  drying, 
some  manganese  borate  may  be  heated  with  it  at  315°  for  some  hours.     The  quantity 
of  fine  lamp-black  (best  re-ignited  in  close  vessels,  or  exhausted  with  boiling  alcohol) 
usually  added  to  printing  ink,  amounts  to  about  16  per  cent.     Soap  is  necessary  to  be 
added  in  order  to  prevent  smearing  and  assist  in  obtaining  sharpness  of  impression. 
Coloured  printing  inks  are  obtained  by  adding  to   boiled   oil  red  or  blue  or  other 
pigments ;  for  red,  vermilion  is  used.     The  ink  used  in  lithography  and  copper-plate 
printing  is  made  thicker,  a  better  black  being  added. 

The  varnish  for  lithographic  ink  has  to  be  thicker  than  that  for  book- work.  Copper- 
plate ink  is  a  mixture  of  thick  varnish  with  Frankfurt  black.  Instead  of  linseed  or 
nut-oil,  bankul-oil  (from  Aleurites  triloba)  has  been  proposed  for  the  preparation  of 
printing  ink. 

Fat  Varnishes. — The  so-called  fat  or  oil  varnishes  are  solutions  of  resins  in  boiled 
linseed  oil  mixed  with  oil  of  turpentine,  benzol,  or  benzoline.  Amber,  copal,  anime, 
gum  dammar,  and  asphalte,  are  among  the  more  ordinary  resins  employed  for  this 
purpose,  the  varnishes  being  made  by  melting,  with  the  aid  of  gentle  heat,  the  amber, 
copal,  &c.,  to  which,  while  liquid,  boiling  linseed  oil  is  added.  The  cauldron  in  which 
this  operation  takes  place  should  be  only  two-thirds  filled ;  and  the  mixture  of  oil  and 
resin  kept  boiling  for  ten  minutes.  The  cauldron  having  been  removed  from  the  fire 
its  contents  are  allowed  to  cool  down  to  140°,  when  the  oil  of  turpentine  is  added. 
The  quantities  by  weight  are  10  parts  copal  or  amber,  20  to  30  boiled  linseed  oil,  25  to 
30  oil  of  turpentine.  Black  asphalte  varnish  is  obtained  in  a  similar  manner  by 
treating  3  parts  of  asphalte,  4  of  boiled  linseed  oil,  and  15  to  18  parts  of  oil  of  turpen- 
tine. Dark  coloured  amber  varnish  is  not  prepared  from  amber,  but  from  the  residue 
(amber  colophonium)  of  the  distillation  of  the  empyreumatic  oil  of  amber  arid  succinic 
acid  left  in  the  still  from  the  preparation  of  succinic  acid.  These  varnishes  are  the 
most  durable,  but  they  dry  slowly,  and  are  more  or  less  coloured. 

Spirit  Varnish. — The  so-called  spirit  varnishes  are  solutions  of  certain  resins — vis., 
sandarac,  mastic,  gumlac  (shellac),  anime  in  alcohol,  aceton,  wood  spirit,  benzoline,  or 
carbon  disulphide.  Good  spirit  varnish  ought  to  dry  rapidly,  give  a  glossy  surface, 


910  CHEMICAL  TECHNOLOGY.  [SECT,  vm, 

adhere  strongly,  and  be  neither  brittle  nor  viscous.  As  shellac  is  frequently  employed, 
the  name  of  lac  varnish  is  sometimes  given  to  these  varnishes.  The  spirit,  usually 
methylated  spirit,  ought  to  be  strong,  about  92  per  cent.  The  solution  of  the  resins 
is  promoted  by  the  addition  of  one-third  of  their  weight  of  coarsely  powdered  glass  for 
the  purpose  of  preventing  the  resinous  matter  caking  together,  and  being  thus  to  some 
extent  withdrawn  from  the  solvent  action  of  the  alcohol.  In  order  to  render  the- 
coating  remaining  from  the  evaporation  of  the  spirit  less  brittle,  Venice  turpentine  is- 
usually  added.  Sandarac  varnish  is  obtained  by  dissolving  10  parts  of  sandarac- 
and  i  of  Venice  turpentine  in  30  of  spirit.  Shellac  varnish,  more  durable  than  the 
former,  is  obtained  by  dissolving  i  part  of  shellac  in  3  to  5  of  spirits.  French  polish  is  a 
solution  of  shellac  in  a  large  quantity  of  spirits,  and  when  this  polish  is  to  be  applied  to 
white  wood,  the  varnish  is  bleached  by  filtration  over  animal  charcoal.  Copal  varnish, 
far  superior  to  the  foregoing,  is  made  by  first  melting  the  resin  at  as  gentle  a  heat  as- 
possible  so  as  to  prevent  the  coloration  of  the  substance,  which  is  next  pulverised,, 
mixed  with  sand,  treated  with  strong  alcohol  on  a  water  bath,  and  filtered.  A  solution 
of  turpentine  or  elemi  resin  is  added  to  render  the  varnish  softer.  Colourless  copal 
varnish  is  obtained  by  pouring  over  6  kilos,  of  previously  pulverised  and  molten  copal,, 
contained  in  a  vessel  which  may  be  closed,  6  kilos,  of  alcohol  at  98  per  cent.,  4  kilos,  of 
oil  of  turpentine,  and  i  kilo,  of  ether ;  the  vessel  containing  this  mixture  having  been 
closed  is  gently  heated.  The  solution  is  clarified  by  decantation. 

Lacquers. — These  are  used  chiefly  for  the  purpose  of  coating  instruments,  and" 
other  objects  of  brass  and  coloured  metallic  alloys,  so  as  to  prevent  the  action  of  the 
atmosphere.  Such  varnishes  are  used  for  imparting  a  gold-colour  to  base  metals ;  for 
this  purpose  alcoholic  tinctures  of  gamboge  and  dragon's  blood,  or  magenta,  picric 
acid,  Martius  yellow,  and  coralline,  are  separately  prepared  and  added,  in  quantities 
found  by  trial,  to  a  varnish  consisting  of  2  parts  of  seed  lac,  4  of  sandarac,  4  of  elemi, 
and  40  of  alcohol. 

Turpentine  Oil  Varnishes. — These  are  prepared  in  the  same  manner  as  the  pre- 
ceding. They  dry  more  slowly,  but  are  less  brittle  and  more  durable.  Common 
turpentine  oil  varnish  is  obtained  by  dissolving  ordinary  resin  in  oil  of  turpentine ;. 
but  this  varnish  is  liable  to  crack.  Copal  is  either  dissolved  in  oil  of  turpentine 
without  or  after  having  been  melted ;  in  the  latter  case  the  varnish  being  coloured. 
When  non-melted  copal  is  used  it  is  broken  into  small  lumps,  and  is  suspended  in  a. 
stout  canvas  bag  over  the  surface  of  the  oil  of  turpentine  contained  in  a  glass  flask, 
and  placed  on  a  sand  bath,  the  vapours  arising  from  the  oil  of  turpentine  gradually 
dissolving  the  copal.  Dammar  gum  resin  varnish,  made  with  oil  of  turpentine,  is 
prepared  by  drying  the  resin  at  a  gentle  heat  and  dissolving  it  in  from  three  to  four  times 
its  weight  of  oil  of  turpentine.  This  varnish,  though  colourless,  is  not  very  durable. 
Green  turpentine  oil  varnish  is  prepared  by  dissolving  sandarac  or  mastic  in  con- 
centrated caustic  potash  solution,  diluting  with  water,  and  precipitating  with  acetate 
of  copper,  the  dried  precipitate  being  dissolved  in  oil  of  turpentine. 

Polishing  the  Dried  Varnish. — In  order  to  increase  the  gloss  of  varnished  surfaces 
especially  on  metallic  objects  and  coaches,  carriages  and  woodwork  in  theatres,  concert- 
rooms,  halls,  &c.,  the  dry  surface  is  first  rubbed  over  with  soft  felt,  on  which  some  very 
fine  pumice-powder  is  laid,  and  is  next  polished  with  very  soft  woollen  tissue  on  which 
some  oil  and  rotten-stone  is  placed,  the  oil  being  rubbed  off  with  starch-powder. 
Instead  of  varnishes,  solutions  of  collodion  (fulminating  cotton  in  alcohol  and  ether), 
and  solutions  of  water-glass  are  sometimes  used ;  while  Puscher  recommends  a  solution 
of  shellac  in  ammonia,  largely  used  by  hatters. 

Pettenkofer's  Process  for  Restoring  Pictures. — In  order  to  remove  the  cracks  often 
observed  in  old  pictures,  Von  Pettenkofer  has  suggested  exposure  to  the  vapour  of 
alcohol  at  the  ordinary  temperature  of  the  air,  the  picture  being  placed  in  an  air-tight- 


SECT.    VIII.]  SOAP.  9II 

box,  at  the  bottom  of  which  is  a  tray  containing  alcohol.  This  method  has  been  tried, 
but  not  only  has  it  failed  in  many  cases,  but  some  pictures  have  been  completely  spoiled. 
According  to  Dr.  G.  J.  Mulder's  researches,  the  only  effective  preservative  of  pictures 
is  complete  exclusion  of  air.  He  suggests  that  pictures  should  be  well  varnished  on 
the  painted  side  as  well  as  on  the  back,  and  next  hermetically  covered  with  well-fitting 
sheets  of  polished  glass  on  the  front,  and  some  substance  on  the  back  impermeable  to 
air.  The  real  cause  of  the  ultimate  destruction  of  pictures  as  well  as  of  paint  is  the 
gradual,  but  continuous,  yet  slow,  oxidation  of  the  linoxine,  resulting  in  the  crumbling 
to  powder  of  the  pulverulent  matter — pigments — used  as  colours.  It  may  not  here  be 
out  of  place  to  state  that  one  of  the  best  solvents  of  linoxine  (dried  paint)  is  a  mixture- 
of  alcohol  and  chloroform,  which  may  be  advantageously  used  to  remove  stains  of  paintr 
and  also  of  waggon  and  carriage  grease  from  silk  and  woollen  tissues. 

Linseed  oil  varnish  mixed  with  white  lead,  litharge,  or  red  lead,  or  with  a  mixture 
of  10  parts  litharge  and  90  parts  elutriated  chalk  is  used  for  cementing  articles  of  glass- 
or  porcelain.  Instead  of  the  chalk,  there  may  be  taken  lime  slacked  to  a  powder,  and 
instead  of  litharge  zinc  white. 

As  a  cement  for  steam-pipes,  &c.,  Stephenson  uses  a  mixture  of  2  parts  litharge,, 
i  part  lime  slacked  to  a  powder,  and  i  part  sand,  the  whole  intimately  mixed  with  hot 
linseed  oil  varnish.  If  alum  soap  (obtained  by  precipitating  solution  of  alum  with  soda- 
soap)  is  dissolved  in  hot  linseed  oil,  we  obtain  a  mixture  suitable  for  cementing  stones. 
Common  glaziers'  putty  is  made  by  grinding  up  chalk  with  boiled  linseed  oil.  If  the 
oil  has  not  been  boiled  it  sets  very  slowly.  Glycerine  putty,  a  mixture  of  glycerine- 
with  litharge,  is  excellent  for  joining  iron  to  iron,  stone  to  stone,  and  iron  to  stone. 
The  best  proportions  are  50  grammes  litharge  to  5  c.c.  glycerine. 

Iron  putty  consists  of  ferric  oxide  ground  up  with  boiled  linseed  oil ;  it  resists  acids- 
well* 

SOAP. 

Soap,  in  the  common  acceptation  of  the  word,  is  the  product  of  the  action  of  caustic 
alkalies  upon  fats,  and  consists  essentially  of  potassium  or  sodium  stearate,  palmitate,. 
or  oleate.  Though  soap  was  known  in  the  pre-historic  ages,  its  manufacture  was  not 
properly  conducted  until  Chevreul  ascertained  the  nature  of  fats  and  the  principles  of 
saponification,  and  until  the  soda  industry  was  developed. 

The  raw  materials  for  soap  are  of  two  kinds,  the  natural  fats  or  the  fatty  acids  and 
the  lye,  an  aqueous  solution  of  caustic  potash  or  soda. 

The  soap-boiler  now  rarely  prepares  caustic  lye  for  his  own  use.  He  generally  finds 
it  more  convenient  to  buy  solid  caustic  soda  and  potash  from  the  alkali  manufacturers. 
Usually  three  different  kinds  of  lye  are  prepared  and  kept,  viz. :  (i)  Strong  lye,  18  to- 
20  percent,  of  alkali;  (2)  Middling  strong  lye,  8  to  10  percent,  of  alkali ;  and  (3)  Weak 
lye,  containing  only  i  to  4  per  cent,  of  alkali.  This  weak  liquor  is  commonly  used 
instead  of  water  for  lixiviating  a  new  soda-ash  and  lime  mixture.  The  sodium-aluminate 
obtained  by  the  decomposition  of  cryolite  is  used  in  the  United  States  under  the  name 
Natrona  refined  saponifier,  for  soap  manufacturing  purposes.  Sodium  sulphide  may 
also  be  used  instead  of  caustic  alkali. 

Theory  of  Saponification. — Before  Chevreul  published  his  researches,  it  was  supposed 
that  fats  and  oils  possessed  the  property  of  combining  with  alkalies.  Chevreul  found, 
however,  that  fats  separated  from  their  state  of  combination  as  soaps  possessed 
properties  differing  from  those  existing  before  they  were  saponified,  the  fact  being 
that  the  substances  we  are  acquainted  with  as  oils  or  fats  are  compounds  of  peculiar 
acids,  stearic,  palmitic,  margaric,  oleic,  all  non-volatile  substances ;  while  certain  fats 
which  give  off  a  peculiar  odour  contain,  in  addition  to  these  acids,  volatile  fatty  acids, 

*  On  cements  the  reader  may  compare  Spon's  "  Encyclopaedia  of  Industrial  Arts,"  pp.  623,  et  seq. 

— [EDITOR] 


912  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

as  butyric,  capric,  capronic,  valerianic,  <fec.  The  volatile  acids  in  the  ordinary  oils 
and  fats  are  combined  with  a  sweet  material,  discovered  by  Scheele,  and  known  under 
the  name  of  glycerine. 

According  to  Berthelot's  researches,  it  is  held  that  all  the  oils  and  fats  which  are 
used  in  soap-making  are  ethers  of  glycerine,  C3H8O3,  that  substance  being  viewed  as  a 

C  H  ~1 

trivalent  alcohol,   3    5  VO3.     Palmitine,  for  instance,  the  main  constituent  of  palm-oil, 

•H-aJ 

is  glyceryl-tripalmitate,  or  tripalmitine,  that  is  to  say,  glycerine  in  which  three  atoms 

C  H         "I 

of  hydrogen  are  replaced  by  the  radical  of  palmitic  acid,   3    s         l03.      Stearine  (tri- 

3^16^31^'  ) 

stearine)  and  oleine  (trioleine)  have  an  analogous  constitution.     When  the  fats,  take 

palm-oil  for  instance,  are  saponified  with  caustic  alkalies,  say  caustic  soda,  the  fat — 

that  is,  in  chemical  parlance,  the  ether — is  decomposed  into  alcohol,  i.e.,  glycerine, 
and  soda  palmitate,  i.e.,  soap,  according  to  the  following  equation  : — 


Tripalmitine         ^4r 

^30,6H3l 

and  caustic  soda,  3lS"aOH, 


s  ( 


Glycerine, 


and  soap,  or  sodium  palmitate,  3  \  W6    32    I  O. 

v.  (  JN  a         j 


The  glycerine  formed  during  the  process  of  saponification  remains,  after  the  separa- 
tion of  the  soap,  dissolved  in  the  mother  liquor  from  which  it  is  prepared.  It  is  clear 
that  such  fats  as  palm-  and  cocoa-nut  oil,  which  in  their  ordinary  state  contain  fatty 
acids,  are  more  readily  saponified  than  the  perfectly  neutral  fats,  viz.,  olive-oil  and 
tallow ;  while  the  oleic  acid  derived  from  the  stearine  candle  manufactories  is  readily 
saponified  by  carbonated  alkalies.  This  operation  applies  to  colophonium  (resin), 
which  consists  essentially  of  a  peculiar  acid,  pinic  acid,  but  in  these  instances  no  real 
saponification  takes  place,  inasmuch  as  no  glycerine  is  formed.  The  decomposition  of 
a  fat  by  an  alkali  does  not  take  place  suddenly  and  throughout  the  whole  of  the  fat 
at  once,  in  the  manner  of  inorganic  salts,  but  passes  through  several  stages,  the  first 
being  the  formation  of  an  emulsion  of  lye  and  fat ;  next  fat  acids  and  fat  acid  salts  are 
formed,  retaining  the  rest  of  the  fatty  matter  in  suspension ;  gradually  the  free  fatty 
matter  is  saponified,  and  the  fat  acid  salts  are  converted  into  neutral  salts,  or,  in  other 
words,  soap. 

When  caustic  potassa  is  used,  soft  soaps  are  produced,  while  the  hard  soaps  result 
from  the  use  of  caustic  soda.  We  distinguish  soaps — 

(a)  As  hard  soaps  or  soda  soaps ; 
(£)  As  soft  soaps  or  potassa  soaps. 

According  to  the  fatty  substances  used  in  soap-boiling,  soaps  are  distinguished  as 
tallow,  oil,  palm-oil,  oleic  acid,  cocoa-nut,  fish-oil,  and  resin  soaps,  &c.  Technically, 
hard  soaps  may  be  divided  into : — 

(1)  Grain  soap ; 

(2)  Smooth  soap; 

(3)  Filled  soap. 

(1)  Grain  soap  takes  its  name  from  the  fact  that  the  finished  soap  when  being  salted 
out  from  solution  separates  from  the  spent  lye  in  the  state  of  semi-solid,  rounded  lumps 
or  grains,  which  solidify  to  a  uniform  mass  free  from  bubbles.    It  is  the  only  pure  soap, 
being  freed  by  the  salting  out  from  glycerine,  superfluous  lye,  excess  of  water,  or  other 
impurities.     The  majority  of  soap-boilers  no  longer  make  this  kind. 

(2)  Smooth  soap  is  made  by  what  is  called  polishing  the  grain  soap.     If  such  soap  is 
boiled  in  the  pan  with  water  or  weak  lye  it  takes  up  a  proportion  of  water,  and  loses 
the  power  of  marbling.     It  is  distinguished  from  grain  soap  merely  by  its  larger 
proportion  of  water. 

(3)  Filled  soaps  are  now  unfortunately  the  commonest.     They  are  30  imperfectly 


SECT.    VIII.]  SOAP.  9!3 

salted  out  that  the  entire  contents  of  the  pan  remain  together  and  are  sold  as  soap. 
On  cooling,  the  whole  solidifies,  and  does  not  betray  its  proportion  of  water. 

This  property  of  appearing  dry  and  hard,  along  with  a  heavy  percentage  of  water, 
is  a  peculiarity  of  cocoa-nut  oil  soaps,  which  communicate  the  same  property  to  tallow 
and  palm-oil  soaps.  A  yield  of  200  to  300  kilos,  soap  from  100  kilos,  fat  is  nothing 
uncommon,  especially  if  water-glass  is  used. 

The  mixture  of  oil  100  kilos.,  resin  70  to  80  kilos.,  water-glass  300  kilos.,  talc  100 
to  150  kilos.,  and  soda-lye  at  56°  Tw.  240  kilos.,  gives  a  yield  of  800  kilos,  of  a  product 
which  sells  as  soap. 

Chief  Varieties  of  Soap. — The  German  tallow  soap  or  curd  soap  is  essentially  a 
mixture  of  sodium  stearate  and  palmitate,  and  it  is  commonly  prepared  indirectly 
by  first  saponifying  tallow  with  caustic  potassa,  and  next  converting,  by  means  of 
common  salt,  the  potassium  stearate  and  palmitate  into  the  corresponding  sodium  com- 
pound. 

The  soap-boiling  pan  employed  is  somewhat  conical  in  shape.  It  is  made  of  cast- 
iron,  and  provided  at  the  top  with  a  high  lintel  or  bulwark  to  prevent  any  fluid  boiling 
over.  Supposing  it  to  be  intended  to  convert  10  cwts.  of  tallow  into  soap :  Into  the 
cauldron  is  first  poured  about  500  litres  of  strong  lye  at  20  per  cent.  (  =  i-226  sp.  gr.) ; 
next  the  tallow  is  added,  and  a  wooden  or  iron  lid  having  been  fitted  to  the  cauldron, 
the  fire  is  kindled.  When  ebullition  sets  in,  it  is  kept  up,  with  occasional  stirring  of 
the  contents  of  the  cauldron,  for  five  consecutive  hours.  The  materials  in  the  cauldron 
are  converted  into  soap-glue,  as  it  is  termed,  a  gelatinous  mass,  which,  if  the  operation 
has  been  well  conducted,  ought  not,  upon  the  addition  of  fresh  lye,  to  become  thin, 
while  it  also  should  not  flow  in  drops,  but  similarly  to  treacle  from  a  spatula.  The 
production  of  this  substance  is  promoted  by  adding  oil  of  tallow  to  the  lye  gradually  and 
in  small  portions  at  a  time. 

Mege-Mouries  recommends  either  yolks  of  eggs,  bile,*  or  albuminous  compounds. 
As  proved  by  the  researches  of  F.  Knapp,  it  is  always  advantageous  to  first  convert 
the  fat,  with  the  requisite  quantity  of  lye,  into  an  emulsion,  and  to  leave  the  lye  either 
not  heated  at  all  or  only  to  50°  in  contact  with  the  fat,  so  as  to  saponify  first  slowly  in 
the  cold  and  to  finish  off  Avith  ebullition.  When  caustic  soda-lye  is  used  it  is  of  a  density 
of  from  14°  to  17°  Tw.  (=1-072  to  ro88  sp.  gr.).  When  the  saponification  is  complete 
the  operation  of  fitting  or  parting  is  proceeded  with,  and  consists  in  adding  from  12  to 
1 6  Ibs.  of  salt  to  100  of  tallow.  The  soap  is  kept  boiling  until  the  soap-glue  has  become 
a  greyish  mass,  from  which  the  mother  liquor  or  under-lye  readily  separates,  the  latter 
being  let  off  by  a  tap ;  or,  if  no  tap  is  fitted  to  the  cauldron,  the  soap  is  gradually 
ladled  over  into  the  cooling  tank.  The  addition  of  salt  not  only  aims  at  the  separation 
of  the  soap  from  the  lye,  but  also  at  the  partial  conversion  of  the  potassp.  into  soda- 
soap.  If  the  soap-glue  has  been  removed,  it  is  again  put  into  the  cauldron,  and  there 
is  added  a  moderately  strong  lye,  and  heat  again  applied.  The  soap  again  becomes 
quite  fluid,  but  consists  chiefly  of  soda-soap  glue.  The  ebullition  is  kept  up,  and 
during  its  continuance  fresh  lye  and  salt  are  added  alternately.  By  continued  boiling 
the  soapy  mass  becomes  more  and  more  concentrated ;  as  soon  as  the  foaming  ceases, 
and  the  whole  mass  is  in  a  steady  ebullition,  it  is  again  ladled  over  into  the  cooling- 
tank,  or  the  mother  liquo'r  is  tapped  off.  The  object  to  be  gained  by  this  second 
boiling  is  the  conversion  of  the  material  into  a  uniform  mass  free  from  air-bubbles ; 
this  object  is  promoted  by  beating  with  iron  rods.  The  hot  soap  is  next  placed  in  a 
wooden  box,  so  constructed  that  it  can  be  taken  to  pieces;  upon  the  bottom  of  this  box, 
which  is  perforated,  a  piece  of  cloth  is  stretched,  so  as  to  allow  of  any  adhering  lye 
running  off.  When  the  soap  is  cool  the  box  is  taken  to  pieces,  the  soap  cut  into  bars,  and 

*  Ox-gall  is  the  finest  soap  known  for  cleansing  dyed  goods,  especially  silks.  Its  synthetic  pro- 
duction  without  the  unpleasant  smell  would  be  a  most  valuable  invention.— [EDITOE.] 


9 14  CHEMICAL  TECHNOLOGY.  [SECT.  viir. 

these  are  placed  in  a  cool,  dry  room.  The  cutting  of  the  soap  into  bars  is  now  effected 
by  machinery ;  formerly  it  was  performed  by  hand  with  a  peculiar  tool,  a  copper-wire 
with  suitable  handles,  such  as  cheesemongers  sometimes  use.  10  cwts.  of  tallow  yield 
on  an  average  i6|  cwts.  of  soap,  which  by  drying  loses  some  10  per  cent.  As  it  is 
impossible,  even  with  repeated  applications  of  salt,  to  convert  potassa-soap  completely 
into  soda-soap,  the  German  curd-soap,  or  Kernseife,  is  always  mixed  with  a  considerable 
quantity  of  potassa-soap,  to  which  it  owes  its  peculiar  softness.  According  to  the 
researches  of  Dr.  A.  C.  Oudemans  (1869),  only  half  the  potassa  is  converted  into  soda- 
soap. 

Olive  Oil  Soap. — This  kind  of  soap,  also  known  as  Marseilles,  Venetian,  or  Castilian 
soap,  is  chiefly  prepared  in  the  southern  parts  of  Europe.  The  olive  oil  is  frequently 
mixed  with  other  kinds  of  oil,  such  as  linseed,  poppy  seed,  cotton-seed  oil,  &c.  Two 
kinds  of  lye  are  employed  in  the  preparation  of  this  soap ;  the  first  lye  is  only  a  caustic 
soda  solution,  and  used  for  fitting  or  preparatory  boiling ;  the  other  lye  is  mixed  with 
common  salt,  and  intended  to  effect  the  separation  of  the  soap.  The  preparatory 
boiling  aims  at  the  formation  of  an  emulsion  or  the  production  of  an  etat  globulaire, 
whereby  the  contact  of  oil  and  alkali  is  greatly  promoted,  and  a  real  soap-glue 
ultimately  results.  In  order  to  remove  the  water  from  this  material  as  much  as 
possible,  a  lye  containing  common  salt  is  employed,  and  lastly  by  a  third  boiling  the 
saponification  is  rendered  complete.  By  the  use  of  the  lye  containing  common  salt  it 
is  possible  to  keep  the  soap-glue  in  such  a  condition  that  it  can  take  up  alkali  without 
combining  with  the  water.  The  preparatory  boiling,  or  fitting,  is  carried  on  in  large 
copper  vessels,  capable  of  containing  250  cwts.,  the  caustic  soda  employed  for  this 
purpose  having  a  strength  of  from  8'2°  to  12*5°  Tw.(=  i-o4i  to  1*064  SP-  gr-)-  The  lye 
is  brought  to  ebullition  first,  and  the  oil  to  be  saponified  is  next  added,  care  being  taken 
to  stir  the  mixture  in  order  to  promote  the  reaction.  Gradually  the  mass  becomes  thick, 
and  as  soon  as  black  vapours  arise,  due  to  the  decomposition  of  a  small  quantity  of  the 
soap-glue  by  coming  in  contact  with  the  very  hot  copper,  there  is  added  the  stronger  lye 
of  30°  Tw.  (1-157  sp.  gr.).  If  it  is  intended  to  produce  a  blue- white  soap,  some  sulphate 
of  iron  is  added.  As  soon  as  the  mass  has  become  sufficiently  thick,  the  soda-lye, 
mixed  with  salt,  is  added.  After  some  hours  the  soap  entirely  separates  from  the 
mother  liquor,  which  is  then  run  off,  and  fresh  lye  added,  also  containing  common  salt. 
The  final  boiling  is  then  proceeded  with,  the  lye  having  a  strength  of  from  30°  to  45°  Tw. 
The  ebullition  is  continued  gently  until  the  alkali  is  exhausted,  when  the  mother  liquor 
is  again  run  off,  and  fresh  lye  mixed  with  common  salt  again  added ;  this  operation  is 
repeated  some  four  to  six  times,  when  the  soap  is  at  last  quite  ready.  This  stage  is 
indicated  by  the  absence  of  all  smell  of  oil  and  the  peculiar  grain  of  the  mass,  which 
is  left  to  cool;  but  if  sulphate  of  iron  has  been  added,  it  is  necessary  to  stir  the 
soap  continuously  until  nearly  cold,  in  order  to  produce  the  mottled  appearance  due  to- 
the  formation  of  iron  sulphide  from  the  sulphate  by  the  action  of  the  sodium  sulphide 
of  the  soda-lye.  Mottled  soap  is  produced  in  England  by  adding  a  concentrated 
solution  of  crude  caustic  soda,  containing  sodium  sulphide,  to  the  liquid  soap,  pre- 
viously being  impregnated  with  iron  sulphate.  When  nearly  cold  the  soap  is  placed 
in  wooden  boxes  and  left  to  completely  solidify.  After  from  ten  to  twelve  days  it  is- 
ready  for  being  cut  into  bars.  64  litres  of  oil  =58  to  60  kilos.,  yield  from  90  to  95 
kilos,  of  soap.  White-oil  soap  is  prepared  in  a  similar  manner,  but  purer  materials 
are  employed.  A  good  sample  of  Marseilles  mottled  soap  should  contain  • — 

I.  n. 

Fat  acids 63  ...  62 

Alkali 13  ,..  ii 

24  ...  27 

100  100 


SECT,  viii.]  SOAP.  9I5 

Oleic  Acid  Soap  is  obtained  from  crude  oleic  acid,  a  bye-product  of  stearine  candle 
manufacture.  The  oleic  acid  produced  by  the  distillation  process  is  less  suitable  for 
soap-making  purposes.  Oleic  acid  is  saponified  simply  by  being  mixed  with  a  strong 
solution  of  sodium  carbonate,  or  by  the  application  of  caustic  soda.  In  the  use  of  the 
sodium  carbonate,  however,  there  is  the  disadvantage  of  the  effervescence  due  to  the 
evolution  of  carbonic  acid,  and  consequent  boiling  over  or  spilling  of  the  materials. 
Pitman  uses  the  sodium  carbonate  in  a  dry  state.  Heat  is  best  applied  by  Morfit's 
arrangement,  in  which  steam  is  passed  through  a  system  of  pipes  moved  by  machinery 
and  acting  as  stirrers.  Resin  is  sometimes  added.  As  soon  as  the  mass  has  acquired 
sufficient  consistency,  and  the  effervescence  ceases,  the  soap  is  put  into  moulds  to  cool 
and  solidify.  When  caustic  soda  is  used,half  the  lye  (sp.gr.  1-15  to  1-20  =  30-4°  to  4o°Tw.) 
is  first  poured  into  the  cauldron  and  brought  to  ebullition,  next  the  oleic  acid  is  added, 
and  as  soon  as  the  soap-glue  is  formed,  the  other  half  of  the  lye  is  put  in,  and  the 
ebullition  continued  until  the  soap  is  formed.  The  separation  from  the  mother  liquor 
is  greatly  promoted  by  the  addition  of  some  salt.  The  soap  is  poured  into  moulds  to 
cool  and  solidify.  In  order  to  impart  greater  hardness  to  the  soap,  from  5  to  8  per  cent, 
of  tallow  is  added  to  the  oleic  acid.  100  kilos,  of  oleic  acid  yield  from  150  to  160  kilos, 
of  soap,  which,  when  well  made,  consists  of — 

Fat  acids  t        .......        66 

Soila 13 

Water  21 


Resin-Tallow  Soaps.— Colophonium  and  ordinary  fir-tree  resin  combine  at  boiling 
heat  mere  readily  with  alkalies  than  do  fats  and  oils ;  but  the  compounds  obtained  bv 
treating  resin  alone  with  alkalies  are  not  soaps  in  a  chemical  sense,  nor  have  they  the 
appearance  or  properties  of  soap.  When  tallow  is  saponified  along  with  a  portion  of  resin, 
a  true  soap  is  obtained.  In  England  resin-tallow  soap  is  manufactured  very  largely 
by  first  preparing  a  tallow-soap,  and  when  this  is  ready  adding  to  it  from  50  to 
60  per  cent,  of  the  best  resin,  previously  broken  into  small  lumps.  The  mass  is 
thoroughly  stirred,  and  after  the  resin  has  been  incorporated  with  the  tallow,  the 
mother  liquor  or  under-lye  is  run  off,  and  the  soap-making  finished  by  boiling  with  a 
quantity  of  fresh  lye  at  from  i  o°  to  1 3°  Tw.  The  insoluble  alumina  and  iron  soaps  having 
been  removed  as  scum  from  the  top  of  the  liquid,  the  hot  soap  is  poured  into  moulds 
made  of  wood  or  sheet-iron ;  sometimes  palm-oil  is  added  in  order  to  improve  the 
colour  of  the  soap.  Usually,  palm  oil  is  not  saponified  alone,  but  is  added  to  tallow ; 
by  treating  a  mixture  of  2  parts  of  tallow  and  3  parts  of  palm  oil  with  potassa  or 
soda-lye  in  the  ordinary  manner,  and  by  mixing  this  soap  with  a  resin  soap  prepared 
from  i  part  of  resin  and  a  proper  quantity  of  potassa-lye,  the  German  palm-oil  soap  is 
obtained. 

Cocoa-nut  Oil  Soap. — The  manufacture  of  cocoa-nut  oil  soap  resembles  that  of  the 
other  kinds  of  soap.  With  a  weak  lye  cocoa-nut  oil  does  not  form  the  emulsion  common 
to  other  soaps,  but  swims  on  the  surface  as  a  clear  fat ;  when,  by  boiling,  the  lye  has 
reached  a  proper  consistence,  the  oil  suddenly  saponifies.  A  strong  soda-lye  is  used  in 
the  preparation  of  this  kind  of  soap.  Cocoa-nut  oil  in  saponifying  does  not  separate  from 
the  under-lye  ;  therefore  potash-lye  is  never  employed.  To  prevent  the  separation  of  the 
soap  from  the  mixing,  the  quantity  of  caustic-lye  used  must  be  accurately  measured. 
Pure  cocoa-nut  oil  soap  hardens  quickly.  It  is  white,  like  alabaster,  shiny,  soft,  and  easily 
lathered ;  it  has,  however,  a  peculiarly  unpleasant  smell,  which  cannot  be  entirely 
masked  by  any  perfume.  Cocoa-nut  oil  is  seldom  used  alone,  but  usually  as  an  addition 
to  palm  oil  and  tallow.  This  kind  of  soap  can  be  made  without  boiling,  by  merely 
heating  it  to  80°,  by  means  of  steam,  to  melt  the  fats,  a  strong  soda-lye  being  added, 


9i6  CHEMICAL  TECHNOLOGY.  [SECT.  vin. 

and  the  mixture  quickly  stirred.  This  is  known  as  the  "  cold  method,"  and  soap  can 
be  thus  prepared  in  large  quantities  in  a  short  time,  and  is  generally  hard  and  dry. 
When  exposed  to  the  air  for  a  month  or  so,  the  soap  loses  considerably  in  weight,  and 
becomes  effloresced  superficially.  B.  linger  (1869)  prepares  a  soap  in  the  following 
manner :  He  saponifies  palm-oil  with  soda-lye  and  salt  as  usual.  The  product  is 
sodium  palmitate.  At  the  same  time  cocoa-nut  oil  is  saponified  by  means  of  carbonated 
and  caustic  soda-lye ;  this  is  added  to  the  palm-oil  soap,  and  they  are  boiled.  As  a 
rule,  there  are  taken  2  parts  of  palm-oil  to  i  part  of  cocoa-nut  oil ;  and  to  100  parts 
of  the  latter  are  added  i4'3  parts  of  caustic  soda  (Na20)  and  12 '8  parts  of  sodium 
carbonate.  According  to  Unger's  experiments,  this  soap  contains  5  mols.  sodium 
palmitate,  i  mol.  sodium  carbonate,  and  x  mol.  water.  The  "  marbling  "  or  "  mottling  " 
is  effected  in  the  following  manner : — Colouring  matters,  oxide  of  iron,  brown-red, 
Frankfort-black,  are  mixed  with  a  small  portion  of  soap ;  this  is  poured  into  the 
rest  of  the  soap,  with  which  it  forms  layers  of  unequal  thickness.  The  entire  mass  is 
now  stirred,  and  by  this  means  a  marbled  or  grained  appearance  imparted. 

Soft-Soap. — As  before  mentioned,  potash  forms  with  fats  and  oils  only  a  soft-soap, 
which  does  not  dry  when  exposed  to  the  air,  but  on  the  contrary  absorbs  water, 
remaining  constantly  like  a  jelly.  As  a  rule,  these  so-called  soaps  are  impure 
solutions  of  potassium  oleate  in  an  excess  of  potash-lye,  mixed  with  the  glycerine 
separated  in  the  saponification.  Soft-soaps  can  be  prepared  only  with  potash-lyes, 
although  in  practice  i  part  of  soda-lye  is  substituted  for  a  part  of  the  potash  to  assist 
in  somewhat  hardening  the  soap.  There  is  no  separation  of  the  soap  from  the  under- 
lye,  which  contains  all  the  impurities ;  consequently  these  are  disseminated  in  the  soap. 

In  consequence  of  the  solubility  and  cleansing  properties  of  soft-soap,  its  use  is 
preferred  to  that  of  soda-soap  in  the  manufacture  of  cloth  and  woollen  articles.  It 
will  have  been  seen  that  the  difference  in  manufacturing  hard-  and  soft-soaps 
consists  in  employing  potash-lye  for  the  latter,  and  soda  for  the  former.  Wood- ash 
is  not  used  in  preparing  the  potash-lye,  but  always  pure  potash ;  the  preparation 
follows  the  usual  method  with  caustic  lime.  The  fats  used  are  mixtures  of  the 
vegetable  and  animal  oils,  as  the  fish-oil  known  as  "  Southern,"  with  rape,  hemp,  and 
linseed  oils.  The  particular  oil  used  varies  according  to  the  time  of  the  year  and 
market  price :  in  winter  the  soft  oils  are  employed ;  in  summer  the  firmer  oils. 
Soft-soap  is  generally  used  for  fulling  and  scouring ;  but  abroad  it  is  sometimes  used 
for  washing  linen,  to  which  it  imparts  a  most  disagreeable  fishy  odour,  hardly  concealed 
by  any  amount  of  perfume.  The  best  soft-soap  is  made  from  hemp-seed  oil,  this  oil 
imparting  a  green  tinge,  which,  however,  can  be  imitated  by  adding  indigo  to  inferior 
soaps.  Summer  soap,  as  it  is  termed,  contains,  owing  to  the  fat  employed,  more 
potassium  palmitate  in  proportion  to  oleate  than  the  winter  soap.  Sometimes  saponifi- 
cation is  effected  with  a  mixture  of  hemp-  and  palm-oil  or  tallow,  of  train  oil  and 
tallow,  &c, 

The  boiling  of  the  soft-soap  commences  with  a  strong  lye  containing  from  8  to  10 
per  cent,  potash,  by  which  an  emulsion  is  formed.  The  scum  is  dashed  about  with  a 
stick,  the  beating-stick,  and  by  this  means  all  the  alkali  is  taken  up.  A  fresh 
lye  is  then  added,  and  the  boiling  continued,  until  the  soap  upon  cooling  stiffens 
into  a  clear  tough  mass.  When  the  soap  contains  too  much  caustic  alkali,  which 
can  be  ascertained  by  the  taste,  more  oil  is  added.  The  clear-boiling  now  commences, 
during  which  the  excess  of  water  is  removed.  To  avoid  lengthy  evaporation  a 
concentrated  lye  is  employed,  and  the  soap,  instead  of  bubbling  up,  has  its  surface 
covered  with  blisters  as  large  as  the  hand ;  these  blisters  are  termed  leaves.  When 
the  boiling  is  finished — ascertained  by  placing  some  of  the  soap  to  cool  on  a  glass 
plate,  from  which,  if  firm,  it  can  be  separated — the  soap  is  cooled,  and  stored  in 
barrels. 


SECT.    VIII.]  SOAP. 


917 


Soft-soap  will  take  up  a  considerable  quantity  of  water-glass  solution  without 
alteration.  Recently,  for  fulling,  there  has  been  added  to  the  soft-soap  a  solution 
of  potassium  sulphate,  or  a  mixture  of  alum  and  common  salt,  and  also  potato 
starch. 

Various  other  /Soaps. — Another  soap  is  prepared  from  hog's-lard,  and  when 
scented  with  oil  of  almonds  or  essence  of  mirbane  (nitrobenzol)  is  sold  as  almond- 
soap,  and  as  a  cosmetic.  A  soap  is  made  from  the  grease  of  sheep's- wool.  The  so-called 
bone-soap  is  nothing  more  than  a  mixture  of  the  usual  hard  or  cocoa-nut  oil  soap 
with  the  jelly  from  bones.  The  bones  are  first  treated  with  muriatic  acid  to  separate 
the  calcium  phosphate.  A  variety  of  bone-soap  is  the  Liverpool  common  soap. 
Flint-soap  is  an  oil-  or  tallow-soap  with  which  siliceous  earth  is  mixed.  When 
powdered  pumice-stone  is  substituted  for  the  siliceous  earth,  the  soap  is  called  pumice- 
soap.  In  America  as  well  as  in  England  a  water-glass  solution  is  substituted  for  the 
siliceous  earth,  although  according  to  Seeber  the  result  is  not  so  efficacious.  Cocoa- 
nut  oil  soap,  however,  containing  24  per  cent,  of  sodium  silicate  and  50  per  cent,  water,  is 
very  firm.  In  the  United  States  water-glass  is  added  to  the  soap  when,  still  hot  from 
the  boiling-pan,  it  is  poured  into  the  moulds.  The  water-glass  solution  is  of  a  density 
=  60°  Tw.  (=1-31  sp.  gr.) ;  the  proportion  of  soap  is  60  per  cent.  This  kind  of 
water-glass  soap  generally  sets  hard.  Recently  cryolite  and  sodium  aluminate  have 
been  employed. 

Toilet-soaps. — On  account  of  the  reduction  in  the  duty  toilet  soaps  are  now  very 
largely  in  demand.  They  are  generally  made  by  re-melting  and  perfuming  common 
soap.  English  toilet  soap  is  considered  the  best,  as  that  of  France  and  Germany  being 
perfumed  while  cold  is  not  so  uniform  a  product. 

There  are  three  modes  of  preparing  toilet  soap,  viz. : — 

(1)  By  re-melting  raw  soap ; 

(2)  By  the  cold  perfuming  of  odourless  soap ; 

(3)  By  direct  preparation. 

(i)  In  the  method  of  re-melting,  good  raw  soap  is  scraped  into  a  boiling-pan,  and 
after  melting  and  skimming  the  perfume  is  added.  The  soap  is  then  cast  in  moulds 
of  the  required  form.  (2)  In  the  method  of  perfuming  in  the  cold,  odourless  soap  is 
cut  into  fine  shreds  by  a  machine ;  the  perfume  is  then  added,  and  the  soap  is  passed 
between  rollers,  the  sheets  or  bars  thus  formed  being  cut  into  tablets.  Struve,  of 
Leipsic,  has  invented  a  machine  by  means  of  which  soap  is  stamped  into  the  shape 
required.  (3)  The  direct  preparation  of  toilet-soap  consists  in  colouring  and  scenting 
pure  white  common  soap  without  an  intervening  cooling.  The  colouring  materials 
are — for  red,  cinnabar,  coralline,  and  magenta;  the  violet  tar-colours  for  violet;  for 
blue,  ultramarine;  for  brown,  a  solution  of  raw  sugar  or  caramel.  Windsor  soap 
is  prepared  in  the  following  manner: — 40  Ibs.  of  mutton  tallow  and  from  15  to 
20  Ibs.  of  olive  oil  are  mixed  with  soda-lye  marking  19°,  making  a  soap  of  15°; 
finally,  with  lye  marking  20°,  when  the  soap  is  of  the  consistency  of  marrow.  The 
excess  of  lye  is  then  neutralised.  When  the  soap  is  set  it  is  allowed  to  stand  from  six 
to  eight  hours,  and  during  this  time  most  of  the  under-lye  separates.  It  is  then 
placed  in  a  flat  form,  and  pressed  until  no  fluid  exudes.  It  is  scented  with  cumin 
oil,  bergamot,  oil  of  lavender,  oil  of  thyme,  &c.  Rose  soap,  savon  &  la  rose,  is  manu- 
factured by  melting  the  ingredients  of  three  parts  of  oil-soap  with  two  parts  of  tallow- 
soap  and  sometimes  water ;  the  perfume  is  attar  of  roses,  oil  of  roses,  or  gilliflower 
water,  the  colouring-matter  being  generally  cinnabar.  Shaving-soap  must  not  contain 
free  alkalies.  It  is  sometimes  prepared  by  boiling  fat  acids  with  a  mixture  of  potassium 
and  sodium  carbonates.  Lather-soaps  have  in  equal  volume  only  half  the  substance  of 
the  other  soaps.  Palm-  or  olive-oil  soap  is  melted  with  an  addition  of  one-third  to  one- 
ei^hth  the  volume  of  water,  and  the  mass  stirred  until  it  has  increased  to  double  the 


CHEMICAL  TECHNOLOGY.  [SECT.  via. 

volume.  It  is  then  placed  in  a  mould.  It  should  be  remarked  that  the  oil-soaps,  and 
not  tallow-soaps,  are  the  true  formatives  of  the  lather-soaps. 

Transparent  Soap. — Ordinary  dry  tallow-soap  is  cut  into  splinters,  and  heated  with 
an  equal  weight  of  alcohol,  in  which  the  soap  dissolves.  The  mixture  is  allowed  to 
cool ;  therewith  all  impurities  are  thrown  down,  and  the  clear  fluid  is  placed  in  the 
moulds,  where  it  has  to  remain  from  three  to  four  weeks  to  harden.  Tincture  of  cochineal 
and  aniline  red  are  employed  for  colouring  transparent  soaps,  and  also  Martius's  yellow. 
The  perfume  is  chiefly  oil  of  cinnamon,  sometimes  oil  of  thyme,  oil  of  marjoram,  and 
sassafras  oil.  Glycerine-soap  is  prepared  from  an  alcoholic  solution  of  ordinary  soap, 
to  which  glycerine  is  added.  Or  5  cwts.  of  soap  with  an  equal  quantity  of  glycerine 
are  heated  by  steam  in  a  copper  vessel.  The  mixture  is  placed  in  moulds,  and 
allowed  to  set  in  the  usual  manner.  A  solution  of  soap  in  an  excess  of  glycerine 
(35  :  3°)  forms  fluid  glycerine-soap,  which  is  of  a  clear  honey  consistency.  Both 
varieties  are  perfumed  with  essential  oils. 

Uses  of  Soap. — Soap  is  used  for  cleansing  purposes  in  washing,  in  bleaching  cloth 
and  woollen  materials ;  for  the  preparation  of  lithographic  inks,  &c.  The  cleansing 
properties  of  soap  are  due  to  the  alkalies  it  contains.  The  alkali,  although  combined 
with  the  fat  acids,  loses  none  of  these  properties,  which  are,  in  fact,  included  in  the 
combination  of  the  alkali  with  the  fatty  substances  of  the  dirt  to  be  removed.  The 
explanation  of  the  action  chemically,  according  to  Chevreul,  is  the  following : — The 
neutral  salts  formed  by  the  alkalies  and  the  fat  acids,  stearates,  palmitates,  and  oleates 
are  decomposed  by  the  water,  whereby  insoluble  double  fat  acid  salts  are  separated, 
while  the  alkali  is  set  free.  By  means  of  the  free  alkali  the  impurities  clinging  to  the 
materials  are  removed,  and  taken  up  by  the  fat  acid  salts,  the  suspended  dirt  being  thus 
contained  in  the  lather.* 

Soap  Tests. — The  greater  the  quantity  of  fat  acids  combined  in  the  soap,  the 
higher  is  its  value.  A  normal  soap,  besides  alkaline  fat  acids,  should  only  contain 
free  water,  the  quantity  of  which  gives  a  means  of  estimating  the  value  of  the  soap. 
It  is  in  the  power  of  the  soap-maker  to  manufacture  300  parts  of  a  good  hard  soap 
out  of  100  parts  of  fat.  When  too  small  a  quantity  of  water  is  contained  the  soap 
becomes  too  hard,  and  much  labour  is  lost  in  obtaining  a  lather.  If,  on  the  other 
hand,  water  is  held  in  too  large  a  quantity  there  is  a  great  loss  of  material.  The 
degree  of  hardness  of  the  soap  forms,  therefore,  another  means  of  estimating  its  value. 
Many  soaps  contain  2  to  3  per  cent,  glycerine.  But  the  proportion  of  water  and  the 
hardness  of  a  soap  are  not  the  only  means  of  estimation,  there  still  remains  the 
estimation  of  the  neutral  fat,  acid,  alkalies,  the  free  alkali,  common  salt,  or  unsaponified 
fat  in  the  residue  left  after  the  drying  of  the  soap.  According  to  W.  Stein,  the 
presence  of  free  alkali  may  be  ascertained  by  means  of  calomel,  or  according  to 
Naschold,  by  mercurous  nitrate.  Uncombined  fat  retards  the  formation  of  a  lather, 
and  after  a  time  imparts  to  the  soap  a  rancid  odour.  But  the  worth  of  a  soap  can 
only  be  accurately  ascertained  by  means  of  chemical  analysis. 

The  table  by  Dr.  Leeds  (p.  919)  gives  a  method  for  the  examination  of  soaps. 

Insoluble  Soaps. — All  soaps  which  have  not  a  base  of  potassa  or  soda  are  insoluble 
in  water.  Calcium-soap  plays  an  important  part  in  the  manufacture  of  stearine 
candles.  It  is  obtained  either  by  saponifying  fat  with  calcium  hydrate  or  by 
decomposing  a  soluble  soap  with  a  soluble  salt  of  lime.  It  is  constantly  formed  if  we 
attempt  to  dissolve  soap  in  hard  water.  Magnesium-soap  is  not  readily  formed  in  a 
direct  manner,  but  it  may  be  formed  indirectly  by  dissolving  common  soap  in  sea 
water.  Aluminium-soap  is  one  of  the  most  important  of  the  insoluble  soaps. 
Alumina  does  not  saponify  fats,  but  alumyiium-soap  is  obtained  by  means  of  a  sodium 

*  Soaps  used  for  cleansing  wool  and  woollen  goods  should  always  have  a  basis  of  potash,  to 
the  exclusion  of  soda. — [EDITOR.] 


SECT.    VIII.] 


SOAP. 


919 


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920  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

or  potassium  aluminate.  Jarry  proposes  to  protect  wood  from  moisture  by  saturation 
with  aluminium  oleate.  Textile  goods  are  often  rendered  waterproof  by  successive 
treatment  with  aluminium  acetate  and  soap-lye,  a  process  which  results  in  the  forma- 
tion of  an  aluminous  soap.  In  raising  the  colours  of  tissues  mordanted  with  aluminium 
salts  and  afterwards  dyed  or  printed  with  a  solution  of  soap,  there  is  formed  aluminium 
oleate  which  is  sometimes  used  as  a  size  in  the  manufacture  of  paper.  Lieber  recom- 
mends aluminium  palmitate. 

Manganese-soap  is  obtained  by  decomposing  manganese  sulphate  with  common  soap 
or  by  dissolving  manganese  carbonate  in  oleic  acid.  It  is  used  as  a  siccative. 

Zinc-soap,  formed  by  double  decomposition  or  by  saponifying  zinc  oxide  with  olive 
oil  with  the  aid  of  heat,  is  a  yellowish- white  mass.  If  obtained  by  the  first  method  it 
quickly  dries  to  a  friable  mass  ;  if  produced  by  the  second  method  it  has  the  con- 
sistence of  a  plaster.  Zinc-soap  is  also  formed  when  zinc  white  is  used  as  an  oil 
colour.  Lead-soap  may  be  formed  by  double  decomposition  or  by  saponifying  litharge 
or  white-lead  with  olive  oil.  It  is  a  yellowish-white  mass  and  is  present  in  lead 
varnishes.  Tin-soap  formed  by  double  decomposition  is  produced  when  tissues  are 
raised  by  soaping  after  being  mordanted  with  salts  of  tin.  Copper-soap,  obtained  by 
double  decomposition  is  a  green,  dry  mass  which  becomes  brittle.  It  is  sparingly 
soluble  in  alcohol,  more  readily  in  ether  or  oils,  and  it  can  also  be  prepared  by  boiling 
copper  carbonate  in  oleic  acid.  A  mixed  copper  and  iron  soap,  obtained  by  precipitating 
with  soap  a  mixed  solution  of  copper  and  iron,  if  ground  up  with  litharge  varnish  and 
wax,  serves  to  produce  a  permanent  green  bronze  on  plaster  figures. 

Mercury  or  quicksilver  soap  is  prepared  from  mercuric  chloride  and  soap ;  it  is 
white,  but  turns  grey  on  exposure  to  air  and  light.  Silver,  gold,  and  platinum  soaps 
are  severally  prepared  by  double  decomposition,  but  they  are  of  little  use.  Gold  soap  is 
employed  in  gilding  porcelain,  and  silver  soap  for  darkening  the  hair. 

Washing  Powders,  Extracts  of  Soap,  Soap  Powders,  Washing  Sugars,  Soap  Ash,  Sapona- 
ceous, &c.,  are  mixtures  used  both  in  manufactures  and  for  domestic  purposes.  They 
vary  greatly  in  their  composition  and  their  value.  One  of  the  commonest  kinds  is 
made  by  allowing  soda  crystals  to  melt  in  their  own  water  of  crystallisation,  often  with 
the  addition  of  a  small  quantity  of  water  to  compensate  for  that  which  escapes  during 
the  process.  Some  palm  oil,  ground  yellow  resin,  or  ordinary  soap,  is  incorporated  with 
the  mixture,  and  the  whole  is  then  poured  out  into  large,  shallow  trays  of  sheet  iron, 
in  which  it  is  diligently  stirred  during  cooling,  so  that  it  solidifies  not  into  crystals  or 
coherent  masses,  but  into  a  rough  powder,  having  the  appearance  of  coarse  sugar.  The 
supposed  advantage  of  these  preparations  is  that  they  dissolve  more  readily  than  soap 
and  soda  crystals.  Some  varieties  are  coloured  with  a  little  turmeric,  and  others  with 
artificial  ultramarine. 

In  the  lower  qualities,  a  considerable  quantity  of  sodium  sulphate  (Glauber's  salt) 
is  melted  down  along  with  the  soda  crystals.  It  cannot  be  detected  by  the  appearance 
of  the  sample. 

Soap-pastes,  or  washing-pastes,  consist  of  soda-lyo  with  which  farinaceous  matter 
has  been  incorporated. — [EDITOR.] 

Adulteration  of  Soaps. — In  the  manufacture  of  soap  integrity  is  nearly  beaten  out 
of  the  market.  The  principal  adulterant  is  water,  which,  by  various  artifices,  is  incor- 
porated with  the  soap  to  an  alarming  extent.  (See  p.  913.)  The  other  adulterants 
are  silica,  alumina,  water-glass,  or  talc.  Caustic  alkali,  though  a  necessary  ingredient 
of  the  soap,  becomes  hurtful  if  present  in  excess,  or  if  it  has  not  been  duly  saponified. 
Unsaponified  fats  may  also  prove  injurious  in  certain  manufacturing  processes. — 
[EDITOR.] 

The  reader  may  compare  "  The  Art  of  Soap-making,"  by  Alexander  Watt.  London  •  Crosby 
Lockwood  &  Son.  "A  Treatise  on  the  Manufacture  of  Soap  and  Candles,"  by  W.  L.  Carpenter. 


SECT.  VIII  ] 


STEARINE  AND  GLYCERINE. 


921 


London  :  C.  &  F.  N.  Spon.  "  Soap  and  Candles,"  by  R.  S.  Cristiani,  Philadelphia  and  London. 
"  Manufacture  of  Soap,"  by  fl.  Dussance,  Philadelphia  and  London.  "  Soaps,"  by  C.  Morfit,  New 
York. — [EDITOR.] 

STEAEINE  AND  GLYCERINE. 

The  preparation  of  the  fatty  acids  can  be  effected  by  saponification  with  lime, 
with  sulphuric  acid,  with  water  and  high  pressure,  and  with  superheated  steam  and 
subsequent  distillation. 

Saponification  with  Caustic  Lime. — The  fat  used  is  tallow  (beef  or  mutton)  or  palm 
oil.  Mutton  tallow  contains  large  quantities  of  solid  fatty  acids  and  is  easier  to  work, 
but  beef  tallow  is  cheaper.  The  tallow  imported  from  Russia  is  generally  a  mixture  of 
beef  and  mutton  tallow.  Since  palm-oil  has  been  introduced  in  quantity  and  at  a  low 
price,  it  is  used  in  many  manufactories  of  stearine  candles. 

The  fat  is  first  melted  in  wooden  vats  lined  with  lead,  the  charge  being  500  kilos, 
of  tallow  and  800  litres  of  water,  heated  by  steam  through  a  pipe,  the  end  of  which 
lies  on  the  bottom,  coiled  in  a  spiral.  After  the  fat  is  melted  there  are  gradually  added 
with  constant  stirring,  600  litres  milk  of  lime,  containing  70  kilos,  of  burnt  lime 
( =  14  per  cent,  of  the  weight  of  the  fat).  After  heating  for  from  six  to  eight  hours  the 
formation  of  the  lime-soap  is  completed.  From  the  hard  crumbly  lime-soap  the 
yellowish  glycerine  water  (at  5*50°  to  8-25°  Tw.)  u  drawn  off  and  worked  up  by  concen- 
tration and  distillation.  According  to  theory,  on  the  assumption  that  in  neutral  fats 
i  mol.  glycerine  exists,  combined  with  3  mols.  fatty  acid,  only  87  quick-lime  should  be 
required  to  100  parts  of  fat.  Still  14  per  cent,  were  used  at  first,  as  it  was  found  that 
an  excess  facilitates  saponification,  though  it  subsequently  occasions  a  corresponding 
increase  in  the  outlay  for  sulphuric  acid. 

The  lime-soap  is  now  decomposed  by  means  of  sulphuric 
acid,  of  which  137  kilos,  are  used  to  500  kilos,  fat  and  70  kilos. 
lime.  The  sulphuric  acid  is  diluted  with  water  to  17°  Tw. 
(containing  in  this  state  30  per  cent.  HaS04)  placed  in  a 
decomposition-vat  along  with  the  lime-soap,  heated  by  the  intro- 
duction of  steam  and  stirred  for  three  hours.  After  the  fatty 
acids  are  separated,  the  steam  is  shut  off  and  the  liquid  is  allowed 
to  settle.  The  fatty  acids  collect  on  the  surface  and  a  great 
part  of  the  calcium  sulphate  subsides  to  the  bottom.  The  fatty 
acids  are  run  off  or  skimmed  off  into  a  vat  lined  with  lead,  and 
in  order  to  remove  the  residues  of  lime  and  gypsum  they  are 
washed  first  with  dilute  sulphuric  acid  of  1*089  sp.  gr.  under  the 
action  of  steam  and  then  with  water.  500  kilos,  tallow  yield 
from  460  to  488  kilos,  of  fatty  acids,  or  74  per  cent.  The  yield 
depends  on  the  kind,  the  purity,  and  the  treatment  of  the 
tallow.  100  parts  of  the  fatty  acids  yielded  from  43*3  to  48^4 
parts  of  solid  fatty  acid,  in  the  mean  45-9  part  of  a  mixture  of 
stearic  and  palmitic  acid. 

After  the  fatty  acids  have  been  freed  as  completely  as  pos- 
sible from  lime,  gypsum,  and  sulphuric  acid  by  repeated  wash- 
ings with  water,  they  are  kept  for  some  time  in  a  state  of 
fusion  to  let  the  last  traces  of  water  escape.  They  are  then  allowed  to  congeal  or 
crystallise,  and  the  part  which  has  not  solidified — consisting  chiefly  of  oleic  acid — is 
pressed  either  in  hydraulic  presses  or  filter-presses,  first  in  the  cold  and  then  in  heat. 
The  congelation  is  effected  in  moulds  of  tin  plate,  which,  like  chocolate  moulds,  are 
wider  at  the  edge  than  at  the  bottom  and  hold  about  2  kilos,  of  fatty  acid. 

The  moulds  are  filled  as  follows : — The  melted  acids  are  conveyed  by  means  of  a 


Fig.  583- 


922 


CHEMICAL   TECHNOLOGY. 


[SECT.  viu. 


pump  and  the  pipe,  B,  into  a  wooden  funnel,  A,  which  is  placed  over  the  entire 
length  of  a  wooden  scaffold  on  which  the  moulds  are  set  above  each  other  as  shown  in 
Fig.  583.  Each  mould  has  a  spout  at  its  upper  edge ;  the  fat  then  flows  down  through 
the  spout  into  the  next  mould,  and  so  on  until  all  the  moulds  are  filled.  The  supply 
is  then  cut  off  by  closing  the  leaden  spouts,  J'7— through  which  the  fat  flows  out  of  the 
funnel  into  the  highest  mould — by  means  of  wooden  plugs.  The  fatty  acids  are  left 
in  the  moulds  to  crystallise  slowly,  which  requires  twelve  hours  in  winter,  but  twenty- 
four  in  summer.  The  slower  the  crystallisation  and  the  better  the  crystals  are 
developed  the  more  easily  and  completely  the  liquid  portions  may  be  removed  by 
expression. 

According  to  A.  Kind  the  cooling  should  be  effected  slowly  and  as  it  may  be 
required  in  order  to  obtain  a  well-crystallised  mass.  By  sudden  cooling  there  is 
obtained  a  mass  from  which  the  solid  fatty  acids  can  only  be 
separated  with  difficulty.  The  cylinder  used,  a  (Figs.  584  and  585), 
is  turned  smooth  within  ;  it  is  closed  at  both  ends  by  the  covers 
b  and  c,  and  is  provided  externally  with  ribs,  n,  set  against  each 
other  which  when  the  cylinder,  a,  is  introduced  into  an  exterior 
cylinder,  w,  coated  with  a  non-conductive  mass,  join  up  to  the 
corresponding  ribs  of  the  latter.  There  is  thus  formed  a  cooling- 
room  serving  for  the  admission  of  cold  water  and  alternately 

Fig-  585- 


Fig.  584. 


rS^wZ^M^ 


Explanation  of  Term. 
Kiihlwasser Water  for  refrigeration. 

interrupted  by  partitions  above  and  below,  so  that  the  cold  water  entering  below  at  e 
is  compelled  to  pass  up  and  down  round  the  cylinder  in  the  direction  of  the  arrow, 
finally  leaving  the  apparatus  of  the  pipe,  f.  For  the  oleine  to  be  refrigerated  there  is 
in  the  cylinder,  a,  a  narrow,  annular  space  formed  by  the  cylinder,  v,  placed  con- 
centrically to  a,  and  set  in  slow  movement  with  its  axle,  h.  Around  its  circumference 
there  are  placed  ribs  which,  as  the  axle  revolves,  brush  slightly  against  the  inside  of 
the  cylinder,  a.  These  ribs  may  either  be  straight  or  have  the  form  of  a  rapid  screw 
thread.  The  oleine  entering  through  the  pipe,  o,  into  the  cover,  b,  is,  on  turning  the 
axle,  h,  moved  slowly  in  the  opposite  direction  to  the  cooling  water  and  is  forced 
though  the  tube,  t,  to  a  store-tank. 

Another  apparatus  for  continuous  working  has  been  devised  by  Messener. 

Petit  uses  a  drum,  A  (Fig.  586),  consisting  of  two  cast-iron  plates,  which  are  held 
together  by  bolts  and  kept  between  two  cylindrical  sheet  iron  walls.  Within  the 
drum  is  cold  water  coming  from  a  refrigerating  machine  which  flows  through  the  pipe, 
C)  and  a  hollow  arm,  D,  to  the  drum,  and  flows  away  through  another  arm.  The  drum 


.SECT.   VIII.] 


STEARINE   AND  GLYCERINE. 


923 


is  moved  by  means  of  a  circle  of  teeth  from  a  shaft,  E ;  this  shaft  drives  a  pump,  P, 

by  means  of  an  eccentric.     The  pump  sucks  the  congealed  mass  out  of  the  receiver,  F, 

and  forces  it  to  the  filter-press.     The  external 

jacket  of  the  drum  as  it  revolves  takes  up  a 

thin    layer   of   liquid   from   the   trough,  f,  to 

which  the  oleine  flows   through   the  cock,  g  ; 

as  the  drum  revolves  this  film  of  liquid  congeals 

and   is  finally  stripped  off  at  h  by  a  scraper, 

and  falls  into  the   recipient,  F,  which  is  also 

cooled  by  cold  water.     Hence  the  mass  arrives 

at  a  Farinaux  filter-press. 

The  separation  of  the  solid  and  the  liquid 
fatty  acids  is  effected  by  cold  pressing  followed 
by  hot  pressing.  For  the  former  the  moulds 
are  thrown  upon  the  press-cloth,  a  coarse, 
sack-like  tissue  of  especially  strong  tough  wool ; 
the  yellowish-brown  cakes  of  fat  are  emptied 
into  it,  the  press-sacks  then  filled  are  arranged 
between  iron  and  zinc  plates  upon  the  table  of 
a  common  hydraulic  press  and  submitted  to  a  pressure  of  200,000  kilos.  The  oleic 
acid  flowing  off  is  received  in  collecting  funnels  placed  below  the  table.  It  is  used 
in  the  soap  manufacture,  for  greasing  wool,  and  recently  as  oleic  ether  mixed 
with  clay  forming  an  excellent  oil  for  rendering  leather  supple.  When  the  cold 
press  no  longer  yields  any  oleic  acid,  hot  pressing  follows.  Fig.  587  shows  the 

Fig.  587- 


most  important  parts  of  a  horizontal  hot  press,  in  which  the  press-bags  and  the 
intermediate  plates  are  upright  for  the  better  escape  of  the  oleic  acid.  The  water 
used  for  pressing  arrives  through  the  pipe,  R,  into  the  press-cylinder,  C,  in  which  it 
acts  upon  the  great  piston,  jT,  which  presses  the  bags  on  the  horizontal  tables.  The 
«akes  of  fat  from  the  cold  press  are  broken  up,  placed  in  horsehair  bags  (called  in 


924  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

French  works  etreindilles)  and  interstratified  with  the  press-plates.  These  plates  are 
of  cast-iron  and  made  hollow,  so  that  they  may  be  heated  by  the  introduction  of  steam 
which  arrives  by  the  pipe,  V,  and  the  flexible  tubes,  a.  In  using  the  press  the  plates, 
P,  and  the  sacks  are  arranged  alternately  and  as  soon  as  the  table  is  full  the  steam- 
pipe,  V,  is  opened  to  heat  the  plates.  The  access  of  steam  is  so  regulated  that  the 
temperature  first  rises  to  70°,  then  falls  so  low  that  it  does  not  reach  the  melting- 
points  of  palmitic  and  stearic  acid,  but  keeps  the  oleic  acid  liquid  enough  to  flow  off 
with  ease.  For  this  purpose  a  temperature  of  40°,  or  even  of  35°,  is  most  suitable. 
At  the  same  time  the  piston  of  the  press  is  allowed  to  act.  When  oleic  acid  no- 
longer  flows  off,  the  hard,  solid  fatty  mass  is  taken  out.  It  is  contaminated  with  a 
little  organic  matter  and  ferric  oxide  only  at  the  places  where  it  has  come  in  contact 
with  the  apparatus,  and  it  is  exposed  to  the  light  for  some  days.  It  is  next,  at  some 
works,  sorted  into  three  or  four  qualities,  according  to  its  degree  of  purity.  Besides  the 
oleic  acid  obtained  on  hot  pressing  there  crystallise  out  on  cooling  not  inconsiderable 
quantities  of  palmitic  acid,  which  is  added  in  the  next  operation  to  the  mixture  of 
liquid  and  solid  fatty  acids.  According  to  Girard  there  is  sometimes  placed  over  the 
press-cylinder,  C,  a  manometer,  M,  connected  with  an  electric  signal  apparatus  which 
shows  the  workmen  when  the  required  pressure  has  been  reached.  Latterly  the  filter- 
press  is  coming  more  and  more  into  use  in  the  stearine  industry. 

The  various  sorts  of  solid,  fatty  acids  obtained  by  hot  pressure  are  next  refined. 
To  effect  this  the  acids  are  melted  by  steam  in  very  dilute  sulphuric  acid  (475°  Tw.)  in 
•washing  becks  lined  with  lead.  This  process  is  then  repeated  two  or  three  times  until 
all  the  sulphuric  acid  is  washed  away.  It  is  then  kept  for  some  time  in  a  state  of 
fusion,  to  eliminate  traces  of  water,  and  is  finally  poured  into  moulds.  The  washing; 
water  must  be  quite  free  from  lime ;  if  this  is  not  the  case  the  lime  must  be  precipi- 
tated by  oxalic  or  stearic  acid.  The  fatty  acid  obtained  is  cast  in  tin  moulds  and 
supplied  to  candle-makers  in  the  state  of  flat  cakes. 

Saponlfication  with  a  Reduced  Proportion  of  Lime  and  the  Use  of  High  Pressure. — 
Milly  observed  that  the  quantity  of  lime  required  for  saponification  could  be  reduced 
from  14  per  cent,  of  the  weight  of  the  tallow,  not  merely  to  8,  but  to  4  or  even  to 
2  per  cent.,  if  the  mixture  of  lime  water  and  fat  is  exposed  to  a  higher  temperature 
than  has  been  customary. 

He  placed  in  a  closed  boiler  2300  kilos,  of  tallow  and  20  hektolitres  of  lime  milk, 
containing  50  kilos,  of  lime  (2  per  cent.),  or  69  kilos.  ( =  3  per  cent.),  and  caused 
steam  of  182°  (=  a  pressure  of  10  atmospheres),  to  act  upon  the  mixture  so  that  the 
temperature  within  the  boiler  was  172°.  After  seven  hours  the  saponification  was 
complete.  In  the  boiler  there  was  a  watery  solution  of  glycerine  and  a  mass  of  fatty 
acids,  among  which  were  distributed  small  quantities  of  lime-soap.  The  boiler  was 
emptied  and  charged  again,  so  that  6900  kiios.  of  tallow  could  be  worked  up  in 
twenty-four  hours.  This  procedure  is  advantageous,  as  the  quantity  of  sulphuric 
acid  required  to  decompose  the  lime-soap  is  much  reduced.  The  Milly  process  is 
introduced  in  the  great  candle-works  at  Vienna,  in  the  "  Apollo  candle-works " 
on  the  Schottenfelde  in  Vienna  and  Penzing,  in  Sarg's  works  at  Liesing,  and  in  those 
of  Himmelbaur  at  Stockerau.  Sarg,  of  Liesing,  saponifies  with  3  per  cent,  lime 
and  a  pressure  of  10  atmospheres,  obtaining  95  per  cent,  fatty  acids,  and  30  per  cent, 
glycerine  water  at  from  6*75  to  8-25°  Tw.  The  fatty  acids  after  cold  and  hot  pressure  yield 
25  percent,  stearic  acid  and  35  per  cent.  "  returns" — i.e.,  fatty  acids — which  are  pressed 
along  with  the  total  yield,  which  is  finally  45  per  cent,  stearic  acid  and  50  per  cent,  oleic- 
acid.  The  glycerine  water  is  evaporated  and  after  repeated  distillation  yields  5  to  6  per 
cent,  glycerine. 

The  apparatus  constructed  by  Leon  Droux,  fitted  with  an  agitator  for  saponifying 
fats  under  pressure,  deserves  notice.  (Fig.  588.)  The  cylinder  is  of  copper,  an  1  is. 


SECT.    VIII.]' 


STEARINE   AND   GLYCERINE. 


925 


generally  8  metres  in  length  by  1-05  to  no  in  diameter,  the  shaft  fixed  in  the  longitu- 
dinal axis  of  the  cylinder  is  50  mm.  in  diameter,  and  is  fitted  with  copper  arms  for 
stirring ;  it  revolves  thirty  times  in  the  minute.  For  saponifying  3000  kilos,  of  fat 
there  are  used  80  kilos,  of  lime.  The  yield  is  2800  kilos,  fatty  acids  and  240  kilos, 
glycerine  at  46°  T\v.  The  increase  of  weight  is  due  to  the  water  taken  up  in  the 
formation  of  glycerine.  After  the  saponification  is  completed  the  contents  of  the  boiler 
are  run  into  a  settling  beck.  The  glycerine  water  obtained  has  the  sp.  gr.  of  7°  Tw. 
The  decomposition  of  the  lime-soap  by  sulphuric  acid  is  made  easier  by  its  fluid  state. 
The  new  apparatus  has  also  been  adopted  in  works  where  the  distillation  process  is 
applied.  In  the  latter  the  saponification  with  sulphuric  acid  is  discarded  and  the  fatty 
acid  obtained  is  saponified  in  Droux's  apparatus  with  slight  acidification.  Latterly  its 
shape  has  been  made  globular  instead  of  cylindrical.  The  axle  of  the  agitator  is 
horizontal ;  the  apparatus  is  heated  by  direct  steam  distributer.  Below,  at  the  side  of 
the  apparatus  are  two  trial-cocks,  and  above  these  is  a  man-hole  for  charging  the 
apparatus.  Each  operation  takes  six  or  seven  hours  and  the  apparatus  is  kept  for 

Fig.  588. 


five  or  six  hours  at  a  pressure  of  7  or  8  atmospheres.  When  the  process  is  at  an 
end  the  contents  of  the  tube  are  run  off  through  a  pipe  opening  into  the  apparatus 
below,  by  simply  turning  a  cock.  The  product  is  then  treated  in  the  manner  already 
described.  The  advantages  of  this  new  construction  are  said  to  be  the  greater  strength 
of  the  globular  vessels,  the  shortening  the  shaft  and  the  decrease  of  condensation  by 
surface  cooling,  as  a  globe  has  the  largest  capacity  with  the  smallest  surface. 

In  explaining  this  kind  of  saponification  Payen  holds  that  lime  in  its  action  upon 
tristearine,  tripalmitine,  and  trioleine  gives  the  impulse  to  a  molecular  movement 
which  is  completed  by  the  water  at  a  temperature  of  172°.  Pelouze  had  observed  that 
lime-soap,  obtained  by  precipitating  an  aqueous  solution  of  calcium  chloride  with  an  aque- 
ous solution  of  common  soap  with  an  equal  quantity  of  water  and  then  put  in  a  digester 
with  olive  oil,  saponifies  the  oil,  at  a  temperature  of  from  155°  to  165°,  setting  glycerine 
at  liberty.  From  this  and  from  other  experiments  he  concluded  that  in  Milly's  saponi- 
fication with  a  small  percentage  of  lime,  the  process  consists  of  several  stages  in  which 
there  is  first  formed  a  basic  or  neutral  soap  which  is  finally  converted  into  an  acid  soap. 
But  if  we  consider  that  Milly  in  his  saponification  with  2  per  cent,  of  lime  employs 
a  temperature  of  182°  (corresponding  to  a  pressure  of  10  atmospheres),  and  that  Wright 
and  Fouche  effected  an  almost  complete  decomposition  of  the  fats  at  the  same  tempera- 
ture with  water  alone  and  that  Cloez  effected  a  complete  saponification  of  the  fats  at 
200°  with  water,  it  seems  simplest  to  assume  that  in  this  case  water  is  the  decomposing 


926  CHEMICAL  TECHNOLOGY.  [SECT.  vra. 

element,  and  that  the  presence  of  2  per  cent,  lime  merely  promotes  and  simplifies  the- 
saponification  by  cancelling  a  counter-affinity.  The  same  result  is  attained  still  better 
by  a  small  quantity  of  alkali. 

Saponification  by  Means  of  Sulphuric  Acid  and  Subsequent  Distillation  by  Means- 
of  Steam. — It  was  known  to  Achard,  in  the  year  1777,  that  the  neutral  fats  are 
decomposed  by  concentrated  sulphuric  acid  in  a  manner  similar  to  the  decomposition 
effected  by  caustic  alkalies.  This  fact  was  again  brought  for  ward  in  1821  by  Caventon,. 
and  in  1824  by  Chevreul,  but  was  not  scientifically  investigated  until  1836  by  Fremy, 
and  not  industrially  applied  until  the  year  1841,  when  Dubrunfaut  introduced  the 
distillation  of  the  fatty  acids  on  the  large  scale.  The  crude  fatty  matter  usually 
submitted  to  this  process  of  saponification  is  of  the  kind  that  cannot  be  saponified  by 
the  lime  process  by  reason  of  its  impurities ;  thus,  for  instance,  palm  and  cocoa-nut  oil, 
bone  and  marrow  fat,  fat  of  slaughter-houses,  kitchen-stuff,  the  products  of  the 
decomposition,  by  means  of  sulphuric  acid,  of  the  soap- water  obtained  from  wool- 
spinning  and  cloth-making  works,  residues -of  the  refining  of  fish  and  other  oils,  residues 
of  tallow-melting,  &c. 

This  process  of  saponification  by  means  of  sulphuric  acid  as  carried  on  in  the  large 
establishment  for  stearine  candle-making  of  Leroy  and  Durand,  at  Gentilly,  near  Paris, 
consists  of  three  operations,  viz. : — 

(a)  Saponification  with  sulphuric  acid  ; 

(/3)  Decomposition  of  the  products  of  saponification  ; 

(•y)  Distillation  of  the  fatty  acids. 

(a)  In  order  to  eliminate  the  greatest  impurities  first,  the  crude  fatty  matters  are 
molten  and  kept  in  the  liquid  state  for  some  time,  so  that  the  coarser  impurities  may 
subside.  The  fatty  matters  are  then  transferred  to  a  kind  of  boiler  made  of  iron  boiler- 
plates lined  inside  with  lead,  and  fitted  with  a  stirring  apparatus  and  a  steam-jacket, 
connected  by  means  of  pipes  with  a  steam-boiler,  so  that  the  apparatus  may  be  heated. 
Into  this  vessel  sulphuric  acid  at  153*4°  Tw.  =  r8  sp.  gr.  is  poured,  the  quantity  of  this 
fluid  being  regulated  according  to  the  nature  of  the  fatty  matters  operated  upon. 
Kitchen-stuff,  fat  from  slaughter-houses,  and  the  like  require  12  per  cent,  of  their 
weight  of  acid  ;  palm  oil  requires  from  6  to  9  per  cent,  according  to  quality.  The  fatty 
substances  having  been  put  into  the  vessel,  the  stirring  apparatus  is  set  in  motion,  and 
the  steam  turned  on  for  the  purpose  of  supplying  heat  to  the  vessel.  The  temperature 
to  which  the  vessel  is  heated  varies,  being  177°  in  Price's  Works,  Battersea,  while  at 
Gentilly  the  heat  is  seldom  higher  than  from  110°  to  115°.  During  the  operation  the 
mass  foams,  becomes  brown,  and  evolves  sulphurous  acid,  partly  due  to  the  action  of  a 
portion  of  the  concentrated  sulphuric  acid  upon  the  glycerine,  partly  to  its  action  upon 
the  impurities  present  among  the  fatty  matters.  The  neutral  fat  is  converted  into  a 
mixture  of  sulpho-fatty  acids  and  sulpho-glyceric  acid.  The  saponification  is  complete 
after  some  fifteen  to  twenty  hours'  application  of  heat.  According  to  De  Milly's  new 
process  (1867)  the  tallow  is  heated  to  120°,  along  with  6  per  cent,  of  sulphuric  acid, 
and  the  action  of  the  latter  is  limited  to  two  or  three  minutes ;  it  is  thereby  possible  to 
obtain  80  per  cent,  of  the  solid  fatty  acids  in  a  condition  at  once  fit  for  making  candles 
without  re-distillation,  only  20  per  cent,  having  to  be  distilled. 

(|3)  Decomposition  of  the  products  of  the  sulphuric  acid  saponification.  The  mass  is 
left  to  cool  for  three  or  four  hours  and  is  next  transferred  to  large  wooden  tanks  lined 
with  lead,  and  previously  one-third  filled  with  water.  At  the  bottom  of  these  tanks 
steam  pipes  are  fitted,  by  means  of  which  the  fluid  contents  of  the  vessel  are  soon 
heated  to  100°.  The  sulphuric  acid  and  the  fatty  acids  are  dissociated,  and  these 
bodies,  partly  combined  with  a  larger  quantity  of  hydrogen  and  oxygen  than  was 
present  in  the  fatty  acids  from  which  they  were  formed,  partly  also  in  an  unaltered 
condition,  are  found  floating  on  the  surface.  After  having  been  repeatedly  triturated 


SECT.    VIII.] 


STEARINE   AND   GLYCERINE. 


927 


with  boiling  water,  the  fatty  acids  are  tapped  or  poured  over  into  a  vessel  filled  with 
water  heated  to  from  40°  to  50°,  for  the  purpose  of  allowing  the  impurities  to  become 
deposited.  The  clarified  fatty  acids  are  next  heated  in  a  vessel  placed  on  an  open  fire 
in  order  to  evaporate  all  the  water,  after  which  they  are  submitted  to  distillation. 

(y)  The  distillation  requires  several  precautions.  Distillation  with  an  open  fire 
would  convert  the  fatty  acids  into  oil,  gas-tar,  and  a  carbonaceous  residue,  if  the  heat 
were  sufficiently  high.  But  when  the  temperature  is  properly  regulated,  the  fatty 
acids  are  protected  from  the  direct  action  of  the  fire.  Air  should  be  completely  excluded 
from  the  distilling  apparatus.  With  these  precautions  the  fatty  acids  distil  over  with- 
out undergoing  any  essential  alteration.  These  conditions  are  complied  with  by  the  use 
of  superheated  steam  at  a  temperature  of  from  250°  to  350°.  The  fatty  acids  are  placed 
in  a  capacious  retort  with  which  there  is  connected  on  the  one  hand  a  pipe  for  admit- 
ting the  superheated  steam,  and  on  the  other  an  ordinary  condenser.  Fig.  589  shows 


Fig.  589. 


the  arrangement  of  the  distilling  apparatus,  the  flame  plays  round  the  spiral  coils  and 
escapes  through  the  chimney,  C.  The  spiral  begins  at  M,  passes  through  the  fire-box, 
comes  out  in  front  at  T,  enters  again  at  T',  and  opens  at  last  into  the  retort,  T".  The 
latter,  which  projects  out  of  the  fire  is  of  copper  or  cast-iron ;  from  the  upper  part  of 
this  retort  there  passes  the  tube,  U,  which  is  continued  as  an  iron  cooling-worm  lying 
in  an  iron  tank  full  of  water.  This  pipe  conveys  the  fatty  acids  into  the  receiver, 
K,  whilst  the  gaseous  products  escape  through  the  tube,  Kr  When  the  apparatus  is  to 
be  set  in  action,  the  spiral  is  first  heated  and  the  retort,  Z>,  is  run  three-quarters  full 
of  the  melted  fat  through  the  pipe,  V ;  steam  is  turned  in  at  300°.  The  air  is  then 
completely  expelled  and  distillation  soon  begins  in  consequence  of  the  high  temperature, 
which  does  not  fall  below  200°  in  the  retort.  The  fatty  acids  collecting  in  the  receiver, 
K,  are  not  identical  at  all  times  of  the  distillation. 

When  the  several  fatty  acids  are  fractionally  collected  from  the  beginning  to  the 
end  of  the  distillation  their  melting  points  are : — 


From  Palm  Oil. 

ist  product  .  .  54'5° 

2nd  .  .  52 'o 

3rd  .  .  48x3 

4th  .  .  46-0 

5th  .  .  44 'o 

6th  .  .  41 'O 

7th  .  .  39-5 


From  Kitchen-stuff 

and  Bone  Fat. 

44-0° 

41-0 

41'0 

42-5 
44-0 

45  •o 
41-0 


028 


CHEMICAL  TECHNOLOGY. 


[SECT.  viii. 


The  water  condensed  with  the  fatty  acids  runs  off  from  the  receiver  through  a  tap. 
At  the  beginning  of  the  operation  the  water  constitutes  half  the  produce ;  towards  the 
end  only  about  one-third.  With  a  retort  capable  of  containing  1000  to  noo  kilos,  of 
material  the  distillation  takes  some  twelve  hours.  The  end  of  the  operation  is  indicated 
by  the  coming  over  of  coloured  products.  There  remains  in  the  retort  a  black  tarry  matter 
the  quantity  of  which  amounts  in  the  case  of  palm-oil  distillation  to  from  2  to  5  per  cent., 
and  for  kitchen-stuff  to  from  5  to  7  per  cent.  This  residue  is  not  removed  after  each 
distillation  but  left  in  the  retort  until  it  has  accumulated  to  such  an  extent  as  to  render 
its  removal  necessary.  The  first  products  of  the  distillation  of  palm  oil  saponified  by 
means  of  fatty  acids  are  so  solid,  that  by  pressure  they  do  not  yield  any  fluid  acid,  and 
are  at  once  fit  for  the  manufacture  of  candles.  The  products  which  come  over  after- 
wards are  further  purified  by  hydraulic  pressure,  re-melting,  and  washing  with  water. 
The  substance  obtained  by  pressure,  more  or  less  pure  oleic  acid,  is  only  used  for 
soap-making  in  this  country,  although  abroad  it  is  burnt  in  some  kind  of  lamps.  The 
oleic  acid  obtained  by  this  process  is  essentially  different  from  that  obtained  by  the 
lime  saponification  process.  The  quantities  of  fatty  acids  obtained  by  this  process  of 
saponification  are  the  following  : — 


from  suint        .... 
„      olive  oil  residues. 
„      palm  oil  . 

„      fat  from  slaughter-houses 
oleic  acid 


47  to  55  Per  cent. 
47  to  50        ,, 
75  to  80        „ 
60  to  66        „ 
25  to  30        „ 


The  boiler  recommended  by  Julian  and  Blumsky  for  distilling  fatty  acids  has  two 
domes,  B  (Figs.  590  and  591),  connected  with  corresponding  coolers.     The  two  end 

plates  give  exit  to  a  num- 

Fig.  590.  Fij-.  591.         ber  of  tubes,  Z>,  connected 

by  intermediate  pieces. 
The  steam  which  has  been 
superheated  in  an  especial 
arrangement  enters 
through  the  pipe,  E,  passes 
through  the  tubes,  D  and 
d,  and  the  two  tubes,  e, 
connected  with  the  sieve- 
tubes,  n,  into  the  liquid. 
The  mixture  of  fatty  acids 
is  filled  in  through  the 
man-hole,  C,  to  the 
height  of  the  cock,  /.  The  apparatus  is  then  heated  until  drops  appear  at  the 
cooling-tubes ;  the  cock  F  is  closed,  G  is  opened,  and  superheated  steam  is  allowed  to 
enter  through  E.  It  passes  through  the  pipe,  Z>,  and  escapes  at  the  cock,  G.  In  this 
manner  the  entrance  of  steam-water  into  the  boiler  is  avoided,  which  would  interfere 
with  the  distillation.  As  soon  as  the  temperature  of  the  charge  has  risen  so  high  thai 
no  more  liquefaction  takes  place  at  Z>,  and  the  steam  in  consequence  escapes  tolerably 
dry,  the  cock  F  is  gradually  opened  to  allow  the  dry  steam  to  pass  through  the  tube,  e, 
to  the  sieve-tubes,  n.  The  cock  G  is  then  closed  and  Nthe  distillation  is  continued  b) 
the  double  action  of  the  superheater-tubes,  Z>,  and  the  sieve-tubes,  n,  until  the  distillate 
appears  coloured,  when  the  operation  is  stopped.  Two  hours  after  the  distillation  is  at 
an  end  the  residues  may  be  let  off  through  the  cock  H  into  a  closed  receiver ;  but  if 
they  are  to  be  collected  in  an  open  cistern  from  five  to  six  hours  should  elapse  after  the 
conclusion  of  the  distillation. 


SECT,  viii.]  STEABINE  AND  GLYCERINE.  929 

Zinc  chloride,  which  in  many  respects  (see  p.  460)  is  similar  in  its  action  to 
sulphuric  acid,  has  been  proposed  as  a  substitute  for  the  latter.  For  countries  into 
which  sulphuric  acid  has  to  be  imported  zinc  chloride  might  be  of  greater  advantage, 
being  capable  of  recovery  and  less  dangerous  and  difficult  in  transport.  When, 
according  to  the  researches  of  L.  Kraft  and  Tessie  du  Motay,  a  neutral  fat  is  heated 
with  anhydrous  zinc  chloride,  a  complete  incorporation  of  these  substances  takes 
place  between  150°  and  200°;  and  by  continuing  the  heating  for  some  time,  and 
washing  the  materials  with  warm  water,  or  better  with  water  acidulated  with  hydro- 
chloric acid,  there  is  obtained  a  fatty  matter,  which,  on  being  submitted  to  distillation, 
yields  the  corresponding  fatty  acid,  while  only  a  small  quantity  of  acroleine  is  formed. 
The  zinc  chloride,  becoming  soluble  in  the  water  used  for  washing,  may  be  recovered 
by  evaporating  the  fluid.  The  yield  of  fatty  acids  by  this  process  is  the  same  as  that 
obtained  by  the  use  of  sulphuric  acid,  while  the  fatty  acids  also  agree  as  to  their  physical 
properties.  The  quantity  of  zinc  chloride  required  amounts  to  from  8  to  1  2  per  cent. 
of  the  fat. 

Saponification  with  Water  and  High  Pressure.  —  Some  sixteen  years  ago  another 
agent,  capable  of  bringing  about,  in  a  manner  similar  to  alkalies  and  acids,  the  disso- 
ciation of  fatty  matters  into  glycerine  and  fatty  acids,  was  introduced,  this  agent  being 
simply  superheated  steam  at  high  pressure  :  — 

+  3H.O  =  ° 


Tripalmitine.  Water.        Glycerine.        Palmitic  acid. 

The  idea  of  submitting  fatty  matters  to  a  similar  method  of  treatment  is  not  a 
new  one,  for  in  the  researches  of  Appert  (1823)  and  Manicler  (1826)  some  hints  are 
given  on  the  decomposition  of  fats  by  means  of  superheated  water  ;  but  the  aim  of 
these  technologists  was  different,  for  in  their  experiments  they  employed  steam  to 
separate  the  tallow  from  the  cellular  tissue  it  is  contained  in,  and  for  that  purpose  a 
temperature  of  from  1  15°  to  121°  was  quite  sufficient,  while  at  a  temperature  of  180°  and 
a  pressure  of  from  10  to  15  atmospheres  (=150  Ibs.  to  225  Ibs.  pressure  to  the  square 
inch)  water  can  exert  a  far  more  energetic  action  upon  the  neutral  fats,  dissociating  them 
and  thus  setting  free  their  constituents.  The  knowledge  of  this  interesting  fact  is  due 
to  the  researches  of  Tilghman  and  Berthelot,  who  almost  simultaneously  made  this 
discovery  in  the  year  1854,  while  shortly  after  Melsens,  at  Brussels,  obtained  the  same 
result.  As  regards  the  industrial  application  of  this  discovery,  Tilghman  and  Melsens 
made  further  researches  ;  their  modes  of  operating  are  very  similar. 

Tilghman  adds  to  the  neutral  fat  about  to  be  decomposed  one-third  to  one-half  of 
its  bulk  of  water,  and  pours  this  mixture  into  a  sufficiently  strong  vessel  in  which  the 
fluids  can  be  submitted  to  the  action  of  a  temperature  nearly  as  high  as  the 
melting-point  of  lead,  320°.  This  vessel  is  so  arranged  that  during  the  operation  it 
can  be  closed  so  as  to  prevent  on  the  one  hand  the  evaporation  of  water,  and,  on  the 
other,  admit  of  a  sufficiently  strong  pressure.  The  process  is  carried  on  continuously  by 
causing  the  fluids  to  circulate  through  a  tube  heated  to  the  required  temperature. 
Melsens  uses  a  Papin's  digester,  in  which  the  fat  to  be  decomposed  is  heated  to  180°  to 
200°,  with  from  10  to  20  per  cent,  water,  to  which  from  i  to  10  per  cent,  of  sulphuric  acid 
has  been  added.  Wright's  and  Fouche's  apparatus  consists  of  two  hermetically  closed 
copper  vessels  placed  one  above  the  other  and  connected  together  by  means  of  two 
tubes,  one  of  which  reaches  nearly  to  the  bottom  of  the  lower  vessel,  and  ends  in  the 
upper  one  just  above  the  bottom. 

The  apparatus  of  Tilghman,  shown  in  section  in  Fig.  592,  consists  of  a  boiler,  A,  in 
which  the  fat  —  previously  freed  from  impurities  —  is  brought  in  contact  with  hot  water, 
and  is  thus  converted  into  a  kind  of  emulsion.  The  piston,  B  perforated  like  a  sieve, 


93° 


CHEMICAL  TECHNOLOGY. 


vni. 


which  is  moved  quickly  up  and  down  in  the  vessel,  A,  effects  an  intimate  mixture  of 
the  fat  and  the  water.  The  forcing  pump,  C,  drives  the  mixture  through  a  long 
wrought-iron  tube,  D,  which,  as  it  appears  in  the  figure,  makes  several  bends  in  the 
furnace,  E,  and  is  heated  by  the  fire,  F,  up  to  the  melting  point  of  lead.  On  issuing 
from  the  heating-tubes  the  mixture,  the  fat  of  which  has  been  already  split  up  into 
glycerine  and  fatty  acids,  passes  through  the  worm,  G,  in  which  its  temperature  is 
reduced  to  100°.  It  then  escapes  through //"and  falls  into  a  suitable  receiver.  The 
valve  placed  at  If  is  loaded  in  such  a  manner  that  when  the  heating-tubes  have  the 
proper  temperature  and  the  forcing-pump  is  not  in  action,  it  cannot  be  opened  by  the 
pressure  within ;  consequently  when  the  pump  drives  nothing  into  the  apparatus, 
nothing  can  escape  from  it,  if  the  temperature  is  not  too  high.  When  the  forcing 
pump  is  at  work  and  drives  the  mixture  through  the  apparatus,  the  valve,  ff,  opens  and 

a  corresponding  quan- 

FiS-  592.  tity  Of   tne   mixture 

escapes  at  G.  The 
hot  mixture  of  fatty 
acid  and  solution  of 
glycerine  is  sepai-ated 
by  settling,  the  fatty 
acid  is  washed  with 
water,  the  solution  of 
glycerine  is  concen- 
trated and  purified 
in  the  usual  manner. 
A  treatment  for  ten 
minutes  is  generally 
sufficient  for  the  com- 
plete decomposition 
of  the  fats.  A  simi- 
lar apparatus  has 
been  designed  by 
Hugues. 

The  process  of  Melsens  consists  in  treating  the  fat  in  a  Papin  digester  at  from  180° 
to  200°,  with  from  10  to  20  per  cent,  of  water,  to  which  from  i  to  10  per  cent,  of 
sulphuric  acid  has  been  added.  The  apparatus  is  a  long  horizontal  boiler,  in  which 
the  mixture  of  the  water  and  the  fat  is  effected  in  a  small,  second  kettle,  which  is  placed 
in  connection  with  the  former,  filled  with  steam,  which  is  then  allowed  to  escape  into 
the  air,  and  the  rest  is  condensed.  The  vacuum  formed  in  the  small  boiler  draws,  on 
opening  a  cock,  water  and  fat  from  the  large,  lower  boiler.  If  a  connection  is  then 
again  effected  between  the  upper  parts  of  both  boilers,  the  liquid  mixture  is  violently 
forced  into  the  lower  boiler. 

According  to  Marix  the  decomposition  of  fats  by  water  can  be  effected  at  pressures 
of  from  3  to  5  atmos.,  if  a  little  magnesium  carbonate  and  chalk  are  added. 
Violette  and  Buisine  have  recourse  to  ammonia. 

Manufacture  of  Fatty  Acids  by  Means  of  Superheated  Steam  and  Subsequent 
Distillation. — Allied  to  the  process  just  described  is  the  operation  carried  on  by  the 
well-known  Price's  Candle  Company.  Limited,  at  -Battersea.  Gay-Lussac  and 
Dubrunfaut  had  already  tried  to  apply  to  industrial  purposes  the  fact  that  neutral 
fats  are  dissociated  by  distillation,  yielding  fatty  acids  ;  but  notwithstanding  that  these 
savants  employed  steam,  the  results  obtained  did  not  answer  the  expectation,  because  a 
portion  of  the  fatty  matter  was  decomposed,  yielding  acroleine  and  leaving  a 
carbonaceous  residue.  Wilson  and  G\vynne  were  more  successful  with  their  experi- 


SECT.    VIII.  I 


STEARINE   AND   GLYCERINE. 


merits,  and  by  using  a  distilling  apparatus  similar  to  that  described  on  p.  503,  they 
obtained  by  means  of  superheated  steam  the  complete  dissociation  of  the  neutral  fats 
into  fatty  acids  and  glycerine;  while  by  closely  watching  and  regulating  the  tem- 
perature, they  could  not  only  completely  saponify  the  neutral  fats,  but  also  distil  the 
fatty  acids  and  glycerine  over  without  undergoing  any  decomposition. 

The  retorts  have  a  cubic  capacity  of  60  hectolitres,  and  are  heated  by  direct  fire  to 
a  temperature  of  from  290°  to  315°.  A  malleable  iron  steam-pipe  conveys  steani  at  a 
temperature  of  315°  into  the  molten  fatty  matter.  The  admission  of  steam  is  con- 
tinued for  from  twenty-four  to  thirty-six  hours  according  to  the  kind  of  fat.  The 
.saponification  proceeds  regularly  and  the  products  distil  over  and  are  collected  at  the 
lower  aperture  of  the  cooling  apparatus.  The  fatty  acids  are  at  once  fit  for  candle- 
making  purposes,  while  the  glycerine  is  purified  by  a  subsequent  distillation  with 
steam.  As  already  mentioned,  the  proper  temperature  has  to  be  scrupulously  main- 
tained, for  if  the  temperature  falls  below  310°,  the  saponification  proceeds  very  slowly  ; 
but  if  the  temperature  rises  much  above  that  degree,  a  portion  of  the  fatty  substance 
is  decomposed  and  acroleine  is  formed  in  large  quantity. 

H.  Heckel  describes  a  simple  apparatus  for  the  purpose. 

According  to  Korschelt  the  decomposition  is  much  facilitated  if  the  fat  is  finely 
divided  before  exposure  to  the  steam.  The  fat  is  heated  for  this  purpose  in  a  receiver, 
A  (Figs.  593  and  594),  to  100°  and  passes  thence  into  a  wrought-iron  pipe,  a,  with 


Fig-  593- 


Fig.  594- 


many  curves  which  lies  in  the  metal  bath,  B.  The  latter  consists  of  a  strong  iron 
vessel  in  which  lead  and  an  alloy  of  lead  and  tin  (preferably  an  alloy  melting  at  290° 
of  100  parts  lead  with  6  or  7  tin)  is  kept  in  a  molten  state.  The  oil  issues  from  thij 
bath  at  about  300°  and  arrives  in  the  tower,  C,  in  which  the  decomposition  is  effected. 
The  tower  is  built  of  cast-iron  plates  surrounded  with  masonry,  but  with  an  isulating 
stratum  of  air  between,  and  is  filled  with  balls  of  burnt  clay,  &c.,  lying  on  gratings,  e. 
The  hot  oil  is  forced  upwards  through  a  pipe,  a,  which  ascends  in  the  middle  of  the 
tower  and  flows  through  the  descending  end  of  this  tube  upon  a  distributor,  n. 
From  this  the  oil  pours  over  the  clay  balls  and  flows  down  among  them,  coming 
thereby  in  intimate  contact  with  superheated  steam  introduced  into  the  tower  through 
the  pipe,  c,  and  rising  upwards.  The  glycerides  are  thus  split  up  into  free  fatty  acids 
and  glycerine,  and  these  products  of  decomposition  pass  along  with  the  steam  through 
exit  tube,  d,  to  a  suitable  refrigerator.  Into  the  tube,  c,  conveying  the  superheated 
steam  a  box,  /,  is  inserted  in  which  are  fixed  two  or  more  tubes,  g,  open  above  and 


932 


CHEMICAL  TECHNOLOGY. 


[SECT.  viii. 


closed  below  ;  one  of  these  is  filled  with  lead  (melting  point  334°) ;  the  second  with  an 
alloy  of  100  parts  lead  with  6  parts  tin  (melting  point  289°)  and  a  third  with  zinc 
(melting-point  412°),  so  that  the  observation  of  these  tubes  renders  it  possible  to 
estimate  the  temperature  of  the  steam  entering  the  tower.  A  similar  arrangement,  h, 
is  introduced  into  the  oil-pipe,  a.  The  inflow  of  the  oil  is  so  regulated  that  little  or 
none  arrives  at  the  bottom  of  the  tower  undecomposed.  The  oil  which  collects  there  is 
conveyed  away  by  the  pipe,  i,  passes  through  the  worm,  s,  into  the  condenser,  m,  and 
runs  away  into  a  receiver.  If  fats  are  used  which  are  solid  at  common  temperatures 
a  little  steam  is  allowed  to  enter  through  the  tube,  i,  or  the  condensing  water  is  raised 
to  the  required  temperature  in  some  other  way. 

For  some  years  the  process  proposed  by  Bock  has  been  in  use  for  the  saponification 
of  fats.  He  treats  the  fat  with  sulphuric  acid  at  a  moderate  temperature  and  without 
distillation.  By  this  treatment  the  albuminous  membranes  in  which  the  fat  globules 
are  enclosed  and  which  make  up  i-o  to  1*5  per  cent,  of  the  fat  are  destroyed  and  the 
fat  may  be  decomposed  by  simply  boiling  with  water  in  open  vessels.  According  to 
Birnbaum  the  mixture  of  fatty  acids  thus  obtained  contains  99^53  per  cent,  fatty  acid 
without  a  trace  of  glycerine.  Hartl,  of  Vienna,  carries  out  this  process  in  an  im- 
proved form. 

Conversion  of  Okie  Acid  into  Palmitic  Acid. — Tallow  generally  yields  about  50  per 
cent,  of  oleic  acid  which  scarcely  fetches  half  the  price  of  the  solid  acids.  The  con- 
version of  oleic  acid  into  solid  palmitic  acid  which  was  formerly  carried  out  by  Cramer 
and  then  on  the  large  scale  by  Radisson,  of  Marseilles,  is  based  upon  the  reaction — 
discovered  in  1841  by  Varrentrapp — of  an  excess  of  caustic  potassa  upon  oleic  acid, 
the  latter  being  split  up  into  palmitic  acid,  acetic  acid  and  hydrogen  according  to 
the  equation,  C12H34O2  +  2KOH  =  C16H31K02  +  C2H3K02  +  H2. 

On  the  large  scale  the  re-action  is  effected  in  cast-iron  cylinders  with  covers  of 
sheet-iron,  three  metres  in  diameter  (Fig.  595).  Into  these  are  pumped  about  1-5  ton 
of  oleic  acid  and  2^5  ton  potassa  lye  of  80°  Tw.,  and  heated  by  a  fire  placed  at  such  a 

distance  as  to  prevent  overheating.  The  steam  given 
off  at  first  escapes  through  the  man-hole  m  in  the 
cover.  When  the  soap  becomes  dry  the  man-hole  is 
covered  and  the  escaping  gases  are  conveyed  through 
the  pipe  z  to  the  condensing  tower  and  then  to  a 
gas-holder.  The  temperature  of  the  mass  is  slowly 
raised  to  290°.  An  agitator  keeps  the  mixture  in 
constant  movement.  At  290°  the  escape  of  hydrogen 
begins  after  the  soap  is  melted.  When  the  tempera- 
ture reaches  320°  the  escaping  gases  have  a  peculiar 
smell.  The  operation  must  then  be  at  once  ended, 
as  otherwise  decomposition  would  ensue.  Steam  and 
water  are  therefore  let  into  the  cylinder,  and  at  the 
same  time  a  trap  at  the  bottom  is  opened  through 

which  the  potassium  palmitate  falls  into  water,  where  it  is  boiled  by  means  of  steam 
with  a  certain  quantity  of  water.  On  settling,  the  product  separates  into  two  layers, 
the  upper  of  neutral  potassium  palmitate,  and  the  lower  of  potassa-lye  at  about  27°  Tw. 
Potassium  palmitate  is  decomposed  by  sulphuric  acid  in  another  vessel,  yielding  a  pale- 
brown  palmitic  acid  which  on  cooling  forms  large  tabular  crystals.  After  crystallisation 
it  is  perfectly  white,  burns  with  a  luminous  smokeless  flame,  and  is  equal  to  the  best 
quality  of  stearic  acid.  If  mixed  with  common  stearic  acid  it  loses  the  tendency  to 
crystallise  and  has  a  translucency  which  is  much  esteemed  in  the  candle  trade.  An 
attempt  has  been  made  to  decompose  the  palmitate  by  boiling  with  milk  of  lime  in 
order  to  recover  the  potassa.  But  it  is  necessary  to  work  with  a  solution  at  8'5°  Tw., 
and  the  expense  of  concentration  to  80°  T\v.  is  far  from  insignificant. 


Fig.  595- 


SECT,  vin.]  STEARINE  AND   GLYCERINE.  933 

By  this  process  oleic  acids  from  the  most  different  sources  may  be  converted  into 
solid  acids  excepting  that  from  mare's  fat  and  from  the  suint  of  wool.  Oleic  acid  pre- 
pared by  Bock's  process  gave  the  best  yield— i.e.,  94  to  95  per  cent,  palmitic  acid.  The 
cost  of  the  conversion  amounts  at  Marseilles  to  31-15  francs  for  100  kilos,  of  white 
palmitic  acid. 

The  substition  of  soda  for  potassa  in  this  process  presented  at  first  some  difficulties, 
since  sodium  oleate  is  relatively  difficultly  fusible  and  is  a  bad  conductor  of  heat,  so  that 
a  uniform  temperature  of  the  melted  salt  could  not  be  obtained  even  by  the  use  of  an 
agitator.  Radisson  found,  however,  that  this  defect  might  be  removed  by  adding  a  cer- 
tain quantity  of  paraffine  to  the  mixture  of  soda-lye  and  oleic  acid.  The  paraffine  effects 
a  perfect  liquefaction  of  the  mass  and  prevents  the  sodium  palmitate  from  being  heated 
above  its  decomposition  point.  The  small  quantity  of  paraffine  volatilised  in  the  opera- 
tion is  received  in  a  condenser.  The  escaping  hydrogen  is  so  rich  in  hydrocarbon  that 
it  is  a  good  gas  for  lighting.  After  the  end  of  the  operation  the  mass  is  treated  with 
water  as  usual  and  separates  into  three  layers,  paraffine  at  the  top,  sodium  palmitate  in 
the  middle,  and  soda-lye,  containing  some  sodium  acetate,  at  the  bottom.  The  paraffine 
and  the  soda-lye  are  used  for  succeeding  operations,  whilst  the  sodium  palmitate  is 
decomposed  by  sulphuric  acid.  The  conversion  is  so  complete  that  the  loss  does  not 
exceed  i  per  cent. 

C  H  (OH\ 

Glycerine.— Glycerine,  C3H803  (a  triatomic  alcohol,      H5}03,  or  C3H5JOHJ,      is 

present  in  the  shape  of  glycerides  in  combination  with  solid  and  fluid  fatty  acid  to  an 
amount  of  8  to  9  per  cent.,  and  may  be  separated  by  treatment  with  bases  (potash, 
soda,  lime,  baryta,  lead  oxide),  or  with  acids  (sulphuric  acid),  and  certain  chlorides 
(e.g.,  zinc),  also  by  means  of  superheated  steam,  or  very  hot  water  without  the  formation 
of  steam,  in  closed  vessels.  Glycerine  is  also  formed  as  a  constant  product  by  the 
alcoholic  fermentation  of  dextrose,  levulose,  and  lactose.  According  to  Pasteur's 
researches,  the  quantity  of  glycerine  thus  formed  amounts  to  about  3  per  cent,  of 
the  weight  of  the  sugar.  Glycerine  was  first  discovered  by  Scheele  whilst  engaged  in 
preparing  lead  plaster.  Industrially,  glycerine  has  been  used  for  only  twenty-five 
years,  in  consequence  of  the  large  quantity  of  glycerine  now  obtained  as  a  bye-product  in 
the  manufacture  of  soap  as  well  as  of  stearine  candles.  The  vinasse  of  the  potato, 
and  molasses  from  beet-root  sugar  distillation,  and  likewise  the  residue  of  the  distilla- 
tion of  wine,  vinasse  proper,  as  carried  on  in  the  South  of  France,  contain  large 
quantities  of  glycerine. 

As  regards  the  preparation  of  glycerine  on  the  large  scale,  it  is  mainly  a  question 
of  purification  of  the  glycerine  obtained  in  the  industrial  preparation  of  the  stearic 
acid  from  neutral  fats  above  described.  When  the  lime  saponification  process  is  used, 
the  glycerine  remains  dissolved  in  the  water  after  the  separation  of  the  insoluble  lime- 
soap.  The  dissolved  lime  having  been  eliminated  by  either  sulphuric  or  preferably 
oxalic  acid,  the  evaporation  of  the  liquid  to  the  consistency  of  a  syrup  will  yield  a 
glycerine  pure  enough  for  many  technical  purposes.  When  the  decomposition,  or  rather 
dissociation,  of  the  neutral  fats  is  effected  by  means  of  superheated  steam,  the  glycerine 
and  fatty  acids  are  both  obtained  in  a  pure  state,  provided  the  heat  be  kept 
at  or  below  310°,  because  otherwise  a  portion  of  the  glycerine  is  decomposed  «vith 
evolution  of  vapours  of  acroleine.  The  fact  that,  when  fats  are  saponified  with  sul- 
phuric acid,  the  sulphoglyceric  acid  in  aqueous  solution  yields  readily  by  evaporar.ior 
glycerine  and  sulphuric  acid,  may  be  applied  for  the  preparation  of  glycerine.  The 
soapboiler's  mother  liquor,  now  the  most  important  source  of  crude  glycerine,  may  be 
made  available  for  its  production,  according  to  Reynold's  patent,  in  the  following 
manner : — The  mother  liquor  is  first  concentrated  by  evaporation ;  the  saline  matter 
which  is  thereby  gradually  separated  being  removed  from  time  to  time.  When  the 


934  CHEMICAL   TECHNOLOGY.  [SECT,  vin 

fluid  is  sufficiently  concentrated — ascertained  by  the  boiling  point  having  risen  to- 
il 6° — it  is  transferred  to  a  still,  and  the  glycerine  distilled  off  by  means  of  superheated 
steam  carried  into  the  still.  The  distillate  is  next  concentrated  and  brought  to  the 
consistency  of  a  syrup  in  a  vacuum  pan. 

The  boiling-point  of  glycerine  is  290°.  The  glycerine,  freed  from  colouring  matters, 
if  necessary  by  means  of  animal  charcoal,  cannot  be  brought  to  the  necessary  concen- 
tration in  open  vessels  without  becoming  coloured.  It  is  therefore  allowed  to  flow  into  a 
vacuum  pan,  in  which  it  is  concentrated  in  the  absence  of  air.  Frequently,  however,  a 
re-heating  with  animal  charcoal  and  a  filtration  are  needed.  Dynamite  works  require 
a  glycerine  free  from  chlorine  ;  for  this  purpose  it  is  purified  with  silver  nitrate. 

The  distillation  of  glycerine  for  its  purification,  as  indicated  by  Wilson  and  Payne 
in  1855,  forms  a  great  advance  in  the  manufacture. 

The  glycerine,  after  being  entirely,  or  almost  entirely,  freed  from  fatty  acids,  is 
distilled  with  superheated  steam  in  the  absence  of  air,  when  the  steam  also  serves  tO' 
expel  volatile  impurities.  A  current  of  steam  at  from  100°  to  110°  is  then  passed  for 
several  hours,  by  means  of  a  perforated  tube,  through  glycerine,  which  has  been  pre- 
viously brought  at  the  lowest  possible  temperature  to  sp.  gr.  1*15,  until  the  products 
passing  over  have  no  longer  an  acid  reaction.  It  is  then  heated  (while  still  introducing 
superheated  steam)  to  from  170°  to  180°,  but  not  above  200°.  If  necessary,  it  may  be- 
rectified  in  the  same  manner.  It  is  important  that  glycerine  should  be  separated  from  the 
accompanying  water  by  fractionated  refrigeration,  to  a  degree  sufficient  for  all  technical 
purposes.  By  distillation  with  heated  steam  there  is  obtained,  not  an  aqueous  solution 
of  glycerine,  but,  if  the  vapours  are  passed  into  a  series  of  refrigerators  surrounded 
with  bad  conductors  of  heat,  in  the  first,  a  glycerine  which  is  nearly  anhydrous,  in  the 
following,  water,  containing  little  glycerine,  and  in  the  last,  water  which  has  scarcely 
a  sweet  taste.  These  liquids  are  used  for  diluting  glycerine  which  is  to  be  refined 

Pure  glycerine  has  the  sp.  gr.  i-2653  ;  it  takes  fire  if  heated  to  150°,  and  burns 
with  a  blue,  faintly  luminous  flame ;  it  burns  also  with  a  wick.  The  freezing  of 
glycerine  was  observed  by  W.  Crookes,  of  London,  in  1867,  by  Sarg,  of  Vienna,  and 
by  Woehler,  of  Gottingen. 

Among  the  many  applications  of  glycerine  are  the  following  : — For  keeping  clay 
moist  for  modelling  purposes ;  for  preventing  mustard  from  drying  up ;  for  keeping 
snuff  damp  ;  preserving  fruit ;  sweetening  liqueurs ;  and  for  the  same  purpose  for 
wine,  beer,  and  malt  extracts.  Glycerine  is  also  useful  as  a  lubricating  material  for 
some  kinds  of  machinery,  more  especially  watch  and  chronometer  works,  because  it  is 
not  altered  by  contact  with  air,  does  not  become  thick  at  a  low  temperature,  and  does 
not  attack  such  metals  as  copper,  brass,  &c.  Glycerine  is  used  in  the  making  of  copy- 
ing inks,  and  of  a  great  many  cosmetics.  In  order  to  render  printing  ink  soluble  in 
water — its  insolubility  is,  however,  its  greatest  advantage — it  has  been  proposed  to  use 
glycerine  for  its  preparation  instead  of  linseed  oil.  Glycerine  is  an  excellent  solvent 
for  many  substances,  including  the  tar-colours  (aniline  blue,  cyanine,  aniline  violet)  and 
alizarine.*  In  order  to  render  paper  soft  and  pliable  glycerine  is  added  to  the  pulp. 
To  the  quantity  of  pulp  required  for  making  100  kilos,  of  dry  paper,  5  kilos,  of  glyce- 
rine, sp.  gr.  i*i8,  are  sufficient.  It  is  not  out  of  place  here  to  mention  the  following 
useful  weavers'  glue  or  dressing,  composed  of — Dextrine,  5  parts  ;  glycerine,  1 2  parts ; 
ammonium  sulphate,  i  part;  and  water,  30  parts.  By  the  use  of  this  mixture 
the  weaving  of  muslins  need  not  be — as  was  formerly  the  case — carried  on  in  damp, 
darkened  cellars,  but  may  be  performed  in  well- aired  and  well-lighted  rooms.  It  is 
said  that  leather  driving-belts,  made  as  usual  of  weakly  tanned  leather,  when  kept  in 

*  In  dyeing  with  colouring  matters  of  great  tinctorial  power,  such  as  many  coal-tar  colours, 
glycerine  is  an  excellent  addition  to  the  dye-beck.  It  prevents  "  flurry,"  i.e.,  the  formation  of  a 
coloured  froth  or  scum  on  the  surface,  which  is  a  frequent  cause  of  unevenness. — [EoiTOK.] 


SECT,  viii.]  ESSENTIAL  OILS  AND  RESINS.  935 

glycerine  for  twenty-four  hours,  are  not  so  liable  to  fray.  A  glycerine  solution  is  now 
largely  used  instead  of  water  for  the  purpose  of  tilling  gas-meters,  as  such  a  solution 
does  not  freeze  in  winter  nor  evaporate  in  summer.  Santi  uses  glycerine  for  the  com- 
passes on  board  screw-steamers,  in  order  to  protect  the  inner  compass-box  against  the 
vibrations  caused  by  the  motion  of  the  propeller.  It  is  impossible  to  enter  here 
into  minute  details  on  the  use  of  glycerine.  Suffice  it  to  observe  further,  that  it  is 
employed  for  preserving  anatomical  preparations,  for  rendering  wooden  casks  imper- 
vious to  petroleum  and  other  oils ;  for  the  preparation  of  artificial  oil  of  mustard  or 
sulpho-cyan-allyl,  made  by  treating  glycerine  with  phosphorus  iodide,  whereby  allyl 
iodide  is  formed,  which  on  being  dissolved  in  alcohol,  and  next  distilled  with  potas- 
sium sulphocyanide,  yields  sulpho-cyan-allyl.  When  glycerine  is  treated  with  very  con- 
centrated nitric  acid  or  with  a  mixture  of  strong  sulphuric  and  nitric  acids,  it  is  converted 
into  nitro-glycerine  (trinitrine  or  glyceral  nitrate)  (see  p.  393),  largely  used  for  various 
purposes,  the  preparation  of  clualine  and  dynamite,  &c.  A  mixture  of  finely  powdered 
litharge  and  very  concentrated  glycerine,  made  into  a  paste,  forms  a  rapidly  hardening 
cement,  especially  useful  as  a  cover  for  the  corks  or  bungs  of  vessels  containing  such 
fluids  as  benzol,  essential  oils,  benzoline,  petroleum,  &c.,  the  cement  being  impermeable 
to  these  liquids. 

When  used  for  sweetening  wines  or  liqueurs,  it  is  sold  under  the  incorrect  name 
of  saccharine,  and  its  application  is  known  as  "  scheelising." 

ESSENTIAL  OILS  AND  KESINS. 

These  substances  almost  all  occur  naturally.  To  the  essential  oils  most  plants 
owe  their  odour  and  flowers  their  perfume.  The  essential  oil  in  plants  is  met  with 
enclosed  in  cells;  hence,  after  bruising  a  plant,  or  the  parts  containing  the 
essential  oil,  the  peculiar  odour  is  more  perceptible;  for  instance,  by  gently  rub- 
bing between  the  fingers  the  leaves  of  some  kinds  of  geraniums,  melissa,  lemon 
plant,  &c.  Essential  oils  do  not  impart  to  the  fingers  a  fatty,  but  a  rather  rough, 
harsh  feeling.  A  large  number  of  essential  oils  possess  the  property  of  precipitating 
silver  from  its  ammoniacal  solution  in  a  metallic  state  ;  hence  the  use  of  essential  oils 
in  silvering  glass  (see  p.  614). 

Preparation  of  Essential  Oils. — These  oils  are  chiefly  obtained  by  submitting  parts 
of  plants,  previously  ground  to  a  coarse  powder,  to  distillation  with  water.  Although 
the  boiling  point  of  these  oils  is  generally  much  higher  than  that  of  water,  the  oils  are 
mechanically  carried  over  in  a  minute  state  of  division  with  the  aqueous  vapour.  When 
oils  the  boiling  point  of  which  is  very  high,  have  to  be  extracted,  some  common  salt  is 
added  to  the  Avater  to  heighten  its  boiling-point.  In  order  to  separate  the  oil  from  the 
water,  there  is  employed  a  peculiarly  shaped  vessel,  called  a  Florentine  flask.  In  this 
way  the  essential  oils  of  aniseed,  chamomile,  lavender,  peppermint,  cloves,  cinnamon,  &c., 
are  obtained,  while  the  most  common  essential  oil— viz.,  that  of  turpentine — is  obtained 
by  the  distillation  of  Venice  turpentine  with  water. 

Preparation  of  Essential  Oils  by  Pressure. — The  essential  oils  largely  met  with  en- 
closed in  the  cells  of  the  skin  of  lemons,  oranges,  bergamots,  and,  in  fact,  all  the  fruits 
belonging  to  the  Citrus  genus,  are  obtained  by  pressing  the  rinds  of  these  fruits. 
Although  the  greater  number  of  the  essential  oils  occur  ready  formed  in  various 
parts  of  the  plants,  some  of  these  oils  are  the  result  of  the  action  of  water— as,  for 
instance,  the  essential  oil  of  bitter  almonds,  which  is  formed  by  the  action  of  water 
upon  amygdalin  under  the  influence  of  a  peculiar  albuminous  compound  called 
synaptase  or  emulsin ;  the  essential  oil  of  mustard  seed  is  formed  in  a  similar  manner, 
bnt  may  be  artificially  prepared  by  distilling  a  mixture  of  propyl  iodide  and  potassium 
cyanide,  &c. 


936  CHEMICAL  TECHNOLOGY.  [SECT.  vin. 

Extraction  of  Essential  Oils  by  Means  of  Fatty  Oils. — Some  of  the  essential  oils, 
more  especially  those  present  in  flowers,  are  so  sparingly  distributed,  that  they  can 
only  be  obtained  by  digesting  the  fresh  flowers  with  pure  olive  oil  or  with  cotton- 
wool soaked  in  sweet  olive  oil,  the  fresh  flowers  being  placed  in  alternate  layers  be- 
tween the  cotton  saturated  with  oil ;  in  some  cases  pure  lard  is  employed.  The 
essential  oils  may  be  recovered  from  the  sweet  oils  by  agitation  with  strong  and 
highly  rectified  alcohol.  The  essential  oils  of  jasmine,  sweet  violets,  hyacinths,  &c., 
are  obtained  in  this  manner. 

Properties  and  Uses  of  Essential  Oils. — These  oils  are  more  or  less  soluble  in 
water,  and  the  solutions  are  known  in  pharmacy  as  distilled  waters.  The  essential 
oils  are  soluble  in  alcohol  in  proportion  to  the  amount  of  oxygen  they  contain. 
Upon  this  property  is  based  the  use  of  these  oils  in  perfumery  and  for  the  preparation 
of  liqueurs  (cordials). 

Perfumery. — This  branch  of  industry  provides  us  with  scented  waters  (esprits  eaux 
de  senteur),  odoriferous  extracts  (extraits  a  odeurs),  perfumed  fats,  pomatums,  oils,  &c. 
Scented  waters  are  really  alcoholic  solutions  of  one  or  more  essential  oils.  The 
alcohol  used  for  this  purpose  requires  to  be  very  pure  and  perfectly  free  from  fusel  oil 
or  other  impurity.  The  oils  are  dissolved  in  the  alcohol,  and  in  order  to  blend  the 
mixture  and  render  it  mellow,  it  is  kept  for  several  months  in  a  bottle  before  being 
sold.  The  old  process  of  distillation  is  very  properly  discarded,  because,  owing  to 
the  high  boiling  point  of  the  oils,  a  portion  was  left  in  the  still,  while  the  scented 
waters  thus  prepared  were  inferior  in  quality.  Eau  de  Mills,  Fleurs  is  prepared  by 
dissolving  in  9  litres  of  alcohol,  60  grammes  of  balsam  of  Peru,  120  grammes  of  oil  of 
bergamot,  60  grammes  of  oil  of  cloves,  1 5  grammes  of  neroli  oil  (oil  of  orange-flowers, 
a  very  expensive  oil),  15  grammes  of  oil  of  thyme,  adding  to  the  mixture  4  litres  of 
orange-blossom  water,  and  120  grammes  of  tincture  of  musk,  obtained  by  digesting  1 5  to 
25  grammes  of  civet  and  75  grammes  of  musk  with  2  litres  of  alcohol.  Eaude  Cologne 
is  obtained  by  dissolving  in  6  litres  of  alcohol  32  grammes  of  essential  oil  of  orange- 
peel  and  equal  quantities  of  oil  of  bergamot,  lemon,  essence  de  limette,  essence  de  petit 
grains,  16  grammes  essence  de  cedro,  and  equal  quantities  of  essence  de  cedrat  and  essence 
de  Portugal;  further.  8  grammes  of  neroli  oil  and  4  grammes  of  rosemary.  The  per- 
fumed extracts  are  generally  obtained  by  the  exhaustion,  by  means  of  alcohol,  of  the 
scented  fats  and  oils  prepared  from  flowers  as  before  described. 

Artificial  Perfumes. — Doebereiner  first  suggested  the  use  of  artificial  perfumes ; 
among  these  are  an  alcoholic  solution  of  amyl  acetate  as  pear  oil,  amyl  valerate  as  apple 
oil,  amyl  butyrate  as  pineapple  oil,  ethyl  pelargonate  as  quince  oil,  ethyl  suberate  as 
essence  of  mulberries,  while  nitrobenzol  mixed  with  nitrotoluol  (commercial  nitrobenzol) 
is  termed  artificial  oil  of  almonds,  and,  when  very  coarse,  is  sold  as  essence  de  mirbane, 
chiefly  used  for  the  preparation  of  aniline.  The  perfumed  fats  (pomatums)  of  better 
quality  are  generally  prepared  from  an  infusion  of  the  flowers  with  oil  or  fat  at  a  tem- 
perature of  65°,  or  by  a  process  of  digestion  in  the  cold  by  placing  the  flowers  in  layers 
between  pure  lard  or  cotton-wool  soaked  in  very  pure  olive  oil ;  enfteurage  is  the 
name  given  to  this  operation.  The  ordinary  pomatums  are  made  simply  of  lard  or 
marrow-fat  coloured  with  turmeric,  annatto,  or  alkanet  root,  and  perfumed  with  a  few 
drops  of  some  essential  oil.* 

Preparation  of  Cm-dials. — The  aim  of  the  preparation  of  liqueurs  (cordials)  is  to 
render  brandy  a  more  agreeable  beverage  by  the  addition  of  sugar,  glycerine,  and 
aromatic  substances.  A  distinction  is  made  between  the  finer  liqueurs  \rosoglio}  and 

*  The  reader  may  here  consult  Piesse's  "  Art  of  Perfumery."  5th  edit.  London  :  Piesse  & 
Lubin.  It  is  not  demonstrated  that  the  artificial  perfumes  made  according  to  Doebereiner's 
process  agree  in  their  physiological  action  with  the  natural  products  which  they  simulate. — 
[EDITOR.] 


SECT.    VIII.] 


ESSENTIAL  OILS  AND   RESINS. 


937 


ordinary  cordials  (aqua  vitce)  according  to  the  quality  of  the  materials  employed  for 
the  purpose.  When  a  sufficiently  large  quantity  of  sugar  is  used  to  render  the 
liqueurs  thickly  fluid  they  are  designated  cremes,  while  those  made  with  the  juices  of 
fruit  obtained  by  pressure,  sugar  and  alcohol  are  called  ratafia.  These  liqueurs  are  not 
prepared  to  any  great  extent  in  this  country ;  but  in  France,  Italy,  Austria,  and 
especially  in  Holland,  the  preparation  is  on  a  large  scale. 

The  basis  of  all  liqueurs  is  a  very  highly  rectified  and  pure  alcohol.     The  vegetable 
materials  used  in  the  liqueurs  may  be  classified  under  three  heads : — In  the  first  place, 
such  vegetable  substances  as  contain  essential  oils  and  are  used  for  that  reason  only, 
caraway,  aniseed,  juniper- berries,  mint,  lemon-peel,  orange-blossom,  and  bitter  almonds. 
These  substances,  previously  bruised  or  cut  up,  are  digested  with  alcohol,  the  mixture 
being  next  distilled,  or,  as  is  more  generally  the  case,  alcoholic  solutions  of  the  essential 
oils  are  employed  and  the  preparation  performed  in  the  cold.     To  the  second  class 
belong  such  vegetable  substances  as  are  used  for  the  sake  of  their  essential  oil  and 
for  their  aromatic  bitter  substances,   chiefly  roots,  such   as   sweet  calamus,  gentian, 
ginger,  orange-peel,  unripe  bitter  Cura9oa  apples  (a  peculiar  kind  of  orange),  worm- 
wood, cloves,  cinnamon,  vanilla  (the  pod  of  an  orchidaceous  plant  originally  brought 
from    Mexico).     These   substances   having    been    bruised  are   digested  with    alcohol 
either  at  the  ordinary  temperature  of  the  air  or  at  50°  or  60°,  the  result  being  the 
formation  of  what  is  termed  a  tincture.      To  the  third  class  belong  fruits,  such  as 
cherries,  pineapples,  strawberries,  raspberries,  the  juice  of  which  is  obtained  by  pres- 
sure,  passed    through  a  sieve,  and  mixed  with    alcohol   and  sugar  or  syrup,  viz.,  a 
solution  of  4  Ibs.  of  refined  loaf-sugar  in  4  litres  of  water.     The  liqueurs  generally 
contain  from  46  to  50  per  cent,  of  alcohol.     It  is  customary  to  colour  the  liqueurs 
red  with  santal-wood,  cochineal,  aniline  red,  or  with  the  Coccus  polonicus,  as  in  the 
case  with  the  celebrated  Alkermes  de  Firense,  a  liqueur  made  at   Florence ;  yellow 
with  saffron,  turmeric,  or  marigold  flowers  (Calendula) ;  green  by  mixing  yellow  and 
blue ;  blue,  with  tincture  of  indigo ;  violet,  with  aniline  violet ;  while  in  many  cases 
caramel  is  used  to  impart  a  brown  colour.      The  so-called  cremes  contain  for  every 
litre  of  liquid  about  i  Ib.  of  sugar  or  a  corresponding  quantity  of  glycerine.     As  an 
instance  of  the  composition  of  a  liqueur,  Maraschino 
consists  of  4  litres  of  raspberry  water,  175  litres 
orange-blossom   water,    1-5    litres   kirschwasser  (a 
Swiss  preparation  —  from  cherries  fermented  and 
distilled — a  strong,   spirituous   liquid   which  con- 
tains hydrocyanic  acid),  18  Ibs.  of  sugar,  and  9  litres 
of  alcohol  at  from  89  to  90  per  cent.     Liqueurs 
are  very  similar  to  cremes,  but  contain  less  sugar. 
English  bitter  contains  5  parts  of  flavedo  corticum 
aurantiorum  (outer  rind  of  dried  orange  peel),  6 
parts  of  cinchona  bark,  6   parts  of  gentian,  8  parts 
of  Carduus  benedictus,  8  parts  of  centaury,  8  parts 
of  wormwood,  4  of  orris  root  digested  with  54  litres 
of  alcohol  at    50  per  cent.,  while  after  filtration 
i-2  Ibs.  of   sugar  are   added.      Cherry  ratafia: — 
20  litres  of  cherry  juice,  20  litres  of  alcohol  at 
85  per  cent.,  30  Ibs.  sugar,  and  usually  4  to  8  litres 
of  bitter  almond  water.     Peppermint :— 2-5  litres 
of  essential  oil  of  peppermint  dissolved  in  i  litre  of 

alcohol  at  80  per  cent. ;  this  solution  is  poured  into  54  litres  of  alcohol  at  20  per  cent., 
sweetened  with  60  Ibs.  of  sugar  previously  dissolved  in  26  litres  of  water,  and  , 
with  either  tincture  of  indigo  or  turmeric. 


Fig.  596. 


c 

-~.=  —  • 

'•—V. 

-*~  -~-°~ 

a 

0 

938  CHEMICAL  TECHNOLOGY.  [SECT.  vm. 

In  Miirrle's  apparatus  for  the  extraction  of  ethereal  oils  (Fig.  596)  there  is  suspended 
a  copper  boiler,  .4,  in  the  round  iron  furnace,  0.  Steam  enters  through  the  tube,  E, 
into  the  receiver,  B,  on  the  perforated  bottom  of  which,  s,  the  plants  are  laid,  and  it 
escapes  then  with  the  ethereal  oil  through  the  pipe,  b,  into  the  worm,  C.  The  dis- 
tillate collects  first  in  the  Florentine  receiver,  D,  where  the  ethereal  oil  separates  out  at 
the  top  whilst  the  water,  being  heavier,  flows  back  through  the  bent  tube-funnel  into  the 
boiler,  A,  to  be  evaporated  anew.  The  distillation  is  continued  until  the  water  escaping 
from  the  worm  is  scentless.  When  the  distillation  is  at  an  end  the  capital  is  detached 
and  raised  by  means  of  the  tackle,  K,  when  the  receiver,  B,  can  be  lifted  off  the  two 
handles,  b,  b.  The  perforated  bottom  is  taken  out  downwards  and  the  residue  is  then 
thrown  away.  The  charging  can  also  be  executed  rapidly,  the  upper  aperture  being 
closed  by  the  accompanying  screw  lid  and  B  being  inserted,  in  which  position  it  stands 
on  its  three  feet,  f.  When  B  is  filled  the  perforated  bottom  is  introduced,  the  whole 
is  inverted  and  replaced  upon  the  boiler,  A.  By  providing  a  second  receiver,  B,  of 
the  same  size,  the  working  power  of  the  apparatus  can  be  increased,  as  one  receiver  is 
at  work  whilst  the  other  is  being  emptied  and  filled  again.  The  catch-pan,  E,  prevents 
any  extractive  matter  from  falling  down  into  the  boiler,  A,  burning  and  spoiling  the 
odour  of  the  essential  oil. 

In  the  process  of  enfleurage  it  has  lately  been  proposed  to  use  chlormethyl  instead 
of  fatty  oils. 

The  artificial  essences  simulating  the  odour  of  certain  natural  perfumes  may  be 
legitimately  used  in  cosmetics,  &c.,  but  it  is  at  least  doubtful  whether  their  physiolo- 
gical action  is  identical  with  that  of  the  natural  products  which  they  imitate.  Hence 
their  use  in  the  production  of  liqueurs  is  questionable. 

Resins. — By  the  action  of  the  oxygen  of  the  air  most  of  the  essential  oils  are 
gradually  thickened,  and  at  length  converted  into  a  substance  termed  resin.  Resins- 
are  frequently  met  with  in  the  vegetable  kingdom ;  in  some  instances,  as  with 
coniferous  trees,  resin  flows  spontaneously  from  the  wood  in  combination  with  an 
essential  oil,  so-called  Venice  turpentine,  which  hardens  by  exposure  to  air.  Some 
resins  are  extracted  from  vegetable  matter  by  means  of  alcohol,  this  solution  being 
either  precipitated  with  water  or  evaporated  to  dryness.  Resins  are  either  soft,  and 
are  then  termed  balsams,  chiefly  solutions  of  resin  in  essential  oils,  or  hard.  To  the 
former  belong  Venice  turpentine,  Canada  balsam,  balsam  of  Peru,  copaiva  balsam,  &c. ; 
to  the  latter,  amber  (a  fossil  resin),  anime,  copal,  gum  dammar,  mastic,  shellac,  asphalte. 
The  gum  resins  are  obtained  from  incisions  made  in  certain  kinds  of  plants,  the  milky 
juice  of  which  hardens  by  exposure  to  air;  these  substances  are  partly  soluble  in 
water,  and  yield  with  it  in  many  instances  an  emulsion ;  for  instance,  asafcetida,  gum 
gutti,  &c.  Many  gum  resins  possess  a  very  strong  odour  and  contain  essential  oils. 
Although  it  is  customary  to  treat  of  caoutchouc  and  gutta-percha  under  the  head  of 
resins,  these  substances  are  not  related  to  resins  at  all,  but  belong  to  a  separate  class 
of  bodies,  among  which,  according  to  Dr.  G.  J.  Mulder's  researches,  the  so-called  drying 
oils  must  be  enumerated. 

Sealing- Wax. — Sealing-wax  of  modern  time  (for  mediaeval  sealing-wax  was  really 
a  mixture  of  wax  with  Venice  turpentine  and  colouring  matter)  is  prepared  from 
shellac,  to  which  some  turpentine  is  added  in  order  to  promote  fusibility  and  prevent 
brittleness.  Red  sealing-wax  and  bright  coloured  wax  are  made  of  a  very  pale,  some- 
times even  purposely  bleached,  shellac,  while  black  and  dark  coloured  sealing-wax  are 
made  of  more  deeply  coloured  shellac.  In  addition  to  shellac  and  turpentine,  sealing- 
wax  contains  earthy  matter,  added  not  only  for  the  purpose  of  increasing  the  weight, 
but  also  for  preventing  the  too  rapid  fusion  of  the  mass ;  chalk,  magnesia,  plaster  of 
Paris,  zinc-white,  barium  sulphate,  kaolin,  and  finely  divided  silica,  are  employed  for  this 
purpose.  Red  sealing-wax  is  prepared  by  melting  together  in  an  iron  pan  placed  on  a 


SECT.    VIII.] 


ESSENTIAL  OILS  AND  RESINS. 


939 


charcoal  fire  4  parts  of  shellac,  i  part  of  Venice  turpentine,  and  3  parts  of  cinnabar 
(vermilion),  care  being  taken  to  stir  the  mixture  constantly.  Ordinary  red  sealing- 
wax  is  often  composed  of  • — 


3- 

4- 

5- 

Shellac 

550 

620 

550 

7OO 

600 

Venice  turpentine 

740 

680 

6OO 

540 

600 

Chalk  or  magnesia 

300 

200 

— 

— 

Gypsum  or  zinc-white 

200 

— 

— 

— 

— 

Baryta  white 

— 

IOO 

380 

300 

300 

Vermilion 

130 

22O 

340 

300 

300 

Oil  of  turpentine 

— 

— 

2O 

25 

The  cooled  but  still  soft  mass  is  either  rolled  on  a  slab  of  marble  and  shaped  into 
sticks,  or  the  fluid  mass  is  run  into  brass  moulds.  Perfumed  sealing-wax  contains 
either  benzoin  resin,  storax,  or  balsam  of  Peru.  The  various  colours  are  imparted  by 
cobalt  ultramarine  (cobalt  blue),  lead  chromate,  bone-black,  &c.  Marbled  sealing- 
wax  is  made  by  mixing  variously  coloured  sealing-waxes  together.  Inferior  kinds  of 
sealing-wax — parcel-wax — are  coloured  with  red  oxide  of  iron,  while  instead  of  shellac 
ordinary  resin  is  used  with  gypsum  or  chalk.  New  Zealand  resin,  the  produce  of  the 
Xanthorrhcta  hastilis,  is  now  frequently  used  instead  of  shellac. 

Asphalte. — This  material,  sometimes  known  as  bitumen,  is  a  black,  glossy,  brittle 
resin,  probably  formed  by  the  gradual  oxidation  of  petroleum  oil ;  it  occurs  very 
largely  on  the  island  of  Trinidad,  on  the  northern  coast  of  S.  America,  at  the  mouth  of 
the  Orinoco,  on  the  water  of  the  Dead  Sea  (anciently  Lacus  Asphaltites),  and  in  some 
other  localities — viz.,  France,  Seyssel,  Department  de  1'Ain,  a  limestone  containing 
1 8  per  cent,  of  asphalte.  By  boiling  this  limestone,  previously  broken  up  into  small 
lumps,  with  water,  there  is  obtained  an  asphalte,  7  parts  of  which  are  mixed  with  90 
parts  of  native  asphalte  limestone.  The  materials  are  ground  up  together  and  are 
employed  for  paving  purposes,  being  compressed  with  heavy  and  highly  heated  irons. 
Asphalte  is  also  found  at  Yal  de  Travers,  Switzerland ;  Limmer,  Hanover ;  Lobsann, 
Lower  Alsace;  and  in  the  Northern  Tyrol.  Asphalte,  or  bitumen,  is  somewhat 
soluble  in  alcohol,  readily  so  in  Persian  naphtha,  oil  of  turpentine,  benzene,  and 
benzoline.  It  is  used  in  varnish  making  (iron  varnish),  in  engraving  copper  and  steel, 
as  an  etching  ground,  and  as  an  oil  paint.  Asphalte  mixed  with  sand,  lime,  or  lime- 
stone, is  largely  used  for  paving  purposes,  being  durable  and  somewhat  elastic ;  it  is 
employed  for  this  purpose  either  in  a  pasty  or  semi-fused  state,  or  in  powder.  Instead 
of  native  asphalte,  Busse's  terresin,  a  mixture  of  coal-tar,  lime,  and  sulphur  is  some- 
times used,  as  well  as  coal-tar  asphalte,  obtained  from  gas  works.  The  residue  of  the 
distillation  of  coal-tar  is  often  employed  instead  of  asphalte,  and  pebbles  mingled  with 
coal-tar  are  now  used  to  form  excellent  footpaths  in  some  parts  of  the  metropolis. 

Tubes  of  paper,  saturated  with  asphalte,  are  often  used  for  water-,  gas-,  and  drain- 
pipes. Sheets  of  strong  paper  and  pieces  of  woven  cloths  steeped  in  asphalte  are  used 

for  roofing. 

Caoutchouc. — Elastic  gum,  or  india-rubber,  is  derived  from  the  milky  juice  of  a 
series  of  plants,  occurring  also  in  opium ;  but  the  commercial  article  is  obtained  from 
the  milky  juice  of  various  trees  belonging  to  the  natural  orders  of  the  Urticece, 
EuphorUacece,  Apocynece.  Among  the  trees  which  yield  caoutchouc  in  large  quantity 
are  the  Siphonia  cahucu,  in  South  America,  and  the  East  Indian  species,  Urceola  elastica; 
Ficus  elastica,  F.  religiosa,  F.  indica,  also  yield  caoutchouc.  It  is  obtained  by  making 
incisions  in  the  tree  and  collecting  the  exuding  juice  in  vessels  of  dried  clay.  The 
juice  is  solidified  by  the  application  of  fire  or  by  exposure  to  the  sun's  rays ;  the  variety 
known  as  lard  gum  is  usually  dried  by  exposure  to  the  sun.  Perfectly  pure  caoutchouc 
is  a  white  and  in  thin  sheets  semi-transparent,  substance ;  its  texture  is  not  fibrous ; 


940  CHEMICAL  TECHNOLOGY.  [SECT.  VIH. 

it  is  perfectly  elastic,  becoming  turbid  and  fibrous  when  strongly  stretched.  Excessive 
cold  renders  it  hard  but  not  brittle.  The  specific  gravity  of  caoutchouc  is  0*925. 
Although  hot  water  and  steam  render  caoutchouc  soft,  it  is  not  further  acted  upon  by 
them.  It  is  insoluble  in  alcohol,  not  acted  upon  by  dilute  acids  or  strong  alkalies, 
while  for  a  very  long  time  it  resists  the  action  of  chlorine.  Strong  sulphuric  and 
nitric  acids  decompose  india-rubber,  and  when  red  fuming  nitric  acid  is  employed  a 
violent  combustion  ensues.  If  strongly  stretched  india-rubber  is  placed  in  cold 
water  for  a  few  minutes  it  temporarily  loses  its  elasticity,  which  it  regains  by  being 
immersed  for  a  few  minutes  in  water  at  45°.  By  exposure  to  a  gentle  heat  caoutchouc 
becomes  supple,  and  finally  melts  at  200°,  with  partial  decomposition,  forming  a  viscous 
mass  which  does  not  again  become  solid  on  cooling.  When  caoutchouc  is  ignited  in 
contact  with  air  it  burns  with  a  sooty  flame.  Of  all  substances  with  which  we  are 
acquainted  none  would  be  better  suited  to  gas  manufacture  than  caoutchouc,  which, 
according  to  experiments  made  many  years  ago  at  Utrecht,  yields  at  red  heat  rather 
more  than  30,000  cubic  feet  of  gas  to  the  ton,  the  gas  being  quite  free  from  sulphur 
and  ammonia  compounds,  and  its  illuminating  power  very  superior  to  that  of  the  best 
oil  gas.  Unfortunately  caoutchouc  is  much  too  high  priced  for  this  application. 
Caoutchouc  may  be  kneaded  with  sulphur  and  other  substances  by  the  aid  of  heat, 
becoming  converted  into  what  is  known  as  vulcanised  india-rubber,  vulcanite,  ebonite, 
&c.  When  caoutchouc  is  submitted  to  dry  distillation,  at  much  below  red  heat,  it 
yields  only  oily  fluids,  consisting  of  carbon  and  hydrogen  (caoutchen,  heveen,  &c.), 
which  are  par  excellence  solvents  for  caoutchouc.  Caoutchouc  itself  contains  only 
carbon  and  hydrogen,  its  formula  being  C4H7  (in  100  parts:  87*5  carbon  and  12-5 
hydrogen) ;  probably,  however,  caoutchouc  is  a  more  complex  mixture  of  various 
hydrocarbons. 

Solvents  of  Caoutchouc. — India-rubber  is  soluble  in  ether  containing  no  alcohol,  in  the 
oils(empyreumatic)of  caoutchouc,  in  Persian  naphtha,  oil  of  turpentine,  carbon  disulphide, 
and  in  chloroform.  Industrially  the  ethereal  solution  of  caoutchouc  is  useless,  because 
it  contains  hardly  more  than  a  trace  of  that  substance.  As  regards  oil  of  turpentine, 
it  dissolves  caoutchouc  only  when  the  oil  is  very  pure  and  with  the  application  of  heat ; 
the  ordinary  oil  of  turpentine  of  commerce  causes  india-rubber  to  swell  rather  than  to 
become  dissolved.  In  order  to  prevent  the  viscosity  of  the  india-rubber  when 
evaporated  from  this  solution,  i  part  of  caoutchouc  is  worked  up  with  u  parts  of 
turpentine  into  a  thin  paste,  to  which  is  added  £  part  of  a  hot  and  concentrated 
solution  of  potassium  sulphide  (K2S5)  in  water ;  the  yellow  liquid  formed  leaves  the 
caoutchouc  perfectly  elastic  and  without  any  viscosity.  The  solutions  of  caoutchouc 
in  coal-tar  naphtha  and  benzoline  are  most  suited  to  unite  pieces  of  caoutchouc,  but  the 
odour  of  the  solvents  is  perceptible  for  a  long  time.  As  chloroform  is  too  expensive 
for  common  use,  carbon  disulphide  is  the  most  usual  and  also  the  best  solvent  for 
caoutchouc.  This  solution,  owing  to  the  volatility  of  the  menstruum,  soon  dries,  leav- 
ing the  caoutchouc  in  its  natural  state.  When  alcohol  is  mixed  with  carbon  disulphide, 
the  latter  no  longer  dissolves  the  caoutchouc,  but  simply  softens  it  and  renders  it  capable 
of  being  more  readily  vulcanised.  Alcohol  precipitates  solutions  of  caoutchouc  and 
gutta-percha. 

The  great  diversity  of  the  sorts  of  caoutchouc,  according  to  Hoehnel,  is  not  merely 
external,  but  extends  to  their  essential  properties,  and  is  due  both  to  the  different 
methods  of  preparation  and  to  the  fact  that  the  commercial  article  is  derived  from 
upwards  of  fifty  plants,  belonging  to  different  families. 

The  methods  of  preparing  caoutchouc  from  the  milky  juice  are  as  follows : — (i)  The 
juice  is  poured  upon  a  mould  in  thin  layers,  and  these  layers  are  gradually  dried  in  hot 
smoke.  More  than  one  hundred  layers  are  thus  often  produced.  (2)  The  milky  juice  is 
conveyed  directly  from  the  tree  to  small  pits  made  in  the  soil.  The  soil  acts  as  a  filter ; 


SECT,  viii.]  ESSENTIAL  OILS  AND    RESINS.  941 

the  watery  part  of  the  milk  filters  off  or  partly  evaporates,  whilst  the  caoutchouc  remains 
behind.  This  method  is  very  crude,  and  can  be  applied  only  in  the  dry  season.  (3)  The 
milky  juice  is  mixed  with  a  little  water  and  allowed  to  stand  for  some  days  to  coagulate. 
The  mass  thus  separated  out  is  freed  from  excess  of  water  by  kneading  and  pressing,  and 
then  dried  in  the  sun  or  in  smoke.  (4)  The  milky  juice  is  mixed  with  a  solution  of 
salt  or  of  alum,  with  an  acid,  or  with  the  extract  of  certain  plants,  whereon  it  quickly 
curdles ;  the  clot  is  then  pressed  and  dried.  (5)  The  milky  juice  is  mixed  with  4  to  8 
parts  of  water,  when  the  caoutchouc  comes  to  the  surface  like  a  thick  cream,  which  is 
collected,  repeatedly  washed,  and  dried  either  in  smoke  or  very  slowly  in  the  air. 
(6)  The  milky  juice  is  simply  allowed  to  dry  in  shallow  vessels.  (7)  The  milky  juice 
is  concentrated,  and  is  caused  to  flow  down  upon  the  arm  of  the  collector,  where  it 
quickly  dries,  and  is  rolled  off  in  the  form  of  a  ring.  (8)  Or  the  concentrated  juice 
flows  down  upon  the  stem  or  drops  to  the  ground,  where  it  is  collected  and  moulded  into 
balls. 

The  most  valuable  kinds  known  in  commerce,  the  "  Para,"  are  obtained  by  the  first 
process.  The  same  method  is  in  use  in  Columbia.  Para  caoutchouc  consists  of  strata 
generally  less  than  ^  mm.  in  thickness,  white  or  dark  grey,  and  it  appears  separated  by 
sharp  black  lines  where  it  has  been  exposed  to  smoke ;  the  finer  and  the  more  equal 
these  layers  are — which  may  be  seen  on  section — the  better  is  the  sample.  Inclosed  air- 
bubbles  signify  an  inferior  quality.  As  soon  as  there  are  seen  layers  from  i  to  2  centi- 
metres in  thickness,  white,  and  full  of  bubbles,  we  have  a  second-rate  Para.  The  second 
process  is  in  use  in  Columbia,  Central  America,  and  occasionally,  along  with  other 
methods,  in  Africa  and  Southern  Asia;  it  yields  a  watery,  contaminated,  inferior 
product.  The  processes  (3)  and  (4)  yield  an  article  rich  in  water,  often  containing  un- 
coagulated  milky  juice.  Those  kinds  are  especially  bad  which  have  been  coagulated  by 
the  addition  of  foreign  matter,  salts,  &c.  Coagulation  is  practised  in  the  north  of 
South  America,  in  Central  America,  West  Africa,  India,  and  the  Sunda  Islands. 
These  kinds  are  often  dried  too  rapidly,  and  have  therefore  a  black  surface,  smelling  of 
smoke  and  sometimes  are  even  burnt.  If  the  drying  is  too  rapid,  the  surface  remains 
smeary.  Such  sorts  are  named  resinous,  and  are  often  found  in  Indian,  "West  African, 
and  Central  American  lots.  It  must  not  be  forgotten  that  South  Asiatic  samples 
are  often  artificially  contaminated  with  resins  or  vegetable  extracts.  Such  resinous 
sorts  are  in  very  low  estimation.  Recent  samples  of  qualities  obtained  by  coagulation 
show  on  section  a  homogeneous  grey  rind,  a  few  millimetres  in  thickness,  and  a  thick, 
white,  violet,  yellow,  or  flesh-coloured  nucleus,  which  is  quite  soft  and  often  contains 
water  or  milky  juice.  The  sorts  obtained  by  coagulation  are  poor  in  fragments  of  wood 
and  bark,  which  occur  most  abundantly  in  sorts  prepared  by  methods  (7)  or  (8). 
Process  (5)  is  used  in  some  parts  of  Central  America,  and  yields  a  good  quality.  Pro- 
cess (6)  gives  a  similar  product,  highly  esteemed,  and  imported  from  the  Gaboon  and 

from  India. 

Preparation  and  Use  of  India-rubier. — India-rubber  is  used  to  clean  paper,  to  rub 
out  black-lead  pencil  marks,  for  making  waterproof  fabrics  (macintosh),  rubber  sponge, 
tubing,  elastic  webs,  lutes,  &c.* 

Vulcanised  Caoutchouc. — When  caoutchouc  is  immersed  for  seme  time  in  molten 
sulphur  it  absorbs  the  latter,  and  becomes  converted  into  a  yellow,  very  elastic  mass. 
The  most  valuable  property  of  vulcanised  india-rubber  is  its  elasticity  even  at  low 
temperatures ;  ordinary  india-rubber  hardens  at  3°.  Vulcanised  india-rubber  is  in- 
soluble in  the  solvents  of  caoutchouc.  It  resists  compression  to  a  very  great  extent ;  hence 
its  use  instead  of  steel  springs  on  tramcars.  According  to  the  old  method,  caoutchouc 

*  The  most  important  of  all  the  uses  of  caoutchouc  at  present  is  in  the  insulation  of  electric 
wires  and  cables.  It  is  the  preferable  ingredient  in  all  cases  when  the  conduction  traverses  a  dry 
medium,  such  as  air,  dry  earth,  the  interior  of  houses,  &c. — [EDITOR.] 


942  CHEMICAL  TECHNOLOGY.  [SECT.  vin. 

was  vulcanised  by  being  placed  for  some  ten  to  fifteen  minutes  in  thin  plates  in 
molten  sulphur  heated  to  120°,  the  weight  of  the  caoutchouc  increasing  10  to  15  per 
cent.  The  material  was  subsequently  mechanically  treated  by  pressure,  and  then 
heated  to  150°.  In  order  to  prevent  efflorescence  of  the  sulphur,  caoutchouc  is 
sometimes  heated  to  120°,  and  then  kneaded  by  the  aid  of  powerful  machinery,  with 
either  kermes  (Sb2S)  or  a  mixture  of  sulphur  and  arsenic  sulphide.  At  the  present 
day  Parkes's  method  is  generally  adopted  :  the  caoutchouc  is  simply  immersed  in  a 
mixture  of  40  parts  of  carbon  disulphide  and  i  part  of  sulphur  chloride ;  it  is 
next  placed  in  a  room  heated  to  21°,  and  when  all  the  carbon  disulphide  has  been 
volatilised,  the  process  is  in  so  far  complete  that  it  is  only  requisite  to  boil  the 
material  in  a  solution  of  500  grammes  of  caustic  potassa  to  10  litres  of  water,  the 
vulcanised  caoutchouc  being  next  washed  to  remove  excess  of  alkali.  In  1870 
Humphrey  introduced  the  use  of  petroleum  ether  (benzoline)  instead  of  carbon  disul- 
phide, as  the  former  fluid  dissolves  sulphur  chloride  readily.  H.  Gaultier  de  Claubry 
(1860)  vulcanised  caoutchouc  by  the  aid  of  bleaching-powder  and  flowers  of  sulphur. 
This  mixture  produces  sulphur  chloride,  and  the  caoutchouc  treated  by  it  contains 
some  calcium  chloride.  Neither  this  process  nor  that  of  Gerard — the  use  of  a  solution 
of  potassium  pentasulphide  of  40°  to  49°  Tw.,  aided  by  a  temperature  of  150°,  and  a 
pressure  of  5  atmos.  or  75  Ibs.  to  the  square  inch — are  practically  available  on  the 
large  scale.  Articles  of  vulcanised  india-rubber  are  made  of  ordinary  caoutchouc 
and  then  vulcanised.  The  uses  of  vulcanised  india-rubber  are  so  many  and  so  gene- 
rally known  that  it  is  hardly  necessary  to  enumerate  them. 

In  1852  Goodyear  discovered  a  process  by  which  caoutchouc  is  rendered  hard 
and  wood-like,  being  then  termed  vulcanite  or  ebonite.  This  substance  exhibits  a 
black  or  brown  colour,  and  is  largely  used  for  making  combs,  imitation  jet  ornaments, 
stethescopes,  and  a  variety  of  articles.  The  preparation  of  ebonite  differs  from  that 
of  vulcanite  only  in  the  introduction  of  a  larger  amount  of  sulphur  (30  to  60  per 
cent.),  at  a  higher  temperature,  with  the  addition  of  other  substances — shellac,  gutta- 
percha,  asphalte,  chalk,  barium  sulphate,  pipe-clay,  zinc,  antimony,  or  copper  sulphides, 
&c.  Ebonite  is  capable  of  taking  a  high  polish  ;  it  does  not,  as  is  the  case  with  horn, 
become  rough  when  cleaned  with  hot  water ;  and  it  is  to  some  extent  elastic. 

For  articles  which  require  elasticity,  such  as  artificial  whalebone,  walking-sticks, 
&c.,less  sulphur  is  used  than  for  those  which  require  rigidity,  such  as  rulers,  discs  for 
frictional  electric  machines,  &c.  The  hardness  required  cannot  be  obtained  with  less 
than  20  per  cent.,  but  quantities  above  35  per  cent,  are  useless,  on  account  of  the 
increasing  brittleness.  After  the  caoutchouc,  sulphur,  and  the  other  ingredients  have 
been  duly  mixed  together,  and  the  articles  are  moulded  into  the  required  shapes 
the  actual  combination  is  effected  by  means  of  steam.  The  articles,  placed  on  small 
trucks,  are  run  upon  rails  into  a  strong  cylindrical  boiler,  which  is  then  tightly  closed 
Steam  is  then  admitted  at  a  pressure  not  exceeding  4^  atmos.  The  introduction 
of  the  steam  must  be  regulated  in  such  a  manner  that  the  internal  temperature 
gradually  rises  to  135°.  From  this  moment  a  very  uniform  temperature  must  be 
maintained.  A  few  degrees  too  high  would  burn  the  contents  of  the  boiler  ;  and  a  few 
degrees  too  low,  or  a  fluctuation  in  the  temperature,  would  render  the  whole  work 
nugatory.  Vulcanite  mixed  with  sand,  emery,  &c.,  sometimes  serves  for  the  produc- 
tion of  artificial  grindstones — whetstones  for  sharpening  scythes,  sickles,  and  other 
agricultural  implements.  Vulcanite  expands  very  considerably  in  heat,  about  three 
times  as  much  as  zinc. 

The  yield  of  caoutchouc  in  1882  was  20,000  tons. 

Gutta-percha. — Plastic  gum,  gutta-  or  getah-percha,  gettannia  gum,  taban  gum,  is  a 
substance  in  many  respects  similar  to  caoutchouc;  it  is  the  inspissated  juice  of  the 
Isonandra  gutta,  a  tree  growing  in  Malacca,  Borneo,  Singapore,  Java,  Madura,  and 
adjacent  countries. 


SECT.  VJIL]  ESSENTIAL  OILS  AND  RESINS.  943 

Gutta-percha  was  at  first  obtained  by  felling  the  trees  and  collecting  the  exuding 
juice,  either  in  suitable  vessels  or  in  shallow  pits  dug  in  the  soil,  or  in  baskets  made 
from  banyan  leaves,  the  juice  being  left  to  coagulate  under  the  action  of  the  sun. 
More  recently  the  practice  has  been  to  make  deep  incisions  in  the  trees,  and  to  collect 
the  exuding  juice.  The  lumps  of  solid  gutta-percha  thus  obtained  are  united  by 
softening  in  hot  water  and  by  pressure.  The  raw  gutta-percha  of  commerce  is  a  dry, 
red,  or  marbled  mass,  not  unlike  leather  cuttings  which  have  been  pressed  together ; 
the  raw  material  contains  as  impurities  some  sand,  small  pieces  of  wood  and  bark,  and 
sometimes  other  inspissated  vegetable  juices  of  less  value  than  gutta-percha.  The  name 
gutta-percha  means,  in  fact,  Sumatra  gum,  this  island  being  known  in  Malay  language  as 
Pulo-percha.  When  perfectly  pure,  gutta-percha  is  quite  white,  its  ordinary  brown 
colour  being  due  to  an  acid  insoluble  in  water,  which  is  present,  partly  free,  partly  as 
insoluble  salts  (of  magnesia,  ammonia,  potash,  and  manganese  protoxide),  of  apocrenic 
acid ;  but  in  addition  there  is  a  small  quantity  of  organic  colouring  matter.  Gutta- 
percha  is  a  mixture  of  several  oxygen-containing  resins,  which  appear  to  be  the  products 
of  the  oxidation  of  a  hydrocarbon,  the  formula  of  which  is  C20H60.  Payen  found  in 
gutta-percha  the  following  substances  : — 75  to  80  per  cent,  of  pure  gutta-percha,  14  to 
21  per  cent,  of  a  white  crystalline  resin  termed  alban,  and  from  4  to  6  per  cent,  of  an 
amorphous  yellow  resin  named  fluavil.  Previously  to  being  used,  gutta-percha  is 
cleansed  from  dirt  by  a  mechanical  process  of  kneading  in  warm  water,  being  then 
usually  rolled  into  thick  plates  or  sheets.  The  purified  material  exhibits  a  chocolate- 
brown  colour,  and  is  not  transparent  unless  first  reduced  to  sheets  as  thin  as  paper,  when 
the  gutta-percha  is  equal  to  horn  in  transparency.  At  the  ordinary  temperature  of  the 
air  gutta-percha  is  very  tough,  stiff,  not  very  elastic  nor  ductile.  Every  square  inch 
of  a  strap  of  gutta-percha,  if  of  good  quality  and  as  homogeneous  as  possible,  can 
sustain  a  strain  of  1872  kilos,  without  breaking.  Its  sp.  gr.  =  0-979.  At  50°  it 
becomes  soft,  and  at  70°  to  80°  it  is  so  soft  as  to  be  very  readily  moulded,  while  two 
pieces  pressed  together  at  this  temperature  become  perfectly  joined.  By  the  aid  of 
heat,  gutta-percha  can  be  rolled  into  sheets,  drawn  into  thread,  and  kneaded  into  a 
homogeneous  mass  with  caoutchouc. 

Solvents  of  Gutta-percha. — Gutta-percha  is  insoluble  in  water,  alcohol,  dilute  acids, 
and  alkalies ;  it  is  soluble  in  warm  oil  of  turpentine,  carbon  disulphide,  chloroform, 
coal-tar  oil,  caoutchouc  oil,  and  in  the  somewhat  similar  oil  obtained  by  the  dry  distilla- 
tion of  gutta-percha.  Ether  and  some  of  the  essential  oils  render  gutta-percha  pasty. 
As  already  stated,  this  substance  becomes  soft  in  hot  water,  absorbing  a  small  quantity, 
which  is  only  very  slowly  driven  off.  Dry  gutta-percha  is  a  very  good  insulating 
material  for  electricity. 

Uses  of  Gutta-percha. — The  natural  properties  of  this  substance  indicate  its  use  as  a 
substitute  for  leather,  papier-mache,  cardboard,  wood,  millboard,  paper,  metal,  &c.,  in 
all  cases  not  exposed  to  the  action  of  heat,  and  where  a  substance  is  desired  resisting 
water,  alcohol,  dilute  acids,  and  alkalies.  The  raw  material,  previously  to  being  moulded 
into  shape,  is  purified,  and  kneaded  by  means  of  powerful  machinery  and  with  the 
assistance  of  hot  water  (some  soda  or  bleaching-powder  solution  being  added),  the  aim 
being  the  removal  of  such  impurities  as  are  only  mechanically  mixed  with  the  gutta- 
percha,  as  well  as  the  removal  of  some  of  the  colouring  matter,  while  a  more  homoge- 
neous mass  is  produced.  The  purified  substance  is  next  submitted  to  the  action  of 
kneading  machinery  similar  to  that  in  use  for  working  up  caoutchouc,  while  it  is  rolled 
out  into°plates  of  some  3  centimetres  in  thickness.  Gutta-percha  is  moulded  into  tubes 
by  the  aid  of  machinery  such  as  are  employed  for  making  lead  and  block-tin  tubing. 
Many  objects  are  made  from  gutta-percha  by  pressing  it  while  soft  into  wooden  or 
metal  moulds.  By  the  use  of  a  solution  of  gutta-percha  in  benzol,  it  may  be  glued  to 
leather  and  similar  substances.  It  is  almost  impossible  to  enumerate  the  various  uses 
of  gutta-percha.  It  is  employed  for  straps  for  machinery  instead  of  leather,  tubes  for 


944  CHEMICAL  TECHNOLOGY.  [SECT.  vin. 

conveying  water,  pumps,  pails,  surgical  instruments,  ornamental  objects  of  various 
kinds,  for  covering  telegraph  wires,  &c.*  Unlike  pure  caoutchouc,  gutta-percha  becomes 
gradually  deteriorated  by  exposure  to  the  atmosphere,  so  that  ultimately  it  can  be  even 
readily  ground  to  powder .t 

Mixture  of  Gutta-percha  and  Caoutchouc. — Frequently  a  mixture  of  i  part  of 
gutta-percha  and  2  parts  of  caoutchouc  is  employed.  Articles  made  of  this  compound 
possess  the  properties  of  both  substances,  and  may  be  vulcanised  equally  as  well  as 
gutta-percha  alone.  A  mixture  of  equal  parts  of  caoutchouc,  gutta-percha,  and  sulphur, 
heated  for  several  hours  to  120°,  obtains  properties  similar  to  those  of  bone  and  horn. 
Sometimes  gypsum,  resin,  and  lead  compounds  are  added  to  this  mixture,  which  is  then 
used  for  making  knife-hafts,  buttons,  &C.J 

Balata. — Since  1857  a  product  has  become  known  which  is  intermediate  in  its 
properties  between  caoutchouc  and  gutta-percha,  and  finds  similar  industrial  applica- 
tions. Balata  is  obtained  from  the  inspissated  milky  juice  of  the  so-called  bully-tree 
(Sapota  Muelleri),  a  sapotaceous  tree  growing  throughout  Guiana.  It  is  chiefly  used 
for  driving-bands,  for  soles  and  heels,  and  in  dentistry. 

Celluloid. — This  name  is  applied  to  a  mixture  of  nitro-cellulose  and  camphor.  It 
has  the  advantage  over  vulcanite  that  it  can  be  obtained  in  various  colours,  but  it  has 
the  defect  of  being  exceedingly  combustible. 

PRESERVATION  OF  WOOD. 

On  the  Durability  of  Wood  in  General. — The  durability  of  wood — i.e.,  its  power  of 
resisting  the  destructive  influences  of  wind  and  weather — varies  greatly,  and  depends 
as  much  upon  the  particular  kind  of  wood  and  the  influences  to  which  it  is  exposed  as 
upon  the  origin  of  the  wood  (timber),  its  age  at  the  time  of  felling,  and  other  condi- 
tions. Beech  wood  and  oak  placed  permanently  under  water  may  last  for  centuries. 
Alder  wood  is  very  lasting  and  substantial  under  water,  as  also  is  fir,  though  in  a  dry 
situation  alder  quickly  perishes.  Taking  into  consideration  the  different  kinds  and 
varying  properties  of  wood  and  the  different  uses  to  which  it  is  applied,  we  have  to 
consider,  as  regards  its  durability,  the  following  particulars : — 

1 .  Whether  it  is  more  liable  to  decay  by  exposure  to  open  air  or  when  placed  in 

damp  situations. 

2.  Whether,  when  left   dry,  it  is  more  or  less  attacked  by  the  ravages  of  insects 

which,  while  in  the  state  of  larvae,  live  and  thrive  in  and  on  wood. 
Pure  woody  fibre  by  itself  is  only  very  slightly  affected  by  the  destructive  influences 
of  wind  and  weather.  When  we  observe  that  wood  decays,  that  decay  arises  from  the 
presence  of  substances  in  the  wood  which  are  foreign  to  the  woody  fibre  but  are  pre- 
sent in  the  juices  of  the  wood  while  growing,  and  consist  chiefly  of  albuminous  matter, 
which,  when  beginning  to  decay,  also  causes  the  destruction  of  the  other  constituents  of 
the  wood.  But  these  changes  occur  in  various  kinds  of  wood  only  after  a  shorter  or 

*  The  last-mentioned  purpose  is  now  by  far  the  most  important.  Like  caoutchouc,  gutta- 
percha  is  a  very  bad  conductor  of  electricity,  and  is  therefore  invaluable  for  insulating  wires  which 
are  conveying  electric  currents,  especially  if  they  have  to  be  laid  under  water.  If  constantly  wet 
it  lasts  a  long  time,  but  if  alternately  wet  and  dry  it  is  inferior  to  caoutchouc. — [EDITOR.] 

f  The  supply  of  gutta-percha  has  been  imperilled  by  incautiously  felling  the  trees.  Without 
diligent  planting  and  strict  preservation,  the  Isonandra  gutta  will  -soon  be  extirpated. — [EDITOR.] 

J  It  was  at  first  expected  that  gutta-percha,  on  account  of  its  lightness,  its  freedom  from  brittle- 
ness,  and  its  resistance  to  acids,  would  be  of  great  use  in  chemical,  dye,  and  print  works,  &c. ,  for 
funnels,  jugs,  measures,  &c.  It  was  soon,  however,  found  that  such  vessels,  though  apparently  not 
attacked  save  by  concentrated  sulphuric  acid,  became  gradually  disintegrated  on  continual  use,  and 
crumbled  away.  This  process  is  much  retarded,  though  not  prevented,  if  the  vessels  are  always 
plunged  into  cold  water  immediately  after  being  used. — [EDITOR."1 


SECT,  viii.]  PRESERVATION   OF  WOOD.  945. 

longer  lapse  of  time.  Indeed,  wood  may  in  some  instances  last  for  several  centuries  and 
remain  thoroughly  sound ;  thus,  the  roof  of  Westminster  Hall  was  built  about  A.D.  1090. 
Since  resinous  woods  resist  the  action  of  damp  and  moisture  for  a  long  time,  they 
generally  last  a  considerable  time  ;  next  in  respect  of  durability  follow  such  kinds  of 
wood  as  are  very  hard  and  compact,  and  contain  at  the  same  time  some  substance 
which — like  tannic  acid — to  some  extent  counteracts  decay.  The  behaviour  of  the 
several  woods  under  water  differs  greatly.  Some  woods  are  after  a  time  converted  into 
a  pulpy  mass.  Others— e.g.,  teak — contain  caoutchouc,  and  are  very  permanent. 

Insects  chiefly  attack  dry  wood  only.  Splint  wood  is  more  liable  to  such  attack  than 
hard  wood ;  while  splint  of  oak  wood  is  rather  readily  attacked  by  insects,  the  hard 
wood  (inner  or  fully  developed  wood)  is  seldom  so  affected.  Elm,  aspen,  and  all 
resinous  woods  are  very  seldom  attacked  by  insects.  Young  wood  which  is  full  of  sap 
and  left  with  the  bark  on  soon  becomes  quite  worm-eaten,  especially  so  the  alder,  birch, 
willow,  and  beech.  The  longer  or  shorter  duration  of  wood  depends  more  or  less  upon 
the  following  circumstances : — 

(a)  The  conditions  of  growth.  Wood  from  cold  climates  is  generally  more  durable  than 
that  grown  in  warm  climes.    A  poor  soil  produces,  as  a  rule,  a  more  durable  and  compact 
wood  than  does  a  soil  rich  in  humus,  and  therefore  containing  also  much  moisture. 

(b)  The  conditions  in  which  the  wood  is  placed  greatly  influence  its  duration.     The 
warmer  and  moister  the  climate  the  more  rapidly  decomposition  sets  in  ;  while  a  dry, 
cold  climate  materially  aids  the  preservation  of  wood. 

(c)  The  time  of  felling  is  of  importance ;  wood  cut  down  in  winter  is  considered  more 
durable  than  that  felled  in  summer,  as  in  the  former  season  it  contains  much  less 
sap.      In  many  countries  the  forest  laws  enjoin  the  felling  of   trees   only  between 
November  15  and  February  15. 

Wood  employed  for  building  purposes  in  the  country,  and  not  exposed  to  either  heat 
or  moisture,  is  only  likely  to  suffer  from  the  ravages  of  insects ;  but  if  it  is  placed  so- 
that  no  draught  of  fresh  air  can  reach  it  to  prevent  accumulation  of  products  of  decom- 
position, decay  soon  sets  in,  and  the  decomposing  albuminous  substances  acting  upon 
the  fibre  cause  it  to  lose  its  tenacity  and  become  a  friable  mass.  Under  the  influence 
of  moisture,  fungi  are  developed  upon  the  surface  of  the  wood.  These  fungi  are 
severally  known  as  the  "  house  fungi "  (Thetephora,  domestica  and  Boletus  destructor) 
and  the  clinging  fungus  (Cerulius  vastator).  They  spread  over  the  wood  in  a  manner 
very  similar  to  the  growth  of  common  fungi  on  soil.  Their  growth  is  greatly  aided  by 
moisture  and  by  exclusion  of  light  and  fresh  air.  A  chemical  means  of  preventing 
such  growths  is  found  in  the  application  to  the  wood  of  iron  acetate,  prepared  from 
wood  vinegar.  Wood  is  often  more  injuriously  affected  when  exposed  to  sea  water, 
when  it  is  attacked  by  a  peculiar  kind  of  mollusc  known  as  the  bore-worm  (Teredo 
navalis}.  This  creature  is  armed  with  a  horned  beak  capable  of  piercing  the  hardest 
wood  to  a  depth  of  36  centimetres.  These  pests  originally  belonged  to,  and  abound 
in  great  numbers  in,  the  seas  under  the  tropical  clime,  but  they  are  also  met  with  on 
the  coasts  of  Holland  and  England. 

Preservation  of  Wood  in  Particular. —  The  means  usually  adopted  to  prevent  the 
destruction  of  wood  by  decay  are  the  following : — 

1.  The  elimination,  as  much  as  possible,  of  the  water  from  the  wood  previously  to 

its  being  employed. 

2.  The  elimination  of  the  constituents  of  the  sap. 

3.  By  keeping  up  a  good  circulation  of  air  near  the  wood  so  as  to  prevent  its  suffo- 

cation, as  it  is  termed. 

4.  By  chemical  alteration  of  the  constituents  of  the  sap. 

5.  By  the  gradual  mineralisation  of  the  wood,  and  thus  the  elimination  of  the  organic 

matter. 

30 


946  CHEMICAL  TECHNOLOGY.  [SECT.  vin. 

1 .  Drying  Wood. — Thoroughly  dried  wood  remains  for  a  long  time  unaltered  while 
in  a  dry  situation,  more  especially  so  when  dried  by  so  strong  a  heat  that  it  becomes 
browned.     When  timber  has  to  be  put  into  a  damp  situation,  it  should,  after  having 
been  well  dried,  be  first  coated  with  a  suitable  substance  to  prevent  the  moisture 
penetrating  into  the  wood.     This  purpose  is  attained  by  coating  the  wood  with  linseed 
oil,  so-called  Stockholm  tar,  coal-tar  creosote,  and  other  hydrocarbons.      Hutin   and 
Boutigny  adopt  the  following  method  to  prevent  the  absorption  of  moisture  by  wood 
that  is  put  hito  the  ground : — The  portion  of  the  post  or  wood  to  be  buried  is  first 
immersed  in  a  vessel  containing  benzol,  petroleum,  photogen,  &c.,  and  when  taken  out 
is  ignited  and  thus  charred.     When  extinguished,  the  wood  is  put  to  a  depth  of  from 
3  to  6  centimetres  into  a  mixture  of  pitch,  tar,  and  asphalte,  and  next  the  entire  piece 
of  wood  is  thoroughly  painted  over  with  tar. 

2.  Elimination  of  the  Constituents  of  the  Sap. — The  constituents  of  the  sap  are 
the  chief  cause  of  the  decomposition  of  wood,  and  they  should  consequently  be  removed ; 
many  plans  are  adopted.     The  constituents,  of  the  sap  can  be  eliminated  from  the  felled 
tree  by  three  methods  : — 

(1)  By  treatment  with  cold  water,  with  which  the  wood  must  be  thoroughly  saturated 
to  dissolve  the  constituents  of  the  sap,  which  are  removed  when  the  wood  is  exposed 
to  a  stream  of  water.     It  is  evident  that  with  large  timber  a  long  time  is  necessary  to 
ensure  perfect  saturation. 

(2)  By  employing  boiling  water  the  sap  is  removed  much  more  quickly  and  efficiently. 
The  pieces  of  wood  are  placed  in  an  iron  vessel  with  water,  and  boiled.     Large  pieces  of 
timber  cannot  be  treated  in  this  manner,  but  are  immersed  in  a  cistern  in  which  the 
fluid  is  heated  by  means  of  steam.     According  to  the  thickness  of  the  wood,  the  boiling 
occupies  some  six  to  twelve  hours. 

(3)  By  treatment  with  steam  (steaming  of  wood) — the  most  effectual  method  of  re- 
moving the  constituents  of  the  sap,  the  hygroscopicity  of  the  wood  thus  treated  being 
rendered  much  less,  while  the  wood  is  far  more  fitted  to  resist  the  effects  of  weather. 
The  apparatus  employed  in  carrying  out  the  method  consists  of  a  boiler  for  the  genera- 
tion of  steam,  and  a  cistern  or  steam  chamber  for  the  reception  of  the  wood,  this 
chamber  being  constructed  of  masonry  and  cement,  of  boiler-plate,  or  being  simply  a 
large  and  very  wide  iron  pipe.     In  most  cases  a  jet  of  steam  is  conveyed  from  the 
boiler  to  the  steam  chamber,  where  it  penetrates   the  wood,  and  dissolves  out  the 
constituents  of  the  sap,  which,  on  being  condensed,  is  allowed  to  run  off.     In  the  case 
of   oak   this   fluid  is  of   a  black-brown  colour ;  with  mahogany,  a  brown-red ;  with 
linden   wood,    a   red-yellow ;  with  cherry-tree  wood,   a  red ;  &c.      The   operation  is 
finished  when  the  outflowing  water  is  no  longer  coloured.     The  steamed  wood  is  dried 
in  the  air  or  in  a  drying- room ;  it  loses  from  5  to  10  per  cent,  in  weight  by  the  process, 
and  becomes  of  a  much  darker  colour.     The  steam  is  sometimes  worked  at  a  temperature 
of  above  100°,  but  generally  the  contents  of  the  steam  chamber  are  maintained  at  from 
60°  to  70°.    Towards  the  end  of  the  operation  some  oil  of  coal-tar  is  introduced  into  the 
boiler,  and  is  consequently  carried  over  with  the  steam,  impregnating  the  wood. 

The  removal  of  the  sap  can  also  be  effected  to  some  extent  by  means  of  mechanical 
pressure  between  a  pair  of  iron  rollers,  which  are  gradually  brought  more  closely 
together.  Another  method  is  by  means  of  air  pressure.  Barlow  employs  for  this 
purpose  a  metal  case  in  which  the  wood  is  enclosed,  and  to  one  end  of  which  an  air 
pump  is  attached.  Air  being  forced  into  the  tube  or  case,  the  sap  flows  away  at  the 
end  opposite  to  which  the  pump  is  attached.  But  both  these  methods  are  costly,  and 
are  not  applicable  in  all  cases. 

3.  Air  Drains. — The  construction  of  air  drains  or  passages  around  woodwork  to  be 
preserved  is,  where  the  method  is  applicable,  a  great  aid  to  the  preservation  of  the 
wood.  The  consideration  of  the  best  means  of  effecting  ventilation  in  this  respect  is 


SECT,  viii.]  PRESERVATION   OF  WOOD.  947 

not  a  matter  with  which  we  can  deal  in  this  work.  It  is  sufficient  to  say  that,  in 
many  instances,  the  air  channels  are  connected  on  the  one  hand  with  the  open  air,  and 
on  the  other  with  the  chimney. 

4.  Chemical  Alteration  oj  the  Constituents  of  the  Sap. — One  of  the  most  usual  and 
most  effective  means  of  preventing  the  decomposition  of  wood  is  by  producing  a  chemical 
change  in  the  constituents  of  the  sap,  so  that  fermentation  can  no  longer  be  set  up. 
To  this  class  belongs  the  well-known  plan  of  protecting  woodwork  that  is  to  be  exposed 
to  the  action  of  the  moisture  of  the  earth  by  charring  the  wood,  either  by  fire  or  by 
treatment  with  concentrated  sulphuric  acid,  so  that  the  wood  is  coated  to  a  certain 
depth  with  a  layer  of  charcoal,  the  charcoal  acting  as  an  antiseptic.  The  charring  or 
carbonisation  of  the  wood  can  be  effected  either  with  the  help  of  a  gas  flame  or  the 
flame  from  a  coal  fire.  The  apparatus  of  De  Lapparent,  invented  for  this  purpose, 
became  very  generally  employed  in  1866  at  the  dockyards  of  Cherbourg,  Pola,  and 
Dantzic.  According  to  another  method,  the  wood  is  impregnated  throughout  its  whole 
mass  with  some  substance  that  either  enters  into  combination  with  the  constituents  of 
the  sap,  or  so  alters  their  properties  as  to  prevent  the  setting  up  of  decomposition. 
To  this  class  belong  the  four  following  methods,  these  being  the  only  ones  that  have 
met  with  any  more  extensive  use. 

(i)  Kyan's  preserving  fluid  is  a  solution  of  mercuric  chloride  of  various  degrees 
of  concentration.  In  England  a  solution  of  i  kilo,  of  corrosive  sublimate  in  80  to  100 
litres  of  water  is  generally  employed  for  railway  sleepers.  The  timber  is  laid  in  a 
water-tight  wooden  trough  containing  the  solution,  where,  according  to  its  size,  it 
remains  a  longer  or  shorter  time.  In  Baden  the  wood  remains  in  the  kyanising 
solution,  when  it  is  to  be  impregnated  to  a  depth  of — 


82  mm. 


85  to  150 
150  to  180 
1 80  to  240 
240  to  300 


for  4  clays, 
7     i, 


10 


18 


the  solution  consisting  of  i  kilo,  of  sublimate  to  200  litres  of  water.  The  prepared 
wood  is  washed  with  water,  rubbed  dry,  and  then  placed  in  sheds  free  from  exposure 
to  rain  and  strong  sunlight.  The  principal  action  of  the  mercuric  chloride  is  to 
convert  the  albumen  of  the  sap  into  an  insoluble  combination,  capable  of  withstanding 
decomposition,  while  the  bichloride  becomes  gradually  reduced  to  mercurous  chloride 
(calomel).  A  great  objection  to  this  method  is  the  danger  to  which  the  carpenter 
or  joiner  who  may  afterwards  shape  the  wood  is  exposed,  the  free  chemicals  acting 
upon  his  system  through  his  hands,  nostrils,  and  mouth.  In  England,  wood  to  be 
varnished  is  seldom  kyanised. 

Erdmann  remarks  upon  this  plan  of  preserving  wood  that  the  interior  of  the  log  is 
still  left  in  its  original  condition.  To  answer  this  objection  the  kyanising  has  been 
made  more  effective  by  placing  the  wood  in  a  water-tight  trough  with  the  solution 
of  sublimate,  and,  by  a  great  pressure  of  air,  thoroughly  impregnating  the  wood. 
Kyanising  by  this  method  becomes,  however,  as  expensive  as  any  other  impregnation 
method.  Recently  there  has  been  substituted  for  the  pure  mercuric  chloride  a  double 
salt  of  the  formula  HgCl..  + 2KC1,  obtained  by  decomposing  a  solution  of  carnallite 
with  mercuric  oxide. 

(2)  Burnett's  (1840)  patent  fluid  consists  of  i  kilo,  of  zinc  chloride  dissolved  in 
go  litres  of  water.  Wood  treated  with  Burnett's  fluid  has  been  buried  in  the  earth  for 
five  years  without  undergoing  any  change,  while  unprepared  wood  buried  for  the  same 
length  of  time  has  been  totally  destroyed.  Zinc  chloride  has  been  much  used  in 
Germany  as  an  impregnating  material.  Besides  this  salt,  copper  sulphate  and  zinc 
acetate— zinc  pyrolignite— (Scheden's  method)  have  been  employed.  The  action  of 


948  CHEMICAL  TECHNOLOGY.  [SECT.  vin. 

the  copper  and  zinc  salts  may  be  explained  by  considering  that  the  metallic  oxides 
of  the  basic  salt  formed  during  seasoning  separate,  and  combine  with  the  colouring 
matter,  tannic  acid,  resin,  &c.,  of  the  wood  to  form  an  insoluble  compound. 

(3)  Bethell's  (1838)  patented  method  consists  in  treatment  under  strong  pressure 
with  a  mixture  of  tar,  oil  of  tar,  and  carbolic  acid,  this  mixture  being  known,  com- 
mercially by  the  name  of  gallotin.     In  and  near  London   wood   thus   treated   has 
remained  eleven  years  in  the  earth  without  undergoing  change ;  other  pieces  of  timber 
so  treated  were  subjected  to  the  action  of  the  sea  for  four  years ;  and  were  still  in  good 
condition.     Yohl  employs  for  preservation  peat  and  brown  coal  creosote;  Leuchs  uses 
paraffine.     Such  agents,  however,  render  wood  treated  with  them  highly  inflammable. 

(4)  Payne's  method. — This  includes  two  patents,  the  first  having  been  taken  out  in 
1841.     Both  are  based  on  the  impregnation  of  the  wood — first  with  one  salt,  and  next 
with  another  salt,  which  is  capable  of  producing  with  the  former  a  precipitate  insoluble 
in  water  and  in  the  sap  of  the  tree.     The  first  solution  is  usually  one  of  iron  sulphate 
or  of  alum  ;  then  follows  a  solution  of  calcium  chloride  or  of  soda.     The  wood  to  be 
impregnated  is  placed  in  a  vessel  from  which  the  air  is  exhausted,  the  first  solution 
being  then  admitted,  and  pressure  subsequently  applied.     The  first  solution   being 
removed,  the  second  is  admitted,  and  pressure  again  applied.     It  is  necessary  to  dry  the 
wood  partially  between  the  two  impregnations.    Payne's  method,  much  used  in  England, 
possesses,  moreover,  the  advantage  of  rendering  the  wood  somewhat  uninflammable. 
The  same  effect  results  with  the  methods  of  Buchner  and  Von  Eichthal,  who  im- 
pregnate the  wood   with  a   solution  of  iron  sulphate,  and  then  with  a  water-glass 
solution,  whereby  the  pores  of  the  wood  are  filled  with  ferrous  silicate.       Ransome 
attains  the  same  end  by  an  impregnation  with  a  water-glass  solution  and  subsequent 
treatment  with  an  acid.     It  is  found  that  the  treatment  of  wood  according  to  the 
above  methods  is  generally  attended  with  good  results.      A  method  of  impregnation 
with  materials  forming  insoluble  soaps,  aluminium,  and  copper  oleates,  or  those  of  other 
metals  patented  in  1862,  has  given  some  moderate  results  on  the  small  scale. 

5.  Mineralising  Wood. — When  the  terms  mineralised,  petrified,  metallised,  or  in- 
crusted  are  applied  to  wood,  they  mean  that  the  wood  has  undergone  impregnation 
with  an  inorganic  substance,  which  has  so  filled  the  pores  of  the  wood  that  it  may 
be  said  to  partake  of  the  characteristics  of  a  mineral  substance.  Suppose  that 
the  wood  has  become  impregnated  with  iron  sulphate  and  then  exposed  to  the 
rain,  the  sulphate  will  be  gradually  dissolved  out,  in  time  leaving  only  a  basic  sulphate. 
By  the  researches  of  Striitzki  (1834),  of  Apelt  in  Jena,  and  of  Kuhlmann  (1859),  the 
influence  of  iron  oxide  upon  wood  fibre  has  been  rendered  very  clear.  Wood  im- 
pregnated with  basic  iron  sulphate  ceases  to  be  wood  after  some  time. 

.Boucherie's  Method  of  Impregnation. — This  method  consists  in  the  impregnation 
of  the  wood  with  the  necessary  substance,  in  a  manner  similar  to  the  natural  filling  of 
the  pores  with  sap ;  that  is  to  say,  the  solution  is  introduced  into  the  tree  from  its 
roots,  and  is  thus  made  to  take  the  place  of  the  sap  in  all  parts  of  the  timber.  When 
the  tree  is  felled,  the  root  end  is  placed  in  a  solution  of  the  salt  (copper  sulphate, 
iron  acetate)  and  allowed  to  remain  for  some  days ;  at  the  end  of  the  required  time 
the  wood  will  have  become  completely  impregnated  with  the  salt.  Occasionally  this 
method  is  employed  in  colouring  woods,  colouring  matter  being  used  instead  of,  or  as 
well  as,  the  salt.  The  linden,  beech,  willow,  elm,  alder,  and  pear  tree  can  be  treated 
in  this  manner.  The  fir,  oak,  ash,  poplar,  and  cherry  tree  do  not,  however,  absorb 
the  impregnating  fluid  sufficiently. 


APPENDIX. 
USEFUL     TABLES. 

THERMOMETRIC    SCALES. 

IN  this  work  temperatures,  almost  without  exception,  are  given  on  the  Centigrade 
scale,  which  takes  the  boiling-point  of  water  at  the  ordinary  atmospheric  pressure  at 
100°,  and  its  freezing-point  at  o°.  Where  any  other  scale  is  used  it  is  specially 
mentioned.  The  following  rules  will  be  useful  for  manufacturers  who  prefer  to  make 
use  of  the  thermometer  of  Fahrenheit,  or  that  of  Reaumur. 

To  convert,  degrees  Centigrade  into  degrees  Fahrenheit  • 

If  the  temperature  is  above  the  freezing-point  of  water  (o°  C.),  multiply  by  9, 
divide  by  5,  and  add  32  to  the  quotient. 

If  the  temperature  be  below  o°  0.,  but  above  -  18°  C.,  multiply  by  9,  divide  by  5, 
and  subtract  the  result  from  32. 

If  below  —  1 8°  C.,  multiply  by  9,  divide  by  5,  and  subtract  32  from  the  result. 

To  convert  degrees  Fahrenheit  into  degrees  Centigrade : 

If  above  32°  F.,  subtract  32,  multiply  by  5,  and  divide  by  9. 

If  below  32°  F.,  but  above  o°  F.,  subtract  the  temperature  from  32,  multiply  by  5, 
and  divide  by  9. 

If  below  o°  F.,  add  the  temperature  to  32,  multiply  by  5,  and  divide  by  9. 

The  conversion  of  Reaumur's  scale — in  which  the  boiling-point  of  water  is  taken  as 
80°,  and  vice  versa — is  effected  in  the  same  manner  ;  the  number  4  being  used  instead 
of  5  as  a  multiplier  or  divisor. 

HYDROMETER   TABLES. 

For  determining  the  specific  gravity  of  liquids  heavier  than  water  the  scale  of 
Twaddell  has  been  generally  used. 

for  its  conversion  into  direct  specific  gravity  : 

Multiply  by  5,  and  add  i  to  the  product. 

For  converting  specific  gravity  into  Twaddell : 

Subtract  i  and  divide  by  5. 

The  degree  Tw.  of  any  liquid  shows  its  weight  per  gallon  in  pounds,  if  we  prefix  i 
and  insert  the  decimal  point  before  the  last  figure.  Thus,  hydrochloric  acid  =  32°  Tw. ; 
its  weight,  therefore,  is  13-2  Ibs.  per  gallon. 

Some  manufacturers,  especially  in  the  Liverpool  district,  use  a  hydrometer  which 
shows  direct  specific  gravity  if  we  place  i  before  its  first  figure.  Thus  a  sample  of 
hydrochloric  acid  of  32°  Tw.  will  be  on  this  scale  160°. 

The  scale  of  Baum6  bears  no  simple  relation  to  direct  specific  gravity;  con- 
sequently its  conversion  into  degrees  Tw.,  and  into  direct  specific  gravity,  can  only  be 
effected  by  means  of  tables,  as  follows : — 


95° 


APPENDIX. 


Degrees 
Baume'. 

Specific 
Gravity. 

Degrees 
Baume". 

Specific 
Gravity. 

Degrees 
Baum6. 

Specific 
Gravity. 

Degrees 
Baume. 

Specific 
Gravity. 

0 

I'OOO 

2O 

I'I52 

40 

i  '357 

60 

1-652 

I 

1-007 

21 

1-160 

41 

1-369 

61 

1-670 

2 

I.OI3 

22 

1-169 

42 

1-382 

62 

1-689 

3 

I'O2O 

23 

1-178 

43 

i  '395 

63 

1-708 

4 

1-027 

24 

1-188 

44 

1-407 

64 

1727 

5 

1-034 

25 

1-197 

45 

1-421 

65 

1747 

6 

I-O4I 

26 

i  -206 

46 

i  '434 

66 

1767 

7 

1*048 

27 

i  -216 

47 

1-448 

67 

1788 

8 

1-056 

28 

1-226 

48 

1-462 

68 

1-809 

9 

1-063 

29 

1-236 

49 

1-476 

69 

1-831 

10 

I-070 

30 

1-246 

50 

1-490 

70 

1-854 

II 

I-078 

31 

1-256 

5i 

I-505 

7i 

•877 

12 

I  -086 

32 

1-267 

52 

1-520 

72 

-900 

13 

1-094 

33 

1-277 

53 

'535 

73 

•924 

14 

I'lOI 

34 

1-288 

54 

•551 

74 

'949 

15 

1-109 

35 

1-299 

55 

•567 

75 

'974 

16 

1-118 

36 

1-310 

56 

•583 

76 

2-OOO 

17 

1-126 

37 

1-322 

57 

•600 

18 

i  '134 

38 

i  '333 

58 

•617 

19 

I'i43 

39 

i  "345 

59 

•634 

For  liquids  lighter  than  water  no  determination  can  be  effected  with  Twaddell's 
hydrometer.  The  scales  used  are  those  of  Beck,  Cartier,  or  Baume's  light  instru- 
ment. 


Deg. 

Beck. 

Cartier. 

Baume". 

Deg. 

Beck. 

Cartier. 

Baume. 

a. 

6. 

a. 

4. 

70 

0-7083 

35 

0*8292 

0-840 

0-845 

0-849 

69 

0-7112 

34 

0-8333 

0-845 

0-850 

0-854 

68 

07142 

33 

0-8374 

0-851 

0-855 

0-859 

67 

07173 

32 

0-8415 

0-856 

n-86  1 

0-864 

66 

0-7203 

31 

0-8457 

0-862 

0-866 

0-869 

65 

0-7234 

30 

0-8500 

0-867 

0-872 

0-875 

64 

0-7265 

29 

0-8542 

0-872 

0-878 

0-88  1 

63 

0-7296 

28 

0-8585 

0-879 

0-883 

0-886 

62 

07328 

27 

0-8629 

0-885 

0-889 

0-892 

61 

07359 

26 

0-8673 

0-891 

0-895 

0-897 

60 

0-7391 

... 

... 

0744 

25 

0-8717 

0-897 

0-901 

0-903 

59 

0-7423 

24 

0-8762 

0-903 

0-907 

0-909 

58 

0-7456 

23 

0-8808 

0-909 

0-914 

0-915 

57 

0-7489 

22 

0-8854 

0-916 

0-921 

0*921 

56 

0-7522 

21 

0*8900 

0*922 

0-927 

0-927 

55 

07556 

.. 

0763 

20 

0-8947 

0-929 

o-934 

o-933 

54 

07589 

19 

0-8994 

0-935 

0-941 

0-939 

53 

0-7623 

18 

0-9042 

0-942 

0-948 

0-946 

52 

0-7658 

17 

0-9090 

0-949 

o-955 

0-952 

Si 

0-7692 

16 

0-9139 

0-956 

0-962 

o-959 

5° 

07727 

... 

... 

0-784 

15 

0-9189 

0-963 

0*969 

0-965 

49 

0-7763 

0-780 

14 

0-9239 

0-970 

o'976 

0-972 

48 

0-7799 

0-792 

13 

0*9289 

0-977 

... 

o-979 

47 

0-7834 

0-795 

12 

0-9340 

0-985 

... 

0-986 

46 

0-7871 

... 

0-799 

II 

0-9392 

0-992 

0-992 

45 

0-7907 

0-803 

IO 

0-9444 

I'OOO 

... 

I'OOO 

44 

0-7944 

0-794 

0-807 

9 

0-9497 

43 

0-7981 

0-799 

... 

0-8II 

8 

0-9550 

42 

0-8618 

0-804 

0-816 

7 

0*9604 

41 

0-8061 

0-809 

0-820 

6 

0-9659 

40 

0-8095 

0-814 

0-824 

5 

0-9714. 

39 

0-8133 

0-819 

O-824 

0-829 

4 

0-9770 

38 

0-8173 

0-825 

0-829 

0-834 

3 

0-9826 

37 

0-8212 

0-830 

0-834 

0-839 

2 

0-9883 

36 

0-8252 

0-835 

0-839 

0-844 

I 

0-9941 

APPENDIX. 

The  following  scale  is  very  often  used  for  alcohol : — 

Gay-Lussac's  Alcoholometer  (Alcoornetre)  at  15°. 


95* 


Degree. 

Sp.  Gr. 

Degree. 

Sp.  Gr. 

Degree. 

Sp.  Gr. 

Degree. 

Sp.  Gr. 

IOO 

0795 

75 

0-879 

50 

0-936 

25 

0-971 

99 

O'Soo 

74 

0-881 

49 

0-938 

24 

0-972 

98 

0-805 

73 

0-884 

48 

0-940 

23 

0-973 

97 

0-810 

72 

0-886 

47 

0-941 

22 

0-974 

96 

0-814 

7i 

0-888 

46 

0'943 

21 

0-975 

95 

0-818 

70 

0-891 

45 

0-945 

20 

0-976 

94 

0-822 

69 

0-893 

44 

0-946 

19 

0-977 

93 

0-826 

68 

0-896 

43 

0-948 

18 

0-978 

92 

0-829 

67 

0-899 

42 

0-949 

17 

0-979 

9i 

0-832 

66 

0-902 

4i 

0-951 

16 

0-980 

90 

0-835 

65 

0-904 

40 

0-953 

15 

0-981 

89 

0-838 

64 

0*906 

39 

0-954 

14 

0-982 

88 

0-842 

63 

0-909 

38 

0-956 

13 

0-983 

87 

0-845 

62 

0-911 

37 

0-957 

12 

0-984 

86 

0-848 

61 

0-913 

36 

0-959 

II 

0-986 

85 

0-851 

60 

0-915 

35 

0-960 

IO 

0-987 

84 

0-854 

59 

0-918 

34 

0-962 

9 

0-988 

83 

0-857 

58 

0-920 

33 

0-963 

8 

0-989 

82 

0-860 

57 

0-922 

32 

0-964 

7 

0-990 

81 

0-863 

56 

0-924 

3i 

0-965 

6 

0-992 

80 

0-865 

55 

0-926 

30 

0-966 

5 

0-993 

79 

0-868 

54 

0-928 

29 

0-967 

4 

0-994 

78 

0-871 

53 

0-930 

28 

0-968 

3 

0-996 

77 

0-874 

52 

0-932 

27 

0-969 

2 

0-997 

76 

0-876 

5i 

0-934 

26 

0-970 

I 

0-999 

The  weights  and  measures  used  in  this  book  are  given  on  the  metric  system.   Their 
value  in  comparison  with  English  weights  and  measures  is  as  follows  : 


1 5 '4384  grains 
1-5438  grain 

0-1543     ,, 

0-0154     „ 

o-ooooi   „ 
I  kilogramme,  generally  abridged  kilo.  =  2*2054 Ibs.  avoirdupois 

=  2-6803  Ibs.  troy 

100  kilos,  or  metric  quintal    =     220-5486^8. 
jooo  kilos,  or  metric  ton        =  2205-486  Ibs. 


i  gramme 

i  decigramme 

i  centigramme  = 

i  milligramme 

i  micro-milligramme   = 


MEASURES   OF  CAPACITY. 

i  cubic  centimetre  (generally  written  c.c.)  =  i5'438395  fluid  grains  (water) 
1000  c.c.  =  i  litre  =  1760773  imperial  pint;  or,  =0-2200967  imperial  gallon 
i  cubic  metre  =  1-308  cubic  yard;  or,  =  35'3I7l  cubia  feet 
i  gallon  of  water  (=  277-274  cubic  inches)  weighs  10  Ibs. 
224  gallons  =  i  ton 

i  cubic  inch  of  water        =     252-45  grains 
„       mercury  =  3425'25      » 


APPENDIX. 


i  metre 

i  millimetre  = 

i  centimetre  = 

i  decimetre  = 

i  inch 

i  foot  = 

I  yard  = 

i  mile  (1760  yards)  = 

1000  metres  = 


MEASURES  OF  LENGTH. 

=  39-37079  inches  =  3*2808992  feet  =   1*093633  yard 

=     0*03937  inch 

=     0-393708  „ 

=     3'937°79  inches 

=     2-539954  centimetres 

=     3-0479449  decimetres 

0-91438348  metre 

1609-3149  metres 

i  kilometre 


INDEX. 


ABEL,  F.  A.,  analyses  of  fire-clay,  631 
Abraum  salts,  284 
Acetic  acid,  491 
Acetometry,  496 
Acid,  acetic,  491 

arsenic,  206,  450 
process,  531 
arsenious,  205 
benzoic,  502 
boric,  427 

formation  and  production  of,  428 
butyric,  499 
carbonic  determinations,  48 

in  beer,  quantity,  757 
chromic,  470 
citric,  502 

colouring  matters,  583,  587 
colours,  584 
crude  carbolic,  511 
formic,  498 
hydrochloric,  313 

treatment  of  bones  with,  896 
lactic,  500 
nitric,  371,  379 

applications,  383 
densities,  382 
oleic,  conversion  into  palmitic  acid  932 

soap,  915 
oxalic,  499 
phthalic,  570 
picric,  564 

purification  of  chamber,  274 
salicylic,  567 
sulphuric,  262,  271,  282 
concentration  of,  275 
green  vitriol  from,  473 
sulphurous  and  sulphuretted  hydrogen,  sul- 
phur from,  248 
liquid,  259 
tartaric,  500 
valerianic,  499 
Acids,  fatty,  boiler  for  distilling,  928 

manufacture  of,  930 
organic,  491 

sulphuric  and  sulphurous,  251 
Adamantine,  434 
Agate  glass,  625 

Ageing  printed  and  dyed  goods,  822 
Air  drains  for  preserving  wood,  946 
gas,  80 
heating,  115 
thermometers,  4 
Alabaster  glass,  624 

Alberts'  examination  of  gun-cotton,  397 
Alcohol,  properties  of,  760 

tables,  487 

Alcoholic  or  vinous  fermentation,  718 
Alcoholometer,  951 


Alcohols  and  ethers,  487 
Alizarine,  573 

blue,  851 

Alkali,  chloride  of,  363 
Alkalimetry,  300 

Allary  and  Pellieux,  obtaining  iodine  from  sea- 
weed, 370 
Alloys,  brass,  167 

of  aluminium,  223 

of  antimony,  205 

of  copper,  1 66 

of  gold,  195 

of  lead,  174 

of  silver,  187 

Almaden  mercury  works,  208 
Almond  soap,  917 
Aloe  hemp,  812 
Alpaca  wool,  80 1 
Alum,  435,  440,  443 

chrome,  473 

earths,  436 

flour,  437 

from  alum  shale  and  alum  earths,  436 

from  alum  stone,  435 

from  azolite,  438 

from  bauxite,  439 

from  blast-furnace  slag,  439 

from  clay,  437 

from  felspar,  439 

shale,  436 

tanning,  886 

works,  green  vitriol  as  a  bye-product,  473 
Aluminate  of  soda,  442 
Aluminium,  221 

acetates  for  calico-printing,  822 

alloys,  223 

bronzes,  223 

hydrate,  443 

properties  of,  223 

salts,  435,  443 

soap,  918 

sulphate,  441 

Amagat's  ebullioscope,  726 
Amalgamation  of  silver,  175 
Amalgam  copper,  168 
American  grape  sugar,  688 

mineral  oils,  907 

America,  North  and  South,  oil  springs,  Si 
Ammonia,  399 

alum,  440 

from  beet  sugar,  407 

from  bones,  406 

from  lant,  405 

inorganic  sources  of,  400 

in  purified  gas,  determination,  78 

organic  sources  of,  401 

soda  process,  339 
Ammoniacal  purifying,  76 


954 


INDEX. 


Ammoniacal  salts,  important,  407 
Ammonium  carbonate  and  nitrate,  409 

sulphate,  409 

Amorphous  or  red  phosphorus,  416 
Analyses  of  crude  iron,  124 

of  fire-clay,  631 

of  purified  gas,  39 

of  soda-lyes,  324 

of  soda  residues,  329 

of  Upper  Silesian  coals,  26 

of  wine  ash,  727 
Analysis  of  beer,  758 

of  bottles,  596 

of  colourless  strass,  622 

of  gas,  complete,  78 

of  glass,  619 

of  Gleiwitz  coke,  125 

of  sparkling  wine,  732 
Ananas  hemp,  812 
Anatomy  of  animal  skin,  873 
Andaquies  wax,  906 
Aniline,  528 

black,  538 

for  cotton,  839 

blue,  535 

green,  537 

oil,  composition  of,  530 

red,  530 

violet,  537 

yellow,  538 
Animal  charcoal,  filtration  of  beet-root  juices 

through,  700 

manufacture,  Berlin  blue  as  a  bye-pro- 
duct, 479 

fats,  904 
Annatto,  523 
Anthon,  M.,  Longchamp,  M.,  and  Kuhlmann,  M., 

preparation  of  potassium  nitrate,  376 
Anthracene,  514 

colours,  571 

derivatives,  590 
Anthracite,  25 
Antichlore,  867 
Antimony,  202 

and  tin  compounds,  448 

cinnabar,  450 

compounds,  449 

extraction  of,  203 

mordants,  825 

oxide,  449 

pentasulphide,  450 

properties  of,  204 

Apel,  W.,  apparatus  for  gas  analysis,  50 
Apparatus  used  in  dyeworks,  826 
Appolt  Bros.,  coke-oven,  28 
Arc  light,  estimating,  105 
Arrowroot,  68 1 
Arsenic,  205, 450 

acid,  206,  450 

process,  531 
Arsenious  acid,  205 
Art-bronze,  167 
Artificial  colours,  584 

Arts  and  manufactures,  organo-chemical,  873 
Asia,  oil-wells  in,  81 
Aspdin,  J.,  Portland  cement,  669 
Asphalte,  939 
Assay  of  antimony  ores,  205 

of  silver,  187 

of  tin  ores,  200 
Atakamite,  150 

Atmospheric  moisture,  decomposition  of,  1 19 
Augustin's  process  for  silver  extraction,  177 
Auramine  printing,  851 


Auramines,  557 

Aurantia,  564 

Aurine,  565 

Australia,  oil-wells,  81 

Austria,  method  of  obtaining  wood-tar,  15 

oil-wells  in,  81 
Aventurine  glass,  598 
Azele,  515 
Azo  colouring  matters,  577 

colours,  525,  588 

direct  production  of,  851 

dyes,  574 

mixed,  German  patent,  578 
Azuline,  565 
Azurite,  150 

BADEN  ANILINE  COMPANY,  cotton  dyeing,  837 
Baking  bread,  783 

water  for,  234 

Balard's  method  for  extracting  sulphur,  245 
Balata,  944 

Balke,  examination  of  barley,  743 
Balling's  saccharometrical  beer  test,  759 
Bannow's  boiling  vessel,  510 
Bar  iron,  127,  131 
Bark  tanning,  874,  88 1 
Barlow,  process  in  printing,  849 
Bartoli,  A.,  and  Papasogli,  G.,  experiments  on 

coal,  19 

Baryta,  purifying  juice  of  beet-root  with,  700 
Basic  colouring  matters,  585 

ferric  chromate,  473 

hearth  smelting,  140 

lead  chloride  as  a  substitute  for  white  lead, 

467 
Baum  and  Schlieper,  process  for  indigo-printing, 

847 

Baume,  M.,  densities  of  nitric  acid,  383 
Bauxite,  alum  from,  439 
Bean  ore,  1 14 

Bedarieux  black  for  wool,  835 
Beech  oil,  906 
Beer,  analysis  of,  758 

brewing,  735 

cellars,  construction  of,  736 

constituents,  757 

quantity  of  carbonic  acid  in,  757 

testing,  758 

wort,  fermentation  of,  753 
Beeswax,  906 
Beet  sugar,  692 

ammonia  from,  407 

treacle,  708 

Belgian  system  for  zinc  distillation,  212 
Bell-metal,  166 
Benrath,  M.,  analysis  of  glass,  619 

analysis  of  plate-glass,  612 
Benzene,  511 
Benzoic  acid,  502 
Benzol  colours,  528 
Berlin  blue,  478 

for  wool,  832 
Bernthsen  violet,  563 
Berries,  various,  used  for  dyeing,  523 
Berthelot's  researches  on  fats,  903 

on  soap,  912 
Bessemer  converter,  copper  ores  worked  in,  156 

steel,  133 

Bethell's  method  of  preserving  wood,  948 
Biebrich  scarlet,  577 
Bismarck  brown,  574 
Bismuth,  201 

ores,  treatment,  202 

properties  of,  202 


INDEX. 


955 


Bismuth,  uses,  202 
Bittering  wine,  728 
Black,  aniline,  538 

antimony  sulphides,  449 

colours,  523 

dye  for  cotton,  839 

dyeing  wool,  834 

silk  dyeing,  835 

topical,  849 

woollen,  578 

Bias  and  Miest,  working  up  zinc  blende,  216 
Blast  furnace  heat,  conditions  of,  117 

furnaces,  114 

Bleach  and  dye  works,  water  for,  231 
Bleaching,  815 

glass,  601 

machine,  continuous,  818 
Blende  furnace  for  roasting,  256 

process  for  working  up,  216 
Blister  copper,  155 
Blue  alizarine,  573,  851 

and  green  mineral,  457 

aniline,  535 

Bremen,  456 

colouring  matters,  519 

Egyptian,  459 

fayence,  845 

green,  481 

indigo,  521 

methylene,  558 

neutral,  564 

new,  558 

oil,  457 

Paris  or  neutral  Berlin,  478 
pencil,  845 
Prussian,  477 
quinoline,  566 
silk  dyeing,  836 
steam,  847 
stone,  454 

vats  for  woollen,  830 
vitriol,  454 
woollen  dyeing,  829 
Blues,  siliceous,  447 
Blum,  E.,  and  Griineberg,  H.,  stairs  column  for 

gas  liquor,  404 
Blumsky  and  Julian,  boiler  for  distilling  fatty 

acids,  928 
Bock,  M.,  brick  furnace,  655 

saponiflcation  of  fats,  932 
Boetius,  gas  firing  of,  42 
Boghead  coal,  25 

Bohemia,  method  of  obtaining  wood  tar,  15 
Bohm's  mashing  apparatus,  763 
Boiler,  roller,  85 

steam,  duty  of,  59 

size  of  grate,  58 
waggon,  84 

Boiling-point,  determination,  3 
Bombay  hemp,  811 
Bone  black,  900 
glass,  624 
glue,  896 
meal,  424 
soap,  917 
Bones,  899 

ammonia  from,  406 

Bontemps,  manufacture  of  flint  glass,  621 
Booth,  furnace  for  melting  alloys,  195 
Borax,  427,  429 

from  boric  acid,  430 
octahedral,  432 
prismatic,  430 
purifying,  431 


Borax,  uses  of,  433 
Bordeaux  reds,  589 
Boric  acid  and  borax,  427 

formation  and  production  of,  428 
Botsch,  Congo  colours,  850 
Bottle  glass,  595,  615 
Bottles,  manufacture,  605 
Boucherie's  method  of  preserving  wood,  948 
Bovey  coal,  19 
Bradford  oil,  82 
Brass,  167 
Bread  and  flour,  781 

impurities  and  adulterations,  785 

making  and  baking,  modes  and  details,  781 

yield  and  composition,  785 
Bremen  blue  or  green,  456 
Breweries,  water  for,  230 
Brewing,  753 
Brick  and  tile  making,  650 

furnaces,  652 

kilns,  656 

Bricks,  green  eruptions,  634 
Brine,  common  salt  from,  306 
Briquettes,  block  coal,  35 
Brockhaus,  M.,  experiment  with  potato   spirit, 

780 
Bromine,  365 

properties  and  applications  of,  368 
Bronze,  art,  167 

cobalt,  147 

colours,  168 

phosphor,  167 
Bronzes,  aluminium,  223 
Brown,  J.,  analysis  of  soda-lyes,  326 

coal,  19,  92 

green  and  black  colours,  523 

phenyl,  565 

Biichner's  researches  on  barks  for  tanning,  875 
Buff-Dunlop,  lixiviation  apparatus,  321 
Bunsen,  electrolytically  prepared  magnesium,  224 

photometer,  95 

Burnett's  preserving  fluid  for  wood,  947 
Burning  clays,  change  of  colour,  634 
Butter,  788 

artificial,  789 
Butyric  acid,  499 

CADMIUM,  217 

alloys,  218 

and  zinc  compounds,  459 

detection  of,  218 

yellow,  461 
Calcium  soap,  918 

sulphite,  261 
Calico-printing,  843 
Canada,  oil-springs,  81 
Canarine,  581 
Candles,  lighting  with,  98 
Cane  sugar,  689 
Caoutchouc,  939 

and  gutta-percha,  mixture  of,  944 
Capacity,  measures  of,  952 
Carbolic  acid,  crude,  511 
Carbonate  of  potassium,  production  of,  286 

of  soda,  346 
Carbon  dioxide,  determination,  78 

disulphide,  249 

properties  of,  250 

gasification  of,  43 

in  iron,  determining,  124 

sulphur  from  sulphurous  acid  and,  249 
Carbonic  acid,  determinations,  48 

in  beer,  quantity,  757 
Carbonisation  steel,  142 


956 


INDEX. 


Carmine  alizarine,  573 

Carnauba  wax,  907 

Carnot,  A.,  researches  on  the  quality  of  coal,  24 

Carrara  porcelain,  645 

Carthamine,  516 

Casali  green,  473 

Cashmere  wool,  80 1 

Casks,  after-fermentation  of  beer  in,  755 

Cassava  starch,  68 1 

Casselmann's  green,  457 

Cassel  yellow,  467 

Cassius's  purple,  452 

Castner,  reduction  of  sodium,  219 

Cast  steel,  142 

Caustic,  lunar,  452 

potash,  299 
Ceollpa  soda,  309 
Celluloid,  944 

Cellulose,  chemical  production,  862 
Cement,  copper,  composition  of,  158 

Portland,  669 

steel,  142 

testing,  673 
Cements,  mixed,  675 
Centrifugal  A  for  sugar,  706 

machine,  721 

Ceramic  manufacture,  628 
Cereals,  vinous  mash  from,  764 
Ceruleine,  579 
Chalkosine,  150 

Champagne  bottles,  manufacture  of,  731 
Chance,  analysis  of  soda  residues,  330 

recovery  of  sulphur,  337 
Chapman,  E.  T.,  and  Wanklyn,  J.  A.,  examination 

of  water,  228 
Charcoal,  manufacture  of  wood,  12 

moulded,  35 

ovens,  14 
Cheese,  790 

Chemical  alteration  in  the  constituents  of  the 
sap  in  preserving  wood,  947 

composition  of  silk,  804 
of  wool,  801 

constituents  of  beet,  693 
of  must,  721 

examination  of  bar  iron,  131 

means,  soda  obtained  by,  310 

nature  of  butter,  789 

principles  of  pyrotechny,  390 

production  of  cellulose,  862 

purification  of  kerosene,  85 

works  of  Leopoldshall,  apparatus  for  distill- 
ing bromine,  366 
ChemicaSy  pure  gold,  195 

pure  silver,  186 
Chestnut  starch,  681 
Chevreul's  researches  on  soap,  911 
China  blue  style,  845 
Chinese  galls,  876 

grass,  use  of,  810 

wax,  906 

Chloral  hydrate,  491 
Chlorates,  347 
Chloride  of  alkali,  363 

of  lime,  347, 358 
liquid,  359 
properties,  and  loss  of  value,  360 

of  mercury,  453 

of  potassium,  preparation  of,  283 

of  sulphur,  251 

of  tin,  449 

of  zinc,  460 
Chlorination,  192 
Chlorine,  347 


Chlorine,  bleach,  815 

properties  and  uses,  358 
Chloroform,  490 
Chlorometric  degrees,  362 
Chlorometry,  361 

Christy,  chemical  production  of  cellulose,  863 
Chromate  of  zinc,  460 
Chromates,  469 
Chrome  alum,  473 

green,  472 

mordants,  824 

red,  471 

yellow,  470 
Chromic  acid,  470 

hydrate,  472 
Chromium  chloride,  473 

compounds,  469 
Cider,  735 
Cinnabar  antimony,  450 

or  vermilion,  453 
Cinnamon  brown,  574 
Citric  acid,  502 

Clarke,  process  for  softening  water,  237 
Glaus,  ammoniacal  purifying,  76 
Clay,  alum  from,  437 

pipes,  649 

ware,  varieties  of,  637 
Clays  and  their  application,  628 

behaviour  of,  in  working,  633 

change  of  colour  in  burning,  634 

plastic,  630 

various  kinds,  630 

Clichy,  apparatus  for  preparing  white  lead,  463 
Coal,  23 

analyses  of,  26 

block,  35 

boghead,  25 

brown  and  Bovey,  19,  92 

coking  of  small,  27 

combustion  value  of,  24 

fields  of  the  world,  24 

formation  and  location,  23 

gas,  desulphurising,  76 
heating  with,  65 

manufacture,  Berlin  blue  as  a  bye-pro- 
duct, 479 

products  of  degasification,  36 

researches  on  the  quality,  24 

tar  colours,  printing,  850 

treatment,  502 
Cobalt,  145 

bronze,  147 

colours,  145 

green,  146 

pure  protoxide  of,  147 

speiss,  146 

ultramarine,  146 

yellow,  147 
Cochineal,  516 
Cocoa-nut  fibre,  812 

oil  soap,  915 
Cocoons,  sorting,  805 
Creruleum,  146 
Cognac,  analysis,  780 

Cohn,  H.,  quantity  of  light  for  reading,  104 
Coke  generator,  41 

Gleiwitz,  analysis  of,  1 25 

object  of  making,  26 

oven  of  Appolt  Bros.,  28 

ovens  at  Pluto  Mine,  32 
closed,  27 

to  gasify,  41 
Coking  in  heaps,  26 

of  small  coal,  27 


INDEX. 


957 


Collodion  cotton,  398 
Colorimeter  for  beer,  759 
Colorimetric  test  for  kerosene,  86 
Colorine,  576 
Coloured  fires,  392 

glasses,  598,  622 

resists,  844 

Colouring  matters,  examination,  582 
fiuoresceine,  547 
insoluble  in  water,  591 
on  the  fibre,  detection  of,  852 
organic,  514,  579 
phenol,  564 

Colour-pans  for  laboratories,  826 
Colours,  anthracene,  571 

artificial,  acid,  &c.,  584 

azo,  direct  production  of,  851 

benzol,  528 

coal-tar,  printing  with,  850 

Congo,  850 

naphthaline,  567 

phenol,  564 

steam,  847 

topical,  849 

weed,  517 
Colza  oil,  906 
Combustion,  35 
Concrete,  675 
Congo  colours,  850 

red,  575 

Congreve's  granulating  machine,  386 
Copper,  150 

alloys,  166 

amalgam,  168 

blister,  155 

cement,  158 

compounds,  454 

matte,  roasting,  152 

ores,  sulphur  from  roasting,  248 

worked  in  Bessemer  converter.  156 

pigments,  455 

production  in  the  dry  way,  151 
in  the  wet  way,  157 

properties  of,  165 

refining,  153,  161 

in  the  United  States,  155 

slate,  150 

smelting,  English  system,  154 

stannate,  458 

sulphate,  454 
Copperas,  473 

and  logwood  blues  for  wool,  833 
Coprolites,  426 
Coralline,  565 
Cordials,  preparation,  936 
Cordwain  leather,  885 

Cork,  use  of,  for  raising  the  grain  of  leather,  883 
Cotton,  bleaching,  817 

detection  in  linen  fabrics,  813 

dyeing,  837 

fabrics,  adulteration,  815 

oil,  906 

species  and  substitutes,  812 
Coupler,  distillation  apparatus,  509 

process  for  magentas,  534 
Cowles  Bros.,  process  for  aluminium,  222 
Crackle  glass,  624 
Cresol,  512 
Crookes,  W.,  freezing  of  glycerine,  934 

gold  extraction  process,  190 

Odling,  W.,  and  Tidy,  C.  M.,  examination 
of  water,  228 

treating  refractory  gold  ores,  &c.,  191 
Cross,  bleaching  jute,  820 


Cross,  Witz,  and  Schmidt,  cotton  dyeing,  837 
Crown  glass,  610 
Crucibles,  manufacture,  659 
Cryolite,  alum  from,  438 

decomposition  of,  438 

glass,  624 

soda,  343 
Crystal  glass,  619 
Cupellation,  187 
Cupola  furnace,  151 
Curd  soap,  913 
Currying  leather,  883 
Cutch,  876 

Cyanide  of  potassium,  477 
Cylinder  glass,  611 

DAMASCUS  steel,  144 

Deacon  and  Hurter,  caustic  soda,  345 

process  for  obtaining  chlorine,  350 
Degasified  wood,  12 
Degasifying,  35,  36 
Dempwolf ,  M.  0. ,  preparation  of  wheat  starch, 

679 

Descotils,  method  of  extracting  platinum,  197 
Desilvering  work-lead  by  electricity,  185 
Desormes,  C.,  lixiviation  apparatus,  319 
Deville,  H.,  and  Wohler,  M.,  observations  on. 

adamantine,  434 
Dextrine,  677,  683 
Diamond-boron,  434 
Didier  and  Hasse,  furnaces,  73 
Dieter,  M.,  working  up  wine-lyes,  501 
Dingler's  green,  472 
Dinitrodibromfluoresceine,  554 
Discharges  used  in  printing,  845 
Distillation  of  spirits,  767 
Distilleries,  water  for,  230 
Disulphide  of  carbon,  249 
properties  of,  250 
Dividivi,  875 

Dobereiner,  production  of  fire,  417 
Domestic  and  municipal  supplies,  water  for,  233 
Dotsch,  process  for  copper,  158 
Dougal,  boiler  furnace  grate,  61 
Drayton's  process  for  silvering  plate  glass,  614 
Droux,  L.,  saponification,  924 
Drummond  light,  104 

Dujardin's  refining  apparatus  for  sulphur,  247 
Dumas,  M. ,  composition  of  crystal  glass,  619 

experiments  on  glass,  592 
"  Dunging"  printed  and  dyed  goods,  823 
Dunlop,  process  for  obtaining  chlorine,  347 
Dupre,  ejection  apparatus,  284 
Diirre,  lixiviation  apparatus,  321 
Dyar  and  Hemming,  soda-ammonia  process,  340 
Dye  and  bleach  works,  water  for,  231 

stuffs,  naphthaline,  567 

works,  apparatus  used,  826 
Dyeing  and  tissue-printing,  821 

cotton,  837 

linen,  839 

silk,  835 

wool  black,  834 
blue,  829 
green,  834 
red,  833 
yellows,  833 

woollens,  829 
Dynamite,  395 

EAKTHENWAKE  manufacture,  628 

production  of,  636 

stoves,  62 
Earth-nut  oil,  906 


95* 


INDEX. 


Ebullioscope,  725 

Edinburgh  and  Leith,  composition  of  crystal 

glass  in,  619 
Egyptian  blue,  459 
Eichhorn  and  Liebig,  furnace  for  roasting 

blende,  256 

Ekman,  chemical  production  of  cellulose,  862 
Electrical  tanning,  889 
Electricity,  desilvering  work-lead  by,  185 

obtaining  and  refining  copper  by,  161 

production  of  zinc  by,  214 
Electric  lighting,  105 

production  of  lead,  172 

thermometers,  5 

Electrolysis,  use  in  tissue-printing,  848 
Electrolytic  extraction  of  antimony,  204 
Electro-plating,  188 
Eliquation,  153 
Emerald  green,  457,  543 
Enamel,  624 
Enargite,  150 
Enfleurage,  938 
English  apparatus  for  tar  distillation,  508 

borax,  432 

fritte  porcelain,  644 

method  of  manufacturing  white  lead,  463 
of  obtaining  zinc,  214 

process  for  the  production  of  lead,  169 

system  of  copper  smelting,  1 54 
Envelopes,  inferior  paper  for,  860 
Eosine,  551 
Erythrosine,  556 
Escherich's  ring  furnace,  655 
Essen,  generator  gas  made  at,  47 
Essential  oils,  935 
Etching  glass,  626 
Ether,  491 

Ethers  and  alcohols,  487 
Ethyl  alcohol,  487 
Etruscan  vases,  649 

Europe,  various  oil  wells  and  springs,  8l 
Explosives,  384 

FAHL  ores,  150 

Fahnehjelm's  "  globe  light,"  103 

Fahrenheit's  thermometer,  2 

Faist,  analysis  of  merino  wool,  801 

Faraday,  M.,  analysis  of  glass,  619 

Farin,  707 

Fats,  903 

animal,  904 
Fat  varnishes,  909 
Fatty  resists,  844 
Faure  and  Kessler,  platinum  lead  concentrator, 

280 
Fayence  blue,  845 

ware,  647 

Feichtinger  and  Winkler,  Portland  cement,  672 
Felspar,  628 

alum  from,  439 
Fermentation,  712,  718 

of  spirits,  766 

Ferric  chromate,  basic,  473 
Ferricyanide  of  potassium,  477 
Ferrocyanide  of  potassium,  474 
Feser,  J.,  researches  on  barks  for  tannin,  875 
Filigree  glass,  625 
Filters,  234 
Fire  bricks,  657 

clays,  631 
Fires,  domestic  and  industrial,  combustion  in,  50 

for  house  heating,  61 

Firework  mixtures  more  commonly  used,  390 
Firing,  steam  boiler,  58 


Fisher,  0.,  bleaching  and  dyeing  machine,  827 
Fish  glue,  898 

oil,  904 

Flach's  proposal  for  extracting  silver,  180 
Flashing-point  of  oils,  determination,  86 
Flavaniline,  526,  538 
Flavaurine,  565 
Flax,  spinning,  809 

use  and  treatment,  808 
Flaxes.  New  Zealand,  811 
Fletcher,  grate  for  boiler  furnace,  60 
Flint  glass,  621 

soap,  917 

Flooring  tiles,  657 
Flour  and  bread,  781 
Flowers  of  madder,  515 
Flue  dust,  lead,  172 
Fluoresceine,  539 

colouring  matters,  547 
Food,  articles  of,  676 
Foods,  value  of  certain,  799 
Formic  acid,  498 
Forster,  B.,  and  Wara,  F.  A.,  "  non-poisonous  " 

match,  423 
Frank,  A.,  distillation  of  bromine,  365 

preparation  of  potassium  chloride,  283 
Franklinite,  114 
French  berries,  523 

method  of  preparing  white  lead,  463 
Fresenius,  K.,  and  Will,    commercial  value    of 

potash,  301 

Friesner,  reagent  for  wood,  865 
Fritsch's  machine  for  parchmentising  paper,  871 
Fuel  and  its  treatment,  I 
Fuels,  behaviour  when  heated,  35 

determination  of  the  value,  6 
Fuller's  earth,  631 
Furnace,  blast,  1 14 

cupola,  151 

for  melting  gold  and  silver  alloys,  195 

puddling,  130 

reverberatory,  126 

smelting,  117,  154,  169 

soda,  rotating,  317 
Furnaces,  brick,  652 

for  mercury  in  America,  208 

for  the  production  of  lighting  gas,  73 

salt  cake,  311 

sulphate,  312 
Fustic,  522 


GALLEINE,  579 

Gallocyanine,  558 

Galloflavine,  580 

Gall's  apparatus  for  distillation,  770 

Galls,  Chinese,  876 

Galvanic  gilding,  197 

Garancine,  515 

Gareis,  J.,  apparatus  for  small  gas  works,  405 

Gas,  air,  80 

analyses  of  purified,  39 

analysis,  50 

burners,  materials  and  construction,  101 

fires,  41 

firing,  66 

for  bricks,  655 

in  metallurgy,  &c.,  71 

of  Boetius,  42 

for  lighting,  production,  72 

formation  in  the  generator,  66 

generator,  41 

lighting,  71,  101 

liquor,  stairs  column  for,  404 


INDEX. 


959 


Gas  manufacture,  boghead  coal  as  fuel  in,  25 

natural,  82 

composition  from  various  sources,  82 

oil,  80 

oven  for  glass,  604 

peat,  79 

purification,  75 

resin,  79 

sulphur,  248 

to  preserve  samples,  56 

wood,  79 

works,  small  apparatus  for,  405 
Oases,  composition  of  the  roasting,  259 

generator,  composition  of,  70 
Gasifying,  35 

Gatty's  process  for  obtaining  chlorine,  348 
Gay-Lussac,  alcoholometer,  951 

assay  of  silver,  187 

denitrificator,  266 

method  of  chlorometry,  361 

tower,  271 
Gelatine,  892 
Generator  gas,  41 
Geneva  black  for  wool,  835 
German  borax,  433 

silver,  168 

starch  sugar,  analysis,  688 

stoves,  62 

Germany,  oil  wells  in,  81 
Gerstenhofer,  roasting  kilns  for  sulphuric  acid, 

254 

Gilding,  196 

Gillard's  "  platinum  gas,"  103. 
Girofle",  564 
Glass,  agate,  625 

alabaster,  624 

analyses,  594,  619 

aventurine,  598 

blowers'  tools,  610,  615 

bone,  624 

cryolite,  624 

defects  in,  608 

denitrification,  598 

etching,  626 

filigree,  625 

flint,  621 

furnace,  603 

hardened,  616 

ice,  624 

iridescent,  625 

lime,  alumina,  596 

making,  raw  materials  used  in,  600 

manufacture,  592 

melting,  607 
furnace,  68 
vessels  for,  602 

muslin,  625 

optical,  620 

painting,  623 

pearls,  625 

phosphatic,  596 

physical  properties,  600 

polishing,  620 

potash,  593 

pressed  and  cast,  616 

refuse,  utilisation  of,  602 

relief,  625 

satin,  623 

soda,  593 

solubility  of,  596 

soluble,  617 

staining,  622 

various  kinds,  609 
Glasses,  coloured,  598,  622 


Glasses,  Venetian  mosaic,  composition,  600 

Glauber's  salt,  manufacture  of,  285 

Glaze,  porcelain,  640 

Glove  leather,  888 

Glover  tower,  267 

Gluckelberger,  precipitation  of  sulphur,  335 

Glue,  drying,  895 

substitutes,  899 

tests  of  quality,  897 

water  for  the  manufacture  of,  231 
Glycerine,  921,  933 

in  sweet  wines,  determination,  727 
Gold,  188 

alloys,  195 

and  silver  printing,  849 

production  in  1884  :  186 

chemically  pure,  195 

deposits,  189 

extraction,  189 

mosaic,  448 

ore,  &c.,  process  for  treating  refractory,  191 

proof,  195 

properties  of,  195 

purple,  452 

ruby  glass,  599 

salts  of,  452 

separation  of,  194 

silver,  and  mercury  compounds,  452 

soap,  919 

Goodyear,  M. ,  caoutchouc,  943 
Goose  greast,  904 

Goppelsroder,  use  of  electrolysis  in  tissue-print- 
ing, 848 

Gossage,  closed  reverberatory,  311 
Grain  soap,  912 
Graining  leather,  883 
Grains  used  for  beer,  735 
Grape-juice  fermentation,  723 

sugar,  684,  722 
Grapes,  pressing,  720 
Grass  bleach,  815 

Chinese,  810 
Grate,  chain,  60 

shape  of,  for  boiler  furnace,  60 
Grates,  oblique,  60 

polygon,  60 
Green,  aniline,  537 

Bremen,  456 

Casali,  473 

Casselmann's,  457 

cobalt,  146 

colours,  523 

converted  into  blue  ultramarine,  446 

Dingler's,  472 

dyeing  wool,  834 

emerald,  457,  543 

eruptions  on  bricks,  634 

Guignet's,  472 

liquid,  543 

malachite,  539 

quinoline,  566 

Scheele's,  457 

silk  dyes,  837 

steam,  847 

ultramarine,  preparation,  445 

vitriol,  473 
Greens,  blues,  481 

Griineberg,  H.,  and  Blum,  E.,  stairs  column  for 
gas  liquor,  404 

ammonia  apparatus,  402 
Gruner,  L.,  technical  value  of  a  coal,  26 
Gschwandler,  J.,  composition   of  certain  beer, 

756 
Guano,  424 


g6o 


INDEX. 


Guignet's  green,  472 
Gum,  boiling  out  of  silk,  806 
Gun-cotton,  395 
metal,  167 
powder,  384 

composition  and  products  of  combus- 
tion, 388 
properties,  387 
Gutta-percha,  942 

and  caoutchouc,  mixture  of,  944 
Gypsum,  660 
uses,  663 

HALSKE  AND  SIEMENS,  measuring  electric  light, 

105 

Hanover,  oil  wells  in,  81 
Hansen,  E.  C.,  yeast,  714 
Harcourt,  M.,  experiments  on  optical  glass, 

620 

Hard  soap,  912 
Hartmann,   M.,  and   Hauer,  M.,  apparatus   for 

determining  the  value  of  vinegar,  496 
Hasenclever  and  Helbig,  kiln,  255 
Hasse  and  Didier,  furnaces,  73 
Hauer,  M.,  and   Hartmann,  M.,  apparatus  for 

determining  the  value  of  vinegar,  496 
Heat,  diffusion  of,  5 
Heating  arrangements,  50 

with  coal  gas,  65 

with  hot  air,  63,  65 

with  open  fires,  61 
Hehner,  O.,  alcohol  tables,  487 
Helbig  and  Hasenclever,  kiln,  255 
Heinatinon,  598 

Hemming  and  Dyar,  soda-ammonia  process,  340 
Hemp,  810 

various  kinds,  81 1 
Henze's  mashing  apparatus,  763 
Hess,  apparatus  for  determining  the  stability  of 

explosives,  397 

Heupel,  gas  firing  for  lignite,  66 
Hides  for  tanning,  treatment,  878 
History  of  lighting  gas,  7 1 
Hoffmann  and  Licht,  brick  furnace,  652 
Hoffmann,  G.,  combination  of  coke-ovens  with 
Siemens'  heat  reservoirs,  30 

P.  W.,  recovery  of  sulphur,  334 
Hollefreund,  M.,  mashing  apparatus,  762 
Holliday,  T.,  &  Sons,  direct  production  of  azo 

colours,  851 
Hops,  736 

adding  to  beer,  750 

substitutes  for,  737 
Hornig's  researches  on  cheese,  792 
Hot-air  heating,  63,  65 

oven,  22 

House  heating,  61 

Hubner's  method  of  preparing  paraffine,  92 
Hummel,  Lepetit,  Lenz,  and  Martin,  detection  of 

colouring  matters  on  the  fibre,  852 
Hungarian  tawing,  888 
Hurter  and  Deacon,  caustic  soda,  345 

process  for  obtaining  chlorine,  350 
Hydraulic  admixtures,  674 

mortar,  668,  671 
Hydrochloric  acid,  313 

treatment  of  bones  with,  896 
Hydrogen,  amalgamation  for  gold,  191 

sulphuretted,  and  sulphurous  acid,  sulphur 

from,  248 
sulphur  from,  249 
Hydrometer  tables,  949 
Hydrometers,  various,  487 
Hygrothermant,  729 


ICE  and  water,  226 

glass,  624 

machines,  evaporation,  242 

manufacture,  242 
Idria  mercury  works,  207 

Ilge,  K.,  continuous  distillation  apparatus,  775. 
Indamines,  525 
India-rubber,  941 
Indigo,  519,  522 

blue,  521 

dyeing  woollen,  830 

printing,  847 
Indophenol,  558 
Induline,  526,  564 

Industries  based  on  alcoholic  fermentation,  719 
Ink,  marking,  452 

printing,  909 
Inks,  writing,  524 

Inorganic  pigments,  conspectus  of,  480 
Iodine,  368 

properties  and  uses,  371 
Iron,  113 

and  steel,  castings,  143 
examination  of,  124 

compounds,  473 

crude,  114,  123 

melting-heat,  119 

determining,  silicon  and  sulphur,  124 
total  carbon  in,  124 

founding,  125 

metallic,  green  vitriol  from,  473 

minium,  474 

mordants,  823 

ore,  spathic,  green  vitriol  from,  474 

oxide,  purifying  gas  with,  76 

putty,  911 

pyrites,  sulphur  from,  247 

refining,  129 

spar,  113 

wrought  or  bar,  127,  131 
Ironstone,  magnetic  and  red,  113 
Isambert,  M.,  reaction  during  the  production  of 

ammonia,  400 
Isinglass,  898 
Italian  kiln,  13 

ores,  extracting  sulphur  from,  245 

JACQUELAIN,  analysis  of  anthracite,  25 

Japan  wax,  907 

Jensen,  E.,  analyses  of  ash  of  Upper  Silesian 
coals,  26 

Jetoline,  538 

Josephsthal  paper  works,  apparatus  for  obtain- 
ing chlorine,  347 

Juices  of  beet-root,  treatment,  695 

Julian  and  Blumsky,  boiler  for  distilling  fatty 
acids,  928 

Julius  and  Schultz,  arrangement  of  most  im- 
portant tar-colours,  525 

Jurisch,  analyses  of  soda-lyes,  325 

Jute,  811 

bleaching,  820 

KAINITE,  286 

Kaolins,  composition  of,  629 

Karmarsch,  assay  of  silver  alloys,  187 

Kefyr,  788  - 

Keith's  process  for  refining  lead  by  electrolysis, 

173 
Keller,  F.  G.,  mechanical  wood-stuff  for  paper, 

860 

Kerosene,  chemical  purification  of,  85 
Kessler  and  Faure,  platinum  lead  concentrator, 

280 


' 


INJ3EX. 


961 


Kiln,  porcelain,  641 
Kilns,  12,  14 

brick,  656 

for  gypsum,  66 1 

various,  for  lime,  665 
Kind,  A.,  saponification,  922 
King's  yellow,  206 
Kino,  877 

Kjeldahl's  process  for  determining  nitrogen,  7 
Klonne  and  Liegel,  furnaces  for  lighting  gas,  73 
Knapp,  F.,  researches  on  soap-making,  913 
Knapp's  leather,  889 
Knox,  furnace  for  mercury,  209 
Koechlin,  C. ,  cotton  mordant,  838 

H.,  cotton  bleaching,  818 
Kolb,  bleaching  linen,  820 

J.,  densities  of  nitric  acid,  382 
Korschelt,  manufacture  of  fatty  acids,  931 
Kosmann,  production  of  zinc,  215 
Kreusler,  analytical  errors  from  the  alkaline  re- 
action of  glass,  598 
Krigar  furnaces,  125 
Kroncke,  process  for  silver,  176 
Kuhlmann,  M.,  Longchamp,  M.,  and  Anthon,  M., 

preparation  of  potassium  nitrate,  376 
Kurtz,  converting  neutral  potassium  tartrate  into 

the  calcium  salt,  500 
Kyan's  preserving  fluid  for  wood,  947 

LAC  dye,  517 
Lacmoid,  557 
Lacquered  leather,  885 

ware,  647 
Lacquers,  910 
Lactic  acid,  500 
Lactose,  787 
Lampblack,  581 
Lamps,  lighting  with,  98 

oil  used  for,  99 

various  forms  of,  99 
Lant,  ammonia  from,  405 
Lapis  styles,  844 
Lather  soaps,  917 
Laurent's  apparatus  for  raising  sulphuric  acid, 

268 

Lauth's  violet,  563 

Le  Chatelier,  setting  of  hydraulic  mortars,  673 
Lead,  169 

alloys,  174 

chambers,  263,  270 

formation  of  sulphuric  acid  in,  271 

chloride,  white  lead  from,  467 

chromate,  470 

compounds,  461 

ore  washings  at  Alternau,  170 

oxide,  461 

peroxide,  462 

production,  174 

by  electricity,  172 

properties  of,  173 

red,  461 

smelting  furnace,  169 

sulphate,  467 

white,  463 
Leather  dressing,  883 

finishing  and  greasing,  884 

glue,  893 

various  kinds,  883 
Leblanc,  process  for  obtaining  soda,  310,  329 

soda  residues,  utilisation  of,  329 
Lebon's  "  thermo  lamp,"  79 
Leeds,  examination  of  soap,  918 
Leicht's  malt  kiln,  741 
Length,  measures  of,  952 


Lenz,  Martin,  Hummel,  and  Lepetit,  detection  of 

colouring  matters  on  the  fibre,  852 
Lepetit,  Lenz,  Martin,  and  Hummel,  detection  of 

colouring  matters  on  the  fibre,  852 
Leroy  and  Durand,  saponification    at    candle 

works,  926 
L6trange,  L.,  production  of  zinc  by  electricity, 

214 

Leuko-base,  production  of,  540,  544 
"  Levuline  "  blue,  850 
Leyser,  0.,  colorimeter  for  beer,  759 
Licht  and  Hoffmann,  brick  furnace,  652 
Liebig,  researches  on  preserving  meat,  795 

and  Eichhorn  furnace  for  roasting  blende, 

256 
M.,  and  Von    Lerrner,  M.,  researches   on 

brewing,  753 

Liegel  and  Klonne,  furnaces  for  lighting  gas,  73 
Light,  intensity  of,  107 
production  of,  94 
units,  96 
Lighting  gas,  71 

checking  the  process  of  manufacture, 

78 

with  candles,  98 
with  lamps,  98 
Lignite,  19 

gas-firing  for,  66 

Lignites,  average  composition,  20 
Lime,  664 

alumina  glass,  596 
burning,  665 
chloride  of,  347,  358 
liquid,  359 

properties,  and  loss  of  value,  360 
Limonite,  114 

Lindt's  researches  on  cheese,  791 
Linen,  810 

bleaching,  820 
dyeing,  839 

fabrics,  detection  of  cotton  in,  813 
printing,  851 
Linseed-oil  varnish,  908 
Liquid  glue,  897 

Liquids  lighter  than  water,  scales  for,  950 
Liquor,  tanning,  882 
Litharge,  461 
Lithophanie,  644 
Litmus,  522 
Lixiviation,  318,  436 
Loam,  632 
Logwood,  522 

and  copperas  blues  for  wool,  833 
Longchamp,  M.,  Anthon,  M.,  and  Kuhlmann,  M., 

preparation  of  potassium  nitrate,  376 
Longden,  J.  N.,  and  Morgan,  W.  P.,  dry  amal- 
gamation process  for  gold,  191 
Low  and  Niigeli,  yeast,  717 
Lubricants,  907 
Lubricator  for  the  cocks  of  apparatus  for  gas 

analysis,  55 

Lucifer  matches,  manufacture  of,  4|»9 
Ludicke,  experiment  on  parchmentiskig  paper, 

872 

Lunar  caustic,  452 
Lunge's  ammonia  apparatus,  401 
Lunge,  Or.,  caustic  soda,  343 

commercial  value  of  potash,  301 

distillation  of  tar,  503 

formation  of  sulphuric  acid  in   the   leac 

chambers,  271 

manufacture  of  saltpetre,  378 
method  of  chlorometry,  362 
removal  of  bleaching  agents,  816 


962 


INDEX. 


Lye,  evaporation  of  the,  436 

soda,  purification  and  concentration  of,  323 
treatment  of  raw,  374 

MABEEEY,  volatilisation  of  aluminium,  222 

Macco's  heater,  117 

MacDougal,  Eawson,  and  Shanks,  process  for 

producing  chlorine,  352 
Machine  for  bleaching  and  dyeing,  828 

paper  manufacture,  869 

sand-blast,  628 
Mactear,  manufacture  of  sodium,  220 

sulphate  furnaces,  312 
Madder,  514 

lake,  514 

printing,  842 
Magenta,  530 

purification,  533 
Magnesium,  224 

soap,  918 

uses  of,  225 

Magnetic  ironstone,  113 
Maize  starch,  68 1 
Malachite,  150 

green,  539 

Maletra,  plate  furnace,  255 
Mallet's  ammonia  apparatus,  401 
Malligand  and  Vidal's  ebullioscope,  725 
Malt  kilns,  739 
Malting,  738 
Maltose,  688 
Manganese,  145,  467 

mordants,  825 

soap,  919 

Manilla  hemp,  812 
Manufacture  of  oil,  84 

of  paper,  853 
Manures,  phosphates,  424 
Margarine,  789 
Marl,  632 

Martin,  E. ,  preparation  of  wheat  starch,  680 
Martin,  Hummel,  Lenz,  and  Lepetit,  detection  of 

colouring  matters  on  the  fibre,  852 
Martius's  yellow,  570 
Massicot,  461 
Matches,  417 

inodorous,  422 

various  kinds  of  early,  418 
Mather  Thompson,  bleaching  process,  819 
Meat,  792 

cooking,  793 

curing,  796 

various  methods  of  preservation,  794 
Mechernich,  treatment  of  lead  ores,  171 
Meissl,  M.,  maltose,  689 
Melis,  707 

Melting  vessels,  602 

Mendheim,  M.,  gas  furnace  for  bricks,  656 
Mercurial  compounds,  453 

fumes,  condensing,  207 
Mercuric  chloride,  453 

oxide,  453 
Mercury,  207 

fulminating,  398 

gold,  and  silver  compounds,  452 

properties  of,  211 

soap,  919 

uses  and  detection,  212 
Merino  wool,  analysis,  80 1 
Metallic  iron,  green  vitriol  from,  473 
Metallurgical  operations,  application   of  water 

gas  in,  49 
Metallurgy,  108 

of  nickel,  148 
Metals,  hardness  of,  1 1 1 


Metals,  pliancy  of,  112 

properties  of,  1 10 
Methylene  blue,  558 
Methylic  alcohol,  486 
Methyl  violet,  537 

Miest  and  Bias,  working  up  zinc  blende,  216 
Milk,  786 

Millifiore  work,  625 
"Milling"  gold,  191 
Milly,  saponification,  924 
Mineral  additions  to  rags  in  paper-making,  86$ 

green  and  blue,  457 

oil,  80 

waters,  artificial,  241 
Mineralising  wood,  948 
Minium,  461 
Mitscherlich,  chemical  production  of  cellulose, 

862 

Mohair,  80 1 
Molasses,  691 
Molloy,  hydrogen  amalgamation  process  for  gold, 

191 

Mond,  L.,  process  for  obtaining  pure  nickel,  149 
for  obtaining  soda  from  vat  waste,  332 
Mordants,  various,  for  dyeing,  822 
Morgan,  W.  P.,  and  Longden,  J.  N.,  dry  amal- 
gamation process  for  gold,  191 
Morin,  M.,  analysis  of  cognac  from  wine,  780 
Morocco  leather,  885 
Mortars,  &c.,  manufacture,  659 

various,  668 
Mosaic  gold,  448 
Mottled  soap,  914 

Miihlhauser,  manufacture  of  malachite  green, 
540 

production  of  leuko-base,  544 
Mulder's  researches  on  picture  restoring,  911 
Miiller,  H.,   examination   of  wood    and    other 

fibrous  vegetable  matter,  863 
Mungo,  803 

Munich  generator  furnace,  68 
Municipal  and  domestic  supplies,  water  for,  233 
Miirile's  apparatus  for  extracting  ethereal  oils, 

938 

Muslin  glass,  625 

Must,  chemical  constituents  of,  721 
Myrtle  wax,  907 

NAGELI  AND  Low,  yeast,  717 
Naphthaline,  513 

distillation,  569 

dye-stuffs,  567 
Neapolitan  yellow,  450 
Nenuphar  black  for  wool,  835 
Nessler's  researches  on  barks  for  tanning,  875 
Nettle,  the  great,  use  of,  811 
Neubauer,  C.,  analyses  of  grapes,  722 
Nickel,  147 

mordants,  824 

obtaining  pure,  149 

ores  from  New  Caledonia,  149 

properties  of,  149 

wet  process  for,  148 
Nitrate  of  ammonia,  409 

of  potash,  preparation  of,  376 

of  silver,  452 

of  soda,  372 
Nitrates,  371 
Nitric  acid,  371 

applications  of,  383 
densities,  382 
Nitro-benzol,  258 
Nitro  colouring  matters,  588 
Nitro-compounds,  525 
Nitrogen,  determination,  7,  427 


INDEX. 


963 


Nitroglycerine,  393 

Nitrose,  denitration  of,  266 

Nitrosodimethylaniline,  558 

Nitrous  vapours,  arrangements  for  collecting, 

265 
Nobel,  M.,  dynamite,  395 

nitroglycerine,  393 
"  Non-poisonous"  match,  423 
Nut  galls,  876 

oil,  906 

Nuts,  valonia,  876 
Nutrition,  797 

OAK  bark  for  tanning,  874 

Octahedral  borax,  432 

Odling,  W.,  Crookes,  W.,  and  Tidy,  C.  M.,  ex- 

amination  of  water,  228 
Oil  blue,  457 

from  Bradford,  82 

gas,  80 

mineral,  80 

of  vitriol,  solid,  263 

tawing,  890 

wells  and  springs,  81 
Oils,  crude,  rectification  of,  91 

drying,  906 

essential,  and  resins,  935 

ethereal,  extracting,  938 

various,  904 

manufacture,  84 
Oleic  acid,  conversion  into  palmitic  acid,  932 

soap,  915 

Oleomargarine,  789 
Olive  oil,  905 

soap,  914 

Opl,  C. ,  recovery  of  sulphur,  337 
Optical  glass,  620 
Orange  alizarine,  573 
Ore,  bean,  114 

processes  of  reduction,  118 

tile,  150 
Ores,  assay  of  tin,  200 

copper,  150 

gold,  &c.,  process  for  treating  refractory, 
191 

treatment,  108 
Organic  acids,  491 

colouring  matters,  514,  579 
Organo-chemical  arts  and  manufactures,  873 
Orpiment,  206 
Oven-coking,  27 
Ovens,  stoneware,  645 

variou,  21 
Oxalic  acid,  499 
Oxidation  of  silver,  188 
Oxide  of  antimony,  449 

of  iron,  purifying  with,  76 

of  lead,  461 

of  mercury,  453 

"  PADDING  on  mordants,"  843 
Painting  or  staining  glass,  623 

porcelain,  643 
Palm  oil,  904 

soap,  917 

wax,  907 

Pans,  vacuum,  for  beet-juice,  703 
Papasogli,  G.,  and  Bartoli,  A.,  experiments  on 

coal,  19 
Paper,  different  kinds  of,  869 

hand-made,  865,  867 

hanging  varnish,  909 

history  and  materials  used,  853 

mills,  water  for,  23 1 

sheets,  straining,  867 


Paper,  various  substances  used  in  making,  853 

Papier-mache,  870 

"  Para  "  caoutchouc,  941 

Paraffine,  applications,  93 

discovery  and  use,  87 

manufacture,  87 

purified,  93 

refining  crude,  91 

yield  of,  from  various  raw  materials,  92 

and  solar  oil  industry,  87 
Parchment,  891 

paper,  871 

Parian  porcelain,  645 
Paring  leather,  883 
Paris  blue,  478 

violet,  537 

Parkes,  process  for  extracting  silver,  1 80 
Pasley,  Portland  cement,  669 
Pasteboard  making,  870 
Pasteur,  M.,  fermentation,  713 

formation  of  vinegar  from  alcohol,  494 
Pasteuring,  728 
Patio,  process  for  silver,  175 
Pattinson,  process  for  extracting  silver,  179 
Payen's  experiments  with  gypsum,  66 1 

researches  on  cheese,  791 

saponification,  925 

Payne's  method  of  preserving  wood,  948 
Pearls,  glass,  625 
Peat,  18 

gas,  79 

sampling,  7 

Pechiney,  production  of  chlorine,  352 
Peligot's  method  for  obtaining  chlorine,  352 
Pellieux  and  Allary,  obtaining  iodine  from  sea- 
weed, 370 

Pelouze,  experiments  on  glass,  595,  597 
Penot's  test  f or  chlorometry,  361 
Percussion-caps,  398 
Perfumery,  936 
Permanganate  of  potash,  468 
Peroncell's  apparatus  for  the  manufacture  of  di- 

sulphide  of  carbon,  250 
Peroxide  of  lead,  462 
Persian  berries,  523 
Petit,  apparatus  for  saponification,  922 
Petroleum,  origin  of,  81 
Phenol,  512 

colouring  matters,  564 
Phenosaffranine,  564 
Phenyl  brown,  565 
Phloxine,  556 
Phosphates,  manures,  424 
Phosphatic  glass,  596 
Phosphor  bronze,  167 
Phosphorus,  410 

in  iron,  determining,  124 

manufacture,  411 

match,  417 

purification,  413 
Photogene,  94 
Photometers,  various,  96 
Photometry,  95 
Phthaleines,  587 
Phthalic  acid,  570 
Physical  properties  of  glass,  600 
Picric  acid,  564 
Pictet's  ice  machine,  243 
Picture  restoring,  910 
Pikaba  hemp,  812 
Pink  salt,  449 

Pistorius's  apparatus  for  distillation,  768 
Pitch,  value  of,  507 
Plants,  salts  of  potassium  from  the  ashes  of,  287 

soda  from,  310 


964 


INDEX. 


Plate  furnace  of  Maletra,  255 

glass,  609,  612 
Platinum,  197 

black,  vinegar  by  means  of,  495 

extraction  from  its  ores,  197 

lead  concentrator,  280 

light  unit,  97 

properties,  198 

soap,  919 

stills,  278 

Platinising  plate  glass,  614 
Plattner,  extraction  of  gold,  192 
Pluto  Mine,  arrangement  of  coke-ovens,  32 
Pneumatic  malting,  740 
Poling,  159 

Polishing  leather  with  pumice-stone,  883 
Polygon  grate,  60 
Porcelain  glaze,  640 

hard,  manufacture  of,  638 

kiln,  641 

ornamenting,  643 

tender,  manufacture,  644 
Portland  cement,  669 
Potash,  caustic,  299 

commercial  value,  300 

glass,  593 

Potassa  and  cobalt,  nitrate  of  protoxide  of,  147 
Potassium  and  sodium,  218 

carbonate,  production  of,  286 

chlorate,  363 

chloride,  preparation  of,  283 

chromates,  470 

cyanide,  477 

ferricyanide,  477 

ferrocyanide,  474 

nitrate  from  Chili  saltpetre,  376 

perchlorate,  364 

permanganate,  468 

preparation  of,  220 

price  of,  221 

saltpetre,  373 

salts,  283 

from  sea-weeds,  295 
from  suint  of  wool,  297 
from  the  ashes  of  plants,  287 
from  the  treacle  of  beet-root  sugar,  291 
Potatoes,  starch  from,  678 
Potato  spirit,  experiment,  780 
Potter's  clay,  631 

wheel,  639 

Pottery,  common,  650 
Poudrette,  424 
Price's  Candle  Company,  manufacture  of  fatty 

acids,  930 
Printing  ink,  909 

linen,  185 

silk,  852 

tissue,  821,  839 

with  coal-tar  colours,  850 

with  gold  and  silver,  849 

with  resists,  844 
Protoxide  of  cobalt,  pure,  147 
Prussian  blue,  477 

preparing,  478 
Prussiate,  yellow,  476 
Puddled  steel,  133 
Puddling,  129 

furnace,  130 
Pulp-bleaching  866 

bluing  and  sizing,  867 
Pumice  soap,  917 
Purple,  452 

Tyrian,  517 
Purpurine,  573 
Puzzolane  cements,  674 


Pyrites  distillation,  green  vitriol  from  the  resi- 
dues, 473 
Pyrogene,  94 
Pyrotechnics,  390 

QuBRCiTKON,  523 
Quinoline,  565 

EABUTEAU,  M.,  analysis  of  potato  fusel,  780 
Rags,  mineral,  additions  to,  865 

recovery  of  indigo  from,  832 

substitutes  for,  in  paper-making,  853 

treatment  of,  865 
Ramie  hemp,  811 
Rawson,    Shanks,  and   MacDougal,  process  for 

producing  chlorine,  352 
Realgar,  206 
Red  aniline,  530 
Red  dyes,  less  important,  518 

colours,  514 

copper  ore,  1 50 

dyeing  wool,  833 

ironstone,  113 

lead,  461 

or  bark  tanning,  874 

phosphorus,  416 

quinoline,  566 

silk  dyeing,  836 

woods,  518 
Reds,  Bordeaux,  589 

steam,  847 

whites,  yellows,  480 
Regulus,  crude,  156 
Resin  gas,  79 

tallow  soap,  915 
Resins,  938 

Resists,  various,  for  printing  844 
Resorcine,  546 

blue,  557 

Retorts  for  charring  wood,  15 
Retted  flax,  809 
Rhea  grass,  811 
Rice  glass,  624 

starch,  68 1 

Richters,  E.,  analyses  of  soda,  residues,  329 
Richter's  hydrometer,  487 
Rinmann's  or  cobalt  green,  146 
Rock  salt,  304 

mode  of  working,  305 
Roller  boiler,  85 
Rolling  leather,  884 
Roofing-tiles,  657 

Rope-making  waste,  use  in  paper  making,  860 
Rosaniline,  535 

derivatives,  sulphonised,  587 
Rose  soap,  917 
Royal  blue  for  wool,  832 
Run  steel,  143 
Rusma,  206 
Russia  leather,  884 

oil  springs,  81 

process  for  obtaining  wood  tar,  1 5 

use  of  platinum  in,  198 
Russian  stoves,  62 

SACCHAKIFIC^TION,  762 

Saccharimetry,  693 

Saccharometrical  beer  test,  759 

Safflower,  516 

Saffranines,  525,  564 

Sagger,  641 

Sago,  683 

Sal  ammoniac,  407 

Salicylic  acid,  567 

Salines,  common  salt  in,  303 


INDEX. 


965 


Salt  cake  furnaces,  311 

common,  from  brine,  306 
from  sea  water,  302 
in  salines,  303 
properties  of,  307 
uses,  309 
lixiviation,  177 
pink,  449 
rock,  304 

springs,  mode  of  working,  306 
works  and  common  salt,  302 
Saltpetre  earth,  treatment  of  ripe,  374 
mode  of  obtaining,  373 
native,  373 
refining  crude,  375 
soda,  371 
testing,  378 
uses,  379 

Salts  of  aluminium,  435,  443 
of  gold,  452 
of  potassium,  283 

from  sea-weeds,  295 
from  suint  of  wool,  297 
from  the  ashes  of  plants,  287 
from  the  treacle  of  beet-root  sugar,  291 
Sand  blast  machine,  628 

filters,  235 

Saponification  theory,  911 
various  methods  of,  924 
with  caustic  lime,  921 
Sarg,  freezing,  of  glycerine,  934 
Satin  glass,  623 
Sauerwein's  method   for  the  decomposition  of 

cryolite,  438 

Saxony  blue  for  wool,  832 
Scales,  thermometric,  949 
Scarlet,  biebrich,  577 

double  brilliant,  578 
Schaffner,  process  for  obtaining  soda  from  vat 

waste,  330,  337 

"  Schafhautel's  mixture,"  use  of,  131 
Scheele's  green,  457 
Scheibler,  M.,  elution,  708 
Scheurer-Kestner,  combustion  value  of  coal,  24 
Schilling,  N.  H.,  Munich  generator  furnace,  68 
Schmidt,  Cross,  and  Witz,  cotton  dyeing,  837 

tissue-printing,  848 

Schwackhofer,  combustion  value  of  coal,  24 
Schoop's    apparatus  for   the    manufacture    of 

arsenic  acid,  450 
Schott's  experiments  on  the  composition  of  glass, 

594 

Schreib,  H.,  soda-ammonia  process,  342 
Schlieper  and  Baum,  process  for  indigo  printing, 

847 

Schultz  and  Julius,  arrangement  of  most  im- 
portant tar  colours,  526 

tube  drying  oven  of ,  21 
Schulze,  F.,  extraction  of  cellulose,  865 

M.,  maltose,  688 
Schwarten  kiln,  13 

Schwarz's  apparatus  for  distillation,  771 
Schweinfurt  green,  457 
Scraping  or  smoothing  leather,  883 
Sealing-wax,  938 

Sea-water,  common  salt  from,  302 
Sea-weeds,  iodine  from,  369 

potassium  salts  from,  295 
Seger,  M.,  experiments  on  clays,  635 
Senff,  determination  of  different  kinds  of  wood 

on  distillation,  17 
Sericiculture,  803 
Sesame  oil,  906 
Shagreen,  891 
Shanks'  lixiviation  apparatus,  321 


Shanks,  MacDougal,  and  Rawson,   process  for 

producing  chlorine,  352 
Shaving-soap,  917 
Sheer  steel,  142 
Sheet  glass,  61 1 
Shoddy,  803 

Shot,  manufacture  of  small,  173 
Sicilian  raw  sulphur,  composition,  245 
Siemens  and  Halske,   measuring  electric  light, 

105 
working  up  zinc  blende,  216 

apparatus  for  distillation,  772,  777 

C.  W.,  electric  pyrometer,  5 

formation  of  gas  in  the  generator,  66 

F.,  gas  burner,  101 
generator,  42 

gas  oven  for  glass,  604 

glass-melting  furnace,  68 

heat  reservoirs  combined  with  coke  ovens,  30 
Siemens-Martin  process  for  steel,  138 
Silica,  ultramarine,  446 
Siliceous  blues,  447 
Silicon  in  iron,  determining,  124 
Silk,  803 

bleaching,  820 

dyeing,  835 

from  wool  and  vegetable  fibres,  distinguish- 
ing, 807 

manipulation  of,  805 

printing,  852 
Silkworm,  varieties,  803 
Silver,  174 

alloys,  187 

amalgamation  of,  175 

and  gold,  printing,  849 

production  in  1884  :  186 

assay,  187 

chemically  pure,  186 

extraction,  174 

by  solution  and  precipitation,  176 
in  the  dry  way,  178 

fine,  burning,  185 

German,  168 

gold,  and  mercury  compounds,  452 

nitrate,  452 

oxidation  of,  188 

purification,  185 

soap,  919 
Silvering,  187 

plate  glass,  614 
Singeing,  use  of,  for  detecting  cotton  in  linen, 

814 

Sizes,  898 

Slag,  alum  from  blast  furnace,  439 
Slags,  109,  122,  138 

melting,  heat  of,  119 
Slavonian  kiln,  13 
Skin,  animal,  anatomy  of,  873 
Smalts,  146 
Smelting,  108,  117,  140,  154 

copper,  154 

treatment  of  nickel  before,  147 
Smoke  consumption,  61 

formation,  50 

gases,  57 
Soap,  911 

ash,  919 
Soap,  examination,  918 

extracts  and  powders,  919 

pastes,  919 

transparent,  918 

uses  and  tests,  918 

varieties  of,  913,  917 
Soaps,  adulteration,  919 

insoluble,  918 


INDEX. 


Soda,  309 

alum,  440 

ammonia  process,  339 

caustic,  343 

crude,  conversion  into  purified,  318 
conversion  of  sulphate  into,  315 

cryolite,  343 

crystals  producing,  326 

from  plants,  310 

from  sodium  sulphide,  343 

from  vat  waste,  330 

furnace,  rotating,  317 

glass,  593 

lye,  purification  and  concentration  of,  323 

lyes,  analyses  of,  324 

obtained  by  chemical  means,  310 

residues,  analyses  of,  329 
utilisation  of,  329 

saltpetre,  371 

stannates,  449 

theory  of  the  formation  of,  328 

ultramarine,  446 
Sodium  aluminates,  442 

amalgam  for  gold  extraction,  190 

and  potassium,  218 

benzoate,  502 

bicarbonate,  346 

chromate,  470 

manufacture  of,  218 

nitrate,  372 

salt,  555 

sulphate,  314 

thiosulphate,  261 
Soft  soap,  912,  916 
Solar  oil,  94 
Sole  leather,  883 
Solvay,  E.,  soda-ammonia  process,  340 

production  of  chlorine,  352 
Soot,  581 

"  Souring  "  of  kerosene,  85 
Souring  wine,  728 
Soxhlet,  M.,  maltose,  689 
Specific  heats  of  metals,  1 1 1 
Speiss,  145 
Spirit,  eosine,  552 

purification  of  crude,  779 
Spirits,  from  sugar  waste,  766 

from  wine  and  lees,  766 

manufacture  of,  760 

varnish,  909 

Spring  and  well  water,  227 
Springs  of  mineral  oil,  81 
Stamp  machine,  866 
Stannate  of  soda,  449 
Stannic  chloride,  449 
Starch,  676 

sugar,  composition,  687 

works,  water  for,  230 
Stas's  experiments  on  glass,  598 
Steam  boiler,  duty  of,  59 
firing,  58 

boilers,  water  for,  229 

brewing,  757 

colours,  847 

heating,  65 

oven,  21 

Steam  pipe  cement,  911 
Stearine,  921 

Stedman's  retort  furnace  for  lighting  gas,  73 
Steel,  132 

and  iron  castings,  143 
examination  of,  124 

basic  process,  136 

Bessemer,  133 

carbonisation,  142 


Steel,  cast,  142 

cement,  142 

Damascus,  144 

engravings,  144 

properties  of,  143 

puddled,  133 

rough  or  natural,  133 

run,  143 

sheer,  142 
Steeling,  143 

Stenhouse,  Dr.,  composition  of  boghead  coal,  25 
Stereochromy,  618 
Stills,  platinum,  278 
Stockb  ridge,  M.,  beet  sugar,  694 
Stoltze's  method  of  preparing  wood  vinegar,  498 
Stones,  imitation  of  precious,  621 
Stoneware,  manufacture,  645 
Stove  heating  for  houses,  61 

Russian,  62 

tile,  63 
Stoves,  earthenware,  62 

in  Germany,  62 
Strass,  621 

Strontia  process  for  beet  treacle,  711 
Style,  china  blue,  845 

lapis,  844 

madder,  842 
Styrogallol,  580 
Sugar,  684 

candy, 707 

consumption,  706 

extraction  from  beet-root,  694 

of  the  grape,  722 

salts  of  potassium  from  treacle  of  beet-Toot, 
291 

varieties  of,  691 

works,  water  for,  231 
Sugars,  various,  712 

washing,  919 
Suint,  802 
Sulphate,  conversion  into  crude  soda,  315 

furnaces,  312 

of  ammonia,  409 

of  copper,  454 

of  lead,  467 

of  zinc,  460 

sodium,  314 
Sulphide  of  soda,  soda  from,  343 

of  zinc,  process  for  benzol  colours,  562 
Sulphides,  tellurides,  gold  ores,  &c.,  process  for 

treating  refractory,  191 
Sulphite  of  calcium,  261 
Sulphur,  244 

chloride,  251 

determination  of,  78 

extraction,  245 

from  iron  pyrites,  247 

from  roasting  copper  ores,  248 

from  sulphuretted  hydrogen,  249 

from  sulphurous  acid  and  carbon,  249 

from  sulphurous  acid  and  sulphuretted  hy- 
drogen, 248 

from  vat  waste,  248 

gas,  248 

in  iron,  determining,  124 
Sulphur,  properties  of,  249 

recovery  of,  "334,  337 

refining,  245 

Sulphuric  acid,  262,  271,  282 
concentration,  275 
green  vitriol  from,  473 
Sulphurous  acid,  liquid,  259 

and  sulphuric  acids,  251 
Sulzbach,  coke-ovens  used  at,  28 
Sulzer's  yarn-dyeing  machine,  829 


INDEX. 


967 


Sumac,  875 
Sun  gold,  570 

hemp,  Sir 

Superphosphate,  425 
Sutton,  F.,  examination  of  water,  228 
Swedish  fining  for  iron,  129 

"  thermo-kettles,"  16 
Sykes's  hydrometer,  487 

TABAKils,  M.,  ebullioscope,  725 
Tables,  useful,  949 
Tanneries,  water  for,  231 
Tanning,  873,  88 1 

alum,  886 

by  electricity,  889 

in  bark,  88 1 

in  liquor,  882 

materials,  estimation  of  the  value  of,  877 

wares,  composition  of  several,  878 
Tannin,  502 

ink,  524 

mordants,  825 
Tar  colours,  524 

arrangement  of ,  526 

condensation  of  vapours,  88 

distillation,  90,  503 

firing,  73 

mode  of  operating  with,  89 

of  paraffine,  preparation,  87 

properties  of,  89 

retort  from  brown  coal,  93 

treatment  of  the  products  of  distillation,  90 
Tartaric  acid,  500 
Tartrazine,  580 
Tawer's  softening  iron,  smoothing  leather  with, 

884 

Tawing,  886,  890 

Temperatures,  high  determination  of,  4 
Textiles,  examination  of  dyed  and  printed,  852 
Thermo-chemistry,  481 
"Thermo-kettles,"  16 
"  Thermo-lamp,"  79 
Thermometers,  various,  2,  5 
Thermometric  scales,  949 
Thermometry,  2 

Thickenings,  importance  in  tissue-printing,  840 
Thomas  and  Gilchrist, basic  process  for  steel,  136 
Thompson,  J.,  bleaching  cotton,  818  :> 

Thomson's  method  for  the  decomposition   of 

cryolite,  438 

Tidy,  C.  M.,  Odling,  W.,  and  Crookes,  W.,  exami- 
nation of  water,  228 
Tile  and  brick-making,  650 
Tile  ore,  150 

stove,  63 

Tilghman,  saponification,  929 
Tin,  199 

and  antimony  compounds,  448 

chloride,  449 

crystals,  448 

mordants,  825 

ores,  assay  of,  200 

properties  of,  200 

uses  of,  200 
Tinning,  201 

Tissue-printing,  821,  839 
Toilet  soaps,  917 
Toluidine,  530 
Topical  colours,  849 
Tours  black  for  wool,  835 
Tow,  809 
Treacle  of  beet-root  sugar,  salts  of  potassium 

from,  291 

Tube  drying  oven,  21 
Turkey  berries,  523 


Turkey  red  for  cotton,  838 

oil  mordant,  822 
Turmeric,  523 
Turnbull's  blue,  479 
Turner's  yellow,  467 
Turpentine-oil  varnish,  910 
Tyrian  purple,  517 

UCUHUBA  wax,  907 

Uhden,  M.,  coloured  fires,  392 

Ultramarine,  444 

adulterations,  448 

cobalt,  146 

constitution,  447 
linger,  B.,  soap-making,  916 
Upper  leather,  883 

VALEBIANIC  acid,  499 

Valonia  nuts,  876 

Vanadium  black  for  wool,  835 

Varnishes,  908 

Varnish  polishing,  910 

Vats,  blue,  for  woollens,  830 

Vat  waste,  soda  from,  330 

Vegetable  fibres,  808 

Velin,  891 

Venetian  mosaic  glasses,  599 

Verdigris,  458 

Vermilion  or  cinnabar,  453 

Victoria  cement,  674 

green,  543 

yellow,  565 
Vicuna  wool,  80 1 

Vidal  and  Malligand's  ebullioscope,  725 
Vienna  black  for  wool,  835 
Vine  cultivation,  720 
Vinegar  essence,  497 

methods  of  making,  &c.,  491 
Vinous  fermentation,  713,  718 

mash,  764 
Vintage,  720 
Violet,  aniline,  537 

solid,  558 
Violets,  563 

Violle,  determination  of  melting-points,  4 
Vitriol,  blue,  454 

green,  473 

solid  oil  of,  263 

white,  460 

Vogel's  method  for  producing  chlorine,  352 
Volatilisation  of  aluminium,  222 
Volhard,  precipitating  silver,  187 
Von  Lermer,  M.,  and  Liebig,  M.,  researches  on 

brewing,  753 

Von  Welsbach,  A.,  gas  burner,  103 
"  Vulcanol,"  94 

WAGGON  boiler,  84 

Wagner,  A.,  method  of  chlorometry,  361 

researches  on  barks  for  tannin,  875 

testing  saltpetre,  378 

Wanklyn,  J.  A.,  and  Chapman,  E.  T.,  examina- 
tion of  water,  228 
Wara,  F.,  and  Forster,  B.,  a  "non-poisonous" 

match,  423 
Wash-leather,  890 
Washing  powders,  919 

sugars,  919 

Water,  and  high  pressure,  use  of,  for  saponifi- 
cation, 929 

and  ice,  226 

colouring  matters  insoluble  in,  591 

colours  soluble  and  insoluble  in,  584 

composition  of,  226 

coolers,  649 


INDEX. 


Water,  distillation,  239 

examination  of,  228 

for  bleach  and  dye  works,  231 

for  breweries,  230 

for  distilleries,  230 

for  municipal  and  domestic  supplies,  233 

for  paper  mills,  231 

for  starch  works,  230 

for  steam  boilers,  229 

for  sugar  works,  231 

for  tanneries,  231 

for  the  manufacture  of  glue,  231 

gas,  45,  48 

manufacture,  46 

glass,  617 

heating,  65 

mains,  240 

purification,  229 

scales  for  liquids  lighter  than,  950 

softening,  237 

used  for  baking,  234 

well  and  spring,  227 
Waters,  artificial  mineral,  241 
Wax  matches,  423 
Waxes,  906 

Weber,  K.,  analyses  of  glass,  594 
Weber  and  Wiebe,  experiments  on  glass,  598 
Weed  colours,  517 
Weld  and  wold,  523 
Welding,  113,  132 

Weldon,  W.,  process  for  obtaining  chlorine,  348 
Weldon  and  Pechiney,  production  of  chlorine, 

353 

Well  and  spring  water,  227 
Wheat  starch,  preparation,  679 
Whey,  787 
White  lead,  462 

from  chloride  of  lead,  467 

oil  soap,  914 

resists,  844 

vitriol,  460 

Whites,  reds,  yellows,  480 
Whitwell's  air  heater,  117 
Wiesner,  J.,  sags,  683 
Will,  H.,  and  Fresenius,  R.,  commercial  value  of 

potash,  301 

Wilson's  bleaching  liquor,  363 
Window  glass,  609 
Windsor  soap,  917 
Wine,  casking,  723 

clearing  or  fining,  730 

constituents,  724 

diseases  of,  727 

lyes,  working  up,  501 

making,  719 

musts,  improving,  732 
Wines,  and  lees,  spirits  from,  766 

artificial,  732 

effervescing,  730 

Winkler  and  Feichtinger,  Portland  cement,  672 
Witz,  calico  printing,  843 

Cross,  and  Schmidt,  cotton  dyeing,  837 
Woehler,  freezing  of  glycerine,  934 

process    for    determining  total  carbon    in 
iron,  124 

M.,  and  Deville,  H.,  observations  on  adaman- 
tine, 434 
Wollner,  M.,  manufacture  of  saltpetre,  377 


Wolff,  J.,  commercial  starch,  680 
Wood,  ii 

charcoal,  manufacture,  12 

composition  of  air-dried,  12 

examination  of,  863 

gas,  79 

preservation  of,  944 

products  of  degasification,  36 

stuff  for  paper-making,  860 

tar,  15 

vinegar,  497 
Wood's  metal,  218 
Woods,  red,  518 
Wool,  artificial,  802 

bleaching,  820 

chemical  composition,  801 

distinguishing  silk  from,  807 

origin  and  properties  of,  800 

suint  of,  salts  of  potassium  from,  297 

varieties,  80 1 
Woollen  black,  578 

printing,  851 
Woollens,  dyeing,  829 
Wootz,  133 
Work-lead,  172 

desilvering,  by  electricity,  185 
Wort,  cooling,  751 

extractives  of,  748 

production  of,  744 
Wrought  iron,  127,  131 

XYLOL,  511 

YEAST,  713,  718 

substitutes  for,  in  baking,  784 
Yellow,  aniline,  538,  574 

cadmium,  461 

Cassel  and  Turner's,  467 

cobalt,  147 

colouring  matters,  522 

Martius's,  570 

Neapolitan,  450 

prussiate,  476 

quinoline,  566 

salicyl,  567 

silk,  dyeing,  837 

Victoria,  565 
Yellows,  dyeing  wool,  833 

whites,  reds,  480 
Young  fustic,  522 

ZEISS  of  Jena's  optical  glass,  621 
Ziervogel's  process  for  extracting  silver,  178 
Zinc,  212 

and  cadmium  compounds,  459 

blende,  working  up,  216 

chloride,  460 

chromate,  460 

distillation,  212 

English  method  of  obtaining,  214 

production  by  electricity,  214 

properties  of,  216 

soap,  919 

sulphate,  460 

sulphide  process  for  benzol  colours,  562 

uses  of,  217 

white,  459 
Zulzer's  machine  for  making  wax  matches,  424 


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